MR Phase Distribution Correction via Field Inhomogeneity Segmentation
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Solution Overview
Problem
Existing MR imaging methods face challenges in accurately determining phase distributions, especially at the edge of image recording regions due to rapid spatial variations in the signal phase caused by magnetic field inhomogeneities, leading to errors in phase difference determination and erroneous representations.
Innovation Solution
A method that combines measured phase distributions with a known magnetic field distribution to generate a correction-phase distribution, which is then used to correct the phase values and restrict them to a defined interval, reducing errors by separating magnetically induced phase variations and enabling more precise determination of relative phase relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-unwrapping techniques are used to determine actual phase difference, then the value range of phase distribution is extended beyond [-π; +π], but errors are propagated over large image regions in edge areas where rapid spatial phase variations occur
Solution Approach 1:
The patent divides the phase distribution determination into two separate components: a measured phase distribution (from actual MR signals) and a correction phase distribution (from simulated field inhomogeneities). This segmentation allows each component to be optimized independently - the measured phase for accuracy in central regions and the correction phase for reliability in edge regions where rapid variations occur.
Solution Approach 2:
The patent introduces a correction phase distribution as an intermediary element that mediates between the measured phase distribution and the final absolute phase distribution. This correction phase, derived from simulated field inhomogeneities, acts as a bridge to compensate for errors in the measured phase, particularly in edge regions where rapid spatial variations cause phase-unwrapping failures.
2Measurement precision
If filter techniques are used to extract high-frequency components as useful signal, then slow spatial variations are suppressed, but rapid spatial phase variations in edge regions are erroneously assigned to useful signal
Solution Approach 1:
The patent extracts the harmful component (rapid spatial phase variations due to field inhomogeneities) from the measured phase distribution and places it into a separate correction phase distribution. By taking out this problematic component, the remaining measured phase distribution contains only the useful signal with slow spatial variations, while the extracted component can be independently corrected using simulated field inhomogeneities.
3Ease of operation
If phase values are restricted to defined presentation interval, then phase distribution is easier to represent, but absolute phase difference information is lost
Solution Approach 1:
The patent changes the parameter representation by separating the phase into two components with different characteristics: the measured phase distribution maintains values in the restricted interval [-π; +π] for easy representation, while the correction phase distribution uses unrestricted values to preserve absolute phase difference information. The final absolute phase distribution is obtained by combining these two components, thus achieving both ease of operation and information preservation.
Data Source
AI summary
In a method and apparatus for determination of phase distributions in MR imaging, a measured phase distribution of the region of interest is combined with at least one second phase value to form a combination-phase distribution, wherein the phase values of the combination-phase distribution are restricted to a defined presentation interval. A correction-phase distribution is generated, based on a known magnetic field distribution in the region of interest. The phase values thereof are not restricted to the defined presentation interval. A corrected combination-phase distribution is generated using the correction-phase distribution and the combination-phase distribution, in which the phase values are restricted to the defined presentation interval. An absolute combination-phase distribution is generated from the corrected combination-phase distribution, in which the phase values are not restricted to the defined presentation interval.