Figure 1: Region of interest (ROI, 5 m m × 5 m m ) was placed in the middle of the six myocardial segments, and the ROI was tracked manually to assure its center position in each segment. The reperfusion curves of acoustic contrast intensity versus time were constructed automatically with QLab software. The specific values of signal intensity peak (A), the slope of slope of curve ( 𝛽 ), and perfusion volume ( 𝐴 × 𝛽 ) were acquired.