The problem: Some doctors recommend CT colonography, or "virtual colonoscopy," over the regular version because that allows patients to avoid having a tube inserted into the colon. But it requires ...

A virtual colonoscopy is doing a colonoscopy with an x-ray machine. Instead of a physician, a gastroenterologist using an instrument to go up into a colon, there's no instrument involved ...

The values are for fatal radiogenic cancers following a paired CT colonography procedure giving an effective dose of 8 mSv. Clearly, the values presented are less than those from ICRP (Table 2), ...