ULTRASOUND-INDUCED TEMPERATURE INCREASE IN THE GUINEA-PIG FETAL BRAININ-VITRO

The temperature of the brain of fetal guinea pigs was measured in vitr o during exposure to an unscanned beam of pulsed ultrasound at intensi ty I-SPTA 2.8 W/cm(2), A mean temperature increase of 5.1 degrees C re corded after 2 min of insonation confirms results of an earlier simila r study. The water-bath exposure system provided enhanced cooling of s uperficial tissue by acoustic streaming. When the scalp was removed, t he ultrasound-induced temperature increase was substantially reduced ( by 35%) due to cooling through radiation force-induced bulk fluid stre aming along the direction of propagation in the water bath. The measur ed temperature increase in guinea pig fetal brain correlated with a mo dified cranial thermal index. (C) 1998 World Federation for Ultrasound in Medicine & Biology.