Abstract: Objective:Evaluation of breast conserving surgery intensity modulated radiation therapy(IMRT) dosimetric advantages of image guided assessment of breast conserving surgery in IMRT and the planning traget volume planning target volume border positioning errors.Methods:Six patients received breast-conserving surgery in early breast cancer patients,the implementation of the whole breast image guided intensity modulated radiation therapy 50 Gy,tumor bed volume electronic wire and evaluation of breast 10 Gy target dose uniformity and the surrounding normal tissue dose and volume,the clinical toxicity,statistical position error.Results:Target dose homogeneity and normal tissue by the amount of the allowed range,the direction of the left and right positioning error 0.3cm,the other direction 0.5 cm.Conclusions:The whole breast after breast conserving IMRT target dose uniformity,normal tissues received a small dose,slight clinical toxicity,and poor reproducibility.Using cone-beam CT image-guided radiation therapy to reduce setuperrors.