Q: Is there some way to better explain what the images are actually of? A more precise explanation of where we are looking on the egg? [Question submitted by a group of high school Chickscope students]

A: I assume you mean that it is difficult to interpret the images. That's certainly true, especially if you only look at one at a time. You need to consider how various structures would look if sliced in different ways, then look for them in the other planes. Discard images that are obviously corrupted by motion. It takes a lot of patience. Looking at the chick as it develops helps some, since it gives you an idea of how big things should be, or whether they are bright or dark. To put this in perspective, radiologists (doctors who look at x-rays and MRIs every day) spend years practicing, looking at thousands of films, before they make any diagnoses on their own. And the subjects of their pictures are generally cooperative (people will turn sideways if you ask them to, for example, or hold still). And they use very standardized poses for getting the images. The chicken doesn't understand that. So your job is actually harder, and you have had less practice.

A possible classroom exercise:

Make a montage of images, one from each day, at the same location in the egg. A good start would be side views at offset 0. Make sure each picture has the same field of view (same scale). Use the database to create the montage, then print it out.

For more advanced students, estimate the relative volumes of the various compartments (albumen, yolk, amnion) and make graphs (volume vs. time). The volume can be estimated crudely by tracing the pictures onto graph paper and counting squares; by cutting out the compartments with scissors from a printout, and weighing the individual pieces (good balance needed for this); or with computer software such as NIH Image that allows measurements on the screen. For really advanced students, repeat the measurement above using several slices at different positions and summing for each compartment to get an "integrated" volume. (Good for calculus students.) This should be a bit more accurate.

Please check out the MRI Database for images.