Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, CA, USA.
Phys Med Biol. 2010 May 7;55(9):2495-504. doi: 10.1088/0031-9155/55/9/005. Epub 2010 Apr 6.
Magnetic resonance (MR)-based multimodality imaging systems, such as single-photon emission tomography (SPECT)/magnetic resonance imaging (MRI) or positron emission tomography (PET)/MRI, face many difficulties because of problems with the compatibility of the nuclear detector system with the MR system. However, several studies have reported on the design considerations of MR-compatible nuclear detectors for combined SPECT/MRI. In this study, we developed a new radiofrequency (RF) coil and gamma-ray radiation shielding assembly to advance the practical implementation of SPECT/MRI in providing high sensitivity while minimizing the interference between the MRI and SPECT systems. The proposed assembly consists of a three-channel receive-only RF coil and gamma-ray radiation shields made of a specialized lead composite powder designed to reduce conductivity and thus minimizing any effect on the magnetic field arising from the induced eddy currents. A conventional birdcage RF coil was also tested for comparison with the proposed RF coil. Quality (Q)-factors were measured using both RF coils without any shielding, with solid lead shielding, and with our composite lead shielding. Signal-to-noise ratios (SNRs) were calculated using 4 T MR images of phantoms both with and without the new gamma-ray radiation shields. The Q-factor and SNR measurements demonstrate the improved MRI performance due to the new RF coil/gamma-ray radiation shield assembly designed for SPECT/MRI, making it a useful addition to multimodality imaging technology not only for animal studies but also for in vivo study of humans.
基于磁共振（MR）的多模态成像系统，如单光子发射断层扫描（SPECT）/磁共振成像（MRI）或正电子发射断层扫描（PET）/MRI，由于核探测器系统与磁共振系统的兼容性问题而面临许多困难。然而，已有几项研究报告了用于组合 SPECT/MRI 的 MR 兼容核探测器的设计考虑因素。在这项研究中，我们开发了一种新的射频（RF）线圈和伽马射线辐射屏蔽组件，以推进 SPECT/MRI 的实际实施，在最小化 MRI 和 SPECT 系统之间干扰的同时提供高灵敏度。所提出的组件由一个三通道仅接收 RF 线圈和伽马射线辐射屏蔽组成，伽马射线辐射屏蔽由专门设计的含铅复合粉末制成，旨在降低电导率，从而最大限度地减少由感应涡流引起的对磁场的任何影响。还测试了一个传统的鸟笼 RF 线圈，以便与提出的 RF 线圈进行比较。使用没有任何屏蔽、实心铅屏蔽和我们的复合铅屏蔽的两种 RF 线圈测量了 Q 因子。使用 4 T MR 图像计算了带有和不带有新的伽马射线辐射屏蔽的幻影的信噪比（SNR）。Q 因子和 SNR 测量结果表明，由于设计用于 SPECT/MRI 的新 RF 线圈/伽马射线辐射屏蔽组件，MRI 性能得到了改善，这不仅对动物研究，而且对人体的体内研究都是多模态成像技术的有用补充。
