[Ultrasound irradiation effects on pre-implantation embryos (author's transl)]

To elucidate ultrasound irradiation effect on pre-implantation embryos, its mechanism and safety levels of ultrasound intensity, I had performed ultrasound irradiation and thermal experiments on pre-implantation embryos. The pre-implantation embryos, whose stages were late morula on early blastocyst, were located in the centre of ultrasound beam certainly by using closed microdroplet culture. Experiments were done under various conditions of ultrasound intensity, irradiation time and temperature of circumference. The statistically significant increase of morphological abnormality was observed when 3.0 W/cm2 continuous wave for 60 minutes of 0.65, 1.0 or 1.8 W/cm2 continuous wave for 720 minutes was irradiated. The statistically significant developmental retardation was observed when 2.0 or 3.0 W/cm2 continuous wave for 60 minutes or 0.65, 1.0 or 1.8 W/cm2 continuous wave for 720 minutes was irradiated. Pulsed ultrasound irradiated groups showed neither increase of morphological abnormality nor developmental retardation significantly. The reading of thermistor sonde located in the centre of beam was raised during irradiation. No significant change were observed between warming and irradiated groups, temperature of which were similarly raised. Similar results were seen when 3.0 W/cm2 continuous wave for 60 minutes were irradiated during cool circumference, in which temperature of the centre of ultrasound beam didn't raise more than 37 degrees C. These results suggest that thermal effect of ultrasound is most effective during various effects including cavitation in this study.