Power modulation is a non-linear method, based on a multi-pulse technique where the acoustic amplitude (and hence power) of the transmitted pulses is changed. Full and half amplitudes pulses are used to induce changes in the response of the contrast agent. The received echoes from the emitted half amplitude pulse are adjusted with the full amplitude pulse and this pairs of pulses are subtracted. Power modulation is used to separate contrast agent echoes at low mechanical index, allowing real-time perfusion imaging.
Power modulation can be used with a low frequency wide band transducer to increase the depth and transmit the sound beam homogenous allowing ultraharmonic imaging.