Ultrasound-induced temperature increase in guinea-pig fetal brain in utero: Third-trimester gestation

Temperature increase was measured at various depths in the brain of living fetal guinea pigs during in utero exposure to unscanned pulsed ultrasound a t I-SPTA 2.8 W/cm(2), Mean temperature increases of 4.9 degrees C close to parietal bone and 1.2 degrees C in the midbrain were recorded after 2-min e xposures. When exposures were repeated on the same sites in each fetus afte r death, the corresponding mean temperature increases were 4.9 degrees C an d 1.3 degrees C, respectively. Cerebral blood perfusion had little cooling effect on ultrasound-induced heating in the guinea pig fetus of 57-61 days gestational age. (C) 1998 World Federation for Ultrasound in Medicine & Bio logy.