Spiral Spin Echo MR Imaging to Reduce B0 Ringing Artefacts
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Solution Overview
Problem
Spiral MR imaging is vulnerable to inhomogeneities in the main magnetic field B0, leading to blurring and degrading image quality due to ringing artefacts, which conventional de-blurring methods fail to adequately address, especially in regions of strong susceptibility-induced magnetic field gradients.
Innovation Solution
The method involves starting the spiral acquisition of MR signal data before the spin echo center, shifting the k-space trajectory to reduce the impact of magnetic field inhomogeneities by relocating signal pile-up away from the k-space center, thereby minimizing ringing artefacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spiral acquisition starts at the spin echo center, then k-space coverage is efficient, but signal pile-up occurs at k-space center due to B0 inhomogeneities causing ringing artefacts
Solution Approach 1:
The spiral acquisition trajectory is shifted to start before the spin echo center, performing the harmful signal sampling earlier when B0 inhomogeneities have not yet caused maximum dephasing. This preliminary action relocates the signal pile-up from the critical k-space center region to less critical regions, reducing ringing artefacts while maintaining efficient k-space coverage
Solution Approach 2:
The invention introduces a temporal dimension shift by adjusting the start time of spiral acquisition relative to the spin echo center. This time-domain adjustment translates to a spatial repositioning of the k-space trajectory, moving the problematic signal pile-up from the center to peripheral regions of k-space
2Manufacturing precision
If conventional de-blurring methods are applied, then some blurring is reduced, but ringing artefacts remain prominent in regions of strong susceptibility-induced magnetic field gradients
Solution Approach 1:
By shifting the spiral acquisition start time before the spin echo center, the method preliminarily addresses the B0 inhomogeneity effect before it can cause maximum signal distortion. This preventive approach reduces the severity of susceptibility-induced artefacts more effectively than post-processing de-blurring methods alone
Data Source
AI summary
The invention relates to a method of MR imaging of an object (10) positioned in an examination volume of an MR device (1). It is an object of the invention to enable spiral MR imaging with a reduced level of ringing artefacts close to strong local IC main magnetic field inhomogeneity. The method of the invention comprises the following steps:—generating a spin echo by subjecting the object (10) to an imaging sequence comprising an RF excitation pulse (31) followed by an RF refocusing pulse (32), wherein a modulated readout magnetic field gradient (34) is applied subsequent to the RF refocusing pulse (32),—acquiring MR signal data by recording the spin echo along a spiral trajectory in k-space, wherein the waveform of the readout magnetic field gradient (34) defining the spiral trajectory starts before the spin echo center (33), and—reconstructing an MR image from the acquired MR signal data. Moreover, the invention relates to an MR device (1) and to a computer program for an MR device (1).