A novel optical reflection model accurately measures arterial surface accumulation of Evans blue dye to indicate transvascular protein flux.
May enable preclinical quantification of vascular permeability; leaves open human validation and clinical translation.
Parenteral Evans blue dye (EBD) binds to albumin and thus can indicate transvascular protein flux. A model was developed to relate the arterial surface accumulation of EBD to the light refected from the opened vessel surface. The accumulation, M (nmol cm-2), was related to the optical "absorbance" (rho) of the surface by the equation, M = 3.92 rho + 0.80 rho3, where rho = -ln(I/I0) and I and I0 are the intensities of light reflected from the surface in the stained and unstained state, respectively. The validity of the model was examined in two ways, 1) by comparing the value of the optical absorption coefficient for EBD predicted by the model to the measured value: the predicted value was 0.128 +/- SD 0.015 cm2 nmol-1, the measured value was 0.125 +/- SD 0.005 cm2 nmol-1; and 2) by comparing predicted changes in vessel wall stretch to measured values: the percentage changes (Y) in area predicted by the model from changes in M were linearly related to the directly measured percentage area changes (X) by Y = 0.09 + 1.01X, +/- SD 2.54, with a correlation coefficient of 0.994.
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D. L. Fry (1977) studied this question.
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