Abstract：Objective To analyze the difference in dosimetric characteristics and protection of organs at risk(OAR)between volumetric modulated arc therapy(VMAT)and intensity modulated radiation therapy(IMRT) for breast cancer patients after breast-conserving therapy.Methods Ten patients with breast cancer (in the left breast)were planned in different ways.The prescribed dose for PTV was 50Gy/25f,while the dose for PGTVtb was boosted to 60 Gy/25 f.The dosimetric parameters of the two different plans, including the dose conformity index(CI)and homogeneity index(HI) of PTV,dose volume histogram(DVH)of normal tissue coverage,MU and delivery time were also analyzed.Results The dose distribution CI of the VMAT plan were better than that of IMRT(P<0.05).Compared with IMRT,VMAT increased the volume of the ipsilateral lung at 5,10,20Gy and the volume of the contrlateral lung at 5 Gy(P<0.05).Conclusion The two treatment modalities can satisfy clinical requirements. The dose distribution CI of the VMAT plan is better than that of IMRT.Also,the VMAT technology can shorten the duration of treatment.
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