Artifact-avoidance gradients in spin-echo MRI sequences
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic resonance imaging (MRI) technologies face artifacts due to ambiguities in spatial encoding, particularly outside the field of view (FOV), leading to reduced image quality and potential misdiagnosis, especially with parallel acquisition techniques like iPAT, which increase scan time when attempting to mitigate these issues.
Innovation Solution
A method involving the use of artifact-avoidance gradients with different amplitudes, activated between excitation and refocusing pulses in a spin-echo sequence, to balance and cancel out ambiguous encodings, thereby suppressing or reducing artifacts without extending scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel acquisition techniques like iPAT are used to improve scan speed or resolution, then productivity is improved, but artifacts are generated that reduce measurement precision and image quality
Solution Approach 1:
The patent applies preliminary anti-action by introducing artifact-avoidance gradients before the ambiguous encoding occurs. These gradients are designed to dephase signal components from regions outside the FOV, preventing them from causing artifacts when parallel acquisition techniques are used. The gradients are applied in advance to counteract the potential harmful effect of ambiguous spatial encoding.
2Measurement precision
If scan time is extended to reduce artifacts by recording data multiple times with different reference lines, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The patent extracts the problematic signal components from regions outside the FOV by applying artifact-avoidance gradients that selectively dephase these components. This allows the useful signals within the FOV to be preserved while removing the harmful external signals that cause artifacts, eliminating the need for multiple scans.
3Measurement precision
If artifact-avoidance gradients with different amplitudes are activated, then measurement precision is improved by reducing artifacts, but device complexity increases
Solution Approach 1:
The patent implements parameter changes by varying the amplitude of artifact-avoidance gradients applied during different phases of the spin-echo sequence. The control computer calculates optimal gradient amplitudes based on the specific imaging parameters and applies them dynamically, allowing effective artifact suppression while maintaining system flexibility.
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 effectively separates ambiguous encodings and reduces artifacts, enhancing image quality without prolonging the scan time, by dephasing signal components outside the FOV and preventing their rephasing, thus improving diagnostic accuracy.
Implementation Method 1
For spatial encoding of the scan data, rapidly switched magnetic gradient fields are overlaid on the basic magnetic field
Implementation Method 2
In phase encoding, such ambiguities also result in artifacts that significantly reduce the quality of the reconstructed images
Data Source
AI summary
In a method and magnetic resonance (MR) apparatus for avoiding artifacts in scan data recorded by execution of a spin-echo sequence, an excitation pulse is radiated, at least one refocusing pulse is radiated, and at least one echo signal is read out. Following the radiation of the excitation pulse and before the readout of the at least one echo signal, at least two artifact-avoidance gradients with different amplitudes are activated, wherein the moments of the artifact-avoidance gradients balance each other.