Temporal Variation of Organ Dose Distribution in RT

描述（由申请人提供）：在放射治疗过程中进行的大量影像学研究表明，患者设置和软组织位置发生了实质性变化。因此，在放射治疗过程中，感兴趣器官（TVODD）的剂量分布存在显著的时间变化，是放射定量分析的难点之一。如果不充分了解这种变化，治疗结果，特别是正常组织剂量反应，就不能正确地与规定剂量相关联，从而妨碍可靠的治疗评估和优化。高适形治疗进一步加剧了这一基本问题。我们的假设是，量化放射治疗中的TVODD对于实现先进治疗技术（例如IMRT）的潜力至关重要。如果对临界正常结构中剂量分布的时间变化进行量化，则可以利用对剂量分布时间变化的了解来改进正在进行的治疗。否则，TVODD仍然是治疗过程中不确定性的主要来源。为了验证我们的假设，我们将追求以下具体目标：(1)将软组织生物力学模型和有限元算法集成到基于图像的器官配准与评估系统中，并进行研究，确定配准模型对组织力学特性和器官边界条件变化的敏感性；(2)在体内验证基于图像的器官配准，使用从嵌入放射性标志物的患者身上收集的多幅CT图像；(3)开展临床研究，确定器官剂量分布的时间变化对治疗计划评估和决策的潜在影响。探索实用的方法，包括器官剂量分布的时间变化，从图像反馈估计，在治疗计划的优化。

DESCRIPTION (provided by applicant): A large number of imaging studies performed during the course of radiation treatment have indicated substantial patient setup and soft tissue position variation. Consequently, significant temporal variation of dose distribution in organs of interest (TVODD) exists during the course of radiotherapy and presents itself as one of the most difficult problems for quantitative radiotherapy analysis. Without fully understanding this variation, the treatment outcome, particularly normal tissue dose response, cannot be correctly correlated to the prescribed dose, thereby preventing reliable treatment evaluation and optimization. This fundamental problem is further exacerbated for a high conformal treatment. It is our hypothesis that quantifying TVODD in radiotherapy is essential for realizing the potential of advanced treatment technologies (e.g. IMRT). Knowledge of the temporal variation of the dose distribution in critical normal structures can be exploited to improve ongoing treatment, if the variation is quantified. Otherwise, TVODD remains as a major source of uncertainty in the treatment process. To test our hypothesis, the following Specific Aims will be pursued: (1) Integrate a soft tissue biomechanics model and finite element algorithm into the image based organ registration and evaluation system, and perform a study to determine the sensitivity of the registration model to variations of tissue mechanical properties and organ boundary conditions, (2) Validate the image based organ registration, in vivo, by using multiple CT images collected from patients with embedded radiomarkers, (3) Perform clinical studies to determine the potential impact of temporal variation of organ dose distribution on treatment planning evaluation and decisions. Explore practical methods to include temporal variation of organ dose distribution, estimated from image feedback, in treatment planning optimization.