USE OF A BREAST PHANTOM TO IMPROVE IMAGE QUALITY AND PATIENT EXPOSUREIN ONTARIO MAMMOGRAPHY FACILITIES

A survey of facilities performing mammography examinations in the Prov ince of Ontario was carried out over the period from 1988 to 1991. Tec hnical information was collected for a craniocaudal view of an average female patient. The image quality and patient skin entrance exposure were measured using an RMI mammography phantom and dosemeter for each facility. An image score and mean glandular breast dose were determine d for each facility. Radiographic visualisation of specks as small as 0.54 mm, fibres as small as 0.75 mm and masses as small as 1.00 mm was considered the minimum acceptable level of performance and gave an im age score of 10. Results of the initial 1988 survey identified a numbe r of phantom mammograms (16 out of 53) with image scores of less than 10 or patient entrance exposure values grater than the Ontario legisla ted maximum value of 900 mR (232 muC.kg-1). Such information was used as a basis for consultation in order to improve image quality and pati ent entrance exposure in such facilities. Results of the 1990/91 surve y indicated a substantial improvement with all facilities surveyed hav ing an image quality score of 10 or greater and a patient skin exposur e value less than the Ontario legislated maximum.