MRI Dephasing Compensation via Multi-Gradient K-Space Segmentation
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Solution Overview
Problem
Magnetic resonance imaging (MRI) with gradient-recalled-echo (GRE) sequences is hindered by susceptibility differences, particularly from metal objects, leading to dephasing-induced signal loss and artifacts, as existing methods are unsuitable for reducing these issues effectively.
Innovation Solution
A method involving the recording of multiple raw data sets with specific additional dephasing steps to rephase spins, allowing for the selection of the maximum signal value at each image point, thereby compensating for dephasing-induced losses and reducing artifacts in the final MRI data set.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If GRE sequences are used for magnetic resonance imaging, then shorter echo and repetition times are achieved, but dephasing-induced signal loss and artifacts occur due to susceptibility differences
Solution Approach 1:
The k-space is segmented into multiple regions, each acquired with a different additional dephasing gradient. This allows different portions of the data to be collected under different dephasing conditions, enabling subsequent selection of optimal data for each image location.
Solution Approach 2:
The dephasing parameter (additional dephasing gradient strength) is varied across different k-space regions. By changing this parameter, the patent creates multiple data sets with different dephasing characteristics, allowing selection of data that minimizes signal loss at each location.
2Reliability
If multiple raw data sets with additional dephasing are recorded, then dephasing-induced signal loss is reduced, but recording time increases
Solution Approach 1:
Multiple k-space data sets acquired with different dephasing gradients are merged by selecting, for each image location, the data with the maximum absolute value. This combining strategy recovers signal that would otherwise be lost due to dephasing while maintaining efficient data acquisition.
Solution Approach 2:
Instead of acquiring complete redundant data sets, the patent acquires partial k-space data for each dephasing condition and combines them selectively. This partial action approach achieves signal recovery without the full time cost of complete multiple acquisitions.
3Stability of the object's composition
If susceptibility differences are present in the target region, then artifacts and signal loss occur, but the basic field homogeneity is compromised
Solution Approach 1:
The patent converts the harmful dephasing effect caused by susceptibility differences into a beneficial selection mechanism. By intentionally applying additional dephasing gradients and selecting maximum value data, the method recovers signal at locations where susceptibility differences would normally cause complete signal loss.
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 reduces or eliminates dephasing-induced signal losses, enhancing imaging quality by ensuring that spins are rephased, even in regions affected by interference fields, thus improving the homogeneity of the MRI data set.
Implementation Method 1
dephasings induced by the susceptibility differences are the same at each point so that no distortion can occur in the image
Implementation Method 2
at least one further raw data set of the target region is recorded that corresponds to a raw-data specific additional dephasing of the spins in the target region
Data Source
AI summary
In a method and apparatus for recording a magnetic resonance data set of a target region of an object, wherein the target region contains at least one interfering object with a susceptibility difference from the rest of the target region that influences the homogeneity of the basic magnetic field, in particular a metal object and/or an air inclusion, in addition to a first raw data set of the target region recorded without additional dephasing, at least one further raw data set of the target region is recorded that corresponds to a raw-data specific additional dephasing of the spins in the target region. For each image point of the magnetic resonance data set, the maximum value raw data of the corresponding image points of all raw data sets in spatial domain are selected as magnetic resonance data.