Fig. 2: Discovery of the acoustic loudness factor.

Structures (a) and photophysical properties as well as PA intensities (b) for a panel of structurally diverse NIR dyes. Relative PA emission intensity plotted versus photoacoustic brightness factor (PABF) (c) or acoustic loudness factor (ALF) (d). Trendlines represent fits from linear regression. Photophysical properties were measured in triplicate in DPBS:MeCN (7:3, 1% DMSO). PA emission is from quantification of PA images of 1.2 cm thick tissue phantoms at positions 2 mm apart.