Three-dimensional and Multienergy Gamma-ray Simultaneous Imaging by Using a Si/CdTe Compton Camera

Purpose: To develop a silicon (Si) and cadmium telluride (CdTe) imaging Compton camera for biomedical application on the basis of technologies used for astrophysical observation and to test its capacity to perform three-dimensional (3D) imaging. Materials and Methods: All animal experiments were performed according to the Animal Care and Experimentation Committee (Gunma University, Maebashi, Japan). Flourine 18 fluorodeoxyglucose (FDG), iodine 131 (I-131) methylnorcholestenol, and gallium 67 (Ga-67) citrate, separately compacted into micro tubes, were inserted subcutaneously into a Wistar rat, and the distribution of the radioisotope compounds was determined with 3D imaging by using the Compton camera after the rat was sacrificed (ex vivo model). In a separate experiment, indium 111(In-111) chloride and I-131-methylnorcholestenol were injected into a rat intravenously, and copper 64 (Cu-64) chloride was administered into the stomach orally just before imaging. The isotope distributions were determined with 3D imaging after sacrifice by means of the list-mode-expectation-maximizingmaximum- likelihood method. Results: The Si/CdTe Compton camera demonstrated its 3D multinuclear imaging capability by separating out the distributions of FDG, I-131-methylnorcholestenol, and Ga-67-citrate clearly in a test-tube-implanted ex vivo model. In the more physiologic model with tail vein injection prior to sacrifice, the distributions of I-131-methylnorcholestenol and Cu-64-chloride were demonstrated with 3D imaging, and the difference in distribution of the two isotopes was successfully imaged although the accumulation on the image of In-111-chloride was difficult to visualize because of blurring at the low-energy region. Conclusion: The Si/CdTe Compton camera clearly resolved the distribution of multiple isotopes in 3D imaging and simultaneously in the ex vivo model. (C) RSNA, 2013