MRI Magnetic Resonance Imaging

MRI Safety

Definitions:

MRI – magnetic resonance imaging

Adverse Event – any unexpected or dangerous reaction to treatment/drug/procedure

Serious Adverse Events - any event which causes death, permanent damage, or requires hospitalization

Ferromagnetic Object – object with magnetic properties

There are Potential Risks in the MRI Environment for:

Patients

Accompanying family members

Accompanying health care professionals

Security

Housekeeping personnel

Firefighters/Police/Prison Guards

What Makes the MRI Environment so Hazardous?

· Large invisible magnetic fields that extend in 3 dimensions

· It is impossible to tell by looking at an MRI system whether it is “ON” or not

· Many objects that don’t appear to contain ferromagnetic/hazardous material

o For example, sandbags – some contain ferrous materials even though one would not think so.

· Labeling on devices or in documentation can be confusing

o “MR safe” and “MR compatible” are specific to a particular MR environment. The terms are not intended to be used without further specifying the particular MR environment where the devices have been tested and found safe and compatible for

o “MR safe” and “MR compatible” may not be with more powerful MRIs

· Combination of complacency, work-arounds for speed, and diffuse responsibility

· Equipment and consumables that are “safe” 99% of the time become “unsafe” near MRI

· People and equipment who are “new” to MRI suite (more interventions and surgeries)

Ferromagnetic Objects Include:

Buffing machines

Chest tube stands

Clipboards (patient charts)

Gurneys

Hairpins

Hearing aids

Identification badges

Insulin pumps

Keys

Medical gas cylinders

Mops

Nail clippers and nail files

Oxygen cylinders

Pulse oximeters

Steel shoes

Stethoscopes

Scissors

Staples

Vacuum cleaners

Watches

Wheelchairs

Types of MRI Hazards

· Projectile effect (ferromagnetic material pulled toward the magnet bore) - Oxygen bottles, scissors, IV poles, patient lifts, traction weights, pens, stethoscopes, and hair barrettes

Hairpins near a MR magnet can reach speeds of 40mph

· Twisting (magnetic objects aligning parallel with the field – torque)

· Magnetic cochlear implants & cerebral aneurysm clips twist within the body causing damage

· Magnetic components rip loose from their foundation on equipment causing device failure or patient injury

· Burns from objects that may heat during the MRI process

o Looped ECG leads, pulse oximeter cables, & MR accessories (e.g., RF coil leads) in contact with

o a patient under sedation can cause full thickness burns

o While rare in occurrence, tattoos or tattooed eye-liner containing iron oxide have heated to cause minor burns

o Skin burns at the sites where the pulse oximeter sensor touches and ECG electrode sites

o Skin burns from contacting the bore of the magnet

o Inadvertent overly high settings for extremity exams have caused ignition of special cuffs/sleeves

· Device malfunction (electronics or mechanics affected)

o Devices with analog gauges, electric motors, transformers, relays, & switches can be affected by the static magnetic field

o Devices that use magnetization to attach to a patient (e.g., some dental devices) and some implants that are electrically, magnetically, or mechanically activated can be affected by the static magnetic field

o Battery-powered devices (laryngoscopes, monitors, etc.,) can suddenly fail to operate

o Some programmable infusion pumps may perform erratically. A PCA pump reversed flow, despite presenting normal displays to the user – a one-way valve stopped flow blood into the IV bag. A similar incident occurred with an insulin infusion pump

o A ventilator delivered inadequate inspiratory pressure

o Pacemakers can pace at the wrong point in the cycle & rapid pacing can occur due to RF field interactions

o ECG waveforms can be distorted (e.g., increased T-wave or ST segment) due to the static magnetic field interactions, & ECG signals can be misinterpreted (e.g., missed complexes) due to the gradient magnetic field interactions

· Acoustic injury from the loud knocking noise that the MRI scanner makes

· Adverse events related to the administration of MRI contrast agents

Nursing Staff, for Your Own safety

You must not accompany a patient into the MRI chamber if you are wearing any clothing containing metal

You must not accompany a patient into the MRI chamber if you are wearing dentures, hearing aids, hairpins, artificial prosthesis, jewelry, TENS unit, stimulators, support braces, makeup, holter monitor

You must not accompany a patient into the MRI chamber if you have had any surgery or trauma which has resulted in shrapnel or welding wounds

For your own safety you must not accompany a patient into the MRI chamber if you have any of the following:

o Cardiac valve prosthesis

o Cardiac pacemaker or pacer wire implant

o Intracranial aneurysm

o IUD

o Cochlear implants

o Joint replacements

o Metal plates or pins

o If you are pregnant

Remember

The magnets in the MRI scanner are always “on” and that turning them “off” (quenching) is an expensive and potentially dangerous undertaking

Many of the objects pulled into the MRI scanner are cleaning equipment or tools taken into the MRI suite by housekeeping staff or maintenance workers