B1 Field Mapping via Linear Projections in MRI
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Solution Overview
Problem
Current B1 field mapping techniques in MRI are time-consuming and often compromise on resolution or introduce noise, and require imaging the entire volume of interest for accurate shimming.
Innovation Solution
A method and apparatus for B1 field mapping that involves transmitting gradient and RF pulse sequences to excite linear projections, acquiring one-dimensional spatial encoding signals, and generating a B1 field map based on these signals, allowing for efficient mapping without imaging the entire volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If known B1 field mapping techniques are used to image the complete volume of interest, then accurate B1 field shimming is achieved, but the mapping time is excessively long
Solution Approach 1:
The patent divides the three-dimensional volume of interest into multiple two-dimensional slices. Each slice is imaged separately using 2D projection reconstruction techniques, allowing parallel processing and significantly reducing the total mapping time compared to acquiring the entire volume sequentially.
Solution Approach 2:
The patent transforms the 3D volume imaging problem into multiple 2D slice imaging problems. By using 2D projection reconstruction and combining slices along the frequency-encode direction, the system achieves efficient B1 field mapping with reduced acquisition time while maintaining accuracy.
2Loss of time
If proprietary high speed B1 field mapping techniques are used to reduce shimming time, then mapping time is reduced, but resolution deteriorates and noise increases
Solution Approach 1:
The patent replaces traditional 3D imaging methods with 2D projection reconstruction techniques. This substitution allows for faster acquisition by imaging slices in parallel while maintaining high resolution through proper reconstruction algorithms, avoiding the resolution loss and noise increase associated with proprietary high-speed methods.
Solution Approach 2:
The patent changes the imaging parameters by using 2D projection reconstruction instead of conventional 3D imaging. By adjusting the number of projections, slice thickness, and reconstruction methods, the system achieves optimal balance between mapping speed, resolution, and noise characteristics.
3Measurement precision
If iterative shimming techniques are used to achieve B0 field homogeneity, then field homogeneity is improved, but the process becomes time-consuming
Solution Approach 1:
The patent performs B0 field shimming before B1 field mapping using the fast 2D projection reconstruction technique. By achieving B0 homogeneity first with a rapid method, the system eliminates the need for time-consuming iterative shimming during the B1 mapping process, thereby reducing total acquisition time while maintaining field homogeneity.
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 significantly reduces the time required for B1 shimming while maintaining high resolution and reducing noise, by focusing on linear projections rather than the entire volume of interest.
Implementation Method 1
MRI functions on the principle of nuclear magnetic resonance (NMR) of atoms of certain elements
Implementation Method 2
An MRI system uses a powerful magnetic field (also known as B0 field) to align the magnetization of some atoms in the body
Implementation Method 3
radio frequency fields (also known as B1 field) to systematically alter the alignment of this magnetization
Implementation Method 4
the resonance frequency of the nuclei of particular atoms is directly proportional to the strength of the applied magnetic field
Data Source
AI summary
A method of B1 field mapping relating to Magnetic resonance imaging (MRI) is given. In the method, RF and gradients are applied to excite and select a linear projection through a volume of interest; a radio frequency pulse sequence is transmitted to impart B1 dependent phase to the linear projection, following which a one dimensional spatial encoding signal is acquired along the linear projection; Subsequently a B1 field map based on the one dimensional spatial encoding signal is reconstructed.