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Development and Implementation of the ClearPEM

1. o aaa DACs calibration test bench anaa ee Typical DAC channel calibration curve o oo ee High voltage regulation circuit schematic ooo ee ee DACs calibration software flowchart 2 ee ee HV regulation circuits calibration setup ooo ee eee SBO HV regulation circuits calibration curves 00000004 Histogram representing the distribution of the gain in the HV regulation circuits of the SB Or cre Beg to Re RR ae OM eee Aire te Meets Bg ica Seo NOG he ge ete Histogram representing the distribution of the offset in the HV regulation circuits of the SO eine Betyg cance Mind ae an he tay a pula Co Ge dak ge ec ea AMty eA SB1 HV regulation circuits calibration curves 2 0200 0000004 Histogram representing the distribution of the gain in the HV regulation circuits of the Babe quim nerds T Selig SE ES nce AOR Cam ad aces na a alas a de Bm Histogram representing the distribution of the offset in the HV regulation circuits of the SB Asante Leak at fe eh Ria Aah A E S RES E alte lane te eae A e Different paths in the SB between the connectors and the ADC Measuring temperature circuit ee ee SMs temperature reading calibration software flowchart Graphical interface of the calibration software 000000004 FEB temperature reading calibration setup o oo 000000004 FEB temperature reading calibration curves 2 2 0 0 0 2000
2. IEEE Transactions on Nuclear Science 53 1 2006 E Albuquerque P Bento F Gon alves C Leong P Lous J Nobre J Rego P Relvas P Rodrigues L Silva M M Silva I C Teixeira J P Teixeira A Trindade and J Varela The Clear PEM Electronics System IEEE Transactions on Nuclear Science 53 5 2006 7 Jo o Pinheiro Development and Study of the Detector Control System and Calibration Software 8 a for the Clear PEM Scanner Masters thesis Instituto Superior T cnico Universidade T cnica de Lisboa 2008 E Albuquerque V Bexiga R Bugalho C S Carri o B Ferreira M Ferreira F Gon alves C Leong P Lous P Machado R Moura P Neves C Ortig o F Piedade J F Pinheiro J Rego 63 9 10 11 12 13 14 15 16 17 18 19 20 21 22 A Rivetti P Rodrigues M M Silva I C Teixeira J P Teixeira J C Silva A Trindade and J Varela Experimental Characterization of the 192 Channel ClearPEM Frontend ASIC Coupled to a Multi Pixel APD Readout of LYSO Ce Crystals Nuclear Instruments and Methods in Physics Research Section A 2008 Intech instruments LTD Temperature conversion table rt table platinum resistance http www intech co nz products temperature typert html Online 2010 KEPCO the power supplier M MST 0 6V 20A http www kepcopower com mst htm Online 2010 ISEG high voltage
3. The ClearPEM Sonic detector hardware is similar to the ClearPEM detector having the same power supplies data acquisition system and Super Modules However it has two main differences an upgraded SB and a cooling system controllable through the PC Therefore the ClearPEM Sonic DCS is basically a reimplementation of the ClearPEM DCS but including new functionalities The DCS includes two new sub modules to control and monitor the new SBs and to control and monitor the Kodiak chiller The main function of the ClearPEM Sonic DCS as the ClearPEM DCS is to switch ON OFF the detector switching ON OFF the hardware sub systems in the correct order First the cooling system then the low voltage system then the high voltage system and finally setting the output voltages of the SB Digital to Analog Converters DACs 27 4 1 Developing Environment The initial goal was to develop the ClearPEM Sonic DCS in C C programming language because the ClearPEM DCS implemented in LabVIEW was unstable and did not allow a clinical technician to use the detector However results from Chapter 3 demonstrated that there was no need to change the development approach therefore LabVIEW development was maintained LabVIEW has several features that allow a faster development among these features is the fact that LabVIEW programs do not have to be compiled into executables prior to running It has a graphical interface that is easy to develop and to connect
4. The variation of the APDs gain is 6 Volt for a gain of 150 which is the gain of the ClearPEM Sonic APDs 24 The maximum difference between the output voltage and the set voltage is 0 23 V So the gain of the APDs has maximum error of 1 38 0 23 x 6 which is which can be neglected 5 3 SMs Temperature Monitoring Calibration Each half SM has four temperature probes and each probe is composed of two PT 100 resistors connected in series The voltage of each pair of PT100 is read by a signal conditioner circuit 25 Since each Detector Head has eight half Super Modules there are 32 temperature probes To readout the voltage sent by the signal conditioners four NS ADC101C027 10 bit Analog to Digital Converters ADCs 26 with eight channels each are used It is necessary to convert the read voltages in the probes into the correct temperatures For this purpose a calibration has to be performed To calibrate the temperature reading three pairs of high precision resistors are used Each pair of high precision resistors emulates a pair of PT100 resistors in a certain 51 Service Board 0 Service Board 1 channel n Set V Measured V Set V Measured V channel 0 432 38 432 370 464 38 464 351 channel 1 430 38 430 426 462 38 462 390 channel 2 428 38 428 462 460 38 460 360 channel 3 426 38 426 521 458 38 458 345 channel 4 424 38 424 460 456 38 456 351 channel 5 422 38 422 389 454 38 454 319 channel 6 420 38 420 405 452 3
5. The Acquisition tool is responsible for acquiring the data processed by the Data Acquisition Electronics It is also responsible for processing the acquired data for a second time After this stage the data is ready to be processed by the image reconstruction algorithms The power supplies status and alarms displayed in the Acquisition Manager are provided by the DCS which is responsible for control and monitor the power supplies the SB the cooling system and the DAE 2 5 Summary THE ClearPEM and ClearPEM Sonic are PET scanners designed to detect early stage breast cancer Scintillator crystals are readout by FE The processed data stream is filtered by data acquisition electronics Power is distributed by LV and HV power supplies and the generated heat removed by a cooling system In Table 2 1 the HW and the variables that are controlled and monitored by the ClearPEM DCS are presented Device Monitored Variables 4 Voltages 4 Kepco LV Power Supplies 4 Currents 5 Internal Status 8 Voltages 8 ISEG HV Power Supplies 8 Currents 5 Internal Status 4 Temperature Sensors 2 Pressure Sensors Service Boards 64 Super Modules Temperatures 64 Vth DACs Voltages 64 HV regulation DACs Voltages Table 2 1 ClearPEM controlled and monitored hardware In Table 2 2 the HW and the variables that are controlled and monitored by the ClearPEM Sonic DCS are presented 11 Device Monitored Varia
6. 384 HV bias are necessary To provide 384 HVs for the APDs biasing an auxiliary mezzanine matrix is connected to the 32 HVs provided by the SB The matrix provides inter connection between the 32 channel HV regulation circuits and the 384 output voltages necessary for the APDs The SB includes two temperature sensors to provide information about the temperature on the detector head to the DCS Four 12 bit ADC read the voltage on the PT100 temperature probes 9 The SB also has a pressure sensor because the heads used to be pressurized with gas to avoid condensation but this system is currently not in use The communication with the temperature sensors is made through PC protocol An on board low power Field Programmable Gate Array FPGA to perform housekeeping functions such as to reset the Frontend ASICs at system startup 2 1 3 ClearPEM Sonic Service Board The DAC sub system was modified in order to give more resiliency to the SB In the SB of the ClearPEM Sonic instead of one DAC with 32 channels to provide the threshold voltages four DACs with 8 channels each are used For the control of the 32 HVs values the single DAC was also replaced by four DACs So if a DAC is damaged and has to be replaced the calibration process is only necessary on eight regulation circuits and not on 32 regulation circuits Finally eight ADCs with 8 channels each have also been added to the SB in order to monitor the 32 threshold voltages and the 32 contr
7. If the value is bigger than 15 A the warning signal becomes red 4 high voltage current error Refers to the automatic monitoring of the ISEG output current If the value is bigger than 2200 uA from the set value the warning signal becomes red 5 high voltage High Refers to the automatic monitoring of the ISEG output voltage If the value is bigger than the set voltage the warning signal becomes red 6 temperature DH1 Refers to automatic monitoring of the temperature on the DH1 If the temperature is outside the limits the warning becomes red 23 7 temperature DH2 Refers to automatic monitoring of the temperature on the DH2 If the temperature is outside the limits the warning becomes red 3 2 5 ClearPEM DCS Tests and Results In order to test the ClearPEM DCS a software capable of simulate hardware errors was developed in this thesis This was necessary due to the scanner localization in Porto and restrict time to work with it This software is mainly composed of global variables that simulate the presence of errors in the DCS The presence of errors can be activated or deactivated by the software user The DCS was modified in order to accept the errors simulation so instead of reading the real hardware status the DCS reads the simulated errors On Figure 3 8 the test software can be seen and on Figure 3 9 the test bench is shown Service Board ISEG HV power supply Figure 3 8 The tes
8. If any of this problems occur the DCS goes to error state while the problem is not solved Stability tests were also carried out with a test bench that include three Kepco LV power supplies one ISEG HV power supply and one SB The Kepco and ISEG power supplies were turned ON simulating the scanner running state To assure a long term stability the tests were carried out during periods of 12 hours and once for 48 hours During the entire time the DCS ran without any problem The ClearPEM DCS improvements were implemented in the first phase of this thesis and deployed in last October on the scanner at IPO Porto Several acquisition runs were done with the scanner and the DCS has not crash being able to detect problems in the scanner These problems concern communication failures between the DCS and the SBs temperatures out of bounds The DCS has demonstrated full and stable control of the power supplies and the SB 25 CHAPTER4 Development of the ClearPEM Sonic Detector Control System N this chapter the development and implementation of the ClearPEM Sonic Detector Control System DCS is discussed The DCS controls and monitors the detector hardware sub systems Kepco low voltage power supplies ISEG high voltage power supplies Service Boards SBs Data Acquisition Electronics DAE and its crate and the Kodiak chiller Like in the ClearPEM the DCS can be controlled through a graphical interface or through the Acquisition Tool 16
9. The Trigger and Data Concentrator board TRG DCC is responsible for the selection of events in coincidence pair of photons resultant of an annihilation and interfaces to the data acquisition computer This system is able to process up to 1 Mevent s which leads to a data output up to 225 MB s In order to send this amount of information per second a communication system developed at CERN 12 was adapted The DAE is composed of four DAQs and one TRG DCC Board which are inside a Compact PCI 6U Crate The DAQ system functionality is implemented using FPGAs two for each DAQ board The TRG DCC functionality is also implemented using one FPGA 6 The communication system is the S Link64 12 and is a FIFO like interface with a maximum throughput of 800 MB s The version used in the ClearPEM scanner can go up to 520 MB s two times higher than the expected bandwidth 13 10 2 4 Data Acquisition Software The Acquisition Manager is the graphical user interface available to the technicians that operate the scanner It interfaces directly with the other two subsystems Acquisition tool and DCS With the Acquisition Manager is possible to turn on calibrate perform an exam and switch off the scanner It also monitors the detector status power supplies voltages and currents and critical alarms The information displayed by the Acquisition Manager with the exception of the power supplies status and alarms is generated by the Acquisition Tool
10. http www iseg hv com download php 512 file url en iseg MMC pdf Online 2010 V et al Brigljevic Fedkit a design reference for cms data acquisition inputs In 9th Workshop on Electronics for LHC Experiments 2003 V Bexiga R Bugalho C S Carri o B Ferreira M Ferreira C Leong P Lous P Machado P Moura Neves C Ortig o F Piedade J F Pinheiro J Rego P Rodrigues I C Teixeira J P Teixeira J C Silva A Trindade and J Varela Experimental Validation and Performance Analysis of the Clear PEM Data Acquisition Electronics IEEE Medical Imaging Conference and 16th Room Temperature Semiconductor Detector Workshop 2008 DIM Distributed Information Management System http dim web cern ch dim Online 2009 National Instruments http zone ni com devzone cda tut p id 8534 Online 2009 Catarina Ortig o Development and Experimental Study of a Detector Module for Positron Emission Tomography PhD Instituto Superior T cnico Universidade T cnica de Lisboa 2009 SENSIRION Datasheet sht10 humidity and temperature sensor www sensirion com Online 2010 LYTRON Kodiak recirculating chillers technical manual http www lytron com cooling systems standard recirculating chillers kodiak aspx Online 2010 Linear Technology Ltc2615 http www datasheetarchive com indexer datasheet 015 dsa00258428 html Online 2010 E Balestrieri S Moisa and S Rapuano DAC static paramete
11. tests were carried out When any communication failure occurs in any State the beahviour of the DCS is the same as the one described in the previous list Except for a communication failure with the ISEG high voltage power supplies In this case an indicator in the DCS informs the user to shut down the detector with the emergency button assuring that all the detector is switched off preventing HW damaging 40 CHAPTERS ClearPEM Sonic Service Boards Calibration N this chapter the calibration of the ClearPEM Sonic Service Boards SBs is discussed There I are three systems that need to be calibrated the threshold Digital to Analog Converters DACs LTC2615 DAC with 14 bits 19 the high voltage HV regulation circuits and the Super Modules temperature monitoring system It is described why are the calibrations necessary and it is described the software developed to perform the calibrations The respective calibrations results are presented Due to the intrinsic variability of the gain and offset of the DACs the voltages set at the output of the DACs channels differ from the real output voltages In addition it can also be observed systematic biases in the gain and offset at the output of the HV regulation circuits due to the behaviour variability of its components In order to obtain the desired voltages at the output of the DACs and HV regulation circuits it is necessary to calibrate them To measure the temperature in the Super
12. Communication with Kodiak chiller OFF Orange Communication with Kodiak chiller unchecked DIM Green DIM communication ON Red DIM communication OFF Orange DIM communication unchecked Low voltage Relay Green Kepco relay normal Red Kepco relay switched due to bad power connection Orange Kepco relay unchecked Low voltage error Green Kepco output voltage normal Red Kepco output voltage error detected by hardware Orange Kepco output voltage unchecked Low voltage overtemp Green Kepco temperature normal Red Kepco temperature out of bounds Orange Kepco temperature unchecked Low voltage overcurrent Green Kepco current normal Red Kepco current out of bounds Orange Kepco current unchecked Low voltage voltage error Green Kepco output voltage normal Red Kepco output voltage error detected by software Orange Kepco output voltage unchecked Low voltage power loss Green Kepco power input normal Red Kepco power input lost Orange Kepco power input unchecked ISEG crate voltage Green ISEG internal voltage normal Red ISEG internal voltage wrong Orange ISEG internal voltage unchecked 70 ISEG crate temp Green ISEG internal temperature normal Red ISEG internal temperature wrong Orange ISEG internal temperature unchecked High voltage current error Green ISEG output current normal Red ISEG output current out of bounds Orange ISEG output current unchecked High voltage Gre
13. Front End Electronic Board Field Programmable Gate Array General Purpose Interface Bus High Voltage Inter Integrated Circuit Integrated circuits Low Voltage Magnetic Resonance imaging Positron Emission mammography Positron Emission tomography Recommended Standard 232 Service Board Standard Commands for Programmable Instruments Trigger and data concentrator board Ultrasonography Universal Serial Bus xiii CHAPTER Introduction 1 1 Motivation REAST cancer is one of the most common cancers among women Although the number of breast B cancer cases has increased since 1990 deaths caused by it has decreased due to improvements in breast cancer treatment and early detection Breast Self Examination and X ray mammography screening are the current mainstays for breast cancer detection Breast Self Examination is an easy and low cost method but is very inaccurate typically tumors smaller than 2 3 cm are not detected X ray mammography has been proven to detect breast cancer cases at an earlier stage and to reduce the number of women dying from the disease 1 Besides X ray the most common exams for breast cancer detection are Ultrasonography US and Magnetic Resonance Imaging MRI US is used to evaluate suspicious breast lesions which are detected with X ray and it also allows to distinguish a benign from a malign lesion 2 but is unable to detect lesions smaller than 5 mm Compared to X ray MRI is much more sensitive
14. HV regulation circuits of the SBs the FE temperature reading and the ASIC thresholds These calibrations must be performed in order to have precise voltages at the output of the HV regulation circuits to ensure the correct reading of the FE temperatures and to provide stable reference for the threshold voltages of the Frontend ASICs Considering the ClearPEM the objectives are e to analyze the existing DCS e to detect the problems and possible improvements e to improve the DCS and make it usable in a clinical environment Regarding the ClearPEM Sonic DCS besides the existing functionalities of the ClearPEM DCS the objectives are to develop the e temperature control and monitoring of the cooling system e temperature monitoring of the FE and SB e voltage control and monitoring of the SB e detection of non functioning ICs in the SB Considering the ClearPEM Sonic SBs the objectives are to calibrate the e threshold voltages DACs e HV regulation circuits e FE temperature reading 1 3 Thesis Organization The thesis is organized as follows In Chapter 2 the ClearPEM and the ClearPEM Sonic architecture and main building blocks are described Special emphasis is given to the FE sub system and to the SB electronics in order to contextualize the main hardware elements that need to be controlled and monitored by the DCS system Chapter 3 discusses the ClearPEM DCS and the improvements needed as well as its implementation
15. To communicate with the ISEG power supplies CANBus protocol is used epco piii niia Boards RS 232 CANBus Q asas fis RS 232 q DIM Acquisition Manager Figure 4 3 ClearPEM Sonic DCS communication protocols and interfaces In the appendix the User Manual of the ClearPEM Sonic DCS is presented This manual allows an user to fully understand the functionalities of the DCS and how to use it In the User Manual all the graphical user interfaces can be analyzed in detail As it can be seen in the User Manual cover the DCS is designated Service Manager 4 3 1 New Service Board Control and Monitoring Due to the hardware modifications in the SB replacement of the two DACs of 32 channels for eight DACs with eight channels each the introduction of eight Analog to Digital Converters ADCs to monitor the DACs output voltages the introduction of eight temperature sensors the introduction of one humidity and temperature sensor Sensirion SHT10 17 the replacement of the existing Field Programmable Gate Array FPGA for another FPGA that communicates with the integrated circuits ICs and the communication with the DCS is done using the RS 232 interface The control and monitoring sub module functions are e to set and measure the 64 threshold voltages e to set and measure the 64 DAC output voltages that control the high voltage HV regulation 31 circuits e to monitor the 16 temperature sensors e to m
16. applied to all Vths DACs in the Service Board If the user wants to change the values individually has to use the squares bellow Set as default If this button is pushed the values present in the squares are set as default and saved in a text file 5 Restore default If this button is pushed the values in the squares became the values saved ina text file 83 SERVICE BOARD Vth SETUP Menu ARe E escore fora PI q l Threshold Voltage Threshold Voltage per Channel per Channel Figure 9 Threshold Voltage control menu HV Setup Menu With this menu is possible to control each one of the HV values Set new default values restore the old ones and reset the DACs 1 Apply changes By pushing this button the values in the indicators are set into the HV channel regulators Exit Pushing this button closes the menu Voltages per channel Service Board 1 and 2 HVs are values that allow the user change the values individually Set as default If this button is pushed the values present in the squares are set as default and saved in a text file Restore default If this button is pushed the values in the squares became the values saved in a text file Reset DAC If this button is pushed the value in the control DACs becomes 0 84 SERVICE BOARD HV SETUP Menu ee Voltages per Channel RR O ESSO NR Figure 10 APD high voltage cont
17. be changed visualized and reseted to the default values The default values are stored in a text file This menu allows to set the DAC voltages in order to obtain at the HV regulation circuits output the wanted voltages To set the desired voltages the following equation is used pe 4 1 where x is the voltage to be written in the DAC y is the desired voltage b and m are the values obtained from the calibration discussed in Chapter 5 which are stored in two text files On page 85 of the User Manual the graphical interface of the HV SETUP MENU is presented where the indicators of the voltages and the buttons that allow to change their values can be seen The Vth SETUP MENU was implemented to allow an advanced control of the threshold voltages It allows to set individually the threshold voltages and also allows to set a common voltage for all the DACs Like in the previous advanced menu it is possible to restore the default voltages by pressing a button The default threshold values are also stored in a text file On page 84 of the User Manual the graphical interface of this menu is presented To monitor the SMs temperature an advanced menu was also created This menu presents detailed information about the temperature on the Top and Bottom FEBs of both SB Super Modules Four pixelized maps are presented being the temperature shown in an indicator matching the correspondent pixel The color grade is equal to the one used in the SBs
18. by the LV controller The internal status are power loss over load relay error over temperature current error and voltage error ISEG High Voltage Control and Monitoring ISEG HV power supplies are controlled and monitored through the CANBus interface using a Dynamic Linked Library DLL This library is necessary to establish the communication between LabVIEW and CANBus hardware Since the working voltages of the Avalanche Photo Diodes APDs are between 370 V and 470 V all the ISEG modules are set to 500 V channel regulators in the SB and the mezzanine matrix do the necessary regulations This sub module main functions are to e detect communication failures e turn ON OFF the HV power supplies e monitor the output voltages and currents e monitor internal voltages currents and temperatures Several internal status are monitored but are not shown in the ISEG control menu Like the previous sub module an advanced menu is available that shows the ISEG internal status output and set voltage output and set current and allows to change the output voltages Service Board Control and Monitoring Communication between the SBs of each head and the DCS is made through an USB to I C converter National Instruments USB 8451 in which an C hub is mounted The PC hub allows to open an Pc connection to each one of the SBs The SB control and monitoring main functions are to e detect communication failures e configure all
19. das por duas cabe as detectoras planares suportadas por um bra o rob tico e um sistema de aquisi o e selec o de dados Uma cabe a detectora constitu da por 96 matrizes de 32 cristais cintiladores A radia o emitida pelo corpo humano devido injec o de uma subst ncia radioactiva nos pacientes detectada por cristais cintiladores que transformam a radia o em luz Esta luz convertida em sinais el ctricos pelos fotod odos de avalanche APD Avalanche Photo Diode A amplifica o e processamento dos sinais dos fotod odos s o efectuados em circuitos especificos ASICs Application Specific Integrated Circuits especificamente desenvolvidos para este projecto Cada ASIC pode processar sinais de 192 APDs O sistema que est equipado com 64 ASICs permite detectar e processar sinais de 12288 APDs As tens es necess rias ao funcionamento dos APDs e dos ASICs s o geradas numa placa independente designada por placa de servi o SB Service Board Esta placa inclui ainda um sistema de controlo e monitoriza o destas tens es de alimenta o de humidade e de temperatura A vers o inicial do sistema de controlo e monitoriza o DCS Detector Control System desenvolvido para o ClearPEM apresentava problemas de estabilidade Durante a sua utiliza o o software parava de responder sendo imposs vel de usar num ambiente cl nico por um t cnico hospitalar A primeira parte do trabalho realizado no mbito des
20. graphical interface As has been mentioned the DCS is controlled through the DIM protocol and is also controllable in a stand alone mode In this last mode the scanner control is made through the LabVIEW graphical interface The main responsibility of the DCS is to turn ON turn OFF and monitor the ClearPEM scanner So when the turn ON command is sent by the Acquisition Manager or is set through the graphical interface the DCS goes by all the states excepting Error starting at Stop state and finishing at the Running state At this point the scanner is ready to perform an exam The opposite path is taken to turn OFF the scanner Kepco Low Voltage Control and Monitoring This sub module is responsible for the control and monitor of the four LV power supplies and the respective controller The communication is done using Standard Commands for Programmable Instruments SCPI The control and monitor of the LV power supplies main functions are 17 e detection of communication failure between the controller and the DCS e power modules voltages configuration power modules monitoring in terms of voltages currents and internal status e measured values storage e report of monitoring information to the acquisition Manager There is also an advanced menu available only in stand alone mode which allows to change and monitor the voltages to change the monitoring refresh and storage time and to monitor all the internal status provided
21. is ON and the Kepco output voltage is different than the set voltage the sub routine shutdowns the scanner If the current is bigger than 15 A the scanner is shut down This is a redundant system because the Kepco power modules have their own automatic voltage monitoring which sets the voltage error warning However if this system fails the software is also able to detect voltage output issues The output voltages measurement is done every 5 seconds In order to send the output voltages values to the Acquisition Manager through the DIM protocol an additional measure for each Kepco module was made In order to reduce the number of measures global variables were created that keep the 5 seconds measuring The value of the global variables is then sent to the Acquisition Manager 3 2 2 ISEG Control and Monitoring Modifications Communication with the ISEG controller is done through the CANBus protocol using a DLL developed in C to establish the communication between LabVIEW and the CANBus to USB converter The original DCS crashed during its utilization This problem was narrowed down to the ISEG control because the same error happened both in DCS and in the ISEG individual control module Every time LabVIEW stop responding a warning about memory allocation appeared This happened due to lack of memory allocation by LabVIEW to the correct CANBus initialization To solve this problem the initialization function which had three required paramet
22. necessary because a sudden change from 500 V to 140 V could damage the circuit components The DAC voltage steps are of 0 2 V being the linear regression done using 13 points Finally the software performs a linear fit in order to obtain the gain and offset values The calibration of one channel takes about 120 s On Figure 5 7 the flowchart of the HV regulation circuit calibration software is shown The graphical interface of the calibration software is similar to the one used to calibrate the DACs 47 Calibration Bench To calibrate the HV regulation circuits besides the SB three Kepco power supply modules one ISEG HV power supply module one multimeter and one PC are used The power supply modules are used to supply the SB with the necessary working low and high voltages The multimeter is used to measure the HV output The PC is used to send the output voltages to the SB to read the voltage measured by the multimeter and to control the Kepco and ISEG power supplies On Figure 5 8 the calibration setup scheme is presented CAN Bus Figure 5 8 HV regulation circuits calibration setup HV regulation circuits calibration results On Figure 5 9 the response of the HV regulation circuits to the DACs output voltages of SB O is presented As it can be seen the response curves are different for different regulation circuits For SB 0 the gain values are between 132 68 and 136 15 The offset values are between 2 02 V and 4 33 V The R
23. of Channels Ss 00027 00023 0 0024 0 0025 0 0026 00027 0 0028 Gain m Figure 5 21 Histogram representing the distribution of the gain in the temperature monitoring calibration Number of Channels 065 0 655 0 66 0 665 0 67 0 675 0 68 Offset Volt Figure 5 22 Histogram representing the distribution of the offset in the temperature monitoring calibration 57 CHAPTERO6 Conclusions HE ClearPEM and ClearPEM Sonic are PET scanners designed to detect early stage breast cancer T Based on an high granularity APD readout with more than 12000 channels The scintillator crystals are readout by Frontend electronics The processed data stream is filtered by data acquisition electronics Power is distributed by state of the art power supplies and the generated heat removed by a dedicated cooling system All these systems must have a stable control and monitoring to assure that the scanners work properly To control these systems a software application named Detector Control System was developed The objective of this thesis was to improve the ClearPEM DCS and to develop the ClearPEM Sonic DCS ClearPEM Detector Control System The ClearPEM Detector Control System is responsible for controlling and monitoring the ClearPEM hardware sub systems the Kepco and ISEG power supplies systems and the Service Board It is also responsible for the control and monitoring of the DAE system In presence of errors the DCS does not allow the user
24. of the control DAC which sets the optocoupler level The circuit was originally designed at EFPL Lausanne and was found to be suitable to APD biasing applications 23 since it shows a linear behavior for the required biasing current As an example if a voltage of 1 07 V is set at the output of the control DAC at the output of the HV circuit the value is around 140 V and if the DAC is 3 8 V at the output of the HV circuit the voltage is around 500 V The HV regulation circuit thus shows a linear correspondence between the two voltages with a multiplicative factor in this example around 130 Due to process variation in the production of the operational amplifiers optocouplers and passive components the multiplicative factor is characteristic of each channel and needs to be determined experimentally during the Services Board calibration process Due to variability in the components behaviour of the HV regulation circuits the output voltages have different gain and offset values If at the output voltages of all the control DACs channels is the same at the output of the HV regulation circuit the measured voltages are different So it is necessary to calibrate each of the 32 HV regulation circuit of each SB On Figure the HV regulation circuit schematic is presented Figure 5 6 High voltage regulation circuit schematic Since the output of the HV regulation circuit has a linear behaviour the best fit line method is used to obtain the gain a
25. offset value obtained from the calibration and m is the gain value obtained from the calibration So using Eq 5 4 with the values obtained from the calibration the read voltage is converted into the correct temperature Calibration Software To make the calibration process faster a Lab VIEW program was developed This program main function is to read the voltage that the ADC channel under calibration is measuring The program assumes that the user places the high precision resistors in the correct order 103 9 Q 107 79 Q and 109 73 Q and waits for each measure before changing the resistors After placing the 3 pairs of resistors in the FEB s connectors and measuring the voltages a linear fit is performed The linear fit is done using 3 points that correspond to the 3 high precision resistors The calibration values are obtained from the linear fit On Figure 5 17 the SMs temperature reading calibration software flowchart is shown On Figure 5 3 the graphical interface of the calibration software is presented 54 Insert first resistor Measure and save voltage Change resistor no Measured 3 resistors Figure 5 17 SMs temperature reading calibration software flowchart Figure 5 18 Graphical interface of the calibration software 55 Calibration Bench The calibration bench is composed of three pairs of high precision resistors Table 5 3 one SB one FEB three Kepco power supply modules and one
26. presented Kodiak Detector Head SUA Cooling Plates Acquisition Workin in Ems Ethernet Figure 3 1 ClearPEM communication architecture DIM Protocol In the DIM protocol the server provides services to the clients A service is composed of a set of data and it is recognized by an identifier Services are requested by the clients only once and they are updated by the server either at regular time intervals or whenever conditions change according to the type of service requested by the client In order to allow transparency this communication protocol has a name server which establishes communication between the server and the clients Servers publish their services by registering them in the name server Clients subscribe to services by asking the name server which server provides the 14 service and then contacting the server directly On Figure 3 2 the interaction between servers clients and the name servers is presented The name server keeps an up to date directory of all the servers and services available in the system In the DCS is implemented a DIM server and several services are provided The acquisition Manager is the client and subscribes the services of the DCS Register Me Request Services Service Service Service Data Command Figure 3 2 Representation of the DIM protocol 3 1 1 DCS Architecture and State Machine The control and monitor software is organized in three main
27. specially to small lesions with less than 1 cm 3 MRI has also some limitations in some cases it is not possible to distinguish malign from benign lesions Dedicated Positron Emission Tomography PET scanners are being developed in order to improve breast cancer detection PET is a technology used to detect cancerigenous lesions based on the detection of radiation The radiation is emitted in the form of two photons by the human body due to a radio tracer that is injected in the patients Studies show that a sensitivity of 90 can be achieved with a Positron Emission Mamography PEM scanner for lesions of various sizes 4 With the goal of improving breast cancer detection the PET Consortium has developed and built a PEM scanner ClearPEM 5 installed in late 2008 at IPO Porto The consortium is currently developing a new scanner ClearPEM Sonic which is going to be installed at Marseille France in late 2010 ClearPEM is currently under clinical trials The scanners hardware is composed of two main electronic subsystems the Frontend Electronics FE and the Data Acquisition Electronics DAE The FE is responsible for detecting the radiation and for converting it into digital signals The scintillator crystals translate radiation into light and the avalanche photodiodoes APDs convert this light into electric signals The Application Specific Integrated Circuits ASICs 6 perform the amplification and shaping of the electr
28. squared values are between 0 99998 and 1 which shows the linearity of the points The histogram on Figure 5 10 presents the distribution of gain values of the SB 0 HV regulation circuits The mean value of gain is 134 4 and the dispersion is 0 65 which indicates a similar behaviour between HV regulation circuits in terms of gain On the other hand the mean values of the the offset values is 3 004 V with a dispersion of 24 Which is expectable because the offset is a small value being the difference between the offset values considerable The histogram of the offset values is presented on Fig 5 11 On Figure 5 12 the response of the HV regulation circuits to the DACs output voltages of SB 1 is presented As it can be seen the response curves are different between the channels For SB 1 the gain values are between 132 65 and 135 45 The offset values are between 0 42 V and 3 96 V The R squared values are between 0 99998 and 1 which shows the linearity of the points The histogram on Figure 5 13 presents the distribution of gain values of the SB 1 HV regulation circuits The mean value of gain is 134 1 and the dispersion is 0 67 which indicates a similar behaviour between HV regulation circuits in terms of gain On the other hand the mean values of the the offset values is 48 470 445 420 395 HV channel Volt 370 345 hl bt il et be hi be RI lel RT tol Toe 320 2 4 2 6 2 8 3 32 3 4 DAC output Volt
29. stages Initialization Hardware Control and Finalization The first stage consists on the initialization of the global variables and on the creation of semaphores for the communication protocols The semaphores prevent that two parallel processes attempt to communicate at the same time through the same communication channel The second stage consists on the hardware control and monitoring All routines for the hardware control monitoring and communication are designed to work in parallel so if one process stops responding the others will be able to continue their function normally Also in the second stage the scanner status is sent to the Acquisition Manager and control commands are sent by it The final stage is only responsible for the communication semaphores termination The main feature of the hardware control is the state machine composed by five states Error Idle Stop Ready and Running This state machine is very important for the scanner correct functioning because some hardware systems can only be turned ON or accessed if another hardware systems is already on The LV power supplies can be turned ON at any moment if the DCS is not in the error state The HV power supplies can only be turned ON if the LV power supplies are turned ON in order to prevent integrated circuits damaging The output voltage of the DACs of the SB can only be set if the HV power supplies are ON On Figure 3 3 the organization of the the state machine is pres
30. the chiller e emulate the chiller presence allowing to work with the DCS without communicating with the chiller e setup the upper and downer limits of the water temperature e detect communication failure between the DCS and the chiller The sub module waits for the chiller to response to an initialization command When the chiller is detected the control and monitoring starts The software sub module waits for a turn ON OFF command if it does not receive any command the reading of the temperature and internal status takes place When the chiller is turned ON a temperature of 18 C is configured and the water starts to circulate Initially the water temperature might be outside of the working limits The limits are between 15 C 21 C because the required temperature is 18 C and a 43 C margin is recommended 18 After turning ON the chiller the temperature is monitored for a while If the temperature does not reach the limits within 10 minutes the DCS is forced into the Error State After turning ON if the temperature is inside the limits the monitoring of the chiller continues normally If the temperature of the chiller goes out of the limits the DCS is forced into the Error State Also if the communication between the DCS and chiller fails the DCS is forced into the Error State When the DCS goes into the Error State the control and monitor sub module of the chiller starts over The flowchart of the chiller control and m
31. the status table and force the Service Manager to go to idle state 68 __sTopsm 5 Kodiak chiller 7 Status table In this table is the information regarding the status of all the hardware controlled and monitored by the Service Manager Peo Coo e ee ees eee eee eer E SERVICE MANAGER 7 9 KEPCO Low Voltage 3 eee ISEG High Voltage stun N 9 SERVICEBOARD Leer D SS poe 2 Lemon 61 O Status ooi id ee ee Ce ER ee RT 2 ee a er A ee a er m TETE oll a a ee mo PETSys oe ee ee PETSys Figure 1 Service Manager Main menu graphical interface Low Voltage Rs 232 Green Communication with Kepco ON Red Communication with Kepco OFF Orange Communication with Kepco unchecked High Voltage CANBus Green Communication with ISEG ON Red Communication with ISEG OFF Orange Communication with ISEG unchecked SB1 Rs 232 Green Communication with SB1 ON Red Communication with SB1 OFF Orange Communication with SB1 unchecked SB2 Rs 232 Green Communication with SB2 ON Red Communication with SB2 OFF Orange Communication with SB2 unchecked 69 DAE Rs 232 Green Communication with DAE ON Red Communication with DAE OFF Orange Communication with DAE unchecked DAE crate Rs 232 Green Communication with DAE crate ON Red Communication with DAE crate OFF Orange Communication with DAE crate unchecked Cooling Rs 232 Green Communication with Kodiak chiller ON Red
32. to the functional blocks 15 Lab VIEW is a programming language specially for developing software for instrumentation Developing the ClearPEM Sonic DCS using LabVIEW allows the re utilization of part of the ClearPEM DCS due to the similarity between both detectors Making the development of the new DCS a faster process 4 2 DCS Architecture DCS architecture is divided in three main parts Control Initialization Hardware Control and Control Finalization Control initialization includes the setup of the semaphores for all communications channels The initialization of the communication channels refers to the configuration of the RS 232 baud rate for Kodiak chiller Kepco low voltage power supplies SBs and Data Acquisition Electronics and for the ISEG power supplies the CANBus port initialization The Distributed Information Management DIM protocol services are initialized to allow the DCS to be controlled through the Acquisition Manager If the initializations take place without any problems the control and monitoring can start Control and monitoring is where the most critical operations take place The Kepco and ISEG power supplies are monitored to detect internal errors and to measure the output voltages The Kodiak chiller is monitored in terms of internal errors and internal temperature Temperature humidity and DACs voltages as well as Super Modules temperatures are monitored in SBs The DAE is monitored in terms of voltages cur
33. to turn ON the scanner The DCS receives control commands from the Acquisition Manager through the DIM protocol being invisible for the clinical user Only an expert user has complete access to the DCS and its advanced menus During the analysis of the original DCS that constitutes the initial part of this thesis one main problem was detected Due to lack of memory allocation by LabVIEW for the ISEG C DLL used to establish communication between the DCS and the USB to CANBus converter the software stopped responding The DLL was modified in order to avoid the memory allocation The Kepco communication interface 59 was changed from GPIB to RS 232 making the communication interface a low cost system Several improvements were carried out regarding voltages currents and hardware status monitoring and control Regarding the detector heads monitoring the temperature is now measured by two temperature sensors located on the SB In order to test the modifications performed in the DCS several software and hardware based tests were conducted These tests include lost of communications wrong output voltages wrong output currents wrong temperatures and hardware internal status errors The new DCS was deployed on the ClearPEM at IPO Porto Several runs were done with the detector in a clinical environment and the DCS has demonstrated a stable behavior ClearPEM Sonic Detector Control System The ClearPEM Sonic scanner is an overhaul of
34. 000008 0G Histogram representing the distribution of the gain in the temperature monitoring Calibration Ss Sisk RE ap Bo ae da Be E DS ee BE Sn Aad ah Bec RR fa Histogram representing the distribution of the offset in the temperature monitoring Calibrations 2 fait Las A ohh Slee he 4 ee aus ls eee ele he ose ek ee 46 48 54 2 1 2 2 3 1 4 1 5 1 5 2 5 3 List of Tables ClearPEM controlled and monitored hardware 2 0000 11 ClearPEM Sonic controlled and monitored hardware ooa 12 Hardware systems status regarding the state machine 16 Hardware systems status regarding the ClearPEM Sonic DCS state machine 30 Voltages measured at the DACs output 2 2 ee ee 45 HV regulation circuits set and measured voltages 2 20000 52 Resistance values and correspondent temperature 000 53 xi Xil ADC APD ASIC CERN CANBus DAC DAE DAQ DCS DH DIM FE FEB FPGA GPIB HV PC IC LV MRI PEM PET RS 232 SB SCPI TRG DCC US USB List of Acronyms and Abbreviations Analog to Digital Converter Avalanche PhotoDiode Application Specific Integrated Circuit European Organization for Nuclear Research Controller Area Network bus Digital to Analogical Converter Data Acquisition Electronics Data acquisition Detector Control System Clear PEM Detector Head Distributed Information Management Front End Electronics
35. 8 452 342 channel 7 418 38 418 364 450 38 450 380 channel 8 416 38 416 403 448 38 448 410 channel 9 414 38 414 348 446 38 446 415 channel 10 412 38 412 471 444 38 444 368 channel 11 410 38 410 485 442 38 442 395 channel 12 408 38 408 396 440 38 440 380 channel 13 406 38 406 476 438 38 438 423 channel 14 404 38 404 461 436 38 436 373 channel 15 402 38 402 237 434 38 434 370 channel 16 400 38 400 246 432 38 432 265 channel 17 398 38 398 490 430 38 430 323 channel 18 396 38 396 435 428 38 428 612 channel 19 394 38 394 449 426 38 426 384 channel 20 392 38 392 214 424 38 424 462 channel 21 390 38 390 347 422 38 422 445 channel 22 388 38 388 364 420 38 420 487 channel 23 386 38 386 243 418 38 418 381 channel 24 384 38 384 490 404 38 404 343 channel 25 382 38 382 451 414 38 414 339 channel 26 380 38 380 416 412 38 412 352 channel 27 378 38 378 350 408 38 408 383 channel 28 376 38 376 323 410 38 410 385 channel 29 374 38 374 376 406 38 406 365 channel 30 372 38 372 295 416 38 416 269 channel 31 370 38 370 210 402 38 402 351 Table 5 2 HV regulation circuits set and measured voltages 52 Number of Channels 5 6 7 8 Offset b Volt Figure 5 14 Histogram representing the distribution of the offset in the HV regulation circuits of the SB 1 temperature The resistance of the resistors and the correspondent temperature can be seen in Table 5 3 PT100 probes have a 0 39 Q C variation between 0 C and 30 C For a tem
36. Figure 5 9 SBO HV regulation circuits calibration curves Number of Channels Figure 5 10 Histogram representing the distribution of the gain in the HV regulation circuits of the SB 0 49 Number of Channels 8 9 10 Offset b Volt Figure 5 11 Histogram representing the distribution of the offset in the HV regulation circuits of the SB 0 470 445 420 395 HV channel Volt 370 345 320 24 25 26 27 28 29 3 34 32 33 34 35 DAC output Volt Figure 5 12 SB1 HV regulation circuits calibration curves 50 3 022 V with a dispersion of 16 Which is expectable because the offset is a small value being the difference between the offset values considerable The histogram of the offset values is presented on Fig 5 14 Number of Channels 137 138 139 140 Gain m Figure 5 13 Histogram representing the distribution of the gain in the HV regulation circuits of the SB 1 In order to verify the precision of the calibration on the HV regulation circuits the desired voltages for biasing the Avalanche Photo Diodes APDs were set and measured which can be seen in Table 5 2 From these measurements a systematic bias of 0 045 in the HV regulation circuits of the SB 0 was measured which indicates a difference of 0 17 V between the desired and the set voltage In HV regulation circuits of SB 1 the bias is 0 055 which represents a difference of 0 23 V between the desired and the set voltage
37. Modules is necessary to calibrate the reading of the voltage in the temperature probes 5 1 DACs Calibration The threshold detector implemented in the Application Specific Integrated Circuits ASICs need precise threshold voltages in order to select only the events relevant for the image reconstruction while discarding noise So it is of most importance to have precise DAC output voltages In principle the output of DACs obey to the equation 41 y x 5 1 where y is the output voltage and x is the set voltage However due to the gain and offset errors the DACs output obey to the equation y mx b 5 2 where y is the output x is the set voltage m is the gain error and b is the offset error 20 The calibration purpose is to guarantee that the desired voltages are obtained at the DACs output A graphical representation of the ideal and real DAC outputs is presented on Figure 5 1 DAC analogical output V 5 4 A 3 y mx b real 2 4 y x ideal 1 o DAC digital o 1 2 3 4 5 __ input V Figure 5 1 Graphical representation of the DAC different outputs For the DACs calibration two main methods can be used endpoint method and best fit line method 21 The first method uses the minimum value and maximum value points to calculate gain and offset The second method calculates the gain and offset errors based on a set of points between the minimum and maximum values In this method error values are d
38. PC The PC communicates with the Kepco power supply and with the SB using the RS 232 protocol The power supply modules are used to supply the SB and the FEB with the necessary working voltages The FEB is connected to the SB through the power supply cable and through the cable that is used to send the voltages from the signal conditioner to the ADC On Figure 5 19 the calibration setup scheme is presented FEB with high precision resistors Figure 5 19 FEB temperature reading calibration setup Calibration results On Figure 5 20 the response curves of the SMs temperature reading calibration is presented A plot that presents the read voltage versus the correspondent temperature is shown The gain values are between 0 00249 and 0 00259 The offset values are between 0 664 and 0 67 The R squared values are always 0 9999 which shows the linearity of the points VU oO Temperature 2C N O 10 E fi f 1 0 7 0 71 0 72 0 73 0 74 ADC value Volt Figure 5 20 FEB temperature reading calibration curves The histogram on Figure 5 21 presents the distribution of gain values of the temperature monitoring calibration The mean value of gain is 0 00255 and the dispersion is 1 16 which indicates a similar behaviour between temperature monitoring channels in terms of gain The mean values of the the offset values is 0 6674 with a dispersion of 0 22 The histogram of the offset values is presented on Fig 5 22 56 Number
39. als is done by ASICs Application Specific Integrated Circuits developed specifically for this project Each ASIC can process signals from 192 avalanche photodiodes The system is composed of 64 ASICs that allow to process 12288 APDs The necessary voltages for the APDs and ASICs are generated by an electronic board SB Service Board The board includes also a voltage monitoring and control subsystem as well as humidity and temperature measurement capabilities The initial version of the ClearPEM Detector Control System DCS presented some stability problems During its utilization the software stopped responding being its clinical use impossible for an hospital technician The first part of the thesis work consisted on the analysis and revision of this system The alarm policy the communication protocols the output voltages monitoring and the detector heads temperature monitoring were revised The system became stable and usable in a clinical environment Later on the ClearPEM Detector Control System was adapted for the ClearPEM Sonic Besides previous functionalities control and monitoring of the cooling system was developed To control and monitor the ClearPEM Sonic Service Board the DCS was also modified Keywords PEM Detector Control System Hardware calibration Contents Resumo ii Abstract v Contents vii List of figures ix List of tables xi List of Acronyms and Abbreviations xi 1 Introduction 1 LI Motivation 3 ae p
40. and obtained results In Chapter 4 the ClearPEM Sonic DCS development environment and its architecture are discussed The control modules adapted from the ClearPEM DCS are explained The new control and monitoring modules development and implementation are fully presented The tests done to the DCS are explained and the results are shown In Chapter 5 the calibration strategies of the ClearPEM Sonic SB are implemented Finally in Chapter 6 the conclusions are presented CHAPTER Overview of the ClearPEM Detector OR a PET scanner to detect a cancer lesion it is necessary to inject a patient with a radiotracer This F substance is absorbed in higher quantities and faster by the cancerigenous cells in the body due to their higher metabolism The positrons released by the radio tracer collide with electrons in the body and both are annihilated emitting two photons which move on a straight path in two opposite directions These photons have a specific energy of 511 keV On Figure 2 1 the Positron Emission Tomography PET working principle is presented In order to detect the resulting photons the Positron Emission Mammography PEM system uses scintillator crystals and avalanche photodiodes APDs that together work as a radiation detector Using a pair of sensors crystal APD it is possible to reconstitute the route of the two emitted photons ClearPEM and ClearPEM Sonic are PET scanners being the ClearPEM Sonic basically an overhau
41. are turned OFF If they are OFF by pushing this button they are turned ON Turning ON the SB means that the threshold voltages are set the HV channel are ramped UP and RESET commands are sent Service Boards temperature Map The temperature in the service board is presented in a form of pixelized map Each indicator in the map matches the sensors in the service board And the Mean indicator shows the mean value of the 8 sensors In the figures bellow is shown where the temperature sensors are placed in the SB The remaining pixels without a sensor indicate a value that is the mean value of the closest sensors Service Boards humidity sensor These 3 indicators show the measurements done by the humidity and temperature sensor This sensor is located in the center of the board Humidity Indicates the relative humidity in the detector head Temperature Indicates the temperature measured by this sensor Dew point Indicates the dew point value 4 Front end electronic boards temperature The temperature in the FEBs is also presented in the form of a pixelized map Each pixel indicates the temperature on a half part of a half Super Module Advanced menus buttons HV Setup Menu Calls the HV channels advanced menu Vth Setup Menu Calls the Vth channels advanced menu FEB temperature Menu Calls the FEB temperature advanced menu SB Status Calls the menu that shows the SBs status 81 SERVICE MANAGER Service Board Control PET
42. been modified due to some modifications in its hardware The number of status alarms has been increased and the critical errors recovery computer crash or LabVIEW crash has been improved All these improvements are going to be discussed in the next sections 3 2 1 Kepco Control and Monitoring Modifications The Kepco controller has two communication ports available GPIB and RS 232 The GPIB has a work rate of 1 8 MB s The price of the used GPIB to USB converter is around 550 euros 15 On the other hand the Kepco RS 232 port has a working rate between 4800 b s and 19200 b s The price of an USB to RS 232 converter is about 20 euros Both with GPIB and RS 232 communication SCPI is used to communicate with the Kepco controller Since the system does not require a fast control and the RS 232 system is a low cost system it was decided to change the Kepco controller communication protocol All the functions of the control and monitoring sub module were maintained One of the differences between the protocols besides the communication rates is that between writing and reading there has to be a 100 ms waiting period that is required by the Kepco controller Each time the DCS sends commands to the Kepco controller the response has to be read otherwise the receiver buffer will overflow and the communication has to be aborted 20 In order to avoid hardware damage an automatic voltage and current sub routine was implemented When the scanner
43. bles 4 Kepco LV Power Supplies 4 Voltages 4 Currents 5 Internal Status 8 Voltages 8 ISEG HV Power Supplies 8 Currents 5 Internal Status 1 Temperature Sensor Kodiak Chiller 1 Pressure Sensor 12 Internal Status Service Boards 16 Temperature Sensors 2 Humidity Sensors 64 Super Modules Temperatures 64 Vth DACs Voltages 64 Vth ADCs Voltages 64 HV regulation DACs Voltages 64 HV regulation ADCs Voltages Table 2 2 ClearPEM Sonic controlled and monitored hardware 12 CHAPTERS Clear PEM DCS Analysis and Improvements N the first section of this chapter the ClearPEM Detector Control System DCS is presented and I analyzed The DCS functionalities are described the architecture is explained and the control and monitor sub modules of the hardware are described The DCS controls and monitors the power supplies the Service Board SB and the Data Acquisition Electronics DAE The DCS clinical use is limited due to the fact that the software crashes during its utilization In the second section the implemented solution for the software crashing is explained The development of other improvements on the DCS software are also described To prove its robustness and functions after the implemented improvements tests done to DCS are shown and the results are presented 3 1 Detector Control System The DCS is a software developed using the National Instruments software LabVIEW V 8 2 1 Th
44. checked Vth DH2 Green Detector head 2 Vth normal Red Detector head 2 Vth out of bounds Orange Detector head 2 Vth unchecked Humidity DH1 Green Detector head 1 humidity normal Red Detector head 1 humidity out of bounds Orange Detector head 1 humidity unchecked Humidity DH2 Green Detector head 2 humidity normal Red Detector head 2 humidity out of bounds Orange Detector head 2 humidity unchecked DAE FPGA Green DAE FPGA status OK Red DAE FPGA status wrong Orange DAE FPGA status unchecked DAE Board Green DAE board status OK Red DAE board status wrong Orange DAE board status unchecked DAE Crate Green crate status OK Red DAE crate status wrong Orange DAE crate status unchecked Service Manager Green Service manager free of errors Red Service manager with error s Orange Service manager error s unchecked 72 2 Cooling control Menu The Kodiak recirculating chiller is controlled through this menu The chiller can be turned ON OFF by pushing a button The temperature and pressure can be monitored Several warnings are shown regarding the chiller internal status The maximum and minimum temperature can be set to control the alarm limits 1 Turn ON OFF button If the chiller is ON by pushing this button the chiller is turned OFF If the chiller is OFF by pushing this button the chiller is turned ON 2 Communication and temperature Cooling ready If this led is light
45. chiller is not right or a chiller internal error occurs the state machine goes to the Error State Turn chiller ON E E Turn T OFF ERROR Eror ERROR solved Turn Turn Kepco E OFF j ERROR j Pe ii lt RROR RUNNING ERROR Figure 4 2 The new DCS state machine State Kodiak Kepco ISEG SB Error OFF OFF OFF OFF Idle OFF OFF OFF OFF Cooling ON OFF OFF OFF Stop ON ON OFF OFF Ready ON ON ON OFF Running ON ON ON ON Table 4 1 Hardware systems status regarding the ClearPEM Sonic DCS state machine 4 3 Control and Monitoring Software Modules ClearPEM Sonic DCS includes five control and monitoring sub modules Each sub module is responsi ble for controlling and monitoring the respective hardware sub system Three of them Kepco ISEG and 30 DAE are reused from ClearPEM DCS The remaining sub modules for the SB and Kodiak chiller were implemented from scratch The alarm policy and the recovery system were also modified Figure 4 3 illustrates the type of communications between the DCS and the detector hardware and it also illustrates the communication between the DCS and the Acquisition Manager The control of the DCS through the Acquisition Manager is done using DIM protocol In order to control the hardware sub systems several types of communication protocols are used Communications with the Kodiak chiller the Kepco power supplies the SBs and the DAE use the RS 232 interface
46. d DASH rd AI JA E Pa bar hl Wa de ea Oa 1 WD ODIECUVES do et ty AMA A Rk ee ae OS 4k IR AL hy SE od 2 1 3 Thesis Organization cu ssa e e ee ee ee 3 2 Overview of the ClearPEM Detector 5 2 Detector Heads bt Mk breech Mew Boke a Bead eG Nd beet aera BND Ms 6 2 11 Frontend Electronics 2 sita aioe ae ee hw ah ot Od Hae A 6 2 1 2 ClearPEM Service Board aoaaa a 7 2 1 3 ClearPEM Sonic Service Board 2 0 ee ee 8 2 1 4 Cooling System isa ae e eee be haba hee babe bes 8 2 2 Power Supply System acna d aici e e a e va e oe we 9 2 3 Data Acquisition Electronics ooo ee 10 24 Data Acquisition Software tiee eae ra aE e E ee 11 2 5 SUMMALY us al e aada d Acialad a a e e a a ue T a a alee af A a aa T ake 4 11 vii 3 Clear PEM DCS Analysis and Improvements 3 1 Detector Control System 2 0 0000 ee 3 1 1 DCS Architecture and State Machine 0 4 3 1 2 DCS Control and Monitor Sub Modules 3 1 3 DCS Limitations 2 0 0 2 000 000 0002000000222 2 3 2 Improvements on the Original ClearPEM DCS 02 3 2 1 Kepco Control and Monitoring Modifications 3 2 2 ISEG Control and Monitoring Modifications 3 2 3 Service Board Control and Monitoring Modifications 3 2 4 DCS Alarms and Crash Recovery 000000004 3 2 5 ClearPEM DCS Tests and Results 2000004 4 Develop
47. d also for the fan control The first module functions are to e monitor the DAQs and TGR DCC FPGAs temperature power consumption and voltage level 19 e monitor DAQs and TGR DCC temperature voltage and current The second module functions are to monitor the DAE crate internal power supplies and the fans speed configuration Two advanced menus are also available in stand alone mode these menus allow to configure the fans speed voltage and current limits 3 1 3 DCS Limitations The analysis done on the DCS shown some limitations in its utilization The main problem concerns the software crashing during its utilization These crashes occur at any period of utilization The DCS does not perform automatic monitoring of voltages and currents If any problem occurs with the output of the power supply voltages the ClearPEM is only switched OFF if the user is monitoring the voltages and currents status If the DCS crashes and the scanner is turned ON when the DCS is turned ON again the DCS forces the scanner to be turned off This procedure is not wanted The DCS must be able be remain in the state that it was before the crash 3 2 Improvements on the Original ClearPEM DCS In the course of this thesis several improvements were made in the DCS in order to allow its clinical use The HV power supplies control and monitoring was improved The LV power supplies control and monitoring modified The SB control and monitoring has also
48. e main function of the DCS is to control and to monitor the hardware of the Clear PEM detector e to turn ON OFF the low voltage LV and high voltage HV power supplies e to measure voltages and currents of LV and HV power supplies e to set the output voltages of the SB Digital to Analog Converters DACs 13 e to monitor the Frontend Electronic Boards FEBs temperature e to monitor the detector heads pressure e to monitor the DAE and its crate in terms of voltages currents and temperatures The DCS has an alarm system which informs that an error has occurred There are several types of errors including communication errors power supplies internal errors SB errors ASIC threshold HV pressure and temperature and DAE internal errors If an error occurs in the Clear PEM scanner the DCS does not allow the clinical user to operate it The DCS uses several different communications protocols DCS communicates with the Kepco controller using GPIB protocol with HV power supplies using CANBus with the SB using IC and with the DAE using RS 232 The data concerning the monitoring of the power supplies voltages is sent to the acquisition Manager through the Distributed Information Management DIM protocol 14 The Acquisition Manager is also responsible for sending control commands to the DCS The Acquisition Manager communicates with the user working station using Ethernet On Figure 3 1 the ClearPEM communication architecture is
49. e Early Detection of Breast Cancer A Non Technical Summary Committee on the Early Detection of Breast Cancer Na tional Cancer Policy Board Commission on Life Sciences National Research Council http www nap edu catalog 10107 html 2001 Thomas M Kolb Jacob Lichy and Jeffrey H Newhouse Comparison of the Performance of Screening Mammography Physical Examination and Breast US and Evaluation of Factors that Influence Them An Analysis of 27 825 Patient Evaluationsl Radiological Society of North America 2002 K Kinkel T H Helbich L J Esserman and J Barclay Dynamic high spatial resolution MR imaging of suspicious breast lesions American Journal of Roentgenology 175 35 43 2000 K Schilling P Conti L Adler and L Tafra The role of positron emission mammography in breast cancer imaging and management Applied Radiology 37 4 26 36 2008 M Abreu J Aguiar F G Almeida P Almeida P Bento B Carri o N C Ferreira M Ferreira F Gon alves C Leong P Lous V M nica N Matela P Mendes R Moura J Nobre N Oliveira C Ortig o L Peralta R Pereira F Piedade J F Pinheiro J Rego P Relvas R Ribeiro A Rivetti P Rodrigues I Rolo J Sampaio A I Santos P Sousa L Silva M M Silva S Tavernier I C Teixeira J P Teixeira J C Silva R Silva A Trindade and J Varela Design and Evaluation of the Clear PEM Scanner for Positron Emission Mammography
50. els of the SBs were calibrated because the paths between the reading ADC and the connector to the FEB have different lengths This leads to different resistance values which means different voltage reading for the same temperature Future Work The first Detector Control System was an engineering prototype developed in 2007 for the ClearPEM scanner The improvements implemented in the DCS during this thesis transformed it into a more reliable software The modifications employed in the DCS to control and monitor the ClearPEM Sonic scanner added new control and monitoring functionalities The next step of the DCS development should be in a commercial level The DCS needs a dedicated PC with Microsoft Windows operating system to run due to being a LabVIEW software The choice of MS Windows was mainly dictated by the need to have an easy development environment in the initial phase of the project At a commercial level the most immediate action would be to merge the DCS into the Acquisition 61 Manager that has a Linux operating system This could be easily done as long adequate drivers for the CANBus are obtained In a second stage the entire LabVIEW DCS could be re implemented in C C in order to reduce the system cost 62 Bibliography 1 Margie Patlak Sharyl J Nass I Craig Henderson and Joyce C Lashof Mammog 2 3 4 5 a a 6 raphy and Beyond Developing Technologies for th
51. en ISEG output voltage normal Red ISEG output voltage out of bounds Orange ISEG output voltage unchecked Cooling level Green Kodiak water level normal Red Kodiak water level low Orange Kodiak water level unchecked Cooling flow Green Kodiak water flow normal Red Kodiak water flow low Orange Kodiak water flow unchecked Cooling limit Green Kodiak water temperature normal Red Kodiak water temperature out of bounds Orange Kodiak water temperature unchecked Cooling overtemp Green Kodiak water temperature normal Red Kodiak water temperature too high Orange Kodiak water temperature unchecked Cooling undertemp Green Kodiak water temperature normal Red Kodiak water temperature too low Orange Kodiak water temperature unchecked Temperature DH1 Green Detector head 1 temperature normal Red Detector head 1 temperature out of bounds Orange Detector head 1 temperature unchecked Temperature DH2 Green Detector head 2 temperature normal Red Detector head 2 temperature out of bounds Orange Detector head 2 temperature unchecked 71 HV DH1 Green Detector head 1 HV normal Red Detector head 1 HV out of bounds Orange Detector head 1 HV unchecked HV DH2 Green Detector head 2 HV normal Red Detector head 2 HV out of bounds Orange Detector head 2 HV unchecked Vth DH1 Green Detector head 1 Vth normal Red Detector head 1 Vth out of bounds Orange Detector head 1 Vth un
52. ented Figure 4 7 Test software graphical interface To test the error handling of the DCS all the control parameters of the test software were activated In order to assure the robustness of the DCS at all times all the errors that the test software generates were tested in all the states of the State Machine e inthe Idle State if any error occurs the DCS only goes to the Error State When the error is solved the DCS goes to the Idle State again 39 e in the Cooling State if any error occurs the Kodiak chiller is turned OFF and the DCS goes to the Error State When the error is solved the DCS goes to the Idle State e in the Stop State if any error occurs the Kepco low voltage power supplies and the Kodiak chiller are turned OFF and the DCS goes to the Error State When the error is solved the DCS goes to the Idle State e in the Ready state if any error occurs the ISEG high voltage power supplies the Kepco low voltage power supplies and the Kodiak chiller are turned OFF and the DCS goes to the Error State When the error is solved the DCS goes to the Idle State e inthe Running state if any error occurs the SB DACs are set to zero the ISEG high voltage power supplies the Kepco low voltage power supplies and the Kodiak chiller are turned OFF and the DCS goes to the Error State When the error is solved the DCS goes to the Idle State To test the response of the DCS to communication failures with hardware sub modules
53. ented Table 3 1 shows the status of the different hardware sub modules regarding the state machine The DAE crate is monitored in all the states and data is always being sent through DIM this is not shown in Table 3 1 The SB turned ON means that the LV and HV regulation DACs are set with the correct values and the temperature is being monitored 15 mmk E Error solved ERROR Turn Turn Kepco erp p ON OFF ERROR A ie i RUNNING o Ea STOP lt Figure 3 3 The DCS State Machine State Kepco LV ISEGHV SB Error OFF OFF OFF Idle OFF OFF OFF Stop ON OFF OFF Ready ON ON OFF Running ON ON ON Table 3 1 Hardware systems status regarding the state machine 16 3 1 2 DCS Control and Monitor Sub Modules On Figure 3 4 the graphical interface of the DCS main menu is presented In this menu is possible to turn ON and turn OFF the scanner by pressing the Start Sequence button The status ON OFF of the Kepco LV power supplies the ISEG HV power supplies and SB can be monitored The state of the DCS state machine can also be seen on the States indicator In the bottom the Stop button which stops the DCS can be seen In the status table the status of the different ClearPEM hardware is also represented Warnings regarding the communication status and internal errors of the power supplies and detector heads are displayed ji A o a A m gt S 9 m rs Bi Figure 3 4 DCS main menu
54. enu From this menu the detector can be turned ON or turned OFF The Service Manager software can be switched OFF In the following list the graphical interface is described The used enumeration matches the enumeration used on Figure 1 1 Status of the four controlled hardware components If the green dot is highlighted the respective hardware is turned ON 2 State In this indicator is shown the current state of the Service Manager In table 1 the status of the hardware regarding the Service Manager is shown Table 1 SM State regarding the hardware status Cooling Stop Ready Running 3 Start Sequence button The function of this button is to turn ON OFF the detector hardware If the detector is OFF when this button is pushed the turning ON sequence starts This sequence goes through all the states excepting error state Idle Cooling Stop Ready Running After this sequence is finished the detector is ready to perform exams To turn OFF the detector the same button has to be pressed The following sequence is performed to turn OFF the detector Running Ready Stop Cooling Idle 4 Stop Start sequence progress bar This bar shows the progress of the Start Stop Sequence regarding the status of the hardware 5 Stop Service Manager button When this button is pushed the Service Manager stops working 6 Clean Errors amp Go to Idle button This button function is to clear the errors present on
55. ers two integers and one string was modified Since the three parameters have always the same values they were deleted as parameters and defined as constants inside the function making the memory allocation unneeded The ISEG power modules do not have an auto output voltage and current monitor In order to detect wrong output voltages and currents an automatic voltage and current sub controller was implemented If the scanner is ON and the ISEG output voltage is different than the set voltage the sub controller shutdowns the scanner If the output current is bigger than 2200 u A maximum set current the scanner is turned OFF Like in the Kepco monitoring the output voltages measurement is done every 5 seconds and values sent through DIM implied an additional measure So in order to avoid this additional measure global variables were created which keep each 5 seconds measurement The value of the global variables is then sent to the Acquisition Manager 3 2 3 Service Board Control and Monitoring Modifications There was a misleading temperature reading due to a voltage loss of 300 mV in the power cables between the SB and the FEBs Due to this the FEBs temperature reading was deactivated Two temperature sensors were added to each detector head and connected to the respective SB The monitoring of the sensors was developed the communication between the sensors and the DCS is done using IC through the hub The temperature measurement no
56. es are controlled from this menu From here is possible to turn ON OFF the power supplies to monitor the output voltage current and to call the advanced menu Fig 5 shows the menu graphical interface 1 Power ON OFF If ISEG power supplies are ON by pushing this button are turned OFF If are OFF by pushing this button are turned ON 2 Advanced Menu The ISEG control advanced menu is called by pushing this button 3 Modules monitoring If the green led is light green the output is ON If the led is dark green the output is off In the voltage and current indicators the output voltage and current can be monitored 4 Emergency Cutoff If the green led is light green the red button must be pushed An emergency situation has occurred and the iseg power modules must be shut down SERVICE MANAGER ISEG HV Module Control PETSys Ned PET Imaging Syst A Figure 5 ISEG power supply control graphical interface 78 ISEG advanced control menu This menu allows the user to have a more complete control and monitor of the ISEG power supplies 1 Exit menu By pushing this button the advanced menu is closed 2 Emergency Cutoff If the green led is light green the red button must be pushed An emergency situation has occurred and the iseg power modules must be shut down 3 Advanced monitoring modules Are composed of 8 monitoring modules number of ISEG modules in the rack Each monitoring module is composed of 8 indicator
57. etector head is presented Figure 2 7 The graphite chiller plate assembled on Figure 2 6 The Kodiak recirculating chiller the detector head 2 2 Power Supply System The power supply system is composed of four Kepco low voltage power supplies 10 and eight ISEG HV power supplies 11 A controller Kepco MST 488 27 with GPIB and RS 232 communication interfaces controls the low voltage power supplies The HV power supplies are composed of eight modules which are inside a crate and have a controller with a CANBus communication interface In order to isolate from the main electric grid the low voltage power supplies the HV power supplies the computer that runs the DCS the computer server and the DAE system described in the next section an isolation transformer is used All these components are inside a rack On Figure 2 8 the ClearPEM power architecture is presented Service Rack Detector Head Kepco LV tad Service Board Modules High and low voltage power lines ISEG HV DAE Isolation transform Figure 2 8 ClearPEM power distribution architecture 2 3 Data Acquisition Electronics The electric signals received by the DAE are sent by the FEBs Data Acquisition DAQ boards are responsible for performing deserialization temporary data storage and algorithmic processing The first level of data processing takes place in the DAE
58. etermined using the minimum mean squared error distance To calibrate the DACs of the SB the best fit line method was used This method calculations are based on the full scale of the DACs without favoritism to any point After calibrating the DACs the gain and offset values are obtained These values are used in x y b m 5 3 where x is the voltage set at the DAC output y is the desired output voltage b is the offset value and m is the gain value both obtained from the calibration So using Eq 5 3 with the values obtained from the calibration to set the voltage in the DACs the gain and offset errors are corrected 42 Calibration Software A program was developed in LabVIEW to calculate the gain and offset values of the DACs The software defines a set of voltages in the DAC and measure the DAC output with a multimeter Keithley 2000 22 The setting of the voltages starts with 0 V and finishes with 3 V in order to cover the entire working range of the DACs The set voltages have a 0 2 V interval between them and the set and measurement take 0 6 s The 0 6 s delay period exists due to delays in the communications between the software and the hardware This means that a calibration of one channel takes 9 s After setting and measuring the voltages in the DAC a linear fit is performed using the obtained voltages The offset and gain values are obtained from this linear fit The set and measured values are stored in a file for fut
59. f 0 5 C After assuring that the SBs are inside the temperature limits the software enters in a cycle where it waits for a turn ON OFF signal or reads the SBs statuses every 5 seconds The SBs monitoring consists on measuring the temperature and humidity sensors and the ADCs This is done every 5 seconds to assure a fast response if any anomaly occurs Turning ON the SBs consists on setting all the DACs output voltages with the desired working voltages Turning OFF consists on setting the DACs output voltages to O V If the temperature or humidity go out of the allowed limits the SBs control and monitor sub module forces the DCS into the Error State Also if the communication between the DCS and the SBs fails the DCS is forced into the Error State In the flowchart is only shown what happens if an error occurs in the measurement stage To make the flowchart easier to understand the communication error situations are not shown However a communication failure can occur at any time So if a communication error occurs the software is designed to force the DCS into the Error State The graphical interface of the SBs control and monitoring is presented on page 82 of the User Manual The interface is divided in three modules two for the SBs temperature and humidity monitoring and other module which have the buttons to call the advanced menus These advanced menus are discussed further ahead Besides these three parts a turn ON OFF button was also i
60. fi INSTITUTO SUPERIOR T CNICO Development and Implementation of the ClearPEM Sonic Detector Control System Gon alo Nuno Bento Duarte da Silva Dissertation submitted to obtain the Master Degree in Electronics Engineering Jury Chairman Prof Jo o Costa Freire Supervisor Prof Jo o Manuel Coelho dos Santos Varela Co Supervisor Prof Maria Helena da Costa Matos Sarmento Member Prof Jos Ant nio Henriques Germano June 2010 Acknowledgments First I would like to thank Professor Joao Varela who had the courage to start this valuable and innovative project for the opportunity to contribute for its development Secondly I must thank Professor Helena Sarmento for all the reviews of this thesis Thirdly I would like to thank to all my TagusLIP colleagues for all the help and good times I would also like to thank my course colleagues for all the friendship and help through these years I am deeply in debt with my girlfriend Dina for the uncountable reviews for the infinite patience for everything Thank you I am forever grateful to you Finally my family without whom I wouldn t be where I am for sure Thank you In s Duarte L nea Silva and Fernando Silva il Resumo Com o objectivo de melhorar a detec o precoce do cancro da mama foram desenvolvidos no mbito do projecto PET Tomografia por Emiss o de Positr es os tom grafos ClearPEM e ClearPEM Sonic Ambas as unidades s o constitu
61. gnals provided by the ASICs to the Data Acquisition Electronics DAE On Figure 2 4 an half Super Module all assembled is presented The Super Modules also include temperature sensors to monitor the temperature of the photodiodes in order to operate in a stable and uniform temperature The APDs performance is heavily dependent on its temperature Modules 12x32 crystals 24 APDs Frontend Board ASICs 2x192 channels Figure 2 4 Twelve detector modules between two FEBs forming a half Super Module 2 1 2 ClearPEM Service Board The SB is responsible for providing the low voltages for the FE and specifically the threshold voltages to the ASICs It also provides the HVs for the APDs biasing The temperature information on the detector head is measured by the SB and sent to the Detector Control System DCS The SB of the ClearPEM scanner has one power supply with 3 3 V one power supply with 5 V and four power supplies with 500 V In order to provide the 32 threshold voltages to the ASICs a 32 channel DAC is used This DAC has an I C communication port and the output voltage is set through IC commands To provide the HV to the APDs biasing the SB has 32 HV regulation circuits The output voltage of these circuits is controlled by a 32 channel DAC that is equal to the one used to provide the threshold voltages The HV circuits output has a linear response to the output voltage of the DAC Since each head has 192 arrays of APDs
62. green the communication with the chiller is OK If the led is dark green the communication with the chiller is not functioning 3 Set Limits This button allows the up and down limits of the chiller alarm The upper limit and lower limit controls are used to set the alarm values The Set limits button must be pressed to confirm the new limit values 4 Chiller status Figure 2 Kodiak chiller control graphical interface Off Green Chiller ON Red Chiller OFF 73 Auto fill Green Chiller Auto fill OFF Red Chiller Auto fill ON Low temperature Green Chiller water temperature OK Red Chiller water temperature low Low Flow Green Chiller water flow OK Red Chiller water flow low Heater Green Chiller auto heater OFF Red Chiller auto heater ON Overt Temperature Green Chiller water temperature OK Red Chiller water temperature too high Low level Green Chiller water level OK Red Chiller water level low Expansion relay 1 Green Chiller expansion relay 1 OFF Red Chiller expansion relay 1 ON Condenser Relay Green Chiller condenser relay OFF Red Chiller condenser relay ON Cool valve Green Chiller cool valve OFF Red Chiller cool valve ON Expansion Relay 2 Green Chiller expansion relay 2 OFF Red Chiller expansion relay 2 ON Low resolution Green Chiller display in Celsius Red Chiller display in faraneit Kodiak chiller connected Push to disconnect If the Kodiak chi
63. ic signals The output analog electric signals are then digitized by on board Analog to Digital Converters ADCs The FE also include temperature sensors which the resistance changes according to the temperature The DAE selects the relevant information generated by the FE The power supply voltages for the FE sub system are provided by another electronic board the Service Board SB The SB provides the high voltages HV for biasing the APDs and low voltages LV for ASICs and other integrated circuits ICs The SB is powered by LV and HV power supplies The voltages at the FE temperature sensors terminals are acquired by ADCs also in the SB The SB is monitored and controlled by the Detector Control System DCS 7 which is also responsible for monitoring and control the ClearPEM power supply system the FE and the DAE The DCS is a software that runs in a computer Service Manager which is connected to the controlled HW The DCS main functions are to switch ON OFF the ClearPEM and to detect problems in the HW of the detector This software has shown stability problems which limit its clinical use In fact the DCS crashed during its utilization Modifications were necessary to allow its clinical use As the new scanner the ClearPEM Sonic has a different hardware it was necessary to re implement the DCS for it Besides previous functionality the DCS also controls the cooling system This thesis addresses both issues The work done
64. in the scope of this thesis concerns the improvement of the ClearPEM DCS and the implementation of the DCS for the new ClearPEM Sonic The thesis presents an analysis of the ClearPEM DCS and the implemented modifications to improve its stability and therefore its clinical use It also presents the implementation of the DCS for the ClearPEM Sonic 1 2 Objectives The objective of this dissertation is twofold Firstly to analyze and improve the software of the ClearPEM DCS in order to allow its clinical utilization Secondly to develop the DCS software for the ClearPEM Sonic scanner The new DCS besides being able to monitor and control the SB power supplies the FE and the DAE also controls the new SB and the cooling system The DCS must be able to turn ON and The consortium is composed of several institutions LIP Laborat rio de Instrumenta o e F sica Experimental de Part culas INEGI Instituto de Engenharia Mec nica e Gest o Industrial INESC ID Instituto de Engenharia de Sistemas e Computadores Investiga o e Desenvolvimento INOV INESC Inova o IBEB Instituto de Biof sica e Engenharia Biom dica IBILI Instituto Biom dico de Investiga o de Luz e Imagem and HGO Hospital Garcia da Orta turn OFF all the hardware It must have a long term stability crash recovery and an easy to use graphical interface to a clinical user Also regarding the ClearPEM Sonic the last objective of this thesis is to calibrate the
65. l of the ClearPEM design with the incorporation of an Ultrasonography detection system Moreover the ClearPEM Sonic presents some upgrades regarding the electronics scintillator crystals and robotics The ClearPEM detectors include two detector heads supported by a mechanical system which allows its movements in several directions On Figure 2 2 the detectors are presented The heads are constituted by arrays of scintillator crystals optically linked to APDs that convert the optical signals in electric signals The electronic to process the electrical signals is the Frontend electronics FE The detectors heads are also equipped with a Service board SB that is responsible for providing the voltages to the FE and to measure the temperature and three cooling plates The next sections describe the detectors heads the power supply systems the electronics and software of the data acquisition system Two antiparallel 511 keV Y photons emitted Detector Positron combines with e electron and annihilates Mg Radio tracer decay Figure 2 1 The process of positron emission and subsequent positron electron annihilation results in two photons emitted 180 apart Detector Detector Heads Figure 2 2 ClearPEM and ClearPEM Sonic detector heads 2 1 Detector Heads The detection of the emitted photons takes place on the detector heads On Figure 2 3 the composition of the detector heads is presented Each head has four Super Mod
66. ller has any problem and has to have manual control This button allow the Service Manager to work without controlling the Kodiak chiller 74 3 Kepco Power supply control Menu The Kepco power supplies are controlled from this menu From here is possible to turn ON OFF the power supply to monitor the output voltage current and to call the advanced menu Fig 3 shows the menu graphical interface Module Module Module 3 Module4 Module Module Module7 Modules Ly a mi o Figure 3 Kepco power supply control graphical interface 1 Power ON OFF If Kepco power supplies are ON by pushing this button Kepco are turned OFF If Kepco are OFF by pushing this button Kepco are turned ON 2 Advanced Menu The Kepco control advanced menu is called by pushing this button 3 Modules monitoring If the green led is light green the output is ON If the led is dark green the output is off In the voltage and current indicators the output voltage and current can be monitored 15 Kepco advanced control menu This menu allows the user to have a more complete control and monitor of the Kepco power supply 1 Advanced monitoring modules Are composed of 8 monitoring modules number of Kepco modules allowed in the rack Each monitoring module is composed of 7 indicators Channel Indicates if the output is ON light green or OFF dark green Real Voltage Indicates the output voltage Max Indicates the maximum allowed out
67. main menu The graphical interface is presented on page 83 of the User Manual In order to detect malfunctions in integrated circuits an advanced menu was developed If any of the ICs that communicate with the FPGA stops responding it has to be replaced The created menu points in a SB photograph the damaged IC This menu can be seen on page 85 of the User Manual The output off all the channels of the eight DACs are monitored using eight ADCs To perform a visual monitoring a graphical interface with several indicators was created page 86 of the User Manual The indicators present the measured voltage of the threshold voltages and also the desired output voltage In the case of the HV regulation circuits the presented values correspond to the high voltage value The 34 value measured by the ADC is converted into an high voltage using the calibration values Chapter 5 If the output voltages differs more than 1 from the desired voltages the background of the indicators starts to blink in order to alert the user This graphical warning makes the detection of wrong voltages easier 4 3 2 Cooling Control and Monitoring To control the Kodiak chiller 18 commands are sent through the RS 232 interface and the respective responses are processed by the DCS Control and monitoring the cooling system includes turn ON OFF the chiller e monitor the water temperature at the output of the chiller e monitor the internal status of
68. ment of the ClearPEM Sonic Detector Control System 4 1 Developing Environment 0 20 00002 ee ee 4 2 DCS Architecture iese ce ee ee A A a eS 4 3 Control and Monitoring Software Modules 2 0000 4 3 1 New Service Board Control and Monitoring 02 4 3 2 Cooling Control and Monitoring oaa 0 002020 000 4 3 3 Main Menu amp Warning System 02 020 00004 4 4 TestsandResults 2 2 2 0 0 a ee 44 Test Bench sata do AUS ee Re Re Bb ek Bake ja 5 ClearPEM Sonic Service Boards Calibration 3 1 DAGS Calibration sa sega vi dar eis eal ee di PS Here ah ee Mecca al dad se b gt Maa alate allo 5 2 HV Regulation Circuits Calibration 2 2 0 00 2 0 000020 000 4 5 3 SMs Temperature Monitoring Calibration 2 0000 6 Conclusions Bibliography Appendix 13 13 15 17 20 20 20 21 21 22 24 27 28 28 30 31 35 37 38 38 38 59 63 65 2 1 22 2 3 2 4 2 5 2 6 2 7 2 8 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 4 1 4 2 4 3 4 4 4 5 4 6 List of Figures The process of positron emission and subsequent positron electron annihilation 6 ClearPEM and ClearPEM Sonic detector heads 2 20000 6 Detector head composition ooa ee 7 Twelve detector modules between two FEBs forming a half Super Module 7 The ClearPEM Sonic SB with the HV adapter mezzanine matrix 9 The Kodiak recircula
69. menu is shown the voltages currents and temperatures of the components of the DAQ boards and the TGR DCC board x lt A 77 Figure 12 DAE monitoring Menu The TRG DCC indicators are the following ones 3 3 Voltage amp VCC EEPROM FPGA voltage FPGA current FPGA temperature Board Temperature Sey The 4 DAQ boards have the following indicators 6 3 3 Voltage amp VCC EEPROM 7 FPGA 1 amp 2 voltages 8 FPGA 1 amp 2 currents 9 FPGA 1 amp 2 temperatures 10 Board 1 amp 2 Temperatures 87 DAE crate monitoring menu In this menu is presented the voltages temperatures and fans speed of the DAE crate Advanced control menus can be called from this menu Figure 13 DAE crate monitoring and control menu 1 Advanced Menus buttons When one of this buttons is pushed an advanced control menu pops UP 2 Voltages monitoring Here is presented the voltages in the DAE crate Upper and lower limits are also presented 3 Temperature limits regarding fan speed The temperature limits control the speed of the fans These limits can be defined by calling the advanced menu 4 Temperature sensors monitoring The temperature measured by the sensors is shown in these indicators 5 Fan information The number of fans is shown The speed of the fans in percentage is presented And finally the current speed is also shown 88 DAE crate limits menu In this menu the limits of the alarm
70. mplemented The temperature and humidity sensor indicators are located in the bottom part of the SBs monitoring The Dew Point indicator shows the dew point temperature 32 ON Set the DACs voliages All voliages set to O V Service Board control and monitoring starts over Figure 4 4 Service Boards control and monitoring flowchart DCS goes to Error State 33 For a visual monitoring of the temperature in the SBs six pixelized maps were created three for each SB For an easy temperature reading by the user a color scale was also created The color scale indicator can be seen at the right side of the bigger maps The biggest map represents the temperatures read in the eight sensors of the SB The temperature indicators placed on the map match the location of the sensors in the SB It is a pixelized map composed of 5 x7 pixels with information about 8 pixels number of sensors So the remaining pixels present a temperature that is the mean temperature of the closest sensors The smaller maps represent the temperature in the Super Modules both in top and bottom Frontend Electronic Boards FEBs The SM maps have 4x4 pixels and each pixel matches a PT100 temperature probe As mentioned before four advanced menus were also created These menus allow an advanced control and monitoring of the SBs The HV SETUP MENU allows an individual control of each HV regulation circuit The output voltages of the circuits can
71. nal statuses of the chiller are presented in form of square indicators Finally two indicators and one button to change the temperature limits were implemented 4 3 3 Main Menu amp Warning System The Main Menu allows to control and monitor all the hardware sub modules of the detector The Main Menu of the ClearPEM DCS was also modified in order to be used in the ClearPEM Sonic DCS The graphical interface of the DCS main menu is shown on page 69 of the User Manual As it can be seen the status panel has the warnings that refer to the new DCS monitoring functions If the monitored statuses have a problem the correspondent indicator is red otherwise is green The critical warnings of the Kodiak chiller monitoring are also shown in the menu the warnings concern e lost of communication e temperature too low e temperature too high e low water level e low water flow If the temperature inside the chiller is not in the allowed limits the warnings turn red If the water level or the water flow are not correct the warnings turn red Concerning both SBs in the status panel the presented warnings are e lost of communication e temperature inside outside the limits e humidity inside outside the limits e right wrong high voltage values e right wrong threshold voltages 37 If the temperature in any of the SBs is outside of the defined limits the indicators turn red otherwise they are kept green If the Dew Point tempera
72. nd offset error values However in this case the method calculations are not based on the full scale of the DAC range Due to the circuit architecture the minimum output voltage of the regulation circuit is around 140 V which corresponds to 1 07 V at the DAC output The maximum output voltage is around 500 V which corresponds to 3 8 V at the DAC output After calibrating the HV regulation circuits the gain and offset values are obtained These values are used in Eq 5 3 where x is the value written in the DAC y is the desired output HV b is the offset value obtained from the calibration and m is the gain value obtained from the calibration So using Eq 5 3 with the values obtained from the calibration the HV regulation circuit output voltages are the desired ones 46 X 1 2 V A Set DAC with X E Wait 5 s Measure and save voltage e Ramp down DAC Figure 5 7 DACs calibration software flowchart Calibration Software This calibration software is similar to the one used to calibrate the DACs It sets a set of voltages 1 2 V to 3 8 V in the DAC and measure the output voltages of the HV regulation circuit The set and measured values are stored in a file for future analysis Between the setting and the measuring of the voltages it exists a waiting period of 5 seconds This is for the output voltage to stabilize When the DAC voltage reaches the 3 8 V the software ramps it down to 0 V The ramping down is
73. ol votlages of the HV regulation circuits To monitor the temperature the SB has eight built in temperature sensors These sensors are evenly placed throughout the SB in order to monitor the maximum percentage of the board space A humidity and temperature sensor to ensure the detection of a water leak was also introduced in the new SB The control of the SB integrated circuits is made through I C protocol with a FPGA To communicate with the FPGA two types of connectors are available DB 9 for RS 232 and a shielded RJ45 for 10 100 Mbps Ethernet To communicate with the integrated circuits without using the FPGA for debugging purposes the SB has an I2C connector This SB has also two 3 3 V supply lines and one 5 V supply line 2 1 4 Cooling System The Super Modules and the SB dissipate almost 100 W Therefore they contribute to the increase of the detector heads temperature One cold graphite and two cold aluminum plates are used to reduce the temperature in the detector head The graphite plate refrigerates the bottom part of the Super Figure 2 5 The ClearPEM Sonic SB with the HV adapter mezzanine matrix Modules one aluminum plate refrigerates the top part of the Super Modules and the other aluminum plate refrigerates the SB The plates are crossed by pipes which carry water with a temperature around 18 C cooled down by a recirculating chiller On Figure 2 6 the chiller is presented On Figure 2 7 the graphite plate attached to a d
74. onitor sub module software is presented on Figure 4 5 The internal status monitoring is divided in two parts the critical internal statuses and the non critical internal statuses The critical statuses concern the temperature inside the chiller the water level and the water flow During the monitoring if the chiller reports an error about these four statuses the DCS is forced into the Error State The non critical statuses regard the status of internal components of the chiller The monitoring of these components is only for informative purposes only indicating if the component is active or inactive 35 Chiller connected Turn ON OFF Figure 4 5 Cooling control and monitoring flowchart 36 Among all the hardware modules that communicate with the DCS the chiller is the only hardware module that can be manually controlled If the communication between the DCS and the chiller fails the DCS must continue to work in a normal way Therefore this sub module permits to stop the communication with the chiller The software assumes that the chiller is turned ON and the DCS continues to work normally The graphical interface of the cooling control and monitoring sub module is presented on page 73 of the User Manual It can be seen the turn ON OFF button and the button to choose if the DCS works with the chiller connected or disconnected The values of the actual temperature set temperature and the pressure are presented The inter
75. onitor the humidity temperature sensor e to monitor the 64 temperatures of the Super Modules On Figure 4 4 the implemented flowchart to control and monitor the SBs is presented As it can be seen on Figure 4 4 the control and monitoring module only communicates with the SB if the Kepco power supplies are turned ON Otherwise it waits for the power supplies to be switched ON After the power supplies are turned ON the software checks if the temperature in the SBs is between the allowed limits The temperature limits are between 18 C and 25 C which correspond to the Avalanche Photo Diodes working regime If the temperature in the SBs is not inside the limits the software waits for the temperature to reach the limits the cooling system is working for 10 minutes If the temperature is not reached within the 10 minutes the system is turned OFF If the temperature is inside this working regime the software continues to work normally and starts to monitor the two SBs From the temperature and humidity measured by the humidity sensor the dew point temperature is calculated This calculation indicates for a given humidity the temperature that the SBs have to be in order to the water vapor to condensate If the measured temperature is equal to the dew point temperature the water vapor starts to condensate Due to the sensor temperature accuracy 0 5 C 17 the humidity warning is activated when the two temperatures have a difference o
76. or long periods of time several test runs were done These different tests were conducted e using the DCS for long periods of time e turning ON and OFF the whole system several times e turning ON and OFF each hardware sub system several times DCS was proven to be stable working without crashing or stop responding for twelve hours test runs The twelve hours runs were chosen to assure that DCS can be used during an entire day without being shut downed Turning ON and OFF the whole detector to assure that the DCS can work without crashing with constant handling For the same purpose several tests where each hardware sub module was turned ON and OFF were taken The DCS worked without any problems during the tests All the new functions of the DCS were tested These tests consisted on using all the developed and implemented functions concerning the SBs menus and the Cooling menu To test the capability of DCS to handle errors the test software used to test the ClearPEM DCS was adapted to test the new DCS This software purpose is to force errors in the DCS For this purpose the test software has global variables that are shared with the DCS These variables represent simulated statuses of the hardware sub modules The simulated statuses concern the output voltages internal status and temperatures The test software user can choose if the DCS reads the real values or the simulated ones On Figure 4 7 the graphical interface is pres
77. perature of 0 C the PT100 has a resistance of 100 Q 9 Resistance Q Temperature C 103 90 10 107 79 20 109 73 25 Table 5 3 Resistance values and correspondent temperature In order to have the correspondence values between the resistance and the temperature the high precision resistors are connected to the signal conditioner pair by pair The 3 different voltages are measured and due to the probes linear behaviour a linear fit is performed From the linear fit the voltage to temperature conversion values are obtained The calibration has to be performed on all 32 temperature reading channels This is due to the different resistance values between the signal conditioners and the ADCs The different resistance values have origin in the different paths between the SMs connectors and the ADCs On Figure 5 15 the different paths between the connectors 1 2 3 4 and the ADC in the SB are shown On Figure 5 16 the circuit to measure the temperature on the PT100 probes is presented Rp refers to the parasite resistance between the PT100 probe and the signal conditioner and also between the ADC and the signal conditioner After calibrating the temperature reading channels the calibration constants m and b are obtained These values are used in 53 PT100 PT100 Figure 5 16 Measuring temperature circuit x y b m 5 4 where x is the temperature in the probe y is the read voltage b is the
78. put voltage Voltage level Indicates the set voltage Real current Indicates the output current Max I Indicates the maximum allowed output current Current level Indicates the set current 2 Output control buttons With these control buttons the output of each one of the Kepco modules can be controlled Channel Choose Set the channel to control Voltage control Set the output voltage Channel State Set the output ON OFF Current Set Set the maximum output current 3 General control buttons Clean errors The errors status leds are re seted to a no error state Refresh Refresh the monitoring values and status Stop Close the advanced menu 4 Kepco internal status monitoring leds The seven indicator leds inform about the internal status of the Kepco power modules If a led is light green an error as occurred If a led is dark green the status is normal Power loss Kepco has lost its power supply Overload The load impedance is bellow Set Voltage Current Limit Relay Error The sense wires become disconnected from the power leads OverTemp Temperature inside the Kepco modules is too high Current error f the output current is not a programmed value Voltage error f the output voltage is not a programmed value Current mode f operation mode is in current mode 76 SS NATIONAL Figure 4 Kepco power supply advanced control menu 77 4 ISEG power supply control Menu The ISEG power suppli
79. r specifications some critical notes Proc of 14th IMEKO International Symposium on New Technologies in Measurement and Instrumentation and 10th Workshop on ADC Modelling and Testing 1 81 86 2005 Bill Jasper Practical telecom dac testing www testedgeinc com Online 2010 Keithley Instruments Inc http www keithley com products dcac dmm broadpurpose mn 2000 Online 2010 64 23 P Lousa J Nobre J C Silva J Varela P Amaral M Ferreira Service board specification document version 1 2 March 2006 24 R Bugalho B Carri o C S Ferreira M Frade M Ferreira R Moura J Neves C Ortig o J F Pinheiro P Rodrigues I Rolo J C Silva R Silva A Trindade and J Varela Characterization of avalanche photodiode arrays for the clearpem and clearpem sonic scanners Journal of Instrumentation 4 P09009 2009 25 Maxim Max6603 dual channel platinum rtd to voltage signal conditioner http datasheets maxim ic com en ds max6603 pdf Online 2010 26 National Semiconductor Madc101c027 http www national com ds dc adc101c021 pdf Online 2010 65 66 Appendix O Service Manager User Manual PET PEM Service Manager Main Menu Cooling control Menu Kepco Power supply control Menu ISEG power supply control Menu Service Board control Menu DAE control Menu 67 68 73 75 78 81 87 1 Service Manager Main Menu The status of all the components of the detector can be monitored in this m
80. rder to have precise threshold voltages the DACs in the SB were calibrated The calibration is necessary due to the gain and offset errors that exist at the output of the DACs The process used to calibrate the DACs is the best fit method where values are set and measured and a linear fit is performed The gain and offset values obtained from the linear fit are used to correct the output errors After calibrating the DACs the maximum output error is 3 mV which corresponds to an error of 0 18 For the APDs to work in the desired condition an accurate high voltage for biasing the APDs is of most importance To assure that the output voltages of the HV regulation circuits are the desired ones all the channels were calibrated To calibrate the HV regulation circuits a set of voltages were set at the control DACs output and the HV channel voltages were measured A linear fit was performed with the measured values and the gain and offset values were obtained The obtained values were applied to set at the HV regulation circuits output the desired values to bias the APDS and a maximum difference of 230 mV was observed which means an error of 0 055 A controlled temperature in the detector heads is necessary for the APDs to work properly so it was necessary to calibrate the temperature measuring system This calibration set a correspondence between the voltage measured in the temperature probes and the temperature All the PT100 probes reading chann
81. rents and temperatures Finalization consists on the elimination of semaphores that are used by the Hardware control The control termination is taken when the DCS is turned OFF and all the communications are terminated The DCS architecture is presented on Figure 4 1 In the presented architecture is given more emphasis to the hardware control because it is the most complex and critical part of the DCS DCS State Machine The state machine Figure 4 2 ensures the correct order of switching ON OFF the hardware sub systems The state machine has a new state Cooling State in order to include the control of the Kodiak chiller This state is located between the idle state and the stop state In Table 4 1 the hardware sub systems 28 Control initialization Kodiak chiller ISEG power supplies DAE monitor initialization initialization initialization Kepco power supplies Service Board initialization initialization Monitor amp control Figure 4 1 The new ClearPEM Sonic DCS architecture 29 status regarding the DCS States are presented The introduction of this state ensures that the Kepco power supplies can only be turned ON if the Kodiak chiller is turned ON This is necessary because the heat originated by the power dissipated on the detector heads total of 100 W has to be removed When the DCS is in this state the Kodiak chiller is turned ON and the remaining hardware of the detector is kept OFF If the temperature in the
82. rol menu SB Status In this menu is shown if any ADC or DAC is disconnected In the following figure is shown the graphical interface of the menu A picture of the SB is shown in order to facilitate the physical detection of the damaged IC ServiceBoard 1 Service Board O 85 1 Exit button Pushing this button closes the menu 2 Global status indicator Here is indicated if the SB is OK or has any problem If OK the indicator shows SB fully functional If not OK the indicator shows Problem detected 3 IC status indicators These indicators show which IC has problems If alC has a problem it is indicated with an arrow highlighted with a square and the matching label in the SB is shown 4 SB picture It is used a picture of theSB in order to make easy the detection of the ICs Vth and HV DAC monitoring Menu In this menu the DACs output voltage can be monitored If the output value of one channel is 10 different of the set value the background of the DAC indicators start to blink In Figure 11 is presented the menu I E o Es LJ ms THT TT TOTTE THT Te TITIL LIE CS TEETE TEETE TEETE THT TTT TT Ie TEETE TEETE TEETE TEETE CIT TITTITTIE TTT Te TIETE Me TTT TT IE TATT TTT TITITIL TTL TEIT TEETE TITITITIE TITE ST TTT TTT a STITT TT TTT TETIT re Fi Figure 11 Vth and HV DACs monitoring menu 86 6 DAE control Menu In this
83. s Voltage Measured Output voltage Set Set Voltage Nominal Nominal Voltage Current Measured Output current Set Set current Trip Trip current Nominal Nominal current 4 Output control buttons With these control buttons the output of each one of the ISEG modules can be controlled HV channel Set the channel to control Channel State Set the output ON OFF Current Set Set the maximum output current Current trip Set the maximum output current Voltage set Set the output voltage 5 General control buttons Monitor refresh Set the menu refreshing period Record period Set the values recording period Ramp Set the ramp value V s Apply Apply the modifications 6 ISEG internal status monitoring The indicators inform about the internal status of the ISEG power modules Temp ISEG internal temperature 24 V 24 V power supply line value 15 V 15 V power supply line value 5 V 5 V power supply line value 5 V 5 V power supply line value 79 i i r gt z a D i y pa i Y amp ei lois g i O ATONAL RUNEN Figure 6 ISEG power supply advanced control menu 80 5 Service Board control Menu This menu allow the user to control and monitor the two Service Boards The monitoring is in terms of temperature and humidity In Figure 7 is presented the graphical interface of the SB menu 1 Turn ON OFF button If the SBs are ON by pushing this button they
84. s can be set These limits are in terms of voltages and temperatures To apply the modification the button APPLY and EXIT has to be pushed Jo C 7 NATIONAL DO INSTRUMENTS APPLY and EXIT tay suf vere Figure 14 DAE crate configuration menu DAE fan speed menu In this menu the speed of the fans can be configured in terms of throttle At 100 the fans are in full throttle To apply the modification the button APPLY and EXIT has to be pushed at is sv Davis Avare Figure 15 DAE crate fan speed menu 89
85. sys Medical PET Imaging Sysems pPoOSDOSCODSS SERVICE BOARD 1 Temperature C SERVICE BOARD 2 Temperature C I I HV SETUP l MENU i I I I pPoOoDDoOS So FEBs top Vth SETUP MENU FEB Temperature MENU MEE FEBs bottom SB status CEO e I Humidity Temperaturq 0 Jo NM DEW point l I Figure 7 Service Board control graphical interface FEBs temperature Menu This menu allow the user to have a more accurate monitoring of the temperature in the FEBs Each half super module has two read sensors 1 FEBs Top mapping This pixelized map indicates the temperature in the top FEBs Each indicator matches a Super module temperature probe 2 FEBs bottom mapping This pixelized map indicates the temperature in the bottom FEBs Each indicator matches a Super module temperature probe 3 Exit This button allow the user to close the menu 82 SERVICE BOARD Q FEBs temperature Menu p Taaie p Seivicemaatat sj Service Board 2 57 PETsys ea Tey ieee Figure 8 FEB temperature monitoring menu Vth Setup Menu With this menu is possible to control each one of the Vth values Set new default values and restore the old ones 1 Apply changes By pushing this button the values in the indicators are set into the Vth DACs Exit Pushing this button closes the menu Threshold values Service Board 1 and 2 Vths is a value that is
86. t software graphical interface Figure 3 9 The test bench With both Kepco and ISEG power modules ON the following tests were performed Stimulus Simulation of ISEG Crate internal status errors wrong internal voltages and temperatures Results DCS goes to error state turns OFF KEPCO and ISEG After the error disappear goes to idle state Stimulus Simulation of ISEG voltage and current wrong output Results DCS goes to error state turns OFF KEPCO and ISEG After the error disappear goes to idle state Stimulus Simulation of Kepco internal status errors power loss over load relay error over temperature current error and voltage error Results DCS goes to error state turns OFF KEPCO and ISEG After the error disappear goes to idle state Stimulus Simulation of Kepco voltage wrong output Results DCS goes to error state turns OFF KEPCO and ISEG After the error disappear goes to idle 24 state Stimulus Simulation of the SB temperature out of bounds Results DCS goes to error state turns OFF KEPCO and ISEG After the error disappear goes to idle state Stimulus Lost of connection with the Kepco controller Results DCS goes to error state turns OFF ISEG After the communication is reestablished turns OFF Kepco and to goes idle state Stimulus Lost of connection with the ISEG controller Results DCS goes to error state After the communication is reestablished turns OFF Kepco and to goes idle state
87. t voltage is 1 68 V in all DACs channels which is the threshold voltage for the circuits implemented in the ASIC The values were set and measured in both Service Boards in order to evaluate the DACs accuracy The measured values show a systemic bias less than 0 18 which represents a maximum diference between the set and measured voltage of 3 mV The R squared values are between 0 99999 and 1 which shows the linearity of the points Ww 3 ba un uw i DAC output Volt ta o w e jo 0 2 0 6 1 14 18 22 26 3 DAC set Voltage Volt Figure 5 5 Typical DAC channel calibration curve Service Board 0 Service Board 1 TOP FEBs V Bottom FEBs V TOP FEBs V Bottom FEBs V 1 678 1 682 1 682 1 680 1 678 1 681 1 677 1 678 1 677 1 681 1 677 1 678 1 681 1 681 1 679 1 678 1 681 1 681 1 681 1 678 1 682 1 677 1 681 1 680 1 679 1 679 1 682 1 680 1 677 1 679 1 680 1 681 1 677 1 678 1 682 1 680 1 677 1 682 1 677 1 682 1 677 1 681 1 677 1 680 1 682 1 681 1 680 1 678 1 678 1 679 1 679 1 678 1 682 1 679 1 680 1 678 1 678 1 681 1 678 1 678 1 681 1 680 1 680 1 680 Table 5 1 Voltages measured at the DACs output 45 5 2 HV Regulation Circuits Calibration An HV regulation circuit is composed of two operational amplifiers one optocoupler resistors capacitors and Zener diodes Figure 5 6 arranged in a linear topology so that the output of the HV regulation circuit has a linear response to the output
88. ta tese consistiu no estudo e revis o do software deste sistema Foi efectuada uma revis o pol tica de alarmes aos protocolos de comunica o monitoriza o das tens es de sa da das fontes de alimenta o e tamb m monitoriza o da temperatura das cabe as detectoras A revis o tornou o sistema est vel e utiliz vel em ambiente cl nico Posteriormente o sistema de controlo e monitoriza o do ClearPEM foi adaptado para o ClearPEM Sonic Para al m das fun es anteriores nclui o controlo e monitoriza o do sistema de arrefecimento Para controlo e monitoriza o da placa de servi o do ClearPEM Sonic o DCS foi tamb m alterado Palavras Chave Mamografia por emiss o de positr es Sistema de controlo e monitoriza o Calibra o de hardware lil Abstract In order to improve early breast cancer detection the ClearPEM and the ClearPEM Sonic scanners were developed within the PET Positron Emission Tomography consortium Both units are composed of two planar detector heads supported by a robotic arm and a trigger and data acquisition system Each head is composed by 96 arrays with 32 crystal scintillators The radiation emitted by the human body due to the injection of a radioactive substance in the patients is detected by crystal scintillators which transform the radiation into light This light is converted into electric signals by avalanche photodiodes APDs Amplification and processing of the sign
89. the 64 DAC channels 18 e measure the mean and individual temperature of the PT 100 temperature probes e measure the scanner head pressure The HV regulation DAC configuration is done by ramping up the voltages in a controlled rate because the HV regulation circuits final output voltage are between 370 V and 470 V and a sudden transition between O and 470 V could damage the circuits The ASICs threshold DAC configuration is only made in one step because its output voltages do is not bigger than 5 V On Figure 3 5 the graphical interface of the SB control and monitoring is presented In this menu pressure and temperature can be monitored threshold voltage and APD bias voltage can be seen and the individual menus can be called Figure 3 5 SB menu graphical interface The individual menus are available only in stand alone mode Vth SETUP MENU allows to change the threshold voltages for the ASIC circuits HV SETUP MENU allows to change the APDs bias voltage And Temperature MENU allows the visualization of each FEB temperature DAE Monitoring To communicate with the DAE it is used RS 232 The DAE monitoring is divided in two sub modules One sub module is responsible for monitoring the four Data Acquisition DAQ boards and the Trigger and Data Concentrator TRG DCC board voltages currents and temperature The other sub module is responsible for the DAE crate voltages current and temperature monitoring an
90. the ClearPEM scanner with some improvements on the electronic system To control its hardware the DCS of the ClearPEM was adapted The control and monitoring software sub modules of the low voltage power supplies high voltage power supplies and DAE were re used The software sub module for controlling and monitoring the Service Boards and the cooling system were developed from scratch Due to the introduction of the cooling control and monitoring the State Machine of the DCS was modified Another state was added where the chiller is the only sub system turned ON The state machine only allows the other hardware sub modules to be turned ON if the chiller is already turned ON The control and monitoring of the Service Boards is responsible for setting the DAC output voltages reading the voltages measured by the ADCs reading the temperature sensors and read the humidity sensor The software does not allow the scanner to work if the temperature and the humidity are not inside the allowed limits To monitor the temperature pixelized maps with a color grade were created turning the temperature monitoring an easier function to the user To assure a constant temperature inside the Detector Heads the software that control and monitors the chiller is responsible for setting it to 18 C Besides this the software is also responsible for monitoring the water temperature level and flow among other internal status The DCS was submitted to robus
91. ting chiller oaa ee ee 9 The graphite chiller plate assembled on the detectorhead 9 ClearPEM power distribution architecture 2 2 ee eee 10 ClearPEM communication architecture 2 ee ee 14 Representation of the DIM protocol 2 2 0 000200 eee ee 15 The DES State Machine i y cede ae Ge oe os RA bee ee A beek 16 DCS main menu graphical interface 2 ee ee 17 SB menu graphical interface 2 a 19 SB new menu graphical interface 2 2 a 22 DCS new main menu graphical interface 2 2 0 2 0000000004 23 The test software graphical interface 2 2 ee ee 24 TPhe test benchs sr Leia ay eh kas eh ah A ede ae a ae ee ae eee 24 The new ClearPEM Sonic DCS architecture 2 0 2 2 2 0 0000 29 The new DES state machine sas eo a e oa ede a ae a 30 ClearPEM Sonic DCS communication protocols and interfaces 31 Service Boards control and monitoring flowchart 4 33 Cooling control and monitoring flowchart 2 2 0 0 2 002020000 36 Detector Control System test bench 2 2 ee 38 4 7 5 1 5 2 5 3 5 4 5 5 5 6 5 7 5 8 5 9 5 10 5 12 5 13 5 14 5 15 5 16 5 17 5 18 5 19 5 20 5 21 5 22 Test software graphical interface o oo ee Graphical representation of the DAC different outputs oaoa DACs calibration software flowchart oaaae Graphical interface of the calibration software
92. tness and functionality tests The DCS was used for long periods of time and were tested its functions during these tests The DCS showed a long term stability because it did not crashed and its functionalities worked every time To test the functionalities of the DCS a software that simulated errors was adapted from the one used for testing the ClearPEM DCS The tests covered all the errors that could occur during the DCS utilization The DCS is capable of recognize all the errors of the hardware and also the communication failures The DCS is a stable and robust software capable of controlling and monitoring the detector hardware At the time of writing this thesis the ClearPEM Sonic is being assembled Further tests of the DCS will be made during the final integration phase 60 ClearPEM Sonic Service Boards Calibration The service Board has in the ClearPEM Sonic a central role since it provides the low and high voltages to the Frontend electronics as well as important monitoring features The success of an high density channel more than 12000 channels APD PET system is directly linked to the degree of precision stability and control of the high voltage regulation circuits and temperature monitoring This makes the calibration process an essential step in the integration phase A precise threshold voltage for the ASICs circuits allow the correct processing of the electric signals originated in the detection of photons by the APDs In o
93. to the Kepco output voltage error detected by the DCS HV current error and voltage error refer to wrong output current or voltage by the ISEG power supplies Temperature DH1 and DH2 now refer to the temperature in the SB instead of the FEBs mean temperature In order to increase the DCS crash recovery the state is saved in a text file If the PC or the LabVIEW crashes this file contains the state before one of the systems crash So when the DCS crashes and is turned ON automatically goes to the state saved in the text file If DCS before crashing was in a given 22 state when is turned ON if the hardware status correspond to that state the DCS goes to the correct state otherwise the DCS goes to the idle state This procedure is taken for all the DCS states On Figure 3 7 the new DCS main menu graphical interface is shown In the Status table the enumerated warnings were modified or added v gt Ld WY 7 Li P I P Figure 3 7 DCS new main menu graphical interface 1 low voltage RS 232 Refers to the communication status between the Kepco power supply and the DCS If green the communication is functioning otherwise the color is red 2 low voltage voltage error Refers to the automatic monitoring of the Kepco output voltage If the value is different from the set value the warning signal becomes red 3 low voltage current error Refers to the automatic monitoring of the Kepco output current
94. ture is equal to the current temperature the humidity sensors turn red otherwise they are kept green If the voltage measured by the ADCs is different from the set voltage in the DACs the threshold and HV warnings turn red It was also added to the main menu a led that indicates if the Kodiak chiller is turned ON or OFF Like in the other hardware sub modules when the chiller is on the led is light green when is off the chiller is dark green 4 4 Tests and Results To verify the robustness of the implemented software several tests were carried out Tests concerning the capability of the DCS to maintain operation for long periods of time Tests were also carried out to verify the capability of the DCS to process software and hardware problems 4 4 1 Test Bench A test bench was used to test the robustness of the software The test bench presented on Figure 4 6 is composed of one SB three Kepco low voltage power supplies one ISEG high voltage power supply one Kodiak chiller and one PC running the DCS The ISEG HV power supply is not connected to the SB to prevent damaging its circuits if the high voltage is fed into the SB and the low voltage is turned off part of the high voltage regulation circuits of the SB could be damaged CAN Bus ISEG K N 2 Pa ARS 232 N A Fer A RS2324 4 a RS 232 Figure 4 6 Detector Control System test bench 4 4 2 Robustness Tests In order to ensure that the DCS can work f
95. ules which are connected to a SB an high voltage HV matrix three cooling plates and several power supply cables 2 1 1 Frontend Electronics A super module is composed of twelve modules of 32 scintillator crystals arranged in a 4 by 8 matrix configuration Two arrays of 32 APDs 8 assembled on a small Printed Circuit Board are placed on the bottom and top of the crystal matrix matching its disposition 5 The crystal modules are placed between two boards that include the signal processing electronic the Frontend boards FEBs FEBs process analog signals from the photodiodes amplifying and converting them into digital signals FEBs also convert parallel data from Analog to Digital Converters ADCs to serial links Two Application Specific Integrated Circuits ASICs implement the amplifiers the sample and hold circuits and the Detector Head Cooling Plates Service Board Figure 2 3 Detector head composition threshold detectors The ASICs are capable of reading out 192 channels from 6 APDs arrays At every clock cycle the input signals are sampled and their value is stored in a memory with space for 10 values In parallel at the clock frequency each of the sampled signals is compared to a threshold voltage followed by digital logic processing to determine the channels above threshold 8 The threshold voltage is adjustable externally and is provided by the SB Digital to Analog Converters DACs FEBs send the electric si
96. ure analysis On Figure 5 2 the DAC calibration software flowchart is presented and Fig 5 3 presents its graphical interface X 0 V _ Set DAC with X Measure and Increase X save voltage et Figure 5 2 DACs calibration software flowchart Calibration Bench To calibrate the DACs beside the SB three low voltage power supplies one multimeter and one PC are used The PC is used to set the output voltages of the DACs to read the voltage measured by the multimeter and to control the low voltage power supplies The low voltage power supplies are used to supply the SB with the necessary working voltages The multimeter is used to measure the voltage at the DAC output On Figure 5 4 the calibration test bench is presented 43 Vth Calibration Pito PR output cluster 3 Multimeter RS 232 COML 2 5 E 15 SB RS 232 5 com2 Y measuremed 0 5 o V written 0 1 1 p 0 0 5 1 15 2 25 3 o Time Figure 5 3 Graphical interface of the calibration software Figure 5 4 DACs calibration test bench 44 Calibration Results On Figure 5 5 a typical calibration curve is presented From this curve the gain and offset values are obtained After performing the calibration the obtained gain and offset values are applied to Eq 5 3 The results of the application of this equation were used to set the desired voltages in the DACs In Table 5 1 the measured voltages are shown The desired outpu
97. w plays a roll on the turning ON process of the SB When the SB is turned ON the first action is to read the temperature measured by the sensors If the temperature is out 21 of limits the DCS waits 15 minutes for the cooling to act on the SB temperature If after the 15 minutes the temperature limits are not reached the DCS goes to error and the SB DACs are not configured If the temperature is correct the DACs are configured and the temperatures are constantly measured If temperatures exceed the limits the DCS goes to error and the scanner is turned OFF The SB temperature low limit is 16 C and the high limit is 25 C These temperature limits are set due to the APDs temperature working range On Figure 3 6 the graphical interface of the SB control is presented Due to the elimination of the FEB temperature reading the button to call the temperature menu and the temperature indicator bar were deleted To show the temperature in the SB three indicators were added Two of the indicators show the value measured by two sensors and the third indicates the mean value of the two sensors 1 E A x y o o o 0 o 0 Figure 3 6 SB new menu graphical interface 3 2 4 DCS Alarms and Crash Recovery The alarm system was modified Regarding the Kepco control the alarm that signals the lost of GPIB communication now refers to the lost of RS 232 communication The Low Voltage voltage error and power loss refer

Development and Implementation of the ClearPEM

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