Fig. 1.

Infrared fluorescence of indocyanine green (ICG) is more intense in dilute condition with weaker green color than in concentrated condition.

A. Commercial ICG green kit. B. Photos of 0.25% ICG aqueous solution (right vial) and 0.002% ICG aqueous solution (left vial). 0.25% ICG solution is dark green in color, while 0.002% ICG aqueous solution is faint green. Near infrared (NIR) fluorescence images were obtained using fluorescence imager. C. NIR image with excitation light on. 0.002% ICG aqueous solution (left vial) shows intense fluorescence with minimal background.