Random Cartesian MRI Sampling for Angiography and Perfusion
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Solution Overview
Problem
Current MRI systems face challenges in acquiring both angiographic and perfusion images efficiently, as existing methods often require separate acquisitions that can lead to undesirable contrast enhancement phases, increased acquisition times, and compromised spatial or temporal resolution.
Innovation Solution
A system and method that acquire MR data using a Cartesian acquisition with a k-space sampling pattern similar to projection reconstruction, dividing k-space into a central region and radially-extending sectors, allowing for time-resolved image data collection and simultaneous production of MRA and perfusion images without extending acquisition times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate acquisitions are used for angiographic and perfusion images, then each image type can be optimized independently, but acquisition time increases and contrast enhancement phases may be compromised
Solution Approach 1:
The patent combines angiographic and perfusion image acquisitions into a single unified acquisition process. The system acquires both types of image data simultaneously during one contrast agent bolus passage, eliminating the need for separate acquisitions. This merging approach reduces total acquisition time while maintaining the quality requirements for both image types through coordinated sampling strategies.
Solution Approach 2:
The patent employs periodic sampling of k-space during the contrast agent bolus passage, with different sampling rates and patterns applied at different time periods. The system uses high sampling rates during peak contrast enhancement for angiographic imaging and adjusts sampling accordingly for perfusion imaging, optimizing both image types within a single periodic acquisition window.
2Measurement precision
If separate acquisitions are performed for MRA and perfusion imaging, then each can be optimized, but the number of contrast agent boluses increases
Solution Approach 1:
The system merges angiographic and perfusion imaging into a single acquisition that utilizes one contrast agent bolus. By coordinating the sampling timing and patterns, the system extracts both angiographic and perfusion information from the same contrast passage, thereby reducing the total quantity of contrast agent required compared to separate acquisitions.
Solution Approach 2:
The unified acquisition system performs multiple functions simultaneously: it captures angiographic data during peak contrast enhancement and perfusion data throughout the contrast passage. This multi-functional approach allows a single contrast agent bolus to serve dual purposes, reducing the need for additional contrast material.
3Productivity
If Cartesian sampling is used for rapid acquisition, then acquisition time decreases, but spatial resolution may be compromised
Solution Approach 1:
The patent applies different sampling densities to different regions of k-space. The center region of k-space is sampled at a higher density to ensure adequate spatial resolution, while peripheral regions use lower sampling density. This local quality approach maintains necessary resolution in critical areas while enabling faster overall acquisition through reduced sampling in less critical regions.
Solution Approach 2:
The system uses partial sampling of k-space, acquiring only the most essential data points needed for diagnostic quality images. By sampling only the central region and selected peripheral points rather than the entire k-space grid, the system achieves rapid acquisition while maintaining sufficient spatial resolution for clinical purposes.
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 enables coordinated acquisition of angiographic and perfusion information with improved image quality, reduced acquisition time, and minimized artifacts from contrast material effects, using a single bolus of contrast agent and reducing patient dose.
Implementation Method 1
magnetic field gradients (Gx, Gy, and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used
Implementation Method 2
If the substance, or tissue, is subjected to a magnetic field (excitation field B1) that is in the x-y plane and that is near the Larmor frequency, the net aligned moment, Mz, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment Mxy
Data Source
AI summary
A system and method are provided for producing a magnetic resonance image of a subject with a magnetic resonance imaging (MRI) system. The method includes acquiring k-space image data from a subject arranged in an MRI system by performing a pulse sequence. To perform the pulse sequence the MRI system divides k-space into a plurality of radially-extending sectors extending along a radial direction away from an origin of k-space. The plurality of radially-extending sectors include a width transverse to the radial direction that is defined by a vane angle chosen to be greater than a floating point precision of the trigonometric functions that define the radially-extending sectors. The MRI system acquires imaging data from at least the radially-extending sectors to undersample the periphery of k-space by only sampling k-space within the plurality of radial sectors and reconstructs an image of the subject using the imaging data.