# Why is barium used instead of bismuth as a contrast in gastrointestinal xrays?

Why is barium used instead of bismuth as a contrast in gastrointestinal x-rays? Bismuth is a heavy metal that has a relatively low toxicity in comparison to barium. Is there a particular property of barium that makes it a better contrast? Is it less expensive?

• I’d suggest looking at Wikipedia on ‘radiocontrast agents’. It has a very good reason given there. – Jon Custer Mar 28 at 22:04

Yes, but no so much that it would be favored, i.e. you don't worry about saving \$5 when your doing a \$5000 procedure.