FPGA-based digitizer for BGO-based time-of-flight PET

Area of Science:

• Nuclear Instrumentation
• Medical Physics
• Photon Detection

Background:

• Bismuth germanate (BGO) crystals produce both scintillation and prompt Cerenkov photons upon interaction with 511 keV photons.
• Independent processing of these photon types is crucial for accurate energy and timing measurements in BGO detectors.

Purpose of the Study:

• To develop and validate a novel field-programmable gate array (FPGA)-based time-of-flight (TOF) digitizer for bismuth germanate (BGO) detectors.
• To enable precise, independent measurement of scintillation and prompt Cerenkov photons for enhanced detector performance.
• To assess the digitizer's suitability for multi-channel applications, such as Positron Emission Tomography (PET) systems.

Main Methods:

• Implementation of a noise-resistant binary counter using the time-over-threshold (TOT) method for energy measurement.
• Integration of an embedded dual-side monitoring time-to-digital converter for efficient, low-resource timing acquisition.
• Experimental validation using BGO pixels coupled to silicon photomultipliers, including electrical testing and coincidence measurements.

Main Results:

• The FPGA-based TOF digitizer achieved a coincidence timing resolution (CTR) of 407 ps FWHM.
• Performance was comparable to traditional oscilloscope measurements (403 ps FWHM).
• The design demonstrated low resource utilization, indicating high scalability potential.

Conclusions:

• The developed FPGA-based TOF digitizer effectively processes dual photon types from BGO crystals.
• The digitizer offers high-precision timing and energy measurements with performance comparable to oscilloscopes.
• Its low resource footprint and scalability make it ideal for developing advanced, multi-channel BGO-based PET systems.