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  4. Decoupling Steerability from Diameter: Helical Dovetail Laser Patterning for Steerable Needles

Decoupling Steerability from Diameter: Helical Dovetail Laser Patterning for Steerable Needles

AUTHORS

Rox Margaret , Emerson Maxwell , Ertop Tayfun Efe , Fried Inbar , Fu Mengyu , Hoelscher Janine , Kuntz Alan , Granna Josephine , Mitchell Jason , Lester Michael , Maldonado Fabien , Gillaspie Erin A , Akulian Jason A , Alterovitz Ron , Webster Robert J . IEEE access : practical innovations, open solutions. 2020 10 2; 8(). 181411-181419

ABSTRACT

The maximum curvature of a steerable needle in soft tissue is highly sensitive to needle shaft stiffness, which has motivated use of small diameter needles in the past. However, desired needle payloads constrain minimum shaft diameters, and shearing along the needle shaft can occur at small diameters and high curvatures. We provide a new way to adjust needle shaft stiffness (thereby enhancing maximum curvature, i.e. “steerability”) at diameters selected based on needle payload requirements. We propose helical dovetail laser patterning to increase needle steerability without reducing shaft diameter. Experiments in phantoms and ex vivo animal muscle, brain, liver, and inflated lung tissues demonstrate high steerability in soft tissues. These experiments use needle diameters suitable for various clinical scenarios, and which have been previously limited by steering challenges without helical dovetail patterning. We show that steerable needle targeting remains accurate with established controllers and demonstrate interventional payload delivery (brachytherapy seeds and radiofrequency ablation) through the needle. Helical dovetail patterning decouples steerability from diameter in needle design. It enables diameter to be selected based on clinical requirements rather than being carefully tuned to tissue properties. These results pave the way for new sensors and interventional tools to be integrated into high-curvature steerable needles.

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