Abstract：Objective To evaluate the plan quality of volumetric modulated arc therapy (VMAT) in single brain metastasis compared with the stereotactic arc therapy (S_ARC). Methods 31 patients were replanned using VMAT and S_ARC technique. Prescription dose is 40 Gy delivered in 4 fractions covering at least 95% of the target volume while keeping minimum doses to the volume of normal brain tissue. The plans were assessed and compared using the conformity indexes (CI),gradient indexes (GI), the mean dose of normal brain tissue, the volumes of normal brain tissue receiving 4 Gy doses, the number of monitor unit and treatment times. A paired t test or non-parametric Wilcoxon signed rank test was performed to analyze the difference between these two plans. Results VMAT plans increased dose conformity, but not dose gradient, compared with S_ARC plans. The median dose conformity index values were 0.815, 0.818, and 0.779(P=0.000,0.000), and the median dose gradient score index values were 5.865, 5.706, and 3.133(P=0.000,0.000,0.000), in single arc, double arc VMAT plans and S_ARC plans, respectively. The mean dose of normal brain tissue was higher in VMAT plans. And the volume of the normal brain tissue receiving doses of 4 Gy in VMAT plans was significantly larger than the volume in S_ARC plans. The VMAT plans got higher MU number (P=0.000,0.000). And the mean treatment times were (2.7±0.1) min,(2.8±0.1) min, and (7.6±0.2) min in single arc, double arc VMAT plans and S_ARC plans, respectively (P=0.000,0.000). Conclusions The dosimetry of VMAT plan can meet the requirements of clinical, and is recommended in the treatment of big volume single brain metastasis or single brain metastasis in cerebellum.
Xu Yingjie,Xiao Jianping,Ma Pan et al. Dosimetry study of volumetric-modulated arc therapy for single brain metastasis[J]. Chinese Journal of Radiation Oncology, 2015, 24(3): 306-309.
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