Design and Simulation of a Novel High Performance Cardiac SPECT Camera

描述（由申请人提供）：SPECT是评估心肌灌注的重要技术。然而，由于需要准直，SPECT的灵敏度低。新的系统已经出现，具有更高的灵敏度，心肌灌注成像，SPECT的主要市场。这些设计中的大多数集中于对心脏周围的感兴趣区域进行成像。Funk等人的设计和GE的Discovery系列使用多个针孔。销孔设计的优点是没有移动部件，从而降低了制造和维修成本。我们提出了一种新的方法来提高分辨率和/或灵敏度，通过使用弯曲的探测器安装到针孔准直器。在每个针孔上使用弯曲的探测器，由于放大率提高，因此比连接到同一针孔的平面探测器的分辨率更好。然后，通过增加针孔直径，可以将改进的分辨率交换为灵敏度，以获得与平面检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、圆锥面和球面探测器的平均分辨率表达式，并计算了保持与通常用于心脏SPECT的LEHR平行准直器相同的平均分辨率的灵敏度提高。我们还实现了一个基于解析光线跟踪的抛物面探测器的针孔分辨率模型的前向投影。射线追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配置，其中多组针孔集中在心脏体积上。我们的初步设计与每个针孔后面的抛物面形探测器，表明灵敏度提高了高灵敏度的多针孔系统与平面探测器是48-85%（取决于针孔的数量使用）。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至9.3倍，在感兴趣区域的分辨率与LEHR相似。我们的假设是，可以通过找到最佳的弯曲探测器表面，最重要的是，通过模拟针孔分辨率和渗透和探测器视差的影响，在迭代重建补偿，以实现进一步的改善。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，从而正式优化探测器表面和重建算法内的分辨率和穿透和探测器视差效果建模，并评估我们提出的系统的性能改进。 公共卫生相关性：该补助金中提出的工作在两年之间分配不均。如研究计划所示，第一年计划完成所有理论设计和建模（PI负责）。将开始实施前向投影仪和重建算法（由博士后负责，在PI的指导和帮助下）。这包括具体目标1以及具体目标2和具体目标3的重要部分。在第二年，算法的实施将完成，不同的设计将进行评估和比较。预计第二年PI（尤其是合作研究者）的工作量将减少。在第二年，PI将继续指导和帮助博士后完成重建算法的实施，评估不同的设计，并撰写在同行评审期刊上发表的材料。不均衡的模块预算反映了工作计划中的这种不均衡。PI的相对参与度为55%-44%。预计在赠款的第一年，将更多地需要共同研究者的建议。博士后研究员将在两年中平等参与。

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.