ULTRASOUND-INDUCED LUNG HEMORRHAGE IN THE MONKEY

Studies with the mouse have shown that lung hemorrhage can result from exposure to ultrasound at a peak pressure of approximately 1 MPa at 4 MHz (Mechanical Index [MI] approximately 0.5). In order to determine whether a comparable outcome could occur in a larger animal with chara cteristics similar to humans, studies were performed with monkeys usin g a clinical scanner under maximum output conditions (imaging + pulsed and color Doppler; derated p, of 3.7 MPa [4.5 MPa, measured in water] , 4 MHz; MI approximately 1.8) (N = 57). Monkeys ranged in age from 1 day of life to 16 years with exposures limited to the right lung lobes (5 min cranial, 5 min caudal; N = 41 exposed, N = 12 sham-exposed con trols, N = 4 colony controls). Results showed that animals ranging in age from 3 months to 5 years (mean age of 2.5 years) had a greater pro pensity for the occurrence of multiple well-demarcated circular hemorr hagic foci (0.1-1.0 cm), which were not observed in either control gro up. These lesions were characterized by marked congestion of alveolar capillaries with accumulation of red blood cells within the alveolar s paces, and were unassociated with major vessels or respiratory bronchi oles. Further studies will be required in order to determine the relev ance of these findings to the human, although it was concluded that ul trasound-induced lung hemorrhage in the monkey is of a significantly l esser degree when compared to the mouse.