Dynamic Shimming for MRI Magnetic Field Uniformity
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Solution Overview
Problem
The uniformity of the static magnetic field in MRI apparatuses can deteriorate due to object movement during imaging scans, leading to a decrease in MR image quality.
Innovation Solution
The MRI apparatus incorporates processing circuitry that acquires shimming data to correct static magnetic field non-uniformity, controls the shim coil current based on this data, and reacquires shimming data during scans if necessary to maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If active shimming is performed to enhance static magnetic field uniformity, then image quality is improved, but the system cannot adapt to object movement during scanning
Solution Approach 1:
The patent implements dynamic shimming by continuously or periodically reacquiring shimming data during the imaging scan and updating shim coil currents in real-time. This transforms the static shimming process into a dynamic one that adapts to object movement, maintaining magnetic field uniformity throughout the scan duration.
Solution Approach 2:
The system establishes a feedback loop where shimming data is acquired, shim coil currents are adjusted, and the resulting magnetic field uniformity is monitored. Based on this feedback, the system determines whether to reacquire shimming data during the scan, creating a closed-loop control system that maintains optimal performance despite object movement.
2Manufacturing precision
If shimming data is reacquired during imaging scan, then magnetic field uniformity is maintained, but scanning time increases
Solution Approach 1:
Instead of continuous reacquisition, the system employs periodic shimming where shimming data is reacquired at predetermined intervals or under specific conditions during the imaging scan. This periodic approach maintains magnetic field uniformity while minimizing the time penalty compared to continuous reacquisition.
Solution Approach 2:
The system reacquires shimming data selectively based on predetermined conditions rather than at every possible moment. This partial action approach reacquires data only when necessary to maintain image quality, avoiding unnecessary time consumption while still preventing quality deterioration.
3Reliability
If shim coil current is continuously adjusted, then image quality is maintained, but system complexity increases
Solution Approach 1:
The system performs self-diagnosis by evaluating whether magnetic field uniformity has deteriorated based on acquired shimming data. The processing circuitry autonomously determines whether reacquisition is necessary and executes the appropriate control actions without requiring external intervention, simplifying the overall control architecture while maintaining reliability.
Solution Approach 2:
The feedback mechanism enables the system to monitor magnetic field uniformity and automatically trigger shim coil current adjustments only when deterioration is detected. This conditional feedback approach maintains image quality consistency while avoiding unnecessary control operations that would increase system complexity.
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 solution effectively suppresses the deterioration of MR image quality by continuously adjusting the static magnetic field uniformity, even during object movement, thereby ensuring consistent image quality.
Implementation Method 1
a shim coil configured to enhance uniformity of the static magnetic field
Implementation Method 2
controls an electric current value of the shim coil
Implementation Method 3
acquire MR image generation data by performing an imaging scan that acquires magnetic resonance signals
Data Source
AI summary
In one embodiment, an MRI apparatus comprising: a static magnetic field magnet configured to generate a static magnetic field; a shim coil configured to enhance uniformity of the static magnetic field; and processing circuitry configured to acquire shimming data for correcting static magnetic field non-uniformity, control an electric current value of the shim coil by using the shimming data, acquire MR image generation data by performing an imaging scan that acquires magnetic resonance signals for generating an image of the object, determine whether to reacquire the shimming data during the imaging scan or not, based on the MR image generation data, and reacquire the shimming data during the imaging scan if reacquisition is determined, and control the electric current value of the shim coil during the imaging scan based on reacquired shimming data.