Comparison of dosimetric characteristics between flattening filter‐free and flattening filter mode volumetric‐modulated arc therapy plans in rectal cancer

Objective We aimed to compare the dosimetric characteristics of 6-MV flattening filter mode (FF) and filter-free (FFF) volumetric-modulated arc therapy (VMAT) plans in preoperative radiotherapy for rectal cancer using an Edge linear accelerator. Methods Two-arc FF-VMAT FFF-VMAT were generated 15 patients with Philips Pinnacle treatment planning system (version 9.10). The homogeneity index, conformity target volume covered by 105% isodose lines, organ-at-risk dosimetry characteristics, monitor units (MUs) compared between plans. results analyzed paired t-tests. Results index plan (0.93 ± 0.01) (0.92 0.02), two groups (0.07 0.03) (0.08 0.01), differences not statistically significant (both P > 0.05). lines was significantly higher than that plan. required a unit (t = 11.49, 0.002) shorter beam-on time 5.78, 0.001) There no absolute receiving 30 Gy 40 bladder intestine colon increased 5.5% 2.1% those 7.2% 2.2%, respectively 20 left right femoral head decreased 3.7% 4.9% (P Conclusion Both met clinical requirements.