A medical apparatus operable to induce localized hyperthermia in a patient via an electromagnetic field emitted by an antenna connected to an output of the medical apparatus includes a signal generator, a bidirectional coupler, and a controller. The signal generator generate radios frequency signal as a function of an operating parameter. The bidirectional coupler provides the radio frequency signal generated by the signal generator to the output and receives a reflected signal from the output. The controller receives the generated radio frequency signal from the signal generator, determines a power of the radiofrequency signal generated by the signal generator, receives the reflected signal from the bidirectional coupler, determines a power of the reflected signal, and determines delivery efficiency of the medical apparatus as a function of the power of the radiofrequency signal generated by the signal generator and the power of the reflected signal received from the bidirectional coupler.