Spin-Echo MRI Velocity Encoding for Flow Artifact Suppression
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Solution Overview
Problem
Conventional MRI technologies struggle to effectively suppress flow artifacts caused by varying velocities and directions of arterial and venous blood flows, leading to incomplete suppression of artifacts despite adjustments in flow compensation pulses.
Innovation Solution
The MRI apparatus employs a spin echo-based pulse sequence with varying intensities of gradient magnetic field pulses before and after a 180-degree pulse, encoding velocity information in measurement data, and performs Fourier transformation in the velocity encoding direction to reconstruct an image free from flow artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If flow compensation pulses are adjusted to suppress flow artifacts, then image quality may improve, but the suppression is incomplete for blood flow with varying velocities and directions
Solution Approach 1:
The patent applies velocity encoding by changing the intensity parameters of gradient magnetic field pulses before and after the 180-degree pulse. By varying these gradient intensities, the system encodes different velocity information into the measurement data, enabling differentiation between stationary tissues and blood flow with various velocities and directions.
Solution Approach 2:
The patent introduces a velocity encoding dimension by adding gradient pulses that encode velocity information along with the spatial encoding dimensions. This creates an additional encoding axis (velocity encoding axis) that allows separation of signals based on tissue velocity, effectively adding a new dimension to the traditional spatial encoding framework.
2Object-affected harmful factors
If conventional flow suppression techniques are applied, then some flow artifacts are reduced, but artifacts from arterial and venous blood with different flow characteristics remain
Solution Approach 1:
The patent uses varying intensities of gradient magnetic field pulses to encode a range of velocity values. This allows the system to capture and differentiate signals from blood flow with different velocities (arterial vs. venous) and directions, providing universal suppression capability across diverse flow characteristics without requiring separate techniques for each vessel type.
Solution Approach 2:
The velocity encoding approach provides a universal solution that handles multiple types of blood flow (arterial, venous, different velocities, different directions) through a single mechanism. The gradient pulse intensity variation creates a comprehensive encoding scheme that adapts to various flow conditions without requiring separate specialized techniques.
3Object-affected harmful factors
If velocity encoding is implemented through gradient magnetic field pulses, then flow artifact suppression is achieved, but measurement complexity increases
Solution Approach 1:
The patent segments the gradient magnetic field application into distinct components: pre-180-degree gradient pulses for velocity encoding and post-180-degree gradient pulses for additional velocity encoding and spatial encoding. This segmentation allows each gradient component to have a specific function, making the complex pulse sequence more manageable and interpretable while achieving comprehensive velocity encoding.
4Loss of information
If multiple gradient magnetic field pulses with varying intensities are applied, then velocity information is encoded, but measurement time increases
Solution Approach 1:
The patent employs periodic application of gradient magnetic field pulses with varying intensities in a structured sequence. The gradients are applied periodically at specific intervals (before and after the 180-degree pulse) rather than continuously, which allows velocity encoding while maintaining a manageable measurement time through rhythmic, structured pulse application.
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 a flow artifact-free image by separating signals from stationary tissues, excluding signals from fluids like blood, thereby 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
In MRI using an SE-based pulse sequence, an object is to suppress flow artifacts and acquire a flow artifact-free image regardless a velocity or a direction of blood flow. A pair of gradient magnetic field pulses are applied before and after a 180-degree pulse of the SE-based pulse sequence, and a plurality of times of imaging are performed using varying intensities of the pair of gradient magnetic field pulses. Image reconstruction is performed by performing a Fourier transformation on measurement data obtained through the plurality of times of imaging in an axial direction of the intensities of the gradient magnetic field pulses, that is, a velocity encoding direction. As a result, images can be separated for each velocity of a stationary tissue and a non-stationary component included in tissues, and an image of spins with a velocity of zero, that is, a flow artifact-free image of the stationary tissue, can be obtained.