Novel tileable scintillator-based photon counting detector for clinical X-ray CT

 描述(由申请人提供)：在提供高对比度诊断CT图像的同时将患者的辐射剂量降至最低一直是所有CT相关研究的中心。在这方面，探测器技术的改进(连同自动曝光控制和改进的重建算法)可能会产生最大的影响。目前工作在积分模式下的X射线CT探测器不能提供光谱信息，并且在采集的图像中引入了很大的电子噪声。目前的光子计数探测器(作为集成CT探测器的替代方案)是基于X射线到电信号的直接转换，这依赖于利用半导体材料(主要是Si、CdTe、CZT)。对于医学成像应用中的X射线能量，硅变得几乎是透明的，从而导致非常低的灵敏度和高患者剂量。CdTe和CZT已被用于这些能量范围，但与当前的CT探测器材料相比，带来了技术挑战和性能问题，如电荷共享、脉冲堆积和计数速率能力、相对较低的有效Z和低密度。此外，高纯度材料(例如CZT)的供应有限，可能会使临床应用的大面积检测器过于昂贵。虽然基于闪烁的探测器被用于临床核成像系统，但由于缺乏强光，它们不能满足临床CT系统在高通量下的所有严格要求 输出闪烁体具有较快的衰减时间，并且缺乏可靠的闪烁体像素化技术来制作小于0.5x0.5 mm2的像素。我们的目标是研究一种基于闪烁体的光子计数探测器的可行性，该探测器使用像素化高Z闪烁体和专用ASIC，其中每个ASIC像素都有一个内置的光电二极管、一个电荷灵敏前置放大器、一个具有可编程峰值时间的整形放大器、3-4个能量窗及其相关计数器。这项研究的意义在于通过使用我们的闪烁体像素化 随着技术的发展，高分辨率光子计数CT探测器的开发是可以以经济高效的方式实现的。该探测器将根据能量对入射X射线进行分类，并将根据临床CT成像的需要处理高达108光子/平方毫米/秒的入射X射线流量。

 DESCRIPTION (provided by applicant): Delivering high contrast diagnostic CT images while minimizing patient radiation dose has been the center of majority of all CT-related research. In this regard, improvement in the detector technology (alongside with automatic exposure control and improved reconstruction algorithms) may have the greatest impact. Current X- ray CT detectors operating in integration mode are not able to provide spectral information and also introduce large electronic noise in the acquired images. Current photon counting detectors (as alternative for integrating CT detectors) are based on direct conversion of the x-rays to electrica signal which relies on utilizing semiconductor materials (mainly Si, CdTe, CZT). For X-ray energies in medical imaging applications, Si becomes almost transparent resulting in a very low sensitivity and high patient dose. CdTe and CZT have been used for these energy ranges, however imposing technical challenges and performance issues such as charge sharing, pulse pileup and count rate capability, relatively low effective Z and low density compared with the current CT detector materials. Furthermore, limited availability of high purity materials (e.g. CZT can make a large area detector for clinical applications prohibitively expensive. While scintillation-based detectors are used in clinical nuclear imaging systems they cannot satisfy all the stringent requirements for clinical CT system at high flux mainly due to the lack of high light output scintillators with fast decay time as well as lack of reliable scintillator pixelation technologies to fabricate pixels smaller than 0.5x0.5 mm2. Our goal is to study the feasibility of a scintillator-based photon counting detector using pixelated high Z scintillator coupled with a dedicated ASIC where each ASIC pixel has a built-in photodiode, a charge sensitive preamplifier, a shaping amplifier with programmable peaking time, 3-4 energy windows and their associated counters. The significance of this research is that by using our scintillator pixelation technology, development of high-resolution photon counting CT detectors is achievable in a cost effective manner. The proposed detector will categorize the incident X-rays based on their energy and will handle the incident X-ray flux up to 108 photon/mm2/second as needed in clinical CT imaging.