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

描述（由申请人提供）：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，但其第二个世纪的标志将是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-探测器配置以及辐射剂量的最小化。低剂量CT、双能量（DE）CT和锥形束CT（CBCT）的最新工作证明了这一点，并且在最近的CT使用科学和流行传播中非常清楚。DE-CT的应用见于腹部（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，不仅考虑X射线检测和图像重建的物理学，而且还考虑成像任务-此外-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。该项目更新建立在原始R 01的成功基础上，其中基于任务的成像性能框架扩展到DE成像和CBCT，提供：i.）从诸如噪声等效量子（NEQ）的基本傅立叶域度量到真实的和模型观测器性能的桥梁; ii.）优化新DE和CBCT技术的定量框架;以及iii.）该方法被证明可以加速新技术在关键临床应用中的转化。通过结合DE成像和CBCT的模型，目前的工作旨在开发DE-CBCT成像性能的框架，解决新探测器技术和图像分解技术方面的挑战，并将结果专门应用于MSK成像的新型DE-CBCT原型。该提案的目的是：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/区分任务联系起来，并为系统优化和剂量最小化提供基础; 2.）将框架扩展到能量集成和能量鉴别探测器技术（即，平板探测器和光子计数器），并在体模和尸体中验证性能与台式测量的对比; 3.）将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，以阐明每种算法的优点并优化特定成像任务的实现;以及4.）将结果转换为MSK四肢CBCT扫描仪原型（已在单独项目中构建），以在MSK成像任务中实施和评估最佳DE-CBCT技术（例如，钙-碘、钙-尿酸和内在软组织辨别）。这项工作的成功完成为评估新的和现有的DE-CT/CBCT系统提供了一个定量框架，为这种快速扩散的技术的知识转化提供了指导，为最大限度地减少成像任务的辐射剂量提供了定量基础，并在MSK成像应用中取得了具体进展（例如，骨关节炎、痛风、软组织和骨肿瘤以及组织撞击综合征）。 公共卫生相关性：X射线能谱断层扫描（通常为双能CT）的新兴技术超越了单能CT中对比度分辨率的传统限制，并为以不同生化变化为特征的广泛病理的诊断和治疗评估带来了重大进展-例如，关节炎（包括骨关节炎、痛风和类风湿性关节炎）、肾结石和使用碘或新型造影剂的血管或关节内造影增强。随着这种技术在更广泛的扩散中进步（例如，在全国各地建立的“痛风中心”中），迫切需要一种图像科学基础，用于定量地理解控制成像性能的因素，识别最佳成像技术，并以保持成像任务性能的方式使辐射剂量最小化。该提案推进了光谱断层成像的图像科学框架，以产生用于技术优化的经验证的模型，指导新的双能量CT探测器和算法的开发，并将理解具体转化为用于肌肉骨骼四肢的扫描仪原型（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).