The myth of the 50-50 breast

M. J. Yaffe, John M Boone, N. Packard, O. Alonzo-Proulx, S. Y. Huang, C. L. Peressotti, A. Al-Mayah, K. Brock

Research output: Contribution to journalArticlepeer-review

199 Scopus citations


Purpose: For dosimetry and for work in optimization of x-ray imaging of the breast, it is commonly assumed that the breast is composed of 50% fibroglandular tissue and 50% fat. The purpose of this study was to assess whether this assumption was realistic. Methods: First, data obtained from an experimental breast CT scanner were used to validate an algorithm that measures breast density from digitized film mammograms. Density results obtained from a total of 2831 women, including 191 women receiving CT and from mammograms of 2640 women from three other groups, were then used to estimate breast compositions. Results: Mean compositions, expressed as percent fibroglandular tissue (including the skin), varied from 13.7% to 25.6% among the groups with an overall mean of 19.3%. The mean compressed breast thickness for the mammograms was 5.9 cm (σ=1.6 cm). 80% of the women in our study had volumetric breast density less than 27% and 95% were below 45%. Conclusions: Based on the results obtained from the four groups of women in our study, the "50-50" breast is not a representative model of the breast composition.

Original languageEnglish (US)
Pages (from-to)5437-5443
Number of pages7
JournalMedical Physics
Issue number12
StatePublished - 2009


  • Breast composition
  • Breast CT
  • Breast density
  • Dosimetry
  • Mammography
  • Mean glandular dose

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging


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