MRI Flow Artifact Suppression via Velocity Encoding
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Solution Overview
Problem
Current MRI technologies struggle to effectively suppress flow artifacts caused by blood flow velocity and direction variations, leading to incomplete suppression of artifacts even with adjusted flow compensation pulses, and extend the echo time in imaging processes.
Innovation Solution
An MRI apparatus and method that employs a gradient echo-based pulse sequence with a pair of gradient magnetic field pulses of opposite polarities and varying intensities to encode velocity information, allowing for Fourier transformation in the velocity encoding direction to separate and exclude signals from non-stationary tissues like blood, thereby reconstructing artifact-free images without extending the echo time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If flow compensation pulses are added to suppress flow artifacts, then flow artifact suppression is improved, but the echo time is extended
Solution Approach 1:
The patent changes the parameters of gradient magnetic field pulses by applying pairs of pulses with opposite polarities and varying intensities. This allows encoding velocity information into the measurement data without extending the echo time, as the velocity encoding is achieved through parameter modulation rather than adding separate compensation pulses
Solution Approach 2:
The patent introduces velocity encoding as an additional dimension by applying gradient pulses with varying intensities and performing Fourier transformation in the velocity encoding direction. This separates stationary tissue signals from flowing blood signals in the frequency domain, achieving flow artifact suppression without time extension
2Object-affected harmful factors
If flow compensation pulses are adjusted to suppress arterial blood flow artifacts, then arterial flow suppression is improved, but venous blood flow artifacts remain
Solution Approach 1:
The patent applies dynamic gradient magnetic field pulses with varying intensities rather than fixed compensation pulses. By changing the intensity parameters of the gradient pulses, the system can encode velocity information for different flow velocities, making it adaptable to both arterial and venous blood flow conditions
Solution Approach 2:
The patent uses periodic application of gradient pulse pairs with opposite polarities at different intensities. This periodic action with varying parameters enables encoding of velocity information across different blood flow conditions, allowing comprehensive suppression of flow artifacts from both arterial and venous blood
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 the acquisition of flow artifact-free images by encoding velocity information into measurement data, allowing for the separation of stationary tissue signals and effectively suppressing artifacts without prolonging the echo time, thus improving image quality.
Implementation Method 1
nuclear magnetic resonance signals generated from an examination target are collected through nuclear magnetic resonance
Implementation Method 2
adding information for encoding a velocity of a non-stationary tissue to measurement data and performing Fourier transformation for a velocity encoding axis
Data Source
AI summary
Provided is an MRI using a GRE-based pulse sequence in which flow artifacts are suppressed and a flow artifact-free image is obtained regardless a velocity or a direction of blood flow. A pair of gradient magnetic field pulses (velocity encoding gradient magnetic field pulses) is applied before echo measurement of a GRE-based pulse sequence, and imaging is performed a plurality of times by varying intensities of the velocity encoding gradient magnetic field pulses. Measurement data obtained by imaging a plurality of times is subjected to a Fourier transformation in an axial direction of the intensity of the velocity encoding gradient magnetic field pulse, that is, in a velocity encoding direction, to perform image reconstruction. As a result, an image can be separated for each velocity of a stationary tissue and a non-stationary component included in the tissue, and an image of spins with a velocity of zero, that is, a flow artifact-free image of the stationary tissue, can be obtained.