与 VMAT 相比，使用 CAVMAT 的单等中心 SRS 可提高对摆位和治疗交付不确定性的稳健性。

Single isocenter SRS using CAVMAT offers improved robustness to commissioning and treatment delivery uncertainty compared to VMAT.

机构信息

Medical Physics Graduate Program, Duke University, Durham, North Carolina, USA.

Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA.

出版信息

J Appl Clin Med Phys. 2021 Jul;22(7):36-43. doi: 10.1002/acm2.13248. Epub 2021 Jun 24.

DOI:10.1002/acm2.13248

PMID:34165217

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC8292691/

Abstract

PURPOSE

In this study, we evaluate and compare single isocenter multiple target VMAT (SIMT) and Conformal Arc Informed VMAT (CAVMAT) radiosurgery's sensitivity to uncertainties in dosimetric leaf gap (DLG) and treatment delivery. CAVMAT is a novel planning technique that uses multiple target conformal arcs as the starting point for limited inverse VMAT optimization.

METHODS

All VMAT and CAVMAT plans were recalculated with DLG values of 0.4, 0.8, and 1.2 mm. DLG effect on V [cc], V [cc], and V [cc], and target dose was evaluated. Plans were delivered to a Delta (ScandiDos, Madison, WI) phantom and gamma analysis performed with varying criteria. Log file analysis was performed to evaluate MLC positional error. Sixteen targets were delivered to a SRS MapCHECK (Sun Nuclear Corp., Melbourne, FL) to evaluate VMAT and CAVMAT's dose difference (DD) as a function of DLG.

RESULTS

VMAT's average maximum and minimum target dose sensitivity to DLG was 9.08 ±3.50%/mm and 9.50 ± 3.30%/mm, compared to 3.20 ± 1.60%/mm and 4.72 ± 1.60%/mm for CAVMAT. For VMAT, V [cc], V [cc], and V [cc] sensitivity was 35.83 ± 9.50%/mm, 34.12 ± 6.60%/mm, and 39.23 ± 8.40%/mm. In comparison, CAVMAT's sensitivity was 23.19 ± 4.50%/mm, 22.45 ± 4.40%/mm, and 24.88 ± 4.90%/mm, respectively. Upon delivery to the Delta , CAVMAT offered superior dose agreement compared to VMAT. For a 1%/1 mm gamma analysis, VMAT and CAVMAT had a passing rate of 94.53 ± 4.40% and 99.28 ± 1.70%, respectively. CAVMAT was more robust to DLG variation, with the SRS MapCHECK plans yielding an absolute average DD sensitivity of 2.99 ± 1.30%/mm compared to 5.07 ± 1.10%/mm for VMAT. Log files demonstrated minimal differences in MLC positional error for both techniques.

CONCLUSIONS

CAVMAT remains robust to delivery uncertainties while offering a target dose sensitivity to DLG less than half that of VMAT, and 65% of that of VMAT for V [cc], V [cc], and V [cc]. The superior dose agreement and reduced sensitivity of CAVMAT to DLG uncertainties indicate promise as a robust alternative to VMAT for SIMT SRS.

摘要

目的

在这项研究中，我们评估和比较了单等中心多靶容积旋转调强（SIMT）和适形弧信息容积旋转调强（CAVMAT）放射外科治疗在剂量学叶片间隙（DLG）和治疗输送方面不确定性的敏感性。CAVMAT 是一种新的规划技术，它使用多个靶区适形弧作为有限的逆向调强优化的起点。

方法

所有的 VMAT 和 CAVMAT 计划都在 DLG 值为 0.4、0.8 和 1.2mm 时重新计算。评估了 DLG 对 V[cc]、V[cc]和 V[cc]的影响以及靶区剂量。计划被输送到一个 Delta（ScandiDos，麦迪逊，WI）体模，并使用不同的标准进行伽马分析。进行了日志文件分析，以评估 MLC 位置误差。将 16 个靶区输送到 SRS MapCHECK（Sun Nuclear Corp.，墨尔本，FL），以评估 VMAT 和 CAVMAT 的剂量差异（DD）作为 DLG 的函数。

结果

VMAT 对 DLG 的最大和最小靶区剂量的平均敏感性分别为 9.08±3.50%/mm 和 9.50±3.30%/mm，而 CAVMAT 分别为 3.20±1.60%/mm 和 4.72±1.60%/mm。对于 VMAT，V[cc]、V[cc]和 V[cc]的敏感性分别为 35.83±9.50%/mm、34.12±6.60%/mm 和 39.23±8.40%/mm。相比之下，CAVMAT 的敏感性分别为 23.19±4.50%/mm、22.45±4.40%/mm 和 24.88±4.90%/mm。在输送到 Delta 体模后，CAVMAT 提供了比 VMAT 更好的剂量一致性。对于 1%/1mm 的伽马分析，VMAT 和 CAVMAT 的通过率分别为 94.53±4.40%和 99.28±1.70%。CAVMAT 对 DLG 变化更稳健，SRS MapCHECK 计划的绝对平均 DD 敏感性为 2.99±1.30%/mm，而 VMAT 为 5.07±1.10%/mm。日志文件显示两种技术的 MLC 位置误差基本相同。

结论

CAVMAT 在治疗输送不确定性方面仍然具有稳健性，而其靶区剂量对 DLG 的敏感性仅为 VMAT 的一半，对 V[cc]、V[cc]和 V[cc]的敏感性为 VMAT 的 65%。CAVMAT 优越的剂量一致性和对 DLG 不确定性的低敏感性表明，它作为 SIMT SRS 的一种稳健替代方案具有很大的潜力。