Fig. 10

Final temperature rise after 30 s of HIFU (averaged over the ROI) vs. cavitation activity. Points correspond to 5, 10, 20, 40, 60, and 80 acoustic watts (in pork, single-focus MR data wasn’t collected above 40 W due to lesion formation). a Averaging over 1-s in phantoms (prior to bubble depletion) shows less cavitation at a given input power in both 4 mm and 8 mm cases. b Averaging over the full 30 s sonication, 8 mm multi-focusing achieves an average rise in the mild heating range (+3-8 °C) above 20 W with generally less cavitation at each input power level. At 40 W total cavitation activity is comparable between the two, but this is likely due to initial rapid depletion of bubbles in single focus (see Discussion). c Negligible cavitation activity was observed with multi-focusing in pork. The large jump in channel variance at 40 W, pork, single-focus may be a result of lesion formation, cavitation, or both