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内容記述 |
Whole gamma imaging (WGI) combines positron emission tomography (PET) and Compton imaging to utilize all detectable gamma rays for imaging. One of the applications of WGI is high-sensitivity 89Zr imaging utilizing both 511 keV pairs and 909 keV single gamma rays emitted after the positron decay. At the last IEEE MIC, we proposed a synergistic reconstruction method for WGI in that PET and Compton images are alternatively updated incorporating the other image for prior information. In this study, we experimentally demonstrated the performance of the synergistic image reconstruction to improve the 89Zr image utilizing 909 keV Compton data, which are inferior to PET data in terms of spatial resolution. We measured a NEMA NU-4 (image quality) IQ phantom filled with a 89Zr solution of 4.5 MBq for 2 min using a WGI prototype, which consisted of GSOZ scintillators of 2.85×2.85×7.5 mm³ for both scatterer and absorber detectors. Coincidence events were extracted by offline software from the measured singles data. From the coincidence events, PET events and 909 keV Compton events were extracted using energy windows. We evaluated the tradeoff between the percentage standard deviation (%STD) and the percentage recovery coefficient (%RC) for the rods, which are IQ indices defined in the NEMA NU4 2008 protocol. As a result, the tradeoff for the 2 mm rod was improved by the synergistic reconstruction of WGI compared with the case where only PET events were used. Therefore, we concluded that the proposed reconstruction algorithm successfully utilized Compton events to improve 89Zr PET image quality. |
