Synthetic-Collimator SPECT with Semiconductor Detectors

描述（由申请人提供）：拟议项目的目的是使用合成准直器成像方法提高临床前分子成像能力，合成准直器成像方法是一种创新的SPECT技术，其中断层扫描图像是从多个放大倍数下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，需要高空间分辨率和良好的灵敏度。需要亚毫米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体质量相关的药理学作用，限制辐射剂量，并保持成像时间短。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。每一种都提供了比常规闪烁相机所能实现的更好的空间分辨率，使得可以在较低的针孔放大率下实现给定的空间分辨率。较低的放大率又允许使用每单位检测器面积的更多数量的针孔。由于这种特殊的锗探测器技术以前尚未应用于临床前SPECT，因此最初的任务将是优化信号处理，然后将探测器性能表征为伽马相机。然后，SPECT成像系统，利用两个摄像头，每个与硅探测器和锗探测器堆叠一个在另一个后面，将建立。该设计将允许使用两种不同能量的光子发射同时以两种不同的针孔放大率进行成像。除了通过使用独特的两个检测器层方法来提高灵敏度之外，该方法还使得能够对复用投影数据进行断层摄影重建，这通过允许使用更多数量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，图像采集策略，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多巴胺D2受体放射性配体在小鼠脑中的纹状体结合来证明。将这些测量值与离体测量值和用商业小动物SPECT系统进行的类似成像测量值进行比较。总的来说，在每个探测器面积的基础上，这种方法应该提供一个独特的组合的空间分辨率和灵敏度的临床前SPECT成像研究。

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.