放疗中的实际稳健性评估 - 一种基于 PTV 的计划评估的光子和质子证明替代方法。
Practical robustness evaluation in radiotherapy - A photon and proton-proof alternative to PTV-based plan evaluation.
机构信息
Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands.
Holland Proton Therapy Center, Delft, The Netherlands; Department of Radiation Oncology, Erasmus Medical Center Cancer Institute, Rotterdam, The Netherlands.
出版信息
Radiother Oncol. 2019 Dec;141:267-274. doi: 10.1016/j.radonc.2019.08.005. Epub 2019 Sep 3.
BACKGROUND AND PURPOSE
A planning target volume (PTV) in photon treatments aims to ensure that the clinical target volume (CTV) receives adequate dose despite treatment uncertainties. The underlying static dose cloud approximation (the assumption that the dose distribution is invariant to errors) is problematic in intensity modulated proton treatments where range errors should be taken into account as well. The purpose of this work is to introduce a robustness evaluation method that is applicable to photon and proton treatments and is consistent with (historic) PTV-based treatment plan evaluations.
MATERIALS AND METHODS
The limitation of the static dose cloud approximation was solved in a multi-scenario simulation by explicitly calculating doses for various treatment scenarios that describe possible errors in the treatment course. Setup errors were the same as the CTV-PTV margin and the underlying theory of 3D probability density distributions was extended to 4D to include range errors, maintaining a 90% confidence level. Scenario dose distributions were reduced to voxel-wise minimum and maximum dose distributions; the first to evaluate CTV coverage and the second for hot spots. Acceptance criteria for CTV D98 and D2 were calibrated against PTV-based criteria from historic photon treatment plans.
RESULTS
CTV D98 in worst case scenario dose and voxel-wise minimum dose showed a very strong correlation with scenario average D98 (R > 0.99). The voxel-wise minimum dose visualised CTV dose conformity and coverage in 3D in agreement with PTV-based evaluation in photon therapy. Criteria for CTV D98 and D2 of the voxel-wise minimum and maximum dose showed very strong correlations to PTV D98 and D2 (R > 0.99) and on average needed corrections of -0.9% and +2.3%, respectively.
CONCLUSIONS
A practical approach to robustness evaluation was provided and clinically implemented for PTV-less photon and proton treatment planning, consistent with PTV evaluations but without its static dose cloud approximation.
背景与目的
在光子治疗中，计划靶区（PTV）旨在确保即使存在治疗不确定性，临床靶区（CTV）也能接收到足够的剂量。在调强质子治疗中，由于需要考虑到射程误差，基于静态剂量云近似的假设（即假设剂量分布对误差不变）存在问题。本研究的目的是引入一种适用于光子和质子治疗的稳健性评估方法，并且与基于 PTV 的治疗计划评估一致。
材料与方法
在多情景模拟中，通过明确计算各种描述治疗过程中可能出现的误差的治疗情景下的剂量，解决了静态剂量云近似的局限性。摆位误差与 CTV-PTV 边界相同，并将三维概率密度分布的理论扩展到包括射程误差的四维，以保持 90%置信水平。情景剂量分布被简化为体素-wise 最小和最大剂量分布；第一个用于评估 CTV 覆盖率，第二个用于评估热点。根据历史光子治疗计划的 PTV 基准，对 CTV D98 和 D2 的接受标准进行校准。
结果
最坏情况下剂量的 CTV D98 和体素-wise 最小剂量与情景平均 D98 之间具有很强的相关性（R > 0.99）。体素-wise 最小剂量以 3D 方式可视化 CTV 剂量一致性和覆盖范围，与光子治疗中的 PTV 评估一致。体素-wise 最小和最大剂量的 CTV D98 和 D2 的标准与 PTV D98 和 D2 之间具有很强的相关性（R > 0.99），平均需要校正-0.9%和+2.3%。
结论
为无 PTV 的光子和质子治疗计划提供了一种实用的稳健性评估方法，并在临床上实施，与 PTV 评估一致，但没有其静态剂量云近似。
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