While there are some differing types and designs of MRI machines, the most common are large cube like structures with average sizes of seven feet tall by seven feet wide and 10 feet long. Essentially the cube structure is a large magnet with a circular "tube" core. This core is called the "bore" of the machine and is where the patient is placed in the machine for imaging to take place. The machine maintains a strong magnetic field inside the bore.
When a patient is placed inside the bore the patient's body distorts the intensity of the magnetic field into varying energy waves. A computer used in conjunction with the machine interprets these energy waves and translates them into picture slices, two-dimensional or three-dimensional. These images are greatly detailed and allow a physician to determine injuries and illnesses such as; tumors, Multiple Sclerosis, torn tendons, tendonitis, and other life threatening injuries and health problems.
The benefits of these machines far outweigh the hazards. Exposure to magnetic fields has not been determined to be hazardous to humans. However, it is the construction and operation of the machines that produce hazards to firefighters.
First and foremost, MRI units are always on. There are never any times when the unit is shutdown. The magnetic field can extend up to 20 feet from the machine and draw or "pull" metallic objects toward it. These objects may be wrenched from the possessor's hands, fly through the air and into the bore area of the machine. Even small items such as badges, pens, eye glasses, watches and any metallic hand tools can become dangerous projectiles. Imagine coming into a smoke filled room in a building on fire and finding yourself literally being sucked into a room by a "force" you are unable to fight against or see, and subsequently losing control of a hoseline, your partner, a piece of equipment or a victim.
This may sound strange or exaggerated but there have been similar incidents. On July 27, 2001 a six-year-old boy was killed when a metal oxygen bottle was pulled into the bore while he was inside. Incidents such as this stress the need to be cognizant of this type of hazard when working on any type of incident, fire or medical, in a room where a MRI unit is present.
Second, a Liquefied Cryogenic Gas is used to cool the interior windings of the magnet while it is in operation. Typically, liquefied helium or liquefied nitrogen are used and are stored in cryogenic cylinders in a separate area or room away from the unit.
Now all of the hazards of hazardous materials response come into play. Temperatures of the liquefied gases range from -250 to -350 degrees F and are kept in low pressure cryogenic containers. Health hazards range from asphyxia, frost bite and frost freeze to pressure hazards from rupturing cylinders from heat of fire. Furthermore, the loss of cooling agent on the MRI magnets can lead to a fire developing in the MRI unit.
Magnetic Resonance Imaging units can be housed, contained and transported in a mobile unit. The MRI unit is in a semi-tractor trailer unit and may be equipped with a HVAC system and diesel generator. The idea behind this design is to transport MRI units to medical facilities that do not have an onsite unit. This makes the technology available to a wide geographical area and provides the life saving service to more individuals than a stationary MRI unit.
In this case the MRI hazards and operations are the same as previously mentioned but now you can factor in a diesel automotive apparatus with a diesel fueled electrical generator. Fuel sources should be monitored and removed during suppression operations. If possible disconnect the semi-tractor and remove it from the fire area.
As stated previously the MRI unit medical personnel should be involved in suppression, salvage/overhaul and investigation operations as much as safely possible.
Incidents involving Magnetic Resonance Imaging units pose a unique challenge to firefighters. MRI unit operational procedures and hazards must be thoroughly understood and preplanned. Strategies and tactics for fire suppression and investigation should be developed incorporating all known hazards to effectively and safely control incidents involving these types of machines.