Δαφνη Ευτυχια Αρθουρος

Well, it is disc-shaped, but it's a _much_ thicker disc; more of a squat cylinder. And the actual volume that an MRI could read data from is even bigger; it's just a non-uniform field outside of that volume. The easiest way to deal with that for normal MRIs is to ignore data outside the uniform field volume, but you could probably correct for the distortion if you needed to (say, to track a moving cat...).

[edit: to/too blunder. Bah. Why do I even pretend to speak English?]