Magnetic Resonance Slice Selection Gradient Pulse Phase Correction
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Solution Overview
Problem
Simultaneous multislice imaging in magnetic resonance techniques faces challenges with long acquisition times, restricted application of slice-specific correction-gradient moments, and unwanted contrast differences due to temporal separation of radio-frequency pulses, which affects signal-to-noise ratio and echo times.
Innovation Solution
The method involves modifying slice-selection gradient pulses by increasing gradient strength in edge regions and applying additional correction-gradient moments outside the slice-selection time period to reduce temporal offsets and echo shifts, allowing for shorter slice-selection time periods while maintaining effective correction phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If temporal offsets are applied to radio-frequency pulses for slice-specific correction-gradient moments, then correction phase is achieved, but slice-selection time period duration increases
Solution Approach 1:
The patent applies dynamics by making the gradient strength variable over time within the slice-selection gradient pulse. The gradient strength is increased in edge regions compared to the middle region, creating a time-varying gradient profile that achieves the same correction phase with reduced overall duration. This dynamic adjustment allows the gradient to exert stronger influence during critical periods while maintaining correction effectiveness.
Solution Approach 2:
The patent changes the parameter of gradient strength distribution within the slice-selection gradient pulse. By increasing the gradient strength in edge regions relative to the middle region, the patent modifies the temporal profile of the gradient to achieve more efficient correction phase application, reducing the required duration while maintaining the necessary correction effect.
2Use of energy by moving object
If radio-frequency pulses are completely temporally separated for different slices, then SAR and peak RF power are reduced, but echo time increases and signal-to-noise ratio decreases
Solution Approach 1:
The patent applies partial separation of radio-frequency pulses for different slices rather than complete temporal separation. By allowing partial overlap while still providing some temporal distinction, the patent achieves a compromise that reduces SAR and peak RF power without fully extending the echo time, thereby maintaining better signal-to-noise ratio compared to complete separation.
3Manufacturing precision
If temporal offsets are applied for slice-specific correction, then correction-gradient moment is achieved, but contrast differences between slices increase
Solution Approach 1:
The patent applies local quality by differentiating the gradient strength at different temporal regions of the slice-selection gradient pulse. By increasing gradient strength specifically in edge regions while maintaining different temporal offsets for different slices, the patent achieves slice-specific correction-gradient moments while the localized gradient enhancement helps maintain more uniform contrast across slices compared to uniform gradient application.
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 reduces the duration of slice-selection time periods, minimizes contrast variations between slices, and enhances the signal-to-noise ratio by optimizing gradient pulse sequences and additional gradient moments, enabling faster and more accurate magnetic resonance imaging.
Implementation Method 1
generate, in at least one slice-selection time period, a slice-selection gradient by activation of a slice-selection-gradient pulse
Implementation Method 2
a radio-frequency pulse with a slice-specific frequency is radiated for each of the slices
Implementation Method 3
a slice-specific correction-gradient moment in the slice-selection direction, which contributes to the achievement of the correction phase for the respective slice, acts on the magnetization
Data Source
AI summary
In a method and apparatus to correct a signal phase in the acquisition of magnetic resonance signals of an object to be examined in a slice multiplexing method, magnetic resonance signals from at least two different slices of the object are detected simultaneously. In at least one slice-selection time period, a slice-selection gradient is generated by a slice-selection-gradient pulse. During the activation of the slice-selection gradient in each case a radio-frequency pulse with a slice-specific frequency is emitted for each of the slices. The radio-frequency pulses for the different slices at least partially temporally overlap and are temporally offset for the phase correction, so the duration of the slice-selection time period is shortened by modification of the slice-selection gradients.