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成像研究表明，患者结构和软组织位置变化很大。因此，感兴趣器官的剂量分布在放射治疗过程中存在显著的时间变化，是放射治疗定量分析中最困难的问题之一。如果不完全了解这种变化，治疗结果，特别是正常组织剂量反应，就不能正确地与处方剂量相关，从而阻碍了可靠的治疗评估和优化。这一根本问题在高适形治疗下进一步恶化。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(如调强放射治疗)的潜力至关重要。如果变化被量化，关键正常结构中剂量分布的时间变化的知识可以被用来改进正在进行的治疗。否则，TVODD仍然是治疗过程中不确定的一个主要来源。为了验证我们的假设，我们将实现以下具体目标：(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和评估系统中，并进行研究以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)通过使用从植入放射标志物的患者身上收集的多幅CT图像在体内验证基于图像的器官配准；(3)进行临床研究，以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。探索实用方法，将从图像反馈估计的器官剂量分布的时间变化包括在治疗计划优化中。

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.