A, no injection; B, 5 × 104 MBVEGFR2; C, 2 × 105 MBVEGFR2; D, 1 × 106 MBVEGFR2; E, 1 × 107 MBVEGFR2; F, 5 × 107 MBVEGFR2. B-mode images overlaid with color-coded multi-frame compounding PI images (within the ROI) of the tumor for injection of MBVEGFR2. Green lines define the ROI of the tumor. Images were taken approximately 20 s after the injection of microbubbles. Scale bar in A represents 2 mm.