MRI Ghosting Correction via Unequal Gradient Magnitudes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MRI systems face challenges in fully correcting ghosting artifacts, particularly the Nyquist ghost, in echo planar imaging (EPI) due to signal inconsistencies and hardware constraints, which affect diagnostic accuracy and are not adequately addressed by existing correction methods.
Innovation Solution
The method involves generating prescan images with a larger field of view to separate ghost artifacts from the object, determining and correcting magnitude and phase differences between odd and even images, and applying a correction map to eliminate or reduce ghosting artifacts during the main scan, specifically addressing frequency response non-flatness and signal modulation differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ghosting correction methods are used in MRI systems, then processing time is reduced, but ghosting artifacts remain above acceptable levels affecting diagnostic accuracy
Solution Approach 1:
The patent applies preliminary action by performing a prescan before the main diagnostic scan to determine magnitude and phase correction factors. These correction factors are calculated in advance and stored for use during the actual diagnostic imaging, allowing rapid correction without time-consuming processing during the main scan.
Solution Approach 2:
The patent replaces complex iterative mechanical correction methods with a mathematical substitution approach. By using magnitude and phase correction factors derived from the prescan, the system substitutes a simplified mathematical model that achieves superior ghosting reduction (below 2%) without requiring extensive processing time during the main scan.
2Measurement precision
If larger field of view is used in prescan images, then ghost artifacts are separated from the object for better correction, but scan time and data volume increase
Solution Approach 1:
The patent extracts only the necessary correction information (magnitude and phase factors) from the prescan data. By using a larger field of view in the prescan, ghost artifacts are separated from the object, allowing accurate extraction of correction parameters without needing to process the entire high-resolution diagnostic dataset.
Solution Approach 2:
The patent applies local quality by determining correction factors specifically for regions where ghosting occurs. The magnitude and phase correction factors are calculated locally based on the prescan data, allowing targeted correction without requiring full processing of all image data at high resolution.
3Stability of the object's composition
If frequency response non-flatness is corrected, then image uniformity improves, but processing complexity increases
Solution Approach 1:
The patent merges frequency response correction with the magnitude and phase correction process. By combining these corrections into a unified approach using the prescan data, the system corrects frequency response non-flatness without requiring separate complex processing steps, thereby improving image uniformity while maintaining manageable processing complexity.
Data Source
AI summary
A magnetic resonance imaging (MRI) system, method and/or computer readable medium is configured to effect MR imaging with reduced ghosting artifacts by operations including determining spatially varying signal magnitude differences associated with first and second parts of a reference MR data, and reconstructing a diagnostic image based upon a first and a second parts of main scan data and the determined spatially varying signal magnitude differences. The first parts of the reference data and main scan data is acquired using a first readout gradient, and the second parts of the reference data and main scan data is acquired using a second readout gradient that is different from the first readout gradient.