MRI Susceptibility Calculation via Frequency Subtraction
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Solution Overview
Problem
Existing methods for calculating magnetic susceptibility distribution in MRI images require two separate calculations for each tissue type, leading to extended calculation times and potential inaccuracies, especially when detecting areas with small susceptibility changes.
Innovation Solution
An image processing device that separates specific tissue images and frequency images, subtracts frequency changes caused by tissues with large susceptibility, and converts these images to calculate a post-subtraction susceptibility image, allowing for accurate calculation of tissues with small susceptibility changes without significant increases in calculation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate calculations are performed for each tissue type (water and fat regions, or hemorrhage region and other areas), then measurement precision of magnetic susceptibility is improved, but calculation time is extended
Solution Approach 1:
The patent applies preliminary action by performing background field removal and frequency change calculation before the main susceptibility calculation. The background field is removed in advance, and frequency changes due to specific tissues (fat, hemorrhage) are calculated and stored prior to the final susceptibility mapping. This preprocessing allows the main calculation to focus only on the target tissue without repeated background corrections, thereby improving precision while reducing overall calculation time.
Solution Approach 2:
The patent segments the calculation process into distinct stages: background field removal, frequency image generation, specific tissue frequency change calculation, and final susceptibility calculation. By dividing the computation into modular segments that can be independently optimized and executed, the system achieves both high precision for different tissue types and efficient processing through parallel computation where possible.
2Manufacturing precision
If separate calculations are performed for each tissue type, then manufacturing precision of susceptibility distribution is improved, but device complexity is increased
Solution Approach 1:
The patent implements universality by creating a multi-functional calculation framework that handles different tissue types (water, fat, hemorrhage, calcification) using a unified approach. The same basic algorithmic structure is applied across all tissue types, with tissue-specific parameters and frequency changes as the only variations. This universal framework reduces the need for separate dedicated processing paths for each tissue type, thereby improving accuracy without proportionally increasing system complexity.
3Measurement precision
If frequency changes of specific tissue are not subtracted, then calculation time is reduced, but measurement precision of tissues with small susceptibility changes is lowered
Solution Approach 1:
The patent applies the extraction principle by isolating and removing the frequency changes attributable to specific tissues (fat, hemorrhage) from the total frequency image. By extracting these known frequency components and subtracting them, the remaining frequency changes can be accurately attributed to the target tissue with small susceptibility changes. This selective extraction and removal process enhances measurement precision while maintaining efficient processing through targeted computation.
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 high-accuracy magnetic susceptibility calculation for tissues with small susceptibility changes while maintaining efficient processing times, reducing errors and computational complexity.
Implementation Method 1
applies an RF magnetic field and a gradient magnetic field to a subject placed in a static magnetic field, measures signals generated from the subject in response to nuclear magnetic resonance
Implementation Method 2
a phase encoding gradient magnetic field and a readout gradient magnetic field, being perpendicular to the slice gradient magnetic field on the imaging slice, are applied, during the period from excitation until obtaining the echo
Implementation Method 3
an image is reconstructed by inverse Fourier transform
Implementation Method 4
a gray-scale image (phase image) having a phase as a pixel value, is an image on which a variation in magnetic field is reflected, caused by static magnetic field inhomogeneity, a magnetic susceptibility difference between living tissues
Data Source
AI summary
Magnetic susceptibility is calculated with high accuracy without significant increase of calculation time. Provided is an image processing device comprising an image processor for creating a susceptibility image representing a magnetic susceptibility of at least one tissue of the subject, from an image created on the basis of magnetic resonance signals generated from a subject, wherein the image processor includes an image separator configured to separate from the image, a specific tissue image representing a content of a predetermined specific tissue and a frequency image, an adder-subtractor configured to calculate a post-subtraction frequency image obtained by subtracting from the frequency image, frequency change caused by the specific tissue, and an image converter configured to calculate a specific susceptibility image representing the magnetic susceptibility of the specific tissue on the basis of the specific tissue image, and to calculate a post-subtraction susceptibility image on the basis of the post-subtraction frequency image.