MRI Ferromagnetic Particle Positioning via Multi-Projection Sequences
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Solution Overview
Problem
Current MRI methods face challenges in precisely and efficiently determining the position of ferromagnetic particles, especially in liquid matrices, due to significant interference fields and signal distortions, which can lead to inaccurate or time-consuming location determination and potential particle migration during measurement.
Innovation Solution
The method involves recording at least two one-dimensional projections per spatial direction with a preselected parameter change, such as echo time or read gradient amplitude, to localize ferromagnetic particles based on field disturbances caused by the particles, allowing for quick and precise position determination without high pulse power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI measurement sequences are used to determine particle position, then measurement precision is degraded due to interference fields and signal distortions, but measurement time increases and particle migration risk increases
Solution Approach 1:
The measurement sequence is divided into multiple individual measurements with relaxation periods in between, allowing the particle position to be determined through sequential data points rather than requiring a single long measurement, thus reducing particle migration during measurement while maintaining precision
Solution Approach 2:
The measurement sequence applies periodic RF excitations and gradient switching at specific timings, creating periodic signal patterns that encode particle position information in the signal phase and amplitude, enabling precise localization through signal analysis rather than prolonged imaging
2Measurement precision
If measurement time is extended to improve position determination accuracy, then measurement precision improves, but particle migration increases and measurement reliability decreases
Solution Approach 1:
The measurement sequence is designed to acquire sufficient position information within a short time frame before particle migration significantly affects position, using optimized RF excitation timing and gradient switching to extract maximum positional accuracy from brief measurement windows
Solution Approach 2:
The system analyzes the MRI signal characteristics (phase shifts, amplitude modulations) to determine particle position, using this information to guide subsequent measurements or corrections, ensuring reliable position tracking even with brief measurement intervals
3Measurement precision
If high pulse power is applied to improve signal quality for particle detection, then measurement precision improves, but device complexity and energy consumption increase
Solution Approach 1:
Instead of applying high pulse power throughout the entire measurement sequence, the method uses optimized, moderate-power RF excitations applied selectively at specific timings when they provide maximum positional information, reducing overall energy consumption while maintaining detection precision
Solution Approach 2:
The measurement sequence varies RF excitation parameters (amplitude, duration, timing) and gradient parameters dynamically throughout the sequence, optimizing signal-to-noise ratio for particle detection at each measurement point without requiring consistently high power levels, thus simplifying device requirements
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 reliable and rapid localization of ferromagnetic particles with minimal technical effort, maintaining the field of view and reducing particle migration risks, even in complex environments like biological tissues.
Implementation Method 1
Ferromagnetic particles within a magnetic field generate significant interference fields whose extent exceeds the size of the particle many times
Implementation Method 2
it is possible to exert a force on them externally using a magnetic field gradient
Data Source
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AI summary
A method for determining the position of at least one ferromagnetic particle in an object or a liquid matrix using an MRI system (50), wherein an MRI measurement sequence is applied to a measurement volume (52) in which the particle is located, is characterized in that at least two projections per spatial direction are acquired, wherein a read gradient is switched for acquiring each one-dimensional projection, wherein a preselected parameter is changed for each of the two projections, and wherein the spatial position of the ferromagnetic particle is determined using the two projections. This enables a more reliable and precise determination of the position of a ferromagnetic particle or a bundle of ferromagnetic particles in a liquid matrix, whereby this position determination can be carried out in a very short time and requires only an extremely low pulse power.