AN EVALUATION OF SAFE PRACTICES TO RESTRICT EXPOSURE TO ELECTRIC AND MAGNETIC-FIELDS FROM THERAPEUTIC AND SURGICAL DIATHERMY EQUIPMENT

Stray electric and magnetic fields have been measured near to therapeu tic and surgical diathermy equipment for many different treatments. Th e highest field strengths are associated with continuous wave (CW) 27 MHz therapeutic diathermy equipment for which fields above national re ference levels extend for 1 m from the electrodes and cables. The exte nt of the fields does not vary substantially with the type of treatmen t being performed. Recommendations that operators remain 1.0 m from CW therapeutic diathermy equipment, 0.5-0.8 m from pulsed treatments wit h capacitive electrodes and 0.2 m from pulsed inductive applicators ca n be applied to restrict exposure for any treatment with each type of unit. In a proposed European Community (EC) directive, action levels s imilar in magnitude to the reference levels are used to trigger requir ements for assessments of hazard, measures to reduce exposure and pers onnel training. Assessments and appropriate recommendations of measure s to reduce exposure can be linked to the type of equipment. Fields as sociated with electrosurgical units operating at frequencies of 0.3-0. 5 MHz only approached reference levels within 20-30 cm of the cables, and because of the relatively short durations of the emissions, precau tions were considered unnecessary with the units tested.