Segmented Multi-Slice MRI Using Parallel Imaging Reconstruction
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Solution Overview
Problem
Current MRI techniques face challenges in reducing image blur and geometric distortion due to long encoding trains in single-shot Echo Planar Imaging (EPI), while accelerated parallel imaging methods suffer from signal-to-noise ratio losses and artifacts from patient movement and physiological changes in segmented multi-shot acquisitions.
Innovation Solution
The integration of a consecutive-segment acquisition strategy with parallel imaging acceleration and Simultaneous Multi-Slice techniques using multiband RF pulses and Slice GRAPPA reconstruction, which minimizes vulnerability to motion and physiological changes by acquiring slices simultaneously and applying varying flip angles to maintain magnetization across segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single-shot EPI acquisition is used, then temporal efficiency is improved, but image quality deteriorates due to T2* blurring and geometric distortion
Solution Approach 1:
The EPI acquisition is divided into multiple segments (e.g., 2-4 segments) where each segment acquires a portion of k-space lines. This segmentation reduces the readout time per segment, minimizing T2* blurring and geometric distortion while maintaining reasonable scan times. The segments are then combined through parallel imaging reconstruction to form the complete image.
Solution Approach 2:
The patent applies parallel imaging acceleration in the phase-encoding direction to reduce the number of phase encoding steps. By using multiple receive coils with different spatial sensitivities, the system can undersample k-space and reconstruct the full image through coil combination algorithms (e.g., GRAPPA, SENSE), thereby reducing readout time and improving image quality without excessive temporal penalty.
2Loss of time
If accelerated parallel imaging is applied, then readout time is reduced, but signal-to-noise ratio deteriorates due to g-factor losses
Solution Approach 1:
The patent applies partial acceleration with acceleration factors typically ranging from 2x to 4x, balancing the reduction in readout time against the acceptable loss in SNR. This partial acceleration is sufficient to reduce T2* blurring and geometric distortion while maintaining reasonable image quality. The acceleration factor is carefully selected based on the specific imaging application and coil array geometry to optimize the trade-off between speed and SNR.
3Manufacturing precision
If segmented multi-shot acquisition is used, then image quality is improved by reducing blurring, but vulnerability to motion artifacts increases
Solution Approach 1:
The patent employs prospective motion correction techniques where motion parameters are estimated before or during the acquisition process, and the acquisition parameters are adjusted in real-time to compensate for anticipated motion. This preliminary action reduces the vulnerability to motion artifacts by proactively correcting for expected patient movement or physiological changes during the segmented acquisition.
4Loss of time
If higher acceleration factors are applied, then readout time is further reduced, but image artifacts increase due to undersampling
Solution Approach 1:
The patent incorporates feedback mechanisms where the acquired data from each segment and each coil is used to inform the reconstruction process. Advanced parallel imaging reconstruction algorithms (e.g., iterative SENSE, GRAPPA with regularization) use the available coil data and known coil sensitivity profiles to estimate the missing k-space lines, thereby reducing undersampling artifacts while maintaining high acceleration factors. The reconstruction process iteratively refines the image to minimize artifacts.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces image blur and geometric distortion, maintains high signal levels, and achieves higher acceleration factors than conventional methods, balancing temporal efficiency and image quality by distributing acceleration across slices and in-plane directions.
Implementation Method 1
Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that utilizes magnetization to visualize soft tissue
Implementation Method 2
an array of RF coils is used to detect the MR signal
Data Source
AI summary
A method for accelerated segmented magnetic resonance (MR) image data acquisition includes using a plurality of RF pulses to excite one or more slices of an anatomical area of interest according to a predetermined slice acceleration factor. Next, a collapsed image comprising the slices is acquired using a consecutive segment acquisition process. Then, a parallel image reconstruction method is applied to the collapsed image to separate the collapsed image into a plurality of slice images.