The biomedical effect of laser-induced photodissociation of oxyhemoglobin in vivo

It is demonstrated that the photodissociation of oxyhemoglobin in cutaneous blood vessels and capillaries allows additional extraction of molecular oxygen, prevents hypoxia, and stimulates aerobic metabolism of cells. On the basis of the studied phenomena, a new optical technology of local oxygenation of tissue directly in the zone of laser irradiation has been developed. It is shown that the efficiency of the proposed method for laser-induced oxygenation of biotissues is comparable with the efficiency of hyperbaric oxygenation, with local action being an additional advantage. Various aspects of the applications of the new technology in modern medicine in which the elimination of local hypoxia is needed are discussed. The proposed optical method for local oxygenation of biotissues makes it possible to solve the hypoxia problem in malignant tissue and substantially increase the efficiency of photodynamic, radiation, and chemical therapy in modern oncology.     

Laser-induced photodissociation of carboxyhemoglobin: An optical method for eliminating the toxic effect of carbon monoxide

We propose and examine an optical method for eliminating the toxic effect of carbon monoxide. The developed method is based on laser-induced photodissociation of carboxyhemoglobin in blood vessels and capillaries. By numerical simulation of the interaction of laser radiation with tissue, we calculate the spectra of the action of carboxyhemoglobin and oxyhemoglobin in cutaneous blood vessels. We show that, despite the sufficiently strong overlap of the action spectra of carboxyhemoglobin and oxyhemoglobin, the substantial difference in the quantum yield values makes it possible to develop an optical method for eliminating the toxic effect of carbon monoxide. We determine the criteria for the efficiency of laser-induced photodissociation of carboxyhemoglobin under direct action on lung alveoli through the skin tissue and intravenously.     

Kinetics of oxygenation of skin tissue exposed to low-intensity laser radiation

We present the results of modeling the action spectrum and an experimental investigation of the effect of laser-induced photodissociation of oxyhemoglobin in vivo on the increase in the degree of oxygenation of skin tissue in the exposed area. We have shown that controlling the local concentration of free molecular oxygen in biological tissues together with the possibility of eliminating tissue hypoxia using laser radiation makes it possible to stimulate aerobic cell metabolism and to achieve the needed therapeutic effect. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 120–125, January–February, 2007.     

Effect of temperature on the quantum yield of laser-induced photodissociation of oxyhemoglobin in vivo

We have studied the effect of temperature on laser-induced photodissociation of oxyhemoglobin in vivo by recording the change in the oxygen saturation of arterial blood. We have established that on exposure to low-intensity laser radiation, the local concentration of free oxygen in tissue significantly increases for a body temperature above 40°C, compared with the normal temperature. We demonstrate a unique option for selectively and locally increasing the concentration of free molecular oxygen in tissue, which promotes enhancement of cell metabolism. We consider the possibilities for biomedical use of this phenomenon. The results obtained show that the temperature dependence of the quantum yield for photodissociation of oxyhemoglobin should be considered in development of new therapeutic methods for laser medicine. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 90–93, January–February, 2006.     

Depth distributions of light action spectra for skin chromophores

Light action spectra over wavelengths of 300–1000 nm are calculated for components of the human cutaneous covering: melanin, basal (bloodless) tissue, and blood oxy- and deoxyhemoglobin. The transformation of the spectra with depth in biological tissue results from two factors. The first is the wavelength dependence of the absorption coefficient corresponding to a particular skin chromophore and the second is the spectral selectivity of the radiation flux in biological tissue. This factor is related to the optical properties of all chromophores. A significant change is found to take place in the spectral distribution of absorbed radiant power with increasing depth. The action spectrum of light for the molecular oxygen contained in all components of biological tissue is also studied in the 625–645 nm range. The spectra are found to change with both the volume fraction of blood vessels and the degree of oxygenation of the blood. These results are useful for analyzing processes associated with optical absorption that are possible mechanisms for the interaction of light with biological tissues: photodissociation of oxyhemoglobin and the light-oxygen effect.     

Oxyhemoglobin photodissociation efficiency in biological tissue exposed to laser radiation

We have obtained quantitative data on the differential (with respect to depth) and the integrated oxyhemoglobin photodissociation efficiency in the dermis when the skin surface is exposed to a light beam in the wavelength range 300–650 nm. With this aim, we have used our own previously developed optical model for skin tissue and analytical procedure for calculating the characteristics of optical fields in a medium. We have estimated the number of oxygen molecules formed at different depths in the medium, and also their integrated number over the entire thickness of the dermis as a function of the irradiation wavelength. We consider models for a dermis that is homogeneous with respect to depth and a dermis that has a layered structure. We show that the spectral photodissociation efficiency has a number of maxima associated with the absorption spectrum of oxyhemoglobin and the optical properties of all the layers of skin tissue. We discuss the effect of the epidermis on these maxima.     

Influence of photon energy on the efficiency of photochemotherapy

It is found that when indotricarbocyanine dye in HeLa cells is exposed to photons with different energies the efficiency of cell damage is wavelength independent provided the photosensitizer absorbs the same number of photons per unit time. In vivo animal experiments with two strains of tumor show that when the wavelength of the irradiating light is increased (668, 740, and 780 nm) and the number of photons absorbed per unit time per unit volume of the tumors is held constant, the damage depth increases by a factor of 1.5 and 3, respectively. The observed changes are related both to differences in the in vivo tissue optical transmission with increasing wavelength and an increased local concentration of oxygen owing to photodissociation of oxyhemoglobin.     

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 O₂ in the dermis due to the photodissociation of blood oxyhemoglobin. We show that, for maximal local O₂ 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 O₂ in the intire bulk of the dermis.     

Optical absorption and scattering spectra of pathological stomach tissues

Diffuse reflection spectra of biotissues in vivo and transmission and reflection coefficients for biotissues in vitro are measured over 300–800 nm. These data are used to determine the spectral absorption and scattering indices and the scattering anisotropy factor for stomach mucous membranes under normal and various pathological conditions (chronic atrophic and ulcerous defects, malignant neoplasms). The most importan tphysiological (hemodynamic and oxygenation levels) and structural-morphological (scatterer size and density) parameters are also determined. The results of a morphofunctional study correlate well with the optical properties and are consistent with data from a histomorphological analysis of the corresponding tissues.     

Comparative studies of infrared laser and radio-frequency action on in vitro biotissues by the method of polarization sensitive optical coherence tomography

We make comparative studies of structural changes of in vitro biotissues subject to the infrared (IR) laser radiation and the radio-frequency field. Noninvasive diagnostics and monitoring of microstructural changes of biological tissues are performed using optical coherent tomography.     

In vivo measurement of the local optical properties of tissue by use of differential path-length spectroscopy

We demonstrate the capability of differential path-length spectroscopy (DPS) to determine the local optical properties of tissue in vivo. DPS measurements on bronchial mucosa are analyzed and yield information on the local blood oxygenation, blood content, average microvessel diameter, and wavelength dependence of the reduced scattering coefficient. Our data collected to date show that cancerous bronchial mucosa has a lower capillary oxygenation and a larger average capillary diameter than normal bronchial mucosa.     

Laser optical method of visualizing cutaneous blood vessels and its applications in biometry and photomedicine

We propose and examine a new approach to visualizing a local network of cutaneous blood vessels using laser optical methods for applications in biometry and photomedicine. Various optical schemes of the formation of biometrical information on the architecture of blood vessels of skin tissue are analyzed. We developed an optical model of the interaction of the laser radiation with the biological tissue and a mathematical algorithm of processing of measurement results. We show that, in medicine, the visualization of blood vessels makes it possible to calculate and determine regions of disturbance of blood microcirculation and to control tissue hypoxia, as well as to maintain the local concentration of oxygen at a level necessary for the normal cellular metabolism. We propose noninvasive optical methods for modern photomedicine and biometry for diagnostics and elimination of tissue hypoxia and for personality identification and verification via the pattern of cutaneous blood vessels.     

Doppler velocimetry and backscattering spectroscopy according to a homodyne scheme using a single-mode Er fiber laser

The prospects for the homodyne recording of backscattered radiation of an Er fiber laser in measuring velocity and in Doppler spectroscopy are investigated. The sensitivity and accuracy of measuring velocity are estimated. It is shown that this method can be used to control laser-induced hydrodynamic flows that form upon the laser evaporation of biotissues.     

Two‐Color Laser Photodynamic Therapy of Tumors

A method of photodynamic therapy of tumors (neoplasms) based on simultaneous action of radiation from two lasers with different generation wavelengths is proposed and implemented in an experiment on animals. The antineoplastic effect was evaluated by the dimensions of the necrosis region determined using the method of vital staining of tissues. The effect of photodynamic therapy in the case of simultaneous use of the two lasers (₁ = 627.8 nm and ₂ = 671 nm) turned out to be higher than in the case of their separate application. The hypothetical reason for the phenomenon is oxyhemoglobin photodissociation that leads to the enrichment of blood with free oxygen.     

An analysis of thermal effects resulting from laser radiation interaction with a multilayered biotissue

Initial data for solving the problem of heating biological tissues by laser radiation are the optical characteristics of the tissues determining light regimes after irradiation, and their thermal-physical properties determining heat transfer as functions of time and depth of penetration into the medium. Based on an analysis and generalization of literature data and results of our investigations, we suggest a model of the optical and thermal-physical characteristics of the biotissues. The finite-element method is used to solve the problem of thermal conductivity. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 90–94, October, 2006.     

Spectrum of the effect of laser radiation on hemoglobin of the blood vessels of skin

We suggested and consider the primary mechanism of biostimulation and of the therapeutic effect of low-level laser radiation caused by a local increase in the effectiveness of oxygen transfer by oxyhemoglobin of the blood vessels of skin. The spectra of the effect of laser radiation on oxyhemoglobin and hemoglobin of the blood vessels of skin are presented which were obtained using a method of numerical simulation with allowance for the optical characteristics of skin and for the depth of penetration into it of radiation of different wavelengths. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 877–860, November–December, 1998.     

Compression as a method for increasing the informativity of optical coherence tomography of biotissues

The efficiency of the mechanical compression of biotissues for improving the differentiation between pathological changes in the structure of a biotissue observed by the method of optical coherence tomography (OCT) is investigated. The effect of the compression in the OCT-images of samples of the human rectum affected by inflammation and carcinoma is studied ex vivo. It is shown that the use of compression makes it possible to differentiate between these pathological changes. To interpret experimental data, images of an inflamed part of rectum are modeled by the Monte Carlo method for different degrees of compression. The results of modeling agree qualitatively with the experimental data.     

在1341.4 nm激光波长对生物组织折射率的测量

根据全反射原理,设计一个由准直宽光束和双棱镜构成的测量装置用于测量生物组织的折射率.在波长632.8 nm通过对几个样品测量,证明该方法用于测量生物组织的折射率具有可靠、精确和简单易行的特点.第一次测得了某些生物组织在1341.4 nm 的折射率,也为在1341.4 nm激光波长测量人体组织的折射率提供了一种有效的方法.     

Possibility of the optical separation of the isomeric nuclei by laser radiation

The possibility of using laser radiation for fast optical separation of isomeric nuclei is considered. The proposed method of separation is based on selective two-step photoionization of atoms or photodissociation of molecules.