REVIEW article
Front. Photonics
Sec. Biophotonics
Volume 6 - 2025 | doi: 10.3389/fphot.2025.1636398
Optical Absorption and Scattering Properties of Blood and Its Components: a Review
Provisionally accepted
- 1Toronto Metropolitan University, Toronto, Canada
- 2Oregon Tech, Wilsonville, United States
- 3iBEST, St. Micheal's Hospital, Toronto, United States
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Blood is a complex biofluid with distinct optical characteristics that underpin a range of diagnostic and monitoring technologies. This review examines the absorption, scattering, and refractive index properties of whole blood and its components across the visible and near-infrared spectrum. Blood's optical properties are determined primarily by water, hemoglobin, and its encapsulation in red blood cells. Hemoglobins dominate blood's light absorption in the 400-1100 nm range, with sharp spectral differences between oxygenated and deoxygenated forms. Scattering in whole blood is primarily due to red blood cells and is influenced by hematocrit, oxygenation, shear rate, and osmolarity. Reduced scattering coefficients are close to 13 cm⁻¹ in the whole visible range of the spectrum, and the anisotropy factor is close to unity, indicating highly forward-directed scattering. While other blood cells (white blood cells and platelets) do not contribute significantly to blood's optical properties, their scattering properties are used in many biomedical applications. We also highlight the role of the geometry of experiment-including detour, sieve, and self-shielding phenomena-in shaping blood's optical response. Multiple clinical technologies, such as pulse oximetry, are based on blood's optical properties. Recently reported discrepancies between consumer and clinical devices highlight the need for more accurate models of blood optics for emerging biomedical and wearable sensing applications.
Keywords: biomedical optics, light-tissue interaction, Refractive index, whole blood, Chromophores
Received: 27 May 2025; Accepted: 09 Jul 2025.
Copyright: © 2025 Saiko, Sadrzadeh-Afsharazar, Burton, Prahl and Douplik. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Alexandre Douplik, Toronto Metropolitan University, Toronto, Canada
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