Radiation exposure in X-ray mammography - A review.

When discussing the radiation risk of X-ray mammography, the magnitude of t he dose applied has decisive importance. The radiation exposure of the brea st is the predominant factor in risk considerations, since it contributes m ore than 98% to the effective dose of this examination. At present, it is g enerally assumed that, with regard to cancer induction by ionizing radiatio n, the glandular tissue is the most vulnerable part in the breast. Therefor e, the average glandular dose, i.e., the mean value of the absorbed dose in the glandular tissue, is used for a description of the radiation risk. The average glandular dose cannot be measured directly, but is calculated unde r certain assumptions from the experimentally determined entrance surface a ir kerma OF entrance surface dose by the use of a so-called conversion fact ors. During the seventies, i.e., in the era of the industrial type X-ray fi lm, the mean value of the average glandular dose per exposure for a larger sample of patients (n>100) was about 20 mGy. Due to the progress in radiogr aphic technique such as, for example, the use of sensitive film-screen syst ems, optimized radiation qualities and modern automatic exposure control un its this value has now decreased to about 1 mGy. Further dose reductions se em possible by the introduction of digital image receptors.