MRI Tracking Marker Design for Artifact-Free Robotic Guidance
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Solution Overview
Problem
Current MRI-guided robotic systems face challenges in device localization and image quality due to the use of ferromagnetic materials, which cause artifacts, and struggle with accurate tracking of multiple wireless fiducial markers with dynamic geometrical layouts, particularly in flexible or non-rigid devices like catheters.
Innovation Solution
A wireless tracking marker with a multilayer planar spiral inductor design that enhances inductance and sensitivity, combined with a 3D shape sensor like a FBG optic fiber for determining marker positions, allowing for accurate correspondence and real-time tracking of multiple markers with varying geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ferromagnetic materials are used in MRI-guided robotic devices, then device strength and structural integrity are improved, but image quality deteriorates due to artifacts
Solution Approach 1:
The patent removes ferromagnetic materials from the device design entirely, extracting the problematic component that causes artifacts. The device is reconfigured to use non-ferromagnetic materials (titanium, stainless steel, nickel-titanium alloys) while maintaining structural integrity through alternative design approaches, thereby eliminating image degradation without sacrificing device strength.
Solution Approach 2:
The patent changes the material composition parameters of the device, transitioning from ferromagnetic to non-ferromagnetic materials. This parameter change fundamentally alters the device's magnetic properties, making it MRI-compatible and eliminating artifact generation while preserving mechanical strength through carefully selected alternative materials and structural designs.
2Measurement precision
If multiple wireless fiducial markers are used for tracking, then tracking coverage is improved, but correspondence between marker signals and positions becomes difficult to determine
Solution Approach 1:
The patent segments the tracking system into distinct functional components: rigid body markers with fixed geometric relationships and flexible catheters with embedded shape sensors. This segmentation allows independent handling of correspondence determination for each component type, simplifying the overall system while maintaining comprehensive tracking coverage.
Solution Approach 2:
The patent introduces shape sensors (FBG optic fibers) as intermediary elements that directly measure catheter geometry and position. These sensors act as mediators between the catheter structure and the tracking system, providing direct geometric data that eliminates the correspondence problem by establishing a known relationship between sensor signals and catheter positions.
3Ease of operation
If flexible devices like catheters are tracked, then patient accessibility is improved, but tracking accuracy deteriorates due to dynamic geometrical layout
Solution Approach 1:
The patent embraces the dynamic nature of flexible devices by integrating shape sensors that continuously measure changing geometries. Rather than attempting to maintain a fixed marker layout, the system dynamically tracks the catheter's evolving shape and position, allowing accurate tracking throughout the full range of motion and deployment configurations.
Solution Approach 2:
The patent replaces traditional mechanical fiducial markers with electromagnetic field-based tracking and optical fiber sensing. This substitution eliminates the mechanical constraints of fixed marker geometries, allowing the system to accurately track flexible devices as they deform and move without requiring rigid structural support for the markers themselves.
4Speed
If active coil tracking with conductive wires is used, then localization speed is improved, but RF-induced heating occurs that may damage the device or harm the patient
Solution Approach 1:
The patent extracts and removes the conductive wiring from the active coil tracking system, eliminating the RF antenna that causes heating. Instead, the system uses wireless inductive coupling through tuned fiducial markers and optical fiber sensing, which do not conduct RF currents and therefore do not generate harmful heating effects while maintaining tracking functionality.
Solution Approach 2:
The patent substitutes electrical conduction-based tracking with electromagnetic induction and optical sensing. By replacing conductive wires with non-conductive optical fibers and using inductive coupling for wireless markers, the system eliminates RF current flow through the device, thereby preventing Joule heating while preserving real-time tracking capabilities.
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
The multilayer planar spiral inductor design provides a compact, high-sensitivity tracking solution that overcomes the limitations of single-layer markers, enabling precise tracking of flexible devices and reducing RF-induced heating, while the 3D shape sensor ensures accurate correspondence between marker signals and positions, improving tracking accuracy and safety within MRI environments.
Implementation Method 1
A wireless tracking marker with a multilayer planar spiral inductor design that enhances inductance and sensitivity
Implementation Method 2
3D shape sensor like a FBG optic fiber for determining marker positions
Implementation Method 3
Magnetic resonance imaging (MRI) guided intervention
Data Source
AI summary
An MR marker (501, 601, 803, 902) for magnetic resonance imaging (MRI) guided intervention and method of fabricating same. The tracking device can be integrated with an MRI-guided robotic system to provide precise positional tracking of the interventional tools and robotic components, allowing safe operation inside the human body. The MR tracking device includes a plurality of stacked flexible printed circuit boards; a plurality of flat planar spirals comprised of a non-ferromagnetic material and directly disposed on a top surface and a bottom surface side of each flexible printed circuit board, a biocompatible, non-ferromagnetic material encapsulating the flexible printed circuit boards; and an adhesive bonding the flexible printed circuit boards. In another aspect, an orientation-independent device is provided including three or more markers (501, 601, 803, 902) in an array around a cylindrical substrate.