Measurement of velocity of propagation from ultrasonic pulse-echo data

A method is proposed for determining velocity of propagation of ultrasound in tissue by processing the pulse-echo data obtained from a compound scan. Individual sectors from different transducer positions are reconstructed and a suitable area common to the two sectors is selected. Cross-correlation of the region of interest is used to detect an apparent shift in the image due to refractive effects. The refractive effects are analysed by a ray-tracing procedure to determine an effective velocity within the tissue. The system has been tested using the U.I. Octoson as input device and both model targets with known velocity of propagation and in vivo liver tissue. The accuracy in the model experiment was +/- 5 ms-1 while the repeatability of measurements in tissue was +/- 15 ms-1. techniques for extending the method to multiple region systems are suggested.