Optimal Control by Transmit Frequency in Tissue Harmonic Imaging

Ultrasound imaging systems usually work in open loop. The system control is thus a sine wave whose frequency is often fixed around two-thirds of the center frequency of the transducer in tissue harmonic imaging. However, this choice requires a knowledge of the transducer and does not take into account the medium properties. Our aim is to seek the command which maximizes the tissue harmonic contrast. We proposed an iterative optimization algorithm that automatically saught for the optimal frequency of the command. Both experimentally and in simulation, its value did not correspond to the usual value. The contrast can be improved by 5 dB. By providing a closed loop system, the system automatically proposes the optimal control without any a priori knowledge of the system or of the medium explored.