Technical basis for the application of localized hyperthermia

Techniques of localized hyperthermia have been developed these last years. Very superficial tumors may be heated by infra-red radiation, radiative diathermy at high frequencies (2450 MHz) or even by techniques of contact hyperthermia. Superficial tumors (some cm deep) may be heated by radiative diathermy at lower frequencies (434 MHz or 915 MHz), inductive diathermy or ultrasound. Deeper tumors (about 10 cm deep) are the most problematic. They may be heated by capacitive diathermy at frequencies of 13.5 or 27 MHz under favourable conditions, or perhaps by ultrasound when multiple transducers are used. Hyperthermic extracorporeal perfusion (in limbs) and interstitial hyperthermia are efficient and promising techniques but their indications are limited.