MRI Device Tracking via Laser-Modulated Magnetic Susceptibility Markers
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Solution Overview
Problem
Current methods for tracking interventional devices during MRI procedures are limited by the difficulty in locating devices outside of known tomographic slices, as magnetic markers cause signal losses and are difficult to distinguish from background signals, leading to time-consuming and inefficient tracking.
Innovation Solution
A tracking device incorporating a magnetic material with an optical source and optical fiber, where laser-induced demagnetization creates variable susceptibility effects, allowing for digital signal processing to separate marker signals from background, enabling rapid and robust position measurement in volumetric coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic markers are used to make devices conspicuous in MRI images, then the device becomes visible in tomographic slices, but it becomes difficult and time-consuming to locate the device when the containing slice is unknown
Solution Approach 1:
The patent applies periodic action by using pulsed laser illumination to modulate the magnetic susceptibility of the marker at a specific frequency. This creates time-varying susceptibility changes that can be detected through frequency-domain filtering, enabling the marker to be distinguished from static background signals and allowing rapid localization without time-consuming manual search through multiple slices
Solution Approach 2:
The patent changes the magnetic susceptibility parameter of the marker dynamically by using laser-induced heating to alter the magnetization state of ferromagnetic materials. This parameter modulation creates detectable signal variations in MRI that enable rapid device localization across volumetric coverage, resolving the time loss issue
2Measurement precision
If ferromagnetic materials are used as markers to generate contrast in MR images, then signal losses are produced in the marker vicinity, but the markers are difficult to distinguish from background signals
Solution Approach 1:
By illuminating the ferromagnetic marker with pulsed laser light at a modulated frequency, the marker's magnetic susceptibility varies periodically. This creates a time-varying signal signature that can be extracted from background noise through frequency-domain filtering and correlation techniques, making the marker easily distinguishable from static background signals
Solution Approach 2:
The system uses feedback by comparing the detected MRI signal with the known laser modulation pattern through cross-correlation or frequency-domain filtering. This feedback mechanism enhances the detectability of the marker signal by selectively amplifying signals that match the expected modulation pattern while suppressing background noise
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
Enables precise and efficient tracking of interventional devices by generating transient susceptibility changes that can be imaged with MRI, allowing for projection-mode coverage and rapid device position measurement, reducing the time and effort required to locate the device within large volumes.
Implementation Method 1
Light generated by the optical source is communicated to the marker via the optical fiber to alter a magnetic susceptibility of the magnetic material in the marker
Implementation Method 2
Differences in volume susceptibility values with their surrounding will cause field inhomogeneities which results in signal losses in their vicinity
Data Source
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AI summary
Described here are systems and methods for using a laser-induced demagnetization of magnetic particles disbursed in a tracking marker to generate variable susceptibility effects that can be imaged with magnetic resonance imaging ("MRI"). As one example, laser power is delivered to nickel particles using fiber optics. This demagnetization effect can be used in rapid tracking of interventional devices by subtracting the two images acquired when the laser is off and on.