High Resolution SPECT-MR for Molecular Imaging

在这项为期2年的AARA拨款申请中，我们建议开发、构建和评估一个用于同时对小动物进行高分辨率分子SPECT/MR成像的原型SPECT/MRI系统，并有可能进一步发展成为人脑SPECT/MRI系统。主要创新包括使用由我们的工业合作伙伴Gamma Medica-Ideas （GMI）开发的最先进的MR兼容碲化镉锌（CZT）探测器模块。新的CZT探测器具有小的亚毫米分辨率像素尺寸，允许获取高分辨率SPECT投影数据。环形SPECT亚单元将基于五个基于CZT的相机开发，每个相机由一个5x5的2.54cmx2.54cm CZT探测器模块阵列组成。摄像机将无缝连接，形成一个环形SPECT亚单元，该亚单元将适合3T飞利浦MRI系统，允许对小动物进行高分辨率SPECT成像，以及人脑SPECT/MRI系统的潜在开发，以同时获取SPECT/MRI数据。将开发一种圆柱形准直器，该准直器周围有一系列多针孔，并将设计和构造一个鸟笼式射频线圈，该线圈连接在准直器圆柱体的内表面。小动物的多针孔图像被投射到相邻的探测器表面。此外，针对无伪影的共配准SPECT/MR图像，将开发调光方法、定量多针孔SPECT图像重建方法、优化MR脉冲序列和图像融合方法。约翰霍普金斯大学（JHU）的研究团队在高分辨率SPECT仪器，模拟工具和定量图像重建方法以及磁共振成像方面拥有强大的专业知识，包括射频线圈设计，磁场均匀性的闪烁，磁共振脉冲序列，磁共振数据采集方法以及图像重建和处理方法。提议的研究将涉及(1)开发用于SPECT成像的高分辨率MR兼容CZT探测器，(2)开发优化的RF发射/接收线圈，微光方法和MRI脉冲序列，用于使用Philips 3T MRI系统在存在SPECT亚基的情况下进行无伪影的高分辨率小动物MR成像，(3)开发优化的MR兼容SPECT亚基和图像重建方法，用于3T MRI系统内无伪影的SPECT图像。(4)使用物理模型和仿真研究对SPECT/MR系统进行初步评估。

In this 2-year AARA grant application, we propose to develop, construct, and evaluate a prototype SPECT/MRI system for simultaneous high-resolution molecular SPECT/MR imaging of small animals, with the potential of further developing into a human brain SPECT/MRI system. The main innovations include the use of state-of-the-art MR compatible cadmium zinc telluride (CZT) detector modules developed by our industrial partner, Gamma Medica-Ideas (GMI). The new CZT detectors have small sub-millimeter resolvable pixel size that allows acquisition of high-resolution SPECT projection data. A ring-type SPECT subunit will be developed based on five CZT based cameras each consists of a 5x5 array of 2.54cmx2.54cm CZT detector modules. The cameras will connected seamlessly to form a ring SPECT subunit that will fit inside a 3T Philips MRI system allowing high-resolution SPECT imaging for small animals as well as potential development of a human brain SPECT/MRI system, for simultaneous acquisition of SPECT/MRI data. A cylindrical collimator with an array of multi-pinhole apertures that surrounds the small animal will be developed and a birdcage RF coil will be designed and constructed that is attached to the inside surface of the collimator cylinder. Multi-pinhole images of the small animal are projected onto the contiguous detector surface. Also, shimming methods, quantitative multi-pinhole SPECT image reconstruction methods, optimized MR pulse sequences and image fusion methods will be developed for artifact-free co-registered SPECT/MR images. The Johns Hopkins University (JHU) team of investigators comprises strong expertise in high-resolution SPECT instrumentation, simulation tools and quantitative image reconstruction methods and in MR imaging including RF coil design, shimming for magnetic field uniformity, MR pulse sequences, MR data acquisition methods and image reconstruction and processing methods. The proposed research will involve (1) development of high-resolution MR compatible CZT detectors for SPECT imaging, (2) development of optimized RF transmit/receive coils, shimming methods and MRI pulse sequences for artifact-free high-resolution small animal MR imaging using the Philips 3T MRI system in the presence of the SPECT subunit, (3) development of an optimized MR compatible SPECT subunit and image reconstruction methods for artifact-free SPECT images inside the 3T MRI system, and (4) preliminary evaluation of the SPECT/MR system using physical phantom and simulation studies.