Move to images 6/9 and 7/9, and follow the same procedure for Terry. Remember you'll need to examine both his upper and lower slices and then do the following steps:

(1) Trace the outline of the lungs,
(2) measure the area of that polygon (don't click elsewhere in the image, or you'll have to re-draw the polygon!),
(3) threshold the polygon (set the Minimum at 249 and the Maximum at 255),
(4) measure the thresholded area, and
(5) record your answers.
Does Terry have emphysema?
No, because his total dead air area was only 2%.
Yes, because his percentage of dead air was around 30%, and the cutoff is 15%.
It's hard to tell because his lungs show 16% dead air. That's so close to the 15% cutoff that he should probably be re-tested.