Abstract
PURPOSE: The aim of this study was to dosimetrically compare volumetric-modulated arc therapy (VMAT) with intensity-modulated radiotherapy (IMRT) techniques using either 6- or 10-MV photon beam energies in lung stereotactic body radiation therapy (SBRT) plans. METHODS: Thirty patients with primary or metastatic lung tumors eligible for SBRT were randomly selected. VMAT and IMRT treatment plans using either 6- or 10-MV photon energies were generated through automatic SBRT planning software in the RayStation treatment planning system. RESULTS: For planning target volume, there was no difference in D(95%) for all plans, whereas D(2%) and D(50%) were significantly increased by 5.22%-5.98% and 2.47%-2.59%, respectively, using VMAT(6/10-MV) plans compared to IMRT(6/10-MV) plans. When comparing the D(max) of organs at risk (OARs), VMAT(6/10-MV) was 18.32%-47.95% lower than IMRT(6/10-MV) for almost all OARs. VMAT(6/10-MV) obviously decreased D(mean) , V(5Gy) , V(10Gy) , and V(20Gy) of whole lung by 9.68%-20.92% than IMRT(6/10-MV) . Similar results were found when comparing VMAT(6-MV) with IMRT(10-MV) or VMAT(10-MV) with IMRT(6-MV) . The differences in the D(2%) , heterogeneity index, and conformity index between 6- and 10-MV plans are not statistically significant. Plans using 6-MV performed 4.68%-8.91% lower levels of D(max) of spinal cord, esophagus, great vessels, and trachea and proximal bronchial tree than those using 10-MV plans. Similarly, D(mean) , V(5Gy) , V(10Gy) , and V(20Gy) of whole lung were also reduced by 2.79%-5.25% using 6-MV. For dose fall-off analysis, the D(2cm) and R(50%) of VMAT(6/10-MV) were lower than those of IMRT(6/10-MV) . Dose fall-off curve based on 10 rings was steeper for VMAT plans than IMRT plans regardless of the energy used. CONCLUSIONS: For lung SBRT plans, VMAT-based plans significantly reduced OARs dose and steepened dose fall-off curves compared to IMRT-based plans. A 6-MV energy level was a better choice than 10-MV for lung SBRT. In addition, the dose differences between different techniques were more obvious than those between different energy levels.