MRI interpretation
MRI safety

Key points

  • MRI safety issues apply to the scanning room
  • Ferrous metallic objects can become projectile and cause serious injury or death to patients or staff
  • All staff must abide by MRI department safety rules
  • Persons entering the scanning room must complete a safety questionnaire prior to being escorted in by trained MRI staff

Although MRI is considered a safe imaging technique, caution is required in the MRI scanning room. A typical MRI magnet has a local magnetic field which is 30,000 times the strength of the earth's magnetic field! Any magnetic object which comes close to the scanner could become projectile and cause serious injury or the death of a patient who is in the bore of the scanner.

The magnetic field

The magnetic field

  • This short video shows what happens to a tennis ball containing a paper clip when it approaches an MRI scanner
  • Any magnetic object which is too close to the scanner could become projectile and cause serious harm to the patient or staff

MRI safety precautions

When referring a patient for an MRI scan the clinician is usually required to complete some initial safety checks. Claustrophobic patients may need sedation, or other imaging tests can be considered. Up-to-date renal function results are required for patients having a scan with gadolinium.

Before entering the MRI room patients are again asked a set of safety questions by a radiographer. Patients with ferrous metallic foreign bodies or implanted electrical medical devices, such as pacemakers or cochlear implants, should not enter the MRI scanning room.

Any person with an implanted surgical device, such as a vascular aneurysm clip or prosthetic heart valve, can only enter the MRI scanner room once it has been established that the device is MRI compatible. If there is doubt, then the person must not enter.

MRI safety warnings

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MRI safety warnings

  • Make sure you abide by your departmental safety rules and all safety notices

The magnetic field itself is not harmful to patients. However, the machine is very noisy and patients are provided with ear protectors.

You must never enter an MRI room unless qualified to do so. You are not permitted to enter even if a patient has had a cardiac arrest. The patient must be removed from the room by MRI department staff before resuscitation can start.

MRI in pregnancy

Generally, MRI is not advised in pregnancy, especially during the first trimester. Discussion with the Radiology Department will be required. Contrast agents are avoided in patients who are pregnant or breast feeding.

Page author: Salisbury NHS Foundation Trust UK (Read bio)

Last reviewed: November 2020