Improvement of ultrasound compound imaging by speed-of-sound estimation.

It is well known that the superposition of ultrasound images of the same object acquired from different directions reduces speckle and improves image quality. Philips/ATL were the first to overlay up to nine images using a phased linear array with different steering angles for real-time compound imaging. However, image quality suffers from speed of sound deviations from the velocity of 1540 m/s assumed by ultrasonic scanners. It has been shown that this is relevant in anatomical imaging and image quality can be improved significantly by estimating the speed of sound [1] and correcting for deviations. In this paper, average sound speed estimation based on a compound image quality criterion is discussed. Additionally, the criteria presented are evaluated for a simple case of local speed of sound estimation.