Preliminary results are presented on the spatial resolution of time resolved breast transillumination. We have established that the resolution of an image could be described by the Image Quality Index or IQI, defined as the smallest diameter of a detectable object on the image. This theory is based on the statistical decision theory which suggests that the detectability of an object on an image is related to the signal to noise ratio SNR. We present the results of time of flight measurements performed in realistic conditions, i.e., through 20 mm thick samples of breast tissue. Thus a comparison of the theoretical predictions with in vitro data have been made and show that the former simulation predictions were in quite good agreement with measurements.

A preliminary study into the spatial resolution that may be achieved for time resolved near infrared imaging through highly scattering media has been performed. The spatial resolution, for time gated images, has been investigated quantitatively by measuring the edge-spread function for scattering media of different properties and at different depths. Transmission scans of two absorbing rods, spaced by different distances, were used to qualitatively study the contrast obtained at different integration periods or using the measured mean time-of-flight. Both spatial resolution and contrast are improved as the time gating interval is reduced. However, for thick tissue sections it may not be possible to reduce the spatial resolution below about 10 mm, because of the small amount of light arriving at these early times.

Monte Carlo simulation technique is used to study photon migration in biological tissues. On a 36 mm diameter cylinder, temporal point spread function is simulated for each of the seven detectors around the model. Information such as mean-time-of-flight, differential pathlength factor, and detected photon number are recorded. Two back-projection algorithms have been proposed to reconstruct tomographic images of phantom.

The suitability and limits of time-resolved transillumination to determine inner details of biological tissues are investigated by phantom experiments. The achievable improvement is demonstrated by using different phantoms (absorbing objects embedded in a turbid medium). By means of line-scans across a sharp edge the spatial resolution and its dependence on temporal resolution can be determined. To demonstrate the physical resolution according to the Rayleigh-criterion, measurements were performed on blackened bead pairs. Investigations with partially transparent beads demonstrate the high sensitivity of time-resolving techniques with respect to variations in scattering or absorption coefficients.

Particle orientation in a disperse medium results both in anisotropic properties and in the changes in spectral transmittancy. To determine theoretically the effects of such kind a general approach based on the joint use of both the equation of Brownian rotation diffusion and the Mueller matrix for a thin slab of anisotropic medium has been developed. The optical properties of scatterers are described in terms of the first and second Born approximation and the exact T-matrix method. The goal of the investigations is to develop adequate optical models for interpretation of the experimental data obtained for the ordered disperse systems. In this paper, anisotropic properties of oriented disperse systems are discussed in a review manner, while the orientational turbidimetric effect is considered in detail.

We have succeeded in working out a new way of making highly sensitive one-line absorption measurements. This technique is similar to the already known method where two intensity modulated lasers with different wavelengths are used. But some special processing of the informative signal makes it possible to distinguish the absorption from scattering and so to carry out the measurements with high accuracy. Full description of the designed technique and some experimental data obtained with the help of it are also given in this paper.

The paper investigates the imaging response of cw coherent systems for imaging through scattering media. Particular attention is paid to the confocal optical technique, and experimental results are presented that show the effect on the imaging spatial resolution as the optical configuration is altered. It is seen that if the scattering concentration is increased, there is a sudden reduction in spatial resolution. This point defines a so called transition region. We show how this transition region can be moved by altering the optical configuration. We also see that when heavily scattering media is being examined, it is possible to vary the optical configuration, what is in effect changing the optical response to various scattered components of light. This procedure can be likened to adjusting the time window in the pulsed time of flight technique, and is further investigated in the companion paper.

The paper presents a method to make direct experimental comparisons between the imaging response of time of flight (TOF) pulsed and continuous wave transillumination techniques. The method uses an absorber to control the different components of scattered light, and uses a Laplace transform relationship to construct the effective TOF response window for the continuous wave system. This TOF response window is the same as that measured in a standard pulsed TOF experiment, thereby enabling comparisons to be made between the imaging response of pulsed and continuous methods of transillumination.

Laser Doppler (LD) microscopy is a technique providing local measurements of directed flow velocities and diffusion coefficients of cells, intracellular protoplasmic constituents, macromolecular aggregates, etc. In our group a computer- and video-aided sign-sensitive scanning laser Doppler microscope (LDM) has been designed, constructed and applied to the study of different biological objects. In this paper some new results are presented in connection with the development of LD microscopy.

The point spread function of transillumination processes is deduced from diffusion theory using common perturbation techniques. It is shown that an unusual term proportional to the gradient of the absorption or scattering coefficient of the object usually may be neglected. For large scattering and small absorption coefficients diffusion theory and Monte Carlo simulation lead to the same resolution. Monte Carlo calculations predict a value of the modulation transfer function for spatial frequency 0, that is large than 1. This effect is experimentally confirmed. The resolution has a minimum at a certain value of the scattering coefficient and increases slowly beyond it. The resolution is improved, the contrast for large objects impaired by an increase of the absorption coefficient.

One of the important methods for the biomedical objects structure investigations is the statistical analysis of the partially developed speckle patterns formed in the output plane of the coherent scanning microscope (CSM). By means of CSM the speckle intensity's statistical properties for the samples of the human epidermis strippings have been investigated. The strippings under testing were considered as random phase screens with an unknown correlation length and phase deviation; for such objects the computer simulation of the laser light diffraction has been carried out.

For the study of light distribution in living tissue, a multi-layer simulation model of the skin was developed. This model assumes realistic anatomical topography data and includes different material parameters of the individual layers such as relative blood volume, absorption coefficient, scattering coefficient, and anisotropy scattering factors. The photon tracks were calculated with the Monte-Carlo-method. Preliminary results show the detectability of alien structures directly beneath the skin surface and in depths of up to several mm.

A Monte Carlo method is used to model the propagation of near infrared light in human breast tissue. The corresponding scattering coefficient, g-factor, and absorption coefficient of the model are adjusted to fit the temporal point spread function. With this model the dependence of the spatial resolution as a function of absorption, thickness of tissue, and integration time of time resolved measurements has been studied. We find that light absorption within the object already acts as a natural filter to suppress long pathlengths of strongly scattered photons. Compared to the case of no absorption, we observe a considerable improvement of the spatial resolution for realistic values of the absorption length and of the tissue thickness. We conclude that by time of flight methods, the spatial resolution in breast tissue with thickness of about 3 - 4 cm may be improved by at most a factor of two, once absorption is taken into account properly.

This paper presents the version of a Monte Carlo method for simulating of optical radiation propagation in biotissue and highly scattering media allowing for 3-D geometry of a medium and macroinhomogeneities located in one of the layers. The simulation is based on the use of Green's function of medium response to a single external pulse. The process of radiation propagation is studied in the area with given boundary conditions, taking into account the processes of reflection and refraction at the boundaries of layers in side the medium under study.

The computer simulation of light propagation in homogeneous and heterogeneous biotissues accounting for absorption and scattering radiation energy by pigmented granules and diffraction is made.

In this paper, phase and intensity information is predicted for a system consisting of two absorbers immersed in a highly scattering medium and two light sources (in- and anti-phased) with a single detector. Phase and intensity information in this 3-D system with absorbing boundaries is obtained by solving the photon diffusion equation by B-W-K technique, with proper boundary conditions. The capability of phased array to resolve two absorbers with a single detector is correlated with a geometric relationship among sources, a detector, and absorbers.

The results of goniometric measurements of the intensity of laser light scattered by bone samples are presented. The experiment was performed on macerated, full-thickness skull samples. The angular dependencies of the intensity of laser light scattered by the samples was measured. The transmission of light through the samples was calculated and is shown as a function of sample thickness for various wavelengths of the incident radiation. The contribution of the fluorescent light in the scattered radiation is taken into account.

Determination of the optical parameters of tissues is a necessary element of laser medical diagnostics and therapy planning. In this work a mathematical model of the photon migration in tissues is considered in the assumption of the harmonic modulation of the incident laser light. The scattering coefficient and the photon's life time in virtually absorbed state can be calculated from the modulation coefficient and phase shift between incident and scattered light. Frequency-domain measurements were performed using two laser diodes (wavelengths 805 and 850 nm) as light-modulated sources and fiber-optic light guides for delivering the light to tissues surface and collecting the back scattering output. It is shown that measured difference in phase shift of scattered light intensity is proportional to difference in mean pathlength of photons at two wavelengths.

We have planned a stereological ultrastructural study of capillaries in the thyroid gland treated with IR laser radiation and quantified 1 day after the last treatment. Wistar rats, 50 days old, were irradiated with IR laser radiation. The rats were perfused with 2.5 percent glutaraldehyde in 0.1 M phosphate buffer (ph equals 7.4). The pieces obtained after sectioning the thyroid gland were placed immediately into the same fixative. A stereological study of the thyroid capillaries was carried out. This analysis revealed an increase of luminal area in irradiated capillaries.

Several approaches to increasing the number of parameters of suspended particles that can be determined by a spectroturbidimetric method have been analyzed. It has been shown that, in principle, this problem can be solved invoking spectral characteristics obtained under conditions of complete or partial particle orientation in the stationary and relaxation regimes. Informative potentialities of combining the methods of electro-optics and spectroturbidimetry have been considered. It has been found that eventually for a given disperse system in situ, it is possible to obtain the following set of parameters: particle mean size, shape characteristic and refractive index, number and mass-volume concentration of particles, their total surface area per unit volume of the suspension and the effective value of particle surface polarizability.

The main principles of flow cytometry and spheres of its application are given. The features and metrological characteristics of the flow counter-analyzer with laser beam space scanning suggested is considered. The experimental results with latex particles and biological cells (red blood cells and its complexes) are presented. It is shown that the laser beam scanning in flow hemacytometry may be useful not only to solve the blood formula problem but for designing the devices which may give an opportunity to investigate the aggregates of blood cells.

Most methods established so far to estimate RBC deformability are hard to standardize and include high error of measurement. For our present investigation on the effects of oxygen (O₂) and ozone (O₃) on red blood cell (RBC) deformability we used the method of laser diffraction in a combination of image analysis. After exposing RBC to O₂ and/or O₃ mechanical fragility was investigated by filtration of the RBC suspensions (hematocrit 5%) through 3 micrometers pore filter under pressure of 200 mmHg. Fragility remained unchanged after oxygenation. Astonishingly O₃ in concentration >= 7 (mu) g/ml improved mechanical fragility (decrease of hemolysis after mechanical stress).

The unified approach based on multiple scattering provides the conditions to obtain many parameters about biological media during single experiment and study various physical- chemical impacts on biological cells. This optical medium-nonperturbing method has been used for analyzing the action of the blood substitutes in a form of perfluocarbons (PFC) emulsion on the whole blood. Following this methodology we have investigated the absorption coefficient K in spectral range 630 - 950 nm, parameters q/(epsilon) , connected with sizes of erythrocytes and their aggregates as well as the real part of the refractive index of particles and the surrounding media.

Following earlier deriving methods for determination of particle absorption coefficient K and the imaginary part of the refractive index we have been measuring diffuse reflection and relative transmittance of whole blood layers inner depth conditions in the spectral range 600 - 900 nm. The possibility of four derivative hemoglobin forms (oxy-, deoxy-, meth- and carboxy-) determination has been analyzed. The method is proposed for deriving the derivative hemoglobin forms by using the different spectral ranges.

Laser Doppler flowmetry has widely been used to investigate the real time changes of the local blood flow in the inner ear. However the optical properties of the cochlea have not thoroughly been investigated. We have investigated the optical characteristics of the bony layer of the guinea pig cochlea by means of an integrating sphere and determined the absorption and scattering coefficients. A Delrin plate with approximately the same optical properties as the bony layer was used as a model in some of the measurements. In a flow model the geometrical conditions of the cochlea were studied. The flow model consists of a single capillary and the Doppler shifted signals were measured by a single optical fiber. Results show, the changes of the Doppler shifted signals were related to the distance between the photodetector and the scattering medium. From our results we can conclude that the laser Doppler measurements include information on the blood flow in structures deeper than 1 mm below the bone surface (guinea pigs).

A simple and sensitive method to determine tissue scattering dynamic parameters is presented. A mode-locked laser is used as an impulse radiation source. Amplitude and number of generation modes are connected to duration and shape of the pulse via Fourier transformation. Scattered optical signal, containing multiple scattering information, is broadened in comparison with incident pulse. Analysis of the output signal is performed by measuring spectral components on the frequencies of mode beating. This approach allows us to increase sensitivity.

In the present paper a brief overview of the developed methods of blood microcirculation analysis in vivo is given. The theoretical investigations into the processes of focused Gaussian beams diffraction in blood capillaries with a diameter a bit greater than the erythrocyte size have been carried out. Also, the diffraction of focused Gaussian beams in the flows of dissolved blood and its separated components in glass capillaries has been experimentally studied. The range of validity of the measurement method of the blood flow velocity in narrow blood capillaries, using focused Gaussian beams diffraction, has been analyzed.

The theory of the frequency-domain optical flicker spectroscopy of erythrocytes is considered. The modified plane bending model of the flicker is developed. It takes into account the discrete spectrum of membrane bending modes; the influence of cell shape on the flicker spectrum; the viscosity of surrounding medium; and the distortion of the intrinsic shape of the flicker spectrum by the instrumental function of the measuring optical set-up. The results of two other (spherical) flicker models also are analyzed. The theory is compared with the flicker spectra measured from single human erythrocytes using two microphotometric techniques: the phase contrast and the backward laser light scattering.

The structure of multilayer Langmuir-Blodgett (LB) films made of protein (Bovine serum albumine)-co-proporphyrin(III) conjugate was investigated by means of fluorescence microscope coupled with the time-correlated single photon counting registration system. The map of coproporphyrin fluorescence from the surface of protein LB-films was measured with picosecond time resolution and spatial resolution 15 micrometers . The sample area 240 X 240 micrometers was irradiated step by step by a focused beam of Nd:YAG laser with an accumulation time of 3 sec per point. There were two different kinds of samples: those with regular and those with irregular distribution of fluorescent labels over the sample.

The first results of comparative spectral analysis of the bone marrow and blood taken from one and the same donor are presented and the new potentialities of the spectroscopic method for hematologic diseases diagnostics and for testing the pathologic process together with the morphologic investigations of bone marrow punctates are considered. We present here the results of comparative spectral analysis of the bone marrow and blood taken from one and the same donor. We found out what differences in spectra are for normal and pathology bone marrow composition and what causes this difference.

In our earlier works it was shown that application of the autogenerator method in the registering techniques improves instrument accuracy even of common fiber sensors. The proposed device is a new type of autogenerator. The main distinction of it, as compared with the previous one, is the availability of two feedback channels for reference and intelligence signals. This feature is intended both to obtain some higher exactness and to make the device more handy for biomeasurements. The paper includes a detailed description and some performance characteristics of the system.

The brightness of backscattering radiation intensity for the lungs, liver, bone under in skin and muscle of a rabbit has been investigated by a fiber-optic design of special construction at the laser wavelengths 0.63, 0.83, and 1.15 micrometers . A satisfactory agreement between the brightness backscattering radiation intensity and the reflection coefficient for a single layer of the blood, liver, skin and muscle is observed. It permits using the previously proposed asymptotic solution of the theory of radiation transfer for weakly absorbing multilayer structures

Energy absorption, heat transfer and temperature distributions during the interaction of laser radiation pulses with pigmented spherical and spheroidal granules in heterogeneous laminated biotissues are investigated on the basis of mathematical modeling.

The physical processes of the skin hyperthermia accompanying the tissue irradiation by visible laser light is discussed. The numerical model based on the program complex SFEMA takes into account the physical heterogeneity and the absorption power density distribution, which was obtained by the Monte Carlo method. The temperature distribution to boundary condition and laser beam radius was researched. The possibility to obtain the needed temperature distribution was shown.

The ability of MRI to non-invasively monitor energy deposition with high spatial and temporal resolution provides the critical feedback required to make laser therapy procedures safe and efficacious. We have previously proposed the use of polyacrylamide gelatin as a phantom material whose optical and MR properties can be controlled independently by adding different dopants to the base gel. We have also begun to investigate the most effective imaging strategies for measuring temperature variations within this material. In this paper we further characterize the gels, delineate the temperature dependance of their MR properties and show how imaging can be used to determine thermal contours within an interstitially laser-irradiated gel.

A model of the calculation of the diffuse reflection of the living tissue based on Kubelka-Munk theory is presented. The equation describing the relationship between backscattering of the living tissue and radiation parameters, inanimate tissue optical characteristics, and chromophores concentration is outlined. The use of the method in clinical dosimetry is given.

Analytic theory of anisotropic random flight requires the expansion of phase-functions in spherical harmonics. The number of terms should be limited while a g value should be obtained that is as high as possible. We describe how such a phase function can be constructed for a given number N of spherical components of the phasefunction, while obtaining a maximum value of the asymmetry parameter g.

A method of measuring the sphere equivalent hydrodynamic radius in highly concentrated suspensions is reported. Results showing the system to be concentration independent are given. The effects of polarization and the use of high birefringence fibers are discussed and shown to be important. The possibility of independence to fluid flow and the monitoring of the enhanced backscatter cone to given information on structure are considered. The equipment allows the use of a dip in probe and laser powers of only 1 mW are required.