Current status and issues of screening digital mammography in Japan

Digital systems have replaced screen-film systems, and have already been used for a screening program. The diagnostic performance of digital systems has been compared with that of screen-film systems, as the golden standard of breast cancer screening. Several studies have demonstrated they are superior to screen-film mammography; others have shown performance is comparable. The validity of digital screening mammography has been demonstrated. Regarding the method of interpretation of digital screening mammograms, the performance of hard-copy and soft-copy reading has been reported to be comparable, although the environment of soft-copy reading was premature. Soft-copy reading seems more promising in the future as a result of the development of both hardware and software. However, many aspects of quality assurance of soft-copy reading (e.g. standard specifications of viewing workstation, contrast visibility and resolution, ambient light) which remain undetermined should be clarified in the Japanese guideline. In Japan the average glandular dose in screening digital mammography is higher than that in screen-film mammography. Most (93.2%) are under 2 mGy for each radiation exposure. The risk of breast cancer by radiation exposure is regarded as higher than before in the 2007 recommendations of the ICRP. Management of radiation exposure is a continuing challenge.