An investigation of coincidence detection methods for Trans-PET

Implementation of coincidence detection in PET systems usually involve energy discrimination and time discrimination. Depending on which is performed at first, the coincidence detection can be divided into two ways: energy discrimination before time discrimination (ETD) and time discrimination before energy discrimination (TED). The major difference of them is that, certain doubles from multiples which will be discarded by TED may be recovered by ETD. Since the extra doubles retrieved by ETD may contain false coincidence such as scatters and randoms, it is hard to tell whether they are beneficial or not. In this work, these two coincidence detection methods were evaluated and compared for our system named Trans-PET. The initial results revealed that the ETD had nearly 12% improvement both in sensitivity and NECR than TED while using a broader energy window of 250-750 keV. The improvement was reduced as the narrowing of the energy window by increasing its lower threshold. Considering the sensitivity and SNR, ETD seems to be the preferred choice in Trans-PET.