MRI Phase Correction Map for CSF-White Matter Signal Unevenness
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) techniques face challenges in effectively reducing black/white signal unevenness in real images due to phase differences between observed elements, particularly cerebrospinal fluid (CSF) and white matter (WM), which can persist even after phase correction, and optimizing threshold values for masking processes is difficult.
Innovation Solution
The MRI apparatus employs an inversion recovery method under a π condition to acquire magnetic resonance data, generates phase data, multiplies phase angles by 2n, unfolds and then reduces these angles by 1/(2n), applies a complex conjugate to generate a phase correction map, and performs phase correction on the data without using a template image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a template image is used for phase correction, then phase correction can be performed, but the imaging period is prolonged
Solution Approach 1:
The patent performs preliminary phase correction by acquiring reference data at a reference position before actual imaging, and uses this pre-acquired reference data to correct phase differences in the actual imaging data. This preliminary action eliminates the need for template images during the imaging process, thereby reducing imaging time while maintaining phase correction accuracy.
2Loss of time
If phase correction is performed without a template image, then imaging time is reduced, but impacts of signal unevenness remain in the real image
Solution Approach 1:
The patent introduces reference data acquired at a reference position as an intermediary element. This reference data serves as a mediator between the raw imaging data and the final corrected image, enabling phase correction without template images. The reference data contains phase information that, when combined with the actual imaging data through complex multiplication, corrects signal unevenness while maintaining imaging speed.
3Measurement precision
If masking is applied to reduce signal unevenness impacts, then real image quality improves, but optimizing threshold value becomes difficult
Solution Approach 1:
The patent extracts phase information from reference data acquired at a reference position and separates it from the main imaging process. By extracting the phase component and using it for correction through complex multiplication, the method eliminates the need for masking operations and threshold optimization, simplifying the process while maintaining image quality.
Data Source
AI summary
A MRI apparatus according to an embodiment includes processing circuitry. The processing circuitry obtains MR data acquired by implementing an IR method under a condition where a phase difference in a complex signal related to observed elements is equal to π, due to a difference in longitudinal magnetization relaxation time between the observed elements; generates phase data on the basis of the MR data; multiplies a phase angle in the phase data by 2n; unfolds the phase of phase data having the phase angle multiplied by 2n; multiplies the phase angle in the unfolded phase data by 1/(2n); generates a phase correction map used for correcting a phase with respect to the complex signal, by applying a complex conjugate to phase data having the phase angle multiplied by 1/(2n); and performs a phase correction on the MR data by using the phase correction map.