Segmented Surface Electrodes for MR Imaging Safety
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Solution Overview
Problem
Surface electrodes used for patient monitoring are not designed for use in MR imaging, as they are susceptible to eddy currents and RF pulses, degrading image quality and posing a safety risk, requiring removal before MR procedures, which disrupts the workflow and necessitates re-placement and re-acquisition of impedance maps.
Innovation Solution
The surface electrodes are designed with slits to reduce eddy currents and a quick disconnect coaxial cable system to minimize induced currents, allowing them to remain in place during MR imaging without degrading image quality or posing a burn risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface electrodes are used for patient monitoring during MR imaging, then continuous monitoring is maintained, but eddy currents are induced in the electrodes which degrade image quality and pose safety risks
Solution Approach 1:
The conductive layer of the electrode is divided into multiple separate conductive elements arranged in an array pattern. This segmentation breaks up continuous conductive paths into discrete segments, reducing the magnitude of eddy currents that can be induced in the electrode during MR imaging while maintaining sufficient conductivity for patient monitoring functions
Solution Approach 2:
Different regions of the electrode have different conductive properties - the conductive elements are strategically positioned and sized to provide adequate signal acquisition for monitoring while minimizing eddy current formation. The conductive elements are embedded in a non-conductive substrate material that provides electrical isolation and structural support
2Object-affected harmful factors
If surface electrodes are removed before MR imaging, then image quality is maintained and patient safety is ensured, but workflow is disrupted and additional time is required for re-placement and re-acquisition of impedance maps
Solution Approach 1:
The electrodes are designed with MR-compatible features (segmented conductive elements, non-ferromagnetic materials, minimized wire loops) before the MR procedure begins. This preliminary design allows the electrodes to remain on the patient during imaging without causing harmful effects, eliminating the need for removal and re-application and thus preventing workflow disruption and time loss
3Reliability
If surface electrodes with continuous conductive layers are used, then good electrical contact is maintained for signal acquisition, but the electrodes act as antennas for RF pulses causing induced currents and burn risks
Solution Approach 1:
The continuous conductive layer is segmented into multiple discrete conductive elements arranged in an array. This segmentation reduces the effective antenna length and breaks up current paths, minimizing RF-induced currents and burn risks while maintaining adequate electrical contact for signal acquisition through the distributed array of conductive elements
Solution Approach 2:
The conductive elements are arranged in a two-dimensional array pattern on the electrode surface rather than as a single continuous layer. This dimensional transformation distributes the electrical contact points across the surface area, maintaining overall signal acquisition capability while reducing the antenna effect 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
This design enables safe and efficient MR imaging by reducing eddy currents and eliminating induced current risks, simplifying the workflow and allowing for immediate post-procedure treatment without the need for re-placement of electrodes.
Implementation Method 1
reducing artifacts in the generated image by dividing the layer into separate side by side sections where the separation into the side by side sections is arranged to reduce eddy currents which are induced in the surface electrodes when they are exposed to variations in the magnetic field
Implementation Method 2
generating an RF pulse in the magnetic field to be applied to the patient such that the imaged part of the patient generates an MR signal in response to the magnetic field and the RF pulse applied thereto
Data Source
AI summary
For use in MR imaging of a patient a plurality of surface electrodes such as ECG or defibrillator are provided for obtaining electrical signals for determining electrical activity within the body of the patient and remain in place during the MR imaging. The surface electrodes include a quick disconnect wire for carrying the signals to a signal processing system to be removed during the MR imaging to prevent heating. Each electrode comprises a conductive layer divided by slits into separate side by side sections to reduce eddy currents which are induced in the surface electrodes when they are exposed to variations in the magnetic field. The sections all are connected through the layer to the conductive location to allow the signal therefrom to be connected to the communication conductor.