Phase Error Correction in Chemical Shift MRI Using Magnitude Fitting
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Solution Overview
Problem
Bipolar MRI pulse sequences result in phase errors that complicate the quantification of fat and iron deposition, as they are not widely available due to high costs, limiting the application of emerging quantitative imaging biomarkers.
Innovation Solution
A method that corrects phase errors in chemical shift encoded MRI data using complex and magnitude fittings, estimating linear phase offsets to generate phase-corrected images and proton density fat fraction maps, applicable to both bipolar and monopolar readout gradients without requiring additional calibration data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bipolar readout gradients are used in MRI pulse sequences, then acquisition time efficiency is improved, but phase errors between images with different gradient polarities occur
Solution Approach 1:
The patent extracts and isolates the phase error component from the bipolar gradient acquisition data. By separating the phase error estimation as an independent calculation step using magnitude fitting, the method removes the harmful phase artifacts while preserving the efficient bipolar acquisition timeline, thereby maintaining productivity while improving measurement precision.
Solution Approach 2:
The patent introduces magnitude fitting as an intermediary processing step between data acquisition and quantitative analysis. This intermediary method estimates phase errors without requiring additional calibration data or specialized pulse sequences, serving as a mediator that bridges the gap between efficient bipolar acquisition and accurate phase-corrected quantification.
2Measurement precision
If specialized pulse sequences are used to correct phase errors, then quantification accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent enables the standard bipolar pulse sequence to self-correct its own phase errors through post-processing. The magnitude fitting method uses the acquired data itself to estimate and correct phase errors, eliminating the need for external specialized calibration sequences. This self-service approach maintains quantification accuracy while avoiding the complexity and cost of specialized pulse sequences.
Solution Approach 2:
The patent creates a virtual calibration dataset through magnitude fitting that replicates the function of actual calibration data without requiring physical acquisition of additional calibration scans. This copying approach allows phase error correction using standard pulse sequences, avoiding the need for expensive specialized hardware or complex pulse sequence implementations.
3Ease of operation
If standard pulse sequences are used without phase correction, then ease of operation is maintained, but quantification reliability deteriorates
Solution Approach 1:
The patent replaces the mechanical/physical solution of specialized phase-correcting pulse sequences with a computational/mathematical solution. By using magnitude fitting and complex fitting algorithms, the method substitutes hardware complexity with software processing, maintaining ease of operation on standard systems while improving quantification reliability through accurate phase error correction.
Data Source
AI summary
Systems and methods for correcting phase errors in chemical shift encoded data are described. The technique is self-calibrated, without the need for specialized calibration data, and therefore may enable fat and iron quantification using data from clinical and research sites that do not have specialized pulse sequences.