The Dosimetric Comparison of Different SBRT Techniques for Treatment of Liver Cancer Using Flattened and Flattening Filter Free Beam

Introduction:To compare the three-dimensional conformal radiotherapy (۳DCRT), dynamic conformal arc therapy (DCA), and volumetric modulated arc therapy (VMAT) in stereotactic body radiation therapy (SBRT) of liver cases using ۶MV and ۱۰ MV flattened beam (FB) and flattening filter-free beam (FFFB).Material and Methods:Twenty liver SBRT patients were selected. The dose prescription was ۴۰ Gy delivered in ۵ fractions. ۳DCRT, DCA and VMAT planning was performed using ۶ MV FB, ۶ MV FFFB, ۱۰ MV FB and ۱۰ MV FFFB. Planning target volume (PTV) coverage, organs at risk (OARs) doses, monitor units (MU), and beam on time (BOT) were noted.Results:VMAT plan produces better PTV coverage in the D۹۸% and D۹۵% region. ۶ MV and ۱۰ MV VMAT FB and FFFB reduced the D۷۰۰cc, V۱۰Gy, and Dmean of the liver minus gross tumor volume region compared to ۳DCRT and DCA plans. FFFB in combination with VMAT producing highly conformal plan (Conformit index=۱.۱۹), better conformity number (CN=۰.۸۵), and lowering Paddick gradient index (GIpad=۳.۲۹) in comparison to ۳DCRT and DCA. The FFFB needs higher monitor units to achieve the plan in all the techniques. FFFB reduces the BOT, body-PTV mean dose in the non-tumour volume.Conclusion: VMAT combined with FFFB will produce a highly conformal plan, spare the OAR’s, deliver fast and dose fall off in the body-PTV region is more as compared to ۳DCRT and DCA. The VMAT will more advantage to treat the multiple lesions simultaneously and reducing the intra-fraction motion error in liver SBRT.