Experimental procedures of van Steveren et al. to determine Intralipid optical properties

  • Measure the on-axis, narrow solid angle transmission, T = exp(-(mus + mua)L), through a cuvette with various dilution fractions (f) of the 10% Intralipid stock. The pathlength of the cuvette is L [cm]. Determine the scattering coefficient of the original 10% Intralipid:
    mus = (-ln(T)/L)/f - mua

    for each dilution f. The value of mua is about 0.01 cm-1 in this wavelength range has little effect on the value of mus. All the values of mus should be in agreement until too high concentrations of Intralipid are tested and multiple scattering causes the apparent mus to decrease.

  • Measure the radial dependence of fluence rate, F [W/cm2]:
    F(r) = (constant) exp(-mueff*r)/r

    where r is the distance from source to collection fiber, to determine
    mueff = sqrt(3*mua*(mua + mus')).

    Deduce mueff and mueff+absorber for the Intralipid (10% lipid) with and with added absorber (Evans Blue). Deduce mus' and mua.

  • Combine mus and mus' to yield g.

  • In summary, measurements of F(r), F(r)+absorber, and T yield mua, mus, and g, and the lumped term mus' = mus(1-g).