We study the physical phenomena and the application of HIFU using simulation and
experiment. The experiment was done with a bowl-shaped focused ultrasound
system. High speed videos of the generation of cavitation bubbles at the focal
point of the HIFU are captured. We observed interesting bubble cloud structures,
bubble movements and stationary bubble oscillations. The system is then applied
for dentistry applications. Firstly we use the HIFU to drive antibacterial
nanoparticles into dentinal tubules for disinfection in root canal treatment.
Initial results show delivery of these nanoparticle deep into the dentinal
channels which are a few microns in size. Next we cultivate E.
Faecalis biofilm, a common bacteria colony found in the mouth and teeth, on
petri dish and in human tooth. Then we subject them for removal under strong
HIFU for 1 to 2 minutes. We obtain positive results in the biofilm removal with
the increasing HIFU sonification time. We also simulate the interaction of a
bubble with pulsed ultrasound and in an ultrasound field near bio-materials such
as fat, muscle and bone. The simulation shows extreme growth and collapse of the
bubble under certain conditions. Also the formation and direction of the water
jet during bubble collapse is highly dependent on the properties of the
bio-materials nearby. These studies provide a foundation for better
understanding of HIFU and its uses in medical treatment.