The invention is directed biopsy site markers and methods of marking a biopsy site, so that the location of the biopsy cavity is readily visible by conventional imaging methods, particularly by ultrasonic imaging. The biopsy site markers of the invention have high ultrasound reflectivity, presenting a substantial acoustic signature from a small marker, so as to avoid obscuring diagnostic tissue features in subsequent imaging studies, and can be readily distinguished from biological features. The several disclosed embodiments of the biopsy site marker of the invention have a high contrast of acoustic impedance as placed in a tissue site, so as to efficiently reflect and scatter ultrasonic energy, and preferably include gas-filled internal pores. The markers may have a nonuniform surface contour, such as a porous, irregular, frosted, faceted, multi-planar or lobulate surface, to enhance the acoustic signature. The markers have a characteristic form which is recognizable artificial during medical imaging. Typically the markers are deposited through an opening in the tissue created by the use of known surgical techniques or more preferably by a disclosed marker applicator device. The biopsy site marker may be accurately fixed to the biopsy site so as to resist migration from the biopsy cavity when a placement instrument is withdrawn, and when the marked tissue is subsequently moved or manipulated.
