Technology to Improve Medical Interventions

N eedle insertion is a critical aspect of many medical treatments, diagnostic methods, and scientific studies, and is considered to be one of the simplest and most minimally invasive medical procedures. Robot-assisted needle steering has the potential to improve the effectiveness of existing medical procedures and enable new ones by allowing increased accuracy through more dexterous control of the needle-tip path and acquisition of targets not accessible by straight-line trajectories. In this article, we describe a robot-assisted needle-steering system that uses three integrated controllers: a motion planner concerned with guiding the needle around obstacles to a target in a desired plane, a planar controller that maintains the needle in the desired plane, and a torsion compensator that controls the needle-tip orientation about the axis of the needle shaft. Experimental results from steering an asymmetric-tip needle in the artificial tissue demonstrate the effectiveness of the system and its sensitivity to various environmental and control parameters. In addition, we show an example of needle steering in ex vivo biological tissue to accomplish a clinically relevant task and highlight challenges of practical needle-steering implementation. Needles are widely used in medicine to deliver treatments and acquire tissue samples for diagnosis due to their ability to reach subsurface targets with little trauma to the patient. In many procedures, accurate placement of the needle tip within an organ is vital for a successful outcome. Poor placement of a needle tip can result in problems such as false negatives from a biopsy, imprecise delivery of radiation therapy (such as radioactive seeds implanted during brachytherapy), and ablation of healthy tissues instead of cancerous tissues. Several factors, including errors in insertion location, needle bending, and tissue deformation, can lead to poor needle-tip placement. When such errors occur in clinical settings, the solution typically involves retraction and reinsertion—in current practice, a clinician has limited control over the path of a needle once inserted into the tissue. The ability to steer a needle inside the tissue could significantly improve the effectiveness of needle-based procedures. Needle steering allows access to subsurface targets unreachable by conventional straight needles, as shown in Figure 1. In some medical procedures, a straight-line path between a feasible insertion site and a desired target is