Austin-Seymour M, Kalet I, McDonald J, Kromhout-Schiro S, Jacky J, Hummel S, Unger J
Department of Radiation Oncology, University of Washington Medical Center, Seattle 98195-6043, USA.
Int J Radiat Oncol Biol Phys. 1995 Dec 1;33(5):1073-80. doi: 10.1016/0360-3016(95)00217-0.
Three dimensional (3D) target volumes are an essential component of conformal therapy because the goal is to shape the treatment volume to the target volume. The planning target volume (PTV) is defined by ICRU 50 as the clinical target volume (CTV) plus a margin to ensure that the CTV receives the prescribed dose. The margin must include all interfractional and intrafractional treatment variations. This paper describes a software tool that automatically generates 3D PTVs from CTVs for lung cancers and immobile head and neck cancers.
Values for the interfractional and intrafractional treatment variations were determined by a literature review and by targeted interviews with physicians. The software tool is written in Common LISP and conforms to the specifications for shareable software of the Radiotherapy Treatment Planning Tools Collaborative Working Group.
The tool is a rule-based expert system in which the inputs are the CTV contours, critical structure contours, and qualitative information about the specific patient. The output is PTV contours, which are a cylindrical expansion of the CTV. A model for creating PTVs from CTVs is embedded in the tool. The interfractional variation of setup uncertainty and the intrafractional variations of movement of the CTV (e.g., respiration) and patient motion are included in the model. Measured data for the component variations is consistent with modeling the components as independent samples from 3D Gaussian distributions. The components are combined using multivariate normal statistics to yield the cylindrical expansion factors. Rules are used to represent the values of the components for certain patient conditions (e.g., setup uncertainty for a head and neck patient immobilized in a mask). The tool uses a rule interpreter to combine qualitative information about a specific patient with rules representing the value of the components and to enter the appropriate component values for that patient into the cylindrical expansion formula.
The portable software tool allows the rapid, consistent, and automatic generation of 3D PTVs from CTVs.
三维（3D）靶区体积是适形治疗的重要组成部分，因为其目标是使治疗体积与靶区体积相匹配。国际辐射单位与测量委员会（ICRU）50号报告将计划靶区体积（PTV）定义为临床靶区体积（CTV）加上一个边界，以确保CTV能接受规定剂量。该边界必须包含所有分次间和分次内的治疗变化。本文介绍了一种软件工具，它可从肺癌及固定不动的头颈癌的CTV自动生成3D PTV。
通过文献综述及对医生的定向访谈确定分次间和分次内治疗变化的值。该软件工具用通用LISP编写，符合放射治疗计划工具协作工作组的可共享软件规范。
该工具是一个基于规则的专家系统，其输入为CTV轮廓、关键结构轮廓及有关特定患者的定性信息。输出为PTV轮廓，它是CTV的圆柱形扩展。从CTV创建PTV的模型嵌入在该工具中。模型包含设置不确定性的分次间变化以及CTV运动（如呼吸）和患者运动的分次内变化。各组成变化的测量数据与将这些组成部分建模为来自三维高斯分布的独立样本一致。使用多元正态统计将各组成部分组合起来以得出圆柱形扩展因子。规则用于表示特定患者情况（如戴面罩固定的头颈患者的设置不确定性）下各组成部分的值。该工具使用规则解释器将有关特定患者的定性信息与表示各组成部分值的规则相结合，并将该患者的适当组成部分值代入圆柱形扩展公式。
该便携式软件工具可从CTV快速、一致且自动地生成3D PTV。
