When Layla, a 7 and amp;frac12;-year-old Eastern Black Rhino, had a growth obstructing her nasal passageway, zoo veterinarians decided to give her a CT, or computerized tomography, scan. At 2,300 pounds, Layla was too heavy to move into the animal hospital at Brookfield Zoo outside Chicago so the vets at the Chicago Zoological Society put Layla in a portable CT scanner.