Fig. 9.

Representative high speed photography frames illustrating fanned-out proliferating cavitation bubbles observed at the end of a single 1 ms HIFU pulse produced by a 1 MHz transducer with F-number=1.52, p⁻ = 9 MPa at increasing concentrations of agarose gel: 1.5%, 3% and 5% (top to bottom). The spatial distribution of new bubbles originating from each proliferating bubble, outlined with dotted yellow lines, became smaller with increasing agarose concentration, and therefore increasing elastic modulus and viscosity. Scale bar is 1 mm.