you get a mammogram, that's one whether it increases. for a chest ct scan, you get three years' worth. >> so this whole business about x-rays and cts, they're not kidding when they say there's a lot of radiation. >> more than what you naturally get, months and years' worth, they're compared with what you normally get walking around. but i want to underscore they're not considered dangerous levels. we're able to sustain that. it is increased but not to the point where -- unless you've had a lot of ct scans or x-rays in a short amount of time, shouldn't be concerned. >> let's talk about things that we can remember in terms of radiation damage. think about chernobyl. >> yeah. that's a worst-case scenario. we had mention it's three millie sieve erts a year. when you look at chernobyl, workers there were exposed, we're talking about 124 workers, exposed to levels between 800 and 16,000 millisieverts. >> so 3 is normal in a year? >> 3 is normal in a year.