2pPAa4. Intestinal hemorrhage from exposure to pulsed ultrasound and lithotripter fields.

Session: Tuesday Afternoon, May 14

Author: Diane Dalecki
Author: Sally Z. Child
Author: Carol H. Raeman
Author: David P. Penney
Author: Edwin L. Carstensen
Location: Rochester Ctr. for Biomedical Ultrasound, Univ. of Rochester, Rochester, NY 14627


Using ultrasound with pulse lengths of 10 (mu)s and pulse repetition frequencies of 100 Hz, the thresholds for intestinal hemorrhage in mice after a 5-min exposure range from ~1 MPa at 1 MHz to ~4 MPa at 4 MHz. With a piezoelectric lithotripter, the threshold for intestinal hemorrhage after 200 pulses was 1--3 MPa. In neither case can the effects be explained by heating. As a test for cavitation, the extent of hemorrhage in the gas-containing intestines of pregnant mice was compared to the amount of hemorrhage in the gas-free intestines of their fetuses. On the 18th day of gestation, the abdominal regions of pregnant mice (n=6) were exposed to 200 pulses from a piezoelectric lithotripter. Acoustic pulses had a peak pressure amplitude of 10 MPa and were administered at a rate of ~1 Hz. All maternal intestines showed hemorrhagic regions extending several centimeters in length. In contrast, only 1 of 43 exposed fetuses showed an intestinal hemorrhage and this one lesion was less than one millimeter in diameter. These are consistent with a cavitation-related mechanism for the production of intestinal hemorrhage by exposure to acoustic fields.

from ASA 131st Meeting, Indianapolis, May 1996