MRI-Compatible Antenna Segmentation for RF Heating Control
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Solution Overview
Problem
Current interventional MRI devices face challenges in visualizing the distal tip and shaft of catheters during procedures due to poor signal-to-noise ratio and RF-induced heating, which can obscure anatomical images and pose safety risks.
Innovation Solution
The development of medical devices with MRI-compatible circuitry that uses alternating conductive material segments with different geometries and insulating layers to control impedance, minimizing RF-induced heating and enhancing visualization without altering the device's mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RF receiver antennas are used with insulated or bare conductors, then device visualization under MRI is achieved, but fine tuning of characteristic impedance values is not practical and signal profile control is limited
Solution Approach 1:
The antenna conductor is divided into multiple discrete segments along its length, where each segment can have different geometric properties (width, thickness) or material composition. This segmentation enables independent control of characteristic impedance at different locations, allowing precise tuning of the signal profile without complex fabrication processes.
Solution Approach 2:
Different sections of the antenna conductor are designed with locally optimized properties - some segments have wider cross-sections for lower impedance, while others have narrower cross-sections for higher impedance. This local quality variation allows the antenna to achieve desired signal profile control by matching impedance characteristics to specific functional requirements at different antenna locations.
2Measurement precision
If highly conductive antenna components and transmission lines are used for minimal signal loss, then device visualization is improved, but RF induced heating increases and may exceed safety limits
Solution Approach 1:
The characteristic impedance of antenna segments is optimized to match the impedance of surrounding tissues (approximately 50-75 ohms). By changing the geometric parameters (width, thickness) and material properties of conductor segments, the antenna achieves impedance matching that minimizes reflected power and reduces RF induced heating while maintaining adequate signal reception.
Solution Approach 2:
The patent converts the potentially harmful effect of RF induced heating by designing the antenna conductor geometry and material properties to minimize current density concentration. The segmented structure with optimized impedance distribution reduces standing wave formation and hot spots, transforming a safety concern into a design parameter that can be controlled and optimized.
3Measurement precision
If multiple RF receiver antenna components are incorporated for tip and shaft visualization, then complete device visualization is achieved, but overall device profile increases and mechanical performance is adversely affected
Solution Approach 1:
A single antenna component is designed to perform multiple functions: it provides both tip visualization and shaft visualization, and enables both signal reception and impedance matching. By integrating these functions into one component rather than using multiple separate antenna components, the device maintains complete visualization capability while reducing overall profile and preserving mechanical performance.
Solution Approach 2:
The patent combines the functions of multiple antenna components (tip antenna, shaft antenna, transmission lines) into a single integrated antenna structure. The segmented conductor serves as both the radiating element and the transmission line, eliminating the need for separate components and reducing the overall device profile while maintaining complete visualization capability.
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 visualization of both the device tip and shaft during MRI procedures while reducing RF-induced heating, ensuring safer clinical operations and improved anatomical image clarity.
Implementation Method 1
fine tuning of the characteristic impedance values of each antenna components that will affect the receive signal profile
Implementation Method 2
After RF excitation through the RF body coil of MRI scanner, the excited hydrogen protons within the body relax back and emit RF waves. These RF waves can be picked up through RF receiver antennas
Implementation Method 3
minimizing RF-induced heating
Data Source
AI summary
The present disclosure provides medical devices having MRI-compatible circuitry. Preferably, the devices do not project an enlarged profile, yet their position can be determined during an iMRI procedure. Illustrative embodiments of such a device can include a base surface, a first conducting layer disposed on the base surface, a first insulating layer disposed over at least a portion of the first conducting layer, and a second conducting layer disposed over at least a portion of the first insulating layer.