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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Anew brain-dedicated compact PET scanner with hemispherical detector arrangement has been recently proposed for high-sensitivity brain imaging. An appropriate standard phantom is highly required for an objective performance evaluation. The Hoffman 3-dimensional (3D) brain phantom has been widely used as a de-facto standard brain phantom. However, the Hoffman phantom cannot be inserted into hemispherical PET scanners because the phantom has a cylindrical shape outside, which is different from the actual human head. Therefore, the purpose of this study is to develop a 3D ‘hemispherical’ brain phantom which is applicable to various scanners including the scanners with
hemispherical detector arrangement. Changing outer shell into a hemispherical shape while maintaining the same radioactivity distribution as the original Hoffman phantom was the key. We performed a simulation study and an actual PET/CTstudy comparing the original Hoffman and hemispherical phantoms. In the simulation, we evaluated the count characteristics, image noise and voxel-by-voxel differences between phantom images and the digital reference. In the actual PET/CT study, we compared the PET images of the two phantoms using a commercial PET/CT scanner. As a result, in the simulation study, the noise equivalent count rate of the hemispherical phantom was higher than that of the original Hoffman phantom by about 20%. Onthe other hand, the difference in
the image noise was not considerable and average global absolute voxel-by-voxel differences from the reference were almost same between the cylindrical and hemispherical phantoms. In the actual PET/CT study, the hemispherical phantom was validated to use imaging performance evaluation, and the
obtained percent contrast was comparable with the original Hoffman phantom. The developed hemispherical phantom is useful for compact PET scanners with hemispherical detector arrangement in view of evaluation of appropriate scanning/reconstruction parameters and validation of the imaging performance towards clinical and widespread applications.
A 3-dimensional hemispherical brain phantom for compact dedicated brain PET scanners
