Multi-Echo Segmented K-Space MR Imaging Motion Artifact Reduction
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Solution Overview
Problem
Current magnetic resonance (MR) imaging techniques, such as Turbo Spin Echo sequences, are sensitive to motion, leading to ghost artifacts that compromise diagnostic value due to segmented k-space acquisition.
Innovation Solution
A method for MR imaging that acquires central k-space in a single shot, reducing motion sensitivity by aligning start and end points of peripheral k-space sampling with central k-space sampling, and applying this approach with multi-echo sequences like spin echo or gradient echo, potentially combining with techniques like PROPELLER or compressed sensing to enhance robustness and reduce scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If segmented k-space acquisition is used to reduce scan time, then productivity is improved, but motion artifacts increase reducing image quality
Solution Approach 1:
The patent divides k-space into central and peripheral portions, applying different acquisition strategies to each segment. The central k-space is acquired in a single shot to ensure motion robustness, while peripheral k-space is acquired in multiple shots to maintain efficiency. This selective segmentation resolves the contradiction by optimizing each region according to its specific requirements.
Solution Approach 2:
Different acquisition qualities are applied to different regions of k-space. The central region receives high-quality single-shot acquisition to prevent motion artifacts, while peripheral regions use multi-shot acquisition for efficiency. This local differentiation allows the system to maintain overall image quality while improving scan time.
2Reliability
If single shot acquisition is used for central k-space, then motion robustness is improved, but scan time increases
Solution Approach 1:
The patent segments k-space acquisition into two distinct parts: central k-space acquired in a single shot for motion robustness, and peripheral k-space acquired in multiple shots for efficiency. This segmentation allows the system to apply single-shot acquisition only where necessary, minimizing the impact on overall scan time while maximizing motion robustness where it matters most.
Solution Approach 2:
Instead of applying single-shot acquisition to the entire k-space (which would excessively increase scan time), the patent applies it partially only to the central region. This partial action provides sufficient motion robustness for the most critical part of the image while avoiding the excessive time penalty of full single-shot acquisition.
3Productivity
If multi-echo sequences are used to accelerate imaging, then productivity is improved, but sensitivity to motion increases worsening image quality
Solution Approach 1:
The patent combines multi-echo sequences with k-space segmentation, using the multi-echo capability to efficiently acquire peripheral k-space while the central k-space is acquired with motion-robust single-shot methodology. This hybrid approach leverages the speed of multi-echo sequences while mitigating their motion sensitivity through selective application.
Solution Approach 2:
Different acquisition methodologies are applied to different k-space regions: multi-echo sequences are used for peripheral regions where speed is prioritized, while single-shot acquisition is used for central regions where motion robustness is critical. This local quality differentiation resolves the contradiction between imaging speed and motion sensitivity.
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 method effectively reduces motion artifacts and scan time while maintaining image quality, allowing for more robust and efficient MR imaging by sampling central k-space at a single point in time and optimizing peripheral k-space sampling.
Implementation Method 1
The magnetic field produces different energy levels for the individual nuclear spins in dependence on the magnetic field strength which can be excited (spin resonance) by application of an electromagnetic alternating field (RF field) of defined frequency (so-called Larmor frequency, or MR frequency)
Implementation Method 2
the magnetization performs a precessional motion about the z-axis. The precessional motion describes a surface of a cone whose angle of aperture is referred to as flip angle
Implementation Method 3
the magnetization in the direction perpendicular to the z direction relaxes with a second time constant T2 (spin-spin or transverse relaxation time)
Data Source
AI summary
An object (10) is placed in an examination volume of a MR device (1) and imaged using a multi-echo imaging technique which is robust with respect to motion. The imaging includes subjecting the object (10) to a number of shots of a multi-echo imaging sequence to generate a train of echo signals by each shot and acquiring the echo signals. Each echo signal represents a k-space profile, wherein k-space (20) is divided into a central k-space part (21) and one or more peripheral k-space parts (22, 23). The central k-space part (21) is sampled by a single shot of the multi-echo imaging sequence, and the peripheral k-space parts (22, 23) are sampled by one or more further shots (25, 28) of the multi-echo sequence; and an MR image is reconstructed from the k-space profiles.