Dosimetric comparison of stereotactic body radiation therapy plans for spine metastasis using flattening filter free and flattening filter modes

Abstract

Objective To compare the dosimetric difference of stereotactic body radiation therapy (SBRT) plans for spine metastasis using 6 MV X-ray flattening filter free (FFF) and flattening filter (FF) modes. Methods A total of nine previously treated patients with a total of twelve spine metastasis were retrospectively included and replanned using FFF-SBRT and FF-SBRT, respectively. The dose-volume histograms (DVH), target conformity index (CI), monitor unites (MUs) and treatment time of target volume, organs at risk and normal tissues were compared between the plans. Results Both FFF-SBRT and FF-SBRT met the clinical objectives. Dose distribution of target volume, organs at risk and normal tissues were similar. MUs of the FFF-SBRT were significantly higher than that of FF-SBRT (t=-5.20, P<0.01), while the treatment time was almost half of the latter (t=17.27, P<0.01). Conclusions Two plan modes are both clinically acceptable. FFF-SBRT plans are delivered in less time and with better efficiency. Key words: Spine metastasis; Stereotactic body radiation therapy; Flattening filter free; Dosimetry