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Chapter 18

18-01
Introduction

18-02
Incidental Hazards

External Objects
MR Equipment
Implants and Devices
Other Considerations 18-03
Physiological Hazards

Static Magnetic Fields
Varying Fields
Radiofrequency Fields 18-04
Regulations and Legal Aspects


Chapter Eighteen
Safety of Patients and Personnel

18-01 Introduction

ny new method in medicine, be it diagnostic or therapeutic, must be tho­rough­ly checked for possible adverse effects. At the end of the 19th  cen­tu­ry, x-rays represented a major step forward in 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. During the last 150 years, hundreds of papers focusing on the effects or side effects of magnetic or radiofrequency fields have been pub­li­shed. They range from anecdotal reports about therapeutical 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].

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 employees working with ultra-high machines between 3 T and 7 T. On the other hand, there are real incidental dangers that can lead to accidents (Figure 18-01 and Figure 18-02).



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

Figure 18-02:
"Are you wearing any metal?" Repetitive and detailed screening questions prior to an MR imaging examination are the best precaution against harm and injuries.


This overview cannot cover all potential sources of hazards. Numerous re­views of the literature have been published 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 medical diagnostic tool; others are si­mi­lar to hazards of other diagnostic methods. Possible hazards can arise from or be connected to:

spaceholder 600 static magnetic fields;
spaceholder 600 varying magnetic fields (gradient fields);
spaceholder 600 radiofrequency fields;

and specifically:

spaceholder trtf-yellow 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);
spaceholder trtf-yellow conducting loops such as electrical leads or accidental anatomical po­si­tions of the patient.

These hazards can affect patients, personnel, and other persons within the field of the magnet. They can be categorized as incidental and physiological. 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 [⇒ Rivi FDA].
Table 18-02 lists potential contraindications to MR examinations.

spaceholder 600 spaceholder 600

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