Dosimetric and image quality comparison of two digital mammography units with different target/filter combinations:...

Our aim was to allocate a digital mammography unit to the screening programme on the basis of the ALARA (as low as reasonably achievable) radiation protection principle.

Two Hologic Selenia mammography units were studied: one with a molybdenum anode and the other with a tungsten anode. After optimisation of the image production chain, we evaluated doses in a phantom under standard conditions. In this phase, we exposed a polymethyl-methacrylate (PMMA) phantom to the two mammography units and recorded the exposure parameters used by them. The phantom was subsequently replaced by a dedicated Radcal ionisation chamber on which preliminary dose assessments were conducted. Image quality of the two systems was compared by exposing a phantom containing geometrical inserts and setting the exposure parameters used for the dose assessments on each mammography unit. Dosimetric assessments of exposure data were recorded from the mammographic examinations of approximately 400 women (1,600 exposures).

The unit with the tungsten anode achieved a lower patient dose. As a result, the Selenia-W device was allocated to the breast screening programme.