Time Determination of BGO-APD Detectors by Digital Signal Processing for Positron Emission Tomography

Coincidence timing resolution in Positron Emission Tomography (PET) can be improved by replacing fast analog pulse shaping and Constant Fraction Discriminator (CFD) with fully digital signal processing. This can be achieved by digitizing the signal from individual detectors using 100-MHz, 8-bit Analog-to-Digital converters (ADC) and by processing the data on-the-fly in Field Programmable Gate Arrays (FPGA). Various digital filters and baseline restorers were implemented and combined with numerical least mean square fit to the data to extract the time of interaction and the energy deposited in BGO-APD detectors. An intrinsic time resolution of 7.2 ns was obtained with digital techniques. However, it is shown that bias in the timestamp estimation can be introduced by digital time discrimination techniques, which could affect the ability of digital methods to accurately estimate random event rates by the delayed time window method. Accordingly, the coincidence FWHM metric should not be the only figure of merit when comparing digital and analog time discrimination strategies.

[1]  R. Fontaine,et al.  Performance evaluation of the LabPET™ APD-based digital PET scanner , 2009, 2007 IEEE Nuclear Science Symposium Conference Record.

[2]  T.K. Lewellen,et al.  Simulation of algorithms for pulse timing in FPGAs , 2007, 2007 IEEE Nuclear Science Symposium Conference Record.

[3]  J. Czernin,et al.  Comparison of noise equivalent count rates and image noise , 2005 .

[4]  Roger Lecomte,et al.  Status of BGO-avalanche photodiode detectors for spectroscopic and timing measurements , 1989 .

[5]  J. Pratte,et al.  Performance analysis of phoswich/APD detectors and low noise CMOS preamplifiers for high resolution PET systems , 2000, 2000 IEEE Nuclear Science Symposium. Conference Record (Cat. No.00CH37149).

[6]  E. Hoffman,et al.  Measuring PET scanner sensitivity: relating countrates to image signal-to-noise ratios using noise equivalents counts , 1990 .

[7]  Application of a Digital Technique for Timing of Events From Scintillation Detectors , 2006, IEEE Transactions on Nuclear Science.

[8]  Horst Halling,et al.  A PET system with free running ADCs , 2002 .

[9]  Hao Peng,et al.  Evaluation of free-running ADCs for high resolution PET data acquisition , 2007, 2007 IEEE Nuclear Science Symposium Conference Record.

[10]  Roger Lecomte,et al.  A power efficient, low noise, wideband, integrated CMOS preamplifier for LSO/APD PET systems , 1999, 1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.99CH37019).

[11]  Yuan-Chuan Tai,et al.  Instrumentation aspects of animal PET. , 2005, Annual review of biomedical engineering.

[12]  R. Lecomte,et al.  Time determination of BGO-APD detectors by digital signal processing for positron emission tomography , 2003, 2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515).

[13]  M. Desco,et al.  Digital timing in positron emission tomography , 2006, 2006 IEEE Nuclear Science Symposium Conference Record.

[14]  Wolfgang Hennig,et al.  Time resolution studies using digital constant fraction discrimination , 2007 .

[15]  R. Fontaine,et al.  Timing Improvement by Low-Pass Filtering and Linear Interpolation for the LabPET Scanner , 2008, IEEE Transactions on Nuclear Science.

[16]  Stefano Riboldi,et al.  Adaptive digital spectroscopy in programmable logic , 2000 .

[17]  C. Bohm,et al.  Digital timing with non-stationary noise optimal filter algorithm for LSO/APD detectors , 2007, 2007 IEEE Nuclear Science Symposium Conference Record.

[18]  R. Fontaine,et al.  Architecture of a dual-modality, high-resolution, fully digital positron emission tomography/computed tomography (PET/CT) scanner for small animal imaging , 2005, IEEE Transactions on Nuclear Science.

[19]  T. Bukki,et al.  Development of an FPGA-Based Data Acquisition Module for Small Animal PET , 2006, IEEE Transactions on Nuclear Science.

[20]  Roger Lecomte,et al.  Design and engineering aspects of a high resolution positron tomograph for small animal imaging , 1994 .

[21]  J.-F. Pratte,et al.  Design of a fast shaping amplifier for PET/CT APD detectors with depth-of-interaction , 2001 .

[22]  S R Meikle,et al.  Instrumentation and methodology for quantitative pre-clinical imaging studies. , 2001, Current pharmaceutical design.

[23]  Chin-Tu Chen,et al.  Potential advantages of digitally sampling scintillation pulses in timing determination in PET , 2007, 2007 IEEE Nuclear Science Symposium Conference Record.