In vitro detection of cavitation induced by a diagnostic ultrasound system

Experiments were performed to determine whether a clinical diagnostic scanner, a Hewlett-Packard (HP) 77020A, could produce cavitation in water containing suspensions of either 0.245- mu m polystyrene spheres or Albunex, 1-10 mu m albumin-coated microbubbles. Two calibrated, phased-array HP imaging transducers with 2.5- and 5.0-MHz operating frequencies were driven in M-mode (single cycle) and Doppler mode 4 cycles by the HP imaging system. Cavitation was detected in the water with polystyrene spheres at 2.5 MHz in both M-mode and Doppler mode at a peak negative acoustic pressure of 1.1 MPa or greater. Insonification at 5.0 MHz in either mode did not produce a detectable amount of cavitation, even with peak negative pressures as high as 1.2 MPa. Cavitation was not detected in water with the Albunex spheres at either frequency.