Absorption Material Reduces RF Heating in External Fixation Devices
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems cause heating effects in patients with metallic medical devices due to strong radio frequency (RF) fields, leading to potential tissue damage, as the metallic parts interact with the electromagnetic field and concentrate energy inside the body, causing high local temperature increases.
Innovation Solution
The use of an absorption material with specific conductivity and permittivity between the bars and clamps or pins of external fixation devices to redistribute the electric field and reduce RF-induced heating, optimized using Response Surface Methodology for maximum effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electrical insulated layer material is used to reduce RF heating, then heating distribution is modified, but the capability for RF heat reduction is limited at high frequencies above 64 MHz
Solution Approach 1:
The patent changes the electrical parameters of the material by using absorption material with specific conductivity (10^-4 to 10^3 S/m) and permittivity (1 to 10^10 epsr) values optimized for high frequencies above 64 MHz, transforming the material's electromagnetic properties to effectively reduce RF heating where traditional insulators fail
Solution Approach 2:
The patent employs composite absorption material that combines specific conductivity and permittivity properties to create a material that can effectively absorb and dissipate RF energy at high frequencies, overcoming the limitations of simple electrical insulator materials
2Strength
If metallic parts of external fixation devices are used to maintain mechanical strength, then structural integrity is maintained, but localized energy deposition and high local temperature increase occur during MRI scanning
Solution Approach 1:
The patent introduces absorption material as an intermediary component between the metallic parts (bars and clamps) and the pins, which acts as a mediator to absorb and dissipate electromagnetic energy before it can be deposited in localized tissue areas, thereby reducing temperature increase while maintaining the structural integrity of the metallic framework
3Device complexity
If only a small portion of metallic components are inside the human body, then device structure is simplified, but highly condensed electromagnetic energy can only be dissipated in a limited volume of tissue, resulting in very high increase in local temperature
Solution Approach 1:
The patent addresses the limited volume for energy dissipation by extending the absorption material beyond the immediate tissue interface to cover larger areas of the metallic components (bars and pins), effectively distributing the energy dissipation across a larger spatial dimension to reduce peak temperature increases in any single location
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
Significantly reduces RF-induced heating at the tips of external fixation device pins by dissipating energy outside the body, minimizing temperature increases and ensuring safer MRI scans for patients with metallic medical devices.
Implementation Method 1
the absorption material has an electric conductivity between that of a perfect electric conductor and an insulator
Implementation Method 2
the absorption material...dissipating energy outside the body, minimizing temperature increases
Implementation Method 3
The use of an absorption material with specific conductivity and permittivity between the bars and clamps or pins of external fixation devices to redistribute the electric field
Data Source
AI summary
The present invention in general provides methods for reducing RF-induced heating in an external fixation device including at least two bars, at least two clamps and at least two pins; and external fixation devices with significantly lower RF heating at the pins' tips when compared to other external fixation devices.