If a piece of metal were missed during your screening, it could cause a problem. Jewelry flying from your body and into the MRI machine is entirely possible. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close.
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Imagine being in this tube and having metal objects flying directly toward you or off of you. These mega-magnetic fields align the positively charged protons within the nuclei of the hydrogen atoms in the body's soft tissue. There are a lot of hydrogen atoms in soft tissue, because soft tissue is rich in H2O, aka water. The skin is about 64 percent H2O and the lungs are 83 percent, according to a paper in the Journal of Biological Chemistry. While they're lining up protons, MRI scanners also use radio waves to vary the magnetic field, forcing the protons to flip their alignment in response.
After the field turns off, the protons return to their usual orientation, which produces radio signals that the MRI machine can measure. The speed at which the protons return to normal is different depending on the tissue, so the radio signals produce an image that differentiates between muscles, organs and other structures.
It's that strong magnetic field that can prove dangerous if there's any metal in the room when the machine is switched on, as the magnet will yank metal objects toward it. Patients must remove any metal from their bodies before getting scanned; anyone with certain metal implants that can't be removed most older pacemakers, for example can't get an MRI scan.
Occasionally, metal objects brought into the room during scans cause tragic accidents. You will typically be asked to change into a gown and to remove things that might affect the magnetic imaging, such as:.
The MRI machine looks like a long narrow tube that has both ends open. You lie down on a movable table that slides into the opening of the tube. A technologist monitors you from another room. You can talk with the person by microphone. If you have a fear of enclosed spaces claustrophobia , you might be given a drug to help you feel sleepy and less anxious.
Most people get through the exam without difficulty. The MRI machine creates a strong magnetic field around you, and radio waves are directed at your body. The procedure is painless. You don't feel the magnetic field or radio waves, and there are no moving parts around you. During the MRI scan, the internal part of the magnet produces repetitive tapping, thumping and other noises.
You might be given earplugs or have music playing to help block the noise. In some cases, a contrast material, typically gadolinium, will be injected through an intravenous IV line into a vein in your hand or arm.
The contrast material enhances certain details. Gadolinium rarely causes allergic reactions. An MRI can last anywhere from 15 minutes to more than an hour. You must hold still because movement can blur the resulting images. During a functional MRI , you might be asked to perform a number of small tasks — such as tapping your thumb against your fingers, rubbing a block of sandpaper or answering simple questions.
This helps pinpoint the portions of your brain that control these actions. A doctor specially trained to interpret MRI s radiologist will analyze the images from your scan and report the findings to your doctor. Your doctor will discuss important findings and next steps with you. An MRI is a very useful tool for helping your doctors see images of the inside of your body, including tissue that can't be seen on a conventional x-ray.
Before your exam, it's very important to fill out the safety screening form carefully. MRI is safe and painless. But metal in the scanner can cause serious safety problems or reduce the quality of the images. Your health care team needs to know about any metal in your body, even a small shard of metal from an accident. Fillings, bridges, and other dental work typically do not pose a problem.
But other metal that has been put into your body might prevent you from having an MRI. That includes some pacemakers, clips for treating aneurysms, and other devices with metal in them.
A nurse may review your health history before your exam. You may be given medications or contrast dye or have blood drawn. Be sure to tell the nurse if you're pregnant, have an allergy to contrast dye, or have kidney or liver problems.
You may not wear clothing with snaps or zippers in the scanner. You will be asked to wear a gown. Do not wear any jewelry or bring anything metal into the scanner, including a hearing aid. An MRI machine uses a powerful magnet to make images of your body. Unlike a CT scan, it does not use x-rays or other radiation. You will be given earplugs. The scanner makes a loud noise when it's operating. A device called a coil may be put on or around the area to be scanned to help capture the images.
You will also be given a squeeze ball to hold. You can use this to signal the technologist any time you need something.
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