Yang Qiangxing, Moyers Michael F, Shen Zhuangming
Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai 201315, China.
Shanghai Key Laboratory of Radiation Oncology, Shanghai 201315, China.
Cancers (Basel). 2025 Sep 6;17(17):2927. doi: 10.3390/cancers17172927.
: Multi-scenario calculational methods have been used to evaluate proton teletherapy plan robustness but few studies have been performed to determine the accuracy of these calculational methods. This study evaluates a multi-scenario method by comparing calculations to measurements made in phantoms that simulate the effects of possible uncertainties. : Plans were made using four phantoms in which the delivered dose was highly sensitive to positional and penetration uncertainties. The effects of alignment and penetration uncertainties on the dose distributions of each of those phantoms were simulated by performing calculations using nine different uncertainty scenarios and comparing the calculations to measurements with induced physical alignment displacements. Measured dose distributions were obtained by exposing films placed inside the phantoms and extracting multiple linear profiles. The maximum and minimum doses obtained for each of the calculational scenarios were compared with the measured dose profiles. In addition, comparisons of DVHs for nominal and uncertainty scenarios were performed. : The results showed that, under the influence of uncertainties, the minimum dose for the four phantoms decreased by more than 20 Gy, the V coverage fluctuated by more than 10%, but the maximum dose parameter changed by less than 5 Gy. This was expected, as no margins for uncertainties were applied around the targets. The envelope bounded by the maximum and minimum possible calculated doses contained most of the measurements, although the shapes of the dose profiles displayed some mismatches for wedge and head phantoms. There were a few points where the measured maximum dose for bone and lung slab phantom cases was slightly higher than the maximum dose calculated from the nine scenarios. : This study demonstrates that a nine-scenario method can adequately evaluate the robustness of simple mono-directional plans containing heterogeneities.
多场景计算方法已被用于评估质子适形放疗计划的稳健性，但很少有研究来确定这些计算方法的准确性。本研究通过将计算结果与在模拟可能不确定性影响的体模中进行的测量结果进行比较，对一种多场景方法进行了评估。：使用四个体模制定计划，其中所给予的剂量对位置和穿透不确定性高度敏感。通过使用九种不同的不确定性场景进行计算，并将计算结果与具有诱导物理对准位移的测量结果进行比较，模拟了对准和穿透不确定性对每个体模剂量分布的影响。通过曝光放置在体模内的胶片并提取多个线性轮廓来获得测量的剂量分布。将每个计算场景获得的最大和最小剂量与测量的剂量轮廓进行比较。此外，还对标称和不确定性场景的剂量体积直方图进行了比较。：结果表明，在不确定性的影响下，四个体模的最小剂量降低了超过20 Gy，V覆盖波动超过10%，但最大剂量参数变化小于5 Gy。这是预期的，因为在靶区周围未应用不确定性余量。尽管对于楔形和头部体模，剂量轮廓的形状存在一些不匹配，但由最大和最小可能计算剂量界定的包络包含了大部分测量值。在一些点上，骨和肺平板体模病例的测量最大剂量略高于从九个场景计算出的最大剂量。：本研究表明，九场景方法可以充分评估包含不均匀性的简单单向计划的稳健性。
