Image Science for the New X-ray: Taking NEQ to Task

描述(申请人提供)：平板成像仪(FPI)正在许多先进的X射线成像方式中进行研究，这些成像方式提供改进的组织可视化和深度辨别，包括双能量(DE)成像、断层合成和锥束CT(CBCT)。每一种都代表了一种很有前途的诊断和图像引导程序技术。在DE成像中，在不同的X射线能量下获得的两个图像被处理以产生骨或软组织的图像。在断层合成和CBCT中，X射线源和FPI在患者周围移动，从多个角度重建3D图像。实现这些模式的全部潜力需要对成像性能进行定量评估，并需要一种方法来揭示限制图像质量的物理因素。传统的基于傅里叶变换的度量方法，如噪声当量量子(NEQ)，为空间分辨率和信噪比提供了实用、普遍的品质因数。然而，对于这些先进的成像模式，目前没有严格的性能计量(基于傅立叶或其他)；此外，NEQ通常只描述探测器的性能，而不考虑图像中感兴趣的结构(即任务)或观察者的反应。这项提议在这些高级模式中采用了一种基本的图像科学方法来进行绩效评估，在许多方面都取得了新的进展。NEQ和相关的傅立叶度量被扩展到每一种高级模式，以提供成像性能评估的实验和理论方法；图像中感兴趣的结构根据成像任务进行量化，考虑与两种最致命的癌症(肺癌和肝转移癌)相关的各种简单和更高阶的任务(检测、定位和大小估计)；成像任务和NEQ的定量公式被严格组合，以产生用于DE成像、断层合成和CBCT中成像性能的基于任务的度量，并且通过与人类观察者的反应的相关性来验证这种基于任务的度量提供图像质量的有意义的替代的程度。因此，这一建议开始通过对成像任务的严格量化来弥合流行的基于傅立叶的方法和传统的基于观察者的方法(例如ROC分析)之间的差距。例如，使用DE成像和断层合成的检测和大小估计任务来评估早期发现肺结节的成像性能，而根据CBCT的定位任务来评估射频消融或肝转移瘤放射治疗的指导。该项目的成功完成将为这些和其他新型成像模式的设计、评估和优化提供一种实用的、任务驱动的方法。

DESCRIPTION (provided by applicant): Flat-panel imagers (FPIs) are being investigated in a host of advanced x-ray imaging modalities that offer improved tissue visualization and depth discrimination, including dual-energy (DE) imaging, tomosynthesis, and cone-beam CT (CBCT). Each represents a promising technology for diagnostic and image-guided procedures. In DE imaging, two images acquired at different x-ray energies are processed to yield images of bone or soft-tissue. In tomosynthesis and CBCT, the x-ray source and FPI move about the patient, and 3D images are reconstructed from multiple perspectives. Realizing the full potential of these modalities requires quantitative evaluation of imaging performance and a methodology for revealing the physical factors that limit image quality. Conventional Fourier-based metrics, such as Noise-Equivalent Quanta (NEQ), provide practical, prevalent figures of merit for spatial resolution and signal-to-noise ratio. For these advanced imaging modalities, however, there is currently no rigorous performance metrology (Fourier-based or otherwise); furthermore, the NEQ conventionally describes only the performance of the detector, and considers neither the structures of interest in the image (i.e., the task) nor the response of observers. This proposal pursues a fundamental image science approach to performance evaluation in these advanced modalities, breaking new ground in numerous respects: 1.) The NEQ and associated Fourier metrics are extended to each of the advanced modalities to provide an experimental and theoretical methodology for imaging performance evaluation; 2.) Structures of interest in the image are quantified in terms of the imaging t ask, considering a variety of simple and higher-order tasks (detection, localization, and size estimation) in relation to two of the most lethal cancers (lung carcinoma and liver metastases); and 3.) Quantitative formulations of imaging task and NEQ are rigorously combined to yield task-based metrics for imaging performance in DE imaging, tomosynthesis, and CBCT, and the extent to which such task-based metrics provide a meaningful surrogate for image quality is validated by correlation with the response of human observers. Hence, this proposal begins to bridge the gap between the prevalent Fourier-based approach and traditional observer-based approaches (e.g., ROC analysis) through rigorous quantitation of imaging task. For example, imaging performance in early detection of lung nodules is evaluated using Detection and Size Estimation tasks for DE imaging and tomosynthesis, while guidance of RF ablation or radiation therapy of liver metastases is evaluated in terms of a Localization task for CBCT. Successful completion of this program will offer a practical, task-driven approach to the design, evaluation, and optimization of these and other novel imaging modalities.