MR Control Data Using Estimated Magnetic Field Maps
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Solution Overview
Problem
Magnetic resonance (MR) imaging systems face challenges in maintaining spatially homogeneous B1 field homogeneity, especially with high-field MR apparatuses, due to movement of the examination object during scans, leading to image artifacts and the need for frequent recalibration of RF and gradient pulses.
Innovation Solution
A method for determining control data for MR excitation using input and estimated magnetic field map data, applying a trained or interpolation function to adjust RF and gradient pulses based on potential object locations, allowing for precise control of B1 and B0 fields without the need for continuous recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If magnetic field map data is determined for a specific location, then control data can be optimized for that location, but the control data becomes less effective when the examination object moves to a different location
Solution Approach 1:
The system performs preliminary determination of magnetic field map data for multiple possible locations before the actual MR examination. This allows control data to be pre-optimized for various positions, so when the examination object is placed, the system can quickly select or interpolate the most appropriate control data without needing to recalibrate during the scan, thereby maintaining B1 field homogeneity even if the object moves.
Solution Approach 2:
The system changes the parameter of location by determining magnetic field map data for multiple different locations (not just one fixed location). This creates a set of control data corresponding to different spatial positions, allowing the system to adapt to object movement by selecting or interpolating between these pre-determined parameter sets.
2Reliability
If magnetic field map data is determined for multiple locations, then robustness to object movement improves, but the time and complexity of determining control data increases
Solution Approach 1:
The system performs the time-consuming task of determining magnetic field map data for multiple locations in advance, before the actual examination. This preliminary action transfers the time investment to a preparatory phase, allowing the actual MR scan to proceed quickly without repeated recalibration, thus reducing the time loss during the critical imaging process.
Solution Approach 2:
Instead of directly measuring magnetic field maps for multiple locations during the examination, the system uses interpolation to create estimated magnetic field map data for intermediate locations based on measurements from a limited set of reference locations. This copying approach reduces the number of direct measurements needed while still providing comprehensive coverage.
3Reliability
If magnetic field map data is determined for multiple locations, then robustness to object movement improves, but the complexity of the system increases
Solution Approach 1:
The system uses interpolation algorithms to generate estimated magnetic field map data for locations that were not directly measured. This copying method allows the system to extend the coverage from a limited set of reference locations to multiple possible examination positions without requiring direct measurements at each location, thereby reducing system complexity.
Solution Approach 2:
The system creates a universal set of control data that can be applied to multiple different locations and examination scenarios. By determining magnetic field map data for multiple locations and using interpolation, the system develops a multi-functional control data set that handles various object positions and movements, reducing the need for location-specific customization.
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 robust control of MR excitations across various object locations, reducing image artifacts and optimizing B1 field homogeneity, even with patient movement, thus improving image quality without the necessity of repeated magnetic field map scans.
Implementation Method 1
Thanks to an RF transmit pulse, a magnetic alternating field, known as a B1 field, is generated in a field of view (FOV) or in an examination space
Implementation Method 2
Further, gradient pulses are output with the aid of a gradient coil unit of the MR apparatus. As a result of this, temporary magnetic field gradients are generated in the examination space.
Implementation Method 3
The MR signals are received by the MR apparatus and are used for the reconstruction of MR images
Data Source
AI summary
In a method for control, input magnetic field map data is received. In this case, the input magnetic field map data for at least one magnetic field type in each case describes a magnetic field map for a state that an examination object is in at an initial location in the MR apparatus. In this case, the estimated magnetic field map data for at least one magnetic field type in each case describes at least one magnetic field map for in each case a state that the examination object is in at an alternative location that is different compared to the initial location. Control data is determined by the system control unit, using the estimated magnetic field map data or using the input magnetic field map data and the estimated magnetic field map data. The control data is suitable for controlling the MR apparatus.