From the blog "Mike at Medical Models"

In this entry we look at registering one scan to another from the same subject pre and post op.     There may come a time when you have multiple scans of the same subject which you want to compare to each other.  This could be a CT and an MRI or a pre and post op scan as in this example.  Since the scans were taken at different times and possibly different places they will not line up with each other when they are loaded.  Registration is the process that can find the tr