Magnetic Resonance Imaging (MRI) scans create detailed internal body images using an extremely strong magnetic field and radio waves. While the procedure is generally safe, the question of whether a person can get “stuck” is a valid safety concern. Getting stuck in an MRI machine can happen in two primary ways: through the magnetic attraction of external objects or from a patient’s physical confinement and psychological distress inside the machine’s tunnel. Both scenarios present distinct risks and require specialized safety protocols to manage.
The Primary Danger: Magnetic Projectiles
The most significant danger in an MRI suite relates directly to the machine’s immense magnetic force, which is always active. Modern MRI scanners typically operate with field strengths between 1.5 Tesla and 3 Tesla, thousands of times stronger than a common magnet. This powerful field exerts a strong pull on any ferromagnetic (iron-containing) object brought near it. This attraction can turn metallic items into high-speed projectiles, often called the “missile effect.” Objects like oxygen tanks, keys, and floor-cleaning buffers can be violently pulled into the machine’s bore, potentially trapping or severely injuring a patient or staff member. Rigorous screening procedures are implemented to remove all metallic items before patients and personnel enter the controlled environment. Safety areas are strictly demarcated, with the 5-Gauss boundary being important, as this is the level considered safe for the general public and where electronic devices like pacemakers are no longer at risk of interference.
Physical Confinement Inside the Bore
The second way a person can get “stuck” involves physical or psychological limitations within the machine’s confined space, known as the bore. Traditional MRI systems feature a relatively narrow tube, often around 60 centimeters (23.6 inches) in diameter. Patients with larger body types or significant swelling may find it physically difficult to enter or exit this tight space.
The feeling of being trapped often stems from claustrophobia. The combination of the narrow bore and the requirement to remain motionless for an extended period can trigger intense anxiety or panic attacks. A patient experiencing severe panic may freeze up or become unable to follow instructions, effectively trapping themselves until medical assistance can safely slide them out.
To mitigate this issue, many facilities offer “wide-bore” MRI machines, which increase the opening to 70 centimeters or more, providing a more spacious experience. Open MRI machines are another alternative, eliminating the tunnel entirely, though they may produce lower quality images. Sedation is also an option for patients whose anxiety prevents them from completing the scan.
Emergency Response: Utilizing the Quench
In the event of a severe magnetic incident, such as a metallic object pinning a patient against the machine, the ultimate emergency response is a procedure called the “quench.” This action is a rapid shutdown of the superconducting magnet’s field and is reserved only for life-threatening situations where the magnetic force prevents safe patient removal.
A quench works by intentionally stopping the superconductivity of the magnet coils. These coils are kept at extremely low temperatures—around -452 degrees Fahrenheit—by a bath of liquid cryogens, typically liquid helium. Pressing the emergency quench button causes the liquid helium to rapidly boil off and change into a gas, which vents out of the machine. This sudden loss of coolant causes the magnet to lose its superconducting state and its magnetic field to collapse.
The quench procedure carries its own dangers, requiring immediate room evacuation and specialized venting systems. The rapid boil-off produces a loud noise and a dense, cold cloud of helium gas that can displace oxygen, creating an asphyxiation hazard. Furthermore, the equipment damage caused by the quench is significant, rendering the machine unusable for an extended period and requiring costly helium replacement and system reactivation.