Evaluation of nonholonomic needle steering using a robotic needle driver

Accurate needle placement is a common need in the medical environment. While the use of small diameter needles for clinical applications such as biopsy, anesthesia and cholangiography is preferred over the use of larger diameter needles, precision placement can often be challenging, particularly for needles with a bevel tip. This is due to deflection of the needle shaft caused by asymmetry of the needle tip. Factors such as the needle shaft material, bevel design, and properties of the tissue penetrated determine the nature and extent to which a needle bends. In recent years, several models have been developed to characterize the bending of the needle, which provides a method of determining the trajectory of the needle through tissue. This paper explores the use of a nonholonomic model to characterize needle bending while providing added capabilities of path planning, obstacle avoidance, and path correction for lung biopsy procedures. We used a ballistic gel media phantom and a robotic needle placement device to experimentally assess the accuracy of simulated needle paths based on the nonholonomic model. Two sets of experiments were conducted, one for a single bend profile of the needle and the second set of tests for double bending of the needle. The tests provided an average error between the simulated path and the actual path of 0.8 mm for the single bend profile and 0.9 mm for the double bend profile tests over a 110 mm long insertion distance. The maximum error was 7.4 mm and 6.9 mm for the single and double bend profile tests respectively. The nonholonomic model is therefore shown to provide a reasonable prediction of needle bending.