Role of pulse repetition frequency and exposure duration in mice and rats with lung hemorrhage induced by exposure to superthreshold pulsed ultrasound

Abstract

Superthreshold behavior for ultrasound-induced lung hemorrhage was investigated in adult mice and rats at an ultrasound center frequency of 2.8 MHz to assess the role of pulse repetition frequency (PRF) and exposure duration (ED). One hundred fifty 6-to-7-week-old mice and 150 10-to-11-week-old rats were each divided into 15 exposure groups (10 animals per group) for a 3-by-5 factorial design (3 EDs: 5, 10, 20 s; 5 PRFs: 25, 50, 100, 250, 500 Hz). The in situ (at the pleural surface) peak rarefactional pressure of 12.3 MPa [MIs of 6.3 (mice) and 7.1 (rats)] and the pulse duration of 1.42 μs were the same for all ultrasonically exposed animals. The lesion depth and surface area were measured for each animal as well as the percentage of animals with lesions per group. The proportion of lesions in both species was related statistically to PRF and ED, with the exception that PRF in rats was not quite significant; the PRF×ED interaction (number of pulses) for lesion production was not significant for either species. The PRF, but not ED, significantly affected lesion depth in both species. Both PRF and ED significantly affected lesion surface area in mice. [Work supported by NIH Grant No. HL58218.]