Stavro Jann, Goldan Amir H, Zhao Wei
Stony Brook University, Department of Radiology, Stony Brook, New York, United States.
J Med Imaging (Bellingham). 2018 Oct;5(4):043502. doi: 10.1117/1.JMI.5.4.043502. Epub 2018 Oct 30.
Photon counting detectors (PCD) have the potential to improve x-ray imaging; however, they are still hindered by high costs and performance limitations. By using amorphous selenium (a-Se), the cost of PCDs can be significantly reduced compared with modern crystalline semiconductors, and enable large-area deposition. We are developing a direct conversion field-shaping multiwell avalanche detector (SWAD) to overcome the limitation of low carrier mobility and low charge conversion gain in a-Se. SWAD's dual-grid design creates separate nonavalanche interaction (bulk) and avalanche sensing (well) regions, achieving depth-independent avalanche gain. Unipolar time differential (UTD) charge sensing, combined with tunable avalanche gain in the well region allows for fast response and high charge gain. We developed a probability-based numerical simulation to investigate the impact of UTD charge sensing and avalanche gain on the photon counting performance of different a-Se detector configurations. Pulse height spectra (PHS) for 59.5 and 30 keV photons were simulated. We observed excellent agreement between our model and previously published PHS measurements for a planar detector. The energy resolution significantly improved from 33 keV for the planar detector to for SWAD. SWAD was found to have a linear response approaching .
光子计数探测器（PCD）有潜力改善X射线成像；然而，它们仍然受到高成本和性能限制的阻碍。通过使用非晶硒（a-Se），与现代晶体半导体相比，PCD的成本可以显著降低，并能够进行大面积沉积。我们正在开发一种直接转换场整形多孔雪崩探测器（SWAD），以克服a-Se中载流子迁移率低和电荷转换增益低的限制。SWAD的双栅设计创建了单独的非雪崩相互作用（体）和雪崩传感（阱）区域，实现了与深度无关的雪崩增益。单极时间差分（UTD）电荷传感与阱区域中可调的雪崩增益相结合，实现了快速响应和高电荷增益。我们开发了一种基于概率的数值模拟，以研究UTD电荷传感和雪崩增益对不同a-Se探测器配置的光子计数性能的影响。模拟了59.5和30 keV光子的脉冲高度谱（PHS）。我们观察到我们的模型与之前发表的平面探测器的PHS测量结果之间有很好的一致性。能量分辨率从平面探测器的33 keV显著提高到SWAD的[此处原文缺失具体数值]。发现SWAD具有接近[此处原文缺失具体数值]的线性响应。
