Liao R, Williams J A, Myers L, Li S, Taylor R H, Davatzikos C
Department of Radiology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21287, USA.
Comput Aided Surg. 2000;5(4):220-33. doi: 10.1002/1097-0150(2000)5:4<220::AID-IGS2>3.0.CO;2-O.
Computer-assisted treatment planning for linac-based radiosurgery is still an open research problem, especially for multiple-isocenter procedures, primarily due to its high complexity and computational requirements. This paper focuses on the optimization of multiple-isocenter treatment planning for linac systems, and addresses several important issues associated with multiple isocenters, such as dose conformality, homogeneity, and optimization of isocenter position and dose.
The key idea behind our approach is that the desired dose distribution can be decomposed into a number of fundamental components. In the current paper, an analytical form, the so-called Ellipsoidal Dose Distribution Estimation (EDDE) model, represents each component. We establish ways (arc configurations) to achieve such ellipsoidal doses of arbitrary position, orientation, and size. Since the EDDE model is described by relatively few parameters, it allows very quick estimation of the dose distribution corresponding to a particular isocenter and thus makes the optimization of isocenter position very efficient. It is further used in a framework for optimal treatment planning, in which a number of ellipsoidal dose distributions, each corresponding to a different isocenter, are optimally placed to cover the target while sparing healthy tissue.
The general ellipsoidal dose distribution of linac-based radiosurgery is summarized as a mathematical model with the aid of supporting experiments. Comparisons between the EDDE-optimized and clinically implemented plans are made, revealing the superior performance of the former. In addition, a dramatic reduction in planning time is achieved using the EDDE model.
The proposed EDDE model is a useful and effective dose model in multiple-isocenter treatment planning for linac-based radiosurgery.
基于直线加速器的放射外科手术的计算机辅助治疗计划仍是一个开放的研究问题，特别是对于多等中心程序，主要是由于其高度的复杂性和计算要求。本文重点关注直线加速器系统多等中心治疗计划的优化，并解决与多个等中心相关的几个重要问题，如剂量适形性、均匀性以及等中心位置和剂量的优化。
我们方法背后的关键思想是，期望的剂量分布可以分解为多个基本成分。在本文中，一种解析形式，即所谓的椭球剂量分布估计（EDDE）模型，代表每个成分。我们建立了实现任意位置、方向和大小的这种椭球剂量的方法（弧形配置）。由于EDDE模型由相对较少的参数描述，它允许非常快速地估计对应于特定等中心的剂量分布，从而使等中心位置的优化非常有效。它进一步用于最佳治疗计划框架中，其中多个椭球剂量分布，每个对应于不同的等中心，被最佳放置以覆盖靶区同时保护健康组织。
借助支持性实验，总结了基于直线加速器的放射外科手术的一般椭球剂量分布作为一个数学模型。对EDDE优化计划和临床实施计划进行了比较，揭示了前者的优越性能。此外，使用EDDE模型使计划时间大幅减少。
所提出的EDDE模型在基于直线加速器的放射外科手术的多等中心治疗计划中是一个有用且有效的剂量模型。
