Radiation doses in the UK trial of breast screening in women aged 40-48 years.

Although data have been published on the radiation doses involved in screening women in the UK in the age range 50-64 years, data have not been published for the screening of younger women, when one might expect higher doses and a different risk benefit balance. Therefore, data on the radiation doses arising from screening younger women (age range 40-48 years) as part of the UK age trial have been collected and reviewed. Each of the screening centres participating in the trial was asked to submit measurements of doses for samples of approximately 50 or 100 women. The doses for 2296 women were received. The dose estimates were corrected to take account of variations in composition with age and breast thickness and in the spectra used. The average received dose was 2.5 mGy per oblique film and 2.0 mGy per craniocaudal film. Although these doses are about 7% higher than those calculated for the screening of older women, this was owing to differences in equipment rather than age of the women. Age itself was not found to be a significant factor affecting the dose to screened women aged over or under 50 years. An identifiable sub-group of women with larger breasts who were screened using higher dose systems received doses that were about 4.2 times the average, and should be considered in any risk benefit analysis. Where modern mammography systems with automatic beam quality selection and alternative target and filter materials had been introduced, there was a 15% reduction in average received dose and up to a 50% reduction in received dose for large breasts.