Abstract
For the optimization of the risk-benefit in mammography, accurate dosimetry requires standardization of both the methodology and dosimeter.
One of the important issues is the asse ssment of the average glandular dose under mammography. To this end, accurate measurement of half value layer and that of air kerma are of primary importance. To see the variation among facilities, the half value layer and the entrance dose were measured at eight facilities. In this series of measurement, a shallow type ionization chamber designed to fit with soft X-ray used in mammography was used.
This comparison indicates that, with the same radiographic condit ions, the variation of the dose among equipment was such that the ratio of the highest to the lowest was almost two. While the variation of the half value layer among equipment under the fixed tube voltage was as high as 15%.
