The influence of ultrasound frequency and gas-body composition on the contrast agent-mediated enhancement of vascular bioeffects in mouse intestine

The induction by ultrasound (US) of petechiae and hemorrhages in mouse inte stine was examined with injection of gas body-based contrast agents, Produc tion of petechiae in the intestinal wall was enhanced by contrast agents fo r both continuous and pulsed (10 mu s pulses repeated at 1 kHz) exposure re lative to a gas body-free blank. For pulsed exposure with 10 mL/kg of Albun ex(R), apparent thresholds for peak negative pressure amplitude were 0.42 M Pa at 0.4 MHz, 0.85 MPa at 1.09 MHz and 2.3 MPa at 2.4 MHz, Results at thes e frequencies were the same for 10-11 cycle pulses with fixed duty cycle (0 .01). Thresholds for hemorrhage into the intestinal lumen were not apprecia bly enhanced by added Albunex(R), and appear to be compatible with previous ly reported lithotripsy data when duty factor differences are considered. T he agents PESDA, Optison(R) and Levovist(R) had lower thresholds (for examp le, 1.8 MPa for Levovist(R)) than Albunex(R) at 2.3 MHz, and yielded more p etechiae, The thresholds for petechiae induction by US with contrast agents encroach upon the exposure range relevant to diagnostic US practice. (C) 2 000 World Federation for Ultrasound in Medicine & Biology.