PETRA MRI Sequence k-Space Trajectory Optimization
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Solution Overview
Problem
Magnetic resonance sequences with ultrashort echo times, such as the PETRA sequence, face challenges in achieving optimal contrast and signal-to-noise ratio due to limitations in scanning techniques, particularly in radial and Cartesian k-space scanning methods, which affect image quality.
Innovation Solution
The method involves adjusting the number of radial spokes to be measured in the PETRA sequence, ensuring that measurement points closest to the center of k-space are acquired at an optimal time after a pre-pulse, thereby stabilizing contrast and improving signal-to-noise ratio without disrupting the original workflow, and modifying the k-space trajectory to prioritize center-proximal measurement points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If radial scanning is used for the first region of k-space with phase coding gradients ramped up before excitation pulse, then echo time is shortened and acquisition speed is improved, but the central region of k-space cannot be scanned and contrast optimization is limited
Solution Approach 1:
The patent divides k-space into two distinct regions: a first region scanned radially with phase coding gradients for ultrashort echo time acquisition, and a second central region scanned Cartesian for optimized contrast. This segmentation allows each region to be acquired with the most appropriate method for its specific requirements, resolving the contradiction between speed and contrast optimization.
Solution Approach 2:
Different scanning strategies are applied to different regions of k-space based on their specific needs. The peripheral region uses radial scanning for speed, while the central region uses Cartesian scanning with pre-pulses for contrast optimization. This local differentiation resolves the contradiction by allowing each region to be optimized independently.
2Measurement precision
If pre-pulses are radiated for T1 contrast enhancement, then contrast is improved, but additional wait time is required which increases total acquisition time
Solution Approach 1:
The patent applies pre-pulses only to the Cartesian scanning of the second central region of k-space, rather than to the entire k-space acquisition. This segmentation allows contrast enhancement where it is most needed (central region) while minimizing the time penalty, as pre-pulses are not required for the faster radial scanning of the first region.
Solution Approach 2:
Instead of applying pre-pulses to the entire k-space acquisition, the patent applies them partially only to the second region scanning. This partial action achieves contrast enhancement for the most critical central region while avoiding the full time penalty that would result from applying pre-pulses to all regions.
3Measurement precision
If Cartesian scanning is used for the second central region of k-space, then contrast is optimized, but additional transformation steps are required increasing processing complexity
Solution Approach 1:
The patent segments the k-space acquisition into two regions with different scanning methods. The second central region is scanned Cartesian to provide optimized contrast, and this segmented approach isolates the processing complexity to only the portion of data that requires it, rather than complicating the entire acquisition process.
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 image acquisition quality by optimizing contrast and signal-to-noise ratio, minimizing gradient jumps, and maintaining the sequence's noise reduction advantages, leading to improved image quality with minimal modifications to the existing workflow.
Implementation Method 1
The invention concerns a method for image acquisition with a magnetic resonance device using a magnetic resonance sequence
Implementation Method 2
at least two phase coding gradients have already been ramped up completely before administration of the excitation pulse
Implementation Method 3
a non-selective radio-frequency excitation pulse radiated by a radio-frequency transmission/reception device
Implementation Method 4
A first region, which does not include the center of k-space, is scanned by at least two phase coding gradients being initially switched (activated) in respective spatial directions
Data Source
AI summary
In a method and magnetic resonance apparatus for image acquisition using a magnetic resonance sequence in which k-space corresponding to the imaging area is scanned, a first region of k-space, which does not include the center of k-space, is scanned radially along a number of spokes emanating from the k-space center, and at least two phase coding gradients are completely ramped up before the excitation pulse. A second central region of k-space, which remains without the first region, is scanned in a Cartesian manner. For contrast increase a pre-pulse is provided before a predetermined number of individual measurements. The number of spokes is selected so a measurement point nearest to the k-space center is measured at a predetermined point in time after the pre-pulse, which is optimal for signal-to-noise ratio and/or contrast.