Breast Characteristics and Dosimetric Data in X Ray Mammography - a Large Sample Worldwide Survey

Average Glandular Dose (AGD) is the quantity generally accepted for dose monitoring of X ray mammographic examinations. A survey of breast characteristics (compressed breast thickness, peak breast density) and AGD values was carried out on a database describing the acquisition conditions of 147,487 routine mammographic images acquired in Europe, North America and Asia-Pacific on GE Healthcare Senographe DS and Essential mammographic equipment. These systems compute the breast density in the densest part of the image and the related AGD using normalized glandular dose values interpolated from published tables. The correlation between peak breast density and compressed breast thickness was determined for the different geographical zones, as well as the distributions of the AGD. Breasts in Asia-Pacific were on average significantly thinner and denser than in Europe and North America. Breasts in North America were on average significantly thicker and denser than in Europe. The average AGD per image was 1.42mGy in North America and Asia-Pacific, and 1.48mGy in Europe. We computed the difference in AGD values between an individual density correction factor based on the peak breast density and a population-averaged density correction factor, as routinely used for dosimetry surveys in Europe. The resulting collective AGD values derived from the two distributions were similar (difference <5%), while the individual AGD values differed by up to 30%. Breast dosimetry can be improved by replacing the population-averaged breast density by the individual volumetric breast density.