MRI Secondary Error Magnetic Field Compensation via Preliminary Measurement
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Solution Overview
Problem
Conventional MRI techniques struggle to sufficiently compensate for secondary error magnetic fields generated by compensation currents, leading to image quality degradation and artifacts in magnetic resonance imaging.
Innovation Solution
The MRI apparatus measures and analyzes secondary error magnetic fields, calculates compensation parameters, and applies a correction magnetic field to the gradient and correction coils to effectively cancel out these errors, thereby enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If compensation current is applied to cancel the primary error magnetic field, then the primary error magnetic field is reduced, but a secondary error magnetic field is generated that cannot be sufficiently compensated
Solution Approach 1:
The patent measures and analyzes the secondary error magnetic field in advance before actual imaging, calculates compensation parameters based on these measurements, and saves them for later use. This preliminary characterization of the secondary error field enables proactive compensation rather than reactive correction.
Solution Approach 2:
The patent uses measured secondary error magnetic field data to calculate compensation parameters that are then applied to generate correction magnetic fields. This creates a feedback loop where measurement results directly inform compensation actions, enabling continuous improvement of image quality.
2Object-affected harmful factors
If additional current is superimposed to cancel eddy current in shim coils, then eddy current effects are reduced, but secondary error magnetic field is generated
Solution Approach 1:
The patent measures the secondary error magnetic field caused by compensation current in advance, characterizes its properties, and calculates appropriate compensation parameters before actual imaging begins. This preliminary measurement approach allows the system to anticipate and prepare for secondary error field compensation.
Solution Approach 2:
The measured secondary error magnetic field information feeds into the compensation parameter calculation, which then generates appropriate correction currents. This feedback mechanism ensures that compensation strategies are based on actual measured effects rather than theoretical estimates.
3Measurement precision
If conventional compensation techniques are used, then primary error magnetic field is compensated, but image quality degradation occurs due to insufficient secondary error field compensation
Solution Approach 1:
The patent performs preliminary measurement and analysis of secondary error magnetic fields before actual imaging, calculating compensation parameters in advance. This preparatory step ensures that both primary and secondary error fields are accounted for before image acquisition begins.
Solution Approach 2:
The system uses measured secondary error field data to adjust compensation parameters, creating a feedback mechanism that improves overall compensation accuracy and reliability for maintaining image quality.
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 prevents image degradation by accurately compensating for secondary error magnetic fields, resulting in improved MRI image quality with reduced artifacts.
Implementation Method 1
Since the gradient magnetic field is applied as a pulse, eddy currents are induced at the rise and fall of the gradient magnetic field (when the magnetic field changes) in conductive structures disposed near a gradient magnetic field coil. This eddy current creates a new magnetic field.
Implementation Method 2
outputting, to the gradient magnetic field coil, compensation current that cancels the error magnetic field
Implementation Method 3
such high magnetic field uniformity is achieved by constantly supplying shim current to a shim coil (correction coil) to generate a correction magnetic field
Implementation Method 4
a static magnetic field magnet that generates a static magnetic field
Data Source
AI summary
Provided are MRI images with excellent image quality and in which the occurrence of artifacts is suppressed by effectively removing a secondary error magnetic field, generated by compensation current (additional current), of eddy current that is caused by applying a gradient magnetic field. The present invention measures and analyzes, in advance, a secondary error magnetic field generated due to the applying of compensation current and saves the results as compensation parameters (secondary compensation parameters), uses the secondary compensation parameters to calculate a correction magnetic field output to be applied to each of a gradient magnetic field coil and a correction coil, and supplies this correction magnetic field output to the gradient magnetic field coil and the correction coil to compensate for (cancel out) the secondary error magnetic field.