High Resolution SPECT-MR for Molecular Imaging

在这项为期两年的AARA赠款申请中，我们建议开发、构建和评估一个原型SPECT/MRI系统，用于同时进行小动物的高分辨率分子SPECT/MR成像，并有可能进一步发展为人脑SPECT/MRI系统。主要创新包括使用最先进的MR兼容碲锌镉(CZT)探测器模块，该探测器模块由我们的工业合作伙伴Gamma Medica-IDEAS(GMI)开发。新的CZT探测器具有较小的亚毫米可分辨像素大小，可以采集高分辨率SPECT投影数据。一个环形SPECT子单元将基于五个基于CZT的相机开发，每个相机由2.54cmx2.54 cm CZT探测器模块的5x5阵列组成。这些相机将无缝连接，形成一个环形SPECT亚单位，该亚单位将安装在3T飞利浦MRI系统中，允许对小动物进行高分辨率SPECT成像，以及可能开发的人脑SPECT/MRI系统，用于同时采集SPECT/MRI数据。将开发一个环绕小动物的具有多个针孔阵列的圆柱形准直器，并将设计和建造一个鸟笼射频线圈，连接到准直器圆柱体的内表面。小动物的多个针孔图像被投影到连续的探测器表面上。此外，对于无伪影的SPECT/MR联合配准图像，将发展填补方法、定量多针孔SPECT图像重建方法、优化的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丰富的专业知识，包括射频线圈设计、磁场均匀垫片、MR脉冲序列、MR数据采集方法以及图像重建和处理方法。拟议的研究将包括：(1)开发用于SPECT成像的高分辨率MR兼容CZT探测器，(2)开发用于无伪影高分辨率小动物MR成像的优化的RF发送/接收线圈、垫片方法和MRI脉冲序列，使用飞利浦3T MRI系统在存在SPECT亚单元的情况下进行无伪影高分辨率MR成像，(3)开发优化的MR兼容SPECT亚单元和用于3T MRI系统内无伪影SPECT图像的图像重建方法，以及(4)使用物理模型和模拟研究对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.