Modified Surface Layers for MRI Implant Heating Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic Resonance Imaging (MRI)-induced induction heating poses a risk of thermal damage to tissues, particularly for patients with metal implants, as conventional high electrical conductivity metals do not adequately reduce heating, and existing solutions fail to consider the impact of thermophysical and electromagnetic properties beyond electrical conductivity.
Innovation Solution
Development of materials with modified surface layers that incorporate additional metals or metal alloys to create reflective or absorptive surfaces, reducing eddy currents through laser diffusion processes, which enhance reflectivity or absorption of RF magnetic fields, thereby minimizing induction heating. These surfaces are designed to have electrical conductivity levels 2.5% above or below the bulk material's conductivity, and can include thin cladding layers and metamaterial structures to control electromagnetic interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional high electrical conductivity metal materials are used, then the amount of energy introduced into the material via the skin effect is reduced, but MRI-induced induction heating is still too high for certain applications
Solution Approach 1:
The patent applies local quality by creating a surface layer with different electrical conductivity properties than the bulk material. The modified surface layer has electrical conductivity that is 2.5% above or below the bulk material, providing localized electromagnetic property control at the surface where eddy currents are generated, while maintaining the bulk material's mechanical properties.
Solution Approach 2:
The patent employs composite materials by combining a bulk metal material with a modified surface layer that has different electromagnetic properties. This composite structure allows the bulk material to provide mechanical strength while the surface layer controls electromagnetic interactions, reducing MRI-induced heating through tailored electrical conductivity at the surface.
2Length of stationary object
If the electrical conductivity of the material is increased to reduce skin effect penetration, then the skin depth decreases, but the resulting induction heating may still be too high
Solution Approach 1:
The patent implements local quality by modifying only the surface layer's electrical conductivity while keeping the bulk material unchanged. This localized modification creates a gradient in electrical conductivity properties, with the surface layer having 2.5% above or below bulk conductivity, allowing control of eddy current generation at the surface without altering overall material properties.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the electrical conductivity of the surface layer to be 2.5% above or below the bulk material's conductivity. This parameter adjustment optimizes the balance between reducing eddy current penetration and minimizing induction heating, achieving reduced heating while maintaining adequate electromagnetic shielding.
3Object-generated harmful factors
If the surface is made more reflective to RF magnetic fields, then eddy currents are reduced, but the thermophysical properties (density, specific heat capacity, thermal conductivity) must be maintained for mechanical properties
Solution Approach 1:
The patent applies local quality by confining electromagnetic property modifications to the surface layer while preserving bulk material properties. The surface layer's modified electrical conductivity reduces eddy currents and improves MRI compatibility, while the bulk material maintains the thermophysical properties (density, specific heat capacity, thermal conductivity) necessary for mechanical strength and fatigue resistance.
Solution Approach 2:
The patent employs composite materials structure where a modified surface layer is integrated with the bulk material. This composite approach allows the surface layer to provide reduced eddy current generation through tailored electrical conductivity, while the bulk material provides the thermophysical properties needed for mechanical strength, creating a material that satisfies both electromagnetic and mechanical requirements.
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 modified surface layers effectively reduce MRI-induced induction heating, enhancing MRI compatibility for medical devices and implants by minimizing heat generation and improving visibility in MRI environments, while also being applicable for non-medical applications such as sensors and energy-related devices.
Implementation Method 1
incorporate additional metals or metal alloys to create reflective or absorptive surfaces, reducing eddy currents through laser diffusion processes
Implementation Method 2
A time-varying magnetic field creates an electric field within any electrically conductive material and the electric field, in turn, induces an electric current, referred to as the 'eddy current'
Implementation Method 3
The eddy current can heat up the conductive material by the Joule effect and this process is called induction heating
Implementation Method 4
An electromagnetic wave entering a conducting surface is damped so that the current density is largest near the surface of the conductor and reduces in amplitude by a factor 1/e at a distance δ from the surface given by: δ=[2/(ωμ0σ)]1/2 where ω is the angular frequency of the radiation, and σ is the electrical conductivity of the metal. The distance δ is referred to as the skin depth of the conductor
Data Source
AI summary
A composition of matter includes a substrate material (M) having a bulk portion and an outer surface integrated to the bulk portion. The outer surface includes a modified surface layer. The modified surface layer extends to a depth from the outer surface of at least 1 nm. The modified surface layer includes M and at least one other material (X) which is a metal or metal alloy. The modified surface layer has a 25° C. electrical conductivity which is at least 2.5% above or below a 25° C. electrical conductivity in the bulk portion of M. The composition of matter can be an article that includes a frequency selective surface-based metamaterial, and the plurality of modified surface portions can be a plurality of periodic surface elements that provide a resonant frequency.