Miller Brian W, Barber H Bradford, Barrett Harrison H, Chen Liying, Taylor Sean J
College of Optical Sciences and Department of Radiology, University of Arizona, Tucson, AZ 85721.
Proc SPIE Int Soc Opt Eng. 2007 Jan 1;6510. doi: 10.1117/12.710109.
Recent advances have been made in a new class of CCD-based, single-photon-counting gamma-ray detectors which offer sub-100 μm intrinsic resolutions.1-7 These detectors show great promise in small-animal SPECT and molecular imaging and exist in a variety of configurations. Typically, a columnar CsI(Tl) scintillator or a radiography screen (Gd(2)O(2)S:Tb) is imaged onto the CCD. Gamma-ray interactions are seen as clusters of signal spread over multiple pixels. When the detector is operated in a charge-integration mode, signal spread across pixels results in spatial-resolution degradation. However, if the detector is operated in photon-counting mode, the gamma-ray interaction position can be estimated using either Anger (centroid) estimation or maximum-likelihood position estimation resulting in a substantial improvement in spatial resolution.2 Due to the low-light-level nature of the scintillation process, CCD-based gamma cameras implement an amplification stage in the CCD via electron multiplying (EMCCDs)8-10 or via an image intensifier prior to the optical path.1We have applied ideas and techniques from previous systems to our high-resolution LumiSPECT detector.11, 12 LumiSPECT is a dual-modality optical/SPECT small-animal imaging system which was originally designed to operate in charge-integration mode. It employs a cryogenically cooled, high-quantum-efficiency, back-illuminated large-format CCD and operates in single-photon-counting mode without any intermediate amplification process. Operating in photon-counting mode, the detector has an intrinsic spatial resolution of 64 μm compared to 134 μm in integrating mode.
最近，一类基于电荷耦合器件（CCD）的单光子计数伽马射线探测器取得了进展，其固有分辨率低于100微米。1-7这些探测器在小动物单光子发射计算机断层扫描（SPECT）和分子成像中显示出巨大潜力，并且有多种配置形式。通常，柱状碘化铯（铊）闪烁体或射线照相屏（硫氧化钆：铽）成像于电荷耦合器件上。伽马射线相互作用表现为分布在多个像素上的信号簇。当探测器以电荷积分模式运行时，跨像素的信号扩散会导致空间分辨率下降。然而，如果探测器以光子计数模式运行，则可以使用安杰尔（质心）估计或最大似然位置估计来估算伽马射线相互作用位置，从而使空间分辨率得到大幅提高。2由于闪烁过程的低光水平特性，基于电荷耦合器件的伽马相机通过电子倍增（EMCCD）8-10在电荷耦合器件中实现放大阶段，或者在光路之前通过图像增强器实现放大阶段。1我们已将先前系统的理念和技术应用于我们的高分辨率LumiSPECT探测器。11, 12 LumiSPECT是一种双模态光学/SPECT小动物成像系统，最初设计为以电荷积分模式运行。它采用低温冷却、高量子效率、背照式大幅面电荷耦合器件，并且在没有任何中间放大过程的情况下以单光子计数模式运行。在光子计数模式下运行时，该探测器的固有空间分辨率为64微米，而在积分模式下为134微米。
