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Duncan D.,Portland State University | Fischer D.,NASA | Daneshbod M.,University of New Mexico | Dayton A.,Oregon Medical Laser Center | Prahl S.,Oregon Medical Laser Center
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2010

The propagation of light through complex structures, such as biological tissue, is a poorly understood phenomenon. Typically the tissue is modeled as an effective medium, and Monte Carlo techniques are used to solve the radiative transport equation. In such an approach the medium is characterized in terms of a limited number of physical scatter and absorption parameters, but is otherwise considered homogeneous. For exploration of propagation phenomena such as spatial coherence, however, a physical model of the tissue medium that allows multiscale structure is required. We present a particularly simple means of establishing such a multiscale tissue characterization based on measurements using a differential interference contrast (DIC) microscope. This characterization is in terms of spatially resolved maps of the (polar and azimuthal) angular ray deviations. With such data, tissues can be characterized in terms of their first and second order scatter properties. We discuss a simple means of calibrating a DIC microscope, the measurement procedure and quantitative interpretation of the ensuing data. These characterizations are in terms of the scatter phase function and the spatial power spectral density. © 2010 Copyright SPIE - The International Society for Optical Engineering.


Duncan D.,Portland State University | Fischer D.,NASA | Daneshbod M.,University of New Mexico | Prahl S.,Oregon Medical Laser Center
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2010

Analysis of the first and second order statistical properties of light is a powerful means of establishing the properties of a medium with which the light has interacted. In turn, the first and second order statistical properties of the medium dictate the manner in which light interacts with the medium. The former is the inverse problem and the latter is the forward problem. Towards an understanding of the propagation of light through complex structures, such as biological tissue, one might choose to explore either the inverse or the forward problem. Fundamental to the problem, however, is a physical parametric model that relates the two halves; a model that allows prediction of the measured effect or prediction of the parameters based on measurements. This is the objective of our study. As a means of characterizing the first and second order properties of tissue, we discuss measurements with differential interference contrast microscopy using a phasestepping approach. First and second order properties are characterized respectively in terms of scatter phase functions and spatial power spectral densities. Results are shown for representative tissue. © 2010 Copyright SPIE - The International Society for Optical Engineering.


Duncan D.D.,Portland State University | Fischer D.G.,NASA | Dayton A.,Oregon Medical Laser Center | Prahl S.A.,Oregon Medical Laser Center
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2011

We present a method of using an unmodified differential interference contrast microscope to acquire quantitative information on scatter and absorption of thin tissue samples. A simple calibration process is discussed that uses a standard optical wedge. Subsequently, we present a phase-stepping procedure for acquiring phase gradient information exclusive of absorption effects. The procedure results in two-dimensional maps of the local angular (polar and azimuthal) ray deviation. We demonstrate the calibration process, discuss details of the phase-stepping algorithm, and present representative results for a porcine skin sample. © 2011 Optical Society of America.


Dayton A.,Oregon Health And Science University | Dayton A.,Oregon Medical Laser Center | Soot L.,The Oregon Clinic Westside Surgical Specialists | Wolf R.,The Oregon Clinic Gastrointestinal and Minimally Invasive Surgery Division | And 3 more authors.
Journal of Biophotonics | Year: 2011

Despite numerous advances, lumpectomy remains a challenging procedure. We report on the early use of light-guided lumpectomy. Eight patients with non-palpable breast cancer undergoing lumpectomy for biopsy-proven and radiographically identifiable cancer were enrolled in the study. An optical wire was designed that incorporated a standard hook-wire with an optical fiber. The optical wire was placed in the same manner as a standard hook-wire. During light-guided lumpectomy, an eye-safe laser illuminated the optical wire and created a sphere of light surrounding the cancer. The light was visible at the beginning of each surgery and facilitated approaching the cancer without using the wire. Dissection around the sphere of light kept the wire tip within the surgical specimen. Three of eight initial surgical specimens had focally positive margins. Additional cavity shaves were performed during five lumpectomies and resulted in negative margins in seven of eight patients. Light-guided lumpectomy is a minor change to breast conserving surgery that can be easily incorporated into clinical practice. Further investigation into the clinical benefit of light-guided lumpectomy is warranted. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ramella-Roman J.C.,Catholic University of America | Nayak A.,Eunice Kennedy Shriver National Institute of Child Health and Human Development | Prahl S.A.,Oregon Medical Laser Center
Journal of Biomedical Optics | Year: 2011

We present the design and calibration of a spectroscopic sensitive polarimeter. The polarimeter can measure the full Stokes vector in the wavelength range 550 to 750 nm with 1-nm resolution and consists of a fiber-based spectrophotometer, a white light emitting diode light source, two liquid crystal retarders, and one polarizer. Calibration of the system is achieved with a scheme that does not require knowledge of the polarizing elements' orientation or retardation. Six intensity spectra are required to calculate the full spectrum Stokes vector. Error in the polarimeter is less than 5%. We report the Stokes vectors for light transmitted through nonscattering polarizing elements as well as a measurement of the depolarizing properties of chicken muscle at several wavelengths. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).


Siebert J.C.,CytoAnalytics | Wang L.,Oregon Medical Laser Center | Haley D.P.,Earle A Chiles Research Institute | Romer A.,Oregon Medical Laser Center | And 4 more authors.
Journal of Translational Medicine | Year: 2010

Background: The complex data sets generated by higher-order polychromatic flow cytometry experiments are a challenge to analyze. Here we describe Exhaustive Expansion, a data analysis approach for deriving hundreds to thousands of cell phenotypes from raw data, and for interrogating these phenotypes to identify populations of biological interest given the experimental context.Methods: We apply this approach to two studies, illustrating its broad applicability. The first examines the longitudinal changes in circulating human memory T cell populations within individual patients in response to a melanoma peptide (gp100209-2M) cancer vaccine, using 5 monoclonal antibodies (mAbs) to delineate subpopulations of viable, gp100-specific, CD8+ T cells. The second study measures the mobilization of stem cells in porcine bone marrow that may be associated with wound healing, and uses 5 different staining panels consisting of 8 mAbs each.Results: In the first study, our analysis suggests that the cell surface markers CD45RA, CD27 and CD28, commonly used in historical lower order (2-4 color) flow cytometry analysis to distinguish memory from naïve and effector T cells, may not be obligate parameters in defining central memory T cells (TCM). In the second study, we identify novel phenotypes such as CD29+CD31+CD56+CXCR4+CD90+Sca1-CD44+, which may characterize progenitor cells that are significantly increased in wounded animals as compared to controls.Conclusions: Taken together, these results demonstrate that Exhaustive Expansion supports thorough interrogation of complex higher-order flow cytometry data sets and aids in the identification of potentially clinically relevant findings. © 2010 Siebert et al; licensee BioMed Central Ltd.


McKenna K.A.,Oregon Medical Laser Center | McKenna K.A.,Oregon Health And Science University | Gregory K.W.,Oregon Medical Laser Center | Sarao R.C.,Oregon Medical Laser Center | And 3 more authors.
Journal of Biomaterials Applications | Year: 2012

An off-the-shelf vascular graft biomaterial for vascular bypass surgeries is an unmet clinical need. The vascular biomaterial must support cell growth, be non-thrombogenic, minimize intimal hyperplasia, match the structural properties of native vessels, and allow for regeneration of arterial tissue. Electrospun recombinant human tropoelastin (rTE) as a medial component of a vascular graft scaffold was investigated in this study by evaluating its structural properties, as well as its ability to support primary smooth muscle cell adhesion and growth. rTE solutions of 9, 15, and 20 wt% were electrospun into sheets with average fiber diameters of 167 ± 32, 522 ± 67, and 735 ± 270 nm, and average pore sizes of 0.4 ± 0.1, 5.8 ± 4.3, and 4.9 ± 2.4 μm, respectively. Electrospun rTE fibers were cross-linked with disuccinimidyl suberate to produce an insoluble fibrous polymeric recombinant tropoelastin (prTE) biomaterial. Smooth muscle cells attached via integrin binding to the rTE coatings and proliferated on prTE biomaterials at a comparable rate to growth on prTE coated glass, glass alone, and tissue culture plastic. Electrospun tropoelastin demonstrated the cell compatibility and design flexibility required of a graft biomaterial for vascular applications. © The Author(s) 2011 Reprints and permissions: sagepub.co.uk/journalsPermissions. nav.


McKenna K.A.,Oregon Medical Laser Center | McKenna K.A.,Oregon Health And Science University | Hinds M.T.,Oregon Health And Science University | Sarao R.C.,Oregon Medical Laser Center | And 5 more authors.
Acta Biomaterialia | Year: 2012

The development of vascular grafts has focused on finding a biomaterial that is non-thrombogenic, minimizes intimal hyperplasia, matches the mechanical properties of native vessels and allows for regeneration of arterial tissue. In this study, the structural and mechanical properties and the vascular cell compatibility of electrospun recombinant human tropoelastin (rTE) were evaluated as a potential vascular graft support matrix. Disuccinimidyl suberate (DSS) was used to cross-link electrospun rTE fibers to produce a polymeric recombinant tropoelastin (prTE) matrix that is stable in aqueous environments. Tubular 1 cm diameter prTE samples were constructed for uniaxial tensile testing and 4 mm small-diameter prTE tubular scaffolds were produced for burst pressure and cell compatibility evaluations from 15 wt.% rTE solutions. Uniaxial tensile tests demonstrated an average ultimate tensile strength (UTS) of 0.36 ± 0.05 MPa and elastic moduli of 0.15 ± 0.04 and 0.91 ± 0.16 MPa, which were comparable to extracted native elastin. Burst pressures of 485 ± 25 mm Hg were obtained from 4 mm internal diameter scaffolds with 453 ± 74 μm average wall thickness. prTE supported endothelial cell growth with typical endothelial cell cobblestone morphology after 48 h in culture. Cross-linked electrospun rTE has promising properties for utilization as a vascular graft biomaterial with customizable dimensions, a compliant matrix and vascular cell compatibility. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Morales Cruzado B.,National Institute of Astrophysics, Optics and Electronics | Prahl S.A.,Oregon Medical Laser Center | Delgado Atencio J.A.,National Institute of Astrophysics, Optics and Electronics | Vazquez Y Montiel S.,National Institute of Astrophysics, Optics and Electronics
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Determining optical properties of turbid media has been performed by many research groups using a technique based on iteratively solving the radiative transport equation using the adding doubling technique (IAD). We present a new, alternative method, GA-MCML, for determining optical properties based on a Monte Carlo tech- nique for radiative transport (MCML) guided by a genetics algorithm. The Monte Carlo method is more exible than the adding-doubling technique and can be adapted to a wider range of sample geometries. The genetic algorithm is a robust search technique that is well-adapted to avoiding the local minima in this optimization problem. GA-MCML, has been implemented by modifying the MCML source code to account for two common experimental problems: light losses due to the nite sample size and non-linear integrating sphere eects using Mott's equations. GA-MCML was validated by comparing with IAD method for data acquired at 632.8 nm on a set of phantoms using a single integrating sphere system. The GA-MCML results were equivalent to the IAD technique. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).


Mueller G.R.,Oregon Medical Laser Center | Wolf R.F.,The Oregon Clinic | Hansen P.D.,The Oregon Clinic | Gregory K.W.,Oregon Medical Laser Center | Prahl S.A.,Oregon Medical Laser Center
Journal of Gastrointestinal Surgery | Year: 2010

Background: Bleeding from the liver surface is common after hepatic resection. Animal studies have demonstrated superiority of argon beam coagulation (ABC) and 38% human serum albumin when applied together after partial liver resection when compared to ABC alone. There are no data addressing the combination of albumin and argon beam coagulation (ABCA) applied to the bleeding liver after resection in humans. The aim of this study was to evaluate the safety and efficacy of ABCA on hemostasis when applied to the surface of the liver remnant post-hepatic resection. Methods: Ten patients underwent liver resection and were treated with ABCA immediately after the liver was divided. The liver surface was coated with albumin and ABC applied simultaneously, the liver was covered with gauze for 3 min, and ABCA was repeated if necessary. Number of rebleeding episodes requiring re-application of ABCA, time of ABCA application, overall blood loss, and liver functions were monitored. Patients were followed for at least 6 months. Results: Nine of 10 patients required a single application of ABCA, and one patient required two treatments. Average time of ABC use was 5 ± 3 min. Median blood loss was 230 ml. Liver functions returned to near normal within 4 days of resection. Conclusions: ABCA performed well with respect to hemostatic properties, much like previous observations in animal studies. Further clinical trials are justified using this technique. © 2010 The Society for Surgery of the Alimentary Tract.

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