Method for Energy Calculation and Pileup Determination for Continuously Sampled Nuclear Pulse Processing

• US 20090074281A1
• Filed: 09/15/2008
• Published: 03/19/2009
• Est. Priority Date: 09/17/2007
• Status: Active Grant

• Current Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Original Assignee: Siemens Medical Solutions USA Incorporated (Siemens AG)
• Inventors: McFarland, Aaron, Newport, Danny F., Siegel, Stefan B., Mintzer, Robert A.
• Granted Patent: US 8,340,377 B2
• Time in Patent Office: Days
• US Class Current: 382/131
• CPC Class Codes: A61B 2503/40 Animals
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/037 Emission tomography
• CPC Class Codes: A61B 6/5235 combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT
• CPC Class Codes: G01T 1/1644 using an array of optically separate scintillation elements permitting direct location of scintillations G01T1/1645 takes precedence

Abstract

A method for processing events in a medical imaging device may comprise the steps of receiving analog signals from at least one PMT into an Applied Specific Integrated Circuit (ASIC) comprising a Constant Fraction Discriminator (CFD) and transmitting analog outputs from the ASIC. Further, sampling the analog outputs continuously using an Analog to Digital Converter (ADC) and transmitting digital outputs; and collecting a number of samples of the digital output during a sampling period using a Field Programmable Gate Array (FPGA) when triggered by the CFD. The method may additionally determine the energy of the analog signals from the at lease one PMT by subtracting the peak value of each signal from the baseline value of each signal, wherein the peak value is determined as an average of at least one sample taken only around the peak during the sampling period, and the baseline value is determined as an average of at least one sample taken only around the beginning or end of the sampling period.

Claims

1. An event processing module for a medical imaging device, comprising:

an Applied Specific Integrated Circuit (ASIC) configured for receiving analog signals from at least one PMT and transmitting analog outputs, the ASIC comprising a Constant Fraction Discriminator (CFD);

an Analog to Digital Converter (ADC) configured for continuously sampling the analog outputs and transmitting digital outputs; and

a Field Programmable Gate Array (FPGA) configured to collect a number of samples of the digital output during a sampling period when triggered by the CFD;

wherein the ASIC, ADC, and FPGA are further configured to determine the energy of the analog signals from the at lease one PMT by subtracting a peak value of each signal from a baseline value of each signal, the peak value being determined as an average of at least one sample taken only around a peak during a sampling period, and the baseline value is determined as an average of at least one sample taken only around a beginning or end of the sampling period.

2. The event processing module according to claim 1, wherein the ASIC, ADC, and FPGA are further configured to detect pileup if the current baseline value exceeds a moving baseline value average over a number of previous pulses by more than a predetermined threshold value.

3. The event processing module according to claim 1, wherein the number of samples is 16 and the sampling rate is 100 MHz.

4. The event processing module according to claim 2, wherein the number of previous pulses is 8.

5. The event processing module according to claim 1, wherein the number of samples is 32 and the sampling rate is 200 MHz.

6. The event processing module according to claim 2, wherein the number of previous pulses is half the number of samples.

7. The event processing module according to claim 2, wherein the number of samples is any number from 1 to 256;

the sampling rate is any number from 50 to 1000 MHz; and

the number of previous pulses is any number from 2 to 100.

8. The event processing module according to claim 1, wherein the ASIC further comprises a Time to Digital Conversion (TDC) function and pulse shaping and amplification of the received analog signals.

9. The event processing module according to claim 1, wherein the medical imaging device is a multimodal medical imaging device comprising PET, SPECT, and CT combined in the same imaging device.

10. The event processing module according to claim 1, wherein the analog outputs of the ASIC are continuously sampled using a 10-bit, 100 MHz ADC.

11. The event processing module according to claim 1, wherein a plurality of PMT signals are multiplexed to n channels and fed to said ASIC and wherein said ASIC generates n output signals;

wherein said ADC comprises n input channels and wherein said FPGA has n input channels.

12. The event processing module according to claim 11, wherein n=4.

13. A method for processing events in a medical imaging device, comprising the steps of:

receiving analog signals from at least one PMT into an Applied Specific Integrated Circuit (ASIC) comprising a Constant Fraction Discriminator (CFD) and transmitting analog outputs from the ASIC;

sampling the analog outputs continuously using an Analog to Digital Converter (ADC) and transmitting digital outputs;

collecting a number of samples of the digital output during a sampling period using a Field Programmable Gate Array (FPGA) when triggered by the CFD; and

determining the energy of the analog signals from the at lease one PMT by subtracting the peak value of each signal from the baseline value of each signal,

wherein the peak value is determined as an average of at least one sample taken only around the peak during the sampling period, and the baseline value is determined as an average of at least one sample taken only around the beginning or end of the sampling period.

14. The method according to claim 13, wherein pileup is detected if the current baseline value exceeds a moving baseline value average over a number of previous pulses by more than a predetermined threshold value.

15. The method according to claim 13, wherein the number of samples is 16 and the sampling rate is 100 MHz.

16. The method according to claim 14, wherein the number of previous pulses is 8.

17. The method according to claim 13, wherein the number of samples is 32 and the sampling rate is 200 MHz.

18. The method according to claim 14, wherein the number of previous pulses is half the number of samples.

19. The method according to claim 13, wherein the number of samples is any number from 1 to 256 and the sampling rate is any number from 50 to 1000 MHz.

20. The method according to claim 14, wherein the number of samples is any number from 1 to 256;

the sampling rate is any number from 50 to 1000 MHz; and

the number of previous pulses is any number from 2 to 100.

21. The method according to claim 13, wherein a plurality of PMT signals are multiplexed to n channels and fed to said ASIC and wherein said ASIC generates n output signals;

wherein said ADC comprises n input channels and wherein said FPGA has n input channels.

22. The method according to claim 21, wherein n=4.

21-1. A method for processing events in a medical imaging device, comprising the steps of:

receiving n analog signals multiplexed from m detectors into an Applied Specific Integrated Circuit (ASIC) comprising a Constant Fraction Discriminator (CFD) and transmitting n analog outputs from the ASIC;

sampling the n analog outputs continuously at 100 MHz using an Analog to Digital Converter (ADC) and transmitting n digital outputs;

collecting 16 samples of the n digital outputs during a sampling period of 160 ns using a Field Programmable Gate Array (FPGA) when triggered by the CFD; and

determining the energy of the n analog signals from the at lease one PMT by subtracting the peak value of each signal from the baseline value of each signal,

wherein the peak value is determined as an average of the eighth and ninth samples taken around the peak during the sampling period, and the baseline value is determined as an average of the first and second samples taken around the beginning of the sampling period.