Comparison of Experimental Models for Predicting Laser Tissue Interaction from 3.8-Micron Lasers PDF Download
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Author: Piper C. M. Williams
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Book Description
The purpose of this study was to compare and contrast the effects of single 3.8-micron laser pulses in an in-vitro and in-vivo model of human skin and to demonstrate the efficacy of in-vitro laser tissue interaction models. The minimum exposure required to produce specific, gross morphologic changes from a four microsecond, pulsed skin exposure for both models was determined. Histologic samples of the tissues were compared to ascertain the effectiveness of the in-vitro models. Eighteen artificial skin equivalents, (in-vitro model), were exposed and compared to exposures made on five Yorkshire pigs. Representative biopsies were taken for histologic evaluation from various locations immediately, one hour, and 24 hours following exposure. The pattern of epithelial changes seen following in-vivo exposure of pig skin was similar to the changes previously observed in human skin equivalents, indicating that the artificial skin equivalents are representative in-vitro models for this particular combination of laser parameters.
Author: Piper C. M. Williams
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Book Description
The purpose of this study was to compare and contrast the effects of single 3.8-micron laser pulses in an in-vitro and in-vivo model of human skin and to demonstrate the efficacy of in-vitro laser tissue interaction models. The minimum exposure required to produce specific, gross morphologic changes from a four microsecond, pulsed skin exposure for both models was determined. Histologic samples of the tissues were compared to ascertain the effectiveness of the in-vitro models. Eighteen artificial skin equivalents, (in-vitro model), were exposed and compared to exposures made on five Yorkshire pigs. Representative biopsies were taken for histologic evaluation from various locations immediately, one hour, and 24 hours following exposure. The pattern of epithelial changes seen following in-vivo exposure of pig skin was similar to the changes previously observed in human skin equivalents, indicating that the artificial skin equivalents are representative in-vitro models for this particular combination of laser parameters.
Author: Elharith M. Ahmed
Publisher:
ISBN:
Category : Lasers in medicine
Languages : en
Pages : 178
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Book Description
Since its invention in the early 1960's, the laser has been used as a tool for surgical, therapeutic, and diagnostic purposes. To achieve maximum effectiveness with the greatest margin of safety it is important to understand the mechanisms of light propagation through tissue and how that light affects living cells. Lasers with novel output characteristics for medical and military applications are too often implemented prior to proper evaluation with respect to tissue optical properties and human safety. Therefore, advances in computational models that describe light propagation and the cellular responses to laser exposure, without the use of animal models, are of considerable interest. Here, a physics-based laser-tissue interaction model was developed to predict the spatial and temporal temperature and pressure rise during laser exposure to biological tissues. Our new model also takes into account the dynamic nature of tissue optical properties and their impact on the induced temperature and pressure profiles. The laser-induced retinal damage is attributed to the formation of microbubbles formed around melanosomes in the retinal pigment epithelium (RPE) and the damage mechanism is assumed to be photo-thermal. Selective absorption by melanin creates these bubbles that expand and collapse around melanosomes, destroying cell membranes and killing cells. The Finite Element (FE) approach taken provides suitable ground for modeling localized pigment absorption which leads to a non-uniform temperature distribution within pigmented cells following laser pulse exposure. These hot-spots are sources for localized thermo-elastic stresses which lead to rapid localized expansions that manifest themselves as microbubbles and lead to microcavitations. Model predictions for the interaction of lasers at wavelengths of 193, 694, 532, 590, 1314, 1540, 2000, and 2940 nm with biological tissues were generated and comparisons were made with available experimental data for the retina, cornea or the skin. Good agreement between model and experimental results established the validity of the model.
Author: Jian Jiao
Publisher:
ISBN:
Category : Laser ablation
Languages : en
Pages : 156
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Book Description
In this dissertation, two types of laser-tissue interactions - ultra-short pulsed (USP) laser-tissue thermal interaction and plasma-mediated ablation - are numerically investigated. The thermal interaction is focused on laser hyperthermia skin cancer treatment. A combined ultrafast radiative transfer and bioheat transfer model is developed to predict the temperature distribution in a 2-D axisymmetric skin tissue cylinder subjected to a train of short pulsed irradiations. An appropriate mathematical model to describe the focused laser beam transport is considered. The laser propagation in the tissue is simulated via solving the transient equation of radiative transfer with the Transient Discrete-Ordinates Method. The bioheat transfer equation is calculated by the Alternative Directional Implicit Method. A numerical scheme is introduced to deal with the multi-time-scale heat transfer problems in a three-layer model skin tissue exposed to multiple short laser pulses. Parametric studies including influences of lens diameter, laser focused depth, wavelength and laser power on killing different types of skin tumors are carried out. For the study of USP laser induced plasma-mediated ablation in transparent media, an ionization rate equation is adopted, which consists of the multiphoton and avalanche ionizations, and diffusion and recombination effects. The present 2-D axisymmetric numerical model is validated via extensive comparisons with experimental measurements and other 1-D numerical models available in the literature. The dynamic process of plasma formation for ablation in pure water can be better visualized by the current modeling. To determine plasma-mediated ablation threshold, we propose that a certain number of free electrons are required to trigger the avalanche ionization. Based on this assumption, the ablation thresholds for pulse widths down to the femtoseconds range at wavelength 800 nm are calculated for transparent corneal epithelium. It is found that the critical seed free electron-density decreases as the pulse width increases, obeying a tp-5.65 rule. A complete numerical model with all ionization and loss mechanisms is also employed to elucidate and validate the conditions when avalanche ionization occurs and dominates in the plasma-mediated ablation process. Moreover, the crater sizes ablated in a PDMS by a 900 fs pulsed laser at wavelength 1552 nm are modeled using the present model, and the results match with the existing experimental measurements. The study of plasma-mediated ablation is further extended to turbid media. For ablation in absorbing and highly-scattering biological tissues, combined modeling of ultrafast radiative transfer and plasma formation is needed. We studied plasma-mediated ablation in a model human skin tissue, in which the rate equation is modified with chromophore ionization in addition to the multiphoton and avalanche ionizations. A parametric study on the influences of band gap, critical free-electron density and recombination rate on the prediction of ablation threshold in the model skin tissue is carried out. Moreover, investigation on crater formation is conducted, and the modeled crater sizes are compared with available experimental measurements on corundum and sapphire materials. For ablation in corundum and sapphire, the free electrons are generated via photoionization (multiphoton and tunneling ionizations) and avalanche ionization. The onset of mass ablation in the material is assumed when the local absorbed laser energy is sufficient to cause evaporation. Good agreements between the modeling and experiments are observed.
Author: Irina T. Sorokina
Publisher: Springer Science & Business Media
ISBN: 3540364919
Category : Science
Languages : en
Pages : 600
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Book Description
This collection of authoritative reviews by leading experts provides a broad and instructive introduction to the most advanced techniques for generating coherent light in the mid-infrared region of the spectrum. With a wealth of up-to-date references – also available online.
Author: Yorai Linenberg
Publisher:
ISBN:
Category : Carbon dioxide lasers
Languages : en
Pages : 86
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Book Description
Author: Irina T. Sorokina
Publisher: Springer Science & Business Media
ISBN: 3540006214
Category : Science
Languages : en
Pages : 600
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Book Description
The book describes the most advanced techniques for generating coherent light in the mid-infrared region of the spectrum. These techniques represent diverse areas of photonics and include heterojunction semiconductor lasers, quantum cascade lasers, tunable crystalline lasers, fiber lasers, Raman lasers, and optical parametric laser sources. Offering authoritative reviews by internationally recognized experts, the book provides a wealth of information on the essential principles and methods of the generation of coherent mid-infrared light and on some of its applications. The instructive nature of the book makes it an excellent text for physicists and practicing engineers who want to use mid-infrared laser sources in spectroscopy, medicine, remote sensing and other fields, and for researchers in various disciplines requiring a broad introduction to the subject.
Author: Donald J. Coluzzi
Publisher: Springer
ISBN: 3319519441
Category : Medical
Languages : en
Pages : 397
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Book Description
This book provides information on the basic science and tissue interactions of dental lasers and documents the principal current clinical uses of lasers in every dental discipline. The applications of lasers in restorative dentistry, endodontics, dental implantology, pediatric dentistry, periodontal therapy, and soft tissue surgery are clearly described and illustrated. Information is also provided on laser-assisted multi-tissue management, covering procedures such as crown lengthening, gingival troughing, gingival recontouring, and depigmentation. The closing chapters look forward to the future of lasers in dentistry and the scope for their widespread use in everyday clinical practice.When used in addition to or instead of conventional instrumentation, lasers offer many unique patient benefits. Furthermore, research studies continue to reveal further potential clinical applications, and new laser wavelengths are being explored, developed, and delivered with highly specific power configurations to optimize laser–tissue interaction. This book will bring the reader up to date with the latest advances and will appeal to all with an interest in the application of lasers to the oral soft and/or hard tissues.
Author: D.R. Vij
Publisher: Springer Science & Business Media
ISBN: 1461509297
Category : Technology & Engineering
Languages : en
Pages : 381
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Book Description
A careful review of the literature covering various aspects of applications of lasers in science and technology reveals that lasers are being applied very widely throughout the entire gamut of physical medicine. After surveying the current developments taking place in the field of medical applications of lasers, it was considered appropriate to bring together these efforts of international research scientists and experts into one volume. It is with this aim that the editors have prepared this volume which brings current research and recent developments to the attention of a wide spectrum of readership associated with hospitals, medical institutions and universities world wide, including also the medical instrument industry. Both teachers and students in the medical faculties will especially find this compendium quite useful. This book is comprised of eleven chapters. All of the important medical applications of lasers are featured. The editors have made every effort that individual chapters are self-contained and written by experts. Emphasis has been placed on straight and simple presentation of the subject matter so that even the new entrants into the field will find the book of value.
Author: E. Zeitler
Publisher: Springer Science & Business Media
ISBN: 3642569560
Category : Medical
Languages : en
Pages : 701
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Book Description
A comprehensive account of the use of modern imaging procedures for the diagnosis of arterial and venous diseases. Each imaging modality is separately considered and applications in individual diseases are then explained with the aid of excellent illustrations. In addition, vascular interventions such as balloon angioplasty, local thrombolysis, and stent implantation are discussed and appraised, with special attention devoted to the problem of radiation burden for patients. The authors are all recognized experts in angiology, phlebology, and interventional radiology.
Author:
Publisher:
ISBN:
Category : Medicine
Languages : en
Pages : 1328
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Book Description
