As much as people would like to put labels on one cruise line, the treatment is very similar on other lines.
The Fantasy is an older ship that I haven't been on, and am unfamiliar with its infirmary. Certainly the infirmaries I've seen on other ships, across the boards, have x ray machines, and equipment to handle basic medical needs. They do have some limited medicines onboard.
Rich referred to dialysis. They have dialysis cruises, where the machines are brought onboard specifically for that cruise. It's not equiptment they have in their normal inventory.
I've perhaps unfortunately been witness to medical problems of friends on several cruises, from minor to quite serious, to some that proved fatal later. Probably 30% of the cruises I've been on have had medical emergencies onboard, where we had to change ports, return to ports, or have helicopter medivacs.
And not just Carnvial. In fact they are just as common on other lines. Elderly people often have more time and more money to cruise more often, and along with that go more incidence of medical emergancies.
I believe Holland America and Cunard ships carry 6 caskets onboard.
Princess (owned by Carnival Corp) I believe has communications abilities set up with US based ERs to be able to send lab results and other tests directly to get assistance.
What people should also know is the Drs. onboard are not employeed by the cruise lines. The medical facilities are outsourced on contract, much like the shops , and some other departments onboard.