Personalized selection of unequal sub-arc collimator angles in VMAT for multiple brain metastases

IF 1.6 3区工程技术 Q3 CHEMISTRY, INORGANIC & NUCLEAR Applied Radiation and Isotopes Pub Date : 2024-09-11 DOI:10.1016/j.apradiso.2024.111513

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Abstract

Purpose

Investigating the effects of unequal sub-arc personalized collimator angle selection on the quality of Volumetric Modulated Arc Therapy (VMAT) plans for treating multiple brain metastases.

Methods

This study included 21 patients, each with 2–4 target volumes of multiple brain metastases. Two stereotactic radiotherapy (SRT) approaches were utilized: sub-arc collimator VMAT (SAC-VMAT) and fixed collimator VMAT (FC-VMAT). In the SAC-VMAT group, multi-leaf collimators (MLC) shaped the target area, dividing the full arc into four unequal sub-arcs under the beam's eye view (BEV). Each sub-arc had an appropriate collimator angle selected to mitigate ‘island blocking problems'. Conversely, the FC-VMAT group used a fixed collimator angle of 15° or 345°. A comparative analysis of the dosimetric parameters of the target volumes and normal tissues, along with the monitor units (MU), was conducted between the two groups.

Results

The mean dose and dose-volume to normal brain tissue (2–26 Gy, with a step of 2 Gy) were significantly lower in the SAC-VMAT group (P < 0.01). There was no statistical difference between the two groups in dose to the target volumes, conformity index (CI), homogeneity index (HI), and other normal tissues (P > 0.05). Compared with the FA-VMAT group, the SAC-VMAT group significantly reduced the gradient index (GI) (4.5 ± 0.59 vs 5.2 ± 0.75, P < 0.001) and MU (1774.33 ± 181.77 vs 2001.0 ± 344.86, P < 0.001). Notably, with an increase in the number of PTV, the SAC-VMAT group demonstrated more significant improvements in the dose-volume of normal brain tissue, GI, and MU.

Conclusions

In this study, personalized selection of the unequal sub-arc collimator angle ensured the prescribed dose to the PTV, CI, and HI, while significantly reducing the GI, MU, and the dose to normal brain tissue in the VMAT plan for multi-target brain metastases in the cohort of cases with 2–4 target volumes. Particularly as the number of targets increase, the advantages of this method become more pronounced.

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在治疗多发性脑转移瘤的 VMAT 中个性化选择不等边弧下准直器角度

目的研究不等弧下个性化准直器角度选择对治疗多发性脑转移瘤的体积调制弧治疗（VMAT）计划质量的影响。研究采用了两种立体定向放射治疗（SRT）方法：亚弧准直器VMAT（SAC-VMAT）和固定准直器VMAT（FC-VMAT）。在 SAC-VMAT 组中，多叶准直器（MLC）对靶区进行塑形，在光束眼视图（BEV）下将整个弧线分成四个不相等的子弧。每个子弧线都选择了适当的准直器角度，以减轻 "孤岛阻塞问题"。相反，FC-VMAT 组则使用 15° 或 345° 的固定准直器角度。结果SAC-VMAT组正常脑组织的平均剂量和剂量体积（2-26 Gy，步长为2 Gy）显著低于FC-VMAT组（P <0.01）。两组在靶体积剂量、一致性指数（CI）、均匀性指数（HI）和其他正常组织方面没有统计学差异（P >0.05）。与 FA-VMAT 组相比，SAC-VMAT 组明显降低了梯度指数（GI）（4.5 ± 0.59 vs 5.2 ± 0.75，P < 0.001）和 MU（1774.33 ± 181.77 vs 2001.0 ± 344.86，P < 0.001）。结论在这项研究中，个性化选择不等边弧下准直器角度确保了 PTV、CI 和 HI 的规定剂量，同时显著降低了 GI、MU 和正常脑组织的剂量。特别是随着靶点数量的增加，这种方法的优势更加明显。

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来源期刊

Applied Radiation and Isotopes 工程技术-核科学技术

CiteScore

3.00

自引率

12.50%

发文量

406

审稿时长

13.5 months

期刊介绍： Applied Radiation and Isotopes provides a high quality medium for the publication of substantial, original and scientific and technological papers on the development and peaceful application of nuclear, radiation and radionuclide techniques in chemistry, physics, biochemistry, biology, medicine, security, engineering and in the earth, planetary and environmental sciences, all including dosimetry. Nuclear techniques are defined in the broadest sense and both experimental and theoretical papers are welcome. They include the development and use of α- and β-particles, X-rays and γ-rays, neutrons and other nuclear particles and radiations from all sources, including radionuclides, synchrotron sources, cyclotrons and reactors and from the natural environment. The journal aims to publish papers with significance to an international audience, containing substantial novelty and scientific impact. The Editors reserve the rights to reject, with or without external review, papers that do not meet these criteria. Papers dealing with radiation processing, i.e., where radiation is used to bring about a biological, chemical or physical change in a material, should be directed to our sister journal Radiation Physics and Chemistry.