Figure 4a:

Graphs show results of in vivo imaging of intramural free dye collections in rat aorta. (a) Raw AF633 signal intensity measured endovascularly from a free dye collection in rat aorta. Owing to variations in blood volume and in thickness of the vessel wall intervening between imaging catheter and dye collection, signal intensities for raw AF633 correlate poorly with concentration of dye. (b) Corrected AF633 signal intensity after division by AF750 fluorescence. After correction with simultaneously acquired AF750 signal, AF633 signal intensity curves exhibit much improved correlation with dye concentration relative to one another. arb = arbitrary units.