title: A volumetric method for estimation of breast density on digitized screen-film mammograms.
abstract: A method is described for the quantitative volumetric analysis of the mammographic density (VBD) from digitized screen-film mammograms. The method is based on initial calibration of the imaging system with a tissue-equivalent plastic device and the subsequent correction for variations in exposure factors and film processing characteristics through images of an aluminum step wedge placed adjacent to the breast during imaging. From information about the compressed breast thickness and technique factors used for taking the mammogram as well as the information from the calibration device, VBD is calculated. First, optical sensitometry is used to convert images to Log relative exposure. Second, the images are corrected for x-ray field inhomogeneity using a spherical section PMMA phantom image. The effectiveness of using the aluminum step wedge in tracking down the variations in exposure factors and film processing was tested by taking test images of the calibration device, aluminum step wedge and known density phantoms at various exposure conditions and also at different times over one year. Results obtained on known density phantoms show that VBD can be estimated to within 5% accuracy from the actual value. A first order thickness correction is employed to correct for inaccuracy in the compression thickness indicator of the mammography units. Clinical studies are ongoing to evaluate whether VBD can be a better indicator for breast cancer risk.
authors.affiliation: Imaging/Bioengineering Research, Sunnybrook and Women's College Health Sciences Centre, Department of Medical Biophysics, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.
authors.forename: Olga
authors.initials: O
authors.lastname: Pawluczyk
authors.forename: Bindu J
authors.initials: BJ
authors.lastname: Augustine
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Yaffe
authors.forename: Dan
authors.initials: D
authors.lastname: Rico
authors.forename: Jiwei
authors.initials: J
authors.lastname: Yang
authors.forename: Gordon E
authors.initials: GE
authors.lastname: Mawdsley
authors.forename: Norman F
authors.initials: NF
authors.lastname: Boyd
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation / Q000379:methods*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D008327:Mammography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity