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Device Technologies and Biomedical Robotics

Device Technologies and Biomedical Robotics - Poster Session D

Poster W10 - A New Real-Time Visualization Tool for Monitoring Safe Medical Steerable Needle Deployment

Friday, October 25, 2024
3:30 PM - 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Robotic steerable needles are minimally invasive medical devices that are able to curve when deployed into tissue, allowing them to avoid critical anatomy. Recently, successful in vivo animal studies demonstrated that they can reach sites in the body that were previously unreachable in a minimally invasive way. However, steerable needles have significant curvature constraints. Therefore, it is difficult for human operators to manually determine safe deployment plans and to control steerable needle deployment in a 3D anatomic environment. A variety of motion planning and control algorithms have been introduced to support safe needle deployment. Still, a physician remains in control of the deployment and closely monitors the progress, resulting in a conditional autonomy setting. During needle deployment, deviations from the original planned path can occur. In this case, it must be decided whether the target is still reachable without piercing critical anatomy or if the steerable needle must be retracted.
We introduce a visualization tool that provides real-time monitoring of needle deployment with respect to surrounding anatomy. Needle deployment simulation results show that the physician needs to monitor both needle position and orientation to determine target reachability. Based on these findings, our tool determines the current needle deviation in position and orientation separately, and visualizes it alongside the maximum allowed deviation in both. Thereby, it supports more informed physician monitoring during needle deployment, ensuring that the needle safely reaches the target. We demonstrate our visualization tool in simulation for a minimally invasive, percutaneous liver biopsy application.

Materials and

Methods:  We use geometric methods to pre-compute a safe region surrounding a selected motion plan preceding needle deployment. Notably, the maximum allowed deviation during deployment depends on the steerable needle’s curvature constraint, as this property limits its ability to correct deviations from the planned path in order to reach the target. Therefore, the safe region has a funnel-like shape to account for the needle’s increasingly limited ability for correction as it approaches the target. Target access can be further limited by critical anatomical obstacles, such as large blood vessels, that the needle must avoid. The safe region computation takes these limitations into account, and as long as the steerable needle stays inside this region, the target can be safely reached.
Our visualization tool consists of the following elements: (i) a needle representation showing the position and orientation of the physical needle with respect to anatomy, (ii) a line element connecting the motion plan and the needle tip, representing the current deviation in position, (iii) a cone shape representing the maximum allowed orientation deviation, (iv) a funnel-shaped shaded area representing the overall safe region, and (iv) two color gradient legends, each marking a color based on the ratio between current deviation and maximum allowed deviation for both position and orientation. The marked color is also used to change the colors of the line element and cone. All visual elements update in real-time based on the physical steerable needle’s tracked motion.

Results, Conclusions, and Discussions: Our steerable needle robot is conditionally autonomous, which means that the robot automatically plans a needle path and steers the needle through tissue, but a physician is closely monitoring the deployment and makes critical decisions. Monitoring needle deployment through a 3D environment on a 2D screen is challenging, as it can be hard to see how far the needle deviates from the planned path. Moreover, needle curvature constraints make it difficult for humans to gauge how much deviation can be corrected to safely reach the target. Our goal is to provide human operators with visual cues that address these challenges, enabling effective monitoring.
We simulated steerable needle deployment in a percutaneous liver biopsy scenario. We randomly sampled a target inside the liver and automatically computed a motion plan to the target based on critical anatomy segmented from a pre-operative CT scan. During an actual procedure, a physician would inspect the planned path thoroughly before approving it for automatic deployment. Our method then pre-computed the safe deployment region surrounding the motion plan, which enables real-time visualization updates during needle deployment. During a physical procedure, the steerable needle’s tip is equipped with an electromagnetic tracking device, which we use to visualize its motion relative to the segmented anatomy. We also use this tracker information to compute the needle’s current deviation from the planned path.
We simulated 100 needle deployments that deviated from a planned motion plan in the liver access scenario. Simulation results show that, on average, the needle reaches the maximum allowed orientation deviation significantly earlier than the maximum allowed position deviation. This means that monitoring only the current position deviation is insufficient in determining target reachability. Therefore, we introduce visual elements that enable monitoring of both position and orientation deviation and their allowed maxima.
In the future, we plan to track and model tissue deformation more accurately and include this important information in our real-time visualization. We hope to test this visualization tool in a user study with physicians to systematically evaluate each visual element and the overall effectiveness for monitoring steerable needle deployment.

Acknowledgements (Optional):