A literature review and novel theoretical approach on the optical properties of whole blood

Optical property measurements on blood are influenced by a large variety of factors of both physical and methodological origin. The aim of this review is to list these factors of influence and to provide the reader with optical property spectra (250–2,500 nm) for whole blood that can be used in the practice of biomedical optics (tabulated in the appendix). Hereto, we perform a critical examination and selection of the available optical property spectra of blood in literature, from which we compile average spectra for the absorption coefficient (μ(a)), scattering coefficient (μ(s)) and scattering anisotropy (g). From this, we calculate the reduced scattering coefficient (μ(s)′) and the effective attenuation coefficient (μ(eff)). In the compilation of μ(a) and μ(s), we incorporate the influences of absorption flattening and dependent scattering (i.e. spatial correlations between positions of red blood cells), respectively. For the influence of dependent scattering on μ(s), we present a novel, theoretically derived formula that can be used for practical rescaling of μ(s) to other haematocrits. Since the measurement of the scattering properties of blood has been proven to be challenging, we apply an alternative, theoretical approach to calculate spectra for μ(s) and g. Hereto, we combine Kramers–Kronig analysis with analytical scattering theory, extended with Percus–Yevick structure factors that take into account the effect of dependent scattering in whole blood. We argue that our calculated spectra may provide a better estimation for μ(s) and g (and hence μ(s)′ and μ(eff)) than the compiled spectra from literature for wavelengths between 300 and 600 nm.