Reducing the sensitivity of IMPT treatment plans to setup errors and range uncertainties via probabilistic treatment planning
Reducing the sensitivity of IMPT treatment plans to setup errors and range uncertainties via probabilistic treatment planning
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DOI：
10.1118/1.3021139
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发表时间：
2009-01-01
期刊：
影响因子：
3.8
通讯作者：
Soukup, Martin
中科院分区：
文献类型：
--
作者：
Unkelbach, Jan;Bortfeld, Thomas;Soukup, Martin
针对强度调制质子治疗（IMPT）优化的治疗计划可能对设置误差和范围不确定性非常敏感。如果在治疗计划期间不考虑这些误差，则与计划的剂量分布相比，在患者中实现的剂量分布可能严重退化。作者采用概率方法将不确定性直接纳入调强治疗计划的优化中。按照这种方法，剂量分布取决于一组随机变量，其参数化不确定性，用于优化治疗计划的目标函数也是如此。对目标函数的期望值进行了优化。他们调查IMPT治疗计划的范围不确定性和设置错误。他们表明，将这些不确定性纳入优化产生质的不同的治疗计划相比，传统的计划，不考虑不确定性。IMPT计划的灵敏度取决于各个射束方向的剂量贡献。粗略地说，在射束方向上的陡峭剂量梯度使得治疗计划对范围误差敏感。陡峭的横向剂量梯度使计划对设置误差敏感。通过在不同射束方向之间重新分配剂量来获得更稳健的治疗计划。这可以通过概率方法来实现。相比之下，广泛应用于光子治疗的安全裕度方法在IMPT中失败，并且既不适合处理范围变化也不适合处理设置错误。(C)2009年美国医学物理学家协会。[DOI：10.1118/1.3021139]
Treatment plans optimized for intensity modulated proton therapy (IMPT) may be very sensitive to setup errors and range uncertainties. If these errors are not accounted for during treatment planning, the dose distribution realized in the patient may by strongly degraded compared to the planned dose distribution. The authors implemented the probabilistic approach to incorporate uncertainties directly into the optimization of an intensity modulated treatment plan. Following this approach, the dose distribution depends on a set of random variables which parameterize the uncertainty, as does the objective function used to optimize the treatment plan. The authors optimize the expected value of the objective function. They investigate IMPT treatment planning regarding range uncertainties and setup errors. They demonstrate that incorporating these uncertainties into the optimization yields qualitatively different treatment plans compared to conventional plans which do not account for uncertainty. The sensitivity of an IMPT plan depends on the dose contributions of individual beam directions. Roughly speaking, steep dose gradients in beam direction make treatment plans sensitive to range errors. Steep lateral dose gradients make plans sensitive to setup errors. More robust treatment plans are obtained by redistributing dose among different beam directions. This can be achieved by the probabilistic approach. In contrast, the safety margin approach as widely applied in photon therapy fails in IMPT and is neither suitable for handling range variations nor setup errors. (C) 2009 American Association of Physicists in Medicine. [DOI: 10.1118/1.3021139]