RF Filter for MRI-Induced Signal Attenuation in Implantable Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Implantable medical devices, such as pacemakers, malfunction during MRI scans due to induced currents and voltages, which can cause cardiac fibrillation and heating issues, leading to suboptimal treatment for patients with implanted devices.
Innovation Solution
An RF filtering system is integrated into the implantable medical device, utilizing a combination of LC tank and series LC resonant circuits with a feedthrough capacitor to attenuate MRI-induced signals, preventing cardiac tissue stimulation and device malfunction while allowing intended cardiac stimulation signals to pass through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an implantable medical device is implanted in a patient, then the device can monitor and provide cardiac therapy, but the device may malfunction during MRI scanning due to induced currents and voltages
Solution Approach 1:
The patent introduces an RF filter as an intermediary component between the implanted lead and the device internal circuitry. This filter acts as a mediator that blocks harmful MRI-induced RF signals from reaching the device while allowing intended cardiac signals to pass through, thus resolving the contradiction between device reliability and susceptibility to MRI-induced harmful factors
Solution Approach 2:
The patent extracts and removes the harmful RF energy from the signal path by using an RF filter that specifically targets and eliminates MRI-induced frequencies. This extraction of harmful factors allows the device to maintain reliability during MRI scanning without requiring device removal or modification
2Object-affected harmful factors
If RF filtering is added to attenuate MRI-induced signals, then device safety during MRI is improved, but device complexity increases
Solution Approach 1:
The patent employs passive RF filter components (inductors and capacitors) that are relatively simple and cost-effective. These passive components provide effective RF attenuation without requiring complex active filtering systems, thereby minimizing the increase in device complexity while achieving the desired MRI safety
3Object-affected harmful factors
If RF filtering is applied to block MRI signals, then cardiac tissue stimulation is prevented, but intended cardiac pacing signals may be attenuated
Solution Approach 1:
The patent designs the RF filter with specific local characteristics that are tuned to block high-frequency RF signals (64-128 MHz) while preserving lower-frequency cardiac pacing signals. The filter's frequency-selective properties create different 'qualities' for different signal types, allowing harmful RF energy to be blocked while maintaining the fidelity of intended pacing signals
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 RF filtering system effectively reduces MRI-induced currents and voltages, ensuring the implantable medical device operates safely and reliably during MRI scans without interfering with intended cardiac pacing signals, thus enabling MRI compatibility without additional patient restrictions.
Implementation Method 1
utilizing a combination of LC tank and series LC resonant circuits with a feedthrough capacitor to attenuate MRI-induced signals
Implementation Method 2
utilizing a combination of LC tank and series LC resonant circuits with a feedthrough capacitor to attenuate MRI-induced signals
Implementation Method 3
a relatively large current and/or voltage may be generated at an external interface of an implantable medical device as a result of MRI scanning
Data Source
AI summary
A filtering scheme for an implantable medical device mitigates potentially adverse effects that may be caused by MRI-induced signals. In some aspects filtering is provided to attenuate MRI-induced signals on an implanted cardiac lead that is coupled to an implanted device. In some aspects the filter may be configured to complement a capacitor circuit (e.g., a feedthrough capacitor) that reduces the amount of EMI that enters the implanted device via the cardiac lead. In some implementations the filter consists of a LC tank circuit and a series LC circuit, where the LC tank circuit is in series with the cardiac lead and a cardiac stimulation circuit and the series LC circuit is in a shunt configuration across the cardiac stimulation circuit.