• Chapter 18 • Contents
  Introduction Incidental Hazards  External Objects  MR Equipment  Patient-Related Devices  Other Considerations Physiological Hazards   Static Magnetic Fields  Varying Magnetic Fields  Radiofrequency Fields Regulations and Legal Aspects 

---

Chapter Eighteen
Safety of Patients and Staff

18-01 Introduction

t the end of the 19th cen­tu­ry, x-rays represented a major step forward in dia­gnos­tic and therapeutic medicine, but then so­ber­ed physicians and the public after the ha­z­ards of ionizing radia­tion were de­tect­ed.

No ionizing radiation is involved in MR imaging. However, because of the re­­co­g­ni­z­ed problems with x-rays and radioisotope examinations, magnetic re­so­na­nce imag­ing and spectroscopy have been intensively examined for possible dan­ge­rous side ef­fects.

Any new method in medicine, be it diagnostic or therapeutic, must be tho­­rou­gh­ly checked for possible adverse effects — and magnets can have fatal at­trac­tions (Figure 18-01).

Figure 18-01:
Magnets can have fatal attractions — whether it is low field or high field.
Top: 900 Gauss (0.09 T) at Paul Lauterbur's first whole-body machine, or …
Bottom: … decades later at a clinical 1.5 T machine.

For a long time, only minimal and reversible physiological effects were reported from imaging and spectroscopy equipment operating below 2 Tesla.

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.

During the last 150 years, thousands of papers focusing on the effects or side ef­fects of magnetic or radiofrequency fields have been pub­li­shed. They range from anec­do­tal reports about therapeutic applications of mag­ne­tic fields as published by Zhang et al. [⇒ Zhang 1984], to reports on unwelcome side effects, such as Bei­scher’s study [⇒ Beischer 1962].

This overview cannot cover all potential sources of hazards. Numerous re­views of the literature have been put forth immediately after the introduction of MR imaging into clinical routine, e.g., by Budinger as early as 1981 [⇒ Budinger 1981], Rinck [⇒ Rinck 1983], by Persson and Ståhlberg [⇒ Persson 1985]; updates are published every so often, for instance in this textbook or, among others, by Budinger [⇒ Budinger 2016].

Several of the side effects as­so­ciat­ed with MR are unique to this kind of diagnostic tool; others are si­mi­lar to hazards of other diagnostic methods. These hazards can af­fect patients, personnel, and other persons within the field of the magnet.

Possible hazards can arise from or be connected to:

static magnetic fields;
varying magnetic fields (gradient fields);
varying magnetic fields (gradient fields);

and specifically:

devices necessary to operate the imaging equipment (such as cooling gases) or to ensure the quality of life of the patients (such as intracorporal implants and ex­tra­cor­po­ral monitors);

conducting loops such as electrical leads or accidental anatomical po­si­tions of the patient.

They can be categorized as incidental and physiological.

There is a wide range of incidental dangers that can lead to accidents (Figures 18-01 and 18-02). Nearly all accidents are incidental, caused by negligence (Table 18-01).

Table 18-01:
The three groups of accidents responsible for more than 90% of all reported injuries to patients and per­­son­nel. They are all caused by human negligence — by staff or patient — or the em­ploy­ment of in­ap­pro­pri­­ate or unsuitable equipment or devices.