In July 2025, a 61-year-old man from Long Island walked into an MRI suite to help his wife off the table after her scan. He was wearing a nine-kilogram (roughly 20-pound) metal chain around his neck — a training accessory. The machine's magnetic field pulled him violently toward the scanner. He was hospitalized in critical condition and later died from his injuries.

Stories like this are shocking. They make international headlines precisely because they are rare. But they raise a question that roughly 40 million Americans face every year when their doctor orders a scan: is MRI actually safe?

The short answer is yes — overwhelmingly so. MRI uses no ionizing radiation, no injections (in most cases), and no incisions. A private imaging company in the United Kingdom performed 1.3 million MRI scans over three years and recorded only 10 burns and 32 projectile incidents, none of which caused serious injury. Those are extraordinarily small numbers relative to the volume.

But MRI is built around an enormously powerful magnet — and that magnet is always on. The safety incidents that do occur are almost always preventable. They happen when someone brings the wrong object into the room, forgets to mention an implant, or skips a screening step.

This article explains how MRI works, what the real risks are, and — most importantly — exactly what you can do to make your scan as safe as possible. If you have an MRI scheduled, or if you simply want to understand the technology before you ever need one, this is the guide to read.

How MRI Works — and Why the Magnet Never Turns Off

Magnetic resonance imaging produces detailed pictures of your organs, soft tissues, bones, and blood vessels without using X-rays. Instead, it relies on three components that work together: a powerful static magnet, radiofrequency (RF) coils, and gradient coils.

The static magnet is the core of the system. Clinical MRI scanners typically operate at 1.5 or 3 Tesla — between 30,000 and 60,000 times stronger than Earth's magnetic field. This magnet creates its field using superconducting wire cooled by liquid helium to approximately minus 269 degrees Celsius. At that temperature, the wire achieves superconductivity, meaning electrical current flows through it without any resistance — forever, unless the helium is deliberately removed.

This is why the magnet is always on. It is not powered up when you arrive and powered down when you leave. Shutting it down — a process called a "quench" — means boiling off the liquid helium. That is an emergency procedure, not a routine switch. It is expensive, time-consuming, and potentially dangerous if helium vents improperly into the room.

The RF coils send radio wave pulses into your body that temporarily knock hydrogen atoms out of alignment with the magnetic field. When those atoms snap back, they emit signals. Different tissues emit signals at different rates. The gradient coils create smaller, precisely controlled variations in the magnetic field that allow the computer to map those signals to exact locations in three-dimensional space.

The result is an image with extraordinary soft-tissue contrast — far better than CT or X-ray for many conditions. And the entire process uses no ionizing radiation, which is one of MRI's greatest safety advantages.

The Projectile Effect: When Metal Becomes a Missile

The most dramatic MRI accidents involve the projectile effect — also called the "missile effect." Any object containing ferromagnetic material (iron, nickel, cobalt, and certain alloys) can be accelerated toward the scanner bore at startling speed.

The force is not subtle. An MRI magnet can pull a ferromagnetic object with a force many times the object's own weight, and that force increases exponentially as the object gets closer to the bore. A wrench, an oxygen tank, or a metal chain that feels manageable at the doorway can become impossible to hold back by the time it is a few feet from the scanner.

Real-world incidents illustrate the range of scenarios:

  • In South Korea, a man was fatally pinned between an oxygen tank and the MRI machine when the tank was brought into the scanner room.
  • In New Zealand, a patient carrying a folding knife had it propelled into his eye, fracturing his orbital bone.
  • In Brazil, a patient undergoing an MRI was shot by a firearm that had been brought into the room and was pulled toward the magnet.
  • In the United States, FDA adverse event reports document cases involving oxygen cylinders, wheelchairs, IV poles, and floor buffers — all pulled into the scanner.

Smaller objects are more common and usually less dangerous. The 1.3-million-scan UK dataset mentioned earlier found that most projectile events involved pocket items: coins, keys, phones, and on one occasion a wrench. None of those incidents caused serious injury, but they damaged scanners and disrupted schedules.

Burns: The Risk You Do Not See Coming

The second category of MRI injury is thermal — burns caused by the scanner's RF and gradient coils. These coils change the electromagnetic field rapidly, and that changing field can induce electrical currents in conductive materials touching or inside the patient's body. Those currents generate heat.

Most MRI burns are mild — first-degree, comparable to a sunburn. But second-degree burns do occur. The mechanism usually involves one of the following:

  • Skin-to-skin contact: If your thighs touch, or your arms rest against your torso, the RF field can create a current loop through the contact point. Technologists place padding between limbs specifically to prevent this.
  • Conductive materials in clothing: A patient wearing a microfiber garment with silver threading received second-degree burns along the seam, likely from the combination of conductive material and trapped moisture.
  • Tattoo ink: Some tattoo inks contain iron oxide or other metallic pigments. A professional American football player reported a mild burn at the site of his tattoos during an MRI scan. The risk is generally low and most people with tattoos complete MRI without incident, but it is a real phenomenon.
  • Monitoring equipment: ECG leads, pulse oximeter cables, and other wires placed on the body during the scan can act as antennas if improperly positioned, concentrating RF energy at the point where the wire contacts the skin.

The good news: burns are rare when standard protocols are followed. Facilities that rigorously pad contact points, screen for conductive materials, and properly route monitoring cables report burn rates close to zero.

Implants, Devices, and Embedded Metal

One of the most important — and most nuanced — areas of MRI safety involves implanted devices and metal inside the body. This is where the screening questionnaire you fill out before your scan becomes critically important.

The interactions between MRI and implanted materials fall into three categories:

  1. Movement or torque: Ferromagnetic implants can shift, rotate, or migrate inside the body under the influence of the static magnetic field.
  2. Heating: Any conductive implant — ferromagnetic or not — can absorb RF energy and heat up, potentially damaging surrounding tissue.
  3. Malfunction: Active electronic devices (pacemakers, neurostimulators, insulin pumps) can have their programming altered, their batteries depleted, or their function disrupted by all three MRI components.

The labeling system used by manufacturers and MRI facilities classifies devices into three categories, as outlined on the comprehensive MRI safety reference database:

  • MR Safe: Contains no metallic, magnetic, or conductive components. Poses no known hazards in any MRI environment. Example: certain plastic IUD types.
  • MR Conditional: Safe under specific conditions — for instance, only at 1.5 Tesla, only with certain scan sequences, or only after a certain time has passed since implantation. Example: many modern joint replacements.
  • MR Unsafe: Poses a definite hazard in MRI. The device must not enter the scanner room. Example: certain older pacemaker models.

This classification matters enormously. An UpToDate clinical review on patient evaluation before MRI emphasizes that each implant must be individually assessed — the generic type of device is not sufficient. A "hip replacement" might be MR Safe, MR Conditional, or MR Unsafe depending on the exact manufacturer, model, and year of implantation.

Cardiac Devices: The Rules Have Changed

For decades, having a pacemaker or implantable cardioverter-defibrillator (ICD) was considered an absolute contraindication to MRI. The logic was straightforward: these devices contain ferromagnetic components, conductive leads that extend into the heart, and sensitive electronics — a combination of every risk factor.

That blanket prohibition has evolved significantly. Since 2011, manufacturers have produced "MR Conditional" cardiac devices specifically designed and tested for use in MRI under controlled conditions. These devices have modified lead designs, reduced ferromagnetic content, and software modes that can be activated before a scan.

A comprehensive review by the American College of Cardiology outlines the current state of the field: patients with MR Conditional devices can safely undergo MRI when the device is reprogrammed to "MRI mode" before the scan, specific absorption rate (SAR) limits are observed, and the scan is performed at the designated field strength (typically 1.5T).

Even patients with older, "legacy" (non-MR Conditional) cardiac devices may now undergo MRI in certain circumstances, under strict protocols at experienced centers. This is a significant shift from the blanket ban of the past.

However — and this is critical — even after a cardiac device has been removed, residual leads may remain in the body. These abandoned leads can still interact with the MRI field. If you have ever had any cardiac device, that information must be disclosed even if the device itself has been removed.

Foreign Bodies You May Not Know About

Some of the trickiest MRI safety scenarios involve metal that the patient does not realize is present. This is more common than you might think.

Occupational exposure is a leading cause. People who have worked in metalworking, grinding, welding, or military service may have small metallic fragments embedded in their soft tissues — particularly around the eyes. These fragments can be too small to feel and may not cause any symptoms, but under MRI they can move and cause serious damage, including retinal hemorrhage. For this reason, patients with a history of metallic foreign body exposure are typically screened with orbital X-rays before MRI.

Other embedded metals that patients frequently forget about or underestimate include:

  • Shrapnel, bullets, or shell fragments from military service or accidents — even decades-old fragments that cause no symptoms can be hazardous in MRI.
  • Small magnets swallowed by children, which can remain in the gastrointestinal tract. On MRI, these can perforate the intestinal wall, sometimes requiring emergency surgery.
  • Retained surgical materials, including clips, wires, or staples from prior procedures that the patient may not know about.

One particularly alarming FDA adverse event report described a case where a patient with a history of metalwork developed eye symptoms after an MRI — small metallic debris had been in the orbit for years without causing any problems until the MRI field moved it.

The lesson is clear: your MRI screening form asks about metal in your body for a reason. Even if you think a piece of embedded metal is harmless, or if you are not entirely sure it exists, disclose it.

Items That Seem Harmless — but Are Not

Beyond the obvious (do not bring a gun into an MRI room), there is a long list of everyday items and medical products that patients frequently forget about or assume are too small to matter.

Tattoos and permanent makeup: As noted above, some inks contain metallic pigments — iron oxide is the most common. Most tattoos are fine, but large or darkly pigmented tattoos can cause localized heating. Cosmetic permanent makeup (eyebrow tattoos, eyeliner, lip liner) also uses metallic pigments. The risk is low, but the radiologist needs to know so they can take precautions — such as placing a cold compress on the tattooed area.

Transdermal medication patches: Some patches — particularly those containing metallic foil backing (older fentanyl, nicotine, and nitroglycerin patches) — can heat up and cause burns during MRI. Patients are typically asked to remove patches before scanning.

Dental work: Modern dental implants, crowns, and bridges are generally made from non-ferromagnetic materials (titanium, ceramic, zirconia) and are MR Conditional. However, some older dental work, orthodontic retainers, and magnetic dental overdentures may contain ferromagnetic components. These rarely pose a safety risk — the forces are typically not strong enough to dislodge well-anchored dental hardware — but they can cause significant image distortion in head and neck MRI.

Intrauterine devices (IUDs): Most modern IUDs (copper and hormonal) are MR Conditional and safe at commonly used field strengths. However, the radiologist should be informed.

Penile prostheses, hair extensions with metal clips, metallic eyelash extensions, and body jewelry: All can interact with the MRI field. They may be safe, but they must be disclosed so the team can make an informed decision.

How Facilities Keep You Safe: Screening Zones and Protocols

Modern MRI facilities use a four-zone safety system defined by the American College of Radiology (ACR) to control access to the magnet:

  • Zone I: General public area — the waiting room and reception.
  • Zone II: Interface between public and controlled areas — where screening begins.
  • Zone III: The restricted area near the magnet room — only screened individuals allowed.
  • Zone IV: The scanner room itself — the highest-risk area, where the magnetic field is at full strength.

The transition from Zone III to Zone IV is where most accidents can be prevented. This is why you are asked to change into a gown, pass through a metal detector in some facilities, and be screened multiple times.

The screening process involves two key steps:

  1. Written questionnaire: You fill out a detailed form asking about every implant, device, surgery, foreign body exposure, tattoo, and medication patch. This form exists because MRI technologists cannot detect internal metal by observation alone.
  2. Verbal confirmation: A trained MRI technologist or nurse reviews your form with you, asks follow-up questions, and may ask you to remove items you did not think of — jewelry, hairpins, underwire bras, hearing aids, glasses, watches.

Some facilities have added handheld or walk-through metal detectors as a third layer of screening. Research suggests this could prevent a significant proportion of projectile incidents, since patients occasionally answer the screening questionnaire inaccurately — whether through oversight, language barriers, or deliberate concealment.

MRI-related injuries are classified as "never events" — events that, in the view of regulatory bodies, should never occur in a properly run facility. This classification reflects the consensus that virtually every MRI accident is preventable with proper screening.

What to Expect on Scan Day: A Step-by-Step Walkthrough

Knowing what to expect can ease anxiety and help you comply with safety protocols more effectively. Here is what a typical MRI visit looks like from arrival to departure.

Before you arrive: You may receive preparation instructions — whether to fast, stop certain medications, or avoid caffeine. Follow them carefully. If you are claustrophobic, anxious, or have difficulty lying still, tell your referring doctor in advance. They may prescribe a mild sedative or arrange for an open MRI scanner.

Arrival and screening: You will check in and complete the MRI safety screening questionnaire. Answer every question honestly and completely. If you are unsure about an implant or prior surgery, say so — the staff would much rather investigate than have you go into the scanner with unknown metal.

Changing: You will change into a hospital gown and remove all personal items — jewelry, watch, phone, wallet, keys, coins, hairpins, hearing aids, glasses, dentures, belts with metal buckles, underwire bras, and any clothing with metallic fasteners or threads. Some facilities provide lockers.

Contrast (if applicable): Some MRI exams require gadolinium-based contrast, which is injected intravenously. The technologist will place a small IV line in your arm. Gadolinium-based contrast agents have a strong safety record, though they carry specific considerations for patients with severe kidney disease.

The scan: You will lie on a motorized table that slides into the scanner bore — a tube approximately 60 centimeters (2 feet) in diameter. The scan lasts anywhere from 15 minutes to over an hour depending on the body part and sequences ordered. You must lie still; motion blurs the images.

Noise: MRI machines are loud — the rapid switching of gradient coils produces knocking, buzzing, and thumping sounds that can reach 100+ decibels. You will be given earplugs, headphones, or both. This is normal and not a sign that anything is wrong.

Communication: You will have a squeeze ball or call button that connects you to the technologist at all times. If you feel any unusual warmth, pain, or discomfort, squeeze it immediately. The scan can be paused or stopped at any point.

After the scan: You can resume all normal activities immediately (unless you received sedation). If contrast was used, you may be asked to drink extra water. Results are typically sent to your referring physician within 1-3 business days.

Claustrophobia and Anxiety: Practical Strategies

Claustrophobia during MRI is common — estimates suggest it affects 5-15% of patients, and it is one of the leading reasons patients fail to complete their scan. This is not a trivial concern, and it does not mean something is wrong with you.

The scanner bore is narrow and enclosed, the exam requires you to lie still, and the loud noises can heighten a sense of confinement. Here are evidence-based strategies:

  • Ask about scanner type: Wide-bore scanners (70 cm diameter vs. the standard 60 cm) and open MRI scanners are available at many facilities. Open scanners have weaker magnets and produce lower-resolution images for some applications, but for many exams they are perfectly adequate.
  • Bring your own music or audiobook: Many facilities allow you to listen to audio through MRI-compatible headphones. Having something to focus on can significantly reduce anxiety.
  • Use the call button: Knowing you can stop the scan at any time is psychologically powerful. Hold the squeeze ball and test it before the scan begins.
  • Close your eyes before entering the bore: Some patients find that never seeing the enclosed space makes the experience much easier. A sleep mask can help.
  • Practice breathing techniques: Slow, deep breathing activates the parasympathetic nervous system. Inhale for 4 counts, hold for 4, exhale for 6.
  • Request a sedative: If your claustrophobia is severe, your doctor can prescribe a mild benzodiazepine (such as lorazepam) to take before the appointment. You will need someone to drive you home.
  • Feet-first positioning: For scans of the lower body (knees, ankles, pelvis), you may enter the scanner feet-first, keeping your head outside the bore entirely. Ask the technologist if this is an option for your exam.

MRI vs. Other Imaging: Radiation and Comparative Safety

One of MRI's strongest safety advantages is the absence of ionizing radiation. A single CT scan of the chest delivers approximately 7 millisieverts (mSv) of radiation — equivalent to about two years of natural background exposure. An MRI delivers zero.

This matters most for:

  • Repeated imaging: Patients who need regular follow-up scans (monitoring tumors, tracking disease progression) accumulate radiation dose with CT and X-ray but not with MRI.
  • Pediatric imaging: Children are more sensitive to radiation because their cells divide faster. MRI is preferred for many pediatric applications precisely for this reason.
  • Pregnancy: MRI is generally considered safe during pregnancy (without gadolinium contrast in the first trimester), whereas CT and X-ray expose the fetus to ionizing radiation.
  • Screening: For applications like breast cancer screening in high-risk women, MRI avoids the radiation dose associated with mammography.

Research published in the British Journal of Radiology Open provides a comprehensive overview of MRI's safety profile relative to other imaging modalities. The key finding: when MRI can provide the diagnostic information needed, it is generally the safest imaging option available from a radiation standpoint.

That said, MRI is not always the best choice. CT is faster, better for bone detail, and more widely available in emergency settings. X-ray is ideal for simple fracture assessment. Ultrasound is portable, inexpensive, and excellent for certain applications. Your doctor chooses the modality based on what question needs answering — not simply which one is "safest."

Special Populations: Pregnancy, Children, and Elderly Patients

MRI has specific considerations for certain patient groups.

Pregnancy: MRI is considered safe at any gestational age based on current evidence, and it is frequently used to evaluate fetal anomalies, placental complications, and maternal conditions where ultrasound is insufficient. However, gadolinium contrast should be avoided during the first trimester unless the clinical benefit clearly outweighs the potential risk, as gadolinium crosses the placenta and its effects on the developing fetus are not fully characterized.

Children: Pediatric MRI presents unique challenges — primarily the need for the child to remain still for extended periods. Young children often require general anesthesia or deep sedation, which carries its own risk profile. Newer rapid-sequence MRI protocols and motion-correction software are reducing sedation needs. When possible, coaching, distraction techniques, and mock scanner sessions can help older children complete scans without sedation.

Elderly patients: The main concerns for older adults are comfort (lying on a hard table for 30-60 minutes can aggravate back pain or joint stiffness), hearing protection (age-related hearing loss does not eliminate the need for ear protection — MRI noise can still cause damage), and the presence of multiple implants or devices that must each be individually assessed for MRI compatibility.

Patients with renal impairment: Gadolinium-based contrast agents are processed by the kidneys. In patients with severely reduced kidney function, certain gadolinium agents have been associated with nephrogenic systemic fibrosis (NSF), a rare but serious condition affecting the skin and internal organs. Newer "group II" gadolinium agents have largely eliminated this risk, but kidney function is still checked before contrast administration.

The Statistics: How Rare Are MRI Injuries?

Putting numbers to the risk helps place MRI safety in perspective.

The UK dataset remains one of the most comprehensive: across 1.3 million scans, there were 10 burn incidents and 32 projectile events. That is a combined adverse event rate of approximately 0.003% — or about 3 incidents per 100,000 scans. No serious injuries resulted from any of those events.

FDA adverse event reporting data shows that serious MRI injuries, while not zero, are exceedingly rare relative to the tens of millions of scans performed annually. The Agency for Healthcare Research and Quality classifies MRI-related injuries as "never events" — meaning they are considered entirely preventable with proper protocols.

A systematic review of MRI safety incidents found that the vast majority involved failures in screening protocols rather than inherent dangers of the technology itself. The most common root causes were: patients not disclosing metal or implants, staff bringing ferromagnetic equipment into the scanner room, and incomplete pre-scan screening.

The comparative context matters too. MRI carries no radiation risk. The risk of a serious allergic reaction to gadolinium contrast is estimated at approximately 1 in 10,000 to 1 in 100,000 administrations — far lower than the reaction rates for iodinated CT contrast.

In short: MRI is one of the safest diagnostic tools in modern medicine. The small residual risk is almost entirely dependent on human behavior — and that means you, as the patient, have real power to reduce it further.

Your Pre-MRI Checklist: What to Tell the Technologist

The single most important thing you can do for your MRI safety is be thorough and honest on your screening questionnaire. Here is a comprehensive checklist of what to disclose — even items that seem irrelevant.

Implanted devices and hardware:

  • Pacemaker, ICD, or cardiac monitor (current or previously removed)
  • Cochlear implants or hearing devices
  • Neurostimulators (deep brain, spinal cord, vagus nerve)
  • Insulin pump or other drug infusion device
  • Any metallic heart valve
  • Aneurysm clips (especially cerebral)
  • Joint replacements (hip, knee, shoulder)
  • Spinal hardware (rods, screws, plates)
  • Vascular stents or filters
  • Surgical clips, staples, or pins from any prior surgery
  • Dental implants, braces, or retainers
  • Intrauterine device (IUD)
  • Penile prosthesis

Embedded metal:

  • Shrapnel, bullets, or shell fragments
  • History of metalworking, grinding, or welding (even years ago)
  • Prior injury involving metal fragments
  • Swallowed metal objects (especially relevant for children)

External items to remove or disclose:

  • All jewelry, piercings (including genital piercings), and body modifications
  • Tattoos (location, size, and approximate age)
  • Permanent makeup or cosmetic tattooing
  • Transdermal medication patches
  • Hair extensions with metal clips
  • Wigs with metal components
  • Metallic eyelash extensions
  • Clothing with metallic threads (check athletic wear)

Medical history:

  • Kidney disease or reduced kidney function (relevant if contrast is planned)
  • Pregnancy or possible pregnancy
  • Severe claustrophobia
  • Inability to lie flat or still for extended periods
  • Previous allergic reaction to MRI contrast (gadolinium)

The goal is not to scare you. It is to ensure the MRI team has every piece of information they need to keep you safe. When in doubt, mention it.

Tracking Your Medical History With WatchMyHealth

One of the challenges patients face when filling out MRI screening forms is remembering every relevant detail. What was the exact model of the knee implant you got eight years ago? Did the surgeon use titanium or stainless steel clips during your gallbladder removal? Was the IUD you had placed last year MR Safe or MR Conditional?

These are not trivial questions — and the answers matter. The physician visit tracker in WatchMyHealth gives you a single, organized place to record your medical procedures, surgeries, and device implantations as they happen. When you are sitting in the MRI screening room trying to recall details from years ago, having a clear log of your medical history makes the process faster, more accurate, and safer.

Beyond MRI preparation, a comprehensive medical history log helps with:

  • Specialist consultations: New doctors always ask for your surgical and implant history.
  • Emergency care: If you are unable to communicate, a detailed health record on your phone can provide critical information.
  • Insurance and pre-authorization: Having dates and details readily available speeds up administrative processes.
  • Longitudinal tracking: Seeing your full medical timeline in one place helps you and your doctors identify patterns and make better decisions.

The best time to log a procedure or device is right after it happens — when the details are fresh and the documentation is at hand. The second-best time is now.

Key Takeaways

MRI is overwhelmingly safe. It uses no radiation, produces no lasting biological effects in the vast majority of patients, and carries an adverse event rate measured in single digits per hundred thousand scans. The technology itself is not the risk — incomplete screening is.

Here is what matters:

  1. The magnet is always on. Never bring any metal object into an MRI room — not even to "quickly" help someone.
  2. Be honest and thorough on your screening form. Disclose every implant, every surgery, every tattoo, every piece of embedded metal. Omitting something because it seems insignificant is how preventable accidents happen.
  3. When in doubt, speak up. The MRI team would always rather pause and investigate than proceed with incomplete information.
  4. Cardiac devices are no longer an automatic disqualification. If you have a pacemaker or ICD, talk to your cardiologist — you may still be able to have an MRI safely.
  5. Occupational metal exposure requires extra screening. If you have ever worked with metal, request orbital X-rays before your first MRI.
  6. Claustrophobia is manageable. Wide-bore scanners, open MRI, sedation, and simple coping techniques can get most patients through the scan.
  7. Keep a record of your medical devices and surgeries. You will need this information for every MRI you ever have — and for many other medical situations.

The goal of MRI safety is not to make you afraid of the scan. It is to ensure that a powerful, invaluable diagnostic tool is used with the respect it deserves. Do your part — fill out the form completely, ask questions, and walk into that scanner room with nothing the magnet can grab.