Testing of Singles Processing Unit for a Brain PET

Brain Positron Emission Tomography (PET) is a high-resolution imaging device specially used for clinical diagnosis and research of human brain diseases. To obtain the charge and time information of photons generated by single positron annihilation, a signal processing electronics system is built in the brain PET. The system consists of 28 Singles Processing Units (SPU), including 1792 charge measurement channels and 224 time measurement channels. Charge measurement of the SPU is achieved by amplification, shaping, analog-to-digital conversion, and area calculation of the detector output signal, and time measurement is implemented by the Tapped-Delay Line (TDL) Field Programmable Logic Array (FPGA) Time-to-Digital Converter (TDC). Before the brain PET system was assembled, a series of tests were conducted on all 28 SPUs to evaluate the charge and time measurement performance. The test results exhibit that all SPUs have good performance: charge measurement resolution is better than 2 ‰ Full Width at Half Maxima (FWHM) under 1.8 V typical signal input, and time measurement resolution is better than 40 ps FWHM, which satisfy the application requirements of the brain PET.