@misc{oai:repo.qst.go.jp:00077297,
 author = {Akamatsu, Go and Yoshida, Eiji and Mikamoto, Takahiro and Maeda, Takamasa and Wakizaka, Hidekatsu and Tashima, Hideaki and Wakitani, Yuichiro and Matsumoto, Mikio and Yamaya, Taiga and Akamatsu, Go and Yoshida, Eiji and Maeda, Takamasa and Wakizaka, Hidekatsu and Tashima, Hideaki and Yamaya, Taiga},
 month = {Oct},
 note = {Sodium-22 is a radioisotope which is typically used as a calibration point source for PET. Its half-life of 2.6 years is suitably long enough while its positron range is as small as that of 18F. However the use of 22Na has been limited to a point-like shape. In this work, with the help of the Japan Radioisotope Association, we proposed a wider variety of 22Na sealed phantoms. As examples, we developed three types of 22Na phantoms: a 5-cm cylinder, a 60-cm flexible tube and a Derenzo-like multi-rod phantom. These were designed for PET system quality assurance and quality control (QA/QC) and performance measurements. At first, in this work, we evaluated uniformity and long-term stability of radioactivity distributions of these phantoms. These phantoms were scanned by the Biograph mCT Flow PET/CT scanner four times during 219 days. The uniformity of radioactivity distributions was evaluated by visual qualitative assessment and region-of-interest (ROI)-based quantitative assessment. In the case of the Derenzo-like phantom, we additionally scanned the phantom using the helmet-type PET prototype and Inveon small-animal PET system. In addition, we measured the radioactivity of these phantoms using the dose calibrator (Atomlab 500) four times during 107 days and we compared the measured and ideal decay curves. As a result, we found the variability of radioactivity distributions was lower than the 5% variation for the cylinder and tube phantoms. The Inveon PET visualized the smallest hot rod (1.6 mm diameter) of the Derenzo-like phantom and the radioactivity seemed to be uniformly distributed. The measured decay curves of all phantoms almost followed their respective ideal decay curve. We confirmed these phantoms have good uniformity and enough stability for PET system evaluation., 2019 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)},
 title = {Development of sealed 22Na phantoms for PET system QA/QC: uniformity and stability evaluation},
 year = {2019}
}