Presentation The helmet-neck PET geometry for high-sensitivity and low-cost brain imaging

田島, 英朗  ,  吉田, 英治  ,  岩男, 悠真  ,  脇坂, 秀克  ,  赤松, 剛  ,  前田, 貴雅  ,  高堂, 裕平  ,  関, 千江  ,  樋口, 真人  ,  須原, 哲也  ,  山下, 大地  ,  山谷, 泰賀

Dementia is one of the severe problems in the aging society. For early diagnosis of the dementia, several diagnostic medicines have been developed as PET tracers targeting amyloid- plaque or tau protein. Therefore, there are potential demands for the brain PET systems with high sensitivity and high resolution at a low cost. For this purpose, we have proposed helmet-type PET having hemispherical detector arrangement and an add-on detector to increase the sensitivity for the brain. Compared with the cylindrical PET, the helmet-type PET can increase the sensitivity for the brain region by 50% without increasing the number of detectors. For the add-on detector position, there are two choices: at the chin position (helmet-chin PET) and at the neck position (helmet-neck PET). Theoretically, the effect of the add-on detector to increase the sensitivity is equivalent regardless of the position. For a proof-of-concept, we developed a prototype helmet-type PET system. In the prototype, 47 block detectors were used to realize the hemispherical arrangement, and 7 block detectors were form the add-on detector. Each block detector was a 4-layer depth-of-interaction (DOI) detector consisting of 16 × 16 × 4 Zr-doped GSO crystals (2.8 mm × 2.8 mm × 7.5 mm) and a 64-ch flat-panel PMT. The total number of the block detectors were about ¼ of those typically used in whole body PET. First, we developed the helmet-chin PET prototype. The chin detector was designed to move upward for patient setup. Next, we changed the add-on detector position from the chin position to the neck position by remodeling of the gantry to develop the helmet-neck PET prototype. We evaluated and compared the sensitivity of the prototypes for the brain region, and we conducted healthy volunteer studies using 18F-FDG. As a result, the helmet-neck PET prototype had higher effect to increase the sensitivity than the helmet-chin PET prototype because the chin detector required a larger margin for patient safety while the neck detector could be placed closer to the brain region. The healthy volunteer studies showed that the both prototypes could image brain structure clearly. In addition, the result demonstrated that the neck detector had an effect of expanding the field of view toward the neck detector covering the cerebellum region with enough space. We concluded the helmet-neck PET is a promising geometry for high-sensitivity and low-cost brain imaging.
The 17th Conference of Peace through Mind / Brain Science

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