Safer Motion Planning of Steerable Needles via a Shaft-to-Tissue Force Model

Abstract

Steerable needles are capable of accurately targeting difficult-to-reach clinical sites in the body. By bending around sensitive anatomical structures, steerable needles have the potential to reduce the invasiveness of many medical procedures. However, inserting these needles with curved trajectories increases the risk of tissue shearing due to large forces being exerted on the surrounding tissue by the needle's shaft. Such shearing can cause significant damage to surrounding tissue, potentially worsening patient outcomes. In this work, we derive a tissue and needle force model based on a Cosserat string formulation, which describes the normal forces and frictional forces along the shaft as a function of the planned needle path, friction parameters, and tip piercing force. We then incorporate this force model as a cost function in an asymptotically nearoptimal motion planner and demonstrate the ability to plan motions that consider the tissue normal forces from the needle shaft during planning in a simulated steering environment and a simulated lung tumor biopsy scenario. By planning motions for the needle that aim to minimize the tissue normal force explicitly, our method plans needle paths that reduce the risk of tissue shearing while still reaching desired targets in the body.

Multibody dynamic modeling of the behavior of flexible instruments used in cervical cancer brachytherapy

“…Insertion force-depth profiles of the catheter and obturator in S-shaped channels were shown to be strongly affected in this work by the curvature and diameterand to a lesser extent torsion-of these channels. It has been theoretically shown that the insertion force increases exponentially with cumulative curvature for a rod with negligible bending rigidity, 43 or quadratically in a frictionless and zero-clearance channel. 30 Laan et al similarly showed that the insertion forces of catheters and obturators increase in channels with decreasing radius of curvature.…”

“…8 Differences between the measured peak insertion forces in this work and the latter may be explained by the difference in coefficient of friction between instrument and channel, which (theoretically) may be exponentially related to the required insertion force. 37,43,46 The effect of channel diameter on the insertion force of elastic rods in curved channels has been scarcely studied, although the work by Liu et al provides some insights. 44 The strong dependence of flexible instrument behavior on channel diameter stresses the importance of adequate applicator (channel) geometry consistency checks, especially when considering 3D printing.…”

“…Kinematic models for BT catheters in curved channels that have been introduced were based on models for steerable needles. [9][10][11] The modeling of deformations and associated forces and moments of slender elastic rods inside rigid (circular) channels or environment has been the topic of several studies for different applications: (i) drill string buckling, [24][25][26][27] (ii) serpentine locomotion, [28][29][30] (iii) concentric tube instruments, [31][32][33] and (iv) (steerable) catheter and guidewire insertion, [34][35][36][37][38][39][40][41][42][43][44] among others. Due to geometric, material, and physical nonlinearities in the problem formulation, most work resorts to numerical approaches.…”