MRI Susceptibility Map Reconstruction via Positive and Negative Signal Separation
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Solution Overview
Problem
Conventional MRI techniques lack a reliable method to distinguish and determine the distribution of materials with susceptibility greater than or less than that of a reference material, such as water, within a measurement target, leading to difficulties in separating positive and negative susceptibility sources coexisting in the same voxel.
Innovation Solution
The proposed MRI data processing method uses equations to calculate the positive and negative contribution levels for susceptibility in each voxel, employing functions that account for the phase and magnitude of the MRI signal to separate the distribution of materials with higher and lower susceptibility than the reference material, utilizing dipole and magnitude relaxation kernels to reconstruct susceptibility maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI techniques are used to measure susceptibility, then the overall susceptibility value can be obtained, but the distribution of materials with positive and negative susceptibility cannot be distinguished
Solution Approach 1:
The patent segments the susceptibility measurement into two distinct components: positive susceptibility sources and negative susceptibility sources. By introducing separate calculation equations (Equation 1 for positive, Equation 2 for negative) and using sign-based classification of frequency shift values, the method divides the原本 unified susceptibility measurement into distinguishable parts, enabling separate mapping and analysis of different material types while maintaining overall measurement precision.
2Adaptability or versatility
If the measurement target contains both positive and negative susceptibility materials, then the susceptibility measurement becomes complex, but the conventional methods cannot separate the two types of materials
Solution Approach 1:
The patent applies an inversion approach by classifying frequency shift values into positive and negative groups, then inverting the conventional single-equation approach into two separate equations. Equation 1 calculates positive susceptibility contributions from positive frequency shifts, while Equation 2 calculates negative susceptibility contributions from negative frequency shifts. This inversion of the measurement paradigm enables clear separation of mixed susceptibility materials that conventional methods cannot distinguish.
3Ease of manufacture
If a single susceptibility map is generated, then the processing is simple, but the detailed distribution information of different susceptibility sources is lost
Solution Approach 1:
The patent adds a dimensional distinction to susceptibility mapping by creating separate maps for positive and negative susceptibility sources. Instead of a single-dimensional susceptibility value, the method generates two-dimensional information: a first susceptibility map for positive sources and a second susceptibility map for negative sources. This dimensional expansion preserves processing simplicity while significantly improving the accuracy and detail of susceptibility distribution information.
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 effectively separates and reconstructs susceptibility maps, accurately distinguishing between materials with positive and negative susceptibility, improving upon conventional methods by providing detailed distribution information of both types of susceptibility sources within the measurement target.
Implementation Method 1
A material may have a physical property called susceptibility (magnetic susceptibility), and its value may vary for each substance. When a material is placed in a magnetic field, if the magnetization of the material is aligned along the direction of the magnetic field, the susceptibility of the material may be defined as having a positive value. Conversely, when the magnetization of the material is aligned along the opposite direction of the magnetic field, the susceptibility of the material may be defined as having a negative value.
Implementation Method 2
MRI is based on nuclear magnetic resonance (NMR). Some nuclei may absorb and release radio frequency energy when placed in an external magnetic field. Hydrogen atoms are naturally abundant in the anatomy to be tested and are most often used to generate radio frequency signals.
Implementation Method 3
a first value regarding a frequency-shift value, which is a difference value between a resonance frequency of the MRI signal measured from the measurement target and a basic resonance frequency, is calculated; when a first dependent variable y1 of a first function f1 having a positive contribution level for susceptibility as a first independent variable and a negative contribution level for susceptibility as a second independent variable has the first value
Data Source
AI summary
Provided is an MRI data processing method for determining a positive contribution level for susceptibility by more than one or more different materials with susceptibility greater than the susceptibility of the reference material and a negative contribution level for susceptibility by one or more different materials with susceptibility smaller than the susceptibility of the reference material. The method includes calculating a first value regarding the frequency of the MRI signal of the measurement target, obtaining a second value regarding a relaxation constant of the MRI signal, and finding the solutions of the first independent variable and the second independent variable when the first dependent variable of the function having the positive contribution level for susceptibility as a first independent variable and the negative contribution level for susceptibility as a second independent variable has the first value and the second dependent variable of the function has the second value.