Imaging tests like CT scans and MRI and nuclear imaging are great tools because they allow doctors to see inside the body. But don't they also expose people to radiation?

And if so, isn't this a bad thing?

MRI

Yes.  And no.  Some imaging tests do expose people to radiation.  But just to be clear, MRI, which stands for magnetic resonance imaging, does not use radiation.  So if you have an MRI, there's no risk of exposure.

CT And CAT Scans

But other types of imaging tests do use radiation.  Like nuclear imaging, which is used to look for heart disease.  And CT, or CAT scans, which use x‑rays to take 3‑D pictures inside the body.

And, unfortunately, over time these tests do sometimes expose people to dangerously high levels of radiation.  High enough to cause cancer, in some cases.

But why would doctors order tests that put people at risk for getting cancer?

Risks And Benefits

Well, mainly because the tests are often very useful.  For example, mammography is the best way to look for early signs of breast cancer.

But it's not as clear that other tests, such as nuclear imaging, are as useful for detecting heart disease.  It may be, but there's not enough hard evidence to be certain.

It's not that people should always avoid these imaging tests.  But they should be aware of the risks.