Offset Astigmatic and Variable Focusing Collimation for Helical SPECT Brain Scans

描述（由申请人提供）：该项目的总体目标是开发一种增强成像技术，使用创新的会聚束准直和3D螺旋路径（hp）用于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，如帕金森病。由于其放大倍率和高检测效率，全锥束SPECT （FCB）有潜力成为一种出色的小脑结构诊断成像工具，特别是那些位于大脑深处的结构，其检测效率随着与焦点的接近度的增加而增加。然而，使用沿圆形轨道运行的FCB准直器的SPECT在应用于脑成像时有两个限制：i)源分布没有完全采样，这导致轴向源位置不靠近准直器的中心、跨轴（垂直）焦平面的图像伪影；ii)由于患者肩部与准直仪位置的干扰，不能有效成像脑尾区。即使SPECT使用FCB准直器跟随HP也有后一种问题。偏移像散光束（OAB）和空间变焦（SVF）准直器的创新组合有效地解决了这两个问题：1)使用三维高分辨率准直器可以获得完整的空间采样，从而在更高的灵敏度和放大倍率下获得高质量、无伪影的投影数据重建图像；ii)消除肩部干扰。OAB准直器可以保持与大脑的近距离，但其偏置的横轴聚焦线位于大脑尾侧区域附近。拟议的研究将包括实验扫描，以及计算机模拟和分析计算。现有的三相机SPECT系统和新型会聚光束准直器，加上床平移，将用于演示创新的成像技术。开发螺旋路径OAB和SVF投影数据的迭代重建软件。激光对准系统和点光源的SPECT采集将用于确定描述系统校准和SPECT扫描仪的机械和电气失调的参数。最初，空间采样的均匀性将通过使用模拟两个或三个会聚光束准直器而不是使用单个会聚光束准直器来研究。最先进的重建程序将考虑系统失调、点扩展响应、衰减和散射的影响。这些因素对图像分辨率，量化和人工制品的影响将使用几何和拟人化的幻影进行评估。一项试验性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，其结果将为建立重要的转化研究提供数据。从长远来看，新技术将有可能通过改进脑部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.