旋转屏蔽近距离放射治疗中快速射束角选择。
Rapid emission angle selection for rotating-shield brachytherapy.
机构信息
Department of Electrical and Computer Engineering, University of Iowa, 4016 Seamans Center, Iowa City, Iowa 52242, USA.
出版信息
Med Phys. 2013 May;40(5):051720. doi: 10.1118/1.4802750.
PURPOSE
The authors present a rapid emission angle selection (REAS) method that enables the efficient selection of the azimuthal shield angle for rotating shield brachytherapy (RSBT). The REAS method produces a Pareto curve from which a potential RSBT user can select a treatment plan that balances the tradeoff between delivery time and tumor dose conformity.
METHODS
Two cervical cancer patients were considered as test cases for the REAS method. The RSBT source considered was a Xoft Axxent(TM) electronic brachytherapy source, partially shielded with 0.5 mm of tungsten, which traveled inside a tandem intrauterine applicator. Three anchor RSBT plans were generated for each case using dose-volume optimization, with azimuthal shield emission angles of 90°, 180°, and 270°. The REAS method converts the anchor plans to treatment plans for all possible emission angles by combining neighboring beamlets to form beamlets for larger emission angles. Treatment plans based on exhaustive dose-volume optimization (ERVO) and exhaustive surface optimization (ERSO) were also generated for both cases. Uniform dwell-time scaling was applied to all plans such that that high-risk clinical target volume D90 was maximized without violating the D2cc tolerances of the rectum, bladder, and sigmoid colon.
RESULTS
By choosing three azimuthal emission angles out of 32 potential angles, the REAS method performs about 10 times faster than the ERVO method. By setting D90 to 85-100 Gy10, the delivery times used by REAS generated plans are 21.0% and 19.5% less than exhaustive surface optimized plans used by the two clinical cases. By setting the delivery time budget to 5-25 and 10-30 min∕fx, respectively, for two the cases, the D90 contributions for REAS are improved by 5.8% and 5.1% compared to the ERSO plans. The ranges used in this comparison were selected in order to keep both D90 and the delivery time within acceptable limits.
CONCLUSIONS
The REAS method enables efficient RSBT treatment planning and delivery and provides treatment plans with comparable quality to those generated by exhaustive replanning with dose-volume optimization.
目的
作者提出了一种快速发射角选择（REAS）方法，该方法可用于高效选择旋转屏蔽近距离治疗（RSBT）的方位屏蔽角度。REAS 方法从帕累托曲线中生成一个治疗计划，潜在的 RSBT 用户可以在其中平衡交付时间和肿瘤剂量一致性之间的权衡。
方法
对两名宫颈癌患者进行了 REAS 方法的测试。考虑的 RSBT 源是部分屏蔽有 0.5 毫米钨的 Xoft Axxent（TM）电子近距离治疗源，该源在宫内应用器内运行。对每个病例使用剂量体积优化生成三个锚定 RSBT 计划，发射角分别为 90°、180°和 270°。REAS 方法通过将相邻的射束组合形成较大发射角的射束，将锚定计划转换为所有可能发射角的治疗计划。还为两种情况生成了基于详尽剂量体积优化（ERVO）和详尽表面优化（ERSO）的治疗计划。对所有计划都应用了均匀驻留时间缩放，使得高风险临床靶区 D90 最大化，同时不违反直肠、膀胱和乙状结肠的 D2cc 耐受度。
结果
通过从 32 个潜在角度中选择三个方位发射角度，REAS 方法的速度比 ERVO 方法快约 10 倍。通过将 D90 设置为 85-100 Gy10，REAS 生成计划的交付时间比两个临床病例中使用的详尽表面优化计划分别减少了 21.0%和 19.5%。对于两个病例，分别将交付时间预算设置为 5-25 和 10-30 min∕fx，与 ERSO 计划相比，REAS 的 D90 贡献分别提高了 5.8%和 5.1%。进行此比较所使用的范围是为了保持 D90 和交付时间都在可接受的范围内。
结论
REAS 方法能够实现高效的 RSBT 治疗计划和交付，并提供与使用剂量体积优化进行详尽重新规划生成的治疗计划质量相当的治疗计划。
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