  The importance of the excitation bandwidth is well known in diagnostic
ultrasound imaging. However, the effect of excitation bandwidth in therapeutic
applications of microbubbles has been mostly overlooked. A majority of contrast
agent production techniques generate polydisperse microbubble populations, so a
wide range of resonance frequencies exist. Therefore, wideband excitation is
necessary to fully utilize microbubble resonance behavior and maximize the
reradiated energy from a microbubble population, both for imaging and therapy.
  Oscillations of sixty SonoVue microbubbles in proximity of a rigid boundary
were captured on a high speed camera at 3 Mfps, excited with a peak negative
pressure of 50 kPa at 1 MHz. Measurements were analyzed according to their peak
radiated pressure, radial oscillations, root mean squared pressure, and shear
stress generated by microbubbles. Results showed that long duration and
wideband excitation at low intensity levels was preferable for sonoporation,
where microbubbles can be driven in a stable oscillation state without
experiencing inertial cavitation or destruction.

Medical Physics