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Electromagnetic Fields in Biological Systems
electromagnetic interference (EMI) with life-support devices (ventilators and electrocardiographic devices), which may fail to operate correctly. Most clinically relevant
interference occurred when an RF surgery device was used within 0.3 m of other
medical equipment (De Marco and Maggi 2006). In the vicinity of electrosurgical
devices, medical staff could be critically exposed up to a distance of 70 cm from the
active electrode and its supplying cable. Considerable overexposure was encountered
when the electrode cable was placed directly on the surgeon’s body. The current flowing through the arm of the surgeon holding the electrode can exceed the permissible value of 40 mA, and electric field strength may exceed 1000 V/m (Gryz and
Karpowicz 2006).
6.4.1.2 Diathermy
In SWD, 10 units in six departments were examined with regard to their stray fields.
It was found that stray fields from capacitive SWD fell below operator limits only at
2 m (electric field strength 4.8–39.8 V/m; magnetic field strength 0.015–0.072 A/m)
and at 1 m for inductive SWD (0–36 V/m; 0.01–0.065 A/m). Capacitive pulsed SWD
fields fell below the limits at 1.5 m (1.2–19.9 V/m; 0.002–0.045 A/m) and at 1 m for
inductive pulsed SWD (0.7–4.0 V/m; 0.009–0.03 A/m). An extra 0.5 m was required
before fields fell below recommended limits for other personnel. These results demonstrate that under a worst-case scenario emissions from SWD exceed the guidelines for operators at distances currently recommended as safe (Shields, O’Hare, and
Gormley 2004).
In eight physiotherapy departments, 11 microwaves, four SWD, and 15 magneto therapy devices were analyzed, and cases of exposures exceeding occupational limits were
identified (Maccá et al. 2008).
6.4.2 Risk Management
To manage risks from such interference several measures may be taken:
•   Developing guidelines for use (Gombotz et al. 2009; Joshi 2009) and performing
treatment planning (Habash et al. 2007) to minimize unintended exposure during treatment (e.g., diathermy and hyperthermia)
•  Identifying zones of restricted access
•  Warning against EMF around powerful EMF sources (e.g., MRI)
•  Preventing excessive exposure of workers by workplace assessment, training,
exposure minimization, and/or shielding as required by worker protection legislation (e.g., EC 2004)
•  Improving immunity of medical devices against EMI as required by the electromagnetic compatibility (EMC) standard for medical devices (IEC 60601-1-2) or for
medical implants (IEC 45502-1). As an example, in the frequency range 150 kHz–
80 MHz, the required immunity level is E i = 3 V/m for general medical devices
and 10 V/m for life-supporting medical devices (IEC 60601-1-2). Implanted cardiac
pacemakers should not work outside the manufacturer’s tolerances up to a signal
input interference voltage of 2 mV pp (IEC 45502-1)