Robotic Needle Steering in ex-vivo and in-vivo Tissue

Robotic needle steering is a promising technique to improve the effectiveness of needle based clinical procedures, such as biopsies and ablation, by computer controlled, curved insertions of needles within the body. In this paper, we explore the capabilities, challenges, and clinical relevance of tip asymmetric needle steering though experiments in ex vivo and in vivo tissue. We evaluate the repeatability of needle insertions in inhomogeneous biological tissue and compare ex vivo and in vivo needle steering. We found that blood perfusion does effect needle steering, particularly in liver, and that steerable needles do not seem to damage tissue more than conventional stainless steel needles. We demonstrated a minimum radius of curvature of pre-bent needles in ex vivo tissue of 5.23 cm and in vivo tissue of 10.4 cm. This discrepancy could be due to the increased stiffness and increased effect of inhomogeneity due to perfused blood vessels in vivo. We also found that steerable needles do not seem to exhibit enough curvature in prostate to be clinically relevant which indicates the need to improve needle steering design for applications to the prostate.