Lunar DPXS X-Ray - Service training
Contents
1. ld Theory and System Overview Rev F 2 2006 DPX consists of 4 Primary Modules e X Ray Generation Tube Power Supplies e X Ray Detection Detector Counting AGS Communication Communications with Host PC Error Detection e Mechanics Motion Control Power Sub System AC Isolation Transformer Protects Unit from Voltage E L DPX IQ IEC All Fer sucha are fused GT POWER BLOCK nd IV d u al ly ISOLATION E GRAM 120 220 V AC systems alike only difference is in fusing Scanner and PC controller draws 12 5 A max 120V requires a 15A dedicated line m NODULE 6 Separate Power Supplies 26 VDC Mechanics 5 amp 12 VDC Logic and Communications 28 VDC Tube Current 2 High Voltage X Ray Generator 1 High Voltage X Ray Detector and 12 VDC Supply Scanner Contro ommunications 5 and 12 VDC Supply Scanner Control and Communications his power supply drives Logic circuitry 5 Communications 12 Between the SBC and the Host Computer CENTENT Pulses Power the detector high voltage power supply 12 Indicator Amber LED on the SBC 26 VDC Drives Motion Mechanics and Positioning Aid Powers Tube Head Fans Powers Mechanics Transverse Motor Longitudinal Motor Shutter Collimator Solenoids Powers Patient Positioning Aid Laser or large LED Green light on scan arm is lit when this power2. Detection All Subsystems e E Stop Collimator Control Control signals ARE NOT generated here This is a way point where control signals Solenoids generated by the SBC are Optically Isolated e Sensing of Collimator Limit Switches e OINK to collimator also goes through XORB User Interface What s the scanner doing Light Indicators shutter light must illuminate when shutter opens e Normally closed circuit x ray on light on when gt 0 1 mA of current runs through tube driven by mA feedback through the SBC Patient Localizer laser Positioning controls on arm End of Exposure Alarm triggered by loss of mA feedback or closing of the shutter LEDS YEARS Motor Control Moving the Scan Arm e SBC sends commands to OINK OINK routes to CENTENT e Commands Run Hold and Direction Motors are placed in Hold upon MAMA generation of X Rays i IEEE CENTENT motor controller tell Drives Stepper motors HEEE e Different Rev s of Motors require different wiring configurations be careful Refer to manual for directions Stepping Pulse Sent By SBC Measured at OINK TP6 Transverse or OINKTP12 gt Longitudinal Laser Board Drives patient Positioning Aid This board is idle until the SBC sends a signal to the OINK which in turn sends 26 VDC to the Laser Board The Laser board steps the 26 VDC input down to 5 VDC which activates the Laser Do N
3. supply is on X Ray Production 28 VDC Power oupply Dedicated to the X Ray Tube Head Filament e Solid State Relay enables Power Supply and Tube Head Filament Transformer e Only on when X Ray Tube Head is being ramped up Red LED on MAX Board indicates the presence of 28 VDC Dedicated HV Power Supply for Detector Dedicated to power the detector Voltage Potential to 1000 VDC Typically 650 680 VDC Keeping system power on keeps detector at thermal equilibrium Increased detector life 12 VDC input IEC Systems AMP Module ncorporates AMP Board and Power Supply into single Unit Non IEC Systems Power Supply is in Electronics Pan a Ja dd Positive and Negative HVPS Enable the generation of X Rays Positive and Negative HVPS Enable the generation of X Rays Hunt Dedicated Create 6Ke 38KeV each potential across X Ray Tube Head insert As soon as 41 KeV potential exists X Rays exist Types vary depending on the sub type of scanner Programmed by the SBC 3mA Maximum Current HVPS in High Current scanners DPX L DPX alpha DPX SF and DPX IQ HVPS New Spellman or Bertan Units from the two vendors are interchangeable Can mix and match but not recommended 3 0 mA Maximum Current Input from AC line Protected by Isolation Transformer 40 KeV DC 38 KeV per power supply Service Tip Use care when changing
4. SUPPLY AGSDCA 0193130 HV POWER SUPPLY HV POWER SUPPLY Troubleshooting Troubleshooting the AGS System e Signs Low BMD Total Body Scans have Halo White lines on Femur or Spine Scans e Checks QA History Look for Air Count flux P 12 Rollover Aluminum Wedge test checks stability of AGS e Actions Replace PMT Adjust AGSDCA TP 4 see Service Manual Section 6 2 tightens window lessens number of amplify commands Stable correctly adjusted AGS e TP 12 signal monitor Ben e Should see stable 2 4 VDC signal with voltmeter or Lg with oscilloscope agus Signal is Amplified or Attenuated based on input from AGS DCA Desired output is 2 4 VDC Fri nn nn ende zd 11 GEF ti Tt I u s wt vr m om lt i ipsu GF dg EE LJ a 7 ae Signal Test Points Signal Expected If the Signal TRA 12 VDC 12 VDC _ Spikes UP TP2 GND 0 VDC lt AGS Rollover TRES 12 VDC 12 VDC Spikes DOWN TP 4 Signal In 2 4 VDC e AGS Rollunder TRE a T B 2 PDC Either condition above is pa Output LUBIARDC trouble AGS With Rollunder TP 12 Monitor Peaks Downward unstable signal Signal is coming in too high Tek Stopped M Acquisitions Hohl ui Hr 0 6 6 0 e cune o AGS is sent too many attenuate commands signal out of range the attenuate counters Rollunder causing INACCURATE BMD results Counters r
5. X Ray Dual Channel Analyzer Primary Function of the DPXDCA Discrimination of High and Low Energy Pulses e Sends logic signal to SBC for each low and each high energy signal it detects Reads High and Low energy signals Does not do the counting only recognition of signal e Electronically identical to AGSDCA however potentiometer settings are very different Discriminating High and Low Energy Pulses DPX DCA Windows A single pulse passes A single pulse passes through the high through the low energy energy window window channel 1 channel 2 the the AGSDCA sends a DPXDCA sends a single logic pulse to the single logic pulse to low energy counter on _ the high energy the SBC LUNAR counter on the SBC SBC Board Single Board Controller rs PL SBC Scanner Control and Communication Functions e Brains of scanner 8032 Intel Processor Overall operation and control Motion control pulse counting limit switch sensing Thermocouple Sensing HV and Current settings e HS232 communications with host computer e 56 K available memory SBC Microprocessor Reset The Processor will reset itself if the scanner is powered up if the Comm port is interrupted if other circuit boards fail fail safe ifthe RESET button on SBC is pressed if the E Stop button is pressed eo a There is no Appendix MAX Board enables X Ray Source MAX Board enables X Ray S
6. beam size to limit patient exposure during exam LUNAR X Ray Detection Sub System LUNAR X Ray Detection Detector PMT Scintillating Material Sodium lodide converts photons into visible light then to an electrical pulse Each photon creates a single pulse Pulse Amplitude is directly proportional to the energy of the X Ray which produced it 6 7 mV for Low Energy 10 mv for High Energy PMT Photo Multiplier Tube increases signal strength Variable HVPS 1000VDC Max Potential set by SBC typically 600 800 VDC Signal out rides piggy back on gt 700VDC power in As scintillation crystal or photocathode deteriorate the detector will loose resolution and must be replaced All counts decrease lows faster than highs causing air ratio to increase Spillover will also increase due to high energy counts getting weaker X Ray Detection AMP Board AGS Board AGSDCA Board DPXDCA Board AMP Board AMP Board Amplification and Pulse Shaping Amplification of charge pulses from the PMT Gain of approximately 240Av Shape signal into a stable bipolar pulse Drive the pulse down a 50 Ohm coaxial cable to the AGS board 5m of cable 12 VDC drives amps Located next to detector in metal case on IEC Certified systems part of AMP Module which also includes the detector power supply Separate board on older systems non IEC Troubleshooting the AMP Board oymptoms No Coun
7. each maximum number of attenuate commands reset anc try to bring signal into range again New detector with old AGS may cause this or a mis adjusted AGS system tsi o en SS Eee Eu Enz na 6 6 04 TR AO O era ee ee L UNAR AGS With Rollover TP 12 Monitor Unstable signal peaking upwards A 51 90ms c Rollover MEM LI REAL EE signal comes in too low in window too many amplify commands sent to AGS the amplify counters Rollover causing INACCURATE BMD results Counters reach maximum and reset to lowest setting e try and bring signal back into range Causes deteriorating detector weak amplifier bad ground or signal cable mis adjusted AGS system AGSDCA Produces Gain Control Data for the AGS Provides Amplify or Attenuate signal to AGS Board 2 Windows Amplify if Signal comes in Low Attenuate if signal comes in High One of the two LED s on the AGS will flash each time an amplify or attenuate signal is sent by the AGSDCA High energy signal is in High energy signal is in Note this is a logic signal Channel 1 window Channel 2 window not the actual data signal senda ATRN sends Attenuate being sent back to the AGS commande i command to the AGS Electronically identical to DPXDCA however potentiometer settings are very different Troubleshooting the MAX Board Hed 28V DC present Green Fuse is good LED s will only be lit when the relay is triggered Troublesh
8. eaks are characteristic of the tungsten target used in the ibe est insert Requirements for Accurate Determination of Bone Density e Two Unknowns in Image Tissue Bone Requires two measurements be made of the same area and compared Unfiltered Spectrum has single Peak can only measure attenuation of single uniform substance or an object containing two substances where one of the two h TFT 10 0 9 E 0 8 707 t i os Zos W 204 j Sos iu 0 2 04 o K Edge Filtration K edge filter Cerium Ce EN Ce has a K shell Absorption Edge at liceo 40 KeV Filters both low and high energy photons Thickness of filter effects count rate Two peaks are visible after the X Ray beam has passed through the TENET Cerium filter 38 KeV 70 KeV Note the relative numbers of counts for the two energy peaks o o o N e o o a 2 gt o o o w gt z am 0 5 Lu E j Lu c o h e 8 Collimator Beam Limiting Device Collimator Control of the X Ray Exposure Collimator Control of the X Ray Exposure e FDA Certified component e 2 Slides 2 limit switches controlled by linear solenoids and springs Shutter e blocks beam e Tantalum attenuates X Rays keeps them contained prevents exposure during ramping and patient positioning Collimator slide Determines Beam size two holes e 1 68mm Medium e 84mm Fine e software determines
9. he 28 VDC so a 31 6 is typically a thermostat error e An arc may also cause an error in the MAX which sends a false thermostat error The tube head thermostat never opens because of heat typically this is a tube head control cable failure or a short inside the tube Error Detection Sensing System Faults Emergency Stop Detection Error Detection Motion Detection Errors Detected by OINK Signal sent by OMI HEX Code Error Possible Cause Board 15 4 Transverse Motion OMI signal lost e Monitor on Pin 2 of Continuous resetting of watch dog on OINK J 13 ONIK Board 23 3 Longitudinal Motion OMI signal lost e This section of the board Comiti i eng watch dog on detects system faults it 27 2 28VDC PS Loss of power to then sends a signal to the TH ma Mi SBC to shut down X Ray OINK production and mechanics 27 E Stop E Stop SI EZ Hard interrupt signalis 30 0 TH Thermostat TH thermostat sent via J19 causing orde HRREE motors and x ray 31 6 Unknown Any of the above shutdown error determination An Error Has Occurred follows 15 4 Transverse Mechanics Esc to Continue Control and Sensing of the Shutter and Collimator Solenoid control from SBC to Collimator Actuation Pulse OINK Actuation Pulse e 26 VDC to Open Drops to hold current when Limit switch is tripped e Newest OINK Rev L continuously triggers shutter to hold open e Limit Switches Sense Position of Slides in Collima
10. ooting tip mP4 P5 and TP13 should be continuous when the Tube Head control cable is hooked Up Indicates TH Filament is good Test Point TP 3 TP 4 TES TP 6 TP12 TP 13 TP 14 Signal Ground Q1 Output Filament Drive Signal Q2 Output Filament Drive Signal 12 VDC 28 VDC Filament Drive Signal 12 VDC Expected 76kV 750mA 0 000 VDC 16 VDC 16 VDC 12 VDC 28 VDC 46 vDG 12 VDC Troubleshooting with the XORB e f ramping trouble exists TP 1 5 2 and 6 good troubleshooting guides current ramping signal Test Point Signal Expected 76kV 7 sec after SBC and 750mA receives command to TP1 uA Monitor 750 VDC generate x rays TP2 KV Monitor 3 800 VDC voltage ramping signal TP3 kV Programming 3 800 VDC 7 sec after SBC TP5 uA Monitor 750 VDC receives command to TP6 kV Monitor 3 800 VDC generate x rays TP7 kV Programming 3 800 VDC Troubleshooting at the SBC Test Point Signal Expected 76kV 5mA TP 18 PMT HV 1 VDC 1000V at Feedback detector TP14 Current Set 750 VDC TP 17 Current Feedback 50 VDC LED Power Present TP 15 KV Set 3 80 VDC TP 16 KV Feedback 3 80 VDC Go po TP 24 kV Feedback 3 80 VDC Red 12 VDC Amber 12 VDC Unknown errors e 31 6 errors multiple error events occurring An Error Has Occurred at the same time RD W e thermostat and 28VDC errors Esc to Continue e A thermostat error disables t
11. ot Plug Unplug 26 VDC Video In with the power on this will destroy transistor Q1 on the OINK and the laser will not turn off OMI Board Optical Motion Interrupt OMI Function Detect arm movement There are 2 OMI s on a DPX series scanner longitudinal transverse e These boards have an infra red beam emitter detector A slotted wheel which rotates while the mechanics are functioning breaks the beam When the beam is broken the OMI sends a pulse to the OINK If the pulses are absent the OINK reports a motion error oub system interaction putting It all together X Ray Production SBC is the command OINK is the key and the relay is the lock SBC OINK E HV PS TUBE HEAD e The SBC sends the command to generate X Rays to the OINK The OINK trips the relay Therelay turns on AC to the 28 VDC supply and the HV power Supplies H kV flows to the tube head 28 VDC flows to the MAX Tube head The SBC regulates and monitors the kV and mA following a ramping profile until the desired kV mA are set X Ray Detection Collimator Detector Amp Upper cable bundle Lower cable bundle AGS AGSDCA DPXDCA SBC Computer y D p DPX IQ IEC POWER BLOCK DIAGRAM ISOLATION TRANSFORM ER How EN FUSES 100110 230240 VDC POWER F2250 1254 HADC HE gt EN FUSES 45VDC HV 100110 230240 HADC HHNDC Lg MODULE Fi1254 06 POWER F31254 06
12. ource SBC enables the 28 VDC power supply via the OINK and the High Voltage Power Supplies through the solid state relay MAX and Filament Transformer in the Tube Head work with power from the 28 VDC power supply MAX regulates X Ray Insert Filament temperature by controlling the filament current As filament temperature increases the number of electrons available for X Ray production increases SBC reads feedback from HVPS and adjusts filament current accordingly Transient Suppression the XORB Xorb is short for tranzorbs optical isolation of HV and ground protects logic circuitry XORB s primary function is to ground out high voltage transients or spikes in the X Ray generation system logic circuit protection All X Ray Generation system power flows through the XORB good place to check signals and power Board Test Point TP1 TP2 TP3 TP5 TP6 TP7 Signal uA Monitor kV Monitor kV Programming UA Monitor kV Monitor kV Programming Expected 76k and 750mA 750 VDC 3 800 VDC 3 800 VDC 750 VDC 3 800 VDC 3 800 VDC Mechanics OINK Board OMI Board SBC Board OINK Board Optical Isolation Noise Reduction OINR or OINK OINK Board Functions 4 Main Sections Mechanics Control e Motor Control Fan Control 26 VDC to fans normal operation always on User Interfaces e Indicator Lights e Rocker Switches for Manual Motion Error
13. power supplies mounting screws are different PAN AS IA RAMS E X Ray Production Subsystem LUNAR Basic Theory of X Ray Production e Tube Head Insert fixed anode Filament e Warm it up low current from Filament Transformer 76 KeV Potential across Insert 0 150mA to 4 750mA CT gt Electrons e boil off of filament ENN 7 Cathode um e Accelerated across 76 KeV potential strike Tungsten Target Anode knocks an e off of target as another e falls into the orbit an X Ray Photon is produced E gt Y FS APE DIA Components of the LUNAR DPX X Ray Tube Head FDA certified component Lunar Manufactures Oil Filled Metal Housing Fixed Anode X Ray Inser Lead Shieldec Filament Transforme Beam Hardening Tungsten is boiled off of Anode pits and collects on the glass of the insert absorbs X Rays Pitting due to high temperature damages Anode focal Spot Filament can burn out similar to incandescent light bulb LUNAR Oil leak possible causing arcing due to air in tube X Ray Production in the LUNAR DPX Iube Head e X Ray Tube Ramped up to proper operating voltage and current HVPS e X Ray Insert Converts current into X Rays e Produces broad spectrum of photon energies 15 80KeV 1 0 0 9 gt 0 8 097 LU 0 6 gt Ww 204 gt sS 0 3 Lu Co 04 20 30 40 50 60 70 PHOTON ENERGY keV Unfiltered X Ray Spectrum at i 80 KV The small p
14. tor used as feedback mechanism TALL THE HE UTA Measu red at OIN K Board Anode N R DPX Series X Ray Generation 28 VDC must be present to enable the tube head filament viaa transistor kV at HVPS must also be present to enable filament current loss of kV or 28 VDC disables filament current mA feedback from HVPS and mA program from SBC drive filament current per voltage from SBC Zero mA feedback causes full drive of the filament current which will immediately correct itself under normal operating conditions because of the feedback control loop an arc or a short will cause a ramping failure f SBC drive signal and mA feedback are equal the filament drive stays the same A kV spike may not cause a system fault but due to V RI the current must increase this causes our count rate to increase causing white lines as the detector becomes saturated f scanner errors it will be a single line entry KV mA out of spec typically mA will be high due to the principle described above
15. ts No Amp Attenuate Lights on AGS Board AMP TP6 to TP4 on AGS should be continuous if not signal cable break exists Never Unplug J2 LEMO HV in with scanner power on it will destroy the AMP Board ONLY non IlEC systems Test Point TP2 TP6 TP TP 8 TPS Input Pulse Output Bipolar Pulse 12 VDC 12 VDC Expected Value 1 0 mVDG 2 4 VDC High 1 6 VDC Low 12UDC 12 VDC 0 VDC The AGS System AGS Board AGSDCA Overview and Function of the AGS AGS Aui matic Gain Stabilization System Consists of AGS Board AGS DCA Dual Channel Analyzer Board Pulses come in from AMP Board at J11 TP4 2 4 VDC bipolar pulse carrying both high and low energy signals AGS routes same signal to both AGS DCA and DPXDCA J4 and J7 Two LED s on AGS Board e 1 Amplify 2 Attenuate AGS adjusts gain on High and Low energy signals from input from SE AGSDCA LUNAR OP CAL Signal SBC disables the AQSNOA T r nn tha evetar OA en Compares voltage of High Energy Pulses to set limits Sends back logic signal that instructs the AGS Board to Amplify or Attenuate the incoming signal from the PMT Gain is constantly adjusted to keep the high energy peak within a preset window 2 4VDC 2 8 By stabilizing the gain on the high signal the low is stabilized as well Adjustment is to raw Data Both High and Low Energy Pulses 2 0 DPXDCA Dual Photon
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