MRI does not use ionizing radiation
MRI uses a strong magnetic field, changing magnetic fields, radiofrequency energy, and a computer to create images. It does not use the ionizing radiation used by x-ray and CT imaging.
That difference is important, but it does not mean an MRI room has no safety risks. The magnetic environment changes which objects and devices can safely enter the room. Radiofrequency energy, scanner noise, body position, contrast, and a person's ability to remain still can also matter.
Safe MRI starts before the person enters the scanner room.
Why the safety form matters
The imaging team will ask about implants, medical devices, surgery, metal, pregnancy, patches, tattoos, and other details. Answer every question fully, even if an item has been in your body for years or did not cause a problem during another scan.
The team may need:
- the exact implant or device name;
- a device card;
- manufacturer and model information;
- the date and place of surgery;
- prior MRI safety records;
- an x-ray or other check for possible metal; or
- confirmation from a clinician or device maker.
Do not decide that an implant is safe based on a general web page. Some devices are MR Safe. Some are MR Conditional, which means they are safe only under stated conditions. An unknown device must be identified before the team can make a safe plan.
Metal objects can become dangerous
The scanner's static magnetic field can pull certain objects toward the magnet. Keys, phones, tools, oxygen tanks, and other magnetic items can become projectiles.
Remove all items the technologist identifies, including jewelry, hair accessories, watches, hearing aids, removable dental items, clothing with metal, and objects in pockets. The facility may provide approved clothing.
Tell the team about possible metal from work, military service, welding, grinding, injury, or a prior procedure. Metal near the eye needs special care.
Implants and devices need exact identification
Examples include:
- pacemakers and defibrillators;
- medication or insulin pumps;
- cochlear implants;
- aneurysm clips;
- neurostimulators;
- joint replacements;
- stents;
- surgical clips;
- tissue expanders;
- implanted ports;
- glucose monitors;
- external braces or wound devices; and
- retained wires or metal fragments.
The presence of a device does not always prevent MRI. The imaging team needs the device identity and its conditions for safe use.
Do not remove or adjust a medical device unless the responsible clinical team tells you to do so.
Radiofrequency energy can cause heating
The radiofrequency energy used during MRI can warm tissue. Conductive material, cables, skin-to-skin contact, some clothing, patches, tattoos, or devices can increase burn risk.
Follow the technologist's positioning instructions. Report unusual warmth, burning, stinging, pain, or discomfort at once. Use the call device provided during the exam.
Long exams can increase heating, which is one reason the protocol and scanner settings matter.
The scanner is loud
Changing magnetic fields create loud tapping, knocking, or thumping sounds. Hearing protection is part of safe scanning.
The imaging team should provide earplugs, headphones, or both. Tell the technologist if the protection does not fit or the sound feels painful. Do not remove hearing protection during an active scan unless the team directs you.
Claustrophobia and motion affect the plan
Some people feel confined or anxious in the scanner. Tell the imaging center before the appointment if that may affect you.
Options depend on the exam and facility. They may include a wider scanner opening, music, communication during the scan, planned breaks, a support person who also passes MRI safety screening, or medication prescribed by a clinician.
Medication for anxiety or sedation adds its own safety steps. Confirm fasting, transportation, monitoring, and discharge instructions in advance. Do not drive if the prescribing clinician says you should not.
Remaining still helps produce useful images. Tell the team before the scan if pain, tremor, breathing trouble, or another condition may make that difficult.
Contrast has a separate risk discussion
Some MRI exams use a gadolinium-based contrast agent. Others do not. The need depends on the clinical question and protocol.
Tell the team about kidney disease, a prior contrast reaction, pregnancy, and other requested health history. Ask why contrast is recommended, what extra information it may provide, and which risks apply to you.
Do not assume that a non-contrast screening package predicts whether a future diagnostic exam will need contrast.
Pregnancy requires a direct discussion
Tell the imaging team if you are pregnant or could be pregnant. The decision to perform MRI and to use contrast depends on the reason for the exam, timing, alternatives, and clinical judgment.
A general statement that MRI does not use ionizing radiation is not individual pregnancy advice.
Questions to ask before the appointment
- What safety form will I complete?
- Which implant or device records should I bring?
- Will this exam use contrast?
- What should I remove or wear?
- How long will I be in the scanner?
- What hearing protection is provided?
- How can I alert the technologist?
- What options exist if I feel claustrophobic?
- What transportation rules apply if medication is used?
- Who should I call if my device information is incomplete?
Call before the scan when you are unsure
Do not wait until you arrive to mention an implant, device, possible metal, pregnancy, severe anxiety, or a need for medication. The imaging team may need time to check records or adjust the plan.
MRI avoids ionizing radiation. Careful screening is still required for every person and every exam.