MRI B1 Shimming via Position-Based RF Correction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in accurately correcting non-uniformity of the transmit RF magnetic field (B1) due to varying patient positions, leading to brightness irregularities in MRI images, especially when pre-scanning is not feasible to obtain spatial distribution data.
Innovation Solution
A magnetic resonance imaging apparatus that specifies the position of the imaging target using a first imaging protocol and determines phase and amplitude correction values for the transmit RF wave based on a correspondence table or calculation equation, allowing for accurate B1 shimming without pre-scanning, thereby correcting non-uniformity and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-scanning is performed to obtain spatial distribution of B1 for each patient, then B1 shimming accuracy is improved, but imaging time is extended
Solution Approach 1:
The system performs preliminary action by pre-calculating and storing correspondence tables between imaging target positions and optimal B1 correction values before actual imaging. This allows the system to quickly retrieve appropriate correction values based on detected target position without performing time-consuming pre-scanning for each patient, thus maintaining B1 shimming accuracy while reducing imaging time.
2Device complexity
If one type of correction value is used for each imaging target, then device complexity is reduced, but B1 shimming accuracy deteriorates due to position variations
Solution Approach 1:
The system applies local quality by providing different B1 correction values tailored to specific imaging target positions within the bore. Instead of using a single uniform correction value for all positions, the system determines the imaging target's position and selects or calculates appropriate correction values specific to that location, thereby improving B1 shimming accuracy while maintaining manageable system complexity through automated position-based selection.
Solution Approach 2:
The system implements dynamics by making the correction value selection adaptive to the imaging target's position. The processing circuitry dynamically determines the target position and selects corresponding correction values from stored correspondence tables, allowing the system to flexibly adapt to different positions without requiring complex real-time calculations or multiple pre-scanning procedures.
3Manufacturing precision
If B1 correction values are determined based on imaging target position, then brightness irregularity is reduced, but processing complexity increases
Solution Approach 1:
The system performs preliminary action by pre-calculating and storing correspondence tables that map imaging target positions to optimal B1 correction values. During actual imaging, the system simply detects the target position and retrieves the corresponding correction values from pre-stored tables, avoiding complex real-time calculations and reducing processing complexity while maintaining image quality uniformity.
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 precise B1 shimming for imaging targets with high positional flexibility, reducing brightness irregularities and improving image quality without extending the imaging time, thus maintaining examination throughput.
Implementation Method 1
a transmit RF coil 106 and transmit circuitry 107
Implementation Method 2
a static magnetic field magnet 101, a gradient coil 102
Implementation Method 3
determines, in accordance with the specified position, a correction value for a phase and/or a correction value for an amplitude of an RF pulse related to a transmit RF wave, so that non-uniformity in a magnetic field of the transmit RF wave transmitted to the imaging target can be corrected
Data Source
AI summary
According to one embodiment, a magnetic resonance imaging apparatus includes processing circuitry and sequence control circuitry. The processing circuitry specifies a position of an imaging target of a subject in a bore, using an image collected by a first imaging protocol. The processing circuitry determines, in accordance with the specified position, a correction value for a phase of an RF pulse and/or a correction value for an amplitude of the RF pulse, the RF pulse being related to a transmit RF wave, so that non-uniformity in a magnetic field of the transmit RF wave transmitted to the imaging target can be corrected. The sequence control circuitry executes a second imaging protocol for the subject, using the determined correction value.