Exposure levels for lung hemorrhage and other bubble effects in vivo.

Abstract

The lungs of neonatal mice were exposed insitu to 1-MHz pulsed ultrasound (10-μs pulse duration, 1-kHz pulse repetition frequency) for durations of 2.4 and 180 s at 10 °C. The neonates were mounted in a special holder that was placed in a tank of physiologically compatible coupling medium such that the broad focal region of the transducer was centered on the dorsal surface overlying the lungs. After removal of the animal from the holder the lungs of sonicated and sham control animals were carefully removed and examined under a dissecting microscope by a second person, who did not know whether the specimen was a sham or sonicated animal, for signs of hemorrhage. The threshold levels for lung hemorrhage are well below those for bubble effects reported in other tissues, but in good agreement with levels reported for hemorrage in adult mouse lung [S. Z. Child etal., Ultrasound Med. Biol. 16, 817–825 (1990)]. The dependence upon on-time for the lung hemorrhage was similar to that for bubble effects in other tissues.