Non-Superconducting MRI Magnet B0 Field Correction
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Solution Overview
Problem
MRI systems face challenges with B0 field instability due to environmental changes, gradient performance, and residual magnetization, leading to image degradation and artifacts, particularly in high-resolution imaging and Fast Spin-Echo (FSE) scans.
Innovation Solution
The implementation of non-superconducting electromagnets with pole pieces, using broad band RF excitation pulses, real-time TX frequency adjustments, extra gradient pulses, high current pulses, and echo separation techniques to correct for B0 field instability, residual magnetization, and concomitant fields, enabling improved image resolution and reduced scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high resolution MRI imaging is performed, then image quality is improved, but sensitivity to B0 field instability increases causing image degradation
Solution Approach 1:
The system performs preliminary actions by applying broad band RF excitation pulses with strong selection gradients before main imaging to correct drift of the excitation volume, and by implementing real time TX frequency adjustments during scanning to compensate for B0 field drift, thereby preventing image degradation before it occurs
Solution Approach 2:
The system implements feedback mechanisms by monitoring frequency and phase drift in real time during MRI scanning and dynamically adjusting the TX frequency and phase corrections based on measured deviations, creating a closed-loop control system that maintains image quality despite B0 field instability
2Productivity
If Fast Spin-Echo (FSE) imaging is used to reduce scan time, then productivity is improved, but sensitivity to gradient performance and B0 stability increases causing artifacts
Solution Approach 1:
The system performs preliminary FSE calibration by separating odd and even echoes and calculating their time and phase shifts before main imaging, and applies preliminary corrections for residual magnetization and concomitant fields to prevent artifact formation during fast scanning
Solution Approach 2:
The system implements real-time feedback by continuously monitoring and correcting for phase and frequency drift during FSE scanning, dynamically adjusting gradient pulses and RF frequencies to compensate for instabilities that would otherwise cause artifacts in high-speed imaging
3Device complexity
If non-superconducting electromagnets with pole pieces are used, then device complexity is reduced, but residual magnetization occurs degrading image quality
Solution Approach 1:
The system extracts and corrects residual magnetization effects by applying extra gradient pulses specifically designed to restore magnetization in pole pieces, and by providing high current pulses to the electromagnet to counteract residual magnetization, thereby removing the degrading effect while maintaining the simple non-superconducting magnet design
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 reduces image degradation from B0 field instability, enhances MRI resolution, and minimizes acquisition time, particularly for high-resolution and Fast Spin-Echo imaging, while maintaining image quality and efficiency.
Implementation Method 1
an MRI apparatus comprising a non-superconducting electromagnet and a plurality of pole pieces
Implementation Method 2
applying broad band RF excitation pulses with strong selection gradients
Implementation Method 3
providing a 180 degree refocusing pulse and a gradient pulse
Data Source
AI summary
Means and methods for improving the MRI “image quality in an MRI imaging” apparatus comprising a non-superconducting electromagnet and a plurality of pole pieces are provided. Said means for improving the image quality chosen from the group consisting of (a) means for reducing degradation of MRI image quality due to B0 field instability; (b) means for decreasing or otherwise correcting residual magnetization; (c) means for providing a 3D scout image; and (d) any combination of the above. These means for improving the image quality provides greater resolution of the imaged object relative to an MRI apparatus not containing such means for improving image quality.