Mechanisms of Laser-Tissue Interaction: Optical Properties of Tissue

Today, lasers are widely used in biology and medicine, and the majority of healthcenters and hospitals utilize modern laser systems for diagnosis and therapy applications.Researchers have introduced different medical applications for different lasers used in surgeries and other medical treatments. Medical lasers can be categorized in both diagnosis and therapy branches. Main difference between diagnosis and therapy applications is the type of laser-tissue interactions. In diagnosis, one tries to arrange a noninvasive method to study the normal behavior of tissue without any damage or clear effect on tissue. But in therapy, such as surgery, a surgeon uses laser as a knife or for affecting a specific region. So, the medical laser applications are defined by the interaction type between laser light and tissues. The knowledge of laser-tissue  interaction can help doctors or surgeons to select the optimal laser systems and modify the type of their therapy. Therefore, we seek to review the mechanisms of laser- tissue interaction. In this paper, the optical properties of biological tissue such as absorption, scattering, penetration and fluorescence are reviewed. Also, the effects of these properties on laser penetration in tissue have been explained

Blind localization of heating in neural tissues induced by a train of the infrared pulse laser

Introduction: Recently, infrared lasers (wavelengths larger than 1100 nm) have been applied to stimulate neural tissues. Infrared neural stimulation (INS) has some advantages over conventional electric stimulation, including contact-free delivery, spatial precision, and lack of stimulation artifacts. In this study and based on a photothermal mechanism, we applied the heat diffusion equation to study temperature variation of a biological phantom during INS. In addition, the impact of laser parameters on spatially localized heating induced by two different infrared wavelengths were studied.Method: We studied the localization of INS inside a phantom similar to cortical neural tissue. First, we analytically solved the heat diffusion equation to study the distribution of temperature inside this phantom. Then, the accuracy of analytical results was verified by heating the phantom using amplitude-modulated infrared lasers (lambda= 1450 and 1500 nm, the energy between 2 and 5 mJ and pulse duration up to 20 ms). The laser light was directed to sample by a multimode optical fiber (NA=0.22, Core size= 200 microns). Finally, the impacts of laser properties on the spatial resolution of infrared heating were discerned.Result: In order to verify analytical results, we measured the maximum temperatures of the phantom during illumination of lasers and compared them with analytical results. The analytical results were in agreement with the experimental results. The effects of laser beam properties such as pulse duration, energy and repetition rate frequency on the spatial resolution were investigated. The results indicated that the spatial resolution of INS can be smaller than one millimeter.Conclusion: Here, the influences of laser properties on the localization of INS inside a biological phantom were studied. These results can be applied to improve the spatial selectivity of the peripheral nerve interface. 

Mechanisms of Laser-Tissue Interaction: II. Tissue Thermal Properties

Laser-tissue interaction is of great interest due to its significant application in biomedical optics in both diagnostic and treatment purposes. Major aspects of the laser-tissue interaction which has to be considered in biomedical studies are the thermal properties of the tissue and the thermal changes caused by the interaction of light and tissue. In this review paper the effects of light on the tissue at different temperatures are discussed. Then, due to the noticeable importance of studying the heat transfer quantitatively, the equations governing this phenomenon are presented. Finally a method of medical diagnosis called thermography and some of its applications are explained

The relationship between postural abnormalities and quality of life and mental health of girl students of Arak Farhangian University

زمینه و هدف: وجود ناهنجاری های وضعیتی، تأثیر نامطلوبی بر درک و تصور بدنی به خصوص در افراد جوان دارد. ناهنجاری ها اگر به موقع شناسایی و درمان نشوند ممکن است آثار نامطلوبی بر عملکرد فیزیولوژیک بدن داشته باشند. هدف این پژوهش، بررسی ناهنجاری های عضلانی اسکلتی ستون فقرات دانشجویان دختر پردیس دانشگاه فرهنگیان اراک و ارتباط آن با سلامت روان و کیفیت زندگی می باشد. روش بررسی: پژوهش حاضر از نوع توصیفی مقطعی و همبستگی محسوب می شود. در این مطالعه، نمونه ای 120 نفری از دانشجویان به روش تصادفی خوشه ای، انتخاب گردید. به منظور گردآوری داده های مربوط به ناهنجاری های عضلانی اسکلتی، از صفحه شطرنجی و آزمون سازمانی نیویورک و خط مرجع شاقولی و خط کش منعطف و جهت جمع آوری اطلاعات مربوط به کیفیت زندگی و سلامت روان از دو پرسشنامه ی معتبر GHQ و پرسشنامه سلامت روان گلد برگ استفاده شد. یافته ها: نتایج حاصل از تحلیل داده ها نشان داد که حدود 91 دانشجو معلمان دارای انواع مختلفی از ناهنجاری های عضلانی اسکلتی بودند و تنها بین کیفیت زندگی دانشجویان با ناهنجاری های عضلانی اسکلتی رابطه معکوس و معنی داری وجود دارد (05/0>P). نتیجه گیری: ناهنجاری های عضلانی اسکلتی، نه تنها در سلامت جسمی و کارکرد اندام ها موثر است، بلکه بر فاکتورهای روان شناسی نیز تأثیرگذار خواهد بود. بنابراین می توان نتیجه گرفت که شناسایی به موقع آن ها تأثیر به سزایی در سلامت جسمی و روحی افراد جامعه خواهد داشت

The Temporal Confounding Effects of Extra-cerebral Contamination Factors on the Hemodynamic Signal Measured by Functional Near-Infrared Spectroscopy

Introduction: Functional near-infrared spectroscopy (fNIRS) has been broadly applied for optical brain imaging. This method is hemodynamic-based functional brain imaging relying on the measurement of the neurovascular coupling to detect changes in cerebral neuronal activities. The extra-cerebral hemodynamic changes are important contaminating factors in fNIRS measurements. This error signal can be misinterpreted as cerebral activities during fNIRS studies. Recently, it was assumed that temporal changes in deoxygenated hemoglobin concentration [HHb] was hardly affected by superficial blood flow, and it was proposed that the activation maps could be determined from [HHb] at large source-detector separation.Methods: In the current study, we measured the temporal changes in [HHb] using a continues-wave fNIRS device at large source-detector separation, while superficial blood flow was stimulated by infrared lasers. A mesh-based Monte Carlo code was applied to estimate fNIRS sensitivity to superficial hemodynamic changes in a realistic 3D MRI-based brain phantom.Results: First, we simulated photon migration in a four-layered human-head slab model to calculate PPLs and fNIRS sensitivity. Then, the localization of the infrared laser inside a realistic brain model was studied using the Monte Carlo method. Finally, the changes in [HHb] over the prefrontal cortex of six adult males were measured by fNIRS at a source-detector separation of 3 cm. The results demonstrated that the relation between fNIRS sensitivity and an increase in S-D separation was nonlinear and a correlation between shallow and deep signals was observed.Conclusion: The presented results demonstrated that the temporal changes in the superficial blood flow could strongly affect HHb measurement at large source-detector separation. Hence, the cerebral activity map extracted from the [HHb] signal was mainly contaminated by superficial blood flow

GREEN SYNTHESIS OF SILVER NANOPARTICLES USING THE LEAF EXTRACT OF PUTRANJIVA ROXBURGHII WALL. AND THEIR ANTIMICROBIAL ACTIVITY.

 Objective: This study deals with the synthesis of silver nanoparticles (AgNP's) from the extract of the leaves of the plant Putranjiva roxburghii wall.Using biological method, i.e., green synthesis.Methods: The extract from the leaves acts as a reducing and stabilizing agent for the AgNP's. Further characterization was done using varioustechniques like ultraviolet (UV)-visible spectrophotometry, which shows surface plasmon resonance, Fourier transform infra-red spectroscopyanalysis shows formation of various bonds, scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis depictsthe distribution and average size of nanoparticles. The antimicrobial activity was also checked against various bacteria and fungi using minimuminhibitory concentration and well diffusion assay.Result: UV analysis shows strong plasmon resonance between 420 and 480 nm SEM analysis shows the distribution of synthesized nanoparticles,whereas TEM analysis shows the average particle size to be near about 5 nm and well diffusion assay proved that these nanoparticles are effectiveagainst different microorganisms.Conclusion: P. roxburghii wall. shows strong potential for the reduction of silver from Ag+ to Ag0 and nanoparticles so formed are strongly activeagainst various microorganism.Keywords: Putranjiva roxburghii, Fourier transform infra-red, Scanning electron microscope, Transmission electron microscope

Diffuse Optical Tomography: Image Reconstruction and Verification

Introduction: In this study, we intend to use diffuse optical Tomography (DOT) as a noninvasive, safe and low cost technique that can be considered as a functional imaging method and mention the importance of image reconstruction in accuracy and procession of image. One of the most important and fastest methods in image reconstruction is the boundary element method (BEM). This method is introduced and employed in our works.Method: Generally, to image a biological tissue we must obtain its optical properties. In order to reach this goal we benefit from diffusion equation because tissue is highly scattering medium. Diffusion equation is solved by boundary element equation (BEM) in our research. First, we assume a double layer phantom with different scattering and absorption coefficients to simulate and verify precession and accuracy of image reconstruction by BEM. Light absorption can be affected by volume fraction of blood in skin. For a specific skin species the volume fraction is calculated and then the results are compared with the reconstructed values obtained by BEM. Since the depth of tissue is important in light absorption a two layer phantom with known values is made and the depths of layers are reconstructed by BEM then they are compared with the expected values. A homogenous phantom with known scattering and absorption coefficients was made and then these coefficients were reconstructed by BEM. Finally, an inhomogeneous phantom (phantom with defect) whose defect was in a known position was made and the absorption and scattering coefficients were reconstructed and compared with real values.Results: Comparison between real or simulated values and reconstructed values of scattering and absorption coefficients, volume fraction of blood and thickness of phantom layers by BEM shows maximum errors of 24%, 7% and 35%, respectively.Conclusion: Comparison between BEM data and real or simulated values shows an acceptable agreement. Consequently, we can rely on BEM as a beneficial method in diffuse optical tomography image reconstruction

A Low-Cost Method for Optical Tomography

INTRODUCTION: In this study, arrangement of a low-cost optical tomography device compared to other methods such as frequency domain diffuse tomography or time domain diffuse tomography is reported. This low-cost diffuse optical imaging technique is based on the detection of light after propagation in tissue. These detected signals are applied to predict the location of in-homogeneities inside phantoms. The device is assessed for phantoms representing homogenous healthy breast tissues as well as those representing healthy breast tissues with a lesion inside.METHODS: A diode laser at 780nm and 50 mW is used as the light source. The scattered light is then collected from the outer surface of the phantom by a detector. Both laser and detector are fiber coupled. The detector fiber may turn around the phantom to collect light scattered at different angles. Phantoms made of intralipid as the scattering medium and ink as the absorbing medium are used as samples. Light is collected after propagation in the phantoms and the capability of the device in collecting data and detecting lesions inside the phantoms is assessed. The fact that the detection fiber orbits around the sample and detects light from various angles has eliminated the need to use several detectors and optical fibers. The results obtained from experiments are compared with the results obtained from a finite element method (FEM) solution of diffusion equation in cylindrical geometry written in FORTRAN.RESULTS: The graphs obtained experimentally and numerically are in good accordance with each other. The device has been able to detect lesions up to 13 mm inside the biological phantom.CONCLUSION: The data achieved by the optical tomography device is compared with the data achieved via a FEM code written in FORTRAN. The results indicate that the presented device is capable of providing the correct pattern of diffusely backscattered and transmitted light. The data achieved from the device is in excellent correlation with the numerical solution of the diffusion equation. Therefore, results indicate the applicability of the reported device. This device may be used as a base for an optical imaging. It is also capable of detecting lesions inside the phantom

Determinants of Reproductive Tract Infection among married women in rural and peri-urban areas of Aligarh: A cross sectional Study

Background: Reproductive Tract Infections (RTI) have a direct impact on reproductive and child health through infertility, cancers, and pregnancy complications, and they have an indirect impact through their role in facilitating the sexual transmission of the human immunodeficiency virus. Objectives: To find the prevalence and determinants of RTI/STI among married women of reproductive age group in rural and peri-urban areas of Aligarh. Methods: The data were collected by using a pretested, semi-structured with both open and closed-ended questionnaire from 500 married women of reproductive age group. The collected data were analyzed using IBM SPSS 20.0 Proportion, frequencies, ?2, and logistic regression were used to interpret the data. Results: Prevalence of RTI/STI symptoms was found to (42.8%) in rural areas and 37.6 % in peri-urban areas. Strong association was found in study subjects having lower educational status, who were not using any contraceptive method, not following good menstrual hygiene, early marriage age had husband history of RTI/STI, had a history of abortion, had a history of violence, and increased parity. Conclusions: Prevalence of symptoms found to be associated with these females having low educational status, early age of marriage, high parity, partner history of reproductive Tract Infections, history of violence etc. So, there should be more focus on improvement in these factors to reduce the prevalence