Magnetic Resonance Dixon Method Gradient Polarity
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Solution Overview
Problem
Current magnetic resonance (MR) techniques face challenges in separating signals of different spin species, such as fat and water, due to artifacts caused by chemical shift differences, leading to suboptimal image quality and increased measurement time.
Innovation Solution
A method involving the acquisition of at least two MR datasets with spins at different phase positions relative to each other, using readout gradients of alternating polarity, allows for the creation of combination images that are less prone to artifacts and can be processed more quickly, reducing measurement time and improving image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Dixon methods are used to separate signals of different spin species, then signal separation is achieved, but chemical shift artifacts occur and measurement time increases
Solution Approach 1:
The patent divides the acquisition of k-space data into two separate segments: one segment acquired with a first readout gradient polarity and another segment acquired with a second readout gradient polarity. This segmentation allows the chemical shift artifacts, which manifest differently in each polarity, to be separated and subsequently eliminated through combination, resolving the contradiction between achieving signal separation and avoiding artifacts.
Solution Approach 2:
The patent uses the readout gradient polarity as an intermediary variable to differentiate the acquisition of the two spin species signals. By switching the gradient polarity between acquisitions, the system creates distinguishable intermediate states that can be mathematically separated, enabling artifact-free signal separation without increasing measurement time.
2Measurement precision
If conventional Dixon methods are used to separate signals of different spin species, then signal separation is achieved, but measurement time increases
Solution Approach 1:
The patent merges the acquisition of multiple spin species signals into a single unified measurement process by alternating readout gradient polarities within one scan. This combining approach allows simultaneous acquisition of data from different spin species without requiring separate measurements, thereby achieving signal separation without increasing measurement time.
Solution Approach 2:
The patent maintains continuous data acquisition throughout the measurement process by seamlessly switching between different readout gradient polarities without interrupting the scan. This continuous action ensures that all necessary data for separating different spin species is collected in a single uninterrupted measurement, preventing time 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 enhances the separation of spin species images by minimizing chemical shift artifacts and reducing overall measurement time, resulting in higher image quality and efficiency compared to conventional Dixon methods.
Implementation Method 1
the nuclear spin resonances triggered are measured as what is known as k-space data
Implementation Method 2
Different spin species process differently, whereby a different magnetic field arises at the nucleus in each case, which leads to different resonant frequencies. This is referred to as a chemical shift between the different spin species.
Implementation Method 3
For spatial encoding of the measurement data, rapidly switched magnetic gradient fields are superimposed on the basic magnetic field
Data Source
AI summary
Techniques are disclosed for acquiring at least two measurement datasets, each consisting of measurement data. The two measurement datasets are recorded at points in time at which spins of a first spin species present in the examination object have different phase positions from spins of a second spin species present in the examination object. Moreover, the two measurement datasets are recorded in each case while switching readout gradients of different polarity, and thus the desired measurement datasets may be recorded faster than conventional approaches.