Proceedings Volume 4162

Controlling Tissue Optical Properties: Applications in Clinical Study

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Proceedings Volume 4162

Controlling Tissue Optical Properties: Applications in Clinical Study

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Volume Details

Date Published: 3 November 2000
Contents: 6 Sessions, 33 Papers, 0 Presentations
Conference: EOS/SPIE European Biomedical Optics Week 2000
Volume Number: 4162

Table of Contents

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Table of Contents

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  • Physical Methods of Controlling and Diagnostics of Optical Properties of Tissue
  • Optical Properties and Spectroscopy of Skin: Monitoring of Temperature, Water, and Chemicals Delivery
  • Fluorescence, Photosensitizers, and Photobiological Effects
  • Optical Properties of Blood and Cells
  • Applications in Ophtalmology
  • Poster Session
Physical Methods of Controlling and Diagnostics of Optical Properties of Tissue
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Immersion effects in tissues
The refractive index matching (immersion) of components if a highly scattering tissue has been studied. The influence on tissue optical transmittance, reflectance, polarization and correlation properties of the scattered light is examined. Experimental data for in vitro, ex vivo and in vivo studies of various solutions, gels and oils action an optical properties of human tissues (human skin, sclera of the human eye, and blood) are presented. The dynamics of tissue optical properties depending on matter diffusion rate within tissue is studied. The possible application of immersion effect for tissue spectroscopy, imaging, and thermotherapy is discussed.
Subsurface photodisruption in scattering biological tissue
Zachary S. Sacks, Greg J. R. Spooner, Ron M. Kurtz M.D., et al.
Approximately five million people worldwide are blind due to complications from glaucoma. Current surgical techniques often fail due to infection and scarring. Both failure routes are associated with damaging surface tissues. Femtosecond lasers allow a method to create a highly precise incision beneath the surface of the tissue without damaging any of the overlying layers. However, subsurface surgery can only be performed where the beam can be focused tightly enough to cause optical breakdown. Under normal conditions, subsurface surgery is not possible since sclera is highly scattering. Using two independent methods, we show completely subsurface surgery in human sclera using a femtosecond laser. The first method is to make the sclera transparent by injecting a dehydrating agent. The second method is to choose a wavelength that is highly focusable in the sclera. Both methods may be applied in other tissues, such as skin. We show highly precise incisions in in vitro tissues. Subsurface femtosecond photodisruption may be useful for in vivo surgical technique to perform a completely subsurface surgery.
Photon statistics of the laserlike emission from polymeric scattering gain media with tissuelike optical properties
Giannis Zacharakis, Nektarios A. Papadogiannis, George Filippidis, et al.
The coherent properties of the temporally and spectrally narrowed emission of laser-induced fluorescence of organic dyes hosted inside artificial scattering matrices (random lasers) were investigated. The excitation source was a frequency doubled 200 femtosecond pulsed laser emitting at 400 nm. Spectral and temporal features were simultaneously recorded using a spectrograph and a streak camera operating on the photon counting mode. Photon number distributions were thus created. The temporal coherence of the laser-like emission above and below the excitation energy threshold has been investigated from the photon number distribution obtained.
Optical Properties and Spectroscopy of Skin: Monitoring of Temperature, Water, and Chemicals Delivery
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Water content and water profiles in skin measured by FTIR and Raman spectroscopy
Gerald W. Lucassen, Peter J. Caspers, Gerwin J. Puppels
We present non-invasive measurements of water content in stratum corneum (SC) by FTIR spectroscopy and water content profiles across the epidermis by Raman microspectroscopy. We apply band fitting to the FTIR spectra to assess changes in SC water content following hydration. While the penetration depth of ATR-FTIR is only a few micrometers, the confocal Raman microspectrometer enables successive collection of Raman spectra at a range of depths below skin surface, with an axial resolution of ca. 5micrometers . Depth resolved water concentration measurements of the epidermis obtained by Raman spectroscopy show clear changes in the water concentration profile as a result of hydration.
Analysis of reflectance spectra for skin oxygenation measurements
The reflectance spectra of the human skin in visible and near- infrared spectral region have been calculated using Monte Carlo technique, and the specular reflection on the surface takes into account. The skin is represented as a complex inhomogeneous multi-layered highly scattering and absorbing medium. The model of the skin takes into account variations of spatial distribution of blood vessels, various level of blood oxygen saturation, volume fraction of water, oxy- and deoxy-hemoglobin and melanin content. Comparison of the results of simulation and experimental results made in vivo are presented. The optical properties of the skin tissues are discussed.
In-vivo measurements and computer modeling of the optical properties of the human skin at temperature and chemical agents action
Yulia M. Proshina, Nina A. Razumikhina, Eugeny P. Savchenko, et al.
Optical and hystological human skin properties will be over viewed. Experimental set up for in vivo controlling of the skin state will be described. The results of in vivo measurements for the normal and variously treated skin will be presented. Chemical agents and thermal treatment is used in our experiment as the source of skin properties changes. The results of Monte Carlo modeling will also be presented and compared with those of the in vivo experiment.
In-vitro and in-vivo study of dye diffusion into the human skin and hair follicles
We present experimental results on in vitro and in vivo investigation of dye diffusion into the human skin and hair follicles. It was shown that dyeing as a method of enhancement of the absorption coefficient of hair follicle tissue components can be used for selective photodestruction of hair follicle and surrounding tissues. Strength and depth of hair follicle dyeing inside the skin were determined for various dyes.
Fluorescence, Photosensitizers, and Photobiological Effects
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Fluorescence in iliac artery wall of rabbit induced by AIPc
Elaine Aparecida Corbani, Katia Calligaris Rodrigues, Raduan Hage, et al.
The aim of this work was to verify the Al-Phthalocyanine (AlPc) absorption in iliac artery wall of a rabbit, through transadventitial fluorescence measurement. Two Norfolk male rabbits, weighing 3.5 kg were used. The iliac artery was dissected and isolated. The artery was then clamped in two points with simple ligatures spaced 1.5 cm. The experiment was made in three phases, with acquisition of several fluorescence spectra in different points of the iliac artery. Firstly was measured the pre and post clamping transadventitial fluorescence without the presence of the photosensitizer. On the second phase, the AlPc, 2.5 (mu) M in 50 (mu) L solution, was injected locally into the clamped region and fluorescence spectra were collected in t=0 minutes and t=15 minutes. Finally, 30 minutes from the beginning of the experiment the clamping was removed, the blood flow restarted into the artery, and the fluorescence spectra was collected in t=5 minutes and t=10 minutes. The excitation was made using an Argon Laser (Stabilite 2017-Spectra Physics), operating in 488nm with 7mW optical power measured at the distal fiber tip. A unique peak, centered in 682nm, identifies the AlPc presence on the analyzed tissue.
Quantitative estimation of absorbing chromophores in tissue simulators based on laser-induced spectroscopy and scattering measurements
Mersini I. Makropoulou, Helen Drakaki, Georgios Stamatakos, et al.
The determination of the tissue optical parameters and the light propagation in multicomponent tissues is an important tool for real-time laser treatment dosimetry (selective laser ablation, PDT) and non-invasive laser diagnostics (laser induced fluorescence spectroscopy, optical tomography). The aim of this work is the experimental study of the optical characteristics of laser light propagation in tissue simulators, employing spectroscopic techniques, in order to quantify the concentration of tissue chromophores. Total and diffuse reflectance/transmittance measurements of tissue phantoms were performed at visible wavelengths and the calculated optical properties were correlated to the concentration of the absorbing species in a multicomponent environment. The experimental results demonstrated the ability of the laser induced spectroscopic techniques for quantitative estimation of tissue chromophores concentration.
Sonoluminescence imaging in vivo
Da Xing, Yonghong He, Yonghong Tang, et al.
In this paper, a sonoluminescence (SL) image of living bodies were obtained with a high-sensitive imaging system for the first time. We found that some kind of chemiluminescent analytic agent, such as FCLA (Fluoresceinyl Cypridina Luminescent Analog) which can work in vivo, could enhance the SL by chemiluminescence through a chemical reaction with oxygen free radicals. In the experiment FCLA is used to enhance the biological SL of mouse body and a clear image of FCLA-enhanced SL was observed in vivo. The biological SL of several typical biological tissues are also investigated. The SL intensity from different tissues has significant difference. With confocal scanning technique, this SL imaging method has potential applications in clinical diagnosis.
Novel cancer diagnostic method: FCLA-assisted sonodynamic diagnosis
In this paper, we propose, for the first time, the concept of Sono-Dynamic Diagnosis (SDD). The novel method named FCLA Assisted Sono-Dynamic Diagnosis is designed as follows: HpD is used to localize the cancer tissue, and is sonosensitized by the ultrasound field to produce singlet oxygen. Then, another reagent, FCLA (Fluoresceinyl Cypridina Luminescent Analog), reacts with O2 to efficiently transform the chemical energy of O2 to photons, thus a strong chemiluminescence is emitted. One can then detect this emission with a high sensitive CCD imaging system to localize the tumor. Based on the principle of FCLA assisted SDD, we obtained a clear diagnostic image of a transplanted tumor in a nude mouse in the experiments. It is shown that the emission from the tumor region is much stronger than that from other regions. The outline of the tumor is quite clear. This method could have potential applications in clinics for early-stage tumor diagnosis.
Photoacoustic trace gas detection of ethene released by UV-induced lipid peroxidation in humans
Simona M. Cristescu, Rik Berkelmans, Sacco te Lintel Hekkert, et al.
A sensitive CO2 laser-based photoacoustic (PA) detector has been used to perform non-invasive and on-line measurements of ethene (C2H4) production from exhaled air and directly emitted from the skin. Ethene was used as indicator for free- radicals induced lipid peroxidation in the skin of human subjects exposed to ultraviolet (UV) radiation from a solarium. Ethene from the exhaled air was analyzed for a group of 21 male subjects at rest. During 15 minutes of UV exposure, the average ethene emission was 17.2 pmol/kg/min (SD 7.3), while the pre-UV exposure levels were 1.4 pmol/kg/min (SD 0.38). Different types of sun protection creams were tested by means of ethene release in exhaled air. The influence of UV radiation intensity and of exposure time (10 and 15 minutes, respectively) on the ethene emission from the skin has been studied for a second group of 12 subjects. Comparison between measurements of exhaled air and directly on the skin is presented.
Kinetics of the accumulation of aluminum(III)-sulfophthalocyanine by human leukocytes measured with a scanning flow cytometer
I. G. Scribunov, Pit A. Tarasov, K. A. Semianov, et al.
The kinetics of aluminum (III)-sulfophthalocyanine uptake by human leukocytes was measured with a scanning flow cytometer (SFC) during the initial period of accumulation, 40 min. The individual cells were distinguished by SFC from their light scattering traces. The dye fluorescence in the cells was excited by N2 pulse laser, and the kinetics of the cell distribution on the amount of the accumulated dye was obtained. A mathematical model of endocytosis was applied in order to describe the dynamics of cell distribution in the system during the cellular uptake. The main kinetic parameters of the dye accumulation were evaluated.
Optical Properties of Blood and Cells
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RBC aggregation effects on light scattering from blood
We consider a number of diffusive and transport models of light transmission through whole blood, targeting better understanding of nature of optical transmission pulsations for blood flow modulated by heartbeats. We claim the existence of scattering- associated mechanism rather than the absorption-associated one. Single erythrocytes and their aggregates are considered to be the main centers of scattering in the red- near infrared spectral region. The shape and size of aggregates change in time due to blood flow changes. The corresponding changes of optical transmission are simulated.
RBC-aggregation-assisted light transmission through blood and occlusion oximetry
Optical transmission of tissue in-vivo and model red blood cells (RBS) suspensions in vitro have been measured in red and near infrared region targeting better understanding of the nature of in vivo pulsatile signals. It is shown experimentally (both in vitro and in vivo) that the pulsatile signal may result not just from volumetric changes, but also from light scattering fluctuations. Theoretical predictions on time evolution of optical transmission for the case of very long over-systolic occlusion also have been proved experimentally for both in vivo measurements and in vitro model sets. The interconnection of the shape of optical signal and geometry of RBC aggregates is confirmed.
Fractal behavior and optical properties on erythrocytes viscoelasticity subjected to mechanical stress
Ana Maria Korol, Juana R. Valverde, Rodolfo Jose Rasia
In this study techniques of fractal analysis as well as a home made device are proposed to characterize viscoelastic properties on mammalian erythrocyte membranes. A numerical method formulated on the basis of the fractal approximation for ordinary (OBM) and fractionary Brownian motion (FBM), is proposed to evaluate sensitive dependence on initial conditions. We hypothesize that this photometric temporal series, could be modeled as a system of bounded correlated random walk. Hence, three phase spaces n-dimensional (n=2 to 8) are generated, and used to distinguish chaotic from white noise behavior. The time series was obtained by ektacytometry over several millions of shear elongated cells. These experimental determinations were carried out in a home made device called erythrodeformeter, that has been built for rheological measurements on red blood cells subjected to definite fluid shear stress. A laser beam traverses the layer of shear deformed erythrocytes producing an elliptical pattern and diffracted intensity corresponding to each principal diameter of the diffraction pattern falls onto a photomultiplier tube (PMT), after passing through a thin straight slot in a mask placed exactly on the corresponding axis of the elliptical pattern. These photometric reading performed while erythrocytes became deformed and relaxed are used to calculate three different parameters over the time dependent process, and very different results were obtained.
Determination of spherical biological particles parameters from light-scattering indicatrix visibility
Nickolay V. Shepelevich, Inna V. Prostakova, Valeriy N. Lopatin
The relations between intensities of light scattering in positions of indicatrix extrema (visibility) and relative refractive index of a homogeneous sphere are studied analytically and numerically for optically soft particles. The Wentzel- Kramers-Brillouin approximation has been used for solution of inverse problem. The obtained results reveal the opportunity of determination of relative refractive index for individual spherical particles from experimental indicatrix.
Applications in Ophtalmology
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Depth-sensitive adaptive deconvolution of retinal images
Andrey V. Larichev, Nikita G. Irochnikov, Ilia P. Nikolaev, et al.
The capability of resolving fine details on retinal images plays a key role in early diagnostic of vision loss. Biochemical and morphological features, which may be present in the early stages of many retinal diseases, cannot be detected today with current funduscopic instruments because of the losses in spatial resolution introduced by the ocular medium and cornea. One of the ways of the solution of such a problem is to use the adaptive optical systems first for measuring phase distortions and then for its suppression. In our work we suggest the innovative approach that includes two stages of adaptive correction. On the first stage a Shack-Hartman wavefront sensor and modal flexible mirror is used for low-order aberration correction. On the second stage a computer post-processing, or deconvolution, of the residual aberrations is done using the information on the aberrations measured by the sensor. In our report we present the specific design of the Shack-Hartman wavefront sensor suitable for measurements of human eye aberrations. The characteristics of a modal bimorph corrector are discussed. The features of deconvolution technique are outlined.
Laser light scattering in eye lens model
Nadezhda L. Larionova, Irina L. Maksimova, Vyacheslav I. Kochubey
Theoretical investigations of laser light radiation scattered by eye lens model as a system of spheres with various parameters were performed on the base of Mie theory of electromagnetic scattering by a single sphere. The calculations were performed for systems of particles whose coordinates were specifically realized in random fashion according to the specified probabilities defined by the approximation of hard spheres. The modeling of lens biotissue was carried out by using of medical data about internal structure of lens of human and some animals. In general the researchable model presents the system of homogeneous spherical particles those are randomly distributed in the layer of thickness. We study the optical properties such as scattering effective cross-section and function of correlation in different models.
Poster Session
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Theoretical estimations of the area of destruction in brain tumors under photodynamic therapy
Vadym N. Bidnenko, Valeriy L. Sigal, Vladimir D. Rozumenko
It's proposed reaction-diffusion mathematical model for evaluating efficiency and destruction area of brains' rumor under photodynamic-laser therapy. The modeling is based on physical mechanism of tissue's effect by singlet oxygen, which display oxidizer's function. Kinetic description of process is proceeded from model of M.J.C. van Gemert, that was worked out diffusion's mechanism of triplet oxygen's spreading in tissue under photodynamic therapy. All calculations are carried out for red laser with wavelength 630nm and photofrin2, as photosensitizer, and for the second type of photo-physical reactions of such molecules. The space-time tissue dependencies of concentrations of possibility conditions of oxygen and photosensitizers are calculated. As was theoretical shown, effect of photodynamic destruction of tumor by singlet oxygen, particularly in brain, not depends from intensity of laser's irradiation, but is dictated by summation does, which is absorbed by tissue in all time of process. The hyperhypoxic's effects in tumor, that accompany of photodynamic therapy, strongly increases with decreases of light's attenuation coefficient in tissue medium.
In-vitro study of control of human dura mater optical properties by acting of osmotical liquids
We present experimental results and computer modeling of investigation on the optical properties of the human dura mater controlled by administration of osmotically active chemical, such as mannitol and glucose solutions with various concentrations. Administration of chemical agent induces diffusion of matter and as a result equalization of the refractive indices of collagen and ground material. Results of experimental study of influence of osmotical liquids (mannitol and glucose solutions) on reflectance and transmittance spectra of the human dura mater are presented. The significant decreasing of the reflectance and increasing of the transmittance of the human dura mater samples under action of osmotical solutions were demonstrated.
Problems of theoretical calculation of the laser light distribution in biological tissues
The possibility of laser spectroscopy for diagnosing pathology in human tissues is studied now very intensively. But there is no total and good theoretical model for calculation of light intensity into the scattering biological tissues. TO obtain one the modified Transport equations, modified Kubelka-Munk approach and some approaches from diffraction theory were developed, studied and used. It was shown that the main problems of development of the exact and total theoretical model exists in the area of combination and accommodation of this three approaches to each other. This new theoretical model is studied and used now as the key point of the software of the real laser clinical diagnostic system.
Mathematical modeling of changes in the optical properties of epidermis due to UV-induced melanogenesis
Mikhail M. Stolnitz, Anna Yu. Peshkova, Alexey N. Bashkatov, et al.
In the work the mathematical model of melanogenesis is presented that allows to predict a qualitative change of epidermis absorption and scattering under UV-irradiation. Epidermal sublayers and inhomogeneous melanin distribution are taken into account.
Interferometric investigations of the cosmonaut erythrocytes
Julia K. Novoderzhkina, Elena A. Streletskaya, Gennady I. Kozinets
Many biological objects, include blood cells, are optically transparent. They don't absorb light and only change optical path length by variations of object's thickness or its refractive index variations. The phase shifting interferometry is used for the visualization of the phase information and the obtaining quantitative properties of cells. Cells are fixed by glutaraldehyde and mounted in immersion liquid for reduction the influences of refraction. Blood cell's interferogram contains the information about space distribution refractive index. The phase-shift method was used for its reconstruction. This method includes record of four interferograms used different values of phase-shift of the reference wave. Many blood cells interferograms are obtained (lymphocytes and erythrocytes). The shape, size and density of cells are measurement. We suppose that these date will be ones of the early diagnostically criteria of hematological diseases. Experimental results for interferometric microscopy and tomography of blood cells are presented.
Optical investigation of functional structures in isolated perfused pig heart
Robert Rauh M.D., Markus Boehnert, Christine Mahlke, et al.
Light scattering in tissue of mammals and humans is affected by subcellular structures. Since these structures correlate well with the status of cells and tissue, light scattering seems to be ideal for monitoring of functional tissue state. By use of EMPHO SSK Oxyscan we investigated functional parameters in a novel kind of isolated perfused pig heart model. In this perfusion model we use organs obtained by the local slaughterhouse that are reanimated at our institute by application of a heart-lung machine. By creating 3D-images of tissue scattering we found an interesting relation between anatomical structures of myocardium and the 3D-images. Additionally, we detected coherence between backscattered light intensity and functional tissue status. Furthermore, we got a sight into the redox state of cytochrome aa3, b and c by creating difference spectra. We believe that this new kind of tissue imaging method will give us the opportunity to get new insights into myocardial function.
Monte Carlo simulation of light propagation in a multilayered biological tissue with optical clearing
In this paper, we described our results of Monte-Carlo simulation of light propagation in a multi-layered biological tissue, such as the human brain and the skin with optical clearing. This report includes optical clearing simulations with different variants of clearing tissue structure. As well as we described light beam deformation in a multi-layered tissue and general principles of our algorithms construction.
Optical properties of melanin in the skin and skinlike phantoms
Experimental study and computer modeling were used to investigate the optical properties of melanin in the skin and skin-like phantoms. To investigate light scattering by melanosomes in skin we made skin-like phantoms on the base of gelatin with different content of melanin particles. Spectra of total transmittance and diffuse reflectance of the phantoms were obtained in the wavelength range from 400 to 800 nm. Absorption and reduced scattering coefficients of melanin were calculated. Mie theory was used to estimate the optical properties of melanin particles. Wavelength dependence of refractive indices of eumelanin particles (isolated and purified from the ink of the cuttlefish Sepia officinalis) and synthetic melanin particles was estimated.
Dynamics of optical clearing of human skin in vivo
Svetlana P. Chernova, Natal'ya V. Kuznetsova, Alexander B. Pravdin, et al.
Two ways of improving the skin permeability to clearing agents has been suggested and tested: i. Removal of upper layers of epidermis by glue stripping, ii. Electrophoretic administration of clearing agent into intact skin. Alterations in light scattering by skin under continuous contact with the agent were monitored by the measurement of diffuse reflectance of tissue at 830nm.
Express diagnostic of anaerobic infection and disbacteriosis by optical PNC method in clinical dentistry
Michail Timofeevich Alexandrov, Sergey U. Koz'ma, Ilia M. Taubinsky, et al.
In this research a new way of express (real time) diagnostics of anaerobic infection and disbacteriosis is suggested. The express diagnostics of anaerobic infection allows to perform quick assessment of the injury microbiocenosis, the state of gastroenteric tract, the disbacteriosis presence and the degree of its development, to follow up dynamics of microflora variations in the process of medication treatment. The research were performed with optical PNC-method. The basic of the method is in registration of stimulated (secondary) radiations and registration of their space fields, which occur in the process of probing radiation interaction with biological tissues and their active elements. The process is called Photon- undulatory Nonlinear Conversion or in short PNC-process (PNC- method, PNC-diagnostic). The optimal diagnostic PNC-method developed here allows detecting the presence of anaerobic microflora directly at the bed of a patient. It makes possible to control the dynamic of patient rehabilitation process, providing strictly individual assessments.
Detection of early stages of dental caries by optical PNC diagnostics: comparison with visual inspection, dental probe, and x-ray methods
Victor I. Masychev, Alexander A. Sokolovsky, Gaby Kesler
In this research results of approbation of the optical PNC-method in dental clinic are presented. The PNC-method was used for diagnostics stages of caries (initial, moderate and deep). The variant of the PNC-method adapted for dental diagnosis is based on simultaneous analyses the following parameters by special algorithms: probing radiation, stimulated backscattering and autofluorescence of caries induced batteries. Analyze of informational signals show good correlation with tooth morphological structure and concentration of anaerobic microflora in hearth of caries lesion. Investigation was performed in vivo on 101 tooth in conditions of typical dental clinic. Comparison of the PNC-methods with visual inspection, dental probe and X-ray ones, which are widely used in clinical practice was made. Preliminary results showed high potential of usage of the PNC-method in clinical practice and more high probability of initial caries detection (up to 100%) in comparison with X-ray method (approximately 75%). In cases when X-ray diagnosed absence of initial caries, more sensitive the PNC-method detected initial caries in stage white lesion.
Real-time caries diagnostics by optical PNC method
Victor I. Masychev, Michail Timofeevich Alexandrov
The results of hard tooth tissues research by the optical PNC- method in experimental and clinical conditions are presented. In the experiment under 90 test-sample of tooth slices with thickness about 1mm (enamel, dentine and cement) were researched. The results of the experiment were processed by the method of correlation analyze. Clinical researches were executed on teeth of 210 patients. The regions of tooth tissue diseases with initial, moderate and deep caries were investigated. Spectral characteristics of intact and pathologically changed tooth tissues are presented and their peculiar features are discussed. The results the optical PNC-method application while processing tooth carious cavities are presented in order to estimate efficiency of the mechanical and antiseptic processing of teeth. It is revealed that the PNC-method can be sued as for differential diagnostics of a degree dental carious stage, as for estimating of carefulness of tooth cavity processing before filling.
Optical caries diagnostics: comparison of laser spectroscopic PNC method with method of laser integral fluorescence
Victor I. Masychev
In this research we present the results of approbation of two methods of optical caries diagnostics: PNC-spectral diagnostics and caries detection by laser integral fluorescence. The research was conducted in a dental clinic. PNC-method analyses parameters of probing laser radiation and PNC-spectrums of stimulated secondary radiations: backscattering and endogenous fluorescence of caries-involved bacterias. He-Ne-laser ((lambda) =632,8 nm, 1-2mW) was used as a source of probing (stimulated) radiation. For registration of signals, received from intact and pathological teeth PDA-detector was applied. PNC-spectrums were processed by special algorithms, and were displayed on PC monitor. The method of laser integral fluorescence was used for comparison. In this case integral power of fluorescence of human teeth was measured. As a source of probing (stimulated) radiation diode lasers ((lambda) =655 nm, 0.1 mW and 630nm, 1mW) and He-Ne laser were applied. For registration of signals Si-photodetector was used. Integral power was shown in a digital indicator. Advantages and disadvantages of these methods are described in this research. It is disclosed that the method of laser integral power of fluorescence has the following characteristics: simplicity of construction and schema-technical decisions. However the method of PNC-spectral diagnostics are characterized by considerably more sensitivity in diagnostics of initial caries and capability to differentiate pathologies of various stages (for example, calculus/initial caries). Estimation of spectral characteristics of PNC-signals allows eliminating a number of drawbacks, which are character for detection by method of laser integral fluorescence (for instance, detection of fluorescent fillings, plagues, calculus, discolorations generally, amalgam, gold fillings as if it were caries.
Estimation of wavelength dependence of refractive index of collagen fibers of scleral tissue
We present experimental results and computer modeling on the optical properties of the human scleral tissue. The wavelength dependence of the refractive index of collagen fibers in the human scleral tissue was estimated on the base of Mie theory. Dispersion formula describing this dependence was derived. The results are general and can be used to describe optical properties of many other fibrous tissues.