1. Field of the Invention
This invention relates generally to an apparatus for the percutaneous positioning of a radiopaque marker for identifying the location of a lesion in a stereotactic biopsy procedure. More particularly, the invention relates to an introducer having a hollow cannula in combination with a movable stylet and a radiopaque marker disposed within the cannula and ejected from it by movement of the stylet.
2. Related Art
Tissue biopsies are commonly performed on many areas and organs of the body where it is desirable to ascertain whether or not the biopsied tissue is cancerous. Often, a lesion or other tissue to be biopsied is identified through use of an imaging technique such as a computerized axial tomography (CAT) scan, ultrasonography, and mammography.
One problem commonly encountered, especially in breast biopsies, is that the lesion is so small that the biopsy reduces its size to the extent that it is no longer visible by the imaging method employed. In such circumstances, it is desirable to place a radiopaque marker at the site of the biopsy to enable the medical practitioner subsequently to locate the lesion quickly and accurately in the event complete removal of the affected tissue is indicated. This problem is currently met by placing a radiopaque marker at the biopsy area by means of a cannula or similar device housing the marker.
More particularly, one of the markers heretofore in use is a staple-type clip. The clip is introduced through a large-diameter cannula, specifically one of 11 gauge.
Some practitioners employ an embolization coil as a marker. This requires them to find a cannula or hollow needle of a size to receive the coil and some means to force the coil through the needle, all the while trying to keep these components together and sterile.
Prior devices for marking a biopsy area have several other disadvantages. A significant disadvantage is that the marker is not always completely ejected from the cannula or can be drawn back into or toward the cannula by the vacuum created upon the withdrawal of the cannula, which results in the marker being moved from the intended site, leading to inaccurate identification of the location of the biopsy area. A second major disadvantage is that current markers have a tendency to migrate within the tissue, also causing error in determining the biopsy location.