Tissue site markers for in VIVO imaging

In diagnosing and treating certain medical conditions, it is often desirable to perform a biopsy, in which a specimen or sample of the suspicious tissue is removed for pathological examination, tests and analysis. As is known, obtaining a tissue sample by biopsy and the subsequent examination are typically employed in the diagnosis of cancers and other malignant tumors, or to confirm that a suspected lesion or tumor is not malignant. The information obtained from these diagnostic tests and/or examinations is frequently used to devise a therapeutic plan for the appropriate surgical procedure or other course of treatment. 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 non-uniform surface contour to enhance the acoustic signature. The markers have a characteristic form which is recognizably artificial during medical imaging. 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be accurately fixed to the biopsy site so as to resist migration from the biopsy cavity when a placement instrument is withdrawn, and when the marked tissue is subsequently moved or manipulated.