Irina Bliznakova | Institute of Electronics, Bulgarian Academy of Sceinces (original) (raw)
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Papers by Irina Bliznakova
Acta Physica Polonica Series a
Photodiagnosis and photodynamic therapy of non-melanoma skin can-cers using delta-aminolevulinic ... more Photodiagnosis and photodynamic therapy of non-melanoma skin can-cers using delta-aminolevulinic acid/protoporphyrin IX (5-ALA/PpIX) give a combined application with broadest dissemination in the current clinical practice. The problems with using of lasers as light sources are the expenses associated with the operation of these types of installations. This is why we test the capability of cheaper sources — light-emitting diodes at 405 nm for fluorescence excitation of PpIX and 635 nm for photodynamic action initia-tion. A LED matrix is developed in our laboratory using two types of LEDs and a combined photodiagnosis/photodynamic theory device applicable for clinical practice is built. Geometrically matrix is formed in such way that power density at 635 nm is about 40 mW/cm 2 , which allow to reach treat-ment doses for a 15–20 min irradiation depending of the lesion size in the focus of the system. The therapeutic mode of system developed can be used also with some other photosensiti...
Acta Physica Polonica Series a
Human skin contains various types of native fluorophores and absorbers with unique absorption and... more Human skin contains various types of native fluorophores and absorbers with unique absorption and emission spectra, different quantum efficiency, concentration and spatial distribution within the skin. Autofluorescence spectroscopy is applied as diagnostic tool for cutaneous tumor detection that increases the importance of evaluation of natural existing fluorophores and unification of data for given class of pathologies. In the current study, several excitation sources in the region 337-405 nm are applied, to achieve information about typical autofluorescent properties of normal human skin.
Journal of Biomedical Optics
The propagation is investigated of a continuous laser beam through homogeneous tissue-like turbid... more The propagation is investigated of a continuous laser beam through homogeneous tissue-like turbid media such as diluted emulsions of Intralipid or milk. The cross sectional radial distributions of the detected forward-propagating light power at different depths along the beam axis in each medium of interest are experimentally determined. The detected-power spatial distribution is also described analytically by a solution of the radiative transfer equation for the case of sharply forward directed indicatrices. It is shown that the experimental results are consistent with the analytical expressions obtained over the corresponding ranges of validity of the latter. It is shown as well that the analytical expressions would allow one to estimate the extinction, reduced-scattering and absorption coefficients as well as the gfactor of the investigated media on the basis of the experimental data.
15th International School on Quantum Electronics: Laser Physics and Applications, 2008
The spatial parameters of scattered light in turbid media with different degrees of turbidity and... more The spatial parameters of scattered light in turbid media with different degrees of turbidity and at various depths are studied in this work. The measurements are made at two wavelengths (687 nm and 850 nm). A collimated laser radiation is used in the experiments in order to avoid the effect of input laser beam structure on the measured optical fields. The radial and in depth distribution is measured of the intensity of the forward-scattered optical beam radiation in turbid (tissue-like) media. The influence of small ingredients within the turbid media is also analyzed. The optical properties of the ingredients are different from those of the surrounding turbid medium. Milk-water mixtures are used as a test medium. The intensity distribution within milk solutions with concentrations ranging from 3.3% to 16.5% is measured in depth of more than 10 cm. The experimental results indicate that the presence of small ingredients within the phantom leads to characteristic changes of the intensity distribution. These preliminary results are evaluated as promising for developing a novel technique for determination of optical characteristics of small embedded ingredients in turbid media.
Special optical system for non-invasive determination of small variations in the optical properti... more Special optical system for non-invasive determination of small variations in the optical properties of homogeneous turbid inclusions embedded into large turbid medium is proposed and developed experimentally. Results for different choice of the optical parameters of both media are presented. The minimum detectable changes in the inclusion optical properties are estimated to be less than 5% with respect to the surrounding medium. It is shown that the output signals depend not only on the relative magnitude but also on the sign of the difference in optical properties of both media. The results could be used for developing techniques and algorithms for distinguishing of different kinds of abnormal formations.
MATEC Web of Conferences, 2013
We compare the morphological modifications in gelatin films, induced with an 800nm femtosecond am... more We compare the morphological modifications in gelatin films, induced with an 800nm femtosecond amplifier, in subject of the number of input pulses and the input pulse duration. Foam is formed in all cases, but only under certain conditions the desirable structures that mimic the native subcellular matrix are formed. The number of input pulses significantly changes the foam structure, allowing a well-defined nano-structuring for optimal tissue-engineering.
In this study are presented some initial results using LEDs as excitation sources for the needs o... more In this study are presented some initial results using LEDs as excitation sources for the needs of fluorescence spectroscopy of the skin, which are compared with the results obtained by nitrogen laser used as excitation source for cutaneous fluorescence. The main studies are made by developed in IE-BAS experimental fibro-optic system for fluorescence spectroscopy. Several volunteers, representative of each skin phototype typical for Bulgarian region, namely--phototypes I, II and III were investigated by the methods of fluorescence spectroscopy of the human skin on several anatomic sites, typical for this type of measurements--palm, medial part of the forearm and lateral part of the forearm. Fluorescence maxima detected are addressed to the typical fluorophores existing in the cutaneous tissues. Influence of main skin absorbers, namely melanin and hemoglobin, is also discussed and their impact on the fluorescence signals received from different anatomical areas and skin phototypes is determined.
Current Management of Malignant Melanoma, 2011
Diagnostic Optical Spectroscopy in Biomedicine IV, 2007
... E. Drakaki, E. Borisova, M. Makropoulou, L. Avramov, AA Serafetinides, I. Angelov, “Laser ind... more ... E. Drakaki, E. Borisova, M. Makropoulou, L. Avramov, AA Serafetinides, I. Angelov, “Laser induced autofluorescence studies of animal skin used in modeling of human cutaneous tissue spectroscopic measurements”, Skin Res&Tech 13: doi:10.1111/j.1600-0846.2007.00237.x ...
Acta Physica Polonica A - ACTA PHYS POL A, 2007
Human skin contains various types of native fluorophores and absorbers with unique absorption and... more Human skin contains various types of native fluorophores and absorbers with unique absorption and emission spectra, different quantum efficiency, concentration and spatial distribution within the skin. Autofluorescence spectroscopy is applied as diagnostic tool for cutaneous tumor detection that increases the importance of evaluation of natural existing fluorophores and unification of data for given class of pathologies. In the current study, several excitation sources in the region 337-405 nm are applied, to achieve information about typical autofluorescent properties of normal human skin.
Physica Scripta, 2012
The propagation of a continuous laser beam through homogeneous tissue-like liquid turbid media ha... more The propagation of a continuous laser beam through homogeneous tissue-like liquid turbid media having sharply forward-directed Henyey-Greenstein indicatrices is studied. The in-depth on-axis and cross-sectional radial distributions of the detected forward-propagating light power are experimentally determined. The spatial distribution of the detected power is also described analytically by solving the radiative transfer equation in the so-called small-angle approximation. The experimental results are consistent with the analytical expressions obtained that are shown to allow one to estimate the extinction, reduced-scattering and absorption coefficients and the g-factor of the investigated media.
Applied Surface Science, 2012
Results are presented on the synthesis and characterization of nanocomposite Ag/ZnO heterostructu... more Results are presented on the synthesis and characterization of nanocomposite Ag/ZnO heterostructures on fused quartz substrates. The experiments were performed by pulsed laser deposition (PLD) using a third harmonic Nd:YAG laser in a vacuum chamber. The ablation of a rotated Ag target was followed by laser modification of the deposited layer and subsequent deposition of ZnO. The process factors, such as the silver film thickness and the post-deposition annealing procedures, were varied in view of controlling the diameter and size distribution of the Ag nanoparticles. The annealing regimes were modified by varying the laser irradiation energy on the Ag layers. The effect on the Ag/ZnO properties is discussed. It is demonstrated that the photoluminescence intensity of ZnO nanolayers is significantly enhanced by plasmon absorption in the Ag nanoparticles and a shift to the lower wavelengths.
Applied Physics B, 2013
ABSTRACT The possibility is studied to develop a straightforward analytical approach to the deter... more ABSTRACT The possibility is studied to develop a straightforward analytical approach to the determination of the optical properties of liquid turbid media having forward-peaked scattering indicatrices. The approach is based on investigating the in-depth behavior of the radius and the axial intensity of a laser radiation beam propagating through the turbid medium. Based on the small-angle approximation, the detected forward-propagating light power spatial distribution, at relatively small or large optical depths along the beam axis, is obtained asymptotically in analytical form allowing one to derive relatively simple expressions of the extinction, reduced-scattering and absorption coefficients and the anisotropy factor of the medium through the characteristics of the propagating light beam. Preliminary experiments have also been performed, using Intralipid dilutions of different relatively low concentrations and measuring the cross-sectional radial distribution of the detected light power at different depths along the beam axis. The corresponding on-axis detected light power profiles have been measured independently as well. The experimental results are consistent with the analytical expressions obtained that allow one to estimate the optical coefficients and the anisotropy factor of the investigated media on the basis of the measured beam characteristics. The values obtained are near those predicted by other researchers.
Fluorescence Spectroscopy of the human skin is very prominent for early diagnosis and differentia... more Fluorescence Spectroscopy of the human skin is very prominent for early diagnosis and differentiation of cutaneous diseases. Selection of proper excitation sources and sensitive detectors gives wide range of possibilities related to real-time determination of existing pathological conditions. A problem with using laser as an excitation source is the high expenses associated with the operation of these types of installations.
We report on the structural investigation of self-organized micropores generated in thin gelatin,... more We report on the structural investigation of self-organized micropores generated in thin gelatin, colla-gen, and collagen–elastin films after single and multishot irradiation with pulse durations ranging from30–100 fs at 800 nm. We systematically studied the effect of laser parameters: laser energy, number ofpulses, and pulse duration on the development of the micropores. This work showed that applying laserpulses at different rates significantly modified the thin film surface. The results clearly revealed that fem-tosecond laser treatment of thin films of biomaterials: gelatin, collagen and collagen–elastin, results increation of micro/nanopores with different size of cavity formations. Experimentally, it is demonstratedthat it is possible to influence the dimensions of the pore sizes, ranging from 100 nm to 2 m by tuningthe laser parameters. We are currently further exploring the possibility of structuring these biomaterialsby applying a time delay between separate pulses. First results from cell culture experiments on lasercreated surface foam of collagen–elastin were successfully obtained, showing the potential of the methodto cultivate cells on superficial porous substrates and the preferable selectivity of the cells to proliferateon the laser modified parts of the biopolymer substrate.
Acta Physica Polonica Series a
Photodiagnosis and photodynamic therapy of non-melanoma skin can-cers using delta-aminolevulinic ... more Photodiagnosis and photodynamic therapy of non-melanoma skin can-cers using delta-aminolevulinic acid/protoporphyrin IX (5-ALA/PpIX) give a combined application with broadest dissemination in the current clinical practice. The problems with using of lasers as light sources are the expenses associated with the operation of these types of installations. This is why we test the capability of cheaper sources — light-emitting diodes at 405 nm for fluorescence excitation of PpIX and 635 nm for photodynamic action initia-tion. A LED matrix is developed in our laboratory using two types of LEDs and a combined photodiagnosis/photodynamic theory device applicable for clinical practice is built. Geometrically matrix is formed in such way that power density at 635 nm is about 40 mW/cm 2 , which allow to reach treat-ment doses for a 15–20 min irradiation depending of the lesion size in the focus of the system. The therapeutic mode of system developed can be used also with some other photosensiti...
Acta Physica Polonica Series a
Human skin contains various types of native fluorophores and absorbers with unique absorption and... more Human skin contains various types of native fluorophores and absorbers with unique absorption and emission spectra, different quantum efficiency, concentration and spatial distribution within the skin. Autofluorescence spectroscopy is applied as diagnostic tool for cutaneous tumor detection that increases the importance of evaluation of natural existing fluorophores and unification of data for given class of pathologies. In the current study, several excitation sources in the region 337-405 nm are applied, to achieve information about typical autofluorescent properties of normal human skin.
Journal of Biomedical Optics
The propagation is investigated of a continuous laser beam through homogeneous tissue-like turbid... more The propagation is investigated of a continuous laser beam through homogeneous tissue-like turbid media such as diluted emulsions of Intralipid or milk. The cross sectional radial distributions of the detected forward-propagating light power at different depths along the beam axis in each medium of interest are experimentally determined. The detected-power spatial distribution is also described analytically by a solution of the radiative transfer equation for the case of sharply forward directed indicatrices. It is shown that the experimental results are consistent with the analytical expressions obtained over the corresponding ranges of validity of the latter. It is shown as well that the analytical expressions would allow one to estimate the extinction, reduced-scattering and absorption coefficients as well as the gfactor of the investigated media on the basis of the experimental data.
15th International School on Quantum Electronics: Laser Physics and Applications, 2008
The spatial parameters of scattered light in turbid media with different degrees of turbidity and... more The spatial parameters of scattered light in turbid media with different degrees of turbidity and at various depths are studied in this work. The measurements are made at two wavelengths (687 nm and 850 nm). A collimated laser radiation is used in the experiments in order to avoid the effect of input laser beam structure on the measured optical fields. The radial and in depth distribution is measured of the intensity of the forward-scattered optical beam radiation in turbid (tissue-like) media. The influence of small ingredients within the turbid media is also analyzed. The optical properties of the ingredients are different from those of the surrounding turbid medium. Milk-water mixtures are used as a test medium. The intensity distribution within milk solutions with concentrations ranging from 3.3% to 16.5% is measured in depth of more than 10 cm. The experimental results indicate that the presence of small ingredients within the phantom leads to characteristic changes of the intensity distribution. These preliminary results are evaluated as promising for developing a novel technique for determination of optical characteristics of small embedded ingredients in turbid media.
Special optical system for non-invasive determination of small variations in the optical properti... more Special optical system for non-invasive determination of small variations in the optical properties of homogeneous turbid inclusions embedded into large turbid medium is proposed and developed experimentally. Results for different choice of the optical parameters of both media are presented. The minimum detectable changes in the inclusion optical properties are estimated to be less than 5% with respect to the surrounding medium. It is shown that the output signals depend not only on the relative magnitude but also on the sign of the difference in optical properties of both media. The results could be used for developing techniques and algorithms for distinguishing of different kinds of abnormal formations.
MATEC Web of Conferences, 2013
We compare the morphological modifications in gelatin films, induced with an 800nm femtosecond am... more We compare the morphological modifications in gelatin films, induced with an 800nm femtosecond amplifier, in subject of the number of input pulses and the input pulse duration. Foam is formed in all cases, but only under certain conditions the desirable structures that mimic the native subcellular matrix are formed. The number of input pulses significantly changes the foam structure, allowing a well-defined nano-structuring for optimal tissue-engineering.
In this study are presented some initial results using LEDs as excitation sources for the needs o... more In this study are presented some initial results using LEDs as excitation sources for the needs of fluorescence spectroscopy of the skin, which are compared with the results obtained by nitrogen laser used as excitation source for cutaneous fluorescence. The main studies are made by developed in IE-BAS experimental fibro-optic system for fluorescence spectroscopy. Several volunteers, representative of each skin phototype typical for Bulgarian region, namely--phototypes I, II and III were investigated by the methods of fluorescence spectroscopy of the human skin on several anatomic sites, typical for this type of measurements--palm, medial part of the forearm and lateral part of the forearm. Fluorescence maxima detected are addressed to the typical fluorophores existing in the cutaneous tissues. Influence of main skin absorbers, namely melanin and hemoglobin, is also discussed and their impact on the fluorescence signals received from different anatomical areas and skin phototypes is determined.
Current Management of Malignant Melanoma, 2011
Diagnostic Optical Spectroscopy in Biomedicine IV, 2007
... E. Drakaki, E. Borisova, M. Makropoulou, L. Avramov, AA Serafetinides, I. Angelov, “Laser ind... more ... E. Drakaki, E. Borisova, M. Makropoulou, L. Avramov, AA Serafetinides, I. Angelov, “Laser induced autofluorescence studies of animal skin used in modeling of human cutaneous tissue spectroscopic measurements”, Skin Res&Tech 13: doi:10.1111/j.1600-0846.2007.00237.x ...
Acta Physica Polonica A - ACTA PHYS POL A, 2007
Human skin contains various types of native fluorophores and absorbers with unique absorption and... more Human skin contains various types of native fluorophores and absorbers with unique absorption and emission spectra, different quantum efficiency, concentration and spatial distribution within the skin. Autofluorescence spectroscopy is applied as diagnostic tool for cutaneous tumor detection that increases the importance of evaluation of natural existing fluorophores and unification of data for given class of pathologies. In the current study, several excitation sources in the region 337-405 nm are applied, to achieve information about typical autofluorescent properties of normal human skin.
Physica Scripta, 2012
The propagation of a continuous laser beam through homogeneous tissue-like liquid turbid media ha... more The propagation of a continuous laser beam through homogeneous tissue-like liquid turbid media having sharply forward-directed Henyey-Greenstein indicatrices is studied. The in-depth on-axis and cross-sectional radial distributions of the detected forward-propagating light power are experimentally determined. The spatial distribution of the detected power is also described analytically by solving the radiative transfer equation in the so-called small-angle approximation. The experimental results are consistent with the analytical expressions obtained that are shown to allow one to estimate the extinction, reduced-scattering and absorption coefficients and the g-factor of the investigated media.
Applied Surface Science, 2012
Results are presented on the synthesis and characterization of nanocomposite Ag/ZnO heterostructu... more Results are presented on the synthesis and characterization of nanocomposite Ag/ZnO heterostructures on fused quartz substrates. The experiments were performed by pulsed laser deposition (PLD) using a third harmonic Nd:YAG laser in a vacuum chamber. The ablation of a rotated Ag target was followed by laser modification of the deposited layer and subsequent deposition of ZnO. The process factors, such as the silver film thickness and the post-deposition annealing procedures, were varied in view of controlling the diameter and size distribution of the Ag nanoparticles. The annealing regimes were modified by varying the laser irradiation energy on the Ag layers. The effect on the Ag/ZnO properties is discussed. It is demonstrated that the photoluminescence intensity of ZnO nanolayers is significantly enhanced by plasmon absorption in the Ag nanoparticles and a shift to the lower wavelengths.
Applied Physics B, 2013
ABSTRACT The possibility is studied to develop a straightforward analytical approach to the deter... more ABSTRACT The possibility is studied to develop a straightforward analytical approach to the determination of the optical properties of liquid turbid media having forward-peaked scattering indicatrices. The approach is based on investigating the in-depth behavior of the radius and the axial intensity of a laser radiation beam propagating through the turbid medium. Based on the small-angle approximation, the detected forward-propagating light power spatial distribution, at relatively small or large optical depths along the beam axis, is obtained asymptotically in analytical form allowing one to derive relatively simple expressions of the extinction, reduced-scattering and absorption coefficients and the anisotropy factor of the medium through the characteristics of the propagating light beam. Preliminary experiments have also been performed, using Intralipid dilutions of different relatively low concentrations and measuring the cross-sectional radial distribution of the detected light power at different depths along the beam axis. The corresponding on-axis detected light power profiles have been measured independently as well. The experimental results are consistent with the analytical expressions obtained that allow one to estimate the optical coefficients and the anisotropy factor of the investigated media on the basis of the measured beam characteristics. The values obtained are near those predicted by other researchers.
Fluorescence Spectroscopy of the human skin is very prominent for early diagnosis and differentia... more Fluorescence Spectroscopy of the human skin is very prominent for early diagnosis and differentiation of cutaneous diseases. Selection of proper excitation sources and sensitive detectors gives wide range of possibilities related to real-time determination of existing pathological conditions. A problem with using laser as an excitation source is the high expenses associated with the operation of these types of installations.
We report on the structural investigation of self-organized micropores generated in thin gelatin,... more We report on the structural investigation of self-organized micropores generated in thin gelatin, colla-gen, and collagen–elastin films after single and multishot irradiation with pulse durations ranging from30–100 fs at 800 nm. We systematically studied the effect of laser parameters: laser energy, number ofpulses, and pulse duration on the development of the micropores. This work showed that applying laserpulses at different rates significantly modified the thin film surface. The results clearly revealed that fem-tosecond laser treatment of thin films of biomaterials: gelatin, collagen and collagen–elastin, results increation of micro/nanopores with different size of cavity formations. Experimentally, it is demonstratedthat it is possible to influence the dimensions of the pore sizes, ranging from 100 nm to 2 m by tuningthe laser parameters. We are currently further exploring the possibility of structuring these biomaterialsby applying a time delay between separate pulses. First results from cell culture experiments on lasercreated surface foam of collagen–elastin were successfully obtained, showing the potential of the methodto cultivate cells on superficial porous substrates and the preferable selectivity of the cells to proliferateon the laser modified parts of the biopolymer substrate.