Comparison of forward and inverse intensity modulation radiotherapy planning for breast cancer after breast-conservative surgery / 中华放射医学与防护杂志

ABSTRACT

Objective To compare the dosimetric difference in forward intensity modulation radiotherapy (fIMRT)and inverse IMRT(iIMRT)planning for breast cancer.Methods Six patients received radiotherapy alone after left breast-conserving surgery were selected.For each patient,two treatment phns(flMRT and iIMRT)were designed with Pinnacle3 7.4f.In each plan,the volume of PIT received prescription dose was not less than 95 %.The dosimetrie parameters were assessed with dose volume histograms in planning target volume (PIT)and organ of around risk(OAR).Results Of flMRT and ilMRT plans,the PTV average canformal indexwere(0.67±0.06)and(0.66±0.06)(t = 2.423,P ＞ 0.05),average homogeneity index were (28.2±6.0)% and(26.1±6.8)%(t = 2.164,P ＞ 0.05);the volume of left lung received 20 Gy(V20)were(18.7±3.3)% and(17.0±2.8)%(t =5.087,P<0.05),and V30 of left lung were(15.5±3.0)%and(14.0±2.6)%(t =7.272,P<0.05);V30 of heart were(4.1±3.1)% and(3.5±2.5)%(t=1.916,P ＞ 0.05);the total monitor units were(262±5)MU and(308±14)MU(t = 7.515,P < 0.05).Conclusions There were no significant differences of CI,HI,and V30 of heart between flMRT and iIMRT.Because of fewer MUs,fIMRT plan could reduce the machine abrasion and treatment time,but V30 and V30 of left lung are higher significantly than iIMRT plan.