The influence of ultrasound on embryonic development.

The chick embryo provides a convenient experimental subject to assess the effects of ultrasound on a developing biological system. Insonating the whole embryo prior to organogenesis with spatial peak temporal average intensities of 4.5 W/cm2 pulsed, and 100 W/cm2 continuous wave focused, produced no lethal effect or observable developmental changes during three days following the treatment. Any bio-effect which may have resulted from the interaction of ultrasound at the cellular level was not severe enough to bring about irreversible gross physical abnormalities in the developing embryo. The effects of standing waves or other extraneous physical factors were considered to be greatly reduced by irradiating embryos "in ovo" rather than in glass dishes following explantation.