Fig. 5

Time history of total channel variance as a measure of cavitation activity for 30 s of HIFU. Each point represents one acquisition and is the sum of the 256 raw channel variances. a Averaged value from phantom trials, as well as the min and max values observed. The observed exponential decay is consistent with cavitation depletion and transient, noisy signals are indicative of cavitation bubble collapse. b Result of pork trials. In pork, a thermal lesion was observed after the 40 W single focus sonication