Americans get more medical radiation than people anywhere else in the world. The average American's dose of radiation has grown six times as to what it was 10 years ago.

Experts say the increased use of computerized axial tomography scans and other advanced imaging are to blame.

It is hard to say how much radiation is risky to the human body.

Radiation is measured in units called millisivierts. Studies have shown that 50 to 150 millisievert units could be tied to an excessive risk of cancer.

An ordinary chest X-ray gives off up to one-tenth of a unit. But just one chest or abdominal CT scan involves 10 to 20 millisieverts.

Many times patients have been subjected to the more powerful X-rays, when other tests could be substituted.

In some cases, patients received nearly 15 or more CT scans over their lifetime. The government is working on plans to regulate radiation dosage.