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Electromagnetic Fields in Biological Systems
exposure could reach up to 26  W/kg at gonads and up to 7 W/kg at the fetus. Such
high values might lead to unacceptable side effects, in particular because this could be
avoided by proper choice of the type of applicator or proper adjustment of output power
(Leitgeb, Omerspahic, and Niedermayr 2010).
These results reinforce warnings that sensitive regions may be subjected to unintended
overexposures such as the eye lens (because of the impaired heat exchange and hence the
risk of cataracts) and reproductive organs. If such overexposures were encountered, they
were associated with inductive applicators rather than capacitive ones.
Numerical investigations with a pregnant woman model concentrated on treatment
locations close to the amniotic sac (hip and spine). It could be demonstrated that fetal
overexposure can occur, however, not at any treatment. During hip treatment with
inductive applicators, fetal exposure exceeded the exposure limit up to 3.6-fold (Leitgeb,
Omerspahic, and Niedermayr 2010).
6.2.1.2.1.2 Staff It is well known that emitted RF stray fields may interfere with other
electromedical devices and electronic implants (Irnich, de Bakker, and Bisping 1978;
Pinski and Trohman 2002).
However, there are also established risks of overexposing medical staff. Measurement
programs in the working environment (Li and Feng 1999; Martin, McCallum, and
Heaton 1990; Moseley and Davison 1981; Shah and Farrow 2007, Shields, O’Hare, and
Gormley 2004; Stuchly et al. 1982; Tuschl et al. 1999) found stray RF EMF considerably
exceeding International Commission on Non-Ionizing Radiation Protection (ICNIRP)’s
exposure limits (ICNIRP 1998). Occupational limits for medical staff were exceeded up
to a distance of 2 m from devices and for accompanying persons up to 2.5 m.
Except for epidemiologic studies performed on pregnant women subjected to diathermy (Lerman, Jacubovich, and Green 2001; Quellet-Hellstrom and Stewart 1993),
so far, little scientific attention has been given to excess patient’s exposure. Guidelines
for use (NHMRC 1985) restrict or even ban the treatment of pregnant women but only
generally recommend reducing the exposure of sensitive regions such as eye lenses and
gonads without giving specific advice, and other guidelines aim at protecting the operator only (HC 2008). An investigation among 116 senior physiotherapists in 41 Irish
hospital-based physiotherapy departments discovered inadequate safety practices and
the urgent need for guidelines for safety of operators, patients, and the public during
diathermy (Shields, Gormley, and O’Hare 2006).
6.2.1.3 Heat Therapy
In heat therapy, also called thermotherapy, heat is applied to the body via different
sources, among them electrical medical devices such as electric heating blanks, pads,
and mattresses or low-temperature infrared cabins with intended medical use.
6.2.1.3.1 Heating Blankets
Because the patient is in close vicinity to the wiring of electric heating blankets, pads,
and mattresses, local exposure to magnetic fields can be relevant. However, it decreases
rapidly with increasing distance and varies considerably depending on the placement
of heating wires. Lowest magnetic fields are produced by bifilar mounted filaments