伽玛刀放射外科治疗计划与实施中“套中套”优化的临床评估
Clinical Evaluation of Shot-Within-Shot Optimization for Gamma Knife Radiosurgery Planning and Delivery.
作者信息
Johnson Perry B, Monterroso Maria I, Yang Fei, Bossart Elizabeth, Keyvanloo Amir, Mellon Eric A
机构信息
Radiation Oncology/Biomedical Engineering, University of Miami, Miami, Florida, USA.
Radiation Oncology, University of Miami, Miami, Florida, USA.
出版信息
World Neurosurg. 2019 Mar;123:e218-e227. doi: 10.1016/j.wneu.2018.11.140. Epub 2018 Nov 24.
OBJECTIVE
Shot-within-shot (SWS) optimization is a new planning technique that relies on various combinations of shot weighting and prescription isodose line (IDL) to reduce beam-on time. The method differs from other planning techniques that incorporate mixed collimation, multiple stereotactic coordinates, and traditionally low prescription IDLs (<60%). In this work, we evaluate the percentage of brain metastasis for which the method can be applied, the magnitude of the resultant time savings, and the possible tradeoffs in plan quality.
METHODS
A retrospective analysis was performed on 75 patients treated for 241 metastatic lesions in the brain. For each lesion, the original planning metrics related to target coverage, conformity, gradient, and beam-on time were recorded. A subset of lesions were selected for replanning using the SWS technique based on size, shape, and proximity to critical structures. Two replans were done, a reference plan was prescribed at the 50% IDL, and an optimized plan was prescribed at an IDL typically >50%. Planning metrics were then compared among the original plan and the 2 replans.
RESULTS
More than a third (39%) of the brain metastases were eligible for the SWS technique. For these lesions, the differences between the original plan and reference SWS plan were as follows: ΔV < 0.5 cc in 93% of cases, ΔV < 0.5 cc in 100% of cases, Δselectivity < 0.1 in 79% of cases. Negligible differences were seen between the 2 replans in terms of Δselectivity and ΔV; ΔGI < 5% in 99% of cases. After optimization, beam-on time was reduced by 25%-30% in approximately 40%-50% of eligible lesions when compared with the reference SWS plan (ΔT = 42%). In comparison with the original plan, beam-on time was reduced even further, ΔT > 50% in 20% of cases (ΔT = 70%).
CONCLUSIONS
This work demonstrates clinically that optimization using the shot-within-shot technique can reduce beam-on time without degrading treatment plan quality.
目的
逐次照射（SWS）优化是一种新的治疗计划技术，它依靠照射权重和处方等剂量线（IDL）的各种组合来减少治疗时间。该方法不同于其他采用混合准直、多个立体定向坐标以及传统低处方IDL（<60%）的治疗计划技术。在本研究中，我们评估了可应用该方法的脑转移瘤的比例、由此节省的时间量以及计划质量方面可能的权衡。
方法
对75例接受治疗的241个脑转移瘤患者进行回顾性分析。对于每个病灶，记录与靶区覆盖、适形度、梯度和治疗时间相关的原始计划指标。根据大小、形状和与关键结构的接近程度，选择一部分病灶使用SWS技术重新规划。进行了两次重新规划，一个参考计划在50% IDL处处方，一个优化计划在通常>50%的IDL处处方。然后比较原始计划和两次重新规划之间的计划指标。
结果
超过三分之一（39%）的脑转移瘤适合SWS技术。对于这些病灶，原始计划与参考SWS计划之间的差异如下：93%的病例中ΔV<0.5 cc，100%的病例中ΔV<0.5 cc，79%的病例中Δ选择性<0.1。两次重新规划在Δ选择性和ΔV方面差异可忽略不计；99%的病例中ΔGI<5%。优化后，与参考SWS计划相比，约40%-50%符合条件的病灶的治疗时间减少了25%-30%（ΔT = 42%）。与原始计划相比疗程时间进一步减少，20%的病例中ΔT>50%（ΔT = 70%）。
结论
这项研究在临床上证明，使用逐次照射技术进行优化可以减少治疗时间，而不会降低治疗计划质量。
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