title: Monte Carlo calculation of conversion coefficients for dose estimation in mammography based on a 3D detailed breast model.
abstract: OBJECTIVE
  At present, the Chinese specification for testing of quality control in x-ray mammography is based on a simple breast model, and does not consider the glandular tissue distribution in the breast. In order to more precisely estimate the mean glandular dose (MGD) in mammography for Chinese women, a three-dimensional (3D) detailed breast model based on realistic structures in the breast and Chinese female breast parameters was built and applied in this study.
  
  
  METHODS
  To characterize the Chinese female breast, Chinese female breast parameters including breast size, compressed breast thickness (CBT), and glandular content were investigated in this study. A mathematical model with the detailed breast structures was constructed based on the Chinese female breast parameters. The mathematical model was then converted to a voxel model with voxels. The voxel model was compressed in craniocaudal (CC) view to obtain a deformation model. The compressed breast model was combined with the Chinese reference adult female whole-body voxel phantom (CRAF) to study the effects of backscatter from the female body. Monte Carlo simulations of the glandular dose in mammography were performed with Geant 4. The glandular tissue dose conversion coefficients for breasts with different glandular contents (5%, 25%, 50%, 75%, and 100% glandularity) and CBTs (3 cm, 4 cm, 5 cm, and 6 cm) were calculated, respectively, at various x-ray tube voltages (25 kV, 28 kV, 30 kV, 32 kV, and 35 kV) for various target/filter combinations (Mo/Mo, Mo/Rh, Rh/Rh, and W/Rh).
  
  
  RESULTS
  A series of glandular tissue dose conversion coefficients for dose estimation in mammography were calculated. The conversion coefficients calculated in this study were compared with those estimated with the simple breast model. A discrepancy of 5.4-38.0% was observed. This was consistent with the results obtained from the realistic breast models in the literature.
  
  
  CONCLUSIONS
  A 3D detailed breast model with realistic structures in the breast was constructed based on the Chinese female breast parameters. It was used to calculate glandular tissue dose conversion coefficients for mammography. Although the accuracy of the proposed model could not be directly assessed, the consistency of the obtained results with previously performed analyses increases the confidence in the applicability of the proposed model. The proposed model could be used in dose estimation and dose optimization for mammography of Chinese women.
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing, 100084, China.|Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, 100084, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing, 100084, China.|Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, 100084, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Qiu
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing, 100084, China.|Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, 100084, China.
authors.forename: Li
authors.initials: L
authors.lastname: Ren
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing, 100084, China.|Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, 100084, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.affiliation: Nuctech Company Limited, Beijing, 100084, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Nuctech Company Limited, Beijing, 100084, China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Li
authors.affiliation: Beijing Tongren Hospital, Captial Medical University, Beijing, 100730, China.
authors.forename: Yantao
authors.initials: Y
authors.lastname: Niu
authors.affiliation: Department of Engineering Physics, Tsinghua University, Beijing, 100084, China.|Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, 100084, China.
authors.forename: Junli
authors.initials: J
authors.lastname: Li
mesh_terms: D001940:Breast; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008327:Mammography; D009010:Monte Carlo Method; D011829:Radiation Dosage; D011874:Radiometry; D014965:X-Rays
keywords: Monte Carlo; conversion coefficient; detailed breast model; mammography; mean glandular dose