Fat Suppressed Diffusion MRI Using Reference Image Segmentation
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Solution Overview
Problem
Current fat suppression methods in diffusion MRI suffer from reduced signal-to-noise ratio (SNR) and increased scan time, particularly when using high SENSE reduction factors required for geometrically accurate EPI, and are not compatible with multi-echo time DIXON algorithms.
Innovation Solution
A fat suppressed diffusion image determination apparatus and method that utilize a diffusion reference image to determine a fat image independently of diffusion encoding, allowing for fat suppression in diffusion weighted MR images without additional acquisitions, thereby maintaining SNR and reducing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spectral fat suppression methods (SPAIR, STIR) are used in diffusion MRI, then fat signal is suppressed, but signal-to-noise ratio (SNR) is reduced
Solution Approach 1:
The method segments the fat suppression process from the diffusion-weighted imaging sequence by using a separate diffusion reference image (b=0) to generate a fat map, which is then applied to the diffusion-weighted images. This allows fat suppression without requiring spectral pulses within the DWI sequence itself, preserving SNR while achieving fat suppression.
Solution Approach 2:
The fat map is determined in advance from the diffusion reference image before processing the diffusion-weighted images. This preliminary fat suppression preparation allows the actual diffusion-weighted images to be processed without additional fat suppression pulses, maintaining their original signal quality and SNR.
2Object-affected harmful factors
If multi-echo time DIXON algorithm is applied to diffusion imaging, then water and fat signals are separated, but echo time is extended and SNR is reduced
Solution Approach 1:
The method extracts the fat suppression function from the multi-echo DIXON sequence by using only the diffusion reference image to create a fat map, which is then subtracted from the diffusion-weighted images. This extracts the essential fat suppression capability without requiring multiple echo times, thus avoiding the SNR penalty associated with extended echo times.
3Object-affected harmful factors
If multiple acquisitions at different echo times are performed for DIXON DWI, then fat suppression is achieved, but scan time is increased by up to 3 times
Solution Approach 1:
The diffusion reference image (b=0) serves multiple functions: it provides the anatomical reference for diffusion weighting calibration and simultaneously serves as the source for generating the fat map through subsequent fat suppression processing. This multi-functionality eliminates the need for separate fat suppression acquisitions, maintaining scan efficiency.
4Object-affected harmful factors
If SENSE algorithm is applied to generate water and fat resolved images from single shot EPI, then fat suppression is achieved, but SNR degradation occurs due to g-factor effects
Solution Approach 1:
The method creates a copy of the fat signal information from the diffusion reference image to generate a fat map, which is then subtracted from the diffusion-weighted images. This copying approach avoids the direct application of SENSE reconstruction to separate water and fat, thereby avoiding the g-factor induced SNR degradation while still achieving fat suppression.
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
Enables robust fat suppression in diffusion MRI with improved SNR and scan time trade-off, eliminating the need for additional fat image acquisitions and reducing geometric distortion, even with high SENSE reduction factors.
Implementation Method 1
One approach to fat suppression in diffusion MRI is to exploit the chemical shift between fat and water using spectrally-selective pulses
Implementation Method 2
Image-forming MR methods which utilize the interaction between magnetic fields and nuclear spins in order to form two-dimensional or three-dimensional images
Data Source
AI summary
A fat suppressed diffusion image determination apparatus, a corresponding method and a corresponding computer program determine a diffusion weighted magnetic resonance image (DWI) of an object. The fat suppressed diffusion image determination apparatus includes a diffusion reference image providing unit for providing a diffusion reference MR image of the object, a fat image determination unit for determining a fat image from the diffusion reference MR image, a diffusion weighted image providing unit for providing a diffusion weighted MR image of the object, a fat suppressed image determination unit for determining a fat suppressed diffusion weighted MR image using a combination of the diffusion weighted MR image and the fat image.