MRI Diffusion Weighted Imaging Using Estimated Motion Probing Gradient B-Factors

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Solution Overview

Problem

Current magnetic resonance diagnostic techniques face challenges in obtaining high diffusion weighted contrast images without deteriorating the signal-to-noise ratio (SNR) or increasing motion artifacts, as higher b-factors require increased maximum gradient magnetic field intensity or longer echo times, which are costly and inefficient.

Innovation Solution

A magnetic resonance diagnostic apparatus and method that derive an apparent diffusion coefficient from multiple images taken with different b-factors and estimate pixel values using these coefficients, allowing for the generation of images with higher b-factors without the need for increased gradient magnetic field intensity or extended echo times.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the time δ for applying MPG pulse is increased to increase the b-factor, then the diffusion weighted contrast becomes stronger, but the TE (echo time) becomes extended, causing SNR (signal-to-noise ratio) to deteriorate and motion artifact to increase

Engineering Contradiction:

Improvediffusion weighted contrastVSAvoidSNR (signal-to-noise ratio)

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary motion correction by estimating motion parameters from the acquired images before generating the final diffusion weighted image. Motion probing gradients are applied to encode motion information, and motion parameters are estimated from these encoded images to correct the diffusion weighted image, thereby preventing motion artifacts from degrading image quality while maintaining the benefits of higher b-factors

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where motion parameters are continuously estimated from the acquired images and used to adjust and correct the diffusion weighted image. The motion estimation process provides feedback about patient motion, which is then used to refine the final image quality, creating a closed-loop system that maintains high contrast while compensating for motion effects

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the time δ for applying MPG pulse is increased to increase the b-factor, then the diffusion weighted contrast becomes stronger, but motion artifact increases

Engineering Contradiction:

Improvediffusion weighted contrastVSAvoidmotion artifact

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

Motion correction is performed preliminarily by estimating motion parameters from images acquired with motion probing gradients before generating the final diffusion weighted image. This preliminary motion characterization allows the system to compensate for motion effects while maintaining high b-factor settings for improved diffusion contrast

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful effect of patient motion during scanning into useful information by applying motion probing gradients that encode motion data into the acquired images. This motion information is then extracted and used to correct the diffusion weighted image, transforming the previously harmful motion artifact into a corrective signal that improves overall image quality

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If maximum gradient magnetic field intensity G is increased to obtain a large b-factor while maintaining a constant TE, then the hardware performance of the gradient magnetic field system must be improved, which requires the cost to increase

Engineering Contradiction:

Improvediffusion weighted contrastVSAvoidhardware performance requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent creates a virtual high b-factor image by computationally processing multiple images acquired at lower b-factors. Instead of physically increasing the gradient strength to achieve high b-factors, the system uses motion correction and image processing algorithms to generate the equivalent of a high b-factor image from lower b-factor data, thereby avoiding costly hardware upgrades

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical approach of increasing gradient magnetic field intensity with a computational approach using motion correction algorithms and image processing. Instead of upgrading the physical gradient system hardware, the system uses software-based motion estimation and correction techniques to achieve the same goal of improved diffusion contrast at lower cost

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9031635B2MRI diffusion weighted imaging with estimated motion probing gradient b-factors based on acquired apparent diffusion coefficients for each pixel

Publication Date: 2015.05.12 TOSHIBA MEDICAL SYST CORP

AI summary

A magnetic resonance diagnostic apparatus includes a derivation unit to derive an apparent diffusion coefficient regarding a pixel position for each pixel position included in a region of interest in at least two original images obtained by imaging a same imaging region of a same subject using at least two b-factors that are different from each other, respectively, based on pixel values of each of at least two original images regarding the pixel positions, and a first estimation unit to estimate a pixel value obtained by using a b-factor that is different from the at least two b-factors, regarding each pixel position included in the region of interest, based on the apparent diffusion coefficient derived for each pixel position.