High intensity focused ultrasound and microbubble induced tissue ablation: Effect of treatment exposure on thermal lesion volume and temperature

High intensity focused ultrasound (HIFU) with microbubbles has demonstrated the enhancement of the therapeutic efficacy of HIFU. The ultrasonic intensity for inducing cavitational bioeffects can be reduced by orders of magnitude with administration of such an agent externally. The current study investigates the effects of ultrasound treatment parameters and microbubble concentration on the HIFU lesion volume and temperature. In the active group, larger tissue volume was coagulated in the presence of MBs, despite equal exposure time. This shows that the MBs enhance the tissue ablation induced by HIFU. HIFU causes localized tissue temperature rise because ultrasound energy is converted to heat. However, the lesion volume for the USMB treatment rose at higher rate then the US treatment. This indicates that the mechanisms other then thermal damage also play role in the tissue damage. Theoretically these results can be explained by thermal damping, viscous damping and acoustical damping.