Fat-Water Separation in MRI

A figure from Dixon's original paper on fat-water separation.

A figure from Dixon’s original paper on fat-water separation.

To anyone who is interested in fat-water separation within the field of MRI, I offer the following (click for PDF):

Fat-Water Separation

This is a chapter from my master’s thesis that explains the most common methods of fat-water separation and presents a very handy geometric interpretation of two-point Dixon imaging. I’ve been told that the interpretation is very helpful for newcomers to the field.

If you find it useful at all, please share it.

What is fat-water separation, you might ask?

Good question.

MRI detects hydrogen atoms; and there are two main places in your body where hydrogen atoms hang out: fat molecules and water molecules. So in the context of MRI, we can say that most tissue in your body is either fat or water. (Examples of “water” here include muscle, blood, skin, and pretty much anything except fat.) Fat-water separation is simply the process of distinguishing between the two tissue types in an MRI image.

Doctors often want either to remove the fat from an image so they can see things the fat might be hiding, or to create two separate images, one of fat only and one of water only. Doing so can help them give patients a more accurate diagnosis.

Fat-water separation techniques involve some interesting physics and math. For more info, click on the link provided above.

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