Using new technology to achieve the ideal mammogram

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It is well established that the ideal mammogram should have the optimal average film density, which depends on selecting the correct exposure. It also needs to have the optimal contrast. This is more difficult to ensure as it depends on the intrinsic breast contrast, the radiographic contrast and film contrast. The operator has control over the radiographic contrast, by adjusting the kV, target material and filter material used and modern machines provide the operator with a greater range of choices. The use of modern very high contrast mammographic films may affect the optimal choice of beam quality.

By theoretical modelling and experimental measurement it is possible to estimate the impact of beam quality choices on dose, contrast and exposure time. The publication of new data on the composition of the breasts involved in screening allows this modelling to be more accurate than in the past. This presentation discusses the principles that should guide operators in making these choices. The two pitfalls to be avoided are excessive contrast due to using a very high contrast film with an inappropriate beam quality (eg 25 kV Mo/Mo). Equally one should avoid excessive contrast loss caused by using an inappropriate target filter combination (eg W/Rh).