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Frequency doubling and tripling of ultrashort laser pulses in biological tissues

Description: Structural proteins such as collagen and elastin are known to generate second harmonic at high laser intensities. Second and third harmonic generations (SHG, THG) of 0.4 ps Ti-Sapphire laser radiation at 800 nm were observed in various biological tissues. Dependence of SHG on laser pulse energy and pulse width was investigated. Reflected second harmonic yield was measured for animal tissue <i>in vitro</i> and human skin <i>in vivo</i>. The yield varies about a factor of 20 for various areas of the skin while the scattered laser radiation (diffuse reflectance) varies only by a factor of 2. In some cases the THG efficiency was comparable to the SHG. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed.
Date: July 24, 1998
Creator: Da Silva, L. B.; Eichler, J.; Joslin, E. J. & Kim, B.-M.
Partner: UNT Libraries Government Documents Department

Biospecimen Reporting for Improved Study Quality

Description: Human biospecimens are subjected to collection, processing, and storage that can significantly alter their molecular composition and consistency. These biospecimen preanalytical factors, in turn, influence experimental outcomes and the ability to reproduce scientific results. Currently, the extent and type of information specific to the biospecimen preanalytical conditions reported in scientific publications and regulatory submissions varies widely. To improve the quality of research that uses human tissues, it is crucial that information on the handling of biospecimens be reported in a thorough, accurate, and standardized manner. The Biospecimen Reporting for Improved Study Quality (BRISQ) recommendations outlined herein are intended to apply to any study in which human biospecimens are used. The purpose of reporting these details is to supply others, from researchers to regulators, with more consistent and standardized information to better evaluate, interpret, compare, and reproduce the experimental results. The BRISQ guidelines are proposed as an important and timely resource tool to strengthen communication and publications on biospecimen-related research and to help reassure patient contributors and the advocacy community that their contributions are valued and respected.
Date: December 27, 2010
Creator: Moore, Ph.D., Helen M.; Kelly, Ph.D., Andrea B.; Jewell, Ph.D., Scott D.; McShane, Ph.D., Lisa M.; Clark, M.D., Douglas P.; Greenspan, M.D., Renata et al.
Partner: UNT Libraries Government Documents Department

Biospecimen Reporting for Improved Study Quality (BRISQ)

Description: Human biospecimens are subject to a number of different collection, processing, and storage factors that can significantly alter their molecular composition and consistency. These biospecimen preanalytical factors, in turn, influence experimental outcomes and the ability to reproduce scientific results. Currently, the extent and type of information specific to the biospecimen preanalytical conditions reported in scientific publications and regulatory submissions varies widely. To improve the quality of research utilizing human tissues it is critical that information regarding the handling of biospecimens be reported in a thorough, accurate, and standardized manner. The Biospecimen Reporting for Improved Study Quality (BRISQ) recommendations outlined herein are intended to apply to any study in which human biospecimens are used. The purpose of reporting these details is to supply others, from researchers to regulators, with more consistent and standardized information to better evaluate, interpret, compare, and reproduce the experimental results. The BRISQ guidelines are proposed as an important and timely resource tool to strengthen communication and publications around biospecimen-related research and help reassure patient contributors and the advocacy community that the contributions are valued and respected.
Date: April 26, 2011
Creator: Moore, Ph.D., Helen M.; Kelly Ph.D., Andrea; Jewell Ph.D., Scott D.; McShane Ph.D., Lisa M.; Clark M.D., Douglas P.; Greenspan M.D., Renata et al.
Partner: UNT Libraries Government Documents Department

Comparison of soft and hard tissue ablation with sub-ps and ns pulse lasers

Description: Tissue ablation with ultrashort laser pulses offers several unique advantages. The nonlinear energy deposition is insensitive to tissue type, allowing this tool to be used for soft and hard tissue ablation. The localized energy deposition lead to precise ablation depth and minimal collateral damage. This paper reports on efforts to study and demonstrate tissue ablation using an ultrashort pulse laser. Ablation efficiency and extent of collateral damage for 0.3 ps and 1000 ps duration laser pulses are compared. Temperature measurements of the rear surface of a tooth section is also presented.
Date: May 1, 1996
Creator: Da Silva, L.B.; Stuart, B.C.; Celliers, P.M.; Feit, M.D.; Glinsky, M.E.; Heredia, N.J. et al.
Partner: UNT Libraries Government Documents Department

Laser welding and collagen crosslinks

Description: Strength and stability of laser-welded tissue may be influenced, in part, by effects of laser exposure on collagen crosslinking. We therefore studied effects of diode laser exposure (805 nm, 1-8 watts, 30 seconds) + indocyanine green dye (ICG) on calf tail tendon collagen crosslinks. Effect of ICG dye alone on crosslink content prior to laser exposure was investigated; unexpectedly, we found that ICG-treated tissue had significantly increased DHLNL and OHP, but not HLNL. Laser exposure after ICG application reduced elevated DHLNL and OHP crosslink content down to their native levels. The monohydroxylated crosslink HLNL was inversely correlated with laser output (p<0.01 by linear regression analysis). DHLNL content was highly correlated with content of its maturational product, OHP, suggesting that precursor-product relations are maintained. We conclude that: (1)ICG alone induces DHLNL and OHP crosslink formation; (2)subsequent laser exposure reduces the ICG-induced crosslinks down to native levels; (3)excessive diode laser exposure destroys normally occurring HLNL crosslinks.
Date: February 20, 1997
Creator: Reiser, K.M.; Last, J.A.; Small, W. IV; Maitland, D.J.; Heredia, N.J.; Da Silva, L.B. et al.
Partner: UNT Libraries Government Documents Department

High definition ultrasound imaging for battlefield medical applications

Description: A team has developed an improved resolution ultrasound system for low cost diagnostics. This paper describes the development of an ultrasound based imaging system capable of generating 3D images showing surface and subsurface tissue and bone structures. We include results of a comparative study between images obtained from X-Ray Computed Tomography (CT) and ultrasound. We found that the quality of ultrasound images compares favorably with those from CT. Volumetric and surface data extracted from these images were within 7% of the range between ultrasound and CT scans. We also include images of porcine abdominal scans from two different sets of animal trials.
Date: June 23, 1996
Creator: Kwok, K.S.; Morimoto, A.K.; Kozlowski, D.M.; Krumm, J.C.; Dickey, F.M.; Rogers, B et al.
Partner: UNT Libraries Government Documents Department

Extended Rayleigh model of bubble evolution with material strength compared to detailed dynamic simulations

Description: The validity of an extended Rayleigh model for laser generated bubbles in soft tissue is examined. This model includes surface tension, viscosity, a realistic water equation of state, material strength and failure, stress wave emission, and linear growth of interface instabilities. It is compared to dynamic simulations using LATIS, which include stress wave propagation, water equation of state, material strength and failure, and viscosity. The model and the simulations are compared using 1-D spherical geometry with bubble in center and a 2-D cylindrical geometry of a laser fiber in water with a bubble formed at the end of the fiber. The model executes over 300x faster on computer than the dynamic simulations.
Date: March 4, 1997
Creator: Glinsky, M.E.; Amendt, P.A.; Bailey, D.S.; London, R.A.; Rubenchik, A.M. & Strauss, M.
Partner: UNT Libraries Government Documents Department

Plasma luminescence feedback control system for precise ultrashort pulse laser tissue ablation

Description: Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using ultrashort pulse laser (USPL). Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.
Date: January 1, 1998
Creator: Kim, B.M.; Feit, M.D.; Rubenchick, A.M.; Gold, D.M.; Darrown, C.B. & Da Silva, L.B.
Partner: UNT Libraries Government Documents Department

LATIS modeling of laser induced midplane and backplane spallation

Description: The computer code LATIS is used to simulate midplane and backplane spallation resulting from short pulsed laser absorption. A 1-D planar geometry is simulated with an exponential laser absorption profile. The laser pulse length is assumed to be much shorter than the sound transit time across the laser absorption length. The boundary conditions are a fixed front plane and free backplane (backplane spall) and a free front plane and a fixed midplane (midplane spall). The NBS/NRC equation of state for water is used with a self- consistent yet empirical material strength and failure model. The failure model includes the effects of void nucleation, growth and coalescence. Definite signatures of the nucleation and coalescence thresholds are found in the back surface motion for backplane spallation.
Date: March 5, 1997
Creator: Glinksky, M.E.; Bailey, D.S. & London, R.A.
Partner: UNT Libraries Government Documents Department

Thermal and molecular investigation of laser tissue welding

Description: Despite the growing number of successful animal and human trials, the exact mechanisms of laser tissue welding remain unknown. Furthermore, the effects of laser heating on tissue on the molecular scale are not fully understood. To address these issues, a multi-front attack oil both extrinsic (solder/patch mediated) and intrinsic (laser only) tissue welding was launched using two-color infrared thermometry, computer modeling, weld strength assessment, biochemical assays, and vibrational spectroscopy. The coupling of experimentally measured surface temperatures with the predictive numerical simulations provided insight into the sub-surface dynamics of the laser tissue welding process. Quantification of the acute strength of the welds following the welding procedure enabled comparison among trials during an experiment, with previous experiments, and with other studies in the literature. The acute weld integrity also provided an indication of tile probability of long-term success. Molecular effects induced In the tissue by laser irradiation were investigated by measuring tile concentrations of specific collagen covalent crosslinks and characterizing the Fourier-Transform infrared (FTIR) spectra before and after the laser exposure.
Date: June 1, 1998
Creator: Small, W., IV
Partner: UNT Libraries Government Documents Department

Photoacoustic Measurements in Brain Tissue

Description: In this work, we develop and evaluate the photoacoustic technique for recording spectra of white and gray mammalian brain tissues. In addition to the experimental work, we also discuss the geometric aspects of photoacoustic signal generation using collimated light. Spectra constructed from the peak-to-peak amplitude of the photoacoustic waveforms indicate differences in the two tissue types at wavelengths between 620 and 695 nm. The potential of the technique for non-invasive diagnosis is discussed.
Date: September 19, 1999
Creator: Kasili, P.M.; Mobley, J. & Vo-Dinh, T.
Partner: UNT Libraries Government Documents Department

APPLICATION OF PRINCIPAL COMPONENT ANALYSIS AND BAYESIAN DECOMPOSITION TO RELAXOGRAPHIC IMAGING

Description: Recent developments in high field imaging have made possible the acquisition of high quality, low noise relaxographic data in reasonable imaging times. The datasets comprise a huge amount of information (&gt;&gt;1 million points) which makes rigorous analysis daunting. Here, the authors present results demonstrating that Principal Component Analysis (PCA) and Bayesian Decomposition (BD) provide powerful methods for relaxographic analysis of T{sub 1} recovery curves and editing of tissue type in resulting images.
Date: May 22, 1999
Creator: OCHS,M.F.; STOYANOVA,R.S.; BROWN,T.R.; ROONEY,W.D.; LI,X.; LEE,J.H. et al.
Partner: UNT Libraries Government Documents Department

Scaling model for laser-produced bubbles in soft tissue

Description: The generation of vapor-driven bubbles is common in many emerging laser-medical therapies involving soft tissues. To successfully apply such bubbles to processes such as tissue break-up and removal, it is critical to understand their physical characteristics. To complement previous experimental and computational studies, an analytic mathematical model for bubble creation and evolution is presented. In this model, the bubble is assumed to be spherically symmetric, and the laser pulse length is taken to be either very short or very long compared to the bubble expansion timescale. The model is based on the Rayleigh cavitation bubble model. In this description, the exterior medium is assumed to be an infinite incompressible fluid, while the bubble interior consists of a mixed liquid-gas medium which is initially heated by the laser. The heated interior provides the driving pressure which expands the bubble. The interior region is assumed to be adiabatic and is described by the standard water equation-of-state, available in either tabular, or analytic forms. Specifically, we use adiabats from the equation-of-state to describe the evolution of the interior pressure with bubble volume. Analytic scaling laws are presented for the maximum size, the duration, and the energy of bubbles as functions of the laser energy and initially heated volume. Of particular interest, is the efficiency of converting laser energy into bubble motion.
Date: March 12, 1998
Creator: London, R. A., LLNL
Partner: UNT Libraries Government Documents Department

Report of the First Community Consultation on the Responsible Collection and Use of Samples for Genetic Research, September 25-26, 2000

Description: The First Community Consultation on the Responsible Collection and Use of Samples for Genetic Research was held in Bethesda, Maryland, on September 25-26, 2000. The consultation was convened by the National Institute of General Medical Sciences (NIGMS) of the National Institutes of Health (NIH). Approximately 120 individuals participated in the consultation, half from a broad range of communities and populations, and half from government. The participants shared their views and concerns about population- and community-based genetic research, expanding the focus of the meeting from the collection and use of blood or other tissue samples for genetic research to broader issues and concerns about the conduct of genetic research in general with populations and communities.
Date: May 22, 2002
Creator: Greenberg, Judith H.
Partner: UNT Libraries Government Documents Department

Predicting Tissue-Specific Enhancers in the Human Genome

Description: Determining how transcriptional regulatory signals areencoded in vertebrate genomes is essential for understanding the originsof multi-cellular complexity; yet the genetic code of vertebrate generegulation remains poorly understood. In an attempt to elucidate thiscode, we synergistically combined genome-wide gene expression profiling,vertebrate genome comparisons, and transcription factor binding siteanalysis to define sequence signatures characteristic of candidatetissue-specific enhancers in the human genome. We applied this strategyto microarray-based gene expression profiles from 79 human tissues andidentified 7,187 candidate enhancers that defined their flanking geneexpression, the majority of which were located outside of knownpromoters. We cross-validated this method for its ability to de novopredict tissue-specific gene expression and confirmed its reliability in57 of the 79 available human tissues, with an average precision inenhancer recognition ranging from 32 percent to 63 percent, and asensitivity of 47 percent. We used the sequence signatures identified bythis approach to assign tissue-specific predictions to ~;328,000human-mouse conserved noncoding elements in the human genome. Byoverlapping these genome-wide predictions with a large in vivo dataset ofenhancers validated in transgenic mice, we confirmed our results with a28 percent sensitivity and 50 percent precision. These results indicatethe power of combining complementary genomic datasets as an initialcomputational foray into the global view of tissue-specific generegulation in vertebrates.
Date: July 1, 2006
Creator: Pennacchio, Len A.; Loots, Gabriela G.; Nobrega, Marcelo A. & Ovcharenko, Ivan
Partner: UNT Libraries Government Documents Department

Imaging of Tissue Micro-Structures using a Multi-Modal Microscope Design

Description: We investigate a microscope design that offers high signal sensitivity and hyperspectral imaging capabilities and allows for implementation of various optical imaging approaches while its operational complexity is minimized. This system utilizes long working distance microscope objectives that enable for off-axis illumination of the tissue thereby allowing for excitation at any optical wavelength and nearly eliminating spectral noise from the optical elements. Preliminary studies using human and animal tissues demonstrate the feasibility of this approach for real-time imaging of intact tissue microstructures using autofluorescence and light scattering imaging methods.
Date: August 12, 2005
Creator: Demos, S G; Lieber, C A; Lin, B & Ramsamooj, R
Partner: UNT Libraries Government Documents Department

A Comprehensive Catalog of Human KRAB-associated Zinc Finger Genes: Insights into the Evolutionary History of a Large Family of Transcriptional Repressors

Description: Krueppel-type zinc finger (ZNF) motifs are prevalent components of transcription factor proteins in all eukaryotic species. In mammals, most ZNF proteins comprise a single class of transcriptional repressors in which a chromatin interaction domain, called the Krueppel-associated box (KRAB) is attached to a tandem array of DNA-binding zinc-finger motifs. KRAB-ZNF loci are specific to tetrapod vertebrates, but have expanded dramatically in numbers through repeated rounds of segmental duplication to create a gene family with hundreds of members in mammals. To define the full repertoire of human KRAB-ZNF proteins, we searched the human genome for key motifs and used them to construct and manually curate gene models. The resulting KRAB-ZNF gene catalog includes 326 known genes, 243 of which were structurally corrected by manual annotation, and 97 novel KRAB-ZNF genes; this single family therefore comprises 20% of all predicted human transcription factor genes. Many of the genes are alternatively spliced, yielding a total of 743 distinct predicted proteins. Although many human KRAB-ZNF genes are conserved in mammals, at least 136 and potentially more than 200 genes of this type are primate-specific including many recent segmental duplicates. KRAB-ZNF genes are active in a wide variety of human tissues suggesting roles in many key biological processes, but most member genes remain completely uncharacterized. Because of their sheer numbers, wide-ranging tissue-specific expression patterns, and remarkable evolutionary divergence we predict that KRAB-ZNF transcription factors have played critical roles in crafting many aspects of human biology, including both deeply conserved and primate-specific traits.
Date: September 30, 2005
Creator: Huntley, S; Baggott, D M; Hamilton, A T; Tran-Gyamfi, M; Yang, S; Kim, J et al.
Partner: UNT Libraries Government Documents Department

Computational methods for describing the laser-induced mechanical response of tissue

Description: Detailed computational modeling of laser surgery requires treatment of the photoablation of human tissue by high intensity pulses of laser light and the subsequent thermomechanical response of the tissue. Three distinct physical regimes must be considered to accomplish this: (1) the immediate absorption of the laser pulse by the tissue and following tissue ablation, which is dependent upon tissue light absorption characteristics; (2) the near field thermal and mechanical response of the tissue to this laser pulse, and (3) the potential far field (and longer time) mechanical response of witness tissue. Both (2) and (3) are dependent upon accurate constitutive descriptions of the tissue. We will briefly review tissue absorptivity and mechanical behavior, with an emphasis on dynamic loads characteristic of the photoablation process. In this paper our focus will center on the requirements of numerical modeling and the uncertainties of mechanical tissue behavior under photoablation. We will also discuss potential contributions that computational simulations can make in the design of surgical protocols which utilize lasers, for example, in assessing the potential for collateral mechanical damage by laser pulses.
Date: February 1, 1994
Creator: Trucano, T.; McGlaun, J. M. & Farnsworth, A.
Partner: UNT Libraries Government Documents Department

Theoretical and experimental investigations of elastic scattering spectroscopy as a potential diagnostic for tissue pathologies

Description: The spectral distribution of the diffuse reflectance of five sizes of polystyrene microspheres has been measured with an elastic scatter spectrometer designed for optical biopsy of living tissue. The microsphere sizes are representative of the suspected scattering centers in living tissue. The experiment data are discussed and interpreted in the framework of Mie scattering theory and Monte-Carlo transport analysis. Present results support the assertion that Mie theory is necessary to describe the spectral features of elastic scatter spectroscopy in tissue.
Date: April 1, 1994
Creator: Boyer, J.; Mourant, J. R. & Bigio, I. J.
Partner: UNT Libraries Government Documents Department