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Safety first or last?

Rinckside 2020; 31,1: 1-2.

ooking at and reading about the incidents during MR examinations last year one gets the impression that safety of patients and personnel seems to have become a neglected topic and incidents seem to increase because there is a lack of information and train­ing.

The accidents in Sweden have been clearly provoked by thoughtlessness — they seem simply self-inflicted.

MR machines are not toys and operating them requires concentration as well as knowing and not forgetting the rules. There is also a lack of hierarchy and strictness of the su­periors as there is a lack of due diligence, dutifulness and sense of responsibility by healthcare managers and administrators. If there is a police inquiry in Sweden, these bureaucrats should be included too.

During the last 150 years, thousands of papers focusing on the effects or side effects of magnetic or radiofrequency fields have been pub­li­shed. They can be categorized as incidental and physiological. There is a wide range of incidental dangers that can lead to accidents. They are all caused by human negligence — mostly by staff, occasionally by patients — or the em­ploy­ment of inappropri­ate or unsuitable equipment or devices.

Incidental hazards are created by the static magnetic field usually covering an ellips­oid region around the isocenter of the magnetic resonance machine. The range of this fringe or stray field depends on the field strength of the system, the type of magnet, and the kind of shielding used. The fringe field around the magnetic re­so­nan­ce system may stretch into ad­ja­cent rooms, floors, even gardens and parking places outside the building. It both influences electronic equipment and can be a possible hazard to per­sons passing by.

Ap­pro­pri­ate warning signs must be posted. In this case, warning signs or si­mi­lar no­tices should be displayed out­side the magnet room, in neigh­bor­ing rooms on the same floor, and on floors above and below. This danger has been reduced by shielded mag­nets.

­Ultralow- and low-field magnets possess a limited stray field of sometimes less than one meter radius from the isocenter of the magnet. The stray field of large bore, high field systems may cover a radius of 15 or 20 meters, unless the magnet is heavily shielded.

   Three groups of accidents are responsible for more than 90% of all reported injuries to patients and per­sonnel.

The most common hazards are temporary or lasting auditory damages to patients whose ears were not adequately protected, usually at high (1.5 Tesla) or ultrahigh fields (3.0 and 7.0 Tesla). Other hazards are second or third degree burns or blisters and skin redness caused by, for instance, ECG leads or similar sources.

The most publicly discussed injuries are created by ferromagnetic objects (‘projec­tiles’) attracted by the magnet attached to the patient or to people entering the magnet room, as those in Sweden.

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Constant education and obligatory safety drills for everybody involved in MR imag­ing are vital.

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Constant education and obligatory safety drills for everybody involved in MR imag­ing are vital. Every per­son working or entering the magnet room or adjacent rooms with a magnetic field has to be instructed about the dangers. This should include the in­ten­si­ve care staff, and maintenance, service, cleaning and security personnel, as well as the crew at the local fire station.

The best protection against this danger is not to allow per­son­nel other than those di­rectly involved in patient examinations — i.e., the operator and the radiologist — into the magnet room by building the room with a closed and controlled access. As a general rule, access to the magnet room should be limited to trained and respon­sible per­son­nel or to thoroughly screened patients and visitors who are accompanied by trained personnel.

Although to date there is no proof of any permanent damages to patients or staff cau­sed by the magnetic or radiofrequency fields of commonly used clinical MR equip­ment, for some years negative health effects on humans have been increasingly pub­lished — mostly concerning ultrahigh machines between 3 T and 7 T and involving both patients and employees [1].

   Considering the importance of MRI safety, the European Magnetic Resonance Forum and The Round Table Foundation offer a free (personal) offprint of the chapter on safety from their recent 12th edition of their textbook Magnetic Resonance in Medicine • A Critical Introduction.

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References

1. Rinck PA. MR safety update: Why we may not need a 20-Tesla MRI machine. Rinckside 2016; 27,6: 13-15.

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Citation: Rinck PA. Safety first or last? Rinckside 2020; 31,1: 1-2.

A digest version of this column was published as:
MRI safety first? Or last?
Aunt Minnie Europe. Maverinck. 9 January 2020.

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