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Background and Objective The number of in vitro experimental studies was carried out with the use of intact tissues to establish a mechanism of laser–tissue interaction. However, in the process of degeneration, both biochemical composition and behavior of the disc were altered drastically. The objective of this study was to evaluate the role of the main matrix components in laser modification of annulus fibrosus (AF) under IR laser irradiation. Study Designs/Materials and Methods The samples of AF in a motion segment after hyaluronidase treatment, trypsin digestion and glycation by glyceraldehyde were heated in hydrothermal bath (95°C, 2 min) or irradiated by laser at 1.56 µm. Specimens were imaged by cross-polarization optical coherence tomography (CP-OCT), and then analyzed by differential scanning calorimery (DSC). Results and Discussion According to CP-OCT and DSC data non-significant alteration was revealed in AF after hyaluronidase treatment, glycation led to stabilization of annulus collagen and trypsin digestion resulted in a noticeable impairment of collagen fibrils. Laser treatment induced subsequent damages of AF matrix but these damages cannot be explained by laser heating only. The specificity of chemical modification of AF matrix has an influence on a character of collagen network alteration due to IR laser effect. Minimal and maximal alterations are observed for hyaluronidase and trypsin treated samples respectively. Glyceraldehyde fixed samples showed failure of the collagen structure after moderate laser treatment; at the same time thermal denaturation of collagen macromolecules was negligible. We assume that a mechanical effect of laser irradiation plays an important role in laser-induced annulus collagen modification and propose the scheme of physico-chemical process occurring under non-uniform IR laser treatment in AF tissue. Conclusion CP-OCT and DSC techniques allow us to record the alteration of collagen network organization as a result of chemical modification. There were detected significant and specific effects of the biochemical composition and material properties on the response of AF collagen network on laser irradiation. The results go in accordance with our hypothesis that the primary effect of laser influence on collagen network under tension is the mechanical damage of collagen fiber. Lesers Surg. Med. 40:422–432, 2008. © 2008 Wiley-Liss, Inc.

We have investigated the effect of application of gold nanoshells with a 150 nm silica core size and 25 nm thick gold coating on optical properties of skin. We have analyzed the possibility of using these particles as a contrasting agent for optical coherence tomography (OCT). A set of Monte Carlo calculations was performed in order to simulate the images of skin before and after application of the nanoshells for a skin model close to that in vivo. We investigated the mechanisms of boundary contrasting between tissue layers with different optical properties in the presence of gold nanoshells on two-layer agar gel phantom. Gold nanoshells were also applied on the skin surface in vivo. Gold-silica nanoshells caused an increase in the intensity of OCT signal, brightness of the superficial part of the dermis, contrast between dermis layers and contrast of hair follicles and glands in the OCT image. The contrasting effects of the gold nanoshells lasted up to 24 hours of observation.

We have investigated the effect of application of gold nanoparticles with a diameter of 50 nm and nanoshells with a 150 nm silica core size and 25 nm thick gold shell on optical properties of skin. We have analyzed the possibility of using these particles as a contrasting agent for optical coherence tomography (OCT). As the first step in the study, effects of gold nanoparticles after one application to skin were studied using OCT. Then we evaluated the effects of multiple applications of 50 nm gold nanoparticles to skin in 30-minute intervals. Biopsy of relevant skin areas was performed under local anaesthesia and samples for light and electron microscopy were prepared. Identification of skin layers on OCT images was made by comparing with histology. Application of gold-silica nanoshells caused increase in intensity of useful signal, brightness of the superficial part of the dermis and contrast between the superficial and deep parts of the dermis 30 minutes after application on skin. After 24 hours the changes in OCT images became more pronounced as the brightness of the superficial part of the dermis and the contrast between the superficial and deep parts of the dermis further increased. In addition, the border between the superficial and deep parts of the dermis became more distinct, continuous and well discernible, permitting to accurately differentiate these layers. Besides that, the application of nanoshells caused contrasting of hair follicles and glands. In order to give interpretation to the obtained experimental OCT-images of skin and understand the mechanisms of contrasting a set of Monte Carlo calculations was performed in order to simulate the images of skin before and after application of the nanoparticles for skin model close to that in the experiment. The results of the simulation exhibit good qualitative agreement with the experimental images and prove that the contrasting originates from the nanoparticles added while contrasting of hair bulb originates from the absence of nanoparticles in it with their presence in surrounding area.

Strong light scattering and absorption limit observation of the internal structure of biological tissue. Only special tools for turbid media imaging, such as optical diffuse tomography, enable noninvasive investigation of the internal biological tissues, including visualization and intravital monitoring of deep tumors. In this work the preliminary results of diffuse fluorescence tomography (DFT) of small animals are presented. Usage of exogenous fluorophores, targeted specifically at tumor cells, and fluorescent proteins expressed endogenously can significantly increase the contrast of obtained images. Fluorescent compounds of different nature, such as sulphonated aluminium phthalocyanine (Photosens), red fluorescing proteins and CdTe/CdSe-core/shell nanocrystals (quantum dots) were applied. We tested diffuse fluorescence tomography method at model media, in post mortem and in vivo experiments. The animal was scanned in transilluminative configuration by low-frequency modulated light (1 kHz) from Nd:YAG laser with second harmonic generation at wavelength of 532 nm or semiconductor laser at wavelength of 655 nm. Quantum dots or protein DsRed2 in glass capsules (inner diameter 2-3 mm) were placed post mortem inside the esophagus of 7-day-old hairless rats to simulate marked tumors. Photosens was injected intravenously to linear mice with metastazing Lewis lung carcinoma. The reconstruction algorithm, based on Algebraic Reconstruction Technique, was created and tested numerically in model experiments. High contrast images of tumor simulating capsules with DsRed2 concentrations about 10 -6 M and quantum dots about 5x10 -11 M have been obtained. Organ distribution of Photosens and its accumulation in tumors and surrounding tissues of animals has been examined. We have conducted the monitoring of tumors, exogenously labeled by photosensitizer. This work demonstrates potential capabilities of DFT method for intravital detection and monitoring of deep fluorescent-labeled tumors in animal models. The comparative analysis of conventional photosensitizer, fluorescent proteins and quantum dots has been carried out.

An experimental setup for multicolor frequency-domain optical diffuse tomography was designed to visualize soft biological tissue inhomogeneities at the distance of up to 6 cm. Scanning is performed by independent electronically controlled shift of source and detector placed in transmission mode. Employing illumination at three wavelengths (684, 794, and 1060 nm) which correspond to predominating absorption of oxygenated hemoglobin, deoxygenated hemoglobin and water provides determination of component composition of an inhomogeneity. Source power modulation at 140 MHz increases spatial resolution (compared to CW imaging) and improves quality of reconstruction procedure. Studies on model media and preliminary in vivo experiments were performed.

We propose to realize an endoscopic all-fiber clinical device for polarized reflectance spectroscopy based on polarization-maintaining (PM) fiber. Results of testing the above device in model media and the first data of clinical investigations are presented. Investigations in vivo were carried out on the uterine cervix with benign and malignant alterations. 7 female patients were examined. POR technique confirm a possibility of differentiating neoplastic changes by the depolarization ratio.

Fluorescent compounds for selective cancer cell marking are used for development of novel medical diagnostic methods, investigation of the influence of external factors on tumor growth, regress and metastasis. Only special tools for turbid media imaging, such as optical diffusion tomography permit noninvasive monitoring of fluorescent-labeled tumor alterations deep in animal tissue. In this work, the results of preliminary experiments utilizing frequency-domain fluorescent diffusion tomography (FD FDT) experimental setup in small animal are presented. Low-frequency modulated light (1 kHz) from Nd:YAG laser with second harmonic generation at the wavelength of 532 nm was used in the setup. The transilluminative planar configuration was used in the setup. A series of model experiments has been conducted and show good agreement between theoretical and experimental fluorescence intensity. Models of deep tumors were created by two methods: (1) glass capsules containing fluorophore solution were inserted into esophagus of small animals to simulate marked tumors; (2) a suspension of transfected HEK293-Turbo-RFP cells was subcutaneously injected to small animal. The conducted experiments have shown that FD FDT allows one to detect the presence of labeled tumor cells in small animals, to determine the volume of an experimental tumor, to perform 3D tumor reconstruction, as well as to conduct monitoring investigations. The obtained results demonstrate the potential capability of the FD FDT method for noninvasive whole-body imaging in cancer studies, diagnostics and therapy.

The main applications of fluorescent proteins (FPs) are monitoring tumor growth, angiogenesis, metastases formation and effects of new classes of drugs. Different types of tomography allow fluorescence imaging of tumors located deep in human or animal tissue. These techniques were used for investigation of the distribution of near-infrared fluorescent probes, but only a few works are devoted to fluorescence tomography in visible light. In this work, preliminary results of the frequency domain fluorescent diffuse tomography (FD FDT) method in application to DsRed2 protein as a fluorescent agent are presented. For the first step of our experiments we utilized second harmonic generation of Nd:YAG laser (532 nm) modulated by low frequency (1 kHz) in the experimental setup. The transilluminative planar configuration was used in the setup. A series of model experiments has been conducted and show good agreement between theoretical and experimental fluorescence intensity. Post mortem experiments with capsules containing DsRed2 and scattering solution introduced into esophagus of rats to simulate tumor formation have been conducted. The results of these experiments show that sensitivity of the setup is sufficient to detect DsRed2 in concentrations similar to those in FP-expressed tumor, but the contrast is not enough high to separate fluorescence of DsRed2 and surrounding tissues. The setup can be significantly improved by utilizing high-frequency modulation (110 MHz using acousto-optical modulator) of the excitation light and precise phase measurements due to difference in fluorescence life-time of FPs and surrounding tissues. An algorithm of processing a fluorescent image based on calculating zero of maximum curvature was employed for detection of fluorescent inclusions boundaries in the image.

We present the results in optical coherence tomography (OCT) visualization of structural changes in human oral cavity and pharyngeal mucosa for 14 patients in the process of radiation and chemoradiation therapy. Typical mucosal changes are seen as a decrease in the tissue layer contrast progressing to a complete contrast loss as severe mucosal damage occurs. Similar evolution in OCT images was observed for all patients. OCT changes can be seen prior to visual mucosal changes and increased as more mucosal damage occurs. Moreover, OCT was able to obtain information on the specific features of the patient response depending on the irradiation method and the individual radiosensitivity.

A numerical algorithm based on a small-angle approximation of the radiative transfer equation (RTE) is developed to reconstruct scattering characteristics of biological tissues from optical coherence tomography (OCT) images. According to the algorithm, biological tissue is considered to be a layered random medium with a set of scattering parameters in each layer: total scattering coefficient, variance of a small-angle scattering phase function, and probability of backscattering, which fully describe the OCT signal behavior versus probing depth. The reconstruction of the scattering parameters is performed by their variation to fit the experimental OCT signal by the theoretical one using a time-saving genetic algorithm. The proposed reconstruction procedure is tested on model media with known scattering parameters. The possibility to estimate scattering parameters from OCT images is studied for various regimes of OCT signal decay. The developed algorithm is applied to reconstruct optical characteristics of epithelium and stroma for normal cervical tissue and its pathologies, and the potential to distinguish between the types of pathological changes in epithelial tissue by its OCT images is demonstrated.

Results of the research carried out at the Institute of Applied Physics US (IAP RAS) in collaboration with the Nizhny Novgorod Medical Academy are presented. The obtained data demonstrate capabilities of Optical Coherence Tomography (OCT), Polarization-Sensitive OCT (PS OCT), and Optical Coherence Microscopy (OCM) for biomedicine. Also we present our first results on Frequency-Domain Optical Diffusion Tomography (FD ODT) and Frequency-Domain Fluorescence Diffusion Tomography (FD FDT). OCT, CP OCT and OCT are high-resolution (3- 15 mcm) techniques used for visualization of near surface objects (at depths up to 2 mm). ODT and FDT have lower resolution (4-8 mm), but they allow investigation at depths up to 5-10 cm.

We present preliminary results of the frequency domain fluorescent diffuse tomography (FD FDT) method in application to fluorescent proteins. For first step in the experimental setup we utilized light-emitting diode (530 nm wavelength) modulated with low frequency (18 kHz). A model experiments with capsules containing DsRed suspension in scattering medium has been conducted. The results of post mortem experiments with capsules containing DsRed, introduced into abdominal cavity of mice to simulate tumors inside animal body, are presented. An algorithm of processing fluorescent image based on calculating zero of maximum curvature has been applied to detect fluorescent inclusions boundaries on the image.

Clinical studies using OCT involved 2000 patients in various fields of medicine such as gastroenterology, urology, laryngology, gynecology, dermatology, stomatology, etc. Layered high-contrast images were typical for benign epithelial conditions. OCT distinguish in mucosae: epithelium, connective tissue layer, and smooth-muscle layer. Various benign processes occurring in mucosa manifest in OCT images as changes in the epithelial height, scattering properties and the course of the basement membrane. Lack of the layered structural pattern is the main criterion for dysplastic / malignant images. In clinic: OCT data may be critical for choosing a tissue site for excisional biopsy, OCT can detect tumor borders and their linear dimensions, OCT can be used to plan a resection line in operations and to control adequacy of resection, to monitor whether reparative processes are timely and adequate. OCT sensitivity of the uterine cervix, urinary bladder and larynx is 82, 98, 77%, respectively, specificity - 78, 71, 96%, diagnostic accuracy - 81, 85, 87% with significantly good agreement index of clinicians kappa - 0.65, 0.79, 0.83 (confidence intervals: 0.57-0.73; 0.71-0.88; 0.74-0.91). Error in detection of high grade dysplasia and microinvasive cancer is 21.4% in average. Additional modification of OCT (cross-polarisation OCT, OCM), development of the procedure (biotissue compression, application of chemical agents) can improve the specificity and sensitivity of traditional modality.

Our goal was statistical assessment of the in vivo cystoscopic optical coherence tomography (OCT) ability to detect neoplasia in human urinary bladder. We analyzed major reasons of false positive and false negative image recognition results. Optical coherence tomography was performed to image the bladder during cystoscopy. The study enrolled 63 patients with suspicion for bladder cancer and scheduled for cystoscopy. The diagnosis was established by histopathology examination of a biopsy. Each biopsy site was examined by OCT. Benign conditions were diagnosed for 31 patients, and dysplasia or carcinoma were diagnosed for 32 patients. Six physicians blinded to all clinical data participated in the dichotomy recognition (malignant or benign) of the OCT images. 98% sensitivity and 72% specificity for the OCT recognition of dysplastic/malignant versus benign/reactive conditions of the bladder are demonstrated. Total error rate was 14.8%. The interobserver agreement multi-rater kappa coefficient is 0.80. The superficial and invasive bladder cancer and high-grade dysplasia were recognized with minimum error rate ranging from 0 to 3.3%. High sensitivity and good specificity of the OCT method in the diagnostics of bladder neoplasia makes OCT a promising complementary cystoscopic technique for non-invasive evaluation of zones suspicious for high-grade dysplasia and cancer.

We performed blind recognition of optical coherence tomography (OCT) images of human urinary bladder for diagnostics of carcinoma and premalignant conditions. OCT images of 63 patients were acquired in vivo during cystoscopic examination. The malignant/premalignant conditions were differentiated from benign/reactive with 98% sensitivity and 72% specificity. OCT was also used for intraoperative monitoring of zones around the tumor for adequate resection (31 patients). OCT - guided planning of the resection margin and examination of the postoperative resection line after transurethral resection (TUR) was performed.

First experimental results on OCT imaging of internal structure of plant tissues and in situ OCT monitoring of plant tissue regeneration at different water supply are reported. Experiments for evaluating OCT capabilities were performed on Tradescantia. The investigation of seeds swelling was performed on wheat seeds (Triticum L.), barley seeds (Hordeum L.), long-fibred flax seeds (Linum usitatissimum L.) and cucumber seeds (Cucumis sativus L.). These OCT images correlate with standard microscopy data from the same tissue regions. Seeds were exposed to a low-intensity physical factor-the pulsed gradient magnetic field (GMF) with pulse duration 0.1 s and maximum amplitude 5 mT (4 successive pulses during 0.4 s). OCT and OCM enable effective monitoring of fast reactions in plants and seeds at different water supply.

The optical coherence tomography (OCT) capabilities of plants were evaluated using leaves of Tradescantia pallida (Rose) D. Hunt. The internal structure of the leaf tissues was visualized in vivo and the physiological and morphological states of the tissues under different water supply conditions were monitored using OCT. The OCT technique provides non-invasive two-dimensional images directly on intact plants. The acquisition time of a two-dimensional image with a size of 200x200 pixels and a spatial resolution of 15 microm is 1-3 s. It was shown that OCT is a useful tool for monitoring the physiological and morphological states of plant tissues supplied with varying amounts of water and under the influence of different chemical factors.

We report results of systematic clinical studies using conventional OCT and its modification cross-polarized OCT in the larynx. Conventional OCT allowed for diagnostic of various pathologies. CP OCT proved to facilitate differential diagnostics of pathologies.

Diagnostic value of standard OCT for recognizing cervical neoplasia has been evaluated: sensitivity is 82%, specificity is 78%, and diagnostics accuracy is 81%. To increase it several approaches have been suggested: application of hyperosmotic agents, cross-polarization tomography, complementary use of fluorescence spectroscopy and OCT, additional computer processing of the OCT-images and optical coherence microscipy.

First experimental results on optical coherence tomography (OCT) imaging of internal structure of plant tissues and in situ OCT monitoring of plant tissue regeneration at different water supply are reported. The OCT images are a map of backscattering coefficient 200 x 200 pixels, 1.5 mm along plant surface and up to 2 mm in depth (by analogy with ultrasound B-scan). Experiments for evaluating OCT capabilities were performed on Tradescantia blossfeldiana Mild . Using OCT device, in vivo images of plant tissues were acquired with a spatial resolution of 15 μm. These OCT images correlate with standard microscopy data from the same tissue regions. Since incident light power at a wavelength of 1.3 μm is as low as 0.5 mW, two-dimensional OCT images can be obtained directly on an intact plant not damaging it. Acquisition time for a 2D image is 1-3 s. OCT enables effective monitoring of fast reactions in plants at different water supply.

A new approach to improving the diagnostic value of optical methods is suggested, which is based on a complementary investigation of different optical parameters of biotissues. The aim of this paper is comparative study of the feasibility of two optical methods - fluorescence spectroscopy and optical coherence tomography - for visualization of borders of neoplastic processes in the uterine cervix and vulva. Fluorescence spectroscopy is based on the detection of biochemical and optical coherence tomography on backscattering properties in norm and pathological changes of tissues. By means of these optical methods changes in biochemical and morphological properties of tissues were investigated. A parallel analysis of these two optical methods and histology from the center of tumors and their optical borders was made. Thirteen female patients with neoplastic changes in uterine cervix and vulva were enrolled in this study. The borders of the tumor determined by optical methods (fluorescence spectroscopy and optical coherence tomography) are coinciding with the biopsy proved ones. In addition, OCT and fluorescence borders of tumor in the uterine cervix and vulva exceeds colposcopically detectable borders, the averaging difference 2 mm. In future optical methods would considerably enhance diagnostic accuracy of conventional methods used in oncogynecology.

In vivo endoscopic optical coherence tomography (OCT) was performed in 154 patients with pathologic lesions, suspicious for high-grade dysplasia, intramucosal or early microinvasive cancer. One group of seven physicians and another of six, familiar with OCT, participated in the blinded recognition of benign and neoplastic conditions in different types of mucous membranes. The result for the OCT sensitivity for malignancy detection in these types of mucosa is 83 - 98%, specificity 71 - 91%. The accuracy was 81 - 87%. Recognition error rate is smaller for high-grade dysplasia and invasive cancer in urinary bladder (3.3% - 1.5%), and higher for the uterine cervix (23% - 11%) and for larynx (45.7% - 3.4%). The kappa coefficient for interobserver agreement was 0.65-0.83.

Summary from only given. Development of computer algorithms of OCT image processing to obtain numerical information on the state of biotissue is an important issue for clinical application of OCT. Optical scattering parameters of the tissue can serve as numerical criteria of the tissue state. In many cases, the morphological structure of tissue may be modeled as a set of uniformly scattering, locally flat layers. When describing light propagation in tissue, scattering in each layer may be characterized by a small number of parameters. Then, a set of scattering parameters of all layers can be used for adequate numerical estimation of the tissue state.

In the present paper, we describe the first complex multifocal noninvasive morphological and functional study that enabled us to define specific qualitative and quantitative features of neonatal skin. A complex morphofunctional examination of 10 infants aging from 1 to 28 days was performed by optical coherence tomography (OCT) device with a flexible probe at the wavelength of 920 nm with longitudinal resolution of 20 μm and transverse resolution of 25 μm with simultaneous measurement of skin functional parameters. The OCT images of neonatal thin skin have organized layered structure with four horizontally oriented layers. Thick skin of newborns has no structure typical for adult skin and no clear transition from the papillary to the cellular dermis. Thus, we show for the first time to our knowledge that neonatal thick skin differs structurally and functionally from adult skin. Structurally, it differs by a loose arrangement of stratum corneum squamae and thinner epidermis and papillary layer of dermis. The functional differences are lower transepidermal water loss, localization-dependent humidity, higher erythema level, and lower pigmentation. The principal structural differences between neonatal and adult skin show that skin structure formation is not completed by the moment of birth.

We study the effect of laser radiation on initially low scattering media such as egg white and crystalline substance. These media become highly scattering under laser irradiation. We perform and discuss three kinds of experiments, which elucidate the time dynamics of scattering of probe radiation. In the experiment of the first kind we investigate the pure photothermal denaturation of tissues under the effect of a Nd:YAG laser at a wavelength of 1440 nm (absorption coefficient in water is 26 cm-1). The theoretical model is derived which enables us to estimate the temperature rise involved. It also allow us to estimate the corresponding kinetics parameters of photodenaturation and characteristics of probe light scattering. In the experiment of the second kind we perform multiple pulse irradiation of tissues by UV harmonics (the fourth and the fifth) of a Nd:YAP laser with the aim to determine the characteristics of pure photochemical modification of materials. In these experiments the fluences were small enough to prevent heating of the materials. The results of the above experiments both of the first and the second kind allow us to estimate the relative contributions of photochemical modification of a tissue and photothermal protein denaturation within the experiments of the third kind, in which we use the mentioned above UV solid state laser harmonics at fluences high enough to produce heating of the materials.

The effect of laser radiation on the regeneration processes in spine disk cartilage has been studied in-vivo. We used rabbits as a model and a Holmium (2.09 micrometer) and an Erbium fiber (1.56 micrometer) lasers for irradiation the discs which were preliminary opened to remove annulus fibrosus and the nucleus pulposus of the intervertebral disc. The irradiated zone has been examined using an optical coherent tomography in one month after the operation and conventional histological technique in two months after the laser operation. It has been shown that laser radiation promotes the growth of the new cartilaginous tissue of fibrous and hyaline types.

We have demonstrated that when using in surgical operations the radiation of YAG:Nd laser with 1.44 μm wavelength exhibits better cutting capabilities as compared to the same laser at 1.32 μm wavelength. The laser scalpel at 1.44 μm also provides adequate hemostasis at non-typical section of parenchymals without blood vessel ligation, however this capability is higher for 1.32 μm radiation. It is possible to combine the advantages of both radiations by repetitive switching the laser between two wavelengths or mixing two simultaneously generate wave in one optical waveguide. Application of several YAG:Nd laser wavelengths with different absorption coefficients in a single operation on the soft tissue allows one to coagulate large-scale blood vessels and to minimize thermal damages of surrounding tissue.

Based on results of clinical examination of about 200 patients we discuss capabilities of the optical coherence tomography (OCT) in monitoring and diagnosing of various pathophysiological processes. Performed in several clinical areas including dermatology, urology, laryngology, gynecology, and dentistry, our study shows the existence of common optical features in manifestation of a pathophysiological process in different organs. In this paper we focus at such universal tomographic optical signs for processes of inflammation, necrosis and tumor growth. We also present data on dynamical OCT monitoring of evolution of pathophysiological processes, both at the stage of disease development and following-up results of different treatments such as drug application, radiation therapy, cryodestruction, and laser vaporization. The discovered peculiarities of OCT images for structural and functional imaging of biological tissues can be put as a basis for application of this method for diagnosing of pathology, guidance of treatment, estimation of its adequacy and assessing of the healing process.

We report on the results of using the optical coherence tomography (OCT) as one of the diagnostic methods at the Department of Gynecology of the Nizhny Novgorod Regional Hospital. An endoscopic OCT device adjusted for gynecological examinations with colposcopy, hysteroscopy and laparoscopy has been developed at the Institute of Applied Physics. It provides clinicians with sharp (up to 15 - 20 micron resolution) images of 1.5 mm thick superficial mucosa layers in the female genital tract, that are recorded at the 0.83 micron wavelength with approximately 1 frame/second rate for a 200 X 200 pixel image. Data obtained during examination of more than 100 patients demonstrate the capability of OCT in estimation of structural alterations in organs, connected with different types of pathologies and functional states of the female genital system. We present first results of OCT application to assess the adequacy of cervical pathologies treatment (electro-, laser surgery and cryotherapy) and to control the healing process.

Pulse-to-pulse kinetics of laser ablation of porcine cornea in vitro by a YAG:Er laser ((lambda) equals 2.94 micrometer) and by fifth harmonic of a YAP:Nd laser ((lambda) equals 216 nm) as well as preablation transformations of cataracted human lens in vitro irradiated by Glass:Er laser ((lambda) equals 1.54 micrometer) are followed by Optical Coherence Tomography (OCT). In the latter case kinetics of tissue swelling is studied. Observation of tissue surface with temporal resolution better than pulse train duration by means of cw probe laser reveals evidences of outburst of 'dynamic' hump.

Optical coherent tomography (OCT) enables one to follow the pulse-to-pulse kinetics of laser interactions with turbid biological tissues. In experiments we investigate the effect of free running mid infrared laser radiation of different wavelengths on a cataract-suffered human lens in vitro. Different regimes of laser ablation and preablation surface transformations are monitored in situ.

We have designed a laser complex which is a combination of a YAG:Er laser operating in the free-running mode, a radiation delivery system based on a chalcogenide fiber with uniquely high damage threshold, and a diagnostic optical coherent tomography (OCT) device for in situ monitoring of surface layers of the tissue under treatment. A flexible chalcogenide glass multimode fiber operates with a pulse energy of 150 mJ at a repetition rate of 3 Hz. Neither degradation nor laser damage were observed after transmission of 104 laser pulses through the fiber delivery instrument. This complex was employed to study the effect of the radiation of a YAG:Er laser and some other mid-IR lasers on a cataract-suffered human lens. The pulse- to-pulse kinetics of the laser tissue treatment process with a scanning depth of several millimeters and spatial resolution of 15 micrometers was investigated.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The progress in creating compact, fast-scanning OCT devices and their use in biomedical research and clinical diagnostics is reported. The results of OCT applications in dermatology, ophthalmology, neurobiology and internal organ studies are presented to demonstrate capabilities and requirements for further development of the method.

Conclusions: We have obtained in-treatment dose distributions and DVHs for each of the different respiratory phases using in-treatment 4D kV CBCT and linac parameters during lung VMAT delivery. Our data showed small variations in dose distributions and DVHs between maximum exhalation and maximum inhalation phases possibly because the tumor size was small and a body frame was used to restrict the patient breathing motion. Dose discrepancies between different phases may be increased for a larger tumor under a free breathing condition. It is further anticipated that deformable registration needs to be implemented to evaluate accumulated dose for an entire treatment delivery.

Damage thresholds of bulk samples and fibers made of high-purity chalcogenide glass of As-S system for YAG:Er laser ((lambda) equals 2.94 micrometers ) are investigated. An accumulation effect is found both in fibers and bulk samples, which reduces stability of repetitive pulse laser operation. Correlation between damage thresholds and heterophase inclusion concentration has been observed experimentally. In samples with impurity concentration less than 104 cm-3 the damage thresholds exceed 1 kJ/cm2 for single shot pulse and approximately twice as low in the repetitive pulse regime. Fibers made of glass samples with minimum concentration of impurities are capable of increasing YAG:Er laser radiation power transmitted through a fiber.

A 3-mum laser-generation delivery instrument that uses chalcogenide fibers with a unique damage threshold and conical radiation input has been developed for medical applications. A new purification and synthesis scheme has been elaborated that yields fibers with a heterophase inclusion content of less than 10(4) cm(-3). In such fibers the damage threshold is 350 J/cm(2) at an average power density of 0.5 kW/cm(2) in a YAG:Er laser operating in the repetitive pulse free-running regime with a pulse duration of 350 ms. 1-3 x 10(4) laser pulses were transmitted at a repetition rate of 3 Hz and an average output power of 1 W under the condition of a 15% decrease in the output power.

The effects of non-ablative infrared (IR) laser treatment of collagenous tissue have been commonly interpreted in terms of collagen denaturation spread over the laser-heated tissue area. In this work, the existing model is refined to account for the recently reported laser-treated tissue heterogeneity and complex collagen degradation pattern using comprehensive optical imaging and calorimetry toolkits. Patella ligament (PL) provided a simple model of type I collagen tissue containing its full structural content from triple-helix molecules to gross architecture. PL ex vivo was subjected to IR laser treatments (laser spot, 1.6 mm) of equal dose, where the tissue temperature reached the collagen denaturation temperature of 60 ± 2°C at the laser spot epicenterin the first regime, and was limited to 67 ± 2°C in the second regime. The collagen network was analyzed versus distance from the epicenter. Experimental characterization of the collagenous tissue at all structural levels included cross-polarization optical coherence tomography, nonlinear optical microscopy, light microscopy/histology, and differential scanning calorimetry. Regressive rearrangement of the PL collagen network was found to spread well outside the laser spot epicenter (>2 mm) and was accompanied by multilevel hierarchical reorganization of collagen. Four zones of distinct optical and morphological properties were identified, all elliptical in shape, and elongated in the direction perpendicular to the PL long axis. Although the collagen transformation into a random-coil molecular structure was occasionally observed, it was mechanical integrity of the supramolecular structures that was primarily compromised. We found that the structural rearrangement of the collagen network related primarily to the heat-induced thermo-mechanical effects rather than molecular unfolding. The current body of evidence supports the notion that the supramolecular collagen structure suffered degradation of various degrees, which gave rise to the observed zonal character of the laser-treated lesion.

Capabilities of optical coherence tomography (OCT) as well as OCT enhanced by tissue clearing using glycerol solution for differential diagnosis of erythematoses, bullous and papulous skin diseases are demonstrated on 118 patients sample. It is shown that high-skilled dermatologists familiar with fundamentals of skin pathomorphology but without previous experience in OCT studies and interpretation of optical features are capable, when using OCT, of distinguishing optical images of various skin diseases to a high diagnostic accuracy (ranging from 76% to 94%) and with good multirater interobserver agreement between different specialists (kappa up to 0.69). Application of glycerol improves contrast and penetration depth of OCT images of skin significantly, thus reliably improving diagnostic validity of the technique and facilitating differential diagnosis of clinically similar dermatoses accompanied by papulous eruption.

To increase the specificity of optical coherence tomography (OCT) a map of depolarizing properties of biological tissues has been acquired by means of crosspolarization OCT. Comparisons between tomograms obtained in orthogonal polarizations have been made.

An experimental setup for combined photoacoustic (PA) and optically mediated ultrasound (US) microscopy is presented. A spherically focused 35 MHz polyvinylidene fluoride (PVDF) ultrasonic detector with a numerical aperture of 0.28, a focal distance of 9 mm, and a bandwidth (−6 dB level) of 24 MHz was used to obtain PA and US data with a 3 mm imaging depth. A fiber-optic system was employed to deliver laser excitation pulses from a tunable laser to the studied medium. A single optical pulse was used to form both PA and US A-scans. The probing US pulses were generated thermoelastically due to absorption of backscattered laser radiation by the metalized surface of a PVDF film.

Contrasting of skin forming elements in optical coherence tomography (OCT) images after application of silica/gold nanoshells or titanium dioxide nanoparticles in solution is discussed. The study is performed both by Monte Carlo simulations and in vivo on animals. The result show that application of both types of nanoparticles produces contrast increase in the OCT images of skin. The increase in OCT signal level originates from the higher backscattering on nanoparticles compared to that on skin forming elements. The increase of contrast in the OCT images originates from the difference in nanoparticles concentration within different skin constituents. These experimental results are confirmed qualitatively by Monte Carlo simulations based on multilayer skin model.