Symmetrical k-space Trajectory Truncation for MRI Excitation
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Solution Overview
Problem
Magnetic resonance imaging techniques face challenges with longer excitation durations for spatially selective excitations, leading to increased off-resonance effects and longer effective echo times, which result in lower signal-to-noise ratios and image quality issues.
Innovation Solution
A method that utilizes a symmetrical excitation trajectory in k-space, truncated on one side of the k-space center, to reduce excitation duration and echo time without compromising spatial resolution, achieved by modifying the excitation trajectory to cover only a reduced interval while maintaining symmetry conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a spatially selective excitation is used for rFOV imaging, then the readout and acquisition duration is reduced, but the excitation duration is markedly lengthened
Solution Approach 1:
The excitation trajectory in k-space is segmented into two parts: a first part that is retained and a second part that is truncated. This segmentation allows the excitation to cover sufficient k-space for spatial selectivity while reducing the total excitation duration, thereby resolving the contradiction between reduced readout time and shortened excitation time.
Solution Approach 2:
The harmful second part of the excitation trajectory is extracted and removed from the sequence. By taking out only the necessary portion of the k-space trajectory that provides spatial selectivity, the patent eliminates the excessive duration while maintaining the essential function of spatially selective excitation for rFOV imaging.
2Measurement precision
If a spatially selective excitation with longer duration is used, then spatial resolution is improved, but off-resonance effects increase
Solution Approach 1:
Instead of traversing the complete symmetrical k-space trajectory, the patent applies partial action by retaining only the first part of the trajectory. This partial traversal provides sufficient spatial resolution for the imaging application while significantly reducing the excitation duration and the associated off-resonance effects that would occur during the full trajectory.
3Area of stationary object
If a spatially selective excitation is used, then the field of view is reduced, but the effective echo time is lengthened
Solution Approach 1:
The excitation trajectory is segmented to retain only the essential first part that establishes spatial selectivity. By eliminating the redundant second part of the trajectory, the patent reduces the contribution to effective echo time while maintaining the reduced field of view capability, thus resolving the contradiction between FOV reduction and echo time shortening.
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 results in a shorter excitation duration and echo time, reducing off-resonance effects and enhancing the signal-to-noise ratio, while maintaining image quality and allowing for use in various magnetic resonance sequences, including EPI, without requiring additional hardware.
Implementation Method 1
Gradient fields can be generated by a gradient coil arrangement
Implementation Method 2
radio-frequency excitation pulses (which are commonly designated as radio-frequency pulses) are emitted by a radio-frequency coil arrangement. A radio-frequency field (typically designated as a B1 field) is generated by the entirety of the radio-frequency pulses
Implementation Method 3
A subject to be examined is introduced into an imaging region of a magnetic resonance apparatus in which a basic magnetic field with a relatively high field strength (known as the B0 field) is present
Data Source
AI summary
In a method to generate a spatially selective excitation in an imaging region of a magnetic resonance apparatus that precedes an acquisition of magnetic resonance data, in the course of the excitation an excitation trajectory in k-space is traversed, the excitation trajectory having a symmetry relative to the k-space center in at least one direction of k-space in the sense that a first traversed extreme value in this direction corresponds to the negative of the other extreme value traversed in this direction, so the excitation trajectory is shortened in the at least one directions on one side of the zero point between the extreme values, and the shortened excitation trajectory is used for excitation.