Radial k-space profile ordering for MR imaging phase error cancellation
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Solution Overview
Problem
Current MR imaging techniques using radial or spiral k-space trajectories are susceptible to phase errors and artefacts due to inhomogeneities and eddy currents, leading to distorted images.
Innovation Solution
A method for MR imaging that involves acquiring radial or spiral k-space profiles with pairs of adjacent profiles in opposite directions and close in k-space, allowing for intrinsic phase error cancellation during reconstruction, using a multi-shot acquisition scheme with orientations incremented by a golden angle to ensure uniform k-space coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If radial or spiral k-space trajectories are used for MR imaging, then image acquisition speed and motion robustness are improved, but phase errors and artefacts increase due to inhomogeneities and eddy currents
Solution Approach 1:
The patent divides the k-space acquisition into multiple segments or shots, where each segment acquires a portion of the k-space data. This segmentation allows for separate phase error correction for each segment and enables parallel acquisition strategies that improve overall efficiency while maintaining image quality through targeted correction approaches.
Solution Approach 2:
The patent employs phase error correction by changing the phase parameters of the acquired data. Specifically, it applies phase correction algorithms that adjust the phase of the k-space data to compensate for errors introduced by inhomogeneities and eddy currents, thereby improving image quality without sacrificing acquisition speed.
2Manufacturing precision
If conventional phase error correction methods are applied, then image quality improves, but acquisition time and processing complexity increase
Solution Approach 1:
The patent performs phase error correction as part of the reconstruction process rather than adding separate correction steps after acquisition. By integrating the correction into the existing reconstruction pipeline, it avoids additional acquisition time while still improving image quality through effective phase error compensation.
Solution Approach 2:
The patent uses the acquired data itself to determine and correct phase errors. By analyzing the acquired k-space data to identify phase errors and then applying corrections based on this analysis, the system performs self-correction without requiring additional reference scans or external calibration data, thus avoiding time loss.
3Productivity
If multiple k-space profiles are acquired in temporal proximity, then sampling efficiency improves, but phase errors accumulate due to eddy currents and field drift
Solution Approach 1:
The patent implements phase error correction that uses feedback from the acquired data itself. By continuously monitoring the phase information in the acquired k-space profiles and using this information to correct subsequent profiles, the system maintains phase stability across multiple rapidly acquired profiles while preserving sampling efficiency.
Solution Approach 2:
The patent applies phase correction periodically across the acquired profiles, using a systematic approach that addresses phase errors at regular intervals throughout the acquisition. This periodic correction maintains phase stability across the entire dataset while allowing efficient continuous sampling.
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 significantly reduces phase errors and artefacts in the reconstructed images, improving image quality and motion robustness, while also enhancing fat suppression and compatibility with advanced imaging techniques like compressed sensing and deep learning.
Implementation Method 1
the body of the patient to be examined is arranged in a strong, uniform magnetic field B0 whose direction at the same time defines an axis (normally the z-axis) of the co-ordinate system to which the measurement is related. The magnetic field B0 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 magnetic field B0 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).
Data Source
AI summary
The invention relates to a method of MR imaging of an object (10). It is an object of the invention to enable MR imaging using radial acquisition with a reduced level of phase distortions and corresponding image artefacts. The method of the invention comprises the steps of: a) generating MR signals by subjecting the object to an imaging sequence comprising RF pulses and switched magnetic field gradients; b) acquiring the MR signals as radial k-space profiles, wherein pairs of spatially adjacent k-space profiles are acquired in opposite directions and wherein k-space profiles acquired in temporal proximity are close to each other in k-space; c) reconstructing an MR image from the acquired MR signals. Moreover, the invention relates to a MR device (1) and to a computer program for a MR device (1).