Predicting objective function weights from patient anatomy in prostate IMRT treatment planning
Predicting objective function weights from patient anatomy in prostate IMRT treatment planning
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DOI：
10.1118/1.4828841
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发表时间：
2013-12-01
期刊：
影响因子：
3.8
通讯作者：
Sharpe, Michael B.
中科院分区：
文献类型：
--
作者：
Lee, Taewoo;Hammad, Muhannad;Sharpe, Michael B.
目的：调强放射治疗 (IMRT) 治疗计划通常通过加权求和将多个标准合并为一个目标函数。作者提出了一种统计模型，可以根据患者解剖结构预测前列腺 IMRT 治疗计划的目标函数权重。这项研究为几何驱动的体重确定提供了概念证明。方法：使用先前开发的逆优化方法 (IOM)，根据 24 名患者的历史治疗计划（即剂量分布）生成最佳目标函数权重。每个股骨头的 IOM 重量约为 1%，而患者之间的膀胱和直肠重量差异很大。使用直肠和膀胱的重叠体积与扩张 1 厘米时的计划目标体积的比率作为自变量，开发了回归模型来预测患者的直肠重量。股骨头重量固定为 1%，膀胱重量计算为 1 减去直肠和股骨头重量。该模型使用留一法交叉验证进行验证。将使用预测权重通过逆向规划生成的目标值和剂量分布与使用原始 IOM 权重以及所有患者的 IOM 权重平均值生成的目标值和剂量分布进行比较。结果：使用 l(2) 距离，IOM 权重向量与预测权重向量的距离平均比与平均权重向量的距离近六倍。同样，通过预测权重实现的膀胱和直肠目标值与通过 IOM 权重实现的目标值更相似。根据单边符号检验，预测体重和平均体重之间的客观价值表现差异具有统计显着性。对于所有患者，预测体重和 IOM 体重生成的剂量分布之间的直肠 V54.3 Gy、直肠 V70.0 Gy、膀胱 V54.3 Gy 和膀胱 V70.0 Gy 值的差异小于 5 个百分点。同样，除一名患者外，所有患者的股骨头 V54.3 Gy 值在两种剂量分布之间的差异均小于 5 个百分点。 结论：这项研究证明了患者解剖结构可用于预测治疗计划的适当目标函数权重的概念证明。从长远来看，这种几何驱动的权重可以作为迭代治疗计划设计的起点，或者可以提供有关要探索的帕累托曲面的临床最相关区域的信息。 (C) 2013 年美国医学物理学家协会。
Purpose: Intensity-modulated radiation therapy (IMRT) treatment planning typically combines multiple criteria into a single objective function by taking a weighted sum. The authors propose a statistical model that predicts objective function weights from patient anatomy for prostate IMRT treatment planning. This study provides a proof of concept for geometry-driven weight determination.Methods: A previously developed inverse optimization method (IOM) was used to generate optimal objective function weights for 24 patients using their historical treatment plans (i.e., dose distributions). These IOM weights were around 1% for each of the femoral heads, while bladder and rectum weights varied greatly between patients. A regression model was developed to predict a patient's rectum weight using the ratio of the overlap volume of the rectum and bladder with the planning target volume at a 1 cm expansion as the independent variable. The femoral head weights were fixed to 1% each and the bladder weight was calculated as one minus the rectum and femoral head weights. The model was validated using leave-one-out cross validation. Objective values and dose distributions generated through inverse planning using the predicted weights were compared to those generated using the original IOM weights, as well as an average of the IOM weights across all patients.Results: The IOM weight vectors were on average six times closer to the predicted weight vectors than to the average weight vector, using l(2) distance. Likewise, the bladder and rectum objective values achieved by the predicted weights were more similar to the objective values achieved by the IOM weights. The difference in objective value performance between the predicted and average weights was statistically significant according to a one-sided sign test. For all patients, the difference in rectum V54.3 Gy, rectum V70.0 Gy, bladder V54.3 Gy, and bladder V70.0 Gy values between the dose distributions generated by the predicted weights and IOM weights was less than 5 percentage points. Similarly, the difference in femoral head V54.3 Gy values between the two dose distributions was less than 5 percentage points for all but one patient.Conclusions: This study demonstrates a proof of concept that patient anatomy can be used to predict appropriate objective function weights for treatment planning. In the long term, such geometry-driven weights may serve as a starting point for iterative treatment plan design or may provide information about the most clinically relevant region of the Pareto surface to explore. (C) 2013 American Association of Physicists in Medicine.