High resolution ultrasonic attenuation estimation with a random phase screen

A novel method is presented for increasing the spatial resolution in attenuation measurements. A random phase screen (RPS) is placed in front of the transducer. The RPS introduces a random phase on the elementary waves scattered by individual scatterers located in the insonified volume. Different locations of the RPS produce different patterns of interference at the front face of the probe. Uncorrelated echographic lines are obtained by shifting the RPS in the ultrasonic field. Thus, without moving the transducer, a significant decrease of the statistical variance on the attenuation measurement is reached. The authors present the effect of the RPS on the beam profile and show that under optimal experimental conditions the beam is weakly spread. They give quantitative results on the increase of the SNR (signal-to-noise ratio). The reduction of the size of the resolution cell gained with a RPS shows that it is promising for local attenuation measurements.<>