MRI Introduction For Middle School Students

For middle school students, MRI could be introduced through basic science concepts, such as atoms and molecules. This introduction is by B. M. Damon.

What is MRI?
MRI stands for Magnetic Resonance Imaging. It is a way of using a big magnet (called a magnetic resonance imager) to make pictures of the insides of things - people, chicken eggs, fruit - just about anything you can think of.

Doctors use MRI every day to make pictures of people who have been injured or are sick. Scientists at the U of I also use MRI to study biology. In this project, you will join them in being the first people ever to use MRI to look at a chicken as it grows and develops inside of its egg.

Saggital Section
Figure 7. Side view of human head (Image courtesy of Dr. Andrew Webb.)

Everything that you see is made of things called atoms. An atom is like a very, very small solar system. As you know, the sun is at the center of the solar system. Just like the solar system, there is something at the center of an atom. It is called the nucleus. So the nucleus of an atom is like the sun in our solar system. Around the sun there are planets. They orbit the sun. In an atom, there are things called electrons that orbit the nucleus.

There are many different types of atoms. All of them are electric. The nucleus of an atom has a positive charge, while the electrons have a negative charge. Some atoms are also magnets. For example, a hydrogen atom is a magnet.

Two or more atoms joined together are called a molecule. For example, when two hydrogen atoms and an oxygen atom join together, they make a water molecule. Because the water molecule includes two magnetic hydrogen atoms, the water molecule is a kind of magnet, too.

This is very convenient for us, because things like chicken eggs have a lot of water molecules in them. There are water molecules in the yolk and there are water molecules in the egg white. So there are millions and millions of little water magnets swimming all around the inside of a chicken egg! When you make your MRI pictures, you are actually making a picture of those water molecules.

In your egg project, someone will take the egg and put it inside of the MRI magnet. You will then use your computer to make an image. In order to do that, the MRI magnet has to zap the little water magnets with some energy. It will do this over and over again. It may take as little as 10 or 12 seconds or as much as a couple of minutes to do this. Eventually, the MRI magnet will be done zapping and a computer will make an picture of the inside of the egg.

What will the picture look like?
The picture will be of a slice of the egg - sort of like if you slice through a hard-boiled egg with a knife. This picture will be a square, 60 mm by 60 mm (about 2 1/2 inches by 2 1/2 inches). We call these dimensions the field of view.

The water magnets in the yolk behave differently from the water magnets in the white. And so you might notice that the yolk is dark gray and the white is light gray. This really doesn't have anything to do with the color of the yolk and the white, though. You can change the contrast in the image to make the yolk lighter and the white darker. It is sort of like looking through red cellophane at an object, and then looking at the same object through blue cellophane. It looks different, but you are really just looking at two different aspects of the same thing. Of course, you will eventually be able to see a chicken developing - a pretty amazing thing.

So what else can you do?
Well, one thing that you can do is view the egg from different angles - like cutting through a hard-boiled egg sideways vs. crossways vs. lengthwise.

Another thing you can do is move the position of the slice forward or backward - like cutting through the egg in a different spot.

You can make the field of view smaller. This is like zooming in: it will make the egg bigger (but if you zoom in too much, it will make the images look weird - try it!). You can also make the field of view larger. This is like zooming out: it will make the egg smaller.

You can cut very, very thin slices - as thin as a millimeter - or very thick slices - as thick as a centimeter.

You can make the same image over and over and average them all. This will make a nice-looking image, but will take a while.

What should I do during the experiments?
You should explore the inside of the egg as much as possible. View the egg from different angles. Move the slice all around so that you can find different things. Zoom in. Zoom out. Try to make your images look as good as possible.

Don't be worried if the image turns out funny. Even the scientists at the U of I have to experiment with things a little (a lot, sometimes!) to get things to turn out right.

Most of all, you should have fun doing this science project. You will be doing something that no one has ever done before - making MRI pictures of a developing chicken egg. Seeing something for the very first time is the fun of science. Have fun in your experiments and discoveries!!

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