Offset Astigmatic and Variable Focusing Collimation for Helical SPECT Brain Scans

描述(申请人提供)：该项目的总体目标是开发一种用于定量单光子发射计算机断层扫描(SPECT)的增强成像技术，该技术使用具有3D螺旋路径(HPS)的创新会聚光束准直。有希望的SPECT分子显像剂正在被开发用于诊断脑疾病，如帕金森氏病。全锥束(FCB)SPECT具有放大倍率高、检测效率高的特点，有可能成为诊断脑内微小结构，尤其是脑内深层结构的一种极佳的成像工具。然而，使用FCB准直器的SPECT在应用于脑成像时有两个限制：i)源分布不完全采样，这导致轴向源位置不靠近准直器中心的跨轴(垂直)焦平面的图像伪影；ii)由于患者的肩膀干扰准直器的放置，无法有效地成像大脑的尾部区域。即使是在惠普之后使用FCB准直器的SPECT也存在后一种问题。偏置像散光束(OAB)和空间可变聚焦(SVF)准直器的创新组合有效地解决了这两个问题：i)使用3D HPS可以获得完整的空间采样，从而从以更高灵敏度和放大倍数获取的投影数据中获得高质量、无伪影的重建图像；以及ii)消除了肩部干扰。OAB准直器可以保持与大脑的紧密接近，但其偏移量的横轴焦线位于大脑尾部附近。这项拟议的研究将涉及实验扫描，以及计算机模拟和分析计算。现有的三摄像头SPECT系统和新型会聚光束准直器，加上床位平移，将被用来展示创新的成像技术。将开发螺旋路径OAB和SVF投影数据的迭代重建软件。将使用激光对准系统和对点源的SPECT采集来确定描述SPECT扫描仪的系统校准和机械和电气失调的参数。最初，将使用模拟两个或三个会聚光束准直器与使用单个会聚光束准直器的采集来研究空间采样的一致性。最先进的重建程序将考虑系统未对准、点扩散响应、衰减和散射的影响。这些因素对图像分辨率、量化和伪影的影响将使用选定的几何和拟人化幻影进行评估。一项试验性的临床研究将涉及一小部分人类受试者。这项提议支持研究和开发新的成像技术，其结果将提供数据，在此基础上进行重大的转化性研究。从长远来看，新技术可能会通过改善对大脑疾病的诊断来提供更好的医疗保健。

DESCRIPTION (provided by applicant): The overall goal of this project is to develop an enhanced imaging technology using innovative convergent- beam collimation with 3D helical paths (HPs) for quantitative single photon emission computed tomography (SPECT). Promising SPECT molecular imaging agents are being developed for diagnosis of brain diseases such as Parkinson's disease. Full-cone-beam (FCB) SPECT has the potential to be an excellent diagnostic imaging tool for small brain structures, particularly those deep within the brain because of its magnification and its high detection efficiency, which increases with increasing proximity to the focal point. However, SPECT using a FCB collimator following a circular orbit has two limitations when applied to brain imaging: i) The source distribution is not completely sampled, which results in image artifacts for axial source locations that are not near the collimator's central, transaxial (perpendicular) focal plane; and ii) The caudal region of the brain cannot be imaged effectively because of interference of the patient's shoulders with the placement of the collimator. Even SPECT using a FCB collimator following a HP has the latter problem. Both problems are effectively addressed by the innovative combination of offset-astigmatic-beam (OAB) and spatially-variable-focusing (SVF) collimators following HPs: i) Complete spatial sampling can be obtained by using 3D HPs, resulting in high quality, artifact-free reconstructed images from projection data acquired at higher sensitivity and magnification; and ii) Shoulder interference is eliminated. OAB collimators can maintain close proximity to the brain and yet have their offset transaxial focal line positioned near the brain's caudal region. The proposed research will involve experimental scans, as well as computer simulations and analytic calculations. An existing triple-camera SPECT system and novel convergent-beam collimators, coupled with bed translation, will be used to demonstrate the innovative imaging technique. Iterative reconstruction software will be developed for helical-path OAB and SVF projection data. A laser alignment system and SPECT acquisitions of point sources will be used to determine parameters that describe system calibrations and mechanical and electrical misalignments of the SPECT scanner. Initially, uniformity of spatial sampling will be investigated using acquisitions that simulate two or three convergent-beam collimators versus the use of a single convergent-beam collimator. State-of-the-art reconstruction programs will account for the effects of system misalignments, point-spread-response, attenuation and scatter. The effects of these factors on image resolution, quantification and artifacts will be evaluated using a selection of geometric and anthropomorphic phantoms. A pilot clinical study will involve a small number of human subjects. This proposal supports the research and development of new imaging techniques, and the results will provide data upon which significant translational research can be built. In the long term, the new techniques will potentially provide better health care through improved diagnosis of brain disease.