In high frequency focused ultrasound therapy, transient cavitation occurs in the kW/m^2 range, which is associated with tissue heating and damage. This is useful for various surgical techniques and tumor ablation. For instance, it takes 1 - 3 seconds to heat tissue to 70C with 1 kW/cm^2 [1]. Therapeutic ultrasound (for tissue hyperthermia) is performed in the 0.5 - 3 W/cm^2 range, and surgical ultrasound is typically above 10 W/cm^2. [2] It appears they've set the top end of their power delivery at just below the therapeutic range.
[1] http://link.springer.com/article/10.1134/1.1591291#page-1
[2] http://onlinelibrary.wiley.com/doi/10.1002/med.10004/pdf