A 3D Quantification Technique for Liver Fat Fraction Distribution Analysis Using Dixon Magnetic Resonance Imaging

This study introduces a unique 3D quantification method for liver fat fraction (LFF) distribution using Dixon Magnetic Resonance Imaging (Dixon MRI). LFF maps, derived from in-phase and water-phase images, are integrated with 3D liver contours to differentiate LFF patterns between normal and steatotic livers, enabling precise assessment of liver fat content.

This study develops a 3D Dixon MRI technique to precisely quantify liver fat distribution, aiming to validate its efficacy as an accurate, non-invasive tool for assessing and differentiating fat patterns in normal versus steatotic livers. Recent advances in MRI fat quantification include normal 3D distribution modeling approaches integrating Dixon imaging with liver structure segmentation to enable precise visualization and measurement of liver fat fraction patterns. Integrating AI-driven medical imaging, deep learning, 3D visualization, and a multimodal data fusion enhances whole liver modeling and steatotic assessment, facilitating precise clinic decision-making.

Current experimental challenges include standardizing computational workflows, addressing variations in equipment and the protocols, and elucidating the mechanisms of disease progression in hepatic steatosis research. Our protocol offers the advantage of 3D liver fat fraction assessment, surpassing the 2D techniques. The findings will advance research in our field by offering a comprehensive and accurate 3D LFF assessment of different stages of fatty liver disease, which is crucial for treatment decisions and the prognosis evaluation.

To begin checking the Dixon sequence for the upper abdomen, create a customized working directory and copy all DICOM data to the created directory. Then go to the directory housing the data within MATLAB's current working directory. Change the directory to access folders for different phases, like in-phase, out-phase, water, and fat phases.

Utilize the Slice_View function to view the image for each phase. Use the MRI Dixon in-phase sequence to enhance descriptions of liver tissue boundaries. Right-click on the color bar and select the option from the pop-up menu to switch to the standard gray color map and reset the entire GUI.

After zooming the image appropriately, use the Mark Pixel Coordinates feature to calculate the distance between two points, aiding in the measurement of nodule sizes. Employ the scroll bar situated at the bottom of the graphic user interface or GUI to navigate through the various sequences efficiently. If the default filter window is not suitable, adjust it by dragging it up and down in the middle of the figure using the left mouse button to modify the window level.

To begin extracting the 3D region of the liver from the Dixon MRI data, open the Mimics software and choose New Project. In the subsequent dialogue box, locate the folder housing the Dixon out-phase images. Click on Next, then click on Continue, and then hit Convert to enter the sequence editing mode.

Click on New within the Mask dialogue box situated on the right-hand side to generate an empty mask and opt for the maximum threshold. Use the Edit Masks tool located under the Segment label to delineate the liver area in all horizontal views. Choose the liver mask depicted earlier and click on Calculate Part from the mask to create a 3D spatial representation of the liver.

Navigate to File, then select Export, and choose the DICOM option. In the pop-up dialogue box, select the liver mask, specify the file path and names, and then click on OK to export the 3D liver region to the designated DICOM files. Change the directory to the folder of in-phase images and select the Volume_In function to generate the in-phase volume.

Change the directory to the folder of water-only images and select the Volume_Water function to generate the water-only volume. Select the FF_Volume function and use the two volumes previously generated as inputs to obtain the FF volume of the abdominal MRI. Utilize the LFF function, providing it with the 3D liver region and the liver stiffness map as input parameters.

Run the LFF_Distribution function using the identical input parameters as LFF_Volume to produce the spatial distribution of the 3D liver fat fraction. Fusing the 3D liver contour with the 2D FF map generated an integrated 3D FF distribution model. This revealed fat fraction values at different liver positions, enabling precise measurement of the proportion of the liver at various steatosis levels.

Comparison between a normal and fatty liver, validated the technique's ability to discern different 3D LFF distribution patterns.