A multi-frequency approach to increase the native resolution of ultrasound images

In ultrasound (US), a natural competition exists between the resolution of the image and the depth-of-field (DOF) into the medium, competition which is difficult to overcome with current US probe. Using large bandwidth transducer, such as cMUT, and the possibility to transmit several frequencies in one single transmission, we propose a multi-frequency scheme based on the frequency compounding (FC) technique to improve the native resolution of the US image and the DOF. In a first time, the different images at the different frequencies are created and a specific time-gain-compensation is used to compensate for the frequency attenuation. Then, the multi-frequency (MF) image is created in order to enhance the resolution and the SNR in the radio frequency domain. The resulting evaluations, through simulations and experiments, show a visible increase of the SNR and of the resolution. Moreover, the exploration depth is improved thanks to the attenuation compensation.