Image Science for the New X-Ray: Taking Dual-Energy CT to Task

描述(申请人提供)：虽然医学X射线成像的第一个世纪通过投影成像和计算机断层扫描(CT)提供了前所未有的进步，但其第二个世纪将标志着对X射线光谱和断层扫描信息的更智能的应用和利用，新颖的源-探测器配置，以及最大限度地减少辐射剂量。最近在低剂量CT、双能量CT和锥束CT(CBCT)方面的工作证明了这一点，在最近关于CT应用的科学和普及交流中也是如此。DE-CT应用于腹部(例如肾结石)、肌肉骨骼(MSK，例如关节炎)和神经(例如，灌注)成像。光谱/层析成像技术的知识进步的关键是性能评估和优化的基础，它不仅考虑X射线探测和图像重建的物理，而且还考虑成像任务--而且--以最大限度地提高任务性能同时最大限度地减少辐射剂量的方式。此项目续订建立在原始R01的成功基础上，在该R01中，基于任务的成像性能框架扩展到DE成像和CBCT，提供：i.)从噪声当量(NEQ)等基本傅里叶域指标到真实和模型观测器性能的桥梁；ii.)优化远程教育和CBCT新技术的量化框架；以及一种方法被证明可以在知识上加速新技术向关键临床应用的转化。通过结合DE成像和CBCT的模型，目前的工作旨在开发一个DE-CBCT成像性能的框架，解决与新的探测器技术和图像分解技术有关的挑战，并将结果专门应用于用于MSK成像的新型DE-CBCT原型。这项建议的目的是：1.为DE-CBCT性能建立一个基于任务的模型框架，将NEQ与特定的检测/识别任务联系起来，为系统优化和剂量最小化提供基础；将框架扩展到能量集成和能量辨别探测器技术(即平板探测器和光子计数器)，并在体模和身体中验证性能与台式测量的对比；将该框架扩展到基于重建和基于投影的DE-CBCT图像分解，包括降噪算法，以阐明各自的优势并优化在特定成像任务中的实现；将结果转换到原型MSK肢体CBCT扫描仪(已经在单独的项目中建造)，以实施和评估MSK成像任务(例如，钙碘、钙尿酸和固有软组织识别)中的最佳DE-CBCT技术。这项工作的成功完成为评估新的和现有的DE-CT/CBCT系统提供了一个量化框架，为这一快速发展的技术的知识翻译提供了指南，为将成像任务中的辐射剂量降至最低提供了量化基础，并在MSK成像(例如骨关节炎、痛风、软组织和骨肿瘤以及组织撞击综合征)的应用方面取得了具体进展。 与公共卫生相关：新兴的X射线光谱断层扫描技术(通常为双能CT)突破了单能CT对比度分辨率的传统限制，在诊断和治疗评估方面取得了重大进展，这些疾病具有明显的生化变化特征，例如关节炎(包括骨关节炎、痛风和类风湿性关节炎)、肾结石，以及使用碘或新型造影剂进行血管或关节内对比剂增强。随着这类技术在更大范围内的扩散(例如，在全国各地建立的“痛风中心”)的发展，迫切需要一种图像科学基础，以定量地了解控制成像性能的因素，确定最佳成像技术，并以保持成像任务性能的方式将辐射剂量降至最低。这项建议提出了光谱断层成像的图像科学框架，以产生技术优化的验证模型，指导新的双能量CT探测器和算法的开发，并将这一理解专门转化为肌肉骨骼肢体的扫描仪原型(例如，关节炎、痛风、软骨退化和组织撞击综合征的成像)。

DESCRIPTION (provided by applicant): While the first century of medical x-ray imaging offered an unprecedented advance via projection imaging and computed tomography (CT), its second century will be marked by more intelligent application and utilization of x-ray spectral and tomographic information, novel source-detector configurations, and minimization of radiation dose. Such is evidenced by recent work in low-dose CT, dual-energy (DE) CT, and cone-beam CT (CBCT) and is crystal clear in recent scientific and popular communication of CT utilization. Application of DE-CT is seen in abdominal (e.g., renal calculi), musculoskeletal (MSK, e.g., arthritis), and neuro (e.g., perfusion) imaging. Key to the knowledgeable advance of spectral / tomographic techniques is a basis for performance assessment and optimization that considers not only the physics of x-ray detection and image reconstruction, but also the imaging task - and moreover - in a manner that maximizes task performance while minimizing radiation dose. This project renewal builds on the success of the original R01 in which a task-based framework for imaging performance was extended to DE imaging and CBCT, providing: i.) a bridge from fundamental Fourier-domain metrics such as noise-equivalent quanta (NEQ) to real and model observer performance; ii.) a quantitative framework for optimization of new DE and CBCT technologies; and iii.) an approach shown to accelerate translation of new technology knowledgeably to key clinical applications. By combining the models for DE imaging and CBCT, the current work aims to develop a framework for imaging performance in DE-CBCT, tackling challenges that beckon in regard to new detector technologies and image decomposition techniques and applying the results specifically to a novel DE-CBCT prototype for MSK imaging. The aims of the proposal are to: 1.) Establish a model task-based framework for DE-CBCT performance that relates NEQ to specific detection / discrimination tasks and provides a basis for system optimization and dose minimization; 2.) Extend the framework to energy-integrating and energy-discriminating detector technology (viz., flat-panel detectors and photon counters) and validate performance versus benchtop measurements in phantom and cadaver; 3.) Extend the framework to reconstruction-based and projection-based DE-CBCT image decomposition, including noise reduction algorithms, to elucidate the advantages of each and optimize implementation in specific imaging tasks; and 4.) Translate the results to a prototype MSK extremities CBCT scanner (already constructed in a separate project) to implement and evaluate optimal DE-CBCT techniques in MSK imaging tasks (e.g., calcium-iodine, calcium-uric acid, and intrinsic soft-tissue discrimination). Successful completion of the work offers a quantitative framework for evaluation of new and existing DE-CT/CBCT systems, a guide to knowledgeable translation of this rapidly proliferating technology, a quantitative basis for minimizing radiation dose with respect to the imaging task, and a specific advance in application to MSK imaging (e.g., osteoarthritis, gout, soft-tissue and bone tumors, and tissue impingement syndromes). PUBLIC HEALTH RELEVANCE: Emerging technologies for x-ray spectral tomography (commonly, dual-energy CT) offer to transcend conventional limitations of contrast resolution in single-energy CT and present a significant advance to diagnosis and therapy assessment in a broad range of pathologies characterized by distinct biochemical change - e.g., arthritis (including osteoarthritis, gout, and rheumatoid arthritis), kidney stones, and vascular or intra-articular contrast enhancement using iodine or novel contrast agents. As such technology advances in broader proliferation (e.g., in "Gout Centers" established around the country), there is an immediate need for an image science basis for quantitatively understanding the factors that govern imaging performance, identifying optimal imaging techniques, and minimizing radiation dose in a manner that maintains performance of the imaging task. This proposal advances an image science framework for spectral tomographic imaging to yield a validated model for technique optimization, guiding the development of new dual-energy CT detectors and algorithms, and translating the understanding specifically to a scanner prototype for musculoskeletal extremities (e.g., imaging of arthritis, gout, cartilage degeneration, and tissue impingement syndromes).