Novel needle cutting edge geometry for end-cut biopsy.

PURPOSE: To introduce and determine the biopsy length performance of the novel enhanced cutting edge (ECE) needle tip design, which contains high inclination angles that allow for more efficient tissue cutting.

METHODS

ECE and regular two-plane symmetric needle tip's biopsy performance and cutting force are compared over a series of needle insertion experiments into bovine liver under varying levels of internal needle vacuum. An earlier developed needle tip force model is also applied. From these experiments and force model, the effect of needle tip geometry and vacuum on biopsy performance and force is studied.

RESULTS

Biopsy sample length is on average 22%, 30%, and 49% longer for ECE needles compared to that of regular needles for the internal pressures of 0, -33.9, and -67.7 kPa, respectively. For ECE needles the vacuum level of -67.7 kPa produces on average biopsy lengths that are 41%, 31%, 29%, 45%, and 42% longer compared to no vacuum for two-plane needle tip bevel angles of 10°, 15°, 20°, 25°, and 30°, respectively. The force results show the ECE needle can be inserted with less initial insertion force than the regular two-plane needle for needles where the needle tip is fully contacting the tissue upon insertion. Vacuum is also showed to help lower insertion forces.

CONCLUSIONS

The novel ECE needle tip design outperforms the regular two-plane symmetric needle by yielding longer biopsy samples and lower insertion forces, thereby demonstrating the benefits of needle geometries that contain higher inclination angles. The use of vacuum further improves the ECE needle tip biopsy sample length and lowers insertion forces.