Ultrasound-induced temperature increase in the guinea-pig fetal brain in vitro

The temperature of the brain of fetal guinea pigs was measured in vitro during exposure to an unscanned beam of pulsed ultrasound at intensity ISPTA 2.8 W/cm2. A mean temperature increase of 5.1 degrees C recorded after 2 min of insonation confirms results of an earlier similar study. The water-bath exposure system provided enhanced cooling of superficial tissue by acoustic streaming. When the scalp was removed, the ultrasound-induced temperature increase was substantially reduced (by 35%) due to cooling through radiation force-induced bulk fluid streaming along the direction of propagation in the water bath. The measured temperature increase in guinea pig fetal brain correlated with a modified cranial thermal index.