Department of Radiation Oncology, University of Kansas Medical Center, Kansas City, Kansas, USA.
Department of Radiation Oncology, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA.
J Appl Clin Med Phys. 2023 May;24(5):e13957. doi: 10.1002/acm2.13957. Epub 2023 Apr 12.
To characterize potential dose to the fetus for all modes of delivery (dynamic adaptive aperture, static adaptive aperture, and no adaptive aperture) for the Mevion S250i Proton Therapy System with HYPERSCAN and compare the findings with those of other available proton systems.
Fetal dose measurements were performed for all three modes of dose delivery on the Mevion S250i Proton therapy system with HYPERSCAN (static aperture, dynamic aperture and uncollimated). Standard treatment plans were created in RayStation for a left-sided brain lesion treated with a vertex field, a left lateral field, and a posterior field. Measurements were performed using WENDI and the RANDO with the detector placed at representative locations to mimic the growth and movement of the fetus at different gestational stages.
The fetal dose measurements varied with fetus position and the largest measured dose was 64.7 μSv per 2 Gy (RBE) fraction using the dynamic aperture. The smallest estimated fetal dose was 45.0 μSv per 2 Gy (RBE) at the base of the RANDO abdomen (47 cm from isocenter to the outer width of WENDI and 58.5 cm from the center of the WENDI detector) for the static aperture delivery. The vertex fields at all depths had larger contributions to the total dose than the other two and the dynamic aperture plans resulted in the highest dose measured for all depths.
The reported doses are lower than reported doses using a double-scattering system. This work suggests that avoiding vertex fields and using the static aperture will help minimize dose to the fetus.
为 Mevion S250i 质子治疗系统与 HYPERSCAN 联合使用的所有输送模式（动态自适应孔径、静态自适应孔径和无自适应孔径）描绘胎儿潜在剂量，并将结果与其他可用质子系统进行比较。
对 Mevion S250i 质子治疗系统与 HYPERSCAN（静态孔径、动态孔径和非准直孔径）的所有三种剂量输送模式进行胎儿剂量测量。使用 RayStation 为左侧脑部病变创建标准治疗计划，使用顶点野、左侧野和后野进行治疗。使用 WENDI 和 RANDO 进行测量，探测器放置在代表性位置以模拟胎儿在不同妊娠阶段的生长和运动。
胎儿剂量测量随胎儿位置而变化，使用动态孔径时最大测量剂量为每 2 Gy（RBE）分数 64.7 μSv。在 RANDO 腹部底部（距等中心 47 cm 到 WENDI 外宽，距 WENDI 探测器中心 58.5 cm）使用静态孔径输送时，估计胎儿剂量最小为 45.0 μSv 每 2 Gy（RBE）。所有深度的顶点野对总剂量的贡献均大于其他两个野，而动态孔径计划导致所有深度的测量剂量最高。
报告的剂量低于使用双散射系统报告的剂量。这项工作表明，避免顶点野并使用静态孔径将有助于最大限度地减少胎儿剂量。
