Offset Astigmatic and Variable Focusing Collimation for Helical SPECT Brain Scans

描述（由申请人提供）：本项目的总体目标是开发一种增强型成像技术，该技术使用创新的会聚束准直和3D螺旋路径（HP）进行定量单光子发射计算机断层扫描（SPECT）。有前途的SPECT分子显像剂正在开发用于诊断脑部疾病，如帕金森氏病。全锥束（FCB）SPECT有可能成为一个很好的诊断成像工具，用于小的大脑结构，特别是那些在大脑深处，因为它的放大率和它的高检测效率，这增加了越来越接近焦点。然而，当应用于脑成像时，使用遵循圆形轨道的FCB准直器的SPECT具有两个限制：i）源分布未被完全采样，这导致轴向源位置的图像伪影，所述轴向源位置不靠近准直器的中心、轴向和轴向。（垂直）焦平面;以及ii）由于患者肩部对准直器的放置的干扰，不能有效地对大脑的尾部区域进行成像。即使在HP之后使用FCB准直器的SPECT也存在后一个问题。这两个问题都有效地解决了以下HP的偏移光学束（OAB）和空间可变聚焦（SVF）准直器的创新组合：i）可以通过使用3D HP获得完整的空间采样，从而从以更高的灵敏度和放大率采集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，但其偏移的轴向焦线定位在大脑的尾部区域附近。拟议的研究将涉及实验扫描，以及计算机模拟和分析计算。现有的三摄像机SPECT系统和新型会聚束准直器，加上床平移，将被用来演示创新的成像技术。将为螺旋路径OAB和SVF投影数据开发迭代重建软件。将使用激光对准系统和点源的SPECT采集来确定描述系统校准以及SPECT扫描仪的机械和电气未对准的参数。首先，将使用模拟两个或三个会聚光束准直器的采集与使用单个会聚光束准直器的采集来研究空间采样的均匀性。国家的最先进的重建计划将占系统失调，点扩展响应，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择的几何和拟人幻影进行评价。初步临床研究将涉及少量人类受试者。该提案支持新成像技术的研究和开发，其结果将提供可用于重大转化研究的数据。从长远来看，新技术将通过改善脑部疾病的诊断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.