Radiologists almost never seek informed consent before beginning an x-ray or scan, and even when they make a stab at best practice, the patient is often not fully informed.
This is probably just as well because new data reveals that the patient who undergoes a full-body CT (computed tomography) scan is being exposed to a radiation level equivalent to that from the atomic bombs dropped on Hiroshima and Nagasaki. As a result up to one in 400 patients who are scanned will go on to develop a fatal cancer, and those unfortunate enough to have an annual CT scan increase their chances of a fatal cancer by between 16 and four times.

This falls well outside the limits of 'acceptable risk' - which was suggested by the UK's Royal Society to be 1 in 1,000 - and yet it's something that the radiologist rarely, if ever, mentions to the patient. Even at the level of acceptable risk, the Royal Society stresses that the individual should be fully aware of the risk, and that he received a commensurable benefit.
Unfortunately the CT scan in particular fails on that second point too. According to the Journal of the American Medical Association, CT scans have "long been controversial because of uncertainties surrounding their ability to detect hidden disease". In other words, they don't work very well.
So not only do you run an up to 1 in 25 risk of dying from cancer, you probably do so for no good reason.

The CT scan is not the only radiological screening to come with risks that many would consider to be unacceptable. Helical computed tomography causes fatal cancer in 1 in 1000 children (and this can be higher), and adults who have a thallium scintigraphy run a similar risk.
Unfortunately, most radiologists adopt the 'don't say a word' strategy with patients, a new report reveals. "Even for procedures with high radiation dose, there is no explicit or implicit mention of long term risks. The risk remains unheard by the patient and unspoken by the doctor," says Eugenio Picano from the National Research Council in Pisa, Italy. Why? Partly because the radiologist is too busy, says Picano, but also because of a paternalistic attitude that radiologist knows best.
Some others understate the risk, claiming the scan to be safe, and that millions are performed every year without incident. Only a handful states the full risk to the patient at which, presumably, the patient fetches his coat and leaves the surgery.

Perhaps it's something you should do the next time your local radiologist dives behind a lead screen, screaming 'Hiroshima' as he goes.