Large-area single-photon-counting CdTe detector for synchrotron radiation computed tomography: adedicated pre-processing procedure
Large-area single-photon-counting CdTe detector for synchrotron radiation computed tomography: adedicated pre-processing procedure
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DOI：
10.1107/s1600577518006197
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发表时间：
2018-07-01
影响因子：
2.5
通讯作者：
Golosio, Bruno
中科院分区：
文献类型：
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作者：
Brombal, Luca;Donato, Sandro;Golosio, Bruno
大面积CdTe单光子计数探测器由于其高效率、低本征噪声和不存在影响空间分辨率的散射屏而在低剂量成像应用中变得越来越有吸引力。然而，目前，由于单个传感器的尺寸很小（通常为几cm（2）），因此需要多模块架构来获得大视场。这需要应对模块间间隙和接近边缘的像素，这通常显示出非最佳行为。此外，高Z检测器通常由于电荷捕获而显示增益随时间的变化：这种效应是有害的，特别是在计算机断层摄影（CT）应用中，其中单个断层摄影图像需要在几秒钟内连续获取数百个投影。这项工作已经在SYRMA-3D项目的框架内，在Elettra同步辐射设施（的里雅斯特，意大利）的SYRMEP光束线上进行，该项目旨在利用同步辐射进行世界上第一个乳房CT临床研究。为PIXIRAD-8碲化镉单光子计数探测器开发了一个专门的数据预处理程序，该探测器包括一个由8个30.7mm × 24.8mm模块组成的阵列，覆盖了246 mm × 25 mm的敏感区域，覆盖了整个同步辐射光束。该程序由五个模块组成，即动态平场，间隙缝合，动态环去除，投影去斑和周围间隙均衡。每个块进行了讨论和比较，如果存在的话，与传统的方法。针对人体乳腺标本的相衬CT图像证明了预处理的有效性。所提出的程序，它提供了依赖于投影指数的校正的动态性质，允许有效地去除时间相关的伪影，保留包括相位效应的主要图像特征。
Large-area CdTe single-photon-counting detectors are becoming more and more attractive in view of low-dose imaging applications due to their high efficiency, low intrinsic noise and absence of a scintillating screen which affects spatial resolution. At present, however, since the dimensions of a single sensor are small (typically a few cm(2)), multi-module architectures are needed to obtain a large field of view. This requires coping with inter-module gaps and with close-to-edge pixels, which generally show a non-optimal behavior. Moreover, high-Z detectors often show gain variations in time due to charge trapping: this effect is detrimental especially in computed tomography (CT) applications where a single tomographic image requires hundreds of projections continuously acquired in several seconds. This work has been carried out at the SYRMEP beamline of the Elettra synchrotron radiation facility (Trieste, Italy), in the framework of the SYRMA-3D project, which aims to perform the world's first breast-CT clinical study with synchrotron radiation. An ad hoc data pre-processing procedure has been developed for the PIXIRAD-8 CdTe single-photon-counting detector, comprising an array of eight 30.7mm x 24.8mm modules tiling a 246mm x 25mm sensitive area, which covers the full synchrotron radiation beam. The procedure consists of five building blocks, namely dynamic flat-fielding, gap seaming, dynamic ring removal, projection despeckling and around-gap equalization. Each block is discussed and compared, when existing, with conventional approaches. The effectiveness of the pre-processing is demonstrated for phase-contrast CT images of a human breast specimen. The dynamic nature of the proposed procedure, which provides corrections dependent upon the projection index, allows the effective removal of time-dependent artifacts, preserving the main image features including phase effects.