“…Incidental or deliberate exposure of the human lung occurs during a variety of specific ultrasound examinations, including routine and transesophageal echocardiography and chest wall, pleural space, diaphragm, and lung parenchymal evaluations; the intestine, however, is always exposed whenever an abdominal organ is examined and during most obstetrical and gynecologic studies. Using a variety of experimental models, a number of investigators have shown that the threshold acoustic pressure for lung hemorrhage across species is 1 MPa (Mechanical Index [MI] 0.5) with a weak correlation with frequency, pulse length, and total exposure time (Section 4) (Child et al, 1990;Raeman et al, 1996). At the present time, data are inconsistent as to whether there are age or species differences in the thresholds for lung hemorrhage, although animals may be grouped into those species with "thin" visceral pleura (mice, rats, rabbit, cats, dogs, and monkeys), which are more susceptible to lung hemorrhage, versus species with "thick" visceral pleura (sheep, pigs, humans, cattle, and horses) who may be relatively protected from mechanical bioeffects, as discussed in Section 3 (Frizzell et al, 1994;Zachary and O'Brien, 1995; Baggs et al, 1996;O'Brien and Zachary, 1996; Dalecki et al, 1997b Dalecki et al, , 1997a.…”