A method of evaluating and minimizing geometric unsharpness for mammographic X-ray units

A method for measuring and minimizing the effects of geometric unsharpness in mammography involves using a star resolution pattern to determine the equivalent focal spot size of mammographic x-ray units. With this measurement, the limit of resolution at any plane within the breast and the focal spot-to-object distance necessary to obtain the desired limit of resolution are determined. Six mammographic x-ray units were evaluated with this technique. Results show that the resolution capability of four of these units is limited by geometric unsharpness, such that the resolution capability of present mammographic recording systems is not fully utilized.