Magnetic Coil Catheter Steering With Minimum-Current Torque Control
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Solution Overview
Problem
Existing medical devices face challenges in navigating narrow vessels due to issues such as vessel perforation, loss of torque transmission, and image distortion in MRI-guided interventions, with current actuation methods like thermal and hydraulic actuation posing safety risks and introducing bulkiness or weight, and microcoil-based steering causing Joule heating.
Innovation Solution
A method for controlling a medical device's movement in a magnetic field using a set of coils, optimizing current supply to minimize torque and deformation, with a quad-coil configuration and laser-machined Archimedean spiral design to achieve precise steering without active cooling, mitigating heating effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If thermal actuation using shape memory alloys is used for catheter steering, then large deformations can be achieved in small sizes, but response time increases and tissue heating safety risks occur
Solution Approach 1:
The patent replaces thermal actuation mechanisms with magnetic actuation using microcoils. Instead of using shape memory alloys that require thermal energy input and exhibit slow nonlinear response, the invention employs microcoils that respond instantaneously to electrical currents through electromagnetic forces, achieving both rapid response and precise control
Solution Approach 2:
The patent changes the actuation parameter from thermal energy to electrical energy. By applying electrical currents to microcoils, the system achieves instantaneous actuation without the delayed thermal response characteristics of shape memory alloys, while also avoiding tissue heating risks associated with thermal actuation
2Speed
If microcoil-based steering is used for MRI-driven actuation, then precise steering and fast response are achieved, but Joule heating effects occur
Solution Approach 1:
The patent employs pulsed or intermittent activation of microcoils rather than continuous operation. By activating coils only when steering corrections are needed and allowing rest periods, the system achieves precise steering control while minimizing cumulative Joule heating effects on surrounding tissue
Solution Approach 2:
The patent introduces active cooling mechanisms as an intermediary system to manage Joule heating. Cooling fluids or heat dissipation structures are integrated with the microcoil assembly to actively remove heat during operation, enabling sustained precise steering without excessive temperature rise
3Force
If hydraulic actuation is used to transmit large forces through the catheter, then force transmission is improved, but radial expansion and buckling cause stiffness variability and fatigue
Solution Approach 1:
The patent replaces hydraulic actuation with magnetic actuation using microcoils. Instead of using fluid pressure that causes radial expansion and buckling of the catheter body, the invention employs electromagnetic forces that act directly on the catheter structure without introducing pressure-related instability or fatigue
Solution Approach 2:
The patent utilizes the catheter's flexible structure in conjunction with magnetic actuation. The flexible catheter body maintains its structural integrity under magnetic forces without the pressure-induced deformation that occurs with hydraulic actuation, preserving both flexibility for navigation and stiffness for force transmission
4Ease of operation
If active catheter design with tendon-based force transmission is used, then maneuverability is improved, but torque transmission loss occurs in tortuous vessels
Solution Approach 1:
The patent replaces tendon-based mechanical force transmission with magnetic actuation. Instead of relying on torque transmission through tendons that suffers from friction and elasticity losses in tortuous vessels, the invention uses distributed microcoils along the catheter that generate local magnetic forces, enabling direct actuation at any position along the catheter length
Solution Approach 2:
The patent divides the catheter into multiple segments with individually controllable microcoils. This segmentation allows independent actuation of different catheter sections, providing precise maneuverability while eliminating the cumulative torque loss that occurs in continuous tendon-based systems navigating tortuous vessels
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise and safe navigation in narrow vasculature with reduced device diameter and minimized heating risks, offering improved maneuverability and reduced bulkiness, while maintaining high force output and scalability.
Implementation Method 1
MRI-driven actuation offers significant advantages over the aforementioned techniques... MRI-driven (magnetic) actuation
Implementation Method 2
determining a torque that needs to be applied onto the medical device such that the medical device carries out the movement
Implementation Method 3
The medical device comprises a set of coils... determining a minimum current that needs to be supplied to each coil of the set of coils
Implementation Method 4
microcoil-based Joule heating effects have been a major design concern
Data Source
AI summary
A method for controlling a movement of a medical device in a magnetic field, the medical device having a set of coils includes determining a torque that needs to be applied onto the medical device such that the medical device carries out the movement, determining a minimum current that needs to be supplied to each coil of the set of coils, respectively, to reach the determined torque by solving an optimization problem, and supplying the determined minimum current to each coil of the set of coils, respectively, such that the medical device carries out the movement.