Collaborative robot assisted smart needle placement

Needles are key tools to realize minimally invasive interventions. Physicians commonly rely on subjectively perceived insertion forces at the distal end of the needle when advancing the needle tip to the desired target. However, detecting tissue transitions at the distal end of the needle is difficult since the sensed forces are dominated by shaft forces. Disentangling insertion forces has the potential to substantially improve needle placement accuracy.We propose a collaborative system for robotic needle insertion, relaying haptic information sensed directly at the needle tip to the physician by haptic feedback through a light weight robot. We integrate optical fibers into medical needles and use optical coherence tomography to image a moving surface at the tip of the needle. Using a convolutional neural network, we estimate forces acting on the needle tip from the optical coherence tomography data. We feed back forces estimated at the needle tip for real time haptic feedback and robot control. When inserting the needle at constant velocity, the force change estimated at the tip when penetrating tissue layers is up to 94% between deep tissue layers compared to the force change at the needle handle of 2.36 %. Collaborative needle insertion results in more sensible force change at tissue transitions with haptic feedback from the tip (49.79 ± 25.51)% compared to the conventional shaft feedback (15.17 ± 15.92) %. Tissue transitions are more prominent when utilizing forces estimated at the needle tip compared to the forces at the needle shaft, indicating that a more informed advancement of the needle is possible with our system.

Novel Steerable Smart Needle With a Built-In Recovery Mechanism for Multiple Actuations

Smart Memory Alloys have brought a range of new capabilities to existing and novel designs due to their unique properties and ability to induce stress and strain in the material due to thermomechanical loading. Shape memory alloy-based smart material has widely been used and studied for biomedical applications. This includes smart needle for percutaneous procedures, self-expanding Nitinol grafts, stents, and other permanent internal devices. The smart needle is a needle in which deflection/path of the insertion in tissues can be controlled by incorporating Nitinol wire actuators on the body of the needle. However, smart needle designs proposed in the past lack both flexibility for multidirectional angles, and they do not allow for multiple martensitic phase transformations and are thus not repeatable. Each time the Nitinol wire is actuated, the wire would have to be manually reset to its initial length. Active materials like Nitinol require a bias force or mechanism that reverts the activated form of the needle back to its original martensitic form, which in the case of active needles is a straight wire. The lack of a recovery mechanism means that subsequent austenite transformations for deflection in opposing or similar trajectories cannot be performed as the system will not fully reset itself once cooled. In our proposed design, four Nitinol wires are embedded into a needle and act independently of one another to provide multi directional needle deformations. By providing tension onto a flexible 3D printed needle shaft, they can pivot a hard needle tip into any given direction. Once the needle’s deformation is complete, the material’s natural rigidity coupled with other Nitinol wires pulling resistance will restore the initial length of the actuated wire as it cools. This allows the needle to undergo a martensitic transformation and then subsequent cooling followed by additional phase transformation in a different direction. This makes the needle’s mechanism repeatable and functional for multiple insertions.