Comparing proton treatment plans of pediatric brain tumors in two pencil beam scanning nozzles with different spot sizes
Comparing proton treatment plans of pediatric brain tumors in two pencil beam scanning nozzles with different spot sizes
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DOI：
10.1120/jacmp.v16i6.5389
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发表时间：
2015-01-01
影响因子：
2.1
通讯作者：
Lin, Liyong
中科院分区：
文献类型：
--
作者：
Kralik, John C.;Xi, Liwen;Lin, Liyong
对 22 名原发性脑肿瘤儿科患者在笔形束扫描 (PBS) 质子治疗中使用两种不同喷嘴进行治疗的目标覆盖率和危及器官保留进行了比较。使用通用喷嘴 (UN) 光束模型和原始 DN 计划目标对在我们机构使用 PBS 专用喷嘴 (DN) 连续治疗的患者进行了重新规划。患者的不同颅骨部位接受了 45 至 54 Gy 范围内的处方剂量治疗。评估的风险器官（OAR）取决于患者；分析了 15 个独特的 OAR，所有这些都在至少 10 名患者中进行了评估。使用剂量体积直方图数据比较两个喷嘴的临床靶体积（CTV）覆盖和器官保留。使用置信区间方法的统计分析表明，UN 和 DN 计划的 CTV 覆盖范围是等效的，在 +/- 5% 等效范围内。相比之下，联合国计划中几乎所有 15 个 OAR 的平均剂量和最大剂量都显着较高。所有 OAR 和患者的平均中位增量约为 1.7 Gy，其中 25%-75% 的增量为 1.0-2.3 Gy；垂体、颞叶、眼睛和耳蜗的平均增加量分别为 1.8、1.7、0.7 和 2.7 Gy。 UN 计划的 CTV 剂量分布下降速度比 DN 计划慢；因此，联合国计划中靠近 CTV 的正常组织结构所接受的剂量高于 DN 计划中的剂量。联合国计划中较高的 OAR 剂量可能是由于使用联合国光束创建的计划中的光斑轮廓较大。鉴于接受颅脑照射的儿科患者的高毒性发生率以及具有高治愈率的选定脑肿瘤类型，本研究表明较小的 DN 光束剖面更有利于减少 OAR 的剂量。
Target coverage and organ-at-risk sparing were compared for 22 pediatric patients with primary brain tumors treated using two distinct nozzles in pencil beam scanning (PBS) proton therapy. Consecutive patients treated at our institution using a PBS-dedicated nozzle (DN) were replanned using a universal nozzle (UN) beam model and the original DN plan objectives. Various cranial sites were treated among the patients to prescription doses ranging from 45 to 54 Gy. Organs at risk (OARs) evaluated were patient-dependent; 15 unique OARs were analyzed, all of which were assessed in at least 10 patients. Clinical target volume (CTV) coverage and organ sparing were compared for the two nozzles using dose-volume histogram data. Statistical analysis using a confidence-interval approach demonstrates that CTV coverage is equivalent for UN and DN plans within +/- 5% equivalence bounds. In contrast, average mean and maximum doses are significantly higher for nearly all 15 OARs in the UN plans. The average median increase over all OARs and patients is approximately 1.7 Gy, with an increase in the 25%-75% of 1.0-2.3 Gy; the median increase to the pituitary gland, temporal lobes, eyes and cochleas are 1.8, 1.7, 0.7, and 2.7 Gy, respectively. The CTV dose distributions fall off slower for UN than for the DN plans; hence, normal tissue structures in close proximity to CTVs receive higher doses in UN plans than in DN plans. The higher OAR doses in the UN plans are likely due to the larger spot profile in plans created with UN beams. In light of the high rates of toxicities in pediatric patients receiving cranial irradiation and in light of selected brain tumor types having high cure rates, this study suggests the smaller DN beam profile is preferable for the advantage of reducing dose to OARs.