Dosimetric comparision between RapidArc and fixed gantry intensity modulated radiation therapy in treatment of liver carcinoma

Abstract

Objective To compare the dosimetric difference of RapidArc and fixed gantry IMRT for liver carcinoma.Methods The CT data of 10 liver cancer patients were used to design 3 groups of treatment plan:IMRT plan,single arc RapidArc plan(RA1) ,and dual arc RapidArc plan(RA2).The planning target volume (PTV) dosimetric distrubition,the organs at risk (OAR) dose,the normal tissue dose,mornitor units(MU) and treatment time were compared.Results The maximum dose of PTV in RA1 and RA2 plans were lower than that of IMRT(Z = -2.090,-2.666,P ＜ 0.05).RapidArc groups had an improved 90% prescription dose conformity index than IMRT(Z = -2.805,-2.809 ,P ＜ 0.05).For organs at risk,RapidArc group plan had a significantly lower dose in V40 of stomach and small bowel than I MRT plan,but higher in mean dose of left kidney (Z = -1.988,-2.191,P ＜ 0.05).The values of V5,V10 and V15 of healthy tissue in RapidArc plan groups were higher than those in IMRT plan,while the values of V20 ,V25 and V30 of healthy tissue in RapidArc plan groups were lower than those in IMRT plan.The number of computed MU/fraction of Rapid Arc plan was 40% or 46% of IMRT plan and the treatment time was 30% and 40% of IMRT.Conclusion RapidArc showed improvements in conformity index and healthy tissue sparing with uncompromised target coverage.RapidArc could lead to the less MU and shorter delivery time compared to IMRT. Key words: RapidArc; IMRT; Liver carcinoma; Dosimetry