Design and Simulation of a Novel High Performance Cardiac SPECT Camera

描述(申请人提供)：SPECT是评估心肌灌注的一项重要技术。然而，由于需要准直，SPECT的灵敏度较低。作为SPECT的主要市场，新的系统已经出现，对心肌灌注成像具有更高的灵敏度。这些设计大多着眼于对心脏周围感兴趣的区域进行成像。Funk等人的设计和GE的Discovery系列使用了多个针孔。销孔设计的优点是没有活动部件，从而降低了制造和维修成本。我们提出了一种新的方法，通过在针孔准直器上安装曲面探测器来提高分辨率和/或灵敏度。由于放大倍率的提高，在每个针孔上使用曲面探测器比连接在相同针孔上的平板探测器的分辨率更高。然后，可以通过增加针孔直径来将提高的分辨率转换为灵敏度，以获得与平板探测器类似的分辨率的更好的灵敏度性能。我们从数学上推导了抛物面、锥面和球面探测器的平均分辨率表达式，并计算了在保持与通常用于心脏SPECT的莱尔平行准直器相同的平均分辨率的情况下灵敏度的提高。在针孔分辨率模型的基础上，实现了抛物面探测器的解析光线跟踪正向投影仪。光线跟踪模拟证实了我们的分析结果。我们设计了一种固定的针孔结构，其中多组针孔集中在心脏体积上。我们的初步设计表明，每个针孔后面都有抛物面形状的探测器，比平面型探测器的高灵敏度多针孔系统的灵敏度提高了48%-85%(取决于使用的针孔数量)。与目前用于心脏成像的临床系统相比，弯曲探测器的灵敏度提高了7.4到9.3倍，分辨率与感兴趣区域的Lehr相似。我们的假设是，通过寻找最优的曲面探测器表面，以及最重要的是，通过对迭代重建中的针孔分辨率、穿透和探测器视差效应进行建模以进行补偿，可以实现进一步的改进。因此，可能会有进一步的分辨率改进，以获得更高的灵敏度。我们的总体目标是形式化地优化探测器表面，对重建算法中的分辨率、穿透和探测器视差效应进行建模，并评估我们所提出的系统的性能改进。 公共卫生相关性：这项拨款中建议的工作在两年间分配不均。如研究计划所示，在第一年，将完成所有的理论设计和建模(由PI负责)。将开始实施前向投影仪和重建算法(这是博士后研究员在PI的指导和帮助下负责的)。这包括具体目标1和具体目标2和具体目标3的重要部分。第二年将完成算法的实施，并对不同的设计进行评估和比较。预计在第二年，独立调查员，特别是联合调查员的努力程度将会降低。在第二年，国际和平研究所将继续指导和帮助博士后研究员完成重建算法的实施，评估不同的设计，并编写材料，以便在同行评议的期刊上发表。不均衡的模块预算反映了工作计划中的这种不平衡。PI的相对参与度将为55%-44%。预计在拨款的第一年，将更需要联合调查人员的建议。博士后研究员将在两年内平等地从事工作。

DESCRIPTION (provided by applicant): SPECT is an important technique for assessing myocardial perfusion. However SPECT suffers from low sensitivity because of the necessity for collimation. New systems have emerged with higher sensitivity for myocardial perfusion imaging, a primary market for SPECT. Most of these designs focus on imaging a region of interest around the heart. The design by Funk et al and Discovery series from GE use multiple pinholes. The advantage of pin-hole designs is that there are no moving parts, thus reducing manufacturing and servicing costs. We propose a novel method to improve resolution and/or sensitivity by using curved detectors fitted to pin-hole collimators. The use of a curved detector on each pin-hole results in a better resolution over that of a flat-detector attached to the same pin-hole, because of improved magnification. The improved resolution can then be swapped for sensitivity by increasing the pin-hole diameter, to obtain better sensitivity performance for similar resolution as the flat-detector. We mathematically derived expressions for average resolution of paraboloid, conical and spherical detectors, and calculated the sensitivity improvement keeping the same average resolution as the LEHR parallel collimators normally used for Cardiac SPECT. We also implemented an analytical ray-tracing based forward projector for the paraboloid detector with the model of the pin-hole resolution. The ray-tracing simulations corroborated our analytical results. We devised a stationary configuration of the pinholes where sets of pinholes are focused on the cardiac volume. Our preliminary design with the paraboloid-shaped detector behind each pin-hole, showed that the sensitivity improvement over the high-sensitive multi-pin-hole system with flat-detectors was 48-85% (depending upon the number pin-hole used). The sensitivity improvement of the curved detector over the clinical systems currently used for cardiac imaging was a factor of 7.4 to 9.3, with resolution similar to that of LEHR in the region of interest. Our hypothesis is that further improvements may be achieved by finding the optimum curved detector surface and most importantly, by modeling the pin-hole resolution and penetration and detector parallax effects in iterative reconstruction for compensation. Thus potentially there would be further resolution improvement to be traded to obtain improved sensitivity. Our overall goal is to thus formally optimize the detector surface and model the resolution and penetration and detector parallax effect within the reconstruction algorithm and evaluate the performance improvements for our proposed system. PUBLIC HEALTH RELEVANCE: The work proposed in this grant is distributed unevenly between the two years. As shown in the research plan, in the first year it is proposed that all the theoretical design and modeling (which are the PI's responsibility) will be finished. The implementation of the forward projector and reconstruction algorithm (which is the post-doctoral fellow's responsibility, under guidance and help from the PI) will be started. This encompasses Specific Aim 1 and significant parts of Specific Aim 2 and Specific Aim 3. In the second year the implementation of the algorithm will be finished and different designs will be evaluated and compared. The degree of effort of the PI and in particular the co- investigators is expected to be less for the second year. In the second year the PI will continue to guide and help the postdoctoral fellow in finishing the implementation of the reconstruction algorithm and evaluating the different designs and writing up the material for publication in peer-reviewed journals. The uneven-modular budget reflects this unevenness in work-plan. The PI's relative engagement would be 55%-44%. It is expected that advice from the co-Investigators' will be needed more in the first year of the grant. The post-doctoral fellow will be equally engages throughout the two years.