Akram Md Shahadat Hossain, Levin Craig S, Nishikido Fumihiko, Takyu Sodai, Obata Takayuki, Yamaya Taiga
Department of Advanced Nuclear Medicine Sciences, Institute of Quantum Medical Science, National Institutes for Quantum Science and Technology (QST), 4-9-1 Anagawa, Inage, Chiba, 263-8555, Japan.
Department of Radiology, School of Medicine, Stanford University, Stanford, CA, 94305-5128, USA.
Radiol Phys Technol. 2024 Mar;17(1):60-70. doi: 10.1007/s12194-023-00747-w. Epub 2023 Oct 24.
The purpose of this study is to evaluate the RF field responses of partial-ring RF-shielded oval-shaped positron emission tomography (PET) inserts that are used in combination with an MRI body RF coil. Partial-ring PET insert is particularly suitable for interventional investigation (e.g., trimodal PET/MRI/ultrasound imaging) and intraoperative (e.g., robotic surgery) PET/MRI studies. In this study, we used electrically floating Faraday RF shield cages to construct different partial-ring configurations of oval and cylindrical PET inserts and performed experiments on the RF field, spin echo and gradient echo images for a homogeneous phantom in a 3 T clinical MRI system. For each geometry, partial-ring configurations were studied by removing an opposing pair or a single shield cage from different positions of the PET ring. Compared to the MRI-only case, reduction in mean RF homogeneity, flip angle, and SNR for the detector opening in the first and third quadrants was approximately 13%, 15%, and 43%, respectively, whereas the values were 8%, 23%, and 48%, respectively, for the detector openings in the second and fourth quadrants. The RF field distribution also varied for different partial-ring configurations. It can be concluded that the field penetration was high for the detector openings in the first and third quadrants of both the inserts.
本研究的目的是评估与MRI体部射频线圈联合使用的部分环形射频屏蔽椭圆形正电子发射断层扫描（PET）插件的射频场响应。部分环形PET插件特别适用于介入研究（例如，PET/MRI/超声三模态成像）和术中（例如，机器人手术）PET/MRI研究。在本研究中，我们使用电悬浮法拉第射频屏蔽笼构建了椭圆形和圆柱形PET插件的不同部分环形配置，并在3T临床MRI系统中对均匀体模进行了射频场、自旋回波和梯度回波图像的实验。对于每种几何形状，通过从PET环的不同位置移除一对相对的屏蔽笼或单个屏蔽笼来研究部分环形配置。与仅使用MRI的情况相比，第一和第三象限中探测器开口处的平均射频均匀性、翻转角和信噪比分别降低了约13%、15%和43%，而第二和第四象限中探测器开口处的相应值分别为8%、23%和48%。不同部分环形配置的射频场分布也有所不同。可以得出结论，两种插件的第一和第三象限中探测器开口处的场穿透率较高。
