Figure 6

In-vivo ultra-harmonic acoustic response for 3 different agents after a bolus injection lasting 2 seconds. Ultrasound sonication started simultaneously with the injection of agent and lasted for 120 seconds. The three agents were diluted to form a sample with gas volume of 1.1–1.2 µl/ml. The final dose was then calculated accordingly to match the conventional dose for BBB opening in rodents. (a) The AUC at 0.75 MHz exhibited a significant increase followed by return to baseline for each of the three agents. (b–d) are the corresponding frequency spectrum for three agents respectively. The nanobubble exhibited the longest circulation time of all the agents, with an AUC still detectable after 120 seconds.