Magnetic Resonance Imaging In-Phase Opposed-Phase Signal Acquisition
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Solution Overview
Problem
Conventional Dixon methods for magnetic resonance imaging require multiple echo trains to differentiate between tissue types, leading to increased measuring duration and susceptibility to motion artifacts, and often result in chemical shift artifacts that impair image quality.
Innovation Solution
A method that uses a train of RF refocusing pulses to generate spin echo signals, with readout gradients activated at specific time points to alternately capture 'in-phase' and 'opposed-phase' signals, allowing for the reconstruction of first and second images that are insensitive to movement artifacts and avoid chemical-shift artifacts, enabling accelerated data acquisition and reliable tissue differentiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Dixon methods use multiple echo trains to differentiate tissue types, then tissue differentiation capability is improved, but measuring duration increases and motion artifacts increase
Solution Approach 1:
The patent combines the acquisition of in-phase and opposed-phase signals into a single echo train by using alternating readout gradients. Instead of requiring separate echo trains for each signal type, the method merges both signal acquisitions into one continuous process, thereby reducing the total measuring duration while maintaining tissue differentiation capability.
Solution Approach 2:
The patent implements continuous data acquisition throughout the echo train by alternately sampling in-phase and opposed-phase signals without interruption. This continuous action eliminates the need for multiple discrete echo trains, reducing measurement time while ensuring complete tissue differentiation data is captured in a single continuous process.
2Measurement precision
If conventional Dixon methods use multiple echo trains, then tissue differentiation is achieved, but susceptibility to motion artifacts increases
Solution Approach 1:
By merging in-phase and opposed-phase signal acquisition into a single echo train, the patent ensures that both signal types are captured within the same temporal window. This eliminates the time gap between acquisitions that would allow motion to occur, thereby reducing motion artifact susceptibility while maintaining the ability to differentiate tissue types through Dixon processing.
3Measurement precision
If conventional Dixon methods are used, then tissue differentiation is achieved, but chemical shift artifacts occur that impair image quality
Solution Approach 1:
The patent changes the temporal parameter of signal acquisition by using alternating readout gradients to capture in-phase and opposed-phase signals at different time points within the same echo train. This temporal separation allows the Dixon algorithm to differentiate tissue types while the single-echo-train approach minimizes the conditions that generate chemical shift artifacts.
4Loss of time
If single-shot method is used to accelerate recording, then measuring time is reduced, but the entire k-space data must be recorded after one RF excitation which increases complexity
Solution Approach 1:
The patent segments the k-space acquisition process by alternating between in-phase and opposed-phase signal sampling within the same echo train. This segmentation allows the use of a single shot approach while organizing the data acquisition in a structured manner that reduces apparent complexity through systematic alternation of gradient polarities.
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 allows for the rapid recording of measurement data, reducing measuring time and minimizing artifacts, enabling the creation of pure fat and water images with improved image quality and reliability, even in regions affected by respiration, and can be combined with partial Fourier and parallel acquisition techniques for further acceleration.
Implementation Method 1
Magnetic resonance (MR) technology is a known modality with which images of the interior of an examination object can be generated. In simple terms, to this end, the examination object is positioned in a strong, static, homogeneous basic magnetic field, also called a B0 field
Implementation Method 2
to trigger nuclear spin resonances, radio-frequency excitation pulses (RF pulses) are radiated into the examination object, the triggered nuclear spin resonances are measured as echo signals
Implementation Method 3
The excited nuclear spins can be manipulated by activating dephasing and rephasing gradients in such a way that the signal decays more quickly than accounted for by the T2* decay inherent in the excited tissue, but, after a certain time (the echo time (TE)) after the RF excitation pulse, a so-called gradient echo (GRE) forms
Implementation Method 4
Another technique is to generate a so-called spin echo signal (SE) by radiating at least one RF refocusing pulse following the radiation of an RF excitation pulse after a time, again called the echo time, after the RF excitation pulse
Implementation Method 5
Generally, rapidly activated magnetic gradient fields are superimposed on the basic magnetic field for spatial encoding of the measurement data
Data Source
AI summary
In a method for creating a first and a second image dataset of an examination object, a train of RF refocusing pulses are radiated into the examination object after the radiation of an RF excitation pulse to generate a spin echo signal after each radiated RF refocusing pulse, phase encoding gradients are activated for encoding the phases of the spin echo signals generated, and readout gradients are activated in each case in a readout window to read out the generated spin echo signals as measurement data. The readout windows alternately include a first time point at which the phases of the different spin species in the spin echo signal are the same, and a second time point at which the phases of the different spin species in the spin echo signal are not the same.