Development of a Photon Counting Detector for CT Breast Imaging

描述（由申请人提供）：为了提高乳腺癌的早期检测和诊断，一些研究小组一直在研究专用于乳房成像的x射线计算机断层扫描（CT）成像仪的使用。初步结果表明，与传统乳房x线照相术相比，专用乳腺CT系统可以提供更好的3D乳腺组织可视化。然而，目前正在研究的乳腺CT原型在使用的检测器、采集几何形状和信号处理方面存在局限性，导致空间分辨率、病变对比度和信噪比低于预期。这些CT原型也测量了大量的散射辐射，并且对胸壁附近的乳腺组织的检测器覆盖率不足。这些物理上的限制将使目前的乳腺CT技术无法在早期乳腺癌的检测和诊断中发挥最大的作用。本提案的总体目标是开发和验证一种创新的检测器系统和成像方法，以提高乳腺专用CT成像的性能。我们在此提出的CT乳房成像系统将使用在光子计数模式下工作的半导体探测器，以螺旋CT几何形状获取投影。一个多世纪以来，临床x射线成像设备一直以能量积分模式运行，通过在有限的采集时间内整合x射线事件形成图像。由于我们在提案中概述的一些原因，能量积分检测器的性能在乳房的CT成像中是次优的。然而，由于x射线CT中通常存在高计数率（即入射到探测器上的x射线流），因此在光子计数模式下操作CT探测器一直是不可能的。由于最近x射线探测器和相关电子学的技术改进，光子计数探测器用于乳房CT应用已经成为可能。模拟和建模将用于检查这种光子计数x射线CT系统的某些设计规范，并将构建原型，并通过成像乳房幻影和新鲜的乳房切除术标本进行验证。使用所提出的CT成像仪的台式原型，我们将验证其性能，并将其与使用间接转换，能量积分检测器的传统平板CT乳房成像仪进行比较。

DESCRIPTION (provided by applicant): In an effort to improve the early stage detection and diagnosis of breast cancer, a handful of research groups have been investigating the use of x-ray computerized tomographic (CT) imagers dedicated for use in imaging the breast. Preliminary results suggest that dedicated breast CT systems can provide improved visualization of 3D breast tissue as compared to conventional mammography. However, current breast CT prototypes that are being investigated have limitations in terms of detectors used, acquisition geometry and signal processing that result in less than desirable spatial resolution, lesion contrast, and signal-to-noise (SNR) ratio. These CT prototypes also measure a substantial amount of scattered radiation, and have inadequate detector coverage for breast tissue located near the chest wall. These physical limitations will prohibit current breast CT technology from providing the maximum performance in detecting and diagnosing early-stage breast cancer. The overall goal of this proposal is to develop and validate an innovative detector system and imaging methodology for improved performance in dedicated CT imaging of the breast. The CT breast imaging system that we propose herein will use semiconductor detectors operating in a photon counting mode, acquiring projections in a helical CT geometry. For over a century now, clinical x-ray imaging devices have operated in energy integrating mode, whereby images are formed by integrating x-ray events over a finite acquisition time. For a number of reasons which we outline in the proposal, the performance of energy integrating detectors are sub-optimal for use in CT imaging of the breast. However, due to the high count rate (i.e., x-ray fluence incident on the detector) typically present in x-ray CT, it has historically been impossible to operate CT detectors in a photon counting mode. Due to recent technological improvements in x-ray detectors and associated electronics, it has now become feasible for photon counting detectors to be used for breast CT applications. Simulation and modeling will be used to examine certain design specifications for such a photon- counting x-ray CT system, and a prototype will be constructed and validated by imaging breast phantoms and fresh mastectomy specimens. Using a bench-top prototype of the proposed CT imager, we will validate its performance and compare it to a conventional flat-panel CT breast imager using an indirect conversion, energy integrating detector. PUBLIC HEALTH RELEVANCE: Tomographic x-ray imaging dedicated to imaging of the breast can potentially improve the detection and diagnosis of breast cancer by providing radiologists with 3D images of the breast. This research proposes to develop an improved, innovative detector system for breast CT imaging.