Gu Y, Levin C S
Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA. Molecular Imaging Instrumentation Laboratory, Department of Radiology, Stanford University, Stanford, CA 94305, USA.
Phys Med Biol. 2014 Jun 7;59(11):2599-621. doi: 10.1088/0031-9155/59/11/2599. Epub 2014 May 1.
We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (26 to ~127.5 ns full width at half maximum (FWHM) for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (34 to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips' weighting functions, which indicated a stronger 'small pixel' effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 to -80 V w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100 µm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns.
我们正在开发一种分辨率为1毫米的小动物正电子发射断层扫描（PET）系统，该系统使用3D定位碲化镉锌光子探测器，探测器由40毫米×40毫米×5毫米的晶体组成，晶体采用交叉条状电极图案进行金属化处理，阳极条间距为1毫米。我们使用一个包含不同尺寸阴极和导向电极条的测试探测器，针对固有灵敏度以及空间、能量和时间分辨率性能对电极图案设计进行了优化。研究发现，3毫米宽和5毫米宽的阴极条能够以相同的精度定位靠近阴极条边界处的电荷共享光子相互作用。3毫米宽的阴极条在阳极和阴极平面之间的光子相互作用位置上，时间分辨率变化较大（对于0.5毫米和4.2毫米深度，半高宽（FWHM）分别约为26至127.5纳秒）。相比之下，5毫米宽的阴极条在相同相互作用位置表现出更稳定的时间分辨率（FWHM约为34至83纳秒），在与电极平面正交的方向上提供了更线性的空间定位，并且光子灵敏度比3毫米宽的阴极条提高了多达68.4%。通过分析阴极条的加权函数来理解这些结果，结果表明3毫米宽的阴极条中存在更强的“小像素”效应。相对于阳极电位，从0到 -80伏降低导向电极偏压时，光子灵敏度和阳极能量分辨率会提高。对于电荷共享光子相互作用，较宽的导向电极条（400微米对100微米）在能量分辨率上有轻微改善。尽管本研究成功聚焦于PET性能的电极图案特征，但这些结果通常适用于采用交叉条状电极图案的半导体光子探测器。
