VMAT for Liver SBRT: Dosimetric Objectives

In the original VMAT plans, a total dose of 45 Gy in 3 fractions was prescribed for all patients with the following planning objectives: prescription dose to cover at least 95% of PTV, conformity index (CI) < 1.2, and appropriate dose sparing of the OARs. The normal tissue dose constraints used at our institution for liver SBRT in 3 fractions are presented in Table 2 [26 (link)]. The Eclipse analytical anisotropic algorithm was used for dose calculation with a grid size of 1.25 mm in the VMAT plans. Using the Eclipse planning system, inverse planning for each patient was performed with a 10 MV flattening-filter-free beam of a Varian TrueBeam accelerator equipped with a high-definition 120 MLC, and 2 full arcs (clockwise rotation from 181–179° with the collimator at 30°, and counterclockwise rotation from 179–181° with the collimator at 330°). The mean isodose line prescribed to 45 Gy was 90.6% (range, 87–92%) of the maximum dose.