Stereotactic localization of breast lesions: How it works and methods to improve accuracy

A computer simulation of stereotactic breast biopsy was developed that para lleled the geometric configuration of a currently available breast biopsy s ystem. This model was developed to define and improve the targeting of brea st lesions with stereotactic biopsy techniques. Lesions must be clearly ide ntified and accurately targeted on both views for successful localization. Nonvisualization of a lesion may result from overlying tissue or from the g eometric configuration of the imaging system. Familiarity with the geometri c configuration of the biopsy unit, especially the location of the referenc e point and center of rotation, facilitates understanding of apparent chang es in lesion position (parallax shift). Inaccuracy in lesion targeting on o ne or both views will manifest predominantly as an error in the calculated z value (depth). The magnitude and direction of this error are largely dete rmined by the direction of the targeting error. Compensatory strategies inc lude use of a long-throw core biopsy gun or directional vacuum-assisted bio psy device and additional sampling along the z axis and should be accompani ed by critical evaluation of both pre- and postfire images. Understanding g eometric considerations as well as how targeting accuracy affects accuracy in lesion localization should lead to greater success in sampling even chal lenging breast lesions at stereotactic biopsy.