The Christopher Wark beats cancer site is well worth reading for anyone who has cancer or is trying to help a friend with cancer.
One of the things I find quite a lot of friends get confused over is whether the dose of radiation one gets from a CAT (CT) scan is more or less than that from an MRI scan. In fact, CT scans are high-powered X-rays that expose patients to between ten and 100 times more radiation than a normal head or chest X-ray for example, and can potentially damage your DNA. Radiation treatments are apparently in the top five causes of secondary cancers for cancer survivors.
MRI scans on the other hand don’t expose you to radiation.
for more info.