Center for Proton Therapy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
Phys Med Biol. 2011 Jul 21;56(14):4399-413. doi: 10.1088/0031-9155/56/14/011. Epub 2011 Jun 27.
In radiation therapy, a plan is robust if the calculated and the delivered dose are in agreement, even in the case of different uncertainties. The current practice is to use safety margins, expanding the clinical target volume sufficiently enough to account for treatment uncertainties. This, however, might not be ideal for proton therapy and in particular when using intensity modulated proton therapy (IMPT) plans as degradation in the dose conformity could also be found in the middle of the target resulting from misalignments of highly in-field dose gradients. Single field uniform dose (SFUD) and IMPT plans have been calculated for different anatomical sites and the need for margins has been assessed by analyzing plan robustness to set-up and range uncertainties. We found that the use of safety margins is a good way to improve plan robustness for SFUD and IMPT plans with low in-field dose gradients but not necessarily for highly modulated IMPT plans for which only a marginal improvement in plan robustness could be detected through the definition of a planning target volume.
在放射治疗中，如果计算出的剂量与实际测量的剂量相符，那么计划就是稳健的，即使存在不同的不确定性。目前的做法是使用安全裕度，将临床靶区充分扩大，以考虑到治疗的不确定性。然而，对于质子治疗，尤其是使用强度调制质子治疗（IMPT）计划时，这种方法可能并不理想，因为在靶区中间也可能会发现剂量适形度的下降，这是由于高强度场内剂量梯度的不匹配造成的。已经为不同的解剖部位计算了单野均匀剂量（SFUD）和 IMPT 计划，并通过分析对设置和范围不确定性的计划稳健性来评估边缘的必要性。我们发现，使用安全裕度是提高 SFUD 和低场内剂量梯度 IMPT 计划稳健性的一种好方法，但对于高度调制的 IMPT 计划则不一定，因为通过定义计划靶区，只能检测到计划稳健性的微小改善。
