I don't have an answer for you, Bobcat, but you might try <a href="http://www.auntminnie.com." target="_blank">www.auntminnie.com.</a> This is a really cool website for the radiologist-to-be. You can ask residents or practicing radiologists themselves and will probably get a better response.
I've been trying to figure out if there is any data on radiation exposure and effects in interventional fields. I haven't been able to find much at all. I think that its not something that people want to think about.
I think this is a very difficult thing to calculate and if you did find a source it would most likely be based on dubious data. Most IR rads I know have ceased wearing their badges so as not to call down the wrath of the radiation safety officer. I can tell you that the actuarial tables of insurance companies state there is no special risk to being a radiologist including IR. The thing we teach all rad residents is to be responsible with the radiation use. Wear your lead, understand x-ray physics principles and become good at what you do so you don't have to irradiate yourself or the patient more than necessary.