The construction and operation of the machines that produce hazards to firefighters.
Advances in medical procedures have greatly enhanced the lives of millions of people throughout the world. One area of advancement has been through the development of Magnetic Resonance Imaging or MRI. Images created by these devices have greatly improved the ability of physicians to see inside a patient's body without performing risky surgery. The MRI far outweighs X-rays in clarity and in many cases the surgeon can see a two-dimensional or three-dimensional image of the organ, body cavity or skull of the patient.
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.
Fire Suppression & Alarm Systems and Safety
Rooms and buildings containing MRI units should be designed and constructed to all applicable building and fire codes. Special precautions should be designed into the room to control magnetic issues. Sprinkler pipes or other types of fire suppression system piping should be non-ferrous piping. Sprinkler heads should be approved for the intended application. Fire alarm components should also follow these guidelines. A non-metallic fire extinguisher should also be required when an extinguisher is placed within a room containing MRI equipment.