A computer model of blood vessel heating by pulse laser irradiation incident on the upper skin layer (epidermis) is suggested. The model is a multilayered half-infinite structure. The depths, optical (absorption and scattering), mechanical and thermal-optical properties of layers are in agreement with the real properties of epidermis and dermis of skin. The exterior of model object (epidermis) is illuminated by light beam of cylindrical form with homogeneous intensity distribution along the cross section. The blood vessel, situated in dermis, is simulated by infinite circular cylinder. Calculations of the dynamics of temperature field inside blood vessel taking into account an inhomogeneous distribution of volumetric heat release within it under the action of pulse laser irradiation of skin were made.
Spider leg veins represent an important aesthetic problem. This clinical study was performed to investigate the pulsed near-infrared diode laser (810 nm) treatment of spider leg veins. 35 female patients were enrolled in this study and treated twice with laser densities of energy (fluence) between 60 - 100 J/cm2 and a spot size of 50 mm2. Histological examinations were performed to investigate morphological and functional effects. Spectroscopic investigations were used as a non-invasive evaluation tool. After the first laser treatment 15 patients showed a complete disappearance (CR); in the remaining 20 patients a remarkable improvement (RI) was seen (N=35). After six months of follow-up
CR was noted in 6 patients, RI in 6, a stable situation in 9, and scar formation in one patient (N=21). The histological examination before and after laser treatment showed no cellular inflammatory reactions. The mean vascular areas were significantly reduced after the laser treatments. Vis-NIR spectroscopic investigations showed almost an immediate occurrence of the haemoglobin double peak and a prompt decrease of the visible remittance after laser treatment of
the skin. Pulsed diode laser therapy is a safe and effective option for the treatment of spider leg veins. Objective in vivo- monitoring by remission spectroscopy and the histology of biopsy specimens show the immediate and long-term laser effects of the irradiated skin in detail.
An advanced model of blood vessel heating by laser radiation is proposed for tasks of laser skin surgery and therapy. Blood vessel is modeled by infinite circular cylinder situated in skin dermis. Heat conduction equation taking into account the inhomogeneous internal source function is calculated. The source function inside the blood vessel is calculated according to the theory of diffraction of electromagnetic radiation on infinite circular cylinder. Dynamics of the temperature fields inside the vessels as a function of vessel diameters and duration of irradiance is calculated for the wavelength of 0.532 μm. It is determined the irradiance conditions whereby the near-homogeneous heating along the perimeter of walls of blood vessels on minimum laser exposure to surrounding tissues is achieved.
In medical diagnostics, non invasive optical techniques will become common at a variety of applications because they contribute to objectivity and precision. The spectral properties of human tissue are an important field of interest. They offer opportunities of detection of skin diseases and of evaluation of chronic wounds. In the visible range, the hemoglobin absorption corresponds to blood microcirculation and the melanin absorption to the skin-type. Two types of diode-array equipment will be described: a combined VIS-NIR spectrometer system from J&M Aalen/Germany (400 nm to 1600 nm) and a stand-alone spectrometer from COLOUR CONTROL Farbmesstechnik Chemnitz/Germany (400 nm to 1000 nm). Non-contacting sensing is essential for investigating chronic wounds (no disturbances of blood microcirculation by contact pressure). The spectroscopic VIS-NIR readings of chronic wounds mainly depend on the absorption of hemoglobin and water. Multivariate analysis was applied for an objective spectral classification of eight different wound scores. Some results regarding spectral measurements of wounds and skin will be discussed. The spectrometer of COLOUR CONTROL was tested in dental surgery. To select dentures, its color has to be determined exactly to meet beauty culture demands. Color determination by dentist is not sufficient enough because of possible metameric effects of illumination. Results of spectral evaluation of denture material and human teeth will be given. Medical examination requires portable and ease equipment suitable for precise measurements. This is solved by a modular measurement system comprising microcomputer, display, light source, fiber probe, and diode-array spectrometer. It is efficient to process primary spectral data to appropriate medical interpretations.
Spectroscopic investigations of the VIS-NIR range allow the objective determination of pigmentation, blood microcirculation and water content of human skin. Non- contacting in vivo measurements of the human skin of 50 volunteers reflect the clinical skin type well. Our correlation analysis yields that the red/infrared spectral range can be used for a determination of skin type. The observed strong spectral variations within the same group of skin type are likely based on the high biological variability of human skin and subjective clinically observed skin type. Therefore it can be useful to measure the full spectral range and to calculate a non-observed skin score with multivariate spectral methods. By multivariate analysis a correct classification of remittance spectra can be obtained. Time- depending spectral variations of dermal microcirculation can be measured at defined locations of the body, for instance the dynamics of oxygenation or blood volume in the skin of the fingertip. The cardial, pulmonal and vasomotoric waves of the micro- and macrocirculation are clearly visible at different wavelengths. The spectroscopic informations are important as an objective measure for the skin type evaluation, the penetration behavior of pharmaca, laser surgery, and therapy.
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