A very thin MRPC developed for TOF-PET

Abstract

PET (Positron Emission Tomography) is a medical molecular imaging modality employed in cancer diagnosis and monitoring. Multi-gap Resistive Plate Chambers (MRPCs) are utilized in Time of Flight (TOF)-PET due to their superior time resolution. Our research group has successfully developed a 4-chamber 32-gap MRPC prototype with 0.128 mm gap thickness. The measured time resolution for cosmic rays is 20 ps, while the time resolution for the time difference between 0.511 MeV photon pairs is 193 ps Full Width at Half Maximum (FWHM). The 23.6 mm thickness of the MRPC prototype will affect the time resolution. To investigate the influence of the number and total thickness of gas gaps on the time resolution, Geant4 software is used to simulate the interaction between particles (such as cosmic rays and photons) and MRPC detectors. Most of the gamma photons interact with the resistive plates in MRPCs. It is ejected mostly a Compton electron into one gas gap, causing the gas ionization. In this paper, two 8-gap MRPC prototypes with 0.128 mm gap thickness and 4.2 mm total thickness are fabricated and tested. The time resolution of 39 ps for cosmic rays and 166 ps FWHM for 0.511 MeV photons is obtained using the fast front-end amplifier and waveform acquisition system. So, a real time PET image can be obtained with a pair of MRPCs, and the detection efficiency for gamma can be improved by increasing the number of thin MRPCs.