A survey of clinical factors and patient dose in mammography

A survey was conducted to estimate the mean glandular dose (MGD) for women undergoing mammography and to report the distribution of doses, compressed breast thickness, glandular tissue content, and mammographic technique factors used. From 24,471 mammograms, of 6,006 women, clinical data were collected. The survey data included mammograms from seven modern units using a molybdenum (Mo) anode and either Mo or rhodium (Rh) filter. Exposure factors for each mammogram were recorded automatically onto a floppy disk on each unit. All mammography units were calibrated individually using breast tissue equivalent attenuation slabs of varying glandular content, so the breast glandular content could be estimated on the basis of exposure factors and compressed breast thickness. The MGD was estimated for each mammogram based on the normalized glandular dose and calculated entrance exposure in air. The survey found a median MGD of 2.6 mGy. The median breast glandular tissue content was 28% and the median compressed breast thickness was 5.1 cm. Also, patient attenuation data were converted to equivalent BR-12 and acrylic thickness to help determine appropriate phantom thicknesses required for mammography unit automatic exposure control performance assessment.