EFFECTS OF PULSED ULTRASOUND ON SPHENOID BONE TEMPERATURE AND THE HEART-RATE IN GUINEA-PIG FETUSES

Temperature increase induced by exposure to unscanned pulsed ultrasoun d at an intensity (I-SPTA) 2.82 W/cm(2) was measured in the brain adja cent to the sphenoid bone of foetal guinea-pigs in late gestation unde r in vitro and in vivo (in utero) conditions. After 120 s exposure a m ean temperature increase of 2.6 degrees C was measured in vitro. Remov al of the overlying parietal bones increased this value to 5.2 degrees C. Mean temperature increases at the sphenoid bone recorded in utero were 1.5 degrees C live and 2.0 degrees C post mortem. Measurement of foetal ECG showed that ultrasound-induced heating of the hypothalamic region did not significantly alter foetal heart rate. (C) 1998 Elsevie r Science Ireland Ltd. All rights reserved.