On the role of modeling parameters in IMRT plan optimization.
On the role of modeling parameters in IMRT plan optimization.
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关于建模参数在 IMRT 计划优化中的作用。
DOI：
10.1088/0031-9155/53/18/004
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发表时间：
2008
影响因子：
3.5
通讯作者：
Thieke,Christian
中科院分区：
文献类型：
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作者：
Krause,Michael;Scherrer,Alexander;Thieke,Christian
调强放射治疗(IMRT)计划中的优化问题包括各种值的选择，例如特定功能的参数或约束范围。在当前的反向计划计划中，每个优化只产生一个治疗计划，通常不清楚这些建模参数对结果计划的影响有多大。这项工作研究了弹性和灵敏度的数学概念来处理这个问题。研究了一个圆形风险结构周围具有不同开启角度的马蹄形目标的人工规划问题。作为评价函数，使用广义等效均匀剂量(EUD)和低于一定剂量阈值的平均不足剂量和超过一定剂量阈值的平均过量剂量。针对示例性参数配置计算单个调强放射治疗计划。然后在不重新优化的情况下计算各参数的弹性和灵敏度，并对结果进行了数值验证。研究结果表明：(1)弹性理论可以根据目标函数值随参数变化的大小来量化建模参数对优化结果的影响。灵敏度分析基于当前的参数设置和相应的处理方案，无需重新优化即可对修改后的参数值预测优化结果，并可估计预测有效的值区间。总之，弹性和敏感性可以在逆向调强放射治疗计划中提供有用的工具，以确定单个计划问题的最关键参数，并以适当的方式修改它们的值。
The formulation of optimization problems in intensity-modulated radiotherapy (IMRT) planning comprises the choice of various values such as function-specific parameters or constraint bounds. In current inverse planning programs that yield a single treatment plan for each optimization, it is often unclear how strongly these modeling parameters affect the resulting plan. This work investigates the mathematical concepts of elasticity and sensitivity to deal with this problem. An artificial planning case with a horse-shoe formed target with different opening angles surrounding a circular risk structure is studied. As evaluation functions the generalized equivalent uniform dose (EUD) and the average underdosage below and average overdosage beyond certain dose thresholds are used. A single IMRT plan is calculated for an exemplary parameter configuration. The elasticity and sensitivity of each parameter are then calculated without re-optimization, and the results are numerically verified. The results show the following.(1) elasticity can quantify the influence of a modeling parameter on the optimization result in terms of how strongly the objective function value varies under modifications of the parameter value. It also can describe how strongly the geometry of the involved planning structures affects the optimization result.(2) Based on the current parameter settings and corresponding treatment plan, sensitivity analysis can predict the optimization result for modified parameter values without re-optimization, and it can estimate the value intervals in which such predictions are valid. In conclusion, elasticity and sensitivity can provide helpful tools in inverse IMRT planning to identify the most critical parameters of an individual planning problem and to modify their values in an appropriate way.