MRI Diffusion-Weighted Image Computation for Tumor Contrast
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Solution Overview
Problem
Conventional MRI techniques face challenges in generating diffusion-weighted images with high contrast for tissues like tumors and nerves due to the limitations of b-value settings, leading to signal attenuation and mixing of ADC and T2 contrasts, making it difficult to accurately depict these tissues.
Innovation Solution
An MRI apparatus and image processing method that acquire multiple diffusion-weighted images with varying parameter settings, allowing for the computation of images with arbitrary b-values and effective echo times, thereby enabling the generation of images with enhanced contrast and reduced signal attenuation, specifically for tissues with short transverse relaxation times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a b-value around 1000 is used for diffusion-weighted imaging, then contrast between body tissues is enhanced, but the contrast is not sufficient for depicting malignant tumors and hardware limitations prevent using larger b-values
Solution Approach 1:
The patent applies parameter changes by acquiring diffusion-weighted images at multiple different b-values (e.g., b1, b2, b3) and then computationally combining these images to generate a final image with an arbitrary target b-value. This allows the system to overcome hardware limitations and produce images with b-values higher than what can be directly acquired, thereby enhancing tumor depiction capability while maintaining adaptability to different imaging requirements.
2Illumination intensity
If a b-value is set to a much larger value to enhance contrast for malignant tumors, then tumor visibility improves, but hardware restrictions prevent setting such large b-values
Solution Approach 1:
The patent uses copying by creating computational replicas of diffusion-weighted images acquired at different b-values. Instead of directly acquiring an image at a very high b-value (which hardware cannot support), the system acquires multiple images at lower, achievable b-values and computationally synthesizes an image that replicates what a high b-value image would show, thereby enhancing tumor visibility within hardware constraints.
3Adaptability or versatility
If multiple diffusion-weighted images are acquired with different parameter settings, then images with arbitrary b-values can be computed, but acquisition time and processing complexity increase
Solution Approach 1:
The patent applies partial action by acquiring diffusion-weighted images at a limited set of discrete b-values (e.g., three specific b-values) rather than continuously across all possible b-values. This partial sampling is sufficient to enable computational generation of arbitrary b-value images through interpolation, thereby reducing acquisition and processing time while maintaining the versatility to generate images at any desired b-value.
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 allows for the accurate depiction of tissues like tumors and nerves with strong signal intensity by avoiding signal attenuation and eliminating the influence of T2 contrast, thereby enhancing the visibility of ADC-based contrast in diffusion-weighted images.
Implementation Method 1
An MRI apparatus is an imaging apparatus configured to magnetically excite nuclear spin of an object placed in a static magnetic field with RF (Radio Frequency) pulses and generate an image by reconstructing MR (Magnetic Resonance) signals emitted from the object due to the excitation
Implementation Method 2
In DWI, a strong flow-encoding gradient magnetic field pulse called an MPG (Motion Probing Gradient) is applied. Application of an MPG pulse causes difference in MR signal intensity (i.e., contrast) between respective body tissues depending on difference in diffusion coefficient between those body tissues
Implementation Method 3
Degree of diffusion of each body tissue is indicated by an index called an ADC (Apparent Diffusion Coefficient). Further, as an index indicating intensity of an MPG pulse, a b-value (i.e., b-factor) is used
Data Source
AI summary
In one embodiment, an MRI apparatus includes: an MRI scanner configured to acquire N+1 or more diffusion-weighted images by differently setting parameter values among the diffusion-weighted images, with regard to N types of parameters, wherein N is a natural number equal to or more than two; and processing circuitry configured to generate a computed diffusion-weighted image having an arbitrary value for at least one of the N types of parameters, based on relationship between signal values of the acquired diffusion-weighted images and the parameter values differently set among the acquired diffusion-weighted images.