MRI Induced Current Measurement on DBS Leads
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Solution Overview
Problem
Magnetic resonance imaging (MRI) scans induce RF currents on elongated metallic leads, causing heating issues, particularly at complex DBS lead designs with multiple electrodes, where measuring induced currents near electrodes is challenging due to distorted magnetic field distributions and image artifacts.
Innovation Solution
A method involving acquiring data from proximal and distal slices to a conductive object within an MRI scanner, processing images to compute the location of the conductive wire and transmit null point, and estimating the induced current's magnitude and phase, allowing for the generation of an implant-friendly RF excitation that mitigates heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional induced current detection methods are used, then heating prediction is demonstrated for simple conductor geometries, but measurement is not possible close to electrodes for complex DBS lead designs due to image artifacts and distorted magnetic field distributions
Solution Approach 1:
The patent divides the measurement process into two distinct segments: (1) acquiring data from a first slice proximal to the electrode that contains the conductive wire, and (2) acquiring data from a second slice distal to the electrode that does not contain the electrode. This segmentation allows measurement near the electrode by using the proximal slice while avoiding the distal slice's artifacts, thereby resolving the measurement difficulty near electrodes while maintaining measurement precision
Solution Approach 2:
The patent uses the proximal slice data as an intermediary to indirectly measure the induced current near the electrode. Instead of directly measuring in the distorted field near the electrode (which causes artifacts), the method uses the proximal slice that contains the wire but not the electrode itself, serving as a mediator to obtain accurate measurements without direct exposure to the problematic electromagnetic environment
2Productivity
If RF excitation is applied to image complex DBS leads with multiple electrodes, then imaging capability is achieved, but induced currents cause critical temperature increase at lead tips
Solution Approach 1:
The patent performs preliminary measurement of induced currents using the segmented slice acquisition method before conducting the actual imaging scan. By measuring the induced current magnitude and phase in advance using the proximal and distal slice technique, the system can predict heating and adjust imaging parameters or warn of potential overheating, thereby preventing temperature increase while maintaining imaging capability
Solution Approach 2:
The patent establishes a feedback mechanism where induced current measurements from the proximal slice are used to predict heating at the lead tip. This information feeds back into the imaging process to adjust RF excitation parameters or alert operators, allowing the system to maintain imaging productivity while preventing dangerous temperature increases through real-time monitoring and adjustment
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 approach enables accurate measurement of induced currents and reduces heating in electrical leads and electrodes, improving patient safety and image quality during MRI scans.
Implementation Method 1
Magnetic resonance imaging ('MRI') scans induce RF currents on elongated metallic leads
Implementation Method 2
These induced currents may critically increase the temperature at the lead tip
Data Source
AI summary
Systems and method for measuring and mitigating radio frequency (“RF”) induced currents on electrical leads, electrodes, and other electrically conductive objects present in the bore of a magnetic resonance imaging (“MRI”) scanner when the MRI scanner is operated to image an object or subject are described. The methods described in the present disclosure can be implemented as a pre-scan procedure to obtain images from which the current induced on the electrical lead can be estimated. This information can then be used to adjust the RF excitation used in a subsequent pulse sequence to mitigate induced currents and reduce heating in the lead. As such, the methods described in the present disclosure provide for improved patient safety.