MRI Eddy Current Correction Using Position-Specific Parameters
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Solution Overview
Problem
Magnetic resonance imaging (MRI) apparatuses face image degradation due to eddy current magnetic fields, particularly at positions away from the center of the magnetic field, as conventional correction methods using a single eddy current correction parameter for all positions may not adequately address distortions caused by eddy currents with varying time constants.
Innovation Solution
The MRI apparatus stores and applies position-specific eddy current correction parameters for both short and long time constant eddy currents, allowing for customized waveform corrections for each imaging position, thereby improving image quality by addressing distortions at all positions within the imaging range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single eddy current correction parameter is used for all positions, then the device complexity is reduced, but the image quality deteriorates at positions away from the center
Solution Approach 1:
The patent applies local quality by preparing different eddy current correction parameters for different imaging positions. Specifically, first correction parameters are prepared for a first imaging position and second correction parameters for a second imaging position, allowing each position to receive optimized correction tailored to its local characteristics rather than applying a uniform correction across all positions.
Solution Approach 2:
The patent segments the imaging range into multiple positions, each with its own eddy current correction parameters. The correction parameter preparation unit divides the correction task by position, and the image generation unit selectively applies appropriate correction parameters based on the specific imaging position, thereby addressing image degradation locally at each position.
2Ease of operation
If eddy current correction is applied using center-reference parameters, then the correction process is simplified, but image distortion occurs at peripheral positions
Solution Approach 1:
Instead of using center-reference parameters for all positions, the patent prepares correction parameters specific to each imaging position. The correction parameter preparation unit generates position-specific parameters that account for the unique eddy current characteristics at each location, ensuring reliable image stability throughout the entire imaging range rather than just at the center.
3Manufacturing precision
If position-specific correction parameters are prepared for all positions, then image quality is improved, but the device complexity increases
Solution Approach 1:
The patent implements a dynamic correction parameter selection mechanism where the correction parameter preparation unit and image generation unit work together to select and apply appropriate correction parameters based on the specific imaging position. This dynamic approach allows the system to maintain high image quality while managing complexity through automated, position-based parameter selection rather than manual configuration for each position.
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 ensures suitable eddy current corrections for each imaging position, reducing image degradation and maintaining image stability, especially in high-speed pulse sequences, by preparing distinct parameters for short and long time constant eddy currents.
Implementation Method 1
A magnetic resonance imaging apparatus adds positional information to a magnetic resonance signal emitted from a subject by applying a gradient magnetic field thereto
Implementation Method 2
an eddy current appears in conductive components arranged around the gradient coil (e.g., a heat shield for a magnetostatic magnet), and this eddy current generates a magnetic field (hereinafter, 'eddy current magnetic field')
Implementation Method 3
The eddy current magnetic field acts in a direction of suppressing the changes of the gradient magnetic field and deforms the waveform of the gradient magnetic field
Implementation Method 4
eddy current correction has been employed to correct the waveform of the gradient magnetic field
Data Source
AI summary
A magnetic resonance imaging (MRI) apparatus storage unit stores different eddy current correction parameters that respectively correspond to different imaging positions to correct for influence of an eddy current magnetic field. An eddy current correcting unit receives the waveform of the gradient magnetic field calculated in accordance with an imaging condition, performs calculation onto the received waveform using an eddy current correction parameter selected in accordance with an imaging position, and outputs the calculation result as a corrected waveform to a gradient magnetic field power supply.