Many people will eventually face the need of an MRI scan for some sort of medical diagnosis, including those with tattoos. Some are told that getting a tattoo would impede their ability to get an MRI scan if the need arose. But it's time to lay this question to rest.
In order to understand the interaction between MRI and tattoos, it's important to understand how an MRI works. Magnetic Resonance Imaging (MRI) technology creates images of the inside of our bodies in the form of very thin “slices,” through a combination of a powerful magnetic field and radio frequency pulses. When used in tandem, these pulses send signals from the MRI machine to our body and then back to a computer, which creates an image out of the data. An MRI can be necessary in diagnosing anything from a slipped disc to early stages of stroke.
(For a more detailed description of MRI technology, this howstuffworks.com guide is helpful.)
It's the magnetic force that is a cause for concern, not only to those who are tattooed but also to anyone with metal objects in their bodies such as implants or pacemakers. The magnetic force of an MRI machine is so strong, even the “weakest” machine used is 10,000 times the strength of the Earth’s magnetic field. Even small metal objects, like paperclips and keys, become projectile weapons if left in an MRI room during a scan.
So, how does this apply to tattoos? Well, up until 20 years ago, tattoo ink was heavily unregulated—and therefore sometimes contained small fragments of metal. Some MRI patients who have had tattoos that dated back far enough to have received ink that contained metal bits have reported pain during an MRI scan, ranging from slight to severe.
There are a few reasons this could be. One theory is that the magnetic force pulls on the metallic fragments so violently that it causes a burning sensation in the location of the tattoo. Another is that the pain is caused by built up friction between the particles. Some people even say that the magnetic force causes the metal fragments to tear at the skin in an attempt to break through. There's no conclusive evidence as to which theory is correct.; however, even if there is no pain at all, these fragments can cause distortions in MRI scans.
These distortions, called artifacts, can render a scanned image useless. In turn, this will require that the procedure be done again, or even an alternate procedure be used. So, at the very least, you could be stuck with a very expensive bill for nothing if your tattoo contains metal.
How can you know if your tattoo contains metal? Short answer: you can't, really. Thankfully, due to implemented regulations, you can be pretty sure that if you got your tattoo within the past 20 years it's safe. Even if you got inked more than 20 years ago, however, that doesn’t mean the ink contains metal. And even if it did, that doesn't always mean you'll have a problem getting an MRI. If you find yourself at this juncture, it's best for you to inform your doctor, and let them help you make an informed decision.
Remember that there are always alternatives to MRI—people with pacemakers and metal implants also have to find other diagnostic methods. Your doctor will help you decide if you might be at risk and, if you are, what alternate option is right for you.