Magnetic Resonance Gradient Correction With Isotropic Liquid Phantoms
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Solution Overview
Problem
Existing magnetic resonance imaging (MRI) systems face challenges in accurately correcting gradient magnetic field strengths due to strict requirements on the geometry and position of the water phantom, leading to inaccurate image and parameter corrections.
Innovation Solution
A method for determining magnetic resonance gradient correction compensation factors using isotropic liquid-filled phantoms, where diffusion gradients are applied in orthogonal directions to calculate diffusion coefficients, allowing for accurate gradient correction factors independent of phantom position and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a completely spherical water phantom is placed strictly at the center of the main magnet for gradient correction, then the measurement precision of gradient magnetic field strength is improved, but the device complexity and operation difficulty increase due to strict requirements on phantom geometry and positioning
Solution Approach 1:
The patent changes the physical state parameter from solid water phantom to liquid-filled phantom, and utilizes diffusion coefficient measurement instead of geometric measurement. This parameter change eliminates the need for precise spherical geometry and positioning, as the liquid diffusion properties are intrinsic and independent of phantom shape or location.
Solution Approach 2:
The patent replaces the mechanical measurement system (geometric analysis of water phantom images) with a physical property measurement system (diffusion coefficient measurement). By measuring the diffusion coefficient of liquid in the phantom under diffusion gradients, the system obtains gradient correction factors without relying on mechanical positioning accuracy or phantom geometry.
2Measurement precision
If a completely spherical water phantom is placed strictly at the center of the main magnet, then the measurement precision is improved, but the ease of operation deteriorates due to difficulty in guaranteeing high accuracy in actual imaging process
Solution Approach 1:
The patent changes from solid water phantom to liquid-filled phantom, utilizing the intrinsic diffusion properties of liquids. This eliminates the need for precise positioning and spherical geometry, making the phantom easy to prepare and place anywhere in the imaging space where gradient linearity is maintained.
Solution Approach 2:
The liquid phantom serves itself by utilizing its own diffusion coefficient as the measurement basis. The diffusion coefficient is an intrinsic property of the liquid that does not depend on external factors like phantom shape, size, or position. This self-service approach eliminates the need for external calibration objects or precise positioning procedures.
3Measurement precision
If traditional water phantom imaging method is used, then gradient correction can be performed, but the productivity decreases due to time-consuming process and low accuracy
Solution Approach 1:
The patent replaces time-consuming image acquisition and geometric analysis with rapid diffusion coefficient measurement. By applying diffusion gradients and measuring signal decay based on intrinsic liquid diffusion properties, the system obtains accurate correction factors much faster, improving productivity without sacrificing precision.
Solution Approach 2:
The patent changes the measurement parameter from image geometric dimensions to diffusion coefficient. This parameter change enables faster measurement since diffusion coefficients can be calculated directly from signal intensity ratios without requiring complex image processing, thereby increasing productivity while maintaining high accuracy.
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
Improves the accuracy and efficiency of gradient correction by calculating precise compensation factors, reducing the need for precise phantom positioning and simplifying the correction process.
Implementation Method 1
the gradient coil can generate a gradient magnetic field in the imaging space
Implementation Method 2
The main magnet can generate a main magnetic field in an imaging space
Implementation Method 3
the radio frequency coil can generate radio frequency pulses in the imaging space
Implementation Method 4
acquiring axis direction magnetic resonance signals of a phantom for respective axis directions when diffusion gradient is applied to a gradient coil in each of the axis directions
Data Source
AI summary
A method for determining a magnetic resonance gradient correction compensation factors, comprising: obtaining axial magnetic resonance signals when a mold applies a diffusion gradient to a gradient coil in different axial directions and a reference magnetic resonance signal when no diffusion gradient is applied to the gradient coil (S202); determining diffusion coefficient calculation values of a liquid in different axial directions according to the axial magnetic resonance signals and the reference magnetic resonance signal (S204); and determining, according to the diffusion coefficient calculation values of the liquid in different axial directions and a reference diffusion coefficient, gradient correction compensation factors of corresponding axes (S206). The mold is a mold filled with the liquid, and the liquid is isotropic. Also disclosed are a magnetic resonance gradient correction method and an apparatus.