I wrote a little while back about radiation from nuclear sources and how to detect them. But what about getting voluntary radiation for medical procedures: like X-rays, CT scans, and MRI’s?

Annual background radiation

Did you know you’re getting about 3.00 mSv of radiation every year if you live in the US? This breaks down to about 0.0082mSv per day.

There’s actually quite a bit of variation in the US depending on where you live. The types of rock in your area, position relative to the planet’s poles, elevation, and wide variety of other factors can affect your daily background radiation dosage.

	Approximate effective radiation dose:	Comparable to natural background radiation for:
One day’s background radiation	0.0082 mSv	1 days
A year of background radiation (US average)	3.0 mSv	1 year/365 days
Cross-country flight from New York to Los Angeles	0.04 mSv	4.87 days

X-rays

X-rays are something most people are familiar with. It turns out, however, modern x-rays actually give you a very low dosage. The lowest doses are dental X-rays. For a full panoramic dental x-ray, you’ll get about 0.007 mSv (0.7mrem). How little is that? One full day’s background radiation is about 0.0066 mSv (depending on where you live).

Still, there does appear to be a link to dental X-rays and certain types of thyroid and laryngeal, parotid gland, and salivary gland cancers.

Moving up, a full chest X-ray gives you a 0.1mSv dose. That’s about 10 days worth of radiation.

MRI’s

MRI’s use magnetic imaging, so they do not use radiation at all. They use a very powerful rotating magnet to generate their images.

Is it perfectly safe? Well, MRI’s can be done with contrast to help identify certain issues, and those chemicals can carry risk. Chuck Norris’ wife (yes, the Chuck Norris) even filed a $10 million lawsuit when his wife experienced health issues from the contrast used in an MRI.

CT scans

CT scans are particularly troublesome because they actually give you a pretty substantial dose of radiation. How much? Ex: A chest X-ray gives you the equivalent of 10 days of natural background radiation (0.1mSv). This is a very low dosage and highly unlikely to cause permanent or long-term damage.

On the other hand, a chest CT scan gives you 2.6 YEARS of radiation dosage – the equivalent of 77 chest x-rays. See some examples below or click them to see even more dosages based on different body part:

If that wasn’t bad enough, CT’s often also involve the use of contrast chemicals that may carry their own risks.