An Integrated PET-MRI System for Molecular Imaging

描述(由申请人提供)： 一种用于小动物分子成像的一体化PET-MRI系统是一个新兴的研究领域。尤其是正电子发射断层扫描(PET)揭示了生物体正在进行的功能过程的信息，如新陈代谢甚至基因表达。它的重要性，特别是在基础癌症研究中是巨大的。虽然PET在灵敏度(纳米磨牙)上几乎是无与伦比的，但它的缺点显然是缺乏解剖信息。即使是1毫米左右的空间分辨率也不能提供足够的解剖结构。将PET与另一种能够显示详细形态信息的成像设备相结合，将是分子成像的一个巨大优势和极大的好处。提供最佳解剖信息的方式是X射线计算机断层扫描(CT)和磁共振成像(MRI)。虽然CT需要较高的辐射剂量才能达到足够的分辨率，这可能会改变动物的生物功能，甚至可能改变整个动物模型，但MRI似乎是无害的。最重要的是，即使没有任何造影剂，MRI也能提供比CT更好的软组织对比度。 这项提议的目标是开发一种集成的PET-MRI系统，用于在小动物的运动皮质成像中同时采集数据。我们与田纳西州诺克斯维尔协和微系统公司合作开发的最新PET探测器是这项工作的基石：10x10 LSO块探测器(晶体尺寸2x2x10 mm 3)由紧凑的单片3x3雪崩光电二极管阵列读出。10XL多路复用器将所需的电子设备降至最低。紧凑型LSO-APD探测器可以被布置为7特斯拉磁共振扫描仪中的RF线圈和梯度设置之间的插入物，从而允许同时对小鼠进行PET和MR扫描。LSO-APD探测器和专用集成读出电子设备取得的令人鼓舞的结果，再加上对不同材料的初步测试结果，如LSO-APDPET探测器、塑料和7特斯拉油田的电子板，表明了该项目的可行性。然而，如果马赛克的一部分不允许同时采集数据，就会制定出几个后备解决方案，以至少实现连续的PET-MR成像，提供具有最高空间精度的形态和功能信息，这是两个独立系统永远无法实现的。 此外，这种组合系统的未来应用远远超出了这笔赠款中提议的工作。结合PET-MRI提供磁共振波谱信息或基于MR图像的PET数据校正(衰减或部分体积效应)将是非常有价值的，并为未来的药物和治疗开发提供巨大的潜力。

DESCRIPTION (provided by applicant): An Inteqrated PET-MRI System for Molecular Imaqinq Non invasive molecular imaging in small animals is an emerging field of research. Especially positron emission tomography (PET) reveals information about ongoing functional processes in living organism, such as metabolism or even gene expression. Its importance, especially in basic cancer research is tremendous. Although PET is nearly unbeatable in sensitivity (nano molar), its drawback is clearly the lack of anatomical information. Even a spatial resolution of about I mm can not provide sufficient anatomical structure. The combination of PET with another imaging device which reveals detailed morphological information would be a huge advantage and highly beneficial for molecular imaging. The modalities, providing best anatomical information are x-ray computed tomography (CT) and magnetic resonance imaging (MRI). Whereas CT requires a high radiation dose to achieve sufficient resolution, which might change biological function in the animals and potentially the entire animal model, MRI seems to be harmless. Most importantly, MRI provides a much better soft tissue contrast than CT, even without any contrast agents. The goal of this proposal is the development of an integrated PET-MRI system for simultaneous data acquisition in motecular imaging of small animals. Our latest PET detector development, in collaboration with Concorde Microsystems, Knoxville, TN, is the cornerstone for this work: a 10x10 LSO block detector (crystal size 2x2x10 mm 3) read-out by compact monolithic 3x3 APD arrays. The 10xl multiplexing minimizes the required electronics. The compact LSO-APD detectors can be arranged as an insert between RF-coil and gradient set in a 7 Tesla MR scanner, allowing simultaneous PET and MR scanning of mice. The encouraging results achieved with the LSO-APD detectors and dedicated integrated readout electronics, in combination with preliminary results from tests of different materials, such as the LSO-APD PET detectors, plastics, and electronic boards in the 7 Tesla field indicate the feasibility of this project. However, if one part of the mosaic does not allow a simultaneous data acquisition, several fall-back-solutions are worked out, to make at least a sequential PET-MR imaging possible, providing morphological and functional information with highest spatial accuracy, which could never be achieved with two separate systems. In addition, the future applications of such a combined system go far beyond the work proposed in this grant. A combined PET-MRI providing also magnetic resonance spectroscopy information or a PET data correction (attenuation or partial volume effect) based on the MR image would be very valuable and provides a lot of potential for future drug and therapy development.