A PILOT SURVEY OF RADIATION-DOSES RECEIVED IN THE UNITED-KINGDOM BREAST SCREENING-PROGRAM

A survey of radiation dose and compressed breast thickness was conduct ed in samples of women undergoing mammography in the United Kingdom Na tional Health Service breast screening programme. The aims were to det ermine the average value and distribution of dose and thickness, and t o identify technical difficulties in carrying out such a survey. Value s of breast thickness and mean glandular dose, calculated from exposur e factors and measured X-ray beam parameters, were collected for 4633 women in 92 screening units in 1994 and 1995. The median (lower quarti le, upper quartile) dose per film was 1.7 (1.2, 2.4) mGy for the medio lateral oblique view (mean thickness 57 mm) and 1.4 (1.1, 2.0) mGy for the craniocaudal view (mean thickness 52 mm). The median dose per wom an was 1.8 (1.3, 2.5) mGy for a one-view examination and 3.3 (2.3, 4.6 ) mGy for a two-view examination. The dose per film showed an exponent ial relationship to breast thickness, but no relationship was found be tween median dose and median breast thickness in the different screeni ng units, possibly because of errors in breast thickness measurement. The values of breast thickness and dose were generally consistent with those in other published surveys, allowing for differences in radiogr aphic technique. No relationship between breast dose and standard opti cal density was demonstrated. Some recommendations for the conduct of future surveys of breast dose in the UK are proposed.