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

 描述（由申请人提供）：提供高对比度诊断CT图像，同时最大限度地减少患者辐射剂量一直是大多数CT相关研究的中心。在这方面，探测器技术的改进（以及自动曝光控制和改进的重建算法）可能会产生最大的影响。当前以积分模式操作的X射线CT探测器不能提供谱信息，并且还在所采集的图像中引入大的电子噪声。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，Si变得几乎透明，导致非常低的灵敏度和高的患者剂量。CdTe和CZT已经用于这些能量范围，然而，与当前CT探测器材料相比，强加了技术挑战和性能问题，例如电荷共享、脉冲堆积和计数率能力、相对低的有效Z和低密度。此外，高纯度材料（例如CZT）的有限可用性可使得用于临床应用的大面积检测器过于昂贵。在临床核成像系统中使用基于闪烁的探测器时，主要由于缺乏高光，它们不能满足临床CT系统在高通量下的所有严格要求 具有快速衰减时间的输出闪烁体以及缺乏可靠的闪烁体像素化技术来制造小于0.5 × 0.5 mm 2的像素。我们的目标是研究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的高Z闪烁体与专用ASIC耦合，其中每个ASIC像素具有内置光电二极管、电荷敏感型放大器、具有可编程峰值时间的整形放大器、3-4个能量窗口及其相关计数器。本研究的意义在于，通过使用我们的闪烁体像素， 技术，高分辨率光子计数CT探测器的开发是以成本有效的方式实现的。所提出的探测器将根据入射X射线的能量对其进行分类，并将根据临床CT成像的需要处理高达108光子/mm 2/秒的入射X射线通量。

 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.