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

Abstract

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 (μa), scattering coefficient (μs) and scattering anisotropy (g). From this, we calculate the reduced scattering coefficient (μs′) and the effective attenuation coefficient (μeff). In the compilation of μa and μs, 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 μs, we present a novel, theoretically derived formula that can be used for practical rescaling of μs 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 μs 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 μs and g (and hence μs′ and μeff) than the compiled spectra from literature for wavelengths between 300 and 600 nm.

Quantitative blood oxygen saturation imaging using combined photoacoustics and acousto-optics

“…In this case, the PA image values from both tubes are equal and directly relate to the optical absorption of the target. Further, the ratio of 1.40 of the fluence compensated PA signals from both tubes at λ 755 nm to λ 780 nm is in agreement with the known absorption spectrum of the 5% oxygenated blood [15].…”

Resultados de médio e longo prazo do tratamento endovenoso de varizes com laser de diodo em 1940 nm: análise crítica e considerações técnicas

“…Additionally, the values for effective optical penetration in water for 1470nm and 1940nm, based both on absorption and scattering processes, are approximately 220 µ and 48 µ respectively, in contrast with a value of approximately 3.0 mm for 980nm. 24,26,27 Based on these facts, endovenous laser ablation at 1470nm, conducted by homogeneous tissue irradiation (with a radial fiber) with the vein wall as the direct target (chromophore: interstitial water) was indeed a major breakthrough for endolaser techniques, with impacts on minimization of the adverse effects inherent to the technique performed with other types of lasers (808, 810, 940 and 980nm, for example). [9][10][11]20,28 In turn, conducting the technique with a radial fiber and λ = 1940nm is an incremental development of the state-of-the-art in laser thermal ablation.…”

“…10,11,20,29,30 One interesting feature that should be borne in mind in relation to the laser with a λ of 1940nm, compared with the laser at a λ of 1470nm, is that its light is absorbed almost five times more by water and it has an effective depth of optical penetration that is around one quarter of the penetration of the 1470nm laser. 24,26,27 This is because the greater the absorption of the photons from a laser by a given target containing absorbent chromophores, the greater the quantity of heat generated and the more restricted the zone of heat generation, i.e., it is absorption of the photons from the laser by chromophores in the tissue that causes the tissues to heat up (absorptive heating). Absorptive heat (J/cm 3 ), generated in situ, is …”

“…33 Since the coefficient of molar extinction is similar for water and blood, when a laser with a wavelength of 1470nm or 1940nm is used, it is important to empty the vein of intraluminal blood, 33 because otherwise the majority of the energy will be absorbed by the intraluminal blood, leading to thrombotic occlusion and possible recanalization after a few months. 27,33,37,38 This statement is based on a study by Vuylsteke et al, 33,40 that assessed the role played by blood in the results of endovenous treatment with a 1500nm laser, histologically evaluating the degree of destruction of the vein wall. The study concluded that the volume of intraluminal blood results in a reduction of vein wall destruction.…”

Hematocrit dependence of flow signal in optical coherence tomography angiography

“…The decorrelation value can be further expressed as ( ) The scattering property of a particle is also related to the particle concentration. Twersky's formula is usually used describe the relationship between the RBC scattering coefficient and the HCT for human blood [30,31] ( ) From Eqs. (8)- (11), the relationships between these optical parameters and the HCT at a wavelength of 840 nm (the central wavelength of the OCT system) are plotted in Fig.…”