CT scan and Barium Sulfate

I've been feeling a slight discomfort on my right side kidney area recently. Now that I'm being more sensitive (paranoid) about what my body is telling me, I went in to talk to the Urologist that removed my kidney stone last November.

He thought that I'd had a CT scan done then instead of just x-rays, but I did not. So we made an appointment for this to be done tomorrow morning at 7:30.

In about 10 minutes I have to drink 30 ounces of water or juice mixed with a "contrast" which is .8 oz of Baruim Sulfate. Then I can't eat or drink anything after midnight until the scan is done.

How much do you want to bet that this stuff I have to drink will taste nasty?

{Ed. Note I : Well it didn't taste too bad becasue I decided to mix it with cran-something juice instead of just plain water. The white chalky substance turned my red juice into a whitish-pink color. I have to keep shaking the container because the Barium Sulfate collects at the bottom of the container.}
{Ed. note II: I changed my mind. That is nnnaaaaaaasssstttttttyyyyyy stuff. So nasty in fact that I drank only half of it and poured the rest of it in the sink. If this messes up the scan oh well. I'd almost rather have another surgery than drink more of that crap. YUK!}

So what exactly is Barium Sulfate (BaSO4) and what does it do? Good questions all.

Barium sulfate is a radiopaque agent. Radiopaque agents are used to help diagnose certain medical problems. Since radiopaque agents are opaque to (block) x-rays, the areas of the body in which they are localized will appear white on the x-ray film. This creates the needed distinction, or contrast, between one organ and other tissues. The contrast will help the doctor see any special conditions that may exist in that organ or part of the body.

Barium sulfate is taken by mouth or given rectally by enema. If taken by mouth, it makes the esophagus, the stomach, and/or the small intestine opaque to the x-rays so that they can be "photographed". If it is given by enema, the colon and/or the small intestine can be seen and photographed by x-rays.

The dose of barium sulfate will be different for different patients and depends on the type of test. The strength of the suspension and tablet is determined by how much barium they contain. Different tests will require a different strength and amount of suspension (some may require the tablet form), depending on the age of the patient, the contrast needed, and the x-ray equipment used.

Barium sulfate is to be used only by or under the direct supervision of a doctor.

What I'd like to know is how "they" figured this out. What led these people to discover that this stuff actually helps with CT scans?