B0 Field Map Estimation from Single Echo MRI Phase Data
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Solution Overview
Problem
Magnetic resonance imaging (MRI) is hindered by artifacts caused by B0 field inhomogeneities, which worsen with longer echo times, leading to distorted and blurred images, and existing correction methods require additional scans, increasing examination time and error susceptibility.
Innovation Solution
A method that estimates B0 field inhomogeneity using a single high-resolution acquisition, applying transforms and operations like virtual coil combination, sum of squares, and low-pass filtering to generate a B0 field map, thereby correcting MR images without additional scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a B0 field map is acquired in addition to patient images, then artifact correction performance is improved, but examination time increases
Solution Approach 1:
The patent combines the B0 field map acquisition with the patient image acquisition into a single scan by using the same k-space data. The field map is derived from the phase information of the complex MR data after image reconstruction, eliminating the need for a separate field map scan while maintaining correction performance
Solution Approach 2:
The patent makes the patient image acquisition serve dual purposes: both diagnostic imaging and B0 field mapping. The same MR data is used for both image reconstruction and field map estimation, making the system multi-functional and eliminating redundant scanning
2Productivity
If the scan resolution is reduced to shorten examination time, then acquisition time is decreased, but B0 field map quality deteriorates
Solution Approach 1:
The patent extracts the B0 field map information from the phase component of the complex MR data after standard image reconstruction. By separating the field map derivation as a post-processing step from the imaging acquisition, the full resolution data is preserved for both purposes without compromising either speed or quality
3Measurement precision
If multiple full scans are performed for B0 field mapping, then field map accuracy is improved, but error susceptibility increases
Solution Approach 1:
The patent merges the field map acquisition with the patient scan, ensuring both are obtained from the exact same data acquisition. This eliminates inter-scan variability and motion-related errors that would arise from performing separate scans at different times
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 examination time, enhances image quality, and provides robust artifact correction with high fidelity, comparable to dual-acquisition methods, while being less prone to errors from patient motion and secondary artifact sources.
Implementation Method 1
applying, by the processor, a transform to the MR data, wherein a result of the applying is an image space representation of the MR data
Implementation Method 2
determining, by the processor, a wrapped phase map of the image space representation of the MR data
Implementation Method 3
scaling, by the processor, the unwrapped phase map into a B0 field map, the scaling based on only the influence of B0 field inhomogeneities on phases in the MR data
Data Source
AI summary
A magnetic resonance (MR) image may be created from MR data by receiving the MR data, applying a transform to the MR data, where a result of the applying is an image space representation of the MR data, determining a wrapped phase map of the image space representation of the MR data, obtaining an unwrapped phase map based on the wrapped phase map, scaling the unwrapped phase map into a B0 field map, reconstructing the MR image based on the MR data, correcting the MR image based on the B0 field map, and outputting the MR image. The scaling may be free of accounting for effects on the MR data by artifact sources secondary to B0 field inhomogeneities.