Synthetic-Collimator SPECT with Semiconductor Detectors

描述(申请人提供)：建议项目的目标是使用合成准直器成像方法改善临床前分子成像能力，这是一种创新的SPECT技术，其中断层图像是从以多倍放大收集的多针孔投影数据重建的。临床前成像任务，特别是小鼠大脑的分子成像，既需要高空间分辨率，又需要良好的灵敏度。需要亚毫米的空间分辨率来解析大脑结构，同时需要高灵敏度来避免与过量配基质量相关的药理效应，限制辐射剂量，并保持成像时间较短。为了满足这些相互竞争的需求，我们将同时使用硅和锗探测器。每种相机都提供了比传统闪烁相机更好的空间分辨率，使得在较低的针孔放大倍数下实现给定的空间分辨率成为可能。较低的放大倍数又允许使用更多数量的每单位探测器面积的针孔。由于这种特殊的锗探测器技术以前没有被应用于临床前SPECT，最初的任务将是优化信号处理，然后表征探测器作为伽马相机的性能。然后，将建立一个利用两个摄像头的SPECT成像系统，每个摄像头一个接一个地堆叠着一个硅探测器和一个锗探测器。这种设计将允许在两个不同的针孔放大倍数下同时使用两个不同能量的光子发射来进行成像。除了通过使用独特的双探测器层方法来提高灵敏度外，该方法还能够对多路传输的投影数据进行层析重建，从而通过允许使用更多的针孔来进一步提高灵敏度。将实施专门的校准程序和迭代重建算法。计算和分析工具将用于指导准直器设计、图像获取策略，并将实验测量结果与预期性能进行比较。最后，多针孔SPECT系统的成像能力将通过测量小鼠大脑中多巴胺D2受体放射性配基的纹状体结合来展示。这些测量将与体外测量和商业小动物SPECT系统进行的类似成像测量进行比较。总体而言，在每个探测器面积的基础上，这种方法应该为临床前SPECT成像研究提供空间分辨率和灵敏度的独特组合。

DESCRIPTION (provided by applicant): The objective of the proposed project is to improve preclinical molecular imaging capabilities using the synthetic-collimator imaging approach, which is an innovative SPECT technique in which tomographic images are reconstructed from multi-pinhole projection data collected at multiple magnifications. Preclinical imaging tasks, particularly molecular imaging of the mouse brain, demand both high spatial resolution and good sensitivity. Sub-millimeter spatial resolution is needed to resolve brain structures, while high sensitivity is needed to avoid pharmacologic effects associated with excessive ligand mass, limit radiation dose, and keep imaging times short. To address these competing demands, we will employ silicon and germanium detectors together. Each provides better spatial resolution than can be achieved with conventional scintillation cameras, making it possible to achieve a given spatial resolution at a lower pinhole magnification. Lower magnification, in turn, allows for a greater number of pinholes per unit detector area to be used. As this particular germanium detector technology has not previously been applied to preclinical SPECT, an initial task will be to optimize the signal processing and then characterize the detector performance as a gamma camera. Then a SPECT imaging system utilizing two camera heads, each with a silicon detector and a germanium detector stacked one behind the other, will be built. This design will allow for imaging to be done using photon emissions of two different energies at two different pinhole magnifications simultaneously. In addition to improving the sensitivity through the use of a unique two detector-layer approach, this method also enables tomographic reconstruction of multiplexed projection data, which further improves sensitivity by allowing a greater number of pinholes to be used. Specialized calibration procedures and iterative reconstruction algorithms will be implemented. Computational and analytical tools will be used to guide collimator design, image-acquisition strategy, and to compare experimental measurements to expected performance. Finally, the imaging capabilities of the multi- pinhole SPECT system will be demonstrated through the measurement of striatal binding in the mouse brain of a dopamine D2-receptor radioligand. These measurements will be compared to both to ex vivo measures and to analogous imaging measurements made with a commercial small-animal SPECT system. Overall, on a per detector-area basis this approach should provide a unique combination of spatial resolution and sensitivity for preclinical SPECT imaging studies.