Measurement of patient exposure dose on X-ray screening mammography

X-ray mammography is the most effective method to produce a high photographic sensitivity in the early detection of breast cancer in which palpation is impossible. Mammography can be adapted to a screening check aimed at discovering abnormal remarks in females without the subjective symptom. However, in order to justify examining a seemingly healthy group in screening mammography, it is necessary to perform with an appreciation of the risk of carcinogenesis that may be associated with the absorbed radiation dose to the breast (patient exposure dose), and to guarantee an optimization of radiological protection. To do so, it is necessary to control the individual patient exposure dose in screening mammography. Moreover, when estimating patient exposure doses, it is important that breast composition is investigated objectively. In this study, a breast dosimetry system that includes digitization of a mammogram for investigating the individual breast composition was built on the basis of the dosimetry method for quality control of screening mammography. It is thought that this system has 10% or less of an error factor including the error determination of breast composition. Patient exposure doses of 124 examples from 76 patients in Japan were actually estimated by this system. Their values were clearly lower than the maximum acceptable dose recommended by the American College of Radiology and Japan.