Background Liquid core nanodroplets containing condensed gaseous fluorocarbons can be vaporized at clinically relevant acoustic energies, and have been hypothesized as an alternative ultrasound contrast agent instead of gas-core agents.The potential for targeted activation and imaging of these agents was tested with droplets formulated from liquid octafluorpropane (C3) and 1 ∶ 1 mixtures of C3 with liquid decafluorobutane (C3C4).Methods and Results In eight pigs with recent myocardial infarction and variable degrees of reperfusion,transthoracic acoustic activation was attempted using 1.3~1.7 MHz low (0.2 mechanical index or MI) or high MI (1.2 MI) imaging in real time (32~64 Hertz) or triggered 1 ∶ 1 at end systole during a 20% C3 or C3C4 droplet infusion.Any perfusion defects observed were measured and correlated with delayed enhancement magnetic resonance imaging and post mortem staining.No myocardial contrast was produced with any imaging setting when using C3C4 droplets, or C3 droplets during low MI real time imaging.However,myocardial contrast was observed in all eight pigs with C3 droplets when using triggered high MI imaging (figure 1), and in five of six pigs who had 1.7 MHz real time high MI imaging.Although quantitative myocardial contrast was lower with real time high MI imaging than 1 ∶ 1 triggering,the correlation between real time resting defect size and infarct size (figure 2) was good (r=0.97,P<0.001),as was the correlation with number of transmural infarcted segments by delayed enhancement imaging.