Multi-Directional Velocity Encoding in Phase-Contrast MRI
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetic resonance angiography (MRA) techniques, such as contrast-enhanced, time-of-flight, and phase-contrast MRA, face limitations including the need for invasive contrast agents, high costs, potential health risks, inaccurate hemodynamic information, and lengthy acquisition times, particularly for multi-dimensional phase-contrast imaging.
Innovation Solution
A system and method for phase-contrast MR imaging that combines multiple velocity encodings per readout, reducing acquisition time by acquiring a set of velocity-insensitive reference data and combined velocity-sensitive data, and using a reconstruction method to determine directional velocity components, allowing for the generation of velocity maps without the need for separate acquisitions for each velocity encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate acquisitions are performed for each velocity encoding in phase-contrast MRA, then accurate velocity information is obtained, but acquisition time becomes excessively long
Solution Approach 1:
The patent combines multiple velocity encodings into a single acquisition by encoding velocities along multiple directions simultaneously within one readout period. This is achieved by applying gradient pairs with different orientations and combining the acquired data through a reconstruction algorithm that separates the velocity components, thus obtaining multi-directional velocity information without performing separate acquisitions for each direction.
Solution Approach 2:
The patent introduces an additional encoding dimension by incorporating velocity encoding along multiple spatial directions within a single acquisition. Instead of sequentially acquiring data for each velocity direction, the method encodes velocity information in multiple dimensions simultaneously and uses computational reconstruction to extract the velocity components, effectively adding a dimension of parallel information acquisition.
2Loss of information
If multiple data sets are acquired for multi-dimensional phase-contrast imaging, then comprehensive velocity information is obtained, but the complexity of the imaging process increases
Solution Approach 1:
The patent merges multiple velocity encoding operations into a single acquisition sequence by applying gradient pairs oriented in different directions during the same readout period. The combined data contains encoding information for multiple velocity directions, which are then separated through a reconstruction algorithm that processes the combined data to extract individual velocity components, reducing the number of separate data sets required.
Solution Approach 2:
The patent introduces a reconstruction algorithm as an intermediary step that processes the combined acquired data to separate and extract velocity information along multiple directions. This computational intermediary enables the derivation of comprehensive multi-dimensional velocity information from a single combined acquisition, avoiding the need to manage and process multiple separate data sets.
3Measurement precision
If traditional phase-contrast MRA methods are used, then velocity encoding is achieved, but the scan time increases with the number of dimensions
Solution Approach 1:
The patent combines velocity encoding along multiple directions into a single acquisition by applying gradient pairs with different orientations during one readout period. This merging of encoding operations maintains the accuracy of velocity measurement while reducing the total scan time, as the combined data is processed through a reconstruction algorithm that efficiently extracts velocity components without requiring sequential acquisitions for each direction.
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 significantly reduces acquisition time for phase-contrast MR imaging, providing accurate velocity information with a 33% savings in 2D imaging and 25% savings in 3D imaging, while eliminating the need for multiple data sets, thus overcoming the limitations of traditional MRA techniques.
Implementation Method 1
Spins that are moving along the direction of a magnetic field gradient receive a phase shift proportional to their velocity. In the presence of velocity-encoding gradients, applied in multiple directions per readout using the plurality of gradient coils
Implementation Method 2
If, however, the substance, or tissue, is subjected to a magnetic field (excitation field B1; also referred to as the radiofrequency (RF) field) which is in the x-y plane and which 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 Mt, which is rotating, or spinning, in the x-y plane at the Larmor frequency
Data Source
AI summary
A system and method is provided for performing a phase-contrast imaging process to generate an image of a subject using a magnetic resonance imaging (MRI) system. With the MRI system, a set of reference projections of a subject is acquired having both stationary spins and non-stationary spins and a set of velocity-sensitive projections is acquired from the ROI that is encoded to be velocity sensitive along multiple directions per readout. For each projection of the set of velocity-sensitive projections, directional velocity components are determined and a phase-contrast image of the ROI is generated using the set of reference projections, the set of velocity-sensitive projections, and the directional velocity components.