Modeling of optimal conditions for oxyhemoglobin photodissociation in laser-irradiated biotissue

Based on the theory of radiation transfer and a model that describes the structure and optical properties of biotissues, we have found spectral conditions of irradiation of the skin surface that ensure efficient generation of molecular oxygen O 2 in the dermis due to the photodissociation of blood oxyhemoglobin. We show that, for maximal local O 2 formation at depths z ≤ 0.2 mm, 0.2 mm < z ≤ 0.9 mm, 0.9 mm < z ≤ 2.5 mm, and z > 2.5 mm, it is more effective to use wavelengths in the intervals 418 ± 5, 575 ± 5, 585 ± 5, and 600 ± 5 nm, respectively. Physical reasons for the shift of optimal wavelengths toward the red range of the spectrum are described. We show that they are based on the selectivity of optical properties of the skin biotissue, which acts as of a kind of spectral filter the transmission curve of which depends on the depth. It is found that irradiation at a wavelength near 575 nm is optimal for the generation of a maximal amount of O 2 in the intire bulk of the dermis.