title: Torsional dynamics of steerable needles: modeling and fluoroscopic guidance.
abstract: Needle insertions underlie a diversity of medical interventions. Steerable needles provide a means by which to enhance existing needle-based interventions and facilitate new ones. Tip-steerable needles follow a curved path and can be steered by twisting the needle base during insertion, but this twisting excites torsional dynamics that introduce a discrepancy between the base and tip twist angles. Here, we model the torsional dynamics of a flexible rod-such as a tip-steerable needle-during subsurface insertion and develop a new controller based on the model. The torsional model incorporates time-varying mode shapes to capture the changing boundary conditions inherent during insertion. Numerical simulations and physical experiments using two distinct setups-stereo camera feedback in semitransparent artificial tissue and feedback control with real-time X-ray imaging in optically opaque artificial tissue-demonstrate the need to account for torsional dynamics in control of the needle tip.
authors.forename: John P
authors.initials: JP
authors.lastname: Swensen
authors.forename: MingDe
authors.initials: M
authors.lastname: Lin
authors.forename: Allison M
authors.initials: AM
authors.lastname: Okamura
authors.forename: Noah J
authors.initials: NJ
authors.lastname: Cowan
mesh_terms: D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005471:Fluoroscopy; D008954:Models, Biological; D009339:Needles; D065287:Robotic Surgical Procedures / Q000295:instrumentation* / Q000379:methods*; D054159:Torsion, Mechanical