Charge Cloud Tracker : A High-Resolution, High-DQE, Photon-Counting Energy-Discriminating X-ray Detector

描述（申请人提供）：我们设计了一种新型的光子计数，能量鉴别x射线探测器；我们假设我们的设计可以提供5微米量级的极限分辨率，同时还提供非常高的x射线检测效率和25 keV光子的足够计数率。基本的探测器单元价格低廉，制造简单，而且不易辐射。探测任务的复杂性转移到高速电子和数据采集系统，该系统将处理每一个光子产生的电荷云，以确定光子的能量和相互作用的位置。该设计可以使用几种不同的半导体材料中的一种来实现，从而使临床应用的x射线能量范围从15 keV到50 keV。该项目的总体目标是为探测器的优化提供工具，并证明使用硅实现的原型可以实现超高分辨率，用于检测25 keV光子。我们将结合三个部分建立探测器的数值模型：1。硅中光子相互作用的蒙特卡罗模拟；2. 详细描述了电子的能量损失机制，以提供Si中初始电荷云分布的完整知识；和3。偏置场分布和电荷通过硅的路径模型。结合这三个组件，可以预测给定探测器几何形状、应用偏置场和读出电子设计的测量信号。我们还将构建探测器的第一个原型（有些次优），以验证模型，并验证关于可实现分辨率的假设。最终的研究成果将是一个精确且经过验证的Si探测器的数值模型，然后可以用于优化探测器的临床前（或乳房成像）版本的几何形状和电子设计。我们最初的临床目标是使新型x射线相位对比成像系统（基于传播和基于光栅）易于实现和剂量效率-因此需要高分辨率和高量子检测效率。然而，由于我们的设计是光子计数和能量鉴别，相同的基本探测器设计也将提供改进的剂量效率（在15%到60%的顺序取决于CT成像任务），以及适用于其他新的成像任务，如k-和l-壳层荧光成像。

DESCRIPTION (provided by applicant): We have designed a novel photon-counting, energy discriminating x-ray detector; we hypothesize that our design can provide limiting resolution on the order of 5 microns, while also providing very high x-ray detection efficiency and adequate count rates for 25 keV photons. The basic detector unit is inexpensive and simple to manufacture, as well as radiation hard. The complexity of the detection task is shifted to the high-speed electronics and data acquisition system, which will process every single photon-created charge cloud to determine the photon's energy and position of interaction. The design could be implemented using one of several different semiconductor materials, thereby enabling clinical applications at x-ray energies ranging from 15 keV to 50 keV. This project has the overall goal of providing the tools for optimization of the detector, as well as demonstrating that ultra-high resolution can be achieved using a prototype implemented in Silicon for detection of 25 keV photons. We will build a numerical model of the detector by combining three components: 1. a Monte-Carlo simulation of photon interactions in Si; 2. a detailed description of energy-loss mechanisms for electrons to provide complete knowledge of initial charge cloud distribution in Si; and 3. a model of bias field distribution and resulting path of charges through the Si. Combining the three components permits prediction of measured signal for a given detector geometry, applied bias field and readout electronics design. We will also build a first (somewhat sub-optimal) prototype of the detector to permit validation of the model, and to permit verification of the hypothesis regarding achievable resolution. The final research product will be an accurate and validated numerical model of the Si detector, which can then be used to optimize the geometry and electronics design for a pre-clinical (or breast imaging) version of the detector. Our initial clinical goal is to enable novel x-ray phase contrast imaging systems (both propagation-based and grating-based) that are both simple to implement and dose efficient - hence the need for high resolution and high quantum detection efficiency. However, since our design is photon counting and energy-discriminating, the same basic detector design would also provide improved dose efficiency (on the order of 15% to 60% depending on the imaging task in CT) as well as being applicable to other novel imaging tasks such as k- and l-shell fluorescence imaging.