Presentation Add‐on detector position for the second helmet PET prototype: chin vs. neck 

田島, 英朗  ,  吉田, 英治  ,  岩男, 悠真  ,  脇坂, 秀克  ,  前田, 貴雅  ,  高堂, 裕平  ,  関, 千江  ,  須原, 哲也  ,  山下, 大地  ,  田沢, 周作  ,  山谷, 泰賀

Objectives: Dementia is a severe health problem in aging societies. For early diagnosis of the dementia, there is an emerging demand for dedicated brain PET scanners. Therefore, we have proposed a helmet PET geometry with an add-on detector for high sensitivity, high resolution, and low cost brain PET. Our first prototype had an add-on detector at the chin position (helmet-chin PET). However, the gantry design gave oppressive feeling to the patient and the movement of the chin detector was inconvenient for the patient setup. On the other hand, our previous simulation have shown that the add-on detector covering the neck position has equivalent effect (Tashima and Yamaya, PMB 61, pp. 7205-7220, 2016). In this study, therefore, we developed a “helmet-neck” PET prototype having the add-on detector at the neck position by remodeling the previous helmet-chin PET. Methods: We developed the helmet PET prototype with 54 four-layer depth-of-interaction (DOI) detectors, each of which consisted of a 16×16×4 array of 2.8×2.8×7.5 mm3 Zr-doped GSO crystals and a 64-ch flat-panel photomultiplier tube. The prototype had a helmet part and add-on detector part, which consisted of 47 and 7 DOI detectors, respectively. We compared the effect of the add-on detector to increase the sensitivity for a hemispherical pool phantom corresponding to the imaging region for brain. In addition, we measured a 3D brain phantom for testing the imaging performance of the helmet-neck PET.Results: The sensitivity for the brain region was increased with the add-on detector by 12% in the helmet-chin PET and by 20% in the helmet-neck PET compared with the geometry without add-on detector. The sensitivity difference between the chin and the neck detector was caused by larger margin of the chin detector, which was required for patient setup and safety. As a result, the detector arrangement of the helmet-neck PET could be more compact than the helmet-chin PET. The brain phantom imaging showed that the helmet-neck PET can obtain clear image even at the bottom of the helmet part where high noise was observed without the add-on detector.Conclusion: The helmet-neck PET has promising performance for high sensitivity brain imaging and improved convenience for patient studies.
SNMMI 2017

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