Proposal of Morphological Imaging for direct Positron Emission Imaging

Direct positron emission imaging (dPEI), a novel molecular imaging technique that does not require image reconstruction processes, was demonstrated using ultrafast time-of-flight radiation detectors in recent years. The dPEI can image functional information in vivo using annihilation gamma rays from positron emitters, and is expected to be a next-generation modality owing to its space-saving and flexible geometric features. On the other hand, there remains an issue in quantitative accuracy with only dPEI images because it is difficult to perform attenuation correction by using the corresponding morphological information. In this study, we propose a novel reconstruction-free image-formation method toward the acquisition of morphological information corresponding to dPEI. Specifically, a morphological image is acquired by using Compton scattered events in the subject among the annihilation gamma rays emitted from positron-emitting nuclides placed between one of the dPEI detectors and the subject. Evaluations through Monte Carlo simulation showed that functional and morphological hybrid images can be acquired with the same detector geometry and attenuation correction improves the quantification of dPEI images. It is possible to simultaneously access various object data, which expects the synergistic effect of the two imaging methodologies.