Quasi-ideal photon counting x-ray CT with multi-energy inter-pixel coincidence counter (MEICC)

项目摘要 我们提出了一种技术解决方案，使接近理想的光子计数探测器（PCD）的X射线 计算机断层扫描（CT），这将使大多数临床梦想周围PCD-CT变成现实。我们称 提出了一种多能量像素间符合计数器（MEICC）的设计方案，并证明了该方案的可行性 MEICC的原理和算法。我们计划提供一个概念验证， 通过对MEICC的细节工作、优化设计和性能研究， 使用蒙特卡罗（MC）模拟的MEICC。PCD-CT有望成为下一代X射线CT。它有 巨大的潜力，例如改进当前的CT图像，还可以实现新的临床应用，例如 更高的空间分辨率，更好的软组织对比度，更强的造影剂增强，辐射剂量 复位、定量CT成像和生物标志物、准确的软组织材料表征、K边缘 成像和同时多造影剂成像。研究表明，最新的PCD足以 快速临床X射线CT和几个小组开发了原型全身PCD-CT系统，并安装 在2014-2018年进行beta测试。研究表明，PCD-CT具有巨大的潜力。但是， 原型PCD-CT没有达到很高的期望。事实上，有时候， 因为PCD像素之间存在一种称为“电荷共享”的现象，它会增加噪音 方差因子为4，降低了空间分辨率，降低了能量响应，并削弱了 光谱信号总体而言，它对PCD-CT的性能有显著的负面影响。电荷共享 是探测物理学所固有的，电荷共享的概率约为70%。因此，不可能 避免，这是一个非常关键的问题，需要加以解决。MEICC将解决噪声和偏置问题， 电荷共享MEICC使用能量相关符合计数器，保持电荷共享的书 事件，并使用事件发生后的确切次数对其进行校正。 收购已经完成。MEICC不会干扰主要计数过程;因此，带有MEICC的PCD 将保持与没有MEICC的人一样快。MEICC可以使用当今的电子技术来实现 因为它的像素间重合计数器是简单的和数字的。我们假设MEICC可以消除 电荷共享效应，将噪声降低到最低水平，增强信号，提高能量 响应，并且总的来说，能够实现几乎理想的X射线PCD-CT。我们计划通过完成 以下3个具体目标：（SA 1）开发MEICC设计和算法;（SA 2）开发MC仿真 （SA 3）评估MEICC和其他完成技术的特定任务性能， Cramér-Rao下限作为主要品质因数。

Project Summary We propose a technical solution that enables nearly ideal photon counting detectors (PCDs) for x-ray computed tomography (CT), which will bring most of clinical dreams surrounding PCD-CT into reality. We call the solution multi-energy inter-pixel coincidence counter (MEICC) and it is feasible to implement the design and algorithm of MEICC using today’s electronics technology. We plan to provide a proof of concept that will “move the needle” by working on the detail of MEICC, optimizing the design and studying the performance of MEICC using Monte Carlo (MC) simulations. PCD-CT is expected to be the next generation of x-ray CT. It has great potentials such as improve the current CT images but also to enable new clinical applications, such as higher spatial resolution, better soft tissue contrast, stronger contrast agent enhancement, radiation dose reduction, quantitative CT imaging and biomarkers, accurate soft tissue material characterization, K-edge imaging, and simultaneous multi-contrast agent imaging. Studies showed that latest PCDs were sufficiently fast for clinical x-ray CT and several groups developed prototype whole-body PCD-CT systems and installed them for a beta test in 2014–2018. Studies have shown great potential of PCD-CT. But, the performance of the prototype PCD-CT did not meet high expectations. In fact, the performance was sometimes comparable to that of dual-energy CT because of a phenomenon called “charge sharing” between PCD pixels. It increases noise variance by a factor of 4, degrades the spatial resolution, degrades the energy response, and weakens the spectral signals. Overall, it has a significantly negative impact on the performance of PCD-CT. Charge sharing is inherent to the detection physics and the probability of charge sharing is ~70%. Thus, it is impossible to avoid and is a very critical issue that needs to be addressed. MEICC will address both noise and bias added by charge sharing. MEICC uses energy-dependent coincidence counters, keeps the book of charge sharing events during the data acquisition, and corrects them using the exact number of the occurrences after the acquisition is completed. MEICC does not interfere with the primary counting process; thus, PCDs with MEICC will remain as fast as those without MEICC. MEICC can be implemented using today’s electronics technology because its inter-pixel coincidence counters are simple and digital. We hypothesize that MEICC can eliminate the effect of charge sharing, decrease noise to the minimal level, enhance signals, improve the energy response, and over all, enable nearly ideal x-ray PCD-CT. We plan to test the hypothesis by accomplishing the following 3 specific aims: (SA1) Develop MEICC designs and algorithms; (SA2) develop MC simulation programs; (SA3) assess the task-specific performance of MEICC and other completing technologies using Cramér–Rao lower bound as the primary figure of merit.