Hemolysis in vivo from exposure to pulsed ultrasound

Ultrasonically induced hemolysis in vivo was studied when a commercial ultrasound contrast agent, Albunex(R), was present in the blood, Murine hearts were exposed for 5 min at either 1.15 or 2.35 MHz with a pulse length of 10 mu s and pulse repetition frequency of 100 Hz, During the exposure period, four boluses of Albunex(R) were injected into a tail vein for a total of similar to 0.1 mL of Albunex(R), Following exposure, blood was collected by heart puncture and centrifuged, and the plasma was analyzed for hemoglobin concentration, With Albunex(R) present in the blood, the threshold for hemolysis at 1.15 MHz was 3.0 +/- 0.8 MPa (mean +/- SD) peak positive pressure (similar to 1.9 MPa negative pressure, similar to 180 W cm(-2) pulse average intensity), For the highest exposure levels (10 MPa peak positive pressure at the surface of the animal), the mean value for hemolysis was similar to 4% at 1.15 MHz and 0.46% at 2.35 MHz, i.e., the threshold at 2.35 MHz is > 10 MPa peak positive pressure, In contrast, hemolysis in control mice receiving saline injections at 10 MPa or sham-exposed (0 MPa) mice receiving Albunex(R) was similar to 0.4%. (C) 1997 World Federation for Ultrasound in Medicine & Biology.