The direct and indirect effects of radiofrequency electromagnetic fields are also used in medical treatment processes (e.g. thermal therapy, radiofrequency surgery or radiofrequency ablation). In the thermal therapy, local temperature increases are generated by the fields, which heat the tissue at certain sites of the body to achieve a therapeutic effect. In diathermy applications in the frequency range from approximately 13 MHz to 430 MHz, depths of penetration of more than 20 cm are achieved (cf. “figure depth of penetration of radiofrequency fields” in chapter Radio frequency (10 MHz–300 GHz)). The microwave therapy is conducted at 2.45 GHz and it has a depth of penetration of a few centimeters, depending on the water content of the tissue. Powers of up to several hundred watts with partial body SAR values of 10 to 50 W/kg are applied in microwave therapy.