Ultrasonic modification of experimental bruising in the guinea-pig pinna

Both pinnae of anaesthetized male guinea-pigs were contused in a reproducible manner and one immediately treated with 0.75 MHz ultrasound at an average therapeutic intensity of 0.61 W cm-2 for a period of 2 min. The lividity and rate of resorption of the rusultant bruises were measured by a photometric method. The results fell into two distinct classes. In the majority of cases, the bruises formed on the insonated pinnae were significantly less intense and were resorbed at the same rate as their corresponding controls. In the remaining cases, ultrasonic irradiation resulted in an increased initial lividity and a significantly greater rate of resorption.