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Elekta Neuromag® Service Manual

Contents

1. I II EE Sensor adapter Electonics cable Preamp MEG Gaeta Wes Se rege aa 4 sensor R 770 RT mothar l Preamplifier Sensor chip FBO elements in 1 I I I i assembly FBS l 1 sensor i 2 sensor l 16 i 4 sensor i element j RT i elements Sensor elements VG o 11 leads i 2x11 pairs elem I 1 1 S 1 1 1 I T cae 1 SN a i i I li IG XE teri ni D 3 SS gt e i Magne DC His ne x UB 18S T l tometer SQUID 1 v t Tani Fy LENS TiVo i n I li i i xcs je Tie Sie I 1 Fone ju Tx Te R4 4 R3 2 c l TiN TIN TN i 1 i li i I i i i I lu i n i i i i i i if 1 i I I I li 1 i I l b T V 1 I i i i I I 1 ji i 1 I i i i f i 1 i i _ 1 1 1 I 4 1 1 i a l ee T2F Te i g Ji 72B 2B TB grad Ex i a Xn 2v av FCE 2G za Tad BOGS RB 4 I R i T2N 12N EN i i i 1 i I i i I I l 1 1 li i i i l i i 1 i lu i i 1 1 I l I I li 1 I i li I I n i 1 i l i I i 1 I b l b I i 1 i i
2. E l Filter unit I l 230V V 4A l 230V l oe lt 1 Vp l als Gp 6V 1 2A I f 6V 1 6 A l atVca lt vca Gc l v l 15V 0 8A i a c l l x Ve Gc l Main electronics power supply unit 9 pcs 11 pcs MEG electronics l front end power Mains switch 15V9A 4Va l fi a apt ot ae a Ad Na l aj 200V 120V 230V Main switch off TOVBA ad 7 x 115V the cabinet P J 230V ee aa 100V i PH leq RY 4 Ga L po 4 ren Il l I AJAY l l EM Ga EEG electronics i 1 Gd front end power l 230 V 24 V p xat 100 VA devi l Vi l E Ay H ci l i 2 cS Preamplifier front end power supply Medical iso at l 1 24 V 24 V i Wee I Front end EEG power supply I isolated Vd v l Yevm MEG opto l ae m L yp 3 8H cxi Om Gd MEG electronics Vd front end control l si MEG opto I J Jo e by 4 rem aT cie a el z 20v 5V Cm sa S44 lt 1
3. Channel selector rotary switch Connector 2 B V E o o 0 Prot 9 10 kQj OO 1 i 4 O x Heater a Neuromag NM20413K a Figure 7 1 Insert wiring tester Figure 7 2 Ribbon test cable 2 pcs 2008 11 11 System Performance Verification 7 Connector 2 Connector 1 Figure 7 3 Test adapter 7 5 2 Channel numbering and conductor naming scheme Each channel is identified by a 4 digit XXYZ code where e XX is the preamplifier number 1 26 e Y is the sensor element number 1 4 connected to preamplifier XX Zis for the magnetometer and 2 or 3 for the gradiometer channels In the wiring tester the channels are marked Y Z and the preamplifier XX is selected by inserting the test adapter into the corresponding preampli fier slot See Figure 7 4 Insert top plate with preamplifier numbers indi cated Note Preamplifier slot 8 contains only sensor elements 1 and 2 Other preamplifier slots are identical with all the sensor elements 1 4 con nected Note Preamplifiers are numbered from 1 26 This is not to be con fused with the board address 0 25 used by the janitor program The corresponding board address is obtained by subtracting one from the preamplifier number Each sensor element has 22 conductors from room temperature to
4. System verification 4 2 PM tools and material 4 2 1 44 Special tools and material needed in PM a Full PM Nitrogen gas purity 99 95 pressure regulator adjustable to 0 1 2 bar output pressure needed cylinder volume is a minimum of 10 liters Liquid helium required by the cool down for Day 3 Liquid helium for the first refill after 2 3 days after the full PM cool down Vacuum pump system Vacuum valve adapter KF25 vacuum flange to the 7 mm silicone hose adapter this is included in the latest version of the Cryogenic Accessories Kit check that this is available on site Fixed siphon end flange to the 7 mm silicone hose adapter this is included in the latest version of the Cryogenic Accessories Kit check that this is available on site 5 meters of clean silicone hose with the inside diameter of 7 mm Insert wiring tester connection cables Multimeter fluke or equal with pin probes connectors and banana plug 4 mm cables 2008 11 11 Preventive Maintenance n Silicone vacuum grease CDs to save final set ups and measured data Useful emergency spares recommended to be on site during the full PM Preamplifier board Siphon vacuum valve o rings Filters to siphons Rupture foil of safety exhaust Interim PM Vacuum pump siphons CDs to save final set ups and measured data Useful emergency spares recommended to be on site during the interim PM Preamplifier board Siphon va
5. Check that the fans are operating Check that the fuses are OK and replace them if necessary Check that the indicator lights are OK Clean the filters and replace them if necessary Vacuum clean the electronics cabinet Tighten the screws and fasten the cables Check the connectors and the door mechanisms Stimulus electronics cabinet Check that the indicator lights are OK Vacuum clean the stimulus electronics cabinet Tighten the screws and fasten the cables Check the connectors and the door mechanisms Check for inappropriate connections of equipment and correct if neces sary Computer system Check and note the software versions and upgrade them if necessary Check and clean the keyboard 2008 11 11 Preventive Maintenance n 3 4 Check and clean the mouse Remove dust and fingerprints from the monitor screens Check the fans of the workstation Vacuum clean the inner parts of the printer Check the air filter and the fan of the printer Clean the printer according to its manual Check the cabling for inappropriately terminated LAN connectors or SCSI cables and correct if necessary 10 Perform an overall visual inspection of the computer system hardware e l 2 HPI system and 3D digitizer Check the HPI coils and cables Check the epoxy coating of the coils Replace worn coils Check the cables of the 3D digitizer Check the functi
6. O l b N Ze O N Lifting unit l GEE 1 QE Portable step up transformer if needed L mains live N mains neutral PE protective earth ground L1 and L2 isolated power terminals symmetiric with respect to ground Switches S6 and S7 are inside cabinets max 10A Secondary fuses F5 F8 and switches S4 S5 are optional Figure A 9 Recommended power and grounding arrangements The specifications of the transformers switches and fuses are site specific 2008 11 11 119 n Technical diagrams 120 2008 11 11 APPENDIX B Fine calibrations of the He level meter The fine calibration of the helium level He level meter needs to be done after the helium level meter board spare part has been changed or when the helium level meter s local display is not showing the correct helium level The purpose of the calibration is to set the parameters of the helium level meter to show the right level values of the helium inside the dewar Note The helium level inside the dewar needs to be less than 0 before starting the calibration Special tool needed Helium level gauge calibration adapter hereafter calibration adapter for the helium level meter part no EL20377T Preparations The helium level inside the dewar needs to be below 0 in the seated position before the calibration according to this instruction can be started The gantry must be moved into the seated position for the calib
7. Preparations a Vacuum has reached the good level 5 10 mbar or higher in dewar Normally vacuum pumping takes overnight 12 15 hours to be ready Vacuum pumping can be in progress until the cool down starts b Prepare a transfer siphon and other accessories for helium refill c The extension has been screwed on end of the fixed siphon d Multimeter is connected into the Liquid helium level gauge unit e All power is turned off from the system f All electrical stim cables are pulled into the simulus cabinet g Filter cabinet hatches and electronic cabinet doors are closed h Close the possible additional feed throughs 2 Close the dewar vacuum valve and stop the vacuum pump 2008 11 11 Preventive Maintenance n 3 4 5 9 10 11 12 13 Start filling in helium as in the normal refill The pressure starts to oscillate inside the dewar pressure gauge Remove the vacuum pump and accessories from the room The multimeter reading starts to decrease slowly from 230 Ohms When the multimeter reading reaches 150 Ohms a Remove the multimeter from the room b Close the MSR door Note The time period immediately after this is critical as the sensors are soon going to a superconducting state Continue the helium transfer until the sound in the exhaust line goes silent then pressure in dewar gauge drops close to 0 bar the point when the system starts to collect He as liquid continue trans
8. The head position indicator HPI system is based on coils placed on known locations on the head see Figure 2 19 A single coil can be ener gized by acoil driver card with currents of different frequencies The exci tation signal is provided by the data acquisition system A three dimensional Fastrak digitizer manufacturer Polhemus Inc USA is con nected to the computer system see Figure 2 20 It is used in the prepara tion phase before MEG measurement to digitize the positions of the head position indicator coils as well as the landmarks on the head which are visible in the MRI scan 2008 11 11 31 Hardware and Networking MU a ae gg Figure 2 20 3D digitizer unit 3D digitizing requires the following devices see Figure 2 20 Goggles with a separate reference receiver goggles to receiver 2 Digitizing stylus pen pen to receiver 1 Transmitter coil 3D digitizer unit pep le 1 2 3 3 Voice intercom system The voice intercom system has been designed not to cause any interfer ence to the Elekta Neuromage However to avoid disturbances the micro phone should be kept further than 30 cm away from the helmet 32 2008 11 11 Hardware and Networking Figure 2 21 Intercom system The voice intercom system is composed of a table station 1 and a main station with a power supply 2 see Figure 2 21 The microphone 3 of the main station is inside the magnetically shielded room The micro phone
9. telnet kaptahl janitor pass homunculus122 e Heater settings Master heater control on set master heater control heat switch 127 Heaters on set heater heat on off 1 set heater2 heat on off 1 set heater3 heat on off 1 set heater4 heat on off 1 set heater5 heat on off 1 set heater6 heat on off 1 set heater7 heat on off 1 set heater8 heat on off 1 set heater9 heat on off 1 set heater10 heat on off 1 set heater11 heat on off 1 set heater12 heat on off 1 set heater13 heat on off 1 set heater14 heat on off 1 set heater15 heat on off 1 2008 11 11 49 g Preventive Maintenance set heater16 heat on off 1 set heater17 heat on off 1 set heater1 heat on off 1 set heater19 heat on off 1 set heater20 heat on off 1 set heater21 heat on off 1 set heater22 heat on off 1 set heater23 heat on off 1 set heater24 heat on off 1 set heater25 heat on off 1 set heater26 heat on off 1 Heaters off set heater heat on off 0 set heater2 heat on off 0 set heater3 heat on off 0 set heater4 heat on off 0 set heater5 heat on off 0 set heater6 heat on off 0 set heater7 heat on off 0 set heater8 heat on off 0 set heater9 heat on off 0 set heater10 heat on off 0 set heater11 heat on off 0 set heater12 heat on off 0 set heater13 heat on off 0 set heater14 heat on off 0 set heater15 heat on off 0 set heaterl6 heat on off 0 set heater17 heat on off 0 set heater1 heat on off 0 set heater19 heat on off 0 set heater20 heat on off 0
10. 3 Check that there is no physical damage to the dewar or helmet units Overheating electronics fans filters The power source in the electronics cabinets will automatically shutdown if overheated at approximately 40 degrees C The recommended temper ature for the electronics cabinet is 20 24 degrees C If the electronics cabinet has overheated make sure that all the fans are operational and that airflow to the filters is not obstructed in any way 6 3 Software and networking toubleshooting 1 Check that all network cables are connected properly 2 Check the network connections by pinging the IP addresses of the workstations as well as their hostnames which can be checked from etc hosts 6 3 1 Premature end of acquisition The acquisition stops automatically when e Workstation cannot handle all the data quickly enough Data transfer problem is detected in the front end of the system Workstation hard disk is about to fill up It is usually possible to continue just by pressing GO after saving the data If the acquisition crashes or hangs up do the following 1 Double click on the RestartAcqProcesses icon found in the Mainte nance folder and follow the instructions on the screen 2 Restart Acquisition 3 Ifthe janitor powerup file is not up to date reload the SQUID tuning settings either using Squiddler or Autotuner 2008 11 11 75 g Troubleshooting 76 6 3 2 Acquisition does not start C
11. 6 Removable back plate screws under cover strips for accessing the dewar top part and the MEG preamplifiers from back the cabling and the lifting mechanism secondary pulleys 7 Removable back hatch for accessing the EEG preamplifiers the lifting mechanism main pulley and the shaft 8 Removable docking piece for the bed The 306 sensors measure the magnetic field distribution around the head and convert it to 306 electrical signals The sensors are immersed in liquid helium to keep their temperature stable at 4 2 K At this temperature the sensors are superconducting The 306 channel cryogenic insert contains 306 SQUID sensors positioned in a helmet shaped array and the neces sary support structures and cabling The sensor insert is inside the cryo genic dewar The helmet shaped cryogenic dewar is a vacuum insulated vessel contain ing the liquid helium necessary for cooling the SQUID sensors to 4 2 K It has a double wall structure with a vacuum gap and an additional thermal radiation shielding in between The neck plug of the probe unit also pro vides thermal insulation The supporting gantry is standing on the floor of the magnetically shielded room and it has a lifiting mechanism to move the dewar between two measurement positions supine position for patients lying on a dedi cated measurement bed and seated position for patients sitting on a special measurement chair The dewar is mounted on a cradle moving along guide rails dr
12. 65 Ohms Rp 300 Ohms at room temperature Rp 0 250 Ohms at 4 K Ru 100 Ohms at room temperature and about Ru 0 5 Ohms at 4K 1 Put the test adapter into the Aux slot number 27 2 Set the channel selector rotary switch to position 1 1 3 Connect the multimeter ohms terminal to B and the common terminal to F The correct reading is 130 30 Ohms if the system is in the superconducting state and 430 30 Ohms if the system is at room temperature 4 Connect the multimeter ohms terminal to V and the common terminal to G The correct reading is 130 30 Ohms if the system is in the superconducting state and 430 30 Ohms if the system is at room temperature 2008 11 11 System Performance Verification ES 5 Connect the multimeter ohms terminal to X and the common terminal to N The correct reading is 130 30 Ohms if the system is in the superconducting state and 430 30 Ohms if the system is at room temperature 6 Connect the multimeter ohms terminal to B and the common terminal to V The correct reading is 130 30 Ohms 7 Connect the multimeter ohms terminal to X and the common terminal to V The correct reading is 130 30 Ohms 8 Connect the multimeter ohms terminal to F and the common terminal to G The correct reading is 130 30 Ohms 9 Connect the multimeter ohms terminal to N and the common terminal to G The correct reading is 130 30 Ohms 10 Set the channel selector rotary switch to position
13. K 0 L EEG kK y i ial ia AY n A D H Digital Ethernet il signal RT im AY D A H Proc System bus im it Q o ial i Digital H Ethernet Ys Electrode K Ay HA D H signal za Ke f B Opto i pian System bus Fiber opt e Head position solation C z link indicator coils i L El p 1 P i 1 T Hu Digital 1 Ethernet i A Li RT Quality RY n D AH signal assurance ene eei anus H proc System bus phantom FL Eg cU Liquid Stimulators lt gt gt i i Helium i i un level i Stim al FA Digital Ethernet VMEbus trigger H signal probe i l VF Ke Oa Boe Real time Gees poe 1 System bus computers LHe 1 level Fiber i QU display optlink 00 0 0 0 T Workstations 3D digi tizer Opto Z isol i K Acq sp LAN Anal Figure A 1 Schematic diagram of the electronics 2008 11 11 111 A Technical diagrams ee _ Control 4 Feedthrough Hiper optical level display Bus filter n Stimulus E Liquid Bus triggers in out System riot Helium probe Piber optic controller Analysis link Bus workstation mear poston LHe HPI Feedthrougn HPI Eet coils
14. The wiring unit see Figure 2 3 and Figure 2 5 consists of a helmet shaped support for the elastically mounted sensor sockets wiring from sensor sockets to sensor adaptor boards sensor adapter boards and a pro tective shell also acting as a spring The protective shell has a sealing ring see Figure 2 4 to prevent eventual solidified oxygen from entering near the sensors The support rod locks the wiring unit firmly on its place to prevent mechanical vibrations of the sensor array A liquid helium level probe is also mounted on the wiring unit see Figure 2 5 Figure 2 3 Wiring unit The photograph above has been taken during installation without the pro tective shell The assembly of cable bundles and ties is only partial The wiring unit consists of the following parts 1 Helmet shaped support 2 Sensor socket assembly mounted flexibly on the helmet shaped sup port 2008 11 11 Hardware and Networking EX 3 Wiring from sensor sockets to sensor adapter boards tied to helmet shaped shell and bundled together in normal use 4 Sensor adapter boards 5 Field effect transistors FETs for amplifier noise cancellation nor mally not visible as they are below the wiring unit top plate 6 Passive filtering components 7 Connectors to the neck cable assembly 8 Support rods used only during installation and removed after installa tion Figure 2 4 Sensor insert There are the following parts in the sensor inse
15. lt gauge MEG control board Control m Serial Ry Dc power bus i PS ME board gt l Ipoles in Gantry es MUX T Phantom Ga Gd HPI ren 1 coils Aud istim Pate ttl ar Patient Stimulation stereo l l HE cud Assistant stereo Inter com i l 9 Intercom microphone eee l d Intercom loudspeaker Electronics cabinet Magnetically shielded room Figure A 5 Schematic diagram of auxiliary electronics 2008 11 11 115 n Technical diagrams A 1 4 Lifting mechanism DC MD MED ED Er pocek mee ZEE T l l V l sv fos an x l BN Fiber pair Y Out ne j neg 22 K Gnd l S Upper limit ev or Itc bs Tension no reflection cy INZ yellow light on ea ee zi V SxX1 i S1 T Fiber pair upper limit Fibre 2 p Out T supine 8 Gnd l O l Tension Sx2 l s2 Y reflection Sx2 tension 1 sv A light on e Tl Limit l I M yellow l l ca Fiber pair Y Out l Control a Eur S q Gnd logic 5 n l L ATE t Fibre 1 Latch on SX3 S3 Upright A l reflection latch prig PY light on SX3 Ve 0 I
16. moment of the fitted dipoles with the calculated dipole moment and adjust if necessary b Noise test 1 Record at least 1 minute of raw data for noise analysis See MEG noise measurements on page 83 2 Perform the noise analysis See MEG noise data analysis on page 83 58 2008 11 11 CHAPTER 5 Maintenance Checklists 5 1 System check Table 5 1 Checklist for performing a system check Action Measure Limit OK NOK Save the current set up in the N A Squiddler program as a reference Check that the acquisition is gener N A ally working and the tuning is OK Record 2 minutes of empty room lt 5 fT SqrtHz data either seated or supine Col lect new data for 120 seconds sampling rate 1000 Hz filter 300 Hz Measure white noise levels in the 10 75 Hz range Print out the graph Check the helium boil off rate and N A review the helium statistics col lected Check that no extra items have N A been glued or fixed to the surface of the dewar and remove them if necessary 5 2 Magnetically shielded room Table 5 2 Checklist for the MSR Grounding 2008 05 09 H Maintenance Checklists Table 5 2 Checklist for the MSR Action Measure OK NOK Check that the system is grounded by disconnecting the main ground strap measuring the resistance between the room wall and the main ground strap Room installation Check that the door mechanism N A
17. 107 Appendix A Technical diagrams 111 A 1 Electronics diagrams sese 111 System diagrams a s ance anata rete o ese Lec Rb aCe c es 111 EEG electrones 4 25 dod ob E ESI utut epit Eae es 113 Auxiliary electronics 222 colos et RM 115 Lifting mechaniS M ssns 822 uet le tfe eei d sehe teg so 116 A 2 Electronics cabinet 5 4s eae ele ended a 117 A 3 Power supplies iuc rd RR rrr re x XE Vows 118 Schemalic dlagram us nie uh RE RU D ee E 118 Recommended power and grounding arrangement 119 Appendix B Fine calibrations of the He level meter 121 CHAPTER 1 Introduction 1 1 Purpose of this manual This service manual is intended to provide instructions for the maintenance and troubleshooting of the Elektra Neuromag MEG device Note Service of the device should only be carried out by certi fied service engineers 1 2 Safety instructions safe service of the system and maintaining reliable operation Read the f Warning This section contains important information concerning the instructions entirely before servicing the system 1 2 1 Properties of helium The dewar is a vacuum insulated vessel containing liquid helium at a cryogenic temperature Since the cold liquid is potentially dangerous cer tain precautions must be made to assure completely safe operation of the device Helium liquid or gas is nonflammable and nontoxic Helium is one of the noble gases He Ne Ar Kr Ra Hel
18. 2 1 11 Connect the multimeter ohms terminal to B and the common terminal to E The correct reading is 130 30 Ohms if the system is in the superconducting state and 230 30 Ohms if the system is at room temperature 12 Connect the multimeter ohms terminal to V and the common terminal to G The correct reading is 130 30 Ohms if the system is in the superconducting state and 230 30 Ohms if the system is at room temperature 13 Connect the multimeter ohms terminal to B and the common terminal to V The correct reading is 130 30 Ohms 14 Connect the multimeter ohms terminal to F and the common terminal to G The correct reading is 130 30 Ohms 15 Set the channel selector rotary switch to position 2 2 16 Repeat Steps 8 11 2008 11 11 109 Ed System Performance Verification 110 2008 11 11 APPENDIX A Technical diagrams A 1 Electronics diagrams Magnetically shiel A 1 1 System diagrams ded room MEG Preamp RF feedthrough Main electronics cabinet 2 fiber optic links MEG EEG e e Ri it MEG y 4 e
19. 63 H Maintenance Checklists 5 5 Gantry and chair Table 5 5 Checklist for the gantry and chair Action Measure Limit OK NOK Gantry mechanism Perform an overall check of the N A mechanical parts of the gantry Drive the gantry up and down a N A few times and make sure the indi cator LEDs operate normally Check the ropes for wear and 5 Years replace if necessary Chair mehanisms Perform overall check of the N A mechanical parts of the chair Check that the chair moves up and N A down without problems Turn the chair over on its left side N A and inspect the hydraulics for leaks Top up the water reservoir if N A needed Check the chair wheels for free N A running Check that the chair remains at a 15 minutes fixed height supporting a person Cleaning Check that no extra items have N A been glued or fixed to the surface of the gantry or the chair Dust the gantry and chair surfaces N A 5 6 Electronics cabinets Table 5 6 Checklist for the electronics cabinets Main electronics cabinet 64 2008 05 09 Maintenance Checklists H Table 5 6 Checklist for the electronics cabinets Action Measure Limit OK NOK Check that all fans are operating N A Verify that all fuses are OK N A Verify that indicator lights are OK N A Clean filters Replace if necessary N A Vacuum clean main electronics N A cabi
20. CHAPTER 3 Software 3 1 Data acquisition software Real Time Data Acq Computers kaptah1 kaptah2 101 U09 dsa S 1d Woy sjeuBis 937 93 101 U09 dueaid 545 J03u02 dueaid 933 Acquisition server collector Control Electronics control server janitor EEG electronics janitor eeg For a data acquisition software block diagram see Figure 3 1 Data Acquisition System Software Structure Network TCP IP Acquisition Workstation connections sinuhe Acquisition Online average Data gt control megacq response display xplotter Head Position Indicator hpi Online r7 saver A o p averager average e b p aa eee B B Raw data ELE n Lr display rawdisp ct o ee a o p rawsave A K lt Raw data r Js 8 P legging d J o par iel KELE x E e Y Automatic SQUID P P tuner tuner Manual SQUID tuner squiddler helium log Helium level i d i logger neiiumd Figure 3 1 Data acquisition software block diagram 3 1 1 Neuromag directory tree Neuromag root directory e neuro he root directory of the Neuromag tree and a symbolic link to net sinuhe opt neuromag created on every workstaion opt neuromag Neuromag software is physically installed under this directory on one or all of the workstations 2008 11 11 37 H Software 38 3 1 2 MEG MRI data areas neuro data the main data
21. During normal use the extension tube must be removed and replaced by a short particle filter Liquid and gaseous helium A siphon is used for transferring liquid helium from a storage container to the dewar when a refill is needed see Figure 2 9 It is a flexible vacuum insulated doublewall tube 2008 11 11 Hardware and Networking Safety exhaust duct building Liquid Helium filling line with safety Secondary safety relief valve cracking pressure 0 15 bar valve rupturing membrane breaking pressure 0 6 bar Primary safety relief valve cracking pressure 0 15 bar Pressure gauge to indicate the inner pressure Transfer siphon Outside Evaporated gas of the not pressurized building or Exhaust line Liquid Helium n gas Liquid Helium recovery system storage container Figure 2 9 Liquid and gaseous helium systems Helium gas evaporating from the dewar is routed typically via a special exhaust system to the outside air or to a gas recovery system if available The primary safety pressure relief valve prevents build up of pressure if for instance the exhaust line gets blocked In addition the liquid helium filling line leading to the liquid helium space is equipped with a pressure relief valve to provide an independent way of preventing pressure build up if for instance the dewar neck parts get blocked If there is a sudden loss of vacuum helium evaporates abru
22. Vm i vy Vm 2 l e TA EEGopto Tei p Pevi i Lem it AO ORS S i l J Vi 3 3V LL Gm A EEG electronics Lat front end control Vm h ATETA A f Y Vi vi Lom EEG opto P 12V 10 amp eee Ag i La i Vi Lavt tem a Gm 4 4 A AME l Outer Shielded room side l power supply unit 1 pc side NM UU ey Soka rea yas Ree fe ety ERE System grounding point Figure A 8 Schematic diagram of power supplies NOTE The stimulus system is not shown 118 2008 11 11 Technical diagrams ES A 3 2 Recommended power and grounding arrangement E F1 er p E O L Sockets for 2 S4 workstations and g N N OJN other equipment e Olpe min 10 EE PE System grounding point l Filter Unit l Grounding terminal in the transformer room 100 115 120 Magnetically shielded room 200 230 240 V 230V bss eta Mee a PF Filter Sockets F2 L L1 t ER E i ee L1 pod i i S2 0 S S6 NS NM NI ser L2 gt e o e a RY PE Le a a a J T2 Sockets F3 lL L1I F7 4 ao SS O i S3 E S5 He L2 l NSS F8 el l l tr i pr E LO PE 1 Socket for lifting unit Stimulus cabinet F4 L WES qp d T4 230V L i O
23. block dia gram of the EEG electronics see Figure 2 17 For a schematic diagram of the EEG electronics see Figure A 2 The EEG system comprises 64 chan nels optionally expandable to 128 channels The electronics is divided into the following blocks e Preamplifier unit inside the probe unit including built in electrode interface e Opto isolation feed through filter inside the filter unit e Isolated power supply inside the filter unit e Control non isolated power feed through filter inside the filter unit EEG main electronics rack in the main electronics cabinet MEG elec tronics use the same data acquisition computers 28 2008 11 11 Hardware and Networking B Magnetically shielded room Filter unit Main electronics cabinet Signal and control cables Main MEG electronics rack Probe unit Isolated power j f fy i Supply i P pr ecd J 1 Electrode Control ai VE unit ee i 1 panel tes A ey i 4 Opto i Main EEG electronics rack isolation a res Ee HA _ Preamplifier power supply unit Pa JN i Switch i RT computer VME rack BENE EEG JE SAN preamp i L Mains distribution unit a at LT LI Figure 2 16 EEG electronics components 2008 11 11 29 Hardware and Networking Digital control RS422 floating 12 V EEG control feedthrough filter EEG preampl
24. created SSP operators Start Acquisition Open the Scales menu and click SSP On Off to see that when the vectors are on the raw data display is less noisy If the SSP operator is not functioning it probably means that the neuro ssp online fif file or the file it points to does not contain valid SSP vectors or is unreadable When both online upright fif and online supine fif are present the Gantry Position Select utility in Neuromag Maintenance toolbox can be used for switching between these two SSP operators The newly selected operator is activated at the next acquisition start GO button 2008 11 11 System Performance Verification ES 7 1 3 7 1 4 MEG noise measurements Before noise measurement all channels must be operating well The aver age noise level in the Tuner program SSP activated should be about 3 3 SfT VHz or less For MaxShield systems refer to instruction NM23167Y as well 1 From Acquisition control select Sampling rate 1kHz and Low pass filter 330Hz 2 Record at least 1 minute raw data for the noise analysis Check that during recording channels stay operative For Maxshield systems use the active compensation feedback and the feedforward system if installed MEG noise data analysis 1 Open a terminal window and issue the following command neuro bin util maxfilter nosss f filename fif where filename is the name given in previous step This will produce a processed ilename s
25. determine which things have changed since the system last operated without problems The following are possi ble common causes of artefacts the list is not exhaustive e Improper grounding of stimulators or other peripherals causing cur rents to flow in the walls of the magnetic shield stimulus artefacts 72 2008 11 11 Troubleshooting g line interference computer data transfer artefacts gt Check that grounding is single point only e Multiple grounding points due to imporperly added equipment line interference gt Check that grounding is single point only e RF interference from external sources caused by unfiltered cables to the inside of the MSR increased noise gt Check that only shielded leads are fed inside the shielded room e Active digital equipment in the stimulus cabinet inducing interference to leads going inside the MSR gt Shield the device or preferably have it outside the stimulus cabinet and feed the signal through a feedthrough filter e Stimulus cables improperly connected stimuli not coming artefacts line interference or RF interference Check cabling Magnetic objects near the sensor array lead trapping of flux in the sen sors causing flat or noisy channels Detrap using sensor heaters 6 2 3 Trapped flux in the sensors Strong magnetic fields in the vicinity of the sensors may cause flux to be trapped inside the films In particular if magnetized objects
26. etre te 55 CGA Juro id cet east dtd ues eus SU S aar B des tos dient 56 GOOLOOWET Ce cotta a dod ut edo OR ren ee Ow mel V dion DR puli 56 System performance verification 002000 58 Chapter 5 Maintenance Checklists 59 5 1 Systent CHECK eas eae eR wa idc do dock dolar eae Beca 59 5 2 Magnetically shielded room 59 5 3 The probe unit co 6 eck tee ee ee xx ee 61 5 4 Cryogeni6S aii ace i eE hcic a acea i oN Re eR eae es 61 5 5 Gantry and Chall iv coosea wRE ORRCRU CUERO RR RR 64 5 6 Electronics cabinets leeesless 64 5 7 Computer system ivo dide 9e RR REX gos 66 5 8 HPI system and 3D digitzer 66 5 9 Helium level gauge eese 67 5 10 Intercom and video if installed 67 5 11 Cryogenic accessories box 67 5 12 TORING PP E ee A eee eee eel bia Pie 68 Chapter 6 Troubleshooting 69 6 1 Isolating the problem in MEG channels 69 6 2 COMMON problemS i iaa soa ee aw nen imn e n c 72 Flat or noisy channels 2a puoi Rb Roe me tm ics 72 Artefacts ux ears tase oon tae dca reno ud ke uin 72 Trapped flux in the sensors 000 eee eee 73 Excess moisture on the top plate 2005 74 Helium boiloff a ore use hes hate mcr cada Db Dedi Be Ag Ae wee dide doce 75 Overheating electronics fans filters 75 6 3 Software and networki
27. from the nominal value Calculate the error in position for each dipole the mean error for all dipoles and the mean amplitude 5 Fill out the results on the phantom test form The individual position differences should be less than 5 mm and the mean dipole moment within 5 from the nominal value If you used a spreadsheet to calculate the results attach the printout 2008 11 11 87 Ed System Performance Verification 88 2008 11 11 System Performance Verification ES 7 3 EEG testing 7 3 1 Required items 7 3 2 The following items are required to perform the EEG testing EEG signal terminators EL20814K EEG test signal adapter Calibration adapter with a 60 dB attenuator EL20844K for 64 channels or EL20867K for 128 channels with a copy of data sheet EL20844Y having the same serial number as the calbiration adapter Utility programs neuro bin util fiff downsample Layout neuro lout vv eeg all test lout Graph function home neuromag lisp print rms lsp Graph setups home neuromag lisp setup eeg spectra setup home neuromag lisp setup eeg rms lsp Calibration instructions EL20868Y Test form EL20980Y Note If the above mentioned files cannot be found they can be obtained from Elekta Neuromag Copy the files to appropriate loca tions Preamplifier control check The following steps test the communications between the janitor eeg software module and the EEG preamplifier hardware l 2 Check that t
28. g Troubleshooting 6 2 Common problems 6 2 1 Flat or noisy channels 1 If several channels show flat or noisy characteristics first check the liquid helium level and transfer if necessary The most common reason for flat or noisy behavior of a channel is improper tuning or magnetic flux trapped into the squid sensor Look at the flux vs current characteristics of the xy digital scope using the squiddler program refer to the tuning instructions given in the Tuner Manual 2 Check the following and adjust if necessary Check that the modulation depth is not suppressed there is no flux trap by heating the sensor Check that the bias is optimal curve not clipping or biased too high Check that the offset is optimal curve is crossing zero not too close to peaks or valleys of the curve Check that the gate is optimal no instability is visible Check that the curve is not skewed no moisture problem Check that the curve is not showing more periods than usual Com pare with neighbour channels this is to check whether the sensor unit input circuit is working properly Replace if necessary 3 After this fine tune the noise adjustment mode If the output cannot be corrected by tuning try another working point by varying the bias to a higher value 4 Adjust the offset and gate accordingly 6 2 2 Artefacts Try to remove the problem by simplifying the setup until the problem has been identified Especially try to
29. goggles if necessary and N A check for wear 66 2008 05 09 Maintenance Checklists H 5 9 Helium level gauge Table 5 9 Checklist for the Helium level gauge Action Measure Limit OK NOK Check the local gauge on the gan N A rty Check the calibration of the He lt 0 He gauge 5 10 Intercom and video if installed Table 5 10 Checklist for the intercom and video Action Measure Limit OK NOK Check the intercom system speak N A ers and microphone Run an empty room measurement N A using the intercom during the mea surement and check that there is no increase in the noise Clean the video monitor system N A Adjust TV monitor for optimal N A contrast and brightness Clean TV camera lens and monitor N A screen 5 11 Cryogenic accessories box Table 5 11 Checklist for the cryogenic accessories box Action Measure Limit OK NOK Check the cryo kit making a note N A of the parts and replace if neces sary 2008 05 09 67 H Maintenance Checklists 5 12 Tuning Table 5 12 Checklist for tuning Check tuning of all channels 68 2008 05 09 CHAPTER 6 Troubleshooting 6 1 Isolating the problem in MEG channels In the tropubleshooting situation of MEG channel problems it is improtant to try to isolate the problem when the system is cooled down If the trouble shooting of cooled system shows that the problem is inside the
30. helium in this calibration mode 19 Move the switch in the calibration board to the actual position 20 Now the helium level meter s local display on the gantry and the jani tor program should indicate that the helium level in the dewar is 0 21 If the helium level readings were not 0 and 100 as explained in Steps 18 and 20 repeat Steps14 20 22 The calibration has been completed when the helium level is 0 and 100 in the janitor program and on the local helium level display 23 Enter the quit command 24 Switch off power from the preamplifiers in the electronics cabinet 25 Remove the calibration adapter from the preamplifier position 27 and install the original adapter board 26 Close the covers 27 Power up the preamplifiers Note Follow the recommended power on sequence 2008 11 11 123 B Fine calibrations of the He level meter Figure B 1 He level meter board with covers on inside the gantry 124 2008 11 11 Fine calibrations of the He level meter B Figure B 2 Helium level meter local display on the left side of the gantry Figure B 3 Helium level meter board covers removed R56 is the upper adjustable potentiometer and R55 is the lower adjustable potentiometer the board is in the ganty in this position 2008 11 11 125 B Fine calibrations of the He level meter 126 2008 11 11
31. i i l 67 i i t l E SF 7 3F eo i a DG T 13B i 3B a grad SQUID aac e p v sy Hm d 2 ec i 9 13G 13G 1 3G is L ER gt Tu 50 12 T1 5 2 e l VS T3N oN TW 1 I ii i i i EHE l G TGV TGV GI GI ES i ne 1 l I I 1 i i lt i Heater R 802 4K or s TH b 1 1 1 1 1 Lo ea ee a Se ee te DB e ra Se ee e 1 hier teg Se eoa da Re E et 1 Lee ET 4 sensor elements 2 sensor 16 sensor 4 sensor sensor adapter el cable el board el board Part list see SQ201720 Note Product Included in Title reference without revision Vectorview Probe unit Probe unit schematics Date 24 8 2000 Part drawing n o pese JKn Ya Neuromag 5 0291725 8 24 8 2000 Typo correction g part list SQ201720 Appr Figure 7 5 Equivalent circuit for the insert 104 2008 11 11 System Performance Verification ES 7 5 4 Test procedure The following procedure describes a complete test of the insert wiring Even when testing a single channel only it is advisable to take reference readings from neighbor channels Note Preamplifier slot number 8 is different from all others see below Note The insert contains components which may be permanently damaged by static electricity Proper precautions such as wearing grounding wrist straps must be taken 1 Insert the test adapter to the preamplifier slot to be investigated Con nect the ribbon cables between the respective connectors of
32. insert elec tronics the system needs to be warmed up Please consult with the MEG support before if you indentify the problem to be at the insert electronics before doing maintenance actions to the insert electronics In the following chapters we explain the steps that one should take when troubleshooting a problem in MEG channels Isolating the problem in MEG channel while the device is still cold In Elekta Neuromag system there are totally 26 identical MEG signal routes from SQUID sensors to Realtime computers Figure 6 1 a illustrates a simplifed view of two channels signal route in normal operating condi tion This chapter defines how the signal route can be trouble shooted by isolating the different parts in the signal route It is easiest to start working from the preamplifier printed circuit board pcb towards the real time com puters following the signal flow Below is an example of the trouble shoot ing a problem in MEG channels Example troubleshooting a problem in misbehaving MEG channels Study the situation first by looking the channel data from the Data Acquisi tion work station raw display use the below check list to trouble shoot the prolematic channels 1 Check the channels from the raw display Notice if there are several channels which have the problem or is it just one channel write down the number s of the channel s which have problem s 2008 11 11 69 g Troubleshooting 70 2 3 Heat the c
33. set heater21 heat on off 0 set heater22 heat on off 0 set heater23 heat on off 0 set heater24 heat on off 0 set heater25 heat on off 0 set heater26 heat on off 0 f Restore initial settings cp p neuro dacq setup janitor config ok neuro dacq setup jani tor config g Select RestartAcqPrograms with b option in Maintenance window 8 Switch on 12 lower section heaters and monitor the dewar pressure The pressure should not exceed 0 1 bar in the dewar gauge If pressure exceeds 0 1 bar reduce the number of active heaters if the pressure 50 2008 11 11 Preventive Maintenance n does not rise increase the number of active heaters while monitoring the dewar pressure Place paper towels under the fixed siphon tip to keep the electronics dry 9 Monitor the resistance change in the multimeter When the resistance value has reached 150 Ohms the temperature inside the dewar is c 80 K The He gas flow from the dewar should have stopped The helmet surface will normally frost at this point Protect the floor from moisture from the helmet surface and helium gas exhaust line at fixed siphon area 10 Switch on all the heaters in the dewar 11 Connect the silicone hose to the nitrogen cylinder regulator 12 Flush the hose with nitrogen gas adjust the pressure for minimum flow 13 Connect the hose into the KF25 7 mm adapter 14 Add nitrogen gas into the vacuum pinch the hose one meter form the valve adaptor with th
34. side window in the SSP Dialog win dow The program will apply the selected 5 vectors to the raw data Check the operation of the vectors by selecting On and Off from the SSP Dialog window Write average X Y into the command line X and Y are the same start and stop times of the good signal After Y the signal must be good 10 seconds Check that the histo 1sp file is available Execute the require histo command in the directory where histo lsp is located The command loads a histogram calculating program for the Graph program Execute the histo 1 10 command to calculate the average noise from 1 Hz to 10 Hz Save the results with the save result name of the file command Repeat the above for the following frequency range 60 70Hz 60Hz 70 80Hz Repeat the whole noise analysis for the gradiometers 2008 11 11 System Performance Verification ER Write MEG 2 and MEG 3 into the names in the Pick widget 26 Check the results with the text editor For the limits of the noise test refer to NM23168 27 Enter the results to the NM23168Y form 7 2 Phantom test 7 2 1 Measurement l Connect the phantom excitation multiplexer into the multiplexer cable with a 25 pin connector which is under the side cover of the gantry Start the acquisition program Select or create a project suitable for phantom measurement Load the required measurement settings from a template file Select load
35. storage Usually this a symbolic link pointing to another file system neuro mri storage for MR images This may also be a symbolic link to another file system neuro databases subject and project databases as well as the list of data volumes in the volumes file Programs neuro bin vue scripts connected to the MEG toolbox icons These scripts first set up the environment correctly for the analysis pro grams and launch them neuro bin X11 binaries of the graphical analysis programs Do not start them directly neuro bin util various non graphical utilities These can be started from the NeuroTerm terminal window neuro bin admin scripts and binaries started by the CDE icons and other programs Do not start them directly neuro bin dicom programs related to DICOM image transfers Do not start them directly e neuro bin mri admin utilities for importing MR images neuro dacq bin acquisition programs for both the workstation and the acquisition computer System data neuro lisp LISP code for the off line signal processor program Graph neuro lout layouts of the plotting and source modelling pro grams e neuro dacg dau fixed configuration files channel assignments calibrations DAU programs for the VME data acquisition systems e neuro dacg vxi fixed configuration files channel assignments calibrations DAU programs for the VXI data acquisition sys
36. system with the Tuner program Check all channels in the Raw data display and save the parameters For Maxshield systems check the operation of the feedforward sys tem according to NM20594A A and the feedback system according to NM231061 Y Enter the results in the forms referred to in the instructions 2008 11 11 77 Ed System Performance Verification 7 1 2 Making online SSP vectors 78 Signal space projection SSP vectors can be generated when all the chan nels are operating and are tuned correctly The vectors are dependent on the position of the device and that is why the vectors must to be made for both upright and supine position 1 Record raw empty room data for both positions for at least one minute Use 1000 Hz sampling 330 Hz low pass and 0 1 Hz high pass filtra tion Save the data with a name like empty_room_upright or empty room supine and mark down the path where the file will be saved Monitor the channels raw data during the measurement to make sure that the signals do not saturate If the signals saturate the measurement must be repeated Start the Signal processor Graph program Load or create a Graph setup which includes at least ssp and pca packages in addition to the basic setup Load the magnetometer noise setup file from the load settings tool bar File gt Load Settings if it is available The file contains the needed widgets Otherwise load a basic setup and
37. the average mode step average trigger eeg 0 and average window win from the Parameters averager menu Open the EEG_noise fif data file and enter the average 0 60 command When the calculation of the averages is finished inspect from the dis play averages whether the noise level in some channels is substantially different from the others for example because of popcorn noise This is seen easiest if all channels are superimposed for a while by setting superpose on from Resources Popcorn noise manifests itself espe cially as increased low frequency noise Use for example scale 1e 7 offset 1 start 0 Hz and length 100 Hz in the display averages Note that the noise level in differetial channels may be different than in uni polar channels Identify channels with excessive noise use also the pick widget eeg and display widget display as help Suitable parame ters for a display widget are for example scale 1e 6 offset auto and length 1 s If necessary if no data is seen or a wrong number of chan nels is displayed refresch the links to display widgets drag with the rightmost mouse button depressed from the widget root to the widget averages and from the widget eeg to the widget display Continue debugging as usual If parts have been changed appropriate parts of this test must be repeated 2008 11 11 97 Ed System Performance Verification 7 4 Noise measurement testing 98 Before noise measurement all channels must be op
38. the filter at the end of the fixed siphon Make sure not to put too much filter material in Check the o ring of the fixed siphon in the siphon feed through on the top plate and grease slightly with silicon vacuum grease Transfer siphon Check the siphon for wear By interviewing the end users find out whether there have been abnor mally high transfer losses or cold siphon surface during the transfer Check the o ring in the vacuum close valve by opening the valve counter clockwise and replace the o ring if needed Screw in the siphon vacuum close valve Re evacuate the siphon vacuum 2008 11 11 Preventive Maintenance n 4 4 6 4 4 7 4 4 8 6 Connect a pumping line to the vacuum pump out port and open the valve by turning the screw counter clockwise Be careful not to unscrew the screw completely The residual vacuum pressure must be below 5 Pa no flow condition Tighten the pump out port screw Check the o ring on the nozzle of the siphon and grease slightly with silicon vacuum grease Safety exhaust check 1 Check that the safety relief valve opens easily by prying it gently with your fingers 2 Remove the safety exhaust duct from the top of the probe unit and check that the rupture foil unit is not damaged The foil is covered with foam plastic damping pieces Replace the foil if necessary Put the foam plastic pieces back 3 Put the duct back and check the duct and joints fo
39. the test adapter and the tester Connect the multimeter common terminal to GI 2 Connect the multimeter ohms terminal to GV Go through channel selector positions 1 1 4 3 The correct reading is 130 30 Ohms 3 Connect the multimeter ohms terminal to the protected Prot terminal 4 Switch the multiplexer Mux rotary switch to position B and the chan nel selector to 1 1 The correct reading is 10 2 40 2 kOhms 5 Switch the multiplexer Mux rotary switch to position F and the chan nel selector positions 1 1 4 3 The correct reading is 20 2 0 2 kOhms unchanged if the system is in the superconducting state and about 40 50 kOhms if the system is in the normal state The pressing of the button decouples the current path from feedback to B and V via the FET forcing all current to flow through the feedback coil The actual reading in the normal non superconducting state may vary significantly depending on the individual parameters of both the FET and the coil A clear change 21 kOhms in the resistance should however be observed An open circuit reading indicates a problem in the sensor adapter wiring unit or the sensor itself Release the button and observe that the reading goes back to its original value Repeat the test for channel selector positions 1 1 4 3 Note Sometimes the autoranging circuitry of the digital multimeter gets confused when the FET button is depressed resulting in errone ous display flashing or osc
40. using the lisp command line at the top of the Graph window Load the following modules using the lisp commands require pca require ssp require std selections 2008 11 11 System Performance Verification 7 9 10 11 12 13 Now open the control panel from the displays tool bar Connect the widgets as follows file diskfile gt buffer ringbuffer gt meg pick gt ssp suppressor gt pick pick gt display plotter Connect by moving the cursor on to the first widget click the mouse right button hold it down drag the line to the second widget and let go of the right button Double click the ssp widget and change the buffer size to 20000 Then double click the ringbuffer widget and increase the buffer size to 1000000 Double click the file widget and load the empty room upright fif file from the directory where it had been saved Making the a11 fif file 1 To choose all channels double click the meg pick widget and type MEG into the Names field It may be necessary to cut and reconnect the display widget line to get the display updated By using the right mouse button select a short time span of data less than one second on the display Then select Make evoked file from the File menu of the Graph win dow Name the file to be saved all fif Double click the file widget and load the empty room upright fif file from the directory where it had been sav
41. works properly Measure temperature and humid See Site Plan ity inside the room compare with ning Guide environmental requirements Check the ramp of the room N A Cleaning Check that no foreign objects have N A been brought into the room that might cause disturbances Have the room cleaned up N A 60 2008 05 09 Maintenance Checklists H 5 3 The probe unit Table 5 3 Checklist for the probe unit Action Measure Limit OK NOK Dewar performance Check the boiloff rate and review See specifica the Helium statistics collected tions Check for cold spots in the dewar N A Warmup Check when the vacuum has last 12 months been re evacuated Perform complete warmup to room N A temperature Re evacuate vacuum 5 Pa If total warmup is performed N A check and grease slightly all the O rings of the probe unit and inspect the safety exhaust rupture for leaks Cable check Check all incoming cables for wear N A and verify the connections Cleaning Check that no extra items have N A been glued or fixed to the surface of the dewar Clean the dewar surface with alco N A hol 5 4 Cryogenics Table 5 4 Checklist for cryogenics Action Measure Limit OK NOK Fixed siphon Warm up and dry the siphon N A Check the fixed siphon for wear N A 2008 05 09 61 H Maintenance Checklists Table 5 4 Checklist for cryogenics Ac
42. 0 1100 Ohms if the system is at room temperature 3 Connect the multimeter ohms terminal to H and the common termi nal to 2X Go through heater selector positions 1 4 The correct reading is 130 30 Ohms 4 Connectthe multimeter ohms terminal to H and the common terminal to 3X Go through heater selector positions 1 4 The correct reading is 130 30 Ohms 7 5 5 Testing for cross talk between channels The wiring tester is designed for measuring only one channel at a time and normally this is sufficient If inter channel cross talk is suspected readings must be taken directly from the test adapter Euro 64 connectors See Figure 7 6 Pinout of the test adapter Note that the channels in the same sensor element XXY 1 XXY3 share a common ground thus there are a lot of apparent interconnections between the channels See Figure 7 5 Equivalent circuit for the insert However there should be no interconnections between channels in different sensor elements 2008 11 11 System Performance Verification ES Note An external 10 kOhms resistor in series with the multimeter test must be used to prevent damage due to static electricity 11G Oo O0 14V Oo O 1 Gl o Oo 1GV Oo o m 1 2G Oo 1 2V Oo oO a 1 3 F o 1 3 B o o re 1 3 N Oo 7O 1 3 X o o 24F o o 24 B oO O0 21N O O0 2 1X oO Tee 2 2 F Oo O0 2 2B o o 2 2N o o 2 2 X Oo oO ES 23G o o 2 3V o o 2 H
43. 2 2008 11 11 CHAPTER 4 Preventive Maintenance 4 1 Planning preventive maintenance There are three kinds of preventive maintenance PM 1 Full PM interval 1 2 year s e Target is to fully go through the system related to all main modules in the system e Full PM is based on the evaluation of a local BU MEG technical spe cialist and it can be done either once a year or every second year If the full PM is performed every second year the interim PM is performed in between these PMs 2 Interim PM interval 1 year e If the full PM is performed every second year the interim PM is per formed between the full PMs 3 Lifter PM interval 5 years e Lifter PM is carried out every fifth year to secure the safe and prob lem free functioning of the lifting mechanism e This plan is typically connected to either the full PM or interim PM but can also be a separate preventive maintenance visit Table 4 1 Preventive maintenance plans Plans Full PM Interim PM Lifter PM Module Initial system check Warm up Vacuum pumping of siphons 2008 11 11 43 g Preventive Maintenance Chair checks Bed checks MSR checks Electronics K LK X X Vacuum pumping of the dewar FK HK X x Insert wiring test x Cool down X Initial testing after cool down Safety exhaust check Lifting unit verifica tion Lifting unit mainte nance
44. 5 _ Control Unit fiter driver Bus Bus E net y saui SQUID Feeathrough L saup Ene E Sensor lt Preamplifier filter electronics Data acquisition 7 and control unit net Acquisition Patient 306 channels Bus 306 channels Bus Realtime Acquisition saui sQUID o Feedthrougn L sauin ET computers Sensor lt Preamplifier 7 filter electronics Bus EEG EEG Feedthrough EEG E net Electrode 2 Preamplifier Ee filter amp opto Ee electronics gt 3D 64 channels Bus 64 channels Bus digitizer E net EEG EEG Feedthrough EEG Electrode 24 Preamplifier ZE beer Lalas ES electronics C Bus Control Feedthrough Fiber optic link Bus E filter Figure A 2 Block diagram of the electronics 112 2008 11 11 Technical diagrams A A 1 2 EEG electronics Filter unit Rf shield em ae AS nok eae hae Shen CES ES MTS l Isolated power feedthrough Ry amp sen m dE Z 24 vj 230 V Isolated gnd 7 Preamplifier unit 9 RT om Re E l Osc Isolated Safet
45. Do not add any equipment to the system or change any cabling without considering the possible side effects If in any doubt contact Elekta Neuromag The applied part of EEG is electrically floating in other words isolated from ground It must not be grounded in any circumstances For potential equalization between the isolated preamplifier and the patient it is neces sary to connect the patient to the isolated signal ground of the preampli fier For that purpose a terminal labelled GND is available in the electrode interface panel To limit the patient current flowing through that terminal to a safe level the preamplifier signal ground connection is pro vided through a current limited ground driver of the preamplifier The iso lated preamplifier signal ground is not directly accessible when headboxes and electrode caps supplied with the system or which are available as options are used The isolated preamplifier signal ground which is only available internally must not be connected directly to humans as the max imum allowable current may be exceeded in a fault condition Warning Do not connect any of the electrode inputs of the side panel or the headbox to actual ground for example the wall of the magnetically shielded room Care must be exercised to avoid contact of conducting parts of the electrodes including REF and GND electrodes to ground or other conducting parts which may be grounded or become live at mains voltage Do n
46. Elekta Neuromag Elekta Neuromag Service Manual Nov 4 2008 ELEKTA Contents Chapter 1 Introduction 1 1 1 Purpose of this manual ees 1 1 2 Safety instructions ii ssec dr aaa dance RR rar ERR EA 1 Properties of helium s rore rou trea ae Reverso Ra tees 1 Warnings concerning the dewar and cryogenics 2 CHODUMPING 25 15 2 cit gat ook 18 8 ttbi kee tid eerie betes 3 Electrical Safety cc ool club ce Ses pee E wv Ets E 3 Mechanical safety s dup are ra aru Cre ER RS 7 1 3 Hequired tools 44 xk Ep rwy EE Ye n 7 General tools 2535395 eR teh NL sed ds 7 Special tools 2d avion encor dre eR tnodo RANE epa ELE aset 8 Tools available at Site 2 2 eee 9 1 4 Overview of the system 9 Chapter 2 Hardware and Networking 11 2 1 Probe UNIT cose oe eens ua arr yew arde kee us 11 lniifo s Pierre END TE 11 Sensor insert and the dewar lllllllsu 12 Liquid and gaseous helium sllesssss 20 Lifting mechanism essa a Ue beni bite sehen dae RE E 22 2 2 EleclrofilCS uociciloo ow RR eee hes ees ERR 26 Main electronics cabinet 0 0 cece eee eee 26 MEG electronics 2s voe eerie 418 a 3 9 59 3 895 000 n art dc nca dn 27 EEG electronies 52e es bw e ERR ORS eo eI ADR ids 28 2 3 Auxiliary hardware modules 30 E Tie t ORE x t aoc turand ed dam Vet M p pull DEAE hd QUON quls eed aC mE 30 HPTarnd SD di
47. NG V 4 SX4 S4 vO ko Fiber pair Y Out lowest pos gt Th Fal S ANE K Gnd l p EY j JEN Lowest pos a l l no reflection SX4 Indicator display dark on l 12V 5 l i l 230V gt t piece 9 50 60Hz GND eh E 4 5 l e l l Pushbutton 4 gt UP l 4 c Up 4 d i e D l 230V gt i 1 50 60 Hz Hu Pushbutton eei Hl d 5 DOWN T N ca Down i T E ET D 7 l l i EIER te iN ri E ET r Se E E m e m A ET E Lifting mechanism indicator feedthrough assy Outer side _ Inner side Figure A 6 Schematic diagram of lifting mechanism electronics 116 2008 11 11 Technical diagrams A A 2 Electronics cabinet L1 230 V EMC filter Circuit breaker Main switch with power failure release IER et i 4 x from isolation transformer L2 PE From main o grounding L point i X 4 x EEN H A Mains sockets Roof fan Ethernet switch Auxiliary sockets Mains sockets Main DSP electronics Mains socket RT computers Mains socket Preamplifiers Figure A 7 Mains distribution in the main electronics cabinet 2008 11 11 117 n Technical diagrams A 3 Power supplies A 3 1 Schematic diagram n Main electronics cabinet
48. ailable as options Power supplies and grounding Warning The power supply of the electronics must be connected only to the power outlets inside the electronics cabinet which are connected to the mains via an isolation transformer Internal power cabling must not be changed 4 2008 11 11 Introduction Warning The 3D digitizer power supply must be connected to mains via an isolation transformer supplied with the Elekta Neuromage system The main electronics is powered through medical safety isolating trans former connected to electronics cabinet outlets Therefore internal power cabling must not be changed For schematic diagrams of the powering see Figure A 8 and Figure A 9 voltage conversion if needed Inside the main electronics cabinet the volt Warning The isolation transformers also provide step up or step down N age is 230 V Main electronics cabinet Stimulus cabinet l OO f NS RF Feedthrough cabinet Main grounding point To main ground at electric switchboard building transformer ground Figure 1 1 Grounding of the system Warning The RF line filters in the stimulus cabinet contain large capaci tors Thus voltage may remain across terminals even after the power has been switched off from the filter The filt
49. al cable between EEG preamplifer frontplanes 3 Signal cable between electrode interface panel and preamplifier frontplane 4 Signal cable between preamplifier and signal feedthrough filter unit 5 Control power cable between preamplifier unit and control feedthrough filter 6 Power cable control between feedthrough filter and EEG signal feedthrough filters 7 Power cable between isolated power supply and EEG signal feedthrough filters EEG optoisolation I signal feedthrough filter 4 pcs 16 channels unit EEG Ch 65 128 to ignal Acquistion Module Magnetically shielded room wall RF feedthrough wall Parts inside the box ONLY in systems including 128 channels Floating applied part Grounded normal electronics Figure A 4 Block diagram of the EEG electronics 114 2008 11 11 Technical diagrams A A 1 3 Auxiliary electronics Feedthrough Helium level probe multiplexer z 300K 42K filter MEG Dc power Display Dc power ZN probe ecu He 5 bu zd U probe sensor 5 A l o 8 o 5 fa p de E D A D DVM Tem 0 I maintenance pera ture i
50. ar including liquid helium and the dewar supporting cradle moving with the sensors is approximately 200 kg To ensure that the dewar is prevented from falling down from the seated measurement position under any circumstances it is equipped with two completely separate and parallel support mechanisms both of which alone can withstand at least a fourfold overload compared with the normal working condition Warning The dewar position must not be changed while the patient patient chair or any other person is under the gantry Required tools General tools The following tools are required to service Elekta Neuromag Please make sure you have these tools available before you start any service proce dures 2008 11 11 7 EH Introduction 1 3 2 e Set of Phillips screwdrivers Set of Torx screwdrivers Set of PoziDriv screwdrivers Set of Slotted screwdrivers Set of wrenches metric e Tongs Pliers Portable metal saw e File Set of needle files Tweezers Set of hexagonal keys metric Ring spanner set Lock jaw pliers Digital multimeter with true RMS readout Tape measure Wire stripper Needle nose pliers e Soldering iron e Flashlight Scissors Sheath knife Ethernet cable Modem cable Ground cable Antistatic mat e BNC RCA cables Fuses Cleaning alcohol Service checklist Special tools In addition the following special tools are required to service Elekta N
51. cable runs to the main station via the feed through filter The loud speaker for the main station is outside of the magnetically shielded room attached on a separate feed through tube on the magnetically shielded room wall 4 2 3 4 Video monitoring system optional For a schematic diagram of the closed circuit television system see Figure 2 22 Figure 2 22 Video monitoring system The camera 1 is placed inside a separate RF shield The cable 2 goes through a dedicated feed through to the monitor 3 The camera should be kept further than one meter away from the Elekta Neuromage to avoid additional noise 2008 11 11 33 E Hardware and Networking 2 3 5 Stim systems optional 34 A 16 channel trigger pulse digital input output interface is provided for synchronizing the measurement software and stimulators not supplied with the standard system used for evoked response studies The interface unit is optically isolated from the main electronics and data acquisition system The RF shielded stimulus electronics cabinet is used to prevent possible RF disturbances caused by stimulus devices from entering the magneti cally shielded room RF filtered feed throughs are available between the inside and the outside of the cabinet Active digital circuitry for example a computer inside the stimulus cabinet should be avoided 2 4 Workstation hardware The standard system configuration typically includes t
52. channels follow the usual hardware debugging procedures swapping parallel units temporarily replacing boards to fix those channels 4 Repeat this for all other channel sets Do not proceed until the hard ware is acceptable Amplitude and phase check 1 Enable the test signals from the built in signal generator in the EEG control click the ALL button channel number field shows ALL then click Test Osc input to On and finally Test Osc to On 2 Set the EEG scale of the raw data display to 300 pu V There should be a clean sinusoidal wave on all EEG channels Every other channel should be 180 degrees out of phase the test signal feed is inverted not the input The amplitude of the differential channels typically EEG61 EEG64 can be different from that of the single ended chan nels 3 If signal is not obtained for some channels check the signal cables damaged pins on connectors and try to swap cables and feedthrough filter units 2008 11 11 91 Ed System Performance Verification Channel assignment check 92 l Click the ALL button again to go back to the individual channel con trol mode Start from channel EEGOO1 Click Active to Off while observing the corresponding trace on the raw data display it should become flat Click the channel back On The sinusoidal trace should appear again Advance to the next channel and do the same check Check all the EEG channels this way If the on off response is
53. command 14 Janitor replies with the helium level reading in percents at the end of the text line 15 Adjust the zero level potentiometer of the helium level meter board in the gantry The zero level potentiometer is marked with R55 see Figure B 3 The goal is to adjust the potentiometer so that the helium level reading just changes from non zero value to zero a Make a slight adjustment to R55 b Perform the helium command c Janitor replies with the helium level d Repeat Steps a to c until the potentiometer setting is as close as possi ble to the position of the first non zero reading 0 4 but the meter is still showing zero 16 Turn the calibration adapter switch to full 17 Adjust the full level potentiometer of the helium level meter board in the gantry Figure B 3 122 2008 11 11 Fine calibrations of the He level meter B The zero level potentiometer is marked with R56 The goal is to adjust the potentiometer so that the helium level reading just changes to 100 a Make a slight adjustment to R56 b Perform the helium command c Janitor replies with the helium level d Repeat Steps a c in until the potentiometer setting is as close as pos sible to the position of the first reading below 100 99 6 but the meter is still showing 100 e Then turn R56 a turn clockwise 18 Switch on the helium level meter s local display Now the helium level indicator LEDs should be all on indicating 100
54. cuum valve o rings Filters to siphons Lifter PM Lifting ropes After PM Refill the Cryogenic Accessories Kit add replacement for the material that has been used during PM or which is missing in the kit 4 3 Overview of the PM schedule The following time schedule is only tentative and is mainly meant to help in scheduling the activity before the visit but it also gives advice on the work order in preventive maintenance 1 Full PM Day 1 System check takes normally about 1 3 hour s 2008 11 11 45 g Preventive Maintenance Fixing of the possible problems notified by the customer takes 2 3 hours Warm up Step 1 Helium boil off with heaters takes typically 2 3 hours depending on the amount of helium inside the dewar Step 2 Continuation of heating with heaters to 80 K takes typi cally about 3 4 hours Step 3 Final warm up to room temperature takes totally about 10 15 hours e Day2 Finalizing the warm up to room temperature Vacuum pumping of siphons takes 3 4 hours this can be done par allel to some of the other steps Insert wire testing takes 3 4 hours Vacuum pumping of the dewar e Day 3 MSR check takes an hour Electronics check takes an hour Chair check takes an hour Bed check takes half an hour Preparations for the cool down and cool down takes 3 4 hours e Day 4 Initial testing after the cool down takes 2 3 hours Lifting unit verification takes a half an hour Final testi
55. device does not generate radiation During the experiment it is not possible for the subject to get in contact with grounded parts Head position coils on small printed circuit boards are spiral shaped The coils are connected to isolated leads and cast with isolating epoxy No electrical contact to the subject is thus made Current fed to coils is typ 70 A and the resulting field less than 1 nT The EEG subsystem contains an applied part of BF type in galvanic con tact with the subject The applied part has been carefully designed and built to fulfill the safety regulations as set by international standards IEC60601 1 and IEC60601 2 The EEG preamplifiers are optically iso lated and the power supply of the EEG preamplifiers is provided with safety isolation transformer Warning To eliminate any risk of electrical shock hazard the EEG sub system must be properly installed by authorized service personnel and used as part of Elekta Neuromage system according to manuals and assembly instructions Internal cabling must not be changed Note The EEG subsystem cannot be used as a standalone system out side of the magnetically shielded room There are no internal operator serviceable parts inside Head position indicator coils electrode caps headboxes and electrode interface in the side panel of the gantry are the only operator accessible parts of the EEG subsystem Use only headboxes and electrode caps supplied with the sys tem or av
56. e left hand open the dewar vacuum valve slightly until the nitrogen in the hose has flown hose has gone flat into the vacuum of the dewar 15 Pinch the hose near the vacuum valve adapter with the right hand and release the hose in your left hand the one meter is filled again 16 Repeat this cycle Steps 14 and 15 10 to 15 times and close the vac uum valve immediately after the last cycle 17 Connect a clean silicone hose to the fixed siphon adapter 18 Start flushing the dewar with nitrogen 19 Continue flushing of the dewar with nitrogen until the dewar volume has been flushed 3 to 4 times flush volume is about 320 liters e g about 2 3 minutes constant flush monitor the dewar pressure and reduce the nitrogen flow if the pressure increases 20 Stop the nitrogen flushing 2 Connect a normal fixed siphon plug to the fixed siphon 22 Let the dewar warm up with the heaters until the multimeter reading is over 200 Ohms 23 Switch off the heaters and return the Janitor configuration into the normal mode 2008 11 11 51 g Preventive Maintenance 52 4 4 4 The dewar warm up takes about 10 15 hours Note If you need to leave the site before the multimeter reading is 200 Ohms it is absolutely necessary to switch off the heaters and preamplifier power supply Electronics module a 1 b General check points Check all incoming cables for wear and verify the connections Main electronics cabinet
57. e levels in the 10 75 Hz range Print out the graph Average noise level should be less that 5 Note If the system has problems the location of the problem needs to be determined before the warm up starts Check the helium boil off rate and review the helium statistics col lected Note any systematic increase in the boil off rate Check that no extra items have been glued or fixed to the surface of the dewar and remove them if necessary Clean the dewar surface with alcohol 2008 11 11 47 g Preventive Maintenance 4 4 2 MSR checks 48 1 5 6 T Check that the system is grounded by disconnecting the main ground strap measuring the resistance between the room wall and the main ground strap The resistance should be more than 1kOhms If the resistance is less than 1 kOhms typically close to 0 Ohms the extra grounding needs to be identified and removed Note In some cases DC potential may disturb the insulation resis tance measurement Reversing the polarity may remove this distur bance Check that the door mechanism works properly Measure temperature and humidity inside the room and compare them with environmental requirements Temperature range inside MSR 20 28 degrees C Humidity 40 70 If the limits are exceeded make a note to the report and inform the cus tomer Check the ramp of the room Check that no foreign objects have been brought into the room Espe cially cables may ca
58. ed Double click the meg pick widget and type MEG 1 into the Names field to choose all the magnetometers If there are known bad channels which will not be repaired now it is possible to list them in the Ignore field To update the display it may be necessary to cut and reconnect the display widget line Cut by clicking the right mouse button hold it and drag the scissors across the line 2008 11 11 79 Ed System Performance Verification 80 8 10 11 12 13 14 15 16 17 On the Graph display window open the resource task bar and enable the superpose function to get the signals stacked on top of each other On the scale window click the Autoscale button and set the offset to zero By using the lower slider check that the data contains low frequency interferences to be eliminated with the vectors Make sure that channels do not saturate in the time span that will be chosen for vector generation At the top on the Lisp command line write pca on widget meg X Y where X is the beginning time for choosing from the file and Y is the end time for choosing from the file and press Enter Select SSP Dialog from the Commands menu It may be necessary to wait a moment on slower systems until the fol lowing selections can be made Select Add PCA fields from the Actions menu Select 8 vectors You should get an entry like PCA 102 8 in the vector pool Click the entry and select Ex
59. erating well The aver age noise level in the Tuner program SSP activated should be about 3 3 5 fT Hz or less 1 10 11 12 13 14 15 From Acquisition control select the sampling rate 1kHz and low pass filter 330Hz Record at least 1 min raw data for the noise analysis Check that dur ing recording channels stay operative Start the Graph program Load magnetometer noise setup from the File gt Load settings Open the just measured raw data Open the Graph control panel by clicking Displays gt Control Panel Select all magnetometers by writing MEG 1 to the names in the pick widget Open Resources and set display to the Superpose mode Click Autoscale in the Display Scale window and set Offset to zero Scroll the file and check that all channels are in the working area in other words signals do not go to the limit flat Note the start and stop time for the good signal Write pca on widget meg X Y to the command line X is start time and Y stop time for the good signal To execute press Enter Select SSP Dialog from the Commands menu Select Add PCA fields 8 vectors On the left side windows appears 8 102 matrix Select matrix and execute the explode command from the SSP Dialog window Matrix explodes into the 8 vectors Select 5 vectors from the top and activate them with the right arrow button Vectors will be copied to the right side window in the SSP Dia log window Prog
60. ermal conduction from room temperature to the liquid helium bath The cables are mounted inside textile supports and they run from the sensor adapter boards to the insert top flange The dewar is made of inner and outer shells tied together only at the top plate and separated by a vacuum space The vacuum space is also equipped with thermal radiation shields and a so called super insulation which is made of multiple layers of plastic foil coated with a thin layer of aluminium A pump out port with a vacuum valve is located at the back of the dewar A special adapter is needed to operate the valve and to connect the vacuum pump The neck plug provides thermal insulation and directs helium gas boiling off the liquid helium bath to flow along the dewar neck tube When the flow is forced along the neck tube wall the heat conduction along the tube wall is effectively reduced Moreover the thermal radiation shields are thermally anchored to the neck tube to keep them at a lower temperature The cable assemblies are also mounted in the space between the neck plug and the neck tube to reduce thermal conduction A helium exhaust tube is mounted on the neck plug collecting the outflowing gas and directing it out The insert top flange see Figure 2 6 contains support plates and pream plifier motherboards The motherboards made of eight octant sectors make a gas tight signal feed through to the helium space The preamplifi ers mounted in the correspond
61. ers have built in resistors which discharge the terminals in less than 10 seconds All shielding covers must be in place before applying power to the filter The filters may only be per manently installed mains plug connection of the filter is prohibited The power supply units are protected by mains primary fuses All fuses are accessible at the back plane of the MEG preamplifier power supply unit with the correct values of the fuses marked in the immediate vicinity A T before the rated current in amperes indicates slow time lag slow blow type and a F fast type If no type has been indicated use fast type 2008 11 11 5 Introduction AN AN AN fuses Refer to Appendix A Warning To avoid risk of fire and electric shock always use only cor rectly rated fuses as replacement The system except for the EEG applied parts discussed below is perma nently grounded class I equipment according to IEC 60601 1 at a single point main grounding point located at the filter unit cabinet between the electronics cabinet and the magnetically shielded room See Figure 1 1 Warning The grounding cables must not be disconnected Note The system must not be grounded to any other place than the grounding point This is very important since otherwise ground loops will be formed resulting in artefacts in the measurements The grounding system of Elekta Neuromage has been carefully designed and realized see Figure 1 1
62. eu romag e Vacuum pump and valve adapter may be provided at the site Helium level gauge calibration adapter EL 20377T e Insert wiring tester NM 20413K e EEG signal terminators e EEG calibration adapter e L siphon adapter e Thermometer measuring range 15 35 degrees of Celsius Humidity meter measuring range 5 100 2008 11 11 Introduction ES 1 3 3 Tools available at site At the site make sure that there are the following tools e Spare part kit e Phantom Nitrogen and helium gas cylinders and regulators Liquid helium for cooldown 100 liters 100 liters e Cryogenic kit e Vacuum cleaner for collecting dust from the electronics cabinets 1 4 Overview of the system The Elekta Neuromag measures non invasively the magnetoecephalo graphic MEG and electroencephalographic EEG signals produced by electrically active tissue of the brain These signals are recorded by a com puterized data acquisition system displayed and may then be interpreted by trained physicians to help localize these active areas The locations may then be correlated with anatomical information of the brain MEG is routinely used to identify the locations of visual auditory somatosensory and motor cortices in the brain when used in conjunction with evoked response averaging devices MEG is also used to non invasively locate regions of epileptic activity within the brain The localization information provided by MEG may be used
63. ferring for about 10 minutes After this time dewar should have about 10 15 liquid He Open the MSR door and perform the power up cycle to the electronics Turn on the He level meter and check the level of liquid helium in the dewar Run RestartAcquisitionPrograms from the maintenance folder Start acquisition and load the saved set up saved after tuning Check that the channels are working by using the Squiddler program in tune mode with the X Y display All channels should show a tune wave but they might not be in cor rect tune with possible bias and offset errors The errors will correct themselves later when the system stabilizes Check for the non working channels If the number of non working channels is 0 3 continue the helium transfer With a large number 4 or more of non working channels you need to do trouble shooting Continue the transfer until the transfer dewar is empty the helium refill ball goes flat and the helium level meter does not increase or the helium level meter shows 100 Note The next refill is sooner than normally as the boil off of He is 2008 11 11 57 g Preventive Maintenance higher right after cool down 14 Check the cryogenic kit make a note of the parts and replace if neces sary 4 4 11 System performance verification a Phantom test 1 Perform a standard phantom test for at least 10 dipoles 2 Check the calibration of the system by comparing the mean dipole
64. fier power supply see Figure 2 13 For a schematic diagram of the electronics see Figure A 1 For a block diagram of the electronics see Figure 2 14 Tti Bis m 1 OO L IIl LU LIE cs se i T Fell aS ri m Figure 2 13 Mounting of the electronics units inside the main electronics cabinet Left front view right back view 26 2008 11 11 Hardware and Networking B Liquid Control l Feedthrough Fiber optic link Helium I B a fil lt level display us ilter x Stimulus E Liquid Bus triggers in out System net Helium probe Fiber optic controller Analysis link Bus workstation eac postnon LHe HPI Feedthrougn HPl Eset Control Unit 7 filter driver 31 coils 5 4 4 Bus Bus Enetry SQUID SQUID Feedthrough sQuip LER Sensor lt Preamplifier filter lt electronics Data acquisition d and control unit ENS Acc sition Patient 306 channels Bus 306 channels Bus Realtime e workstation 7 u SQUID SQUID Feedthrougn 4 saquin LER Sensor lt Preamplifier 7 filter electronics Bus EEG EEG Feedthrough EEG E7 Electrode EZ Preamplifier ZZ filter amp opto FE electronics gt isolati
65. g The exhaust line must be open at all times Warning To prevent frostbite avoid contact with liquid helium or exhaust helium gas or any object that has recently been in direct contact with liquid or evaporated gas Wear protective gloves and safety goggles 2008 11 11 AN 1 2 3 1 2 4 Introduction Warning Do not leave anyone alone inside a closed magnetically shielded room MSR without the presence of another person outside the room Cryopumping At liquid helium temperature all common materials are solid This means that the vapor pressure of for example the atmospheric gases nitrogen oxygen water is practically zero in any volume containing liquid helium which leads to cryopumping of these gases any helium vessel left open to the atmosphere will very effectively suck in large amounts of these gases Water freezes and may block the helium vessel or a transfer siphon Oxy gen in the probe unit dewar causes large irregular low frequency drifts of MEG signals because the magnetic susceptibility of the paramagnetic oxygen in its solid form is very high Note To prevent cryopumping observe the following precautions All helium vessels must be sealed from the atmosphere and prop erly vented via a back flow or valve or a sufficiently long and nar row exhaust tube Do not leave the fixed siphon at the top of the dewar open Block the opening with the dedicated plug when not pumping helium Do not lead the bo
66. gantry base Cable support chain Secondary rope Pulley for the primary rope Primary rope Lifting motor unit with separate mains power Drum for the primary rope driven by the motor Bowden cable Entry point for the Bowden cable alernatively on the right side Additional pulley if the Bowden cable is entering from the right side Main shaft Push buttons to control the movement Movement control unit inside the feed through filter cabinet Motor control cable Position indicator display of the lifting mechanism 2008 11 11 23 E Hardware and Networking 24 16 Optical fibers of the position indicator sensor in the lifting mecha nism Figure 2 11 Lifting ropes inside the lower back parts of the gantry The following are shown in the back part of the gantry Primary rope 2 Primary rope pulley 3 Bearing for the main shaft 4 Main shaft 3s Secondary rope 2008 11 11 Hardware and Networking Figure 2 12 Safety latches and fiber sensors The dewar cradle has been removed in the figure above There are the fol lowing safety latches and fiber sensors Safety latch Sensor fibers of the safety latch Lever for releasing the latch Sensor fiber detector Guide rails for the cradle wheels Sa pu em 2008 11 11 25 E Hardware and Networking 2 2 Electronics 2 2 1 Main electronics cabinet The main electronics cabinet comprises two MEG subracks one EEG subrack and an MEG preampli
67. gitizer 2 vats kreet eet eee oe eee eke ke 31 Voice Intercom System nuaa eae bawwl eld a dare ra 32 Video monitoring system optional 33 Stim systems optional 000 c cee eee 34 2 4 Workstation hardware 34 2 0 Networking 2 0 nox deoa eg ace eae RD e o de 34 Chapter 3 Software 37 3 1 Data acquisition software LLus 37 Neuromag directory tree 0 ee eee 37 Relevant configuration files 0 00 e ee eeee 38 Commands of the janitor program 00000 cee 39 UNIX commandS site ure RR ERR AIR ROI EE eS de gah ce de pn tase 40 Chapter 4 Preventive Maintenance 43 4 1 Planning preventive maintenance 43 4 2 PM tools and material eeeslees 44 Special tools and material needed in PM 44 4 3 Overview of the PM schedule 45 4 4 Step by step instructions for PM 47 System check module 2 2 exe seeks hstur Roe dg Ss 47 MSR echeckS eut aetema dare eS e pe i E d a tang tang dete Ros aes 48 Warm Up 45279 fca aces ceed oe ee EC E Ee e dti d 48 Electronics module isc 523 20 EE ER ERR ahah ae dee 52 Vacuum pumping of siphons n sssaaa anaana 54 Safety exhaust check 00 ccc cece eee 55 Lifter verification a a ririteht Son Sank ld Roe do caja e 55 Chal GlecKS suom oia ae Fass tuse sca Bar Prata aedes
68. hannel s first in order to release possible trapped magnetic flux and check the tuning curve of the channels which have problems If you have several problematic channels try the effect of switching off the ssp vectors as in some of the cases they can spread the prob lem of one channel to multiple channels Check also from the opera tors when the problem started and had there been any changes to the system connected to that when the problem started If there has been changes to the system check what those were and if noting else helps you could at the later phase of the trouble shooting ask the operator to return the systemto the condition before the problem started If there are only some channels that is problematic try to isolate the prob lem For this example we show how to isolate a problem in a MEG chan nel 0312 by swapping Start from the preamplifier pcb s Start Swapping the SCSI cables of channel 3 and 4 from the connec tros of the preamplifier pcb s as shown in Figure 6 1b and look then the Data Acquisition work station raw display If the problem which was earlier seen in the channel 0312 has now been tranferred to channel 0412 the problem is either the preamplifier pcb of channel 3 or the insert electronics in the dewar By swapping the preamplifier pcb you can check the condition of that If the prob lem is in insert electronics consult the support of MEG about the next actions because the device has to likely be warmed
69. he EEG system is powered On the acquisition workstation open a connection to the janitor eeg module by opening a terminal window and issuing the following commands telnet kaptah2 janitor eeg pass homunculus122 init To read the identification register of the EEG reference board in slot 0 of the EEG preamplifier case issue the readreg eeg 0 Id com mand The command should return a string like 200 Register eeg 0 Id OxA1 2008 11 11 89 Ed System Performance Verification 90 5 where A1 is the revision of the control FPGA chip If not check that the preamplifier power is on the power control cable is connected optical fibres are connected properly at both ends and that the parallel port cable between the EEG optodriver board and the corresponding real time computer is connected If there is still no response check that the EEG preamplifier is cor rectly assembled and that the board ID DIP switches are correctly set Repeat the previous command for slots 1 to 8 or to 16 if there are 128 EEG channels by changing the number in the readreg eeg x Id command where x 1 8 or x 1 16 Exit the janitor eeg by issuing the quit command 7 3 3 Testing with the terminators l Connect the two terminators EL20814K to the EEG input connectors D37 connectors on the side panel of the gantry The two terminators are equivalent Be sure not to use the Calibration adapter EL20844K or EL20867K a
70. he following parts in the gantry seen from the back Preamplifier signal cables Preamplifier control and power cable Control data terminator L siphon equipped with a pressure relief valve Helium gas exhaust tube vacuum insulated Pressure ballast Pressure gauge Safety exhaust duct Vacuum pumpout port 10 Lifting mechanism actuating buttons 11 Lifting mechanism safety latch release lever 12 Lifting mechanism secondary rope pulley CHONAARWNS 2008 11 11 19 E Hardware and Networking 20 13 Optical fiber for the lifting mechanism position sensors 14 Cable support chain to lead the cables from the moving dewar cradle to the gantry base Figure 2 8 Gantry top seen from the front In the figure above the hood has been removed There are the following parts in the gantry seen from the front L siphon plug with the pressure relief valve Pressure gauge Pressure relief valve Liquid helium level gauge unit Control and power cable to the liquid helium level gauge unit Uno oe IPs The L siphon is a vacuum insulated tube leading from the top flange to the lower side of the neck plug for transferring liquid helium into the dewar The L siphon connects to a flexible siphon used for transferring liquid helium from a storage container During the cool down of the sys tem the L siphon is equipped with an extension piece not shown in the figures which guides the initial cold helium flow to the lower parts of the dewar
71. he number of averages to 400 in the averager parameters Start acquisition Start the function generator by issuing the phan 1 command to the collector Set the EEG scale on the raw data display to 10 u V The signal should be buried in noise in unipolar channels in differential channels the amplitude should be the same as in Step 7 Click the Average check box on After 400 averages have been collected stop acquisition and save the average file as Ref_el_no_act Set the scale of the averages display to 0 1 u V and the base line and filter settings as in Step 7 The amplitude of the burst should roughly match the size of the viewport in unipolar channels in differential channels the amplitude should be the same as in Step 7 Change Active ground to On in the Squiddler EEG window Leave Ref Source to Ref el Repeat Step 9 After 400 averages have been collected stop acquisition and save the average file as Re el no act Set the scale baseline and filter of the averages display as in Step 10 The burst should be only barely visible or indistinguishable from noise in unipolar channels in differential channels the amplitude should be the same as in Step 7 7 3 5 Calibration Note This test is performed only if any of the preamplifier boards or any of the EEG signal RF filter boards have been exchanged l Verify the calibration by performing the calibration measurements as instructed in EL20868Y Check the result
72. he response To catch the minimum and maximum automatically use the fit to mamimum feature right click to the signal waveform window and select fit to max amp and then shift left click over the second peak relase mouse button and shift left click over the third peak For further instructions on how to fit the dipoles refer to Source Modelling Software User s Guide Repeat the fitting for all other dipoles 3 Go to Dipole fitting window select all fitted dipoles press the right but ton of the mouse and select Print gt File In the saving options dialog select column titles Cartesian dipole coordi nates distance from origin dipole moment and tab delimited output If you intend to do further processing see next step on a spreadsheet using a PC with a decimal comma system you may also want to select decimal part separated by comma Print out the file and attach it to the phantom test form NM23166Y 4 Compare the localization results with the positions given in Table 1 and check that the peak to peak amplitudes roughly match with the dipole moment selected at step 7 Note that the Source modelling program displays the dipole moments Q as zero to peak values whereas phantom dipole select uses peak to peak values calculate the peak to peak value as the sum of the two peaks min imum and maximum fitted for each dipole Due to the finite precision of the physical dipole length the measured dipole moments typically differ slightly
73. heck also neuro ssp and tm for the binary if you don t find it in neuro bin util 20 Go back to Step 5 and repeat the above steps for gradiometers Delete the previous SSP vectors from the pool and SSP panels and set the meg pick widget names resource to MEG 2 or MEG 3 before doing the PCA for the gradiometers Save the results to files like neuro ssp grad_ssp_upright fif or neuro ssp grad_ssp_supine fif 21 Combine the gradiometer and magnetometer SSP operators in the Source Modelling Program Xfit 22 Open an evoked response all fif file The file has data from all channels both magnetometers and gradiom eters 2008 11 11 81 Ed System Performance Verification 82 23 24 25 26 PAJA Open the Projection window and use File gt Load to load your newly created neuro ssp grad ssp upright fif and neuro ssp mag ssp upright fif Check Allow measurement ID mismatch before loading the above files Select all the SSP vectors in the projection list Click File gt Save and give the file a name like neuro ssp online upright fif or neuro ssp online supine fif Check the file permissions and create a symbolic link as follows cd neuro ssp chmod 644 online upright fif ln s online upright fif online fif Go back to Step 5 and repeat the above with the raw data from the supine position Remember to replace upright with supine in the file names Check the functionality of the
74. heck network connectionsby pinging ping lt hostname gt Connecting and monitoring the servers Servers to connect e collector_fork on the acquisition workstation sinuhe e collector on the RT systems kaptahl and kaptah2 e DSP on all DSP boards sqc01 sqc26 sam01 sam12 scc fungen 1 Establish connection telnet lt hostname gt collector 2 Log in not required for DSPs pass homunculus122 3 Turn on monitoring moni on 4 Turn on state tracking send on 5 Log off quit 2008 11 11 carrer SyStem Performance Verification 7 1 MEG testing 7 1 1 The MEG testing comprises the following phases po Dares pg e MEG channel tuning and rough checking Making the online SSP noise suppression vectors Preliminary visual checking of the MEG channels with the on line noise suppression Noise data measurement Analysis of the nois data Phantom measurement Analysis of phantom data MEG channel tuning amp preliminary system checking It is possible to give the channels a rough check immediately after the cool down The insert temperature will stabilize in 12 24 hours The final tuning can be done after that 1 By manually tuninig check that all channels are working Refer to Chapter 7 6 in the Sensor tuner user s guide document NM21283A Go to the Measure mode and check signals in the Raw data display Ifall channels are working save the tuning parameters Tune the
75. ifier backplane 5 x ine EE ontrol signa EEG preamplifier reference board tisystem EEG optoisolation signal feedthrough EEG preamplifier board filter 4 pcs 16 channels unit 8 pcs 8 channels board H 3 LT EEG Ch 1 64 to Buffered reference i ignal Acquistion Module test oscillator signal ECG0 2 reference el actGND Isolated power EEG EEG preamplifier frontplane 2 pcs PAS feedthrough filter Buffered reference _ 24 V jet T a pe test oscillator signal S re T 6 i 7 Ch 1 32 Unipolar reference el actGND e fl Isolated floating 12V Non isolated 15V Ch 33 60 Unipolar Ch 61 64 Bipolar 30 EEG preamplifier backplane EEG optoisolation signal feedthrough EEG databus termination filter 4 pcs 16 channels unit EEG Ch 65 128 to Empty slot ignal Acquistion Module pee annnnnnnnnncesfonnnnn EEG preamplifier board 8 pcs 8 channels board _ Magnetically shielded room wall EL21014 EEG preamplifier 2 front plane 2 pcs RF feedthrough wall Ch 65 92 Unipolar Ch 93 96 Bipolar 3 Ch 97 124 Unipolar Ch 125 128 Bipolar 3 Parts inside the box ONLY in systems including 128 channels Signal cable between EEG preamplifier backplanes Signal cable between EEG preamplifer frontplanes a Floating Signal cable between electrode interface panel and preamplifier frontpla
76. il off tube vent directly into the room Use silicon hose tube to lead the exhaust vent out from the magnetically shielded room If the hose breaks during transfer replace it with a new hose as soon as possible Do not remove the fixed siphon or the boil off tube from the top plate The opening must be plugged with rubber bungs provided in the Cryogenic Accessories Kit if the fixed siphon or boil off tube are ever removed even for a short amount of time If the safety exhaust rupture membrane accidentally breaks the opening must be plugged with a large rubber bung provided in the Cryogenic Accessories Kit and the membrane replaced Electrical safety All Elekta Neuromage SQUID sensor electronics are operated using low voltage max 15 V 24 V power supplies connected to the mains through an isolation transformer To avoid electrical interference most parts are shielded and grounded class I according to IEC 60601 1 The probe unit is operated inside a magnetically shielded room to avoid elec tromagnetic interference 2008 11 11 3 EH Introduction Subject connections All applied parts of MEG equipment connected to the subject are made of electrically insulating materials only They are classified as body floating BF type according to IEC 60601 1 The helmet shaped sensor assembly is located inside a double walled iso lating fiber reinforced plastic vacuum gap dewar making no electrical contact to the subject The
77. illating between the two values If this happens try manual ranging of the multimeter 6 Switch the multiplexer Mux rotary switch to position V Go through channel selector positions 1 1 4 3 The correct reading is 10 2 0 2 kOhms 2008 11 11 105 Ed System Performance Verification 106 7 Switch the Mux multiplexer rotary switch to position G Go through channel selector positions 1 1 4 3 The correct reading is 10 1 40 1 kOhms 8 Switch the multiplexer Mux rotary switch to position X Go through channel selector positions 1 1 4 3 The correct reading is 10 2 0 2 kOhms in magnetometer channels 1 and open circuit 21 MOhms in gradiometers 2 and 3 9 Switch the multiplexer Mux rotary switch to position N Go through channel selector positions 1 1 4 3 The correct reading is over 10 MOhms in the superconducting state and about 3 MOhms when the system is at room temperature Note The actual resisttance values vary considerably from one FET to another Heater test 1 Connect the multimeter ohms terminal to H Go through heater selector positions 4 The correct reading is 180 50 Ohms if the system is in the superconducting state and 400 1100 Ohms if the system is at room temperature 2 Connect the multimeter ohms terminal to 2X and the common termi nal to 3X Go through heater selector positions 1 4 The correct reading is 180 50 Ohms if the system is in the superconducting state and 40
78. in conjunction with other diagnostic data in neurosurgical planning Elekta Neuromage MEG channels are based on 306 superconducting thin film sensors inside a cryogenic dewar vessel The gantry which supports the dewar the patient bed and the patient chair are operated inside a mag netically shielded room For a block diagram overview of the system see Figure 1 2 MEG electronics unit outside the magnetically shielded room reads out the sensor outputs through the filter unit digitizes the signals and controls the operation of the sensors A data acquisition system col lects and routes the data to the main computer system as well as controls the electronics and data acquisition For an example of the site layout see Figure 1 3 For a schematic diagram of auxiliary electronics see Figure A 5 2008 11 11 9 Introduction 10 Isolation trahsfdrmers Figure 1 2 Block diagram overview of the system MEG Equipment area Analysis Printer PC Visual Magnetically shielded room LAN stimulation Workstation _ 4 option option CCTV option SQUID T E Analysis Inti control A workstation ntercom o OPTION c EEG MHS LAN Data a i control H 5 storage 9 An 5 8 option sti
79. ing slots on the preamplifer motherboard read out and amplify the signals from the sensor elements and control the setting of the operating point 2008 11 11 17 E Hardware and Networking 18 Figure 2 6 Preamplifier top flange The preamplifier top flange consists of the following parts Neck cable assembly connectors under the protective cover acting also as a strain relief Preamplifier connector Power and digital control cable connector Support cage for preamplifiers Dummy motherboard octant 8 There is a dummy textile support assembly connected to octant 8 to keep the helium flow evenly distributed inge Each preamplifier motherboard octant has four slots per board Each slot in the system has a unique address consisting of the board number slot number address numbering starting from 0 Each board number has been set at factory by soldering jumpers on address pads and the address of each slot has been hard wired on the PCB Each octant has 2 x D25 connectors one for the power control cable one for the terminator The control cable can be connected to either of the two D25 connectors associ ated with every motherboard octant and the remaining D25 connector must be terminated with a data terminator block see Figure 2 7 and Figure 2 8 2008 11 11 Hardware and Networking Ji T Wag Wo q L i Figure 2 7 Gantry seen from the back In the figure above the covers have been removed There are t
80. it is advisable to reset the MEG chan nels between the dipoles select Tools gt Reset channels Go back to Step 8 and repeat the measurement for each phantom dipole When all phantom dipoles have been measured stop the measurement and save the file This file contains the responses of all measured dipoles stored as dif ferent categories Data analysis Open a terminal window Depending on the system proceed as follows Systems with Maxshield feedback active compensation on Issue the command Ineuro bin util maxfilter v frame head f filename fif where filename is the name given in previous step This will produce a processed file filename sss fif Systems without MaxShield or feedback active compensation off Issue the command neuro bin util maxfilter nosss f filename fif where filename is the name given in previous step This will produce a processed file filename nosss fif 2 Start the Source Modelling Program Open the processed file saved at previous step and pick up the first of the dipole categories Set the sphere model origin to 0 0 0 in the head coor dinate system and set the baseline from 50 to 0 ms Select accurate coil definition from the DipoleFit Preferences menu If the data file was pro cessed with the nosss option set filter to low pass 35 Hz width 5 Hz Fit single dipoles to the second and third peaks minimum and maximum of 2008 11 11 System Performance Verification 7 t
81. ium gas is odorless and colorless Helium gas is seven times lighter than air ing the relative oxygen content in closed rooms if evaporated rapidly Warning Helium gas is not life supporting it may replace air thus reduc N resulting in a risk of suffocation 2008 11 11 1 Introduction e Boiling point is 4 2 K 269 C or 452 F Density of liquid helium is 0 125 kg liter Liquid helium evaporates very easily latent heat of evaporation is 20 9 kJ kg 2 6 kJ liter e One liter liquid helium corresponds to approximately 750 liters of gas 20 C 101 3 kPa Warning Skin contact with liquid helium or cold gas or cooled objects may cause severe frostbite Flow of cold helium gas makes a very good thermal contact with any surface it passes by unprotected skin cools below freezing point in seconds Dangerous pressures may arise as a result of rapid vaporization inside closed vessels e Liquid helium can cryopump other gases such as nitrogen oxygen and water vapor which solidify at liquid helium temperature This may lead to the blocking of the vents and consequently to the buildup of dangerous pressures in cryogenic vessels 1 2 2 Warnings concerning the dewar and cryogenics Warning The structural integrity of the dewar should not be damaged in any way Absolutely no holes may be drilled on the dewar Warning The dewar must not be opened to atmospheric pressure under any circumstances IN Warnin
82. iven by rope mechanism The rope mechanism is powered by an electric motor located outside of the magnetically shielded room The hinged side panels hide a number of connectors used for connecting EEG electrodes various auxiliary electronics parts and a docking piece that is used to guide the patient bed to the right position The docking piece is not used while measuring in the seated position The gantry has also several removable hatches and covers to access the inside structures for service 2 1 2 Sensor insert and the dewar For the structure of the sensor insert inside the dewar see Figure 2 2 2008 11 11 Hardware and Networking Figure 2 2 Dewar with the insert There are the following parts in the dewar with the insert poc oen ih 9 10 11 12 13 Helmet shaped detector array Wiring unit Sensor adapter boards Wiring unit support rod Neck cable assemblies Neck plug Dewar neck tube Vacuum space with thermal radiation shields Insert top flange with preamplifier motherboards MEG preamplifiers Vacuum pump out port L siphon Helium gas exhaust tube The detector array comprises a helmet shaped support shell equipped with sensor sockets into which the triple sensor elements each having three channels are plugged in Each sensor socket has two connectors The sen 2008 11 11 13 E Hardware and Networking 14 sor socket is mounted on a flexible planar spring There are 102 sensor sockets
83. liquid helium space These comprise 6 conductors per channel plus four conduc tors common to the sensor element 2008 11 11 101 System Performance Verification 13 14 1516 ao N Oo Figure 7 4 Insert top plate with preamplifier numbers indicated The separate conductors for each channel 1 3 are the following e B Bias V Voltage measurement G Voltage measurment ground no current F Flux feedback N Noise cancellation X Extra see below The conductors common for the sensor element are the following GV Common active ground voltage measurement e GI Common active ground current return e H Heater H Heater The extra conductor X in channels 2 and 3 is used for doubling the heater wiring In magnetometer channel 1 the X wire is connected to ground 102 2008 11 11 System Performance Verification 7 7 5 3 Equivalent circuit for the insert To find out the equivalent circuit for the insert SQUID channels see Figure 7 5 Equivalent circuit for the insert Note that the extra conductor X is used for doubling the heater wiring in channels 2 and 3 and in mag netometer channel 1 the X wire is connected to ground 2008 11 11 103 Ed System Performance Verification
84. meas urement settings from the File menu and select the file neuro dacq setup phantom fif Digitize the HPI coil locations on the phantom The cardinal points coincide with the HPI cols Compare the digitized distances of the coils with the actual values to verify correct digitizer operation Errors should be max 1 0 mm Put the phantom into the sensor helmet of the probe unit and push against the helmet The front coil should point somewhat upwards Connect the 32 pair cable between the phantom excitation multiplexer and the phantom Connect the separate HPI coil set connector of the phantom to the connector of the HPI cable connected to the HPI outlet undernearth the side cover of the gantry Start the measurement Do the head position measurement in the usual way as described in the Data acquisition User s Manual Start the phantom dipole control utility program by double clicking it s icon in the MEG Maintenance folder Activate dipole 1 by entering its number to the phantom dipole control dialogue and click Do it 2008 11 11 85 Ed System Performance Verification 86 7 2 2 10 11 Use the default 1000 nAm dipole moment Check that the MEG signals sine wave cycles and triggers appear on the raw data display Activate Average Wait until the limit of 100 epochs is reached Advance the dipole number in the phantom dipole control dialogue by one and click Do it again When measuring many dipoles
85. mulators Helium a g options u level 2 Acquisition Le contro E workstation HPI me control H 3D digitizer J cabinet PC NC I Electr Acquisition Q Patient preparation and head digitization Feedthrough filter o pos i fn il J EN Stimulup Stimulus control gabinet T d boa MSR h eg HPI chair MSR F 35 equipment Video area projector Figure 1 3 Example of the site layout 2008 11 11 cHaprer2 Hardware and Networking 2 1 Probe unit 2 1 1 Introduction The core component of the Elekta Neuromag system is the probe unit It is located inside a magnetically shielded room MSR that reduces the environmental magnetic noise The probe unit comprises a sensor insert with an array of 306 magnetic field sensors inside a cryogenic dewar and a supporting gantry see Figure 2 1 Figure 2 1 Probe unit The probe unit consists of the following parts 1 Dewar with a magnetometer insert containing 306 magnetic sensors and first stage preamplifiers 2008 11 11 11 E Hardware and Networking 12 2 Gantry base stationary part 3 Gantry cradle moving part holding the dewar 4 Side panel 5 Removable hood for accessing the dewar top part and MEG preampli fiers
86. ne applied part Grounded normal Control power cable between preamplifier unit and control feedthrough filter electronics Power cable control between feedthrough filter and EEG signal feedthrough filters 1 2 3 4 Signal cable between preamplifier and signal feedthrough filter unit 5 6 7 Power cable between isolated power supply and EEG signal feedthrough filters Figure 2 17 Block diagram of the EEG electronics 2 3 Auxiliary hardware modules 2 3 1 Phantom A phantom is provided for checking the system performance see Figure 2 18 It contains 32 artificial dipoles and four fixed head position indicator coils The phantom is based on the mathematical fact that an 2008 11 11 Hardware and Networking B equilateral triangular line current produces equivalent magnetic field dis tribution to that of a tangential current dipole in a spherical conductor provided that the vertex of the triangle and the origin of the conducting sphere coincide The phantom dipoles are energized using an internal sig nal generator which also feeds the HPI coils An external multiplexer box is used to connect the signal to the individual dipoles Only one dipole can be activated at a time HPI coil left Connector panel under the gantry cover Phantom HPI cable Pin arrangement Phantom cable dipole 1 dipole 2 dipole 31 dipole 32 Dipole multiplexer Figure 2 18 Phantom 2 3 2 HPI and 3D digitizer
87. net Tighten screws and fasten cables N A Check connectors and door mecha N A nisms Stimulus electronics cabinet Verify that indicator lights are OK N A Vacuum clean stimulus electronics N A cabinet Tighten screws and fasten cables N A Check connectors and door mecha N A nisms Check for inappropriate connec N A tions of equipment and correct if necessary 2008 05 09 65 H Maintenance Checklists 5 7 Computer system Table 5 7 Checklist for the computer system OK NOK Action Measure Check and note software versions upgrade if necessary N A N A N A Clean the keyboard Check and clean the mouse Remove dust and fingerprints from the screen of the monitors N A N A Check the fans of the workstations Vacuum clean the inner parts of the printer Clean printer according to the N A printer manual Check cabling for inappropriately N A terminated LAN connectors or SCSI cables and correct if neces sary Do an overall visual inspection of N A the computer system hardware installation 5 8 HPI system and 3D digitzer Table 5 8 Checklist for the HPI system and 3D digitizer Measure OK NOK Check the HPI coils and cables Check the cables of the 3D digi N A tizer Check the function of the 3D digi N A tizer and record the accuracy Clean the 3D digitizer chair N A Clean the
88. ng of the system takes 3 4 hours 2 Interim PM e Dayl System check takes normally about 1 3 hour s Fixing of the possible problems notified by the customer takes 2 3 hours Vacuum pumping of siphons takes 3 4 hours this can be done par allel to some of the other steps e Day2 46 MSR check takes an hour Electronics check takes an hour Chair check takes an hour 2008 11 11 Preventive Maintenance n Bedcheck takes half an hour Lifting unit verification takes half an hour Final testing of the system takes 3 4 hours 3 Lifter PM Day 1 System check takes 1 3 hour s Fixing of the possible problems notified by the customer takes 2 3 hours Lifting unit maintenance takes 2 3 hours Lifting unit verification takes half an hour 4 4 Step by step instructions for PM The individual preventive maintenance plans are built from so called modules This chapter provides the step by step instructions for the mod ules in different preventive maintenance plans 4 4 1 System check module l 2 Save the current set up in the Squiddler program as a reference Check that the acquisition is generally working and the tuning is OK Tune the channels if needed If the channels have been re tuned save a new copy of the set up Record 2 minutes of empty room data either seated or supine Collect new data for 120 seconds sampling rate 1000 Hz filter 300 Hz Measure autotuner average white nois
89. ng toubleshooting 75 Premature end of acquisition 0 0 05 75 Acquisition does not start 20000 76 Chapter 7 System Performance Verification 77 IA MEG t slini 14222 Gucsisen cae teres Ca Eae aca us 77 MEG channel tuning amp preliminary system checking 77 Making online SSP vectors 000e eee ee eee 78 MEG noise measurements 0000 ee eee eee 83 MEG noise data analysis 2 ovscie cee Eee pSPAPETU 83 7 2 Phantom test witnescyeorsardad Vaca ick ceti RE eriared au 85 Measure melli srra taaa ari bias Bast un Ure ated de O ntt ed 85 Data ANY SIS s ect ead so dete Du pte dE o deae 86 7 3 EEG testin ade nb Rara ah RR CR RR RATER CELA C dn 89 Required items s bah orsa c eve oe ure seins Ble m Eee va RES 89 Preamplifier control check 00000 cece eee 89 Testing with the terminators 00 eee eee eeee 90 Common mode rejection and active ground test 92 Calibration SNR Cp 94 Noise measurement 000 cece eee eee 95 7 4 Noise measurement testing ssee 98 7 5 Insert wiring test cri serena hee ee Phe EAR 99 Equipment needed x xci bxixPthEEEa 99 Channel numbering and conductor naming scheme 101 Equivalent circuit for the insert 00000005 103 Test proced ra MEE 105 Testing for cross talk between channels 106 Helium level probe and thermometers
90. not seen check whether the response can be seen in some other channel in that case signal cables have been swapped or preamplifier board addresses do not correspond to physi cal locations 7 3 4 Common mode rejection and active ground test Note This test is performed only if the reference board has been exchanged l Connect the test signal adapter calibration adapter EL20844K or EL20867K to the EEG inputs on the side panel of the gantry Note that the D37 connectors are not equal the connector with the switch must be connected to EEG connector EEG1 EEG32 Connect the input cable of the test signal adapter to the HPI connector found on the right hand side panel of the Vectorview gantry Make sure that the switch on the test signal adapter is in the Test posi tion Open a connection to the collector server by double clicking the Col lector icon in the Maintenance toolbox Enter the pass homunculus122 password Set the function generator amplitude by issuing the vara phan tomAmp 1 0 command to the collector note the case This corresponds roughly to a 1 Vpp signal to the calibration adapter and thus 1 mVpp to the EEG amplifier Set up the on line averager as follows 2008 11 11 System Performance Verification 7 Define event 1 Event channel STI201 Old state 0 65535 New state 32 65535 Make sure that STI201 is selected in the acquisition setup activate cat egory 1 by performing the following ta
91. o 2 H o o SS 3 1G o 3 1V oO O Em 3Gl o o 3GV o o SS 3 2G Oo o 3 2 V o o EL 3 3F o O0 3 3B Oo O0 SS 3 3 N o o 3 3 X o oO 44 F Oo o 4 1B 9 8 4 1 N o o 41X o O0 H 4 2 F o o 4 2 B o o 4 2N Oo o 4 2X oO ERA 43G oO o 4 3V oO O SS 4H o o 4 H o o EX o EX o o SS 15VA2 o o 415VA2 o o AGND o o AGND o o S55 DGND o o 6VD Oo O N C Oo o N C Oo O BM o BM o o SS TD o o TD o o e CLK o O0 CLK oO O E N C oO o N C o o SS N C o o N C o Oo Figure 7 6 Pinout of the test adapter 7 5 6 Helium level probe and thermometers For the equivalent circuit for the helium level probe and the two thermom eters see Figure 7 7 Equivalent circuit for the liquid helium level probe Rp and the thermometers Ru 2008 11 11 107 Ed System Performance Verification 108 Av 1 1 B I4 Aw 1 1 X l e 1 1 V V4 Rp Rw 1 1 G V gt y 1 1 F I 1 1 N I CEN 2 1 B l Pw 24 V V4 Ry Aw 24 G V a 24 F I Aw 2 2 B l 2 2 V V4 Ro Aw 2 2 G V 2 2 F I Figure 7 7 Equivalent circuit for the liquid helium level probe Rp and the thermometers R 2 Nominal values for the resistors are Rw
92. of the commonly used commands are ABOU Displays information about the server BIAS Sets the bias current BIAS lt ch gt value CONFIG Gets the current configuration in other words the contents of the con fig file CONFIG device CLIS Displays a list of all the clients e DUMP Dumps the state into tmp janitor dump DUMP initial wanted current GATE Sets the gate voltage GATE lt ch gt value HEAT Heats one channel HEAT ch name HELIUM Measures the liquid helium level HELIUM nosync HELP Displays a list of all commands HELP topic is more specific 2008 11 11 39 H Software 40 INIT Initializes all devices and the janitor service LIST Lists some known objects LIST units class LOAD Loads a state from a file LOAD file name gt LOOP Closes or opens a flux locked loop LOOP lt ch gt C O MONI Shows starts or stops monitoring MONI OFF ON NAME Sets or asks your name NAME program name gt OFFSET Sets the offset voltage OFFSET lt ch gt value PASS homunculus122 Enters the login password QUIT Quits from the service and closes the connection READ Reads the state of an item READ unit item force READREG Reads the contents of a register READREG device slot register SET Sets the value of an item SET unit item value STATE Asks the state of
93. on 3D 64 channels Bus 64channels Bus digitizer EEG EEG Feedthrough t g net Electrode lt Preamplifier x filter amp opto RZ electronics isolation Bus Control Feedthrough Riber optie link Bus um filter Figure 2 14 Block diagram of the electronics 2 2 2 MEG electronics For the MEG electronics components see Figure 2 15 The MEG elec tronics can be divided in the following blocks e Preamplifiers inside the probe unit e Feed through RF filters inside the filter unit e Control power feed through filter inside the filter unit Mainelectronics racks and real time data acquisition computers in the VME rack inside the main elecronics cabinet 2008 11 11 27 E Hardware and Networking Magnetically shielded room LHe ER Probe unit gauge separate box unit MEG Feed preamp through filter local Control display 4 unit Aux E electr MEG panel EA through pem filter MSR y feed through Lifting unit control Filter Main electronics unit cabinet Signal and control cables X unit N A Main MEG electronics rack LHe S Main EEG electronics rack Preamplifier power supply unit Switch RT computer VME rack Mains distribution unit Figure 2 15 MEG electronics components 2 2 3 EEG electronics For the EEG electronics components see Figure 2 16 For a
94. on of the 3D digitizer using for example graph paper and record the accuracy Clean the 3D digitizer and chair Clean the goggles if necessary and check for wear Helium level gauge Check the functioning of the local gauge on the gantry Intercom and video if installed Check the intercom system speakers and microphone Run an empty room measurement using the intercom during the mea surement and check that there 1s no increase in the noise Check the video monitor system Adjust the TV monitor for optimal contrast and brightness Clean the TV camera lens and monitor screen 2008 11 11 53 g Preventive Maintenance 4 4 5 Vacuum pumping of siphons 54 a 1 Fixed siphon Remove the fixed siphon from the probe unit Plug the opening for the fixed siphon on the top plate by using a rub ber cork included in the cryo kit Warm up and dry the siphon Check the fixed siphon for wear Check the o ring in the vacuum close valve by opening the valve counter clockwise and replace the o ring if needed Screw in the siphon vacuum close valve Re evacuate the fixed siphon vacuum a Connect a pumping line to the vacuum pump out port and open the vacuum valve by turning the screw counter clockwise Be careful not to unscrew the screw completely b The residual vacuum pressure must be below 5 10 2 mbar no flow condition Tighten the pump out port screw Replace the cotton in
95. ot ground the subject to actual ground Do not place con ducting grounded objects so the that someone might touch them while connected to the equipment 2008 11 11 1 2 5 AN 1 3 1 3 1 Introduction Auxiliary user supplied equipment To avoid risk of electrical shock equipment supplied by the user and con nected to humans must comply with isolation requirements similar to or better than this system For connection of these devices isolated and fil tered power outlets are provided in the stimulus cabinet Maximum cur rent available is 10 A total Warning The applied parts of user supplied equipment must be of BF type or cardiac floating CF type and they must fulfill the norms of IEC 60601 1 for medical electrical equipment Although the individual devices fulfill the leakage current requirements set forth in standards a possible hazard exists caused by the summation of leakage currents when several pieces of equipment are interconnected Also other equipment connected to the same stimulus trigger interface unit must fulfill the requirements of IEC 60601 1 The power outlets in the electronics and stimulator cabinets connected to the isolation transformers if installed may only be used for the connec tion of system components or equipment needed during service and main tenance operations or for compatible user supplied auxiliary equipment stimulus cabinet Mechanical safety The weight of the fully loaded dew
96. pass band band pass 0 1 100 pass type function square sqr base start 0 stop 60 no baseline off sub fsub root ssqrt This setup calculates the rms value of the noise in the 0 1 100 Hz band In the command line on the graph main window enter the 1oad print rms lsp command where is the directory path speci fied in Section 7 3 1 4 Open the EEG noise2 fif file Set the cursor using the rightmost mouse button to any point on the trace Enter the print rms rms txt command This lists the rms amplitudes of each channel in units of u Vrms to the rms txt file prepend appropriate directory path Open a terminal window and enter the following commands cd directory path given above more rms txt The maximum value is 0 4 u Vrms 5 This step is not performed if Step 4 has been skipped If necessary calculate the spectra and investigate them to find a reason for possible excessive noise Calculate the spectra as follows In Graph issue the require average command Load the eeg spectra setup setup where is the directory path specified in Section 7 3 1 This setup creates the following wid gets to the Control panel 96 2008 11 11 System Performance Verification 7 eeg EEG win start 0 end 4 translate spectra fft size 2048 fft step 1024 power n averages 1 window han ning average start 0 end 300 do average root function ssqrt Set the parameters to
97. plate may get cooler than under normal conditions resulting in condensation of water Water in the top plate connector may cause leakage currents and polariza tion voltages between the pins of the connector This may lead to a wide variety of disturbances observed in the normal measurement mode To identify the problem caused by moisture check whether there is water condensing on the top plate in the connector area and check the flux vs current characteristics where the following phenomena may be observed one of several The flux vs current characteristics gets skewed see Figure 6 2 Flux vs current characteristics gets skewed if there is leakage due to excess water e The amplitude of the flux vs current characteristics may get smaller e The amount of flux caused by certain excitation may be lower than normally less flux quanta When observing the flux vs current characteristics in the xy mode _ the trace is substantially phase shifted see Figure 6 2 Flux vs current characteristics gets skewed if there is leakage due to excess water Figure 6 2 Flux vs current characteristics gets notably skewed if there is leakage due to excess water 2008 11 11 Troubleshooting g 6 2 5 6 2 6 Helium boiloff 1 Check the log history to determine whether the He dewar has been filled appropriately 2 Check that the surface of the dewar or siphons are not cold to the touch or have any ice formed on the surfaces
98. plode from the Edit menu Now the vectors can be selected individually by clicking them Start with PCA v1 as it one corresponding to the largest singular value and then click the right arrow The right arrow copies the vector to the SSP vector panel The sup pressor automatically turns on once there is at least one vector assigned to it You should see a decreasing noise level on the display as more vectors are added Delete the vectors you do not need from the vector pool then click File gt Save and give the file a name like neuro ssp mag ssp upright fif or 2008 11 11 System Performance Verification ES neuro ssp mag ssp supine fif depending on wheather the loaded file was upright or supine Generally five vectors are enough for magnetometers and two to three for gradiometers If more vectors are used the raw data appears better On the other hand the bigger number of vectors also unnecessarily attenuate brain signals as well and complicate analysis 18 Select a short time span less than one second of raw data on the dis play with the right mouse button Then select Make evoked file in the File menu of the Graph window Give the file a name like neuro ssp mag names fif 19 Open a terminal window Run cd neuro ssp cont neuro bin util add proj namelist f cont mag names fif mag ssp upright fif This step adds the channel names to the SSP vectors This program is missing from older software distributions C
99. ptly which makes the pressure rise rapidly and the relief capacity of the primary valve exceed Conse quently the rupturing membrane acting as a secondary safety valve gets broken This results in letting the gas escape via the safety duct to the out side of the building A pressure gauge on top of the dewar shows the inter nal pressure At normal pressure the dewar inner parts are virtually at athmospheric pressure however during cooldown warmup or liquid helium fill up the pressure may rise because of rapid evaporation of helium For the inner parts of the dewar see Figure 2 7 and Figure 2 8 To prevent thermo acoustic oscillations also known as Tachonics oscillations in the exhaust line which could lead to markedly increased liquid helium boil off the exhaust line is equipped with a pressure ballast At some sites the exhaust system may contain an external helium boil off valve unit It is used for connecting the dewar exhaust hose and storage 2008 11 11 21 E Hardware and Networking 22 2 1 4 dewar exhaust hose to a helium boil off feed through tube that is con nected to a check valve This is may be connected via a heat exchanger to a gas meter if installed Lifting mechanism The dewar cradle is moved between the supine and seated positions by using a rope mechanism The pulley connected to the main shaft is pow ered by a motor outside the room driving the primary rope A secondary rope connected to the dewar c
100. r wear Replace if necessary 4 Check the connection of the safety exhaust duct to the duct outside the room Lifter verification l 2 Perform an overall check of the mechanical parts of the gantry Drive the gantry up and down a few times and make sure the indicator LEDs operate normally showing the OK green LED lit in the supine and seated measurement positions and that the red fault LED does not come on at any time Check the ropes for wear and replace if necessary The ropes must be replaced every 5 years Chair checks l 2 Perform an overall check of the mechanical parts of the chair Check that the chair moves up and down without problems 2008 11 11 55 g Preventive Maintenance 3 Turn the chair over on its left side use cushioning material underneath 56 to avoid scratching and inspect the hydraulics for leaks Check the water reservoir and fill up if needed Return the chair to the normal position Check that the chair wheels roll free Check the locking of the chair wheels Check that the chair remains at a fixed height supporting a person for at least 15 minutes 4 4 9 Cleaning 1 1 Check that no extra items have been glued or fixed to the surface of the gantry or the chair Remove if necessary Dust the gantry and chair surfaces with a damp cloth Alcohol may be used if necessary to remove fingerprints and tape glue residues for instance 4 4 10 Cool down
101. radle winds or unwinds from the main shaft as the cradle moves The pulley shaft combination provides gearing to reduce the tension of the primary rope The secondary rope forms a loop firmly attached at the middle to the cradle effectively forming two inde pendent secondary ropes At the measurement positions the weight of the cradle is resting on end stoppers supine position or on two safety latches seated position so that at secured measurement position there is no ten sion on the ropes at all The latches are automaticlly engaged by a spring when the hole in the cradle passes by the latch To monitor the status and to indicate a safe measurement position the system has been equipped with four optical fibre sensors control electronics and an indicator display on the wall of the magnetically shielded room The detectors based on sensing a refelection from a surface sense the dewar uppermost and low ermost positions the latch engagement and the secondary rope tension For the lifting mechanism see Figure 2 10 For details of the lifting mech anism see Figure 2 7 Figure 2 8 Figure 2 11 and Figure 2 12 2008 11 11 Hardware and Networking Figure 2 10 Lifting mechanism The lifting mechanism consists of the following parts CON AKRARWNS ee Ol ed nABRWNR Oo Dewar cradle moving on wheels along rails inside the
102. ram will apply the selected 5 vectors to the raw data You can check the operation of the vectors by selecting On and Off from SSP Dialog 2008 11 11 System Performance Verification ES 16 Write average X Y into the command line where X and Y are the same start and stop times of the good signal After Y the signal must be good for 10 seconds 17 Check that the histo 1sp file is available 18 Execute the require histo command in the directory where histo lsp is located 19 Command load histogram calculating program for the Graph Execute the histo 1 10 command to calculate the average noise from 1Hz to 10Hz Save results by save result name of the file 20 Repeat the above for the frequency range 60 70Hz 60Hz 70 80Hz 21 Repeat the whole noise analysis for the gradiometers Write MEG 2 and MEG 3 into the names in the pick widget 7 5 Insert wiring test 7 5 1 Equipment needed Wring tester NM20413K See Figure 7 1 Insert wiring tester e Ribbon cable NM20181J 64 pin with DIN 41612 8 Euro connec tors 2pcs See Figure 7 2 Ribbon test cable 2 pcs Test adapter EL201810 See Figure 7 3 Test adapter Digital multimeter Recommended models Fluke 77 Fluke 73 or Fluke 79 Banana plug 4 mm test leads 2 pcs 2008 11 11 99 100 System Performance Verification Multiplexer selector Heater et selector SWIG rotary switch FET pushbutton
103. ration Note When the helium level meter s local display reading is 096 there is still approximately 15 liters of helium left in the dewar Step by step instructions for calibration 1 Open the top covers of the probe unit to access the helium level meter board and the back cover of the probe unit Figure B 1 2 Switch off the power from the preamplifiers from the electronics cabi net 3 Open the cover of the helium level meter board in the gantry 4 Replace the helium level meter adapter board in Slot 27 on the top of the dewar with the calibration adapter 2008 11 11 121 B Fine calibrations of the He level meter 5 Turn the switch of the calibration adapter to the actual position 6 Switch on the power to the preamplifiers from the electronics cabinet Note Follow the recommended power on sequence 7 Double click the janitor icon in the Maintenance toolbox to start a ses sion with the janitor program and type pass homonculus122 8 Initialize the electronics with the init command 9 Perform the readreg meg 249 Id command 10 Janitor replies with a hexadecimal number 0xA4 If you get an error message the program cannot contact the board In that case check the cabling 11 Switch on the helium level meter s local display Figure B 2 on the side of the gantry and check that the lowest LED indicating an empty dewar is on 12 Switch off the helium level meter s local display 13 Perform the helium
104. rt 1 Triple sensor elements 2008 11 11 15 E Hardware and Networking 16 DUI Lael cell Sensor element connectors Wiring unit shell Sealing ring Textile support for cable bundles Support ring Preamplifier motherboards made of eight sectors octants Figure 2 5 Middle section of the insert The middle section of the insert consists of the following parts ae ee NO Sensor adapter boards Neck cable connectors Neck cable assemblies inside textile supports Wiring unit support rod Funnel to match the end of the L siphon extension during cooldown to direct the helium stream to the lowest parts of the insert Connector for the liquid helium level probe Liquid helium level probe The sensor adapter boards see Figure 2 3 and Figure 2 5 contain the feedback resistors passive radio frequency RF filtering components and the field effect transistors FETs for the amplifier noise cancellation Each sensor adapter is connected to four sensor sockets Therefore each sensor adapter has 12 channels There are 26 sensor adapter boards plus one auxiliary board for the liquid helium level sensor and the thermometer resistors Each sensor adapter board connects to a corresponding pream plifier also 12 channels 2008 11 11 Hardware and Networking B The cable assemblies connecting the room temperature parts and the sen sor adapter boards see Figure 2 4 are made of resistive wires to mini mize th
105. s by calculating the difference of the sine wave burst maximum and minimum and comparing it with the real supplied preamplifier input voltage as described in the calibration instructions 2008 11 11 System Performance Verification ES 7 3 6 Noise measurement Note This test is performed only if any of the preamplifier boards or any of the EEG signal RF filter boards have been exchanged l In the Squiddler EEG set the parameters as follows Gain of all channels 5000 HPF 0 03 Hz Ref Source Ref el Active ground On Set the sampling frequency to 600 Hz high pass filter to 0 1 Hz and disable the averager by deactivating the category 1 Disconnect the cable of the calibration adapter connected to the HPI connector at the gantry side panel This is very important as this cable ties the isolated ground to the real ground and thus may cause excessive line frequency artefact under certain conditions Keep also the cable off the floor Start acquisition and collect 1 minute of raw data Save the file as EEG noise Use the following utility program to downsample the data by a factor of two neuro bin util fiff downsample 2 EEG noise fif EEG noise2 fif Start the Graph program Load the eeg rms setup settings where is the directory path specified in Section 7 3 1 The setup creates the following widgets to the Control panel display 2008 11 11 95 Ed System Performance Verification eeg EEG eeg filter
106. sks Set 1 as the reference event Disable rejection by setting 1 to the MEG Amplitude field Set the number of averages to 100 Make sure that Ref Source is set to Iso ground and Active ground to Off in the Squiddler EEG window 5 Start the acquisition hit GO 6 Start the function generator by issuing the phan 1 command to the collector Set the EEG scale on the raw data display to 500 pV Check that the function generator trigger pulses appear on STIO16 on the raw data display and that a clean burst of two sine wave cycles appears on all the channels in phase The burst should just fit the dis play Click the Average check box on 7 After 100 averages have been collected stop acquisition and save the average file as Isognd no act Select data plotter menu item File load layout vv eeg all test lout and set the scale of the averages display parameters as follows Process Scales time 50 200 ms Process Scales EEG amplitude 500 500 uV Process Baselines baseline 50 20 ms use baseline Process Filter low pass filter 40 Hz width 20 Hz Check that the burst polarity is the same on all EEG channels and that its amplitude roughly matches the size of the viewport the space reserved for display of each channel trace 8 Change Ref Source to Ref el in the Squiddler EEG window 2008 11 11 93 Ed System Performance Verification 94 10 11 12 13 Leave Active ground to Off Set t
107. ss fiffile 2 Perform the noise analysis on the processed file according to NM20654Y factory test or NM20846A installation test with the Maxshield active feedback on 3 Start the Graph program 4 Load magnetometer noise setup from File Load settings 5 Open the just measured raw data 6 Open the Graph control panel by clicking Displays gt Control Panel 7 Select all magnetometers by writing MEG 1 to the names in the Pick widget 8 Open Resources and set the display to the Superpose mode 9 Click Autoscale in the Display Scale window and set the offset to Zero 10 Scroll the file and check that all channels are in the working area in other words check that signals do not go to the limit flat 2008 11 11 83 Ed System Performance Verification 84 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Note the start and stop time for the good signal Write pca on widget meg X Y to the command line X is the start time and Y is the stop time for the good signal To execute press Enter Select SSP Dialog from the Commands menu Select Add PCA fields 8 vectors On the left side window there is an 8 102 matrix Select the matrix and execute the explode command from the SSP Dialog window The matrix explodes into 8 vectors Select 5 vectors from the top and activate them with the right arrow button Vectors will be copied to the right
108. such as tools steel buttons magnetic electrodes or hairpins are brought inside the hel met against the surface flux trapping may occur Flux may become trapped into the SQUID if a current surge of big enough amplitude flows through the SQUID Trapped magnetic flux always reduces the critical currents of the SQUID This is manifested as reduced modulation depth of the flux vs current characteristics The point of operation also changes as a result the SQUID feedback loop may not lock any more after flux trapping or at least the noise level is greatly increased In case of a sudden increase in noise and loss of the ability to lock the feedback loop flux should be checked If the maximum modulation depth drops below 25 of its original value mea sured during installation associated with a shift of the offset flux trap ping is likely Carefully check the conditions under which flux trapping 2008 11 11 73 g Troubleshooting 6 2 4 74 has occured so that further flux trapping can be avoided Record and save the modulation depths of all the channels for future reference Excess moisture on the top plate In humid conditions condensation of water on top of the dewar may occur Therefore the air in the magnetically shielded room must be condi tioned to have a dew point which is at least 5 degrees C below room tem perature A recommended room temperature is 20 24 degrees C with 50 relative humidity During helium transfer the top
109. t this step Start the acquisition program by double clicking its icon in the Neuro mag toolbox Invoke Squiddler EEG EEG control program from the Tools menu of the Acquisition control program Select Initialize electronics from the Commands menu of the EEG control so that the EEG electronics goes into its default mode The per channel parameters should now be as follows Active Off Gain 5000 for unipolar channels typically EEG1 EEG60 and EEG65 EEG128 For differential channels typically EEG61 EEG64 the gain is 500 or 150 depending on the configuration nothing is shown in the ALL mode HPF 0 1 Hz Test Osc input Off Test Osc input Off The common parameters should now be as follows Ref Source Ref Electrode 2008 11 11 System Performance Verification 7 Ref Test Osc Off Active ground Off depending on the configuration this may also be On but switch it to Off Test Osc Off Test Osc Amp 490 Vpp Zel 1 M Ohms Test Osc Freq 20 Hz 4 Select all EEG and MEG channels and set a 600 Hz sampling rate 200 Hz low pass and 0 1 Hz high pass in the Acquisition menu of the Acquisition control program and start acquisition hit GO Noise level check 1 Select the first EEG channel set in the raw data display 2 Setthe EEG scale to 20 Volts this may vary slightly according to local line noise level 3 Observe the noise level If there are channels whose noise level exceeds that of other
110. tems e neuro dacg logs log files for the acquisition system neuro dacg tuning SQUID tuning parameter files and various configuration files for the automatic tuner program Relevant configuration files The following configuration files are stored on the acquisition worksta tion in the neuro dacq setup directory janitor config MEG system janitor configuration janitor eeg config EEG system janitor configuration megacq defs local acquisition user interface configuration param eter values 2008 11 11 Software H megacq vars local acquisition user interface configuration param eter types The following configuration files are stored on the acquisition worksta tion in the neuro dacq setup collector conf directory e collector cmd collector server channel assignment collector defs collector server parameter values collector cal ccalibration coefficients collector pos MEG sensor position info collector para collector server parameters The following configuration file is stored on the acquisition workstation in the neuro ssp directory online supine fif On line SSP operator online upright fif On line SSP operator 3 1 3 Commands of the janitor program AN Warning Do not change anything unless you are quite certain about the changes needed The MEG and EEG servers are controlled through the janitor and janitor eeg programs Some
111. the parameters STATE unit lt unit gt lt item gt STATE device lt name gt STATUS Gets the device or slot status STATUS device lt devname gt STATUS slot lt devname gt slot STRUCTURE Gets the hardware structure information STRUCTURE SYNC Synchronizes the registers in the electronics TEST Tests the given device TEST lt device gt lt slot number gt lt of trials gt UNIX commands The following are the most commonly used UNIX commands man Display the manual page for a command man lt command gt id Display the login and group names and numbers of the current user Is 2008 11 11 Software H Displays the contents of a directory Is 1 will display the owners groups file sizes and last modification dates of all files in a directory e cp Copy a file from a directory to another cp path1 lt path2 gt mv To move a file from one directory to another mv lt path1 gt lt path2 gt m To delete a file rm options filename e ps Display a list of processes running on the system kill Terminate a process kill options process id chmod Sets the permissions to a file For example chmod ug w o rw jani tor powerup enables the owner u and group g to write w to file janitor powerup and disables both read r and write w access for users other than the owner of the file and the members of the associ ated group 2008 11 11 41 H Software 4
112. tion Measure OK NOK Re evacuate the fixed siphon vac cum Replace the filter at the end of the N A fixed siphon Check and grease slightly the O N A ring on the fixed siphon feed through Transfer siphon Check the siphon for wear N A Interview end users for abnormally N A high transfer losses or cold siphon surface during the transfer Re evacuate the siphon vacuum 5 Pa Grease slightly the O ring on the N A nozzle of the siphon Exhaust system Make a note of the dewar pressure 2 kPa 0 02 while in normal operating mode bar Warmup and dry exhaust tube if N A necessary Re evacuate the exhaust tube vac 5 Pa uum Grease slightly the O ring on the N A nozzle of the exhaust tube feed through Check the silicon hose and all hose N A connections for wear Check the exhaust system outside N A the room Safety exhaust system Verify that the safety relief valve N A opens easily by prying it gently with your fingers 62 2008 05 09 Maintenance Checklists H Table 5 4 Checklist for cryogenics Action Remove the safety exhaust duct from the top of the probe unit and verify that the rupture foil unit is not damaged Measure N A Limit OK NOK Put the duct back and check the duct and joints for wear N A Check the saety exhaust duct out side the room N A 2008 05 09
113. up and the prob lem isolated with the insert wiring tester If the problem does not transfer to the channel 0412 the problem is after the preamplifier pcb looking the signal route towards the real time computers in the SCSi cables or filter unit pcb or SQUID con troller pcb In order to study that continue with the next swap Swap the cables between the filter unit pcb s and SQUID controller pcb s of channels 3 and 4 If the problem does not change to channel 0412 the problem is in SCSI cable or squid control pcb If the problem transferred to 0412 the fault is in filter unit pcb Isolating the problem of MEG channel when the device has been warmed up The insert wiring tester is plugged in in place of the preamp 3 and will isolate problems of the insert electronics see more info about that in the chapter instructing the use of the insert wirring tester 2008 11 11 Troubleshooting g a Preamplifier pcb Filter pcb SQUID contr pcb 3 3 3 Insert Switch electronics PPS 4 4 4 b Preamplifier pcb Filter pcb SQUID contr pcb 7 i i m Insert electronics Switch i i E C Preamplifier pcb Filter pcb SQUID contr pcb 3 3 3 p Insert Switch electronics TA 4 4 mo is Figure 6 1 MEG signalling simplified view 2008 11 11 71
114. use disturbances Have the room cleaned up Note If a vacuum cleaner or any other magnetic equipment must be used during the clean up do it when the system has been warmed up 4 4 3 Warm up 1 Remove the top and the back covers of the probe unit 2 Install the fixed siphon extension 3 Connect a fixed siphon end flange adapter to the fixed siphon 4 Connect a 7 mm silicone hose to the fixed adapter and lead the hose out of the shielded room note in this phase the fixed siphon is used as 2008 11 11 Preventive Maintenance n an extra exhaust line 5 Connect the multimeter to the PT100 resistor in the helium level aux iliary box 6 Remove the blind flange of the dewar vacuum port and attach the vac uum valve adapter on the vacuum port with the KF25 vacuum flange to the 7 mm silicone hose adapter with the clean silicone hose Note 1 If the silicon hose has some dirt inside this might contaminate the vacuum space and could cause artifacts in the MEG measurements Note 2 Do not open the vacuum valve of the dewar at this point 7 To switch on heaters with the janitor perform the following commands a Save janitor config file cp p neuro dacq setup janitor config neuro dacq setup janitor con fig ok b Copy warmup file to janitor file cp p neuro dacq setup janitor config warmup neuro dacq setup jani tor config c Select RestartAcqPrograms with b option in Maintenance window d Connect to janitor as root
115. wo UNIX worksta tions one for performing and controlling measurements and on line pro cessing acquisition workstation and the other for off line analysis of data analysis workstation Additional mass storage and output devices can be added to the system according to need 2 5 Networking WS sinuhe 10 100 BaseTX For an overview of the network see Figure 2 23 Data Acquisition Cabinet 10BaseTX Real time unit Media kaptahl Converter 1000 BaseTX or Switch Optical fibre Real time unit 1000 BaseTX kaptah2 Printer Multiple DSPs papyrus Connection to the customer s network Figure 2 23 Overview of the network 2008 11 11 Hardware and Networking B e Acquisition workstation network host name is sinuhe Analysis workstation network host names are minea and mut i e Workstation IP addresses are site dependant e Real time unit RT network host names are kaptah1 and kaptah2 e Dedicated RT IP network addresses are 192 168 100 11 and 192 168 100 12 e RT units run the collector server to collect the measured signals as well as the janitor server to control the MEG preamplifiers and the janitor_eeg server to control the EEG preamplifiers kaptahl runs the janitor server kaptah2 runs the janitor eeg server All application software and configuration files are loaded from the acquisition workstation during boot up 2008 11 11 35 B Hardware and Networking 36 2008 11 11
116. wp RF feedthr 1i SAM Dedi channels amplifier de high pass r amplifier S pas am fiker filter S Ba a Dedicated LAN Figure A 3 Schematig diagram of the EEG electronics 2008 11 11 113 Technical diagrams Digital control RS422 floating 12 V EEG control feedthrough filter EEG preamplifier backplane 5 ewe Control signal RS422 amp 15 V EEG preamplifier reterence board 4 T system ps _ EEG optoisolation EEG preamplifier board 1 8 pcs 8 channels board i J Buffered reference test oscillator signal ECG0 2 l reference el actGND signal feedthrough filter 4 pcs 16 channels unit EEG Ch 1 64 to ignal Acquistion Module EEG preamplifier frontplane 2 pcs i EE Buffered reference Isolated power EEG feedthrough filter 24 V jet eS E s pree m 8 test oscillator signal S re T 6 i 7 Ch 1 32 Unipolar reference el actGND e Isolated floating 12V Non isolated 15V Ch 33 60 Unipolar Ch 61 64 Bipolar r EEG preamplifier backplane EEG databus termination Empty slot EEG preamplifier board if 8 pcs 8 channels board 3 EL21014 EEG preamplifier 2 zm front plane 2 pcs Ch 65 92 Unipolar Ch 93 96 Bipolar 3 Ch 97 124 Unipolar Ch 125 128 Bipolare 3 1 Signal cable between EEG preamplifier backplanes 2 Sign
117. y isolating RF feedthr power supply transformer _ filter _ Osc Wo Behe ete pee elias ee ee as 1 IVME rack N I EEG control feedthr i S 15 VN HE ontrol K Non iso gt A m v F 230 v mad i ey i _ power PF feedthri bim Dc offset Gain amp high i _ Optic link fiter Optic omp _ pass control UR SCORE SEED EAE a IER C Heine link Electrode EEG optoisolation signal feedthrough filter EEG rack l F i PE EA i JA d P ape HH Unipolar t ME ban Dd channels Differential Buffer amplifier Buffer Optoisol Lowp RF feedthr SAM Dd O amplifier dc high pass amplifier filler filler tt gd Reference at electrode s lt j i eee oe 1 Al Real ti a Batter e i ct gnd nT N j computers on o i amp Ground Buffer Ground unisce GU dance electrode amplifier driver Isolated floating Grounded Signal Bd 28 y modules a Osc l 12ch SAM E V G L 43 Osc is N Ac Osc v lt Osc i 2 M B Work Y 4 Test oscillator l i ur o y Station H i i Fiber opt I f Dc offset Gain amp high ink comp pass control MEER E ERES Le REA RE DNE n EEG optoisolation signal feedthrough filter gt ly i bs cian MMC d Electrodes A Ly Ya N fy M lt psr c Fs NC 4 Biunipolar Differential Buffer ampl Buffer Optaisol Lo

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