A MPPC Based Tool for Timing and Spatial Resolution Characterization of PET Detectors

When developing new detectors for positron emission tomography (PET) imaging it is necessary to characterize the performance in terms of spatial and timing resolution in order to understand how the detector performs relative to existing technology. With the move toward time-of-flight PET (TOF PET) due to its benefits for clinical imaging, characterization of the timing performance of PET detectors is taking on an increased importance. We present a probe designed to facilitate the simultaneous measurement of spatial and timing resolution of a PET detector using an electronically collimated beam of 511 keV photons. The design of the probe uses two Multi-Pixel Photon Counting (MPPC) single pixel detectors. The first, used to generate the timing signal, is coupled to a plastic scintillator containing an embedded positron emitting source. The second MPPC detector is coupled to a single LYSO crystal and is used to electronically collimate the 511 keV photon beam. Several features are built into the probe to facilitate the characterization of a PET detector under test including: 1) the two MPPC detectors are mounted on an arm that can be rotated in 15 degrees steps in order to allow characterization of spatial and timing resolution as a function of 511 keV photon beam incidence angle; 2) the effective size of the 511 keV photon beam can be varied by changing the distance between the two MPPC detectors, thus changing the geometric magnification (or minification) of the beam; 3) the probe can be used to acquire a flood irradiation timing measurement if only the output of the MPPC coupled to the plastic scintillator is used or the beam can be collimated by taking a coincidence with the LYSO detector.