MRI Neurological Cable RF Filter Layout to Reduce Skin Heating
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Solution Overview
Problem
Existing neurological electrode systems face challenges in minimizing radio frequency (RF) heating during Magnetic Resonance Imaging (MRI) procedures, which can lead to burns and require time-consuming electrode attachment and detachment.
Innovation Solution
The integration of a combination of inductors and resistors in-line within the electrode system's cable forms a radio frequency filter, reducing heating and minimizing frequency specificity, thus avoiding the need for precise tuning and costly tank filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If tank filters are used to block RF energy in electrode cables, then heating is reduced at specific frequencies, but the device becomes frequency-specific and requires precise tuning
Solution Approach 1:
The patent changes the filtering mechanism from frequency-specific tank filters to a broadband approach using ferrite beads and resistors. The ferrite material properties are utilized to create frequency-independent attenuation across the entire RF spectrum, eliminating the need for precise frequency tuning while maintaining heating reduction effectiveness.
Solution Approach 2:
The patent replaces expensive, complex tank filters requiring precise tuning with simpler, cheaper components like ferrite beads and resistors that provide broadband filtering without frequency-specific adjustments. This simplifies the device and reduces manufacturing costs.
2Object-affected harmful factors
If electrodes are removed from patients prior to MRI procedures to avoid burns, then patient safety is improved, but the procedure becomes time-consuming and expensive
Solution Approach 1:
The patent incorporates RF filtering components (ferrite beads and resistors) into the electrode cable assembly before the MRI procedure. This preliminary integration of protective measures allows electrodes to remain on patients during MRI without causing burns, eliminating the need for time-consuming removal and reattachment procedures.
Solution Approach 2:
The patent introduces ferrite beads and resistors as intermediary elements in the cable that block RF energy from reaching the electrode-skin interface. This intermediary filtering allows continuous monitoring during MRI by preventing the harmful RF heating that would otherwise require electrode removal.
3Measurement precision
If stronger magnetic fields and higher radio frequencies are used in MRI machines, then image quality is improved, but resistance heating and potential for burns increases
Solution Approach 1:
The patent converts the harmful RF energy that causes heating into a controlled filtering process. By using ferrite beads and resistors, the RF energy is dissipated safely through controlled resistance rather than causing uncontrolled heating at the electrode-skin interface, allowing high-field MRI to proceed safely.
Solution Approach 2:
The patent changes the electrical parameters of the cable system by introducing ferrite beads and resistors that alter the impedance and attenuate RF signals. This parameter modification reduces the RF energy reaching the electrode without affecting the MRI's magnetic field strength or imaging capabilities.
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 reduces RF power delivery to the patient's skin, minimizing the risk of burns and allowing for continuous neurological monitoring during MRI procedures, while being cost-effective and tolerant of various radio frequencies.
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.
Implementation Method 3
the risk of magnetic saturation altering the properties of ferrites in strong magnetic fields
Implementation Method 4
all module materials and filter components are chosen to contain either no magnetic material at all, or at least the minimum feasible quantity of such material including nickel plating, thus minimizing the risk of dangerous attraction in very strong magnetic fields
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 1OO 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.