Conductive Absorption Material for MRI RF Heating Reduction
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Solution Overview
Problem
External fixation devices made of nonmagnetic metal materials experience significant RF-induced heating during MRI scans, leading to potential tissue damage due to localized energy deposition, as existing solutions like electrical insulation layers are insufficient in reducing heating at high operating frequencies.
Innovation Solution
Incorporating an absorption material with electric conductivity greater than 10−4 S/m into the fastening assembly of external fixation devices to dissipate or reduce RF-induced heat, thereby minimizing temperature increases at the insert tips during MRI scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electrical insulation layer material is used to reduce RF heating, then some heat reduction is achieved, but the capability is limited at high operating frequencies (above 64 MHz) where induced current can still couple inside the human body
Solution Approach 1:
The patent changes the electrical conductivity parameter of the absorption material from insulating (low conductivity) to conductive (high conductivity greater than 10^-4 S/m). This parameter change enables the material to effectively couple with and absorb RF electromagnetic fields at high frequencies (above 64 MHz), transforming it from a material that merely insulates to one that actively dissipates RF energy through controlled electrical conduction, thereby achieving reliable heating reduction.
Solution Approach 2:
The patent employs composite material construction by combining conductive absorption material with the external fixation device structure. The conductive material is integrated into or applied on the surface of the device components, creating a composite structure that maintains mechanical strength while adding RF energy dissipation capability, thus achieving both structural integrity and effective RF heating reduction.
2Strength
If nonmagnetic metal materials are used to maintain mechanical strength, then structural integrity is preserved, but significant RF-induced heating occurs during MRI scans due to strong interaction with electromagnetic fields
Solution Approach 1:
The conductive absorption material serves as an intermediary between the nonmagnetic metal structure and the RF electromagnetic field. Instead of the metal directly interacting with and heating from the RF field, the conductive material acts as a mediator that absorbs and dissipates the RF energy, reducing the harmful thermal effects on both the device and surrounding tissue while allowing the nonmagnetic metal to maintain its structural function.
Solution Approach 2:
The patent converts the harmful RF-induced heating effect into a beneficial one by using the conductive absorption material to intentionally absorb and dissipate RF energy. The material transforms the potentially harmful electromagnetic energy interaction into controlled energy dissipation that protects the device and tissue, turning the harmful RF field interaction into a protective mechanism.
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 use of conductive absorption materials effectively reduces RF heating at the insert tips by up to 59.5% compared to devices without such materials, significantly mitigating the risk of tissue damage during MRI procedures.
Implementation Method 1
strong radio frequency (RF) fields generated by MRI systems can cause heating effects when patients are being scanned. This can be a significant issue when patients with metallic medical devices (e.g., external fixation devices) are scanned. Localized energy can be deposited near the tips of these medical devices
Implementation Method 2
the absorption material has an electric conductivity greater than 10−4 S/m. During MRI scanning, a RF heating at the insert, particularly at the portion of the insert that is within the patients tissue/bone, such as a tip of an insert pin, is significantly reduced
Data Source
AI summary
The present invention provides an external fixation device and method thereof. The device includes at least an insert for inserting into a patient's tissue such as a bone. The insert is fastened to a fastening assembly which comprises at least a RF heat source member during MRI scanning of the patient. At least a part of the RF heat source member's surface is covered with an absorption material to reduce the direct or indirect transfer of RF induced heat from the member to the insert. The absorption material has an electric conductivity greater than 10−4 S/m.