Optimized Cone-Beam CT for Image-Guided Radiation Therapy

描述（由申请人提供）：在放射治疗（RT）中，必须向含有恶性肿瘤的靶体积提供规定的高剂量辐射，同时保留周围的正常组织。这是通过在整个RT过程中广泛使用成像来完成的。计算机断层扫描（CT）是图像引导放射治疗（IGRT）的主要成像工具。具有锥形束CT （CBCT）成像能力的模拟器单元已成为RT计划系统的一部分。最近，在直线加速器（LINAC）处理系统上也开发了一种能够进行CBCT成像的千伏x射线成像仪（简称车载成像仪）。机载成像仪提供了一个独特的机会，在治疗之前，期间和之后产生患者的准确图像表示。这些系统适用于两大类RT任务，每一类任务在图像质量、获取速度和患者剂量最小化方面都有自己的一组要求。第一类包括诸如涉及CBCT治疗计划的任务，其目标是获得诊断图像质量并在复杂场景中识别未知物体。第二类包括使用CBCT进行定位等任务，其目标是识别相对于规划扫描的位置差异，并识别已知物体的姿态。该项目的目标是利用机载成像仪作为测试平台，通过开发创新的扫描配置和算法，充分利用硬件功能和最新的算法进步，在IGRT中产生准确和剂量有效的体积图像。该项目的具体目标是：(1)开发用于放疗CBCT成像的创新扫描配置；(2)开发放疗CBCT成像的图像重建算法；(3)补偿放疗CBCT成像中的物理因素；(4)评估放疗CBCT成像的扫描配置和算法。我们最近在CBCT算法方面取得了重大突破。可以设计算法，从部分覆盖患者的x射线照明和一般扫描配置获得的CBCT数据中，在感兴趣区域（ROI）内精确重建图像。我们的目标ROI成像策略类似于调强放射治疗。减少患者剂量，分散，避免关键脏器重复照射。我们相信，我们在影像学和放射治疗研究中积累的专业知识和见解使我们处于独特和强大的地位，能够成功并及时地完成IGRT中CBCT成像优化的拟议研究。

DESCRIPTION (provided by applicant): In radiation therapy (RT), it is essential to deliver a prescribed high radiation dose to a target volume containing malignancy while sparing surrounding normal tissues. This is accomplished by extensive use of imaging throughout the RT process. Computed tomography (CT) is the dominant imaging tool in image- guided radiation therapy (IGRT). Simulator units with cone-beam CT (CBCT) imaging capabilities have become available as part of RT planning systems. Recently, a KV X-ray imager, referred to as the on-board imager, capable of CBCT imaging has also been developed on the linear accelerator (LINAC) treatment system. The on-board imager offers a unique opportunity to yield accurate image representation of the patient before, during, and after treatment sessions. There are two broad classes of RT tasks to which these systems are suited, and each task class has its own set of requirements on image quality, acquisition speed, and patient dose minimization. The first class includes tasks such as those involving CBCT for treatment planning, where the objective is to obtain diagnostic image quality and to identify unknown object in a complex scene. The second class includes tasks such as those using CBCT for localization, where the objective is to recognize differences in position relative to the planning scan and to identify pose of known objects. The goal of the project is to, using the on-board imager as the test-bed platform, capitalize fully on the hardware capabilities and on recent algorithm advances through developing innovative scanning configurations and algorithms to yield accurate and dose-efficient volumetric images in IGRT. The specific aims of the project are: (1) To develop innovative scanning configurations for radiotherapy CBCT imaging; (2) To develop image-reconstruction algorithms for radiotherapy CBCT imaging; (3) To compensate for the physical factors in radiotherapy CBCT imaging; and (4) To evaluate the scanning configurations and algorithms for radiotherapy CBCT imaging. We have recently made significant breakthroughs in CBCT algorithms. Algorithms can be designed for accurate image reconstruction within regions-of-interest (ROI) from CBCT data acquired with X-ray illumination that partially covers the patient and with general scanning configurations. Our strategy for targeted ROI imaging resembles that of the intensity-modulated radiation therapy. It can reduce patient dose and scatter and avoid repeated illumination of critical organs. We believe that our expertise and insights developed and accumulated in our studies in both imaging and radiation therapy have placed us in a unique and strong position to perform and accomplish the proposed research on optimization of CBCT imaging in IGRT successfully and in a timely manner.