An evaluation of the relationship between compressed breast thickness and glandular dose, within the breast screening service

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This project aims to investigate the relationship between compressed breast thickness (CBT) in mm and mean glandular dose (MGD) in mGy for two differing mammography units. The units are a 28 Kvp fixed molybdenum filter and target mammomat (Siemens 300) (Young et al 1996) and an Automatic Quality Beam System unit, which alters Kvp, filter and target material (Siemens 3000) (Young et al 1996), both units being commonly used in the NHSBSP. The outcome revealed that using a fixed 28 Kvp molybdenum filter and target, the CBT and MGD relationship exists exponentially. Breasts with a CBT of greater than 60 mm were at risk of receiving a MGD greater than recommended by NHSBSP Publication 37 1998, of 2 mGy. The Automatic Quality Beam System demonstrated overall a more erratic relationship between CBT and MGD, mainly due to target and filter material changing. However, it allowed the MGD at greater values of CBT to be reduced, with 2 mGy not exceeded up to 70 mm CBT. The use of Automatic Quality Beam System mammomats is highly recommended within the NHSBSP to maximise image quality while maintaining low glandular dose.