Dosimetric comparison of different multileaf collimators in volumetric modulated arc therapy for malignant pleural mesothelioma

Abstract

Abstract Objective The aiom of the study was to compare the impacts of two types of multileaf collimators (MLC) [standard MLC with a width of 10 mm (sMLC) and micro-MLC with a width of 5 mm (mMLC)] on volumetric modulated arc therapy (VMAT) planning for malignant pleural mesothelioma. Methods VMAT for ten patients with inoperable malignant pleural mesotheliomas was retrospectively planned with the sMLC and mMLC. Histogram-based dose-volume parameters of the planning target volume (PTV) [conformity index (CI) and homogeneous index (HI)] and organs-at-risk were compared for VMAT plans with sMLC (sMLC-VMAT) and mMLC (mMLC-VMAT). Results The mMLC-VMAT plans were more efficient (average delivery time: 2.67±1.49 min) than the sMLC-VMAT plans (average delivery time: 4.21 ± 2.03 min; P < 0.05). Moreover, compared to the sMLC plans, the mMLC plans demonstrated advantages in the dose coverage of the PTV (CI 0.75 ± 0.08 vs 0.73 ± 0.09; HI 1.09 ± 0.02 vs 1.10 ± 0.02), although the difference was not statistically significant (P > 0.05). In addition, significant dose sparing in the fraction of the ipsilateral lung volume receiving > 20 Gy (V20; 54.72 ± 27.08 vs 58.52 ± 29.30) and > 30 Gy (V30; 42.74 ± 27.86 vs 46.86 ± 31.49) radiation, respectively, was observed for the mMLC plans (P < 0.05). Conclusion Comparing sMLC-VMAT and mMLC-VMAT not only demonstrated the higher efficiency and better optimal target coverage of mMLC-VMAT, but also considerably improved the dose sparing of the ipsilateral lung in the VMAT plans for malignant pleural mesothelioma.