量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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【Purpose】Recent progress in radioactive source production technology made it possible to generate a sealed radioactive source with flexible shape. The Japan Radioisotope Association (JRIA) developed three types of novel shape sample sources [5-cm-diameter cylinder, 60-cm flexible tube, Derenzo-like multi-rod (rod diameter: 1.6~6.0 mm)] with 22Na and 68Ge. These novel sources can be applied for a PET scanner QA/QC, such as daily QC and performance measurements. In this work, we evaluated uniformity and long-term stability of these sample sources.
【Method】All sources were scanned by the Biograph mCT Flow every month for three months. For the 5-cm-diameter cylindrical source, we placed circular regions-of-interest (ROIs) on three axial slices and evaluated its uniformity by calculating a coefficient of variation (CV). In addition, the measured activity decay was evaluated to confirm these sources correctly follow a half-life of corresponding radionuclide. For the 60-cm tube source, the ROI was placed to cover the whole source and calculated its total activity. The Derenzo-like multi-rod source was scanned by not only Biograph mCT Flow but also Inveon small-animal PET scanner and brain-dedicated helmet-type PET scanner. We visually evaluated the uniformity of activity distributions of the Derenzo-like source.
【Result】The CV among axial slices for the cylindrical source was 2% or less. The measured activity decays of the cylindrical source and the tube source followed the half-life of corresponding radionuclide. We were able to compare image resolutions among the three scanners using the Derenzo-like source. The Inveon scanner visualized the smallest rod of which activity seemed to be uniformly distributed.
【Conclusion】The uniformity and stability of the three sample sources have been maintained for three months. We are to try to make more complicated shape sources for a PET scanner QA/QC.
Initial evaluation of novel shape radioactive sample sources with 22Na and 68Ge
