Guiding Elastic Rods With a Robot-Manipulated Magnet for Medical Applications

Abstract

Magnet-tipped, elastic rods can be steered by an external magnetic field to perform surgical tasks. Such rods could be useful for a range of new medical applications because they do not require either pull wires or other bulky mechanisms that are problematic in small anatomical regions. However, current magnetic rod steering systems are large and expensive. Here, we describe a method to guide a rod using a robot-manipulated magnet located near a patient. We solve for rod deflections by combining permanent-magnet models with a Kirchhoff elastic rod model and use a resolved-rate approach to compute trajectories. Experiments show that three-dimensional trajectories can be executed accurately without feedback and that the system’s redundancy can be exploited to avoid obstacles.

Steerable Microinvasive Probes for Localized Drug Delivery to Deep Tissue

“…Bevel‐tip needle steering is driven by asymmetric tip geometry resulting in a net lateral force upon insertion in soft media that leads to a curved insertion trajectory . Asymmetric tip geometry can be a simple bevel or a more complex bent tip, both of which can be guided by closed‐loop control over implant position via needle rotation or magnetic actuation . These techniques have not, however, been put into clinical practice .…”

Flexible Instruments for Endovascular Interventions: Improved Magnetic Steering, Actuation, and Image-Guided Surgical Instruments

“…Results from this study showed decreased radiation exposure and safe and effective procedures [43]. Furthermore, Kratchman et al [32] demonstrated the guidance of a magnet-tipped rod along arbitrary 3-D trajectories using a single, robot-manipulated permanent magnet. The magnet was attached to a 6-DoF serial robot, which demonstrated trajectory following and obstacle avoidance using resolved-rate motion control.…”

“…Consequently, accurate mechanical models and continuous device localization are specific fundamental requirements of control strategies for magnetic catheter actuation [74]. Mechanical models used for accurately describing the system and environment include Euler-Bernoulli beam deflection [35], rigid link approximation [75], the Cosserat rod theory [32], and pseudorigid body modeling [76]. The localization of catheters has been demonstrated by accurately using electromagnetic tracking [27] and by observing the device shape and orientation using MR, US, and fluoroscopy.…”

“…This ferromagnetic material is widely utilized in catheter designs because it has strong magnetization, making it an excellent candidate for steering catheter tips [29]. Studies using both electromagnets [30], [31] and permanent magnets [32] for passive actuation have utilized Nd-Fe-B magnets in their catheter models, although the majority has implemented single magnetic components. Recently, Edelmann et al [33] demonstrated the modeling of different catheter geometries with multiple magnetic components and various boundary constraints.…”

Sensorless Estimation of the Planar Distal Shape of a Tip-Actuated Endoscope

“…physical point where robot is at least partially constrained, and applied loads [9]- [12]. Similar methods have been applied for continuum devices that rely on magnetic fields for actuation [5], [6], [13].…”