Abstract: Breast is one of the most sensitive organs to radiation. In 2007, ICRP increased the tissue weighting factor for the breast from 0.05 to 0.12,which makes the accurate evaluation of breast dose more important. But in the human voxel phantom, the structure of breast is not elaborate enough because of the limitation of image resolution used for phantom modeling. This will probably affect the accuracy of breast dose calculated in simulation. A lot of research works on detailed breast modeling has been carried out in recent years internationally, but there is no research in this area in China. The model of detailed breast is established in this paper using mathematical modeling method. The model includes lactiferous sinuses, lactiferous ducts, lobules and adipose tissue. Model is voxelized and then merges with Chinese reference adult female voxel model. This model is used to calculate dose conversion coefficients of breast gland for external photon exposures in AP geometry and results are compared with that calculated using old model. The results show that the difference between the results of two models is up to 30% at low photon energy. There is no much difference at high photon energies.

Key words: breast, detailed breast model, monte carlo, external radiation