Multi-Shot MR Reconstruction with Reference-Based Navigator Maps
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Solution Overview
Problem
Multi-shot magnetic resonance (MR) image reconstruction is complicated by changing patient motion across different shots, causing phase inconsistency and noise in clinical DWI images, which limits spatial resolution and complicates image reconstruction.
Innovation Solution
A method for compensating for motion in multi-shot MR images by estimating phase variations using a reference image and navigator maps, applying regularized minimization techniques to calculate navigator maps, and reconstructing images using these maps to correct for motion-induced phase inconsistencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-shot MR imaging is used to improve spatial resolution, then image quality is improved, but patient motion between shots causes phase inconsistency and noise
Solution Approach 1:
The patent applies preliminary action by acquiring a reference image before the multi-shot DWI acquisition. This reference image serves as a baseline to calculate motion-induced phase variations during the actual imaging process. By preparing the reference image in advance, the system can subsequently correct phase inconsistencies caused by patient motion without requiring real-time reference acquisitions for each shot.
Solution Approach 2:
The patent implements feedback through the calculation of navigator maps that quantify phase variations between the reference image and each shot. These navigator maps are then fed back into the reconstruction process to correct phase inconsistencies. The feedback loop continuously monitors and adjusts the reconstruction based on measured motion effects, ensuring phase consistency across multiple shots.
2Measurement precision
If navigator maps are calculated using full k-space data, then phase variation estimation is accurate, but computational time and data requirements increase
Solution Approach 1:
The patent applies segmentation by dividing the k-space data into different regions, specifically using only the central portion of k-space for navigator map calculation. This central k-space region contains the most relevant information for phase variation estimation while excluding the peripheral regions that contribute less to phase accuracy but require more computational resources. This segmentation enables accurate phase estimation with reduced computational burden.
Solution Approach 2:
The patent implements partial action by using only a subset of k-space data (central region) rather than processing the entire k-space. This partial approach provides sufficient accuracy for phase variation estimation while significantly reducing computational time and data processing requirements. The method accepts that peripheral k-space data contributes minimally to phase accuracy and focuses computational resources on the most critical central region.
Data Source
AI summary
Systems and methods for estimating navigator maps for multi-shot phase-navigated image reconstruction are provided. The techniques described herein include acquiring a reference image of a subject, calculating, for a multi-shot MR image of the subject, a navigator map using the reference image, and reconstructing the multi-shot MR image by applying the navigator maps to segments of the multi-shot MR image. The MR image and the reference image may be, for example, a T1-weighted image, a T2-weighted image, a fluid-attenuated inversion recovery (FLAIR) image, DWI image, a water separated image, fat separated image, a fat suppressed image, a phase contrasted image, or a blood contrasted image. The reference image may be a different type, and/or acquired from the same or a different sequence than the MR image. The navigator maps may correct for shot-varying motion-induced phase differences in the multi-shot MR image.