Needle placement accuracy during stereotactic localization mammography

Aim

To derive a mathematical model to describe the relationship between lesion position in the breast and measurements derived from the stereoradiographs to enable more accurate sampling of a lesion during stereotactic mammographic needle placement.

Materials and methods

The affect that registration errors have on the accuracy of needle placement when identifying the lesion on the stereoradiographs was investigated using the mathematical model.

Results

The focus-to-film distance of the x-ray tube and the horizontal distance of the lesion from the centre of rotation have little effect on error. Registration errors for lesions lying at a greater perpendicular distance in the breast from the centre of rotation produce smaller localization errors when compared with lesions sited closer. Lesion registration errors during marking of the stereoradiographs are exacerbated by decreasing the angle of x-ray tube swing.

Conclusions

When problems are encountered in making an accurate registration of the lesion on the stereoradiographs, consider the following error reducing strategies: (1) employ an approach that places the lesion the maximum distance away from the film cassette; (2) avoid reducing the angle of tube swing; and (3) consider sampling superficial and deep to, as well as at, the location indicated. The possibility of erroneous tissue sampling should be borne in mind when reviewing the pathology report.