| abstract |
The invention is for a biopsy instrument having a stationary shaft secured to which is a stylet such that, once secured, the stylet does not move relative to the instrument. The stylet is telescopically received by a cannula which is mounted to a spring-loaded guide; the cannula and the guide move between charged and discharged positions. Also provided is a safety cap, which travels within slots formed in opposite sides of the cylindrical casing that houses the shaft, the guide and the spring. Retracting the safety cap moves the guide and the cannula from the discharged to the charged position where a release lever engages the guide. The safety cap covers the release lever to prevent accidental actuation of the instrument. The instrument is fired by sliding the safety cap forward and depressing the exposed release lever, which allows the spring to drive the cannula forward, toward the discharged position and over the stationary stylet, so that a tissue sample may be taken. Further, the biopsy instrument has a sealed chamber disposed behind the cannula. The sealed chamber creates a vacuum when the biopsy instrument is discharged. The vacuum aids in retaining the tissue sample within the cannula. |