Biopsy apparatus with vacuum relief

1. A method of relieving vacuum in a biopsy apparatus that comprises a first cannula defining a first lumen therethrough and a tissue-receiving opening in communication with the first lumen; a second cannula slidably disposed in the first lumen, wherein the second cannula defines a second lumen therethrough, and a vacuum source in fluid communication with the second lumen, the method comprising:

applying vacuum from the vacuum source through at least one motor to the second lumen;

providing an open leak path through an engagement area between a first cannula mounting hub and a housing that permits fluid communication between the first lumen and the atmosphere, the leak path is continuously open and fluid is drawn from the leak path and through the first cannula;

retracting the second cannula to permit tissue to prolapse into the tissue receiving opening due to the vacuum created through the second lumen;

translating the second cannula toward the distal end of the first cannula to sever the tissue that has prolapsed into the tissue receiving opening;

aspirating the severed tissue through the second lumen; and

selectively relieving vacuum distally of the severed and aspirating tissue by retracting the second cannula away from the distal end of the first cannula thereby permitting the second lumen to communicate with the first lumen and the leak path while a portion of the biopsy apparatus, including the tissue receiving opening, is positioned within tissue.

2. The method of claim 1 , wherein the vacuum is applied continuously.

3. The method of claim 1 , wherein the second cannula is at least one of (i) rotated within the first cannula and (ii) reciprocated within the first cannula, to sever the tissue that has prolapsed into the tissue receiving opening.

4. The method of claim 3 , wherein the second cannula is rotated simultaneously when the second cannula is translated.

5. The method of claim 1 , wherein a distal end of the second cannula is spaced inwardly from a proximal edge of the tissue receiving opening of the first cannula, prior to the second cannula being translated distally toward the distal end of the first cannula to cut tissue.

6. The method of claim 1 , wherein the fluid that that is drawn from the leak path is air.

7. A method of controlling a biopsy device to clear a tissue sample disposed within the biopsy device, the biopsy device comprising a continuously open leak path, an inner cannula and an outer cannula, the outer cannula having a outer lumen, a distal end and a tissue receiving opening proximal to the distal end, the inner cannula having an inner lumen and being disposed coaxially and slidably relative to the outer cannula, the leak path being in fluid communication the outer lumen and a fluid source, the method comprising:

applying vacuum from a vacuum source though the inner lumen;

retracting the inner cannula from a position distal to a distal edge of the tissue receiving opening to a position proximal to the distal edge of the tissue receiving opening;

drawing a fluid into the biopsy device through the leak path to relieve a vacuum formed distal of the tissue sample.

8. The method of claim 7 , wherein the fluid source is atmospheric air.