DocumentCode :
2555242
Title :
FPGA-based time-to-digital converter for time-of-flight PET detector
Author :
Key Jo Hong ; Ealgoo Kim ; Jung Yeol Yeom ; Olcott, P.D. ; Levin, Craig S.
Author_Institution :
Dept. of Radiol., Stanford Univ., Stanford, CA, USA
fYear :
2012
fDate :
Oct. 27 2012-Nov. 3 2012
Firstpage :
2463
Lastpage :
2465
Abstract :
We have developed a FPGA-based time-to-digital converter (TDC) that can be used for a TOF-PET block detector based on silicon photomultiplier (SiPM) photodetectors. The tapped delay line (TDL) method implemented with a dedicated carry chain structure was used to measure short time intervals. The proposed TDC, implemented in a Spartan-6 FPGA, consists of a fine time measurement block, a coarse counter, a ring oscillator and a multiplexer. The ring oscillator generates a delay chain related frequency which is used to compensate process, voltage and temperature (PVT) effects in real-time without causing dead-time in the TDC. The multiplexer allows multiple channels to share the same delay chain which effectively reduces the amount of FPGA resources. As the TDC is implemented in an shared FPGA device, which already exists in a data acquisition system (DAQ), TOF capability can be implemented easily without requiring more resources. The performance of our proposed TDC was first measured with two input pulses which were generated from a pulse generator but with different delay lengths. Timing resolution of a TDC channel is 41.6 ± 1.1 ps FWHM (17.7 ± 0.5 ps RMS). The proposed TDC was also used to measure the timing resolution of a pair of TOF-PET detector with a Hamamatsu MPPC coupled to a 3 mm × 3 mm face of a 2 mm × 2 mm × 3 mm LYSO crystal. The measured coincidence time resolution was 197 ± 4 ps FWHM which agreed with the value measured by a high speed oscilloscope (195 ± 7 ps FWHM). These results verify the feasibility of our TDC for TOF-PET applications.
Keywords :
analogue-digital conversion; data acquisition; elemental semiconductors; field programmable gate arrays; multiplexing equipment; oscillators; oscilloscopes; photodetectors; photomultipliers; positron emission tomography; pulse generators; silicon; DAQ; FPGA-based time-to-digital converter; Hamamatsu MPPC; LYSO crystal; Si; SiPM photodetectors; Spartan-6 FPGA; TDC; TDL method; TOF-PET block detector; coarse counter; data acquisition system; dedicated carry chain structure; high speed oscilloscope; multiplexer; positron emission tomography; pulse generator; ring oscillator; silicon photomultiplier photodetectors; tapped delay line method; time measurement block; time-of-flight PET detector;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE
Conference_Location :
Anaheim, CA
ISSN :
1082-3654
Print_ISBN :
978-1-4673-2028-3
Type :
conf
DOI :
10.1109/NSSMIC.2012.6551560
Filename :
6551560
Link To Document :
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