MRI Electrode Cable RF Filter Layout to Reduce Skin Heating
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Solution Overview
Problem
Existing neurological monitoring electrode systems face challenges with RF heating and potential burns when used in MRI environments, as they tend to act as antennas for RF energy, leading to resistance heating at the skin-electrode interface.
Innovation Solution
The integration of a combination of inductors and resistors in-line within the electrode system's cable forms a radio frequency filter, which reduces heating and is less frequency-specific than traditional tank filters, minimizing RF power delivery to the patient's skin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If tank filters are used to block RF energy in electrode cables, then RF heating is reduced at specific frequencies, but the filters are frequency-specific and require precise tuning which increases device complexity and manufacturing cost
Solution Approach 1:
The patent changes the electrical parameters of the cable itself by inserting resistors and inductors to modify its RF characteristics. This transforms the cable from an RF antenna to an RF filter, providing broad-spectrum attenuation without frequency-specific tuning. The parameter changes in resistance and inductance create a distributed filtering effect across multiple frequencies.
Solution Approach 2:
The patent extracts the filtering function from separate tank filter components and integrates it directly into the cable structure through inserted resistors and inductors. This eliminates the need for frequency-specific tuning of separate filter modules while maintaining RF heating protection.
2Object-affected harmful factors
If electrodes are removed from patients before MRI procedures to prevent burns, then patient safety is improved, but monitoring capability is lost during the procedure and re-attachment is time-consuming
Solution Approach 1:
The patent converts the harmful RF-heating effect into a beneficial filtering mechanism. The same RF energy that causes heating is used to activate the filtering action of the resistors and inductors inserted in the cable, which dissipate RF energy as heat in the filter components rather than at the skin-electrode interface, allowing electrodes to remain on patients during MRI.
Solution Approach 2:
The patent introduces resistors and inductors as intermediary elements in the electrode cable. These components act as mediators that intercept and dissipate RF energy before it can reach the electrode-skin interface, enabling continuous monitoring during MRI without burn risk.
3Measurement precision
If MRI magnetic field strength and RF frequency are increased to improve image quality, then imaging performance is improved, but RF heating and burn potential increase
Solution Approach 1:
The patent applies preliminary anti-action by pre-installing resistors and inductors in the electrode cables before MRI procedures. These components are positioned to counteract RF heating effects before they can occur, creating a protective barrier against the increased RF energy used in high-field MRI imaging.
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
This solution effectively minimizes RF power delivery to the patient's skin across a broad range of radio frequencies, reducing the risk of burns and allowing for safer neurological monitoring during MRI procedures without the need for precise tuning or costly components.
Implementation Method 1
The RF energy in the cable heats the cable and any electrically resistive material connected to it. If the cable is connected to an electrode attached to the skin of the patient, resistance heating at the skin-electrode interface may result in a burn injury.
Implementation Method 2
If the cable is in the presence of a magnetic field oscillating at a radio frequency (RF), such as that generated by a Magnetic Resonance Imaging (MRI) machine, the cable tends to act as an antenna and conducts the radio frequency (RF) energy.
Data Source
AI summary
An electrode system includes an electrode, a connector, and a cable with an in-line radio-frequency filter module comprising resistors and inductors without any deliberately added capacitance. The resistors are arranged in an alternating series of resistors and inductors, preferably with resistors at both outer ends, and connected electrically in series. The in-line module is located at a specific location along the wire, chosen through computer modeling and real-world testing for minimum transfer of received RF energy to a patient's skin, such as between 100 cm and 150 cm from the electrode end of a 240 centimeter cable. The total resistance of the resistors plus cable, connectors and solder is 1000 ohms or less; while the total inductance is roughly 1560 nanohenries. The inductors do not include ferrite or other magnetic material and are, together with the resistors, stock components thereby simplifying manufacture and reducing cost.