MRI Scan Safety FAQ

MRI is one of the safest medical imaging techniques available — no radiation, no known long-term effects, over 40 years of clinical use. But "safe" doesn't mean "no rules." This MRI safety FAQ covers every common concern in detail: radiation, metal, implants, contrast, pregnancy, children, and what happens if things go wrong.

Radiation and General Safety

Does an MRI scan expose me to radiation?

No. MRI uses a strong magnetic field and radiofrequency (RF) pulses — not ionising radiation. There is zero radiation dose from an MRI scan. This is fundamentally different from CT scans (which use X-rays) and X-rays.

Can MRI scans cause cancer?

No. Because MRI uses no ionising radiation, it does not carry the DNA-damage risk associated with X-ray-based imaging. Over four decades of research and billions of scans worldwide have found no link between MRI and cancer development.

Is it safe to have multiple MRI scans?

Yes. There is no known cumulative risk from repeated MRI scanning. Unlike CT (where radiation doses add up over a lifetime), you can have as many MRIs as clinically needed. This makes MRI particularly suitable for long-term monitoring of conditions like multiple sclerosis, tumours, and inflammatory diseases.

Does the magnetic field damage cells or DNA?

No. The static magnetic field, gradient magnetic fields, and radiofrequency pulses used in clinical MRI (1.5T and 3T) have been extensively studied. No reproducible evidence of cell damage, DNA mutation, or adverse biological effects has been found at clinical field strengths.

Is the MRI scanner always on?

Yes. The main superconducting magnet runs continuously — it is never switched off during normal operation. (Shutting it down, called a "quench," is an emergency procedure that boils off the liquid helium coolant.) This is why strict metal-screening protocols apply whenever anyone enters or approaches the scanning room, even when no scan is scheduled.

Can MRI affect my brain or nervous system?

No lasting effects. Some people report mild, temporary dizziness or a metallic taste when moving quickly through the magnetic field (particularly at 3T), but these sensations resolve immediately and are harmless. There is no evidence of neurological harm from clinical MRI.

Metal and Implants

Can I have an MRI with metal implants?

It depends on the type. Most modern orthopaedic hardware — titanium joint replacements, plates, screws, rods — is non-ferromagnetic and MRI-compatible. The safety team verifies every implant before scanning, using your implant card and manufacturer documentation. See our full metal implants guide.

Three safety categories exist:

• MR Safe — Contains no metal whatsoever. Safe in any MRI environment.
• MR Conditional — Safe under specific conditions (e.g., only at 1.5T, only with certain scanner settings). Most modern implants fall here.
• MR Unsafe — Must not enter the MRI room. Includes some older pacemakers and certain intracranial aneurysm clips.

What happens if ferromagnetic metal enters the MRI room?

The scanner's magnetic field exerts a powerful pulling force on ferromagnetic objects. A steel oxygen cylinder, wheelchair, or even a hairpin can become a dangerous projectile — accelerating towards the bore at speed. This "missile effect" is the single greatest physical safety risk in MRI and the reason every person entering the room is screened for metal.

Can I have an MRI with dental fillings?

Yes. Standard amalgam fillings, gold crowns, porcelain bridges, dental implants (titanium posts), and root canal posts are all safe. They may cause minor localised image distortion on jaw or face scans, but they pose no safety risk and do not need to be removed.

Can I have an MRI with a tattoo?

In the vast majority of cases, yes. Some older tattoo inks (particularly red and black inks from before 2000) contained iron oxide particles that can absorb RF energy and cause mild, localised warming or tingling during the scan. Modern tattoo inks are generally MRI-compatible. Inform the radiographer about all tattoos — they will monitor you. It is extremely rare for a tattoo to prevent an MRI scan.

What about body piercings?

All piercings must be removed before entering the scanning room. If a piercing genuinely cannot be removed (e.g., a surgical-grade titanium piece), inform the radiographer, who will assess the material and decide whether scanning is safe.

Can I have an MRI with an IUD (coil)?

Yes. Both copper IUDs (e.g., Paragard) and hormonal IUDs (e.g., Mirena, Kyleena) are MR Conditional at both 1.5T and 3T. The IUD does not need to be removed. There is no evidence that MRI displaces a correctly positioned IUD. Inform the radiographer that you have one.

Can I have an MRI with a pacemaker or defibrillator?

If your device is labelled MR Conditional (most devices implanted since roughly 2010-2015), you can be scanned under specific conditions — typically at 1.5T only, with cardiology involvement to reprogram the device before and after the scan. Older non-MR-conditional devices are MR Unsafe. Always bring your device card and inform the scanning centre at the time of booking. See our implants guide.

Can I have an MRI with cochlear implants?

Newer cochlear implants (from roughly 2012 onwards) are generally MR Conditional at 1.5T with the internal magnet in place or removed. Older models may be MR Unsafe. Your implant centre will have documentation specifying the exact conditions. This requires specialist planning — inform the scanning centre well in advance.

Contrast Agent (Gadolinium) Safety

What are the risks of gadolinium contrast?

Gadolinium-based contrast agents have an excellent safety record across hundreds of millions of doses worldwide. Mild side effects (brief headache, nausea, metallic taste, injection site coolness) occur in roughly 1-2% of patients and resolve without treatment. Serious allergic-type reactions (anaphylaxis) are extremely rare — roughly 1 in 100,000 administrations. All MRI centres have resuscitation equipment on hand.

Is gadolinium safe for my kidneys?

For people with normal kidney function, yes — gadolinium is filtered and excreted by the kidneys within approximately 24 hours. Patients with severely impaired kidney function (eGFR below 30) must not receive gadolinium due to the risk of nephrogenic systemic fibrosis (NSF), a rare but serious condition affecting the skin and connective tissue. If you are over 60, have diabetes, high blood pressure, or known kidney disease, a blood test to check your eGFR may be required before contrast is given.

Does gadolinium stay in my body permanently?

Most gadolinium is excreted within 24 hours. However, research since 2014 has shown that trace amounts of gadolinium can be retained in certain tissues — particularly the brain (dentate nucleus and globus pallidus) and bone. To date, no adverse health effects from this retention have been identified in patients with normal kidney function. Current guidelines (ESUR, ACR, MHRA) recommend using contrast only when it provides clear diagnostic benefit — not indiscriminately.

Can I have gadolinium if I am allergic to iodine contrast?

Yes. Gadolinium-based MRI contrast and iodine-based CT contrast are chemically unrelated substances with completely different mechanisms. An allergy to iodinated contrast does not predict a reaction to gadolinium. However, inform the radiographer of any previous contrast reactions — people who have reacted to any contrast agent may have a slightly higher risk of reacting to others.

Pregnancy and Breastfeeding

Is MRI safe during pregnancy?

MRI is generally considered safe during pregnancy because it uses no ionising radiation. The main evidence comes from large retrospective studies (including a 2016 JAMA study of over 1.4 million pregnancies) showing no increased risk of harm. As a precaution, MRI is typically avoided in the first trimester unless clinically urgent. When MRI is needed during pregnancy (e.g., appendicitis, neurological symptoms, placental assessment), it is used and considered safer than CT.

Can I have gadolinium contrast while pregnant?

Gadolinium is generally avoided during pregnancy. Animal studies have shown that gadolinium crosses the placenta and enters fetal circulation. A 2016 Canadian study (JAMA) found a slightly increased risk of certain conditions in babies exposed to gadolinium in utero, though absolute risks were very small. Non-contrast MRI is always preferred during pregnancy. Gadolinium is used only when the clinical benefit clearly outweighs the potential risk.

Can I have an MRI while breastfeeding?

Yes. The MRI scan itself has no effect on breast milk. If gadolinium contrast is given, current guidelines from ESUR, ACR, and the MHRA all state that breastfeeding can continue without interruption — less than 0.04% of the gadolinium dose passes into breast milk, and less than 1% of that is absorbed by the infant's gut.

Children

Is MRI safe for babies and young children?

Yes. MRI is considered very safe for children of all ages, including newborns. The absence of radiation makes it particularly valuable in paediatrics — conditions can be monitored with repeated scans without any radiation exposure. See our full children and MRI guide.

Is sedation or anaesthesia safe for children during MRI?

Paediatric sedation and general anaesthesia for MRI are routine procedures performed by specialist teams. However, they carry their own small risks (breathing complications, allergic reactions). The 2016 FDA drug safety communication raised concerns about repeated or prolonged general anaesthesia in children under 3, but a single short anaesthetic for MRI is considered very low risk. The child's breathing, heart rate, and oxygen levels are monitored continuously throughout.

Can children have gadolinium contrast?

Yes, when clinically indicated. Gadolinium is safe for children with normal kidney function. The dose is weight-adjusted. The same safety profile applies as for adults.

During the Scan

Can the noise from the scanner damage my hearing?

Not with proper ear protection. MRI scanner noise can reach 100-110 dB (comparable to a chainsaw or rock concert). Without protection, this could cause hearing damage. Foam earplugs and/or headphones are mandatory for every scan, reducing noise to safe levels. If you feel that your ear protection has come loose during the scan, squeeze the alarm button immediately.

Can I overheat inside the scanner?

The RF pulses used during scanning deposit energy in your body, measured as SAR (Specific Absorption Rate). The scanner automatically monitors and limits SAR to prevent harmful tissue heating. You may feel mild warmth in the area being scanned — this is normal. If you feel uncomfortably hot or notice any burning sensation, alert the radiographer immediately via the alarm button.

Can I suffocate inside the scanner?

No. The scanner bore is open at both ends with continuous airflow. Many scanners also have built-in fans. You are never sealed inside — the table can slide out at any time, and the alarm button brings the radiographer immediately.

What if there is a power cut during my scan?

The scanner table can be manually extracted from the bore even without power. Emergency lighting activates automatically. The superconducting magnet remains active (it is cooled by liquid helium, not powered by mains electricity), but scanning sequences stop. You will be removed safely.

What if I have a panic attack inside the scanner?

Squeeze the alarm button. The radiographer will stop the scan, slide the table out, and help you. This happens regularly and no one will be surprised or annoyed. Options include taking a break, adjusting your position, trying relaxation techniques, or rescheduling with sedation. See our claustrophobia guide.

Can the MRI scanner malfunction and hurt me?

MRI scanners have multiple built-in safety systems and undergo regular maintenance and safety testing. Serious malfunctions are exceptionally rare. The scanning room has emergency stop buttons and quench procedures. The greatest actual risk in MRI comes not from the machine itself but from ferromagnetic objects entering the room — which is why metal screening is so thorough.