An automated ultrasonic exposure system to assess the effects of in utero diagnostic ultrasound

An ultrasound exposimetry system was designed and constructed to expose rat embryos and fetuses to ultrasound. The unique feature of the exposure system is that it insonates pregnant rats which are not anesthetized or otherwise restrained. The rats were trained to float in a restricted area directly above the submerged ultrasound transducer. The water tank was designed to confine the floating rat to a 15-cm×10-cm region while being exposed to ultrasound. The ultrasound transducer operating in either pulsed or continuous-wave (CW) mode is submerged below the animal and moved in a raster fashion to irradiate the entire abdominal area. Computer control of the exposure system and the ultrasound intensity levels allow for the experiments to be conducted in a blind fashion. Using a calibrated hydrophone, pressure waveforms are obtained from which the free-field I_SPTA and I_SPTP are calculated at the distance of the rat´s abdomen