Simultaneous Dual Isotope ToF-PET Imaging

ingle tracer positron emission tomography (PET) is a powerful molecular imaging technique. PET using multiple tracers can improve the specificity of PET and broaden its uses. For instance, there are demonstrated benefits to sequential imaging using two different tracers staggered in time. Unfortunately, this staggered imaging approach not only increases imaging time but also does not provide for simultaneous imaging of multiple tracers and may lead to errors due to temporal changes in physiological and molecular functions. Simultaneous dual isotope PET imaging has previously been investigated using a pure emitter and a dirty emitter. The main challenges of simultaneous dual isotope imaging are low detection efficiency of triple coincidences and low separability of pure and dirty positron emitters. With the rapid advance of coincidence time resolution (CTR) in PET (214ps in a commercial system), we can localize an annihilation event by the difference in their arrival time at the detectors. In this work, we used estimated annihilation positions to represent detected events and a novel method to separate dirty emitters from pure emitters in PET images. A simulation of a complex mixed source phantom in a dedicated brain PET system with an end-cap detector was carried out in GATE to demonstrate this proof of concept of simultaneous dual isotope PET imaging using time of flight (ToF) information. For pure and dirty sources, a relative error about 3% is achieved in the region of interest (RoI).