Characterization studies of Silicon Photomultipliers and crystals matrices for a novel time of flight PET detector

摘要

This paper describes the characterization of crystal matrices and siliconphotomultiplier arrays for a novel Positron Emission Tomography (PET) detector,namely the external plate of the EndoTOFPET-US system. The EndoTOFPET-UScollaboration aims to integrate Time-Of-Flight PET with ultrasound endoscopy ina novel multimodal device, capable to support the development of new biomarkersfor prostate and pancreatic tumors. The detector consists in two parts: a PEThead mounted on an ultrasound probe and an external PET plate. The challenginggoal of 1 mm spatial resolution for the PET image requires a detector withsmall crystal size, and therefore high channel density: 4096 LYSO crystalsindividually readout by Silicon Photomultipliers (SiPM) make up the externalplate. The quality and properties of these components must be assessed beforethe assembly. The dark count rate, gain, breakdown voltage and correlated noiseof the SiPMs are measured, while the LYSO crystals are evaluated in terms oflight yield and energy resolution. In order to effectively reduce the noise inthe PET image, high time resolution for the gamma detection is mandatory. TheCoincidence Time Resolution (CTR) of all the SiPMs assembled with crystals ismeasured, and results show a value close to the demanding goal of 200 ps FWHM.The light output is evaluated for every channel for a preliminary detectorcalibration, showing an average of about 1800 pixels fired on the SiPM for a511 keV interaction. Finally, the average energy resolution at 511 keV is about13 %, enough for effective Compton rejection.