Computational Tools for Adaptive Radiation Therapy

描述（由申请人提供）：分时段患者设置的不确定性和解剖结构的变化被广泛认为是最大限度地利用现代放射治疗技术的主要限制因素之一，如调强放射治疗（IMRT）。到目前为止，几乎所有的研究工作都集中在通过尝试更准确地重新定位患者来减少器官运动/变形的不利影响上。在临床上，IMRT治疗方案优化和剂量递送仍然是两个分离的步骤，考虑到基于人群的边缘包括临床靶体积的几何不确定性，这极大地影响了放射治疗的成功。近年来机载体积成像设备的出现为我们获得患者在治疗位置的3D甚至4D几何模型提供了有价值的工具，并允许在治疗过程中自适应修改IMRT计划。该项目的目标是为图像引导适应性放射治疗（IGART）开发使能的计算工具，并展示IGART新范式的潜在临床影响。这项工作的基本假设是IGART将大大减少光束靶向的不确定性，并提供大大改善的剂量分布，以实现更大的局部肿瘤控制，同时减少正常组织并发症的可能性。该项目的具体目标是：(1)建立一种基于锥形束CT （CBCT）的剂量重建方法，用于分数剂量和累积剂量的计算；(2)建立IGART规划的动态闭环框架；(3)证明拟议IGART的潜在临床影响。该项目的执行将证明IGART是可以实现的，并确定IGART相对于传统IMRT的改进水平。鉴于其在最佳补偿分数间几何不确定性以及先前分数中产生的剂量学误差方面的重大承诺，该项目的成功完成将导致癌症患者护理的实质性改善。

DESCRIPTION (provided by applicant): Interfractional patient setup uncertainty and anatomy change are widely recognized as one of the major limiting factors for maximum exploitation of modern radiation therapy techniques, such as intensity modulated radiation therapy (IMRT). Up to this point, almost all research efforts have been focused on reducing the adverse effects of organ movement/deformation by attempting to reposition the patient more accurately. Clinically, IMRT treatment plan optimization and dose delivery are still two decoupled steps, with the geometric uncertainties taking into account by population based margins encompassing the clinical target volume, which significantly compromises the success of radiation therapy. The recent advent of onboard volumetric imaging device provides a valuable tool for us to obtain 3D or even 4D geometric model of the patient in the treatment position and allows adaptive modification of IMRT plan during a course of treatment. The objective of this project is to develop enabling computational tools for image guided adaptive radiation therapy (IGART) and to show the potential clinical impact of the new paradigm of IGART. The underlying hypothesis of this work is that IGART will greatly reduce the uncertainty in beam targeting and provide substantially improved dose distributions required to achieve greater local tumor control while reducing the probability of normal tissue complications. Specific aims of the project are (1) to establish a cone beam CT (CBCT)-based dose reconstruction method for fractional and cumulative dose calculations; (2) to setup a dynamic closed-loop framework of IGART planning; and (3) to demonstrate the potential clinical impact of the proposed IGART. Execution of the project will demonstrate that the IGART is achievable and determine the level of improvement of IGART over the conventional IMRT. Given its significant promise in optimally compensating for interfractional geometric uncertainties as well as dosimetric errors incurred in previous fractions, successful completion of the project should lead to substantial improvement in cancer patient care. PUBLIC HEALTH RELEVANCE: Currently, a radiation therapy treatment plan is produced based on the patient's anatomical model from planning CT images acquired a few days or even weeks before treatment. Numerous investigations have revealed that there can be significant changes in the patient anatomy from day to day due to patient positioning uncertainties and physiologic and clinical factors. This project is aimed to develop enabling computational tools for a new paradigm of radiation therapy, referred to as image-guided adaptive radiation therapy (IGART), to eliminate the influence of inter-fractional anatomy change. IGART improves current radiation therapy by adaptively adjusting the beam parameters according to volumetric imaging data acquired with the patient in the actual treatment position.