Optical Radiation Bioeffects Branch

Eidson Road, TX, United States

Optical Radiation Bioeffects Branch

Eidson Road, TX, United States

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Butler S.J.,University of North Texas | Lee D.W.,Chonnam National University | Burney C.W.,United States Air Force Academy | Wigle J.C.,Optical Radiation Bioeffects Branch | Choi T.Y.,University of North Texas
Journal of Biomedical Optics | Year: 2013

We investigated the potential for using polydimethylsiloxane microfluidic devices in a biological assay to explore the cellular stress response (CSR) associated with hyperthermia induced by exposure to laser radiation. In vitro studies of laser-tissue interaction traditionally involved exposing a monolayer of cells. Given the heating-cooling dynamics of the cells and nutrient medium, this technique produces a characteristic bulls-eye temperature history that plagues downstream molecular analyses due to the nonuniform thermal experience of exposed cells. To circumvent this issue, we devised an approach to deliver single cells to the laser beam using a microfluidic channel, allowing homogeneous irradiation and collection of sufficient like-treated cells to measure changes in CSR after laser heating. To test this approach, we irradiated Jurkat-T cells with a 2-wavelength laser in one branch of a 100-wide bifurcated channel while unexposed control cells were simultaneously passing through the other, identical channel. Cell viability was measured using vital dyes, and expression of HSPA1A was measured using reverse transcription polymerase chain reaction. The laser damage threshold was 25 ± 2 J/cm2, and we found a twofold increase in expression at that exposure. This approach may be employed to examine transcriptome-wide/proteome changes and further comparative work across stressors and cell types. © Society of Photo-Optical Instrumentation Engineers.

Hokr B.H.,Texas A&M University | Hokr B.H.,TASC Inc | Clark C.D.,TASC Inc | Clark C.D.,Fort Hays State University | And 3 more authors.
Optics Express | Year: 2013

We develop a higher-order method for non-paraxial beam propagation based on the wide-angle split-step spectral (WASSS) method previously reported [Clark and Thomas, Opt. Quantum. Electron., 41, 849 (2010)]. The higher-order WASSS (HOWASSS) method approximates the Helmholtz equation by keeping terms up to third-order in the propagation step size, in the Magnus expansion. A symmetric exponential operator splitting technique is used to simplify the resulting exponential operators. The HOWASSS method is applied to the problem of waveguide propagation, where an analytical solution is known, to demonstrate the performance and accuracy of the method. The performance enhancement gained by implementing the HOWASSS method on a graphics processing unit (GPU) is demonstrated. When highly accurate results are required the HOWASSS method is shown to be substantially faster than the WASSS method. © 2013 Optical Society of America.

Roth C.C.,University of Texas Health Science Center at San Antonio | Maswadi S.,University of Texas at San Antonio | Ibey B.L.,Radio Frequency Bioeffects Branch | Beier H.T.,Optical Radiation Bioeffects Branch | Glickman R.D.,University of Texas Health Science Center at San Antonio
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2014

Despite 30 years of research, the mechanism behind the induced breakdown of plasma membranes by electrical pulses, termed electroporation, remains unknown. Current theories treat the interaction between the electrical field and the membrane as an entirely electrical event pointing to multiple plausible mechanisms. By investigating the biophysical interaction between plasma membranes and nanosecond electrical pulses (nsEP), we may have identified a non-electric field driven mechanism, previously unstudied in nsEP, which could be responsible for nanoporation of plasma membranes. In this investigation, we use a non-contact optical technique, termed probe beam deflection technique (PBDT), to characterize acoustic shockwaves generated by nsEP traveling through tungsten wire electrodes. We conclude these acoustic shockwaves are the result of the nsEP exposure imparting electrohydraulic forces on the buffer solution. When these acoustic shockwaves occur in close proximity to lipid bilayer membranes, it is possible that they impart a sufficient amount of mechanical stress to cause poration of that membrane. This research establishes for the first time that nsEP discharged in an aqueous medium generate measureable pressure waves of a magnitude capable of mechanical deformation and possibly damage to plasma membranes. These findings provide a new insight into the longunanswered question of how electric fields cause the breakdown of plasma membranes. © 2014 SPIE.

Roth C.C.,University of Texas Health Science Center at San Antonio | Barnes R.A.,University of Texas at San Antonio | Ibey B.L.,Radio Frequency Bioeffects Branch | Beier H.T.,Optical Radiation Bioeffects Branch | And 2 more authors.
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2015

Exposure of cells to very short (<1 μs) electric pulses in the megavolt/meter range have been shown to cause disruption of the plasma membrane. This disruption is often characterized by the formation of numerous small pores (<2 nm in diameter) in the plasma membrane that last for several minutes, allowing the flow of ions into the cell. These small pores are called nanopores and the resulting damage to the plasma membrane is referred to as nanoporation. Nanosecond electrical pulse (nsEP) exposure can impart many different stressors on a cell, including electrical, electro-chemical, and mechanical stress. Thus, nsEP exposure is not a “clean†insult, making determination of the mechanism of nanoporation quite difficult. We hypothesize that nsEP exposure creates acoustic shock waves capable of causing nanoporation. Microarray analysis of primary adult human dermal fibroblasts (HDFa) exposed to nsEP, indicated several genes associated with mechanical stress were selectively upregulated 4 h post exposure. The idea that nanoporation is caused by external mechanical force from acoustic shock waves has, to our knowledge, not been investigated. This work will critically challenge the existing paradigm that nanoporation is caused solely by an electric-field driven event and could provide the basis for a plausible explanation for electroporation.

Williamson C.A.,UK Defence Science and Technology Laboratory | Rickman J.M.,ASC | Freeman D.A.,NAMRU SA | Manka M.A.,ASC | Mclin L.N.,Optical Radiation Bioeffects Branch
The World's Leading Conference on Laser Safety, ILSC 2015 - International Laser Safety Conference, Conference Program and Proceedings | Year: 2015

An experiment was conducted to measure the contribution of atmospheric scatter to the angular profile of received laser irradiance at the eye following outdoor propagation. A 15 W 532 nm laser was propagated over a 380 m outdoor range in San Antonio, Texas during summer 2014. A measurement technique was developed to determine an atmospheric scatter function, which was then compared to human eye scatter to assess the overall impact on laser eye dazzle. It was concluded that, for such short range laser engagements in atmospheres of good to moderate air quality, atmospheric scatter makes a negligible impact upon laser eye dazzle.

Huantes D.,TASC Inc | Kennedy P.,Optical Radiation Bioeffects Branch | Flemming B.,Selex ES Ltd. | Flower M.,UK Ministry of Defense
The World's Leading Conference on Laser Safety, ILSC 2015 - International Laser Safety Conference, Conference Program and Proceedings | Year: 2015

The use of Probabilistic Risk Assessment (PRA) techniques to perform laser hazard analyses for lasers in outdoor environments has become an increasingly accepted alternative to standard deterministic methods, based on Maximum Permissible Exposure (MPE) limits. The United Kingdom (UK) Ministry of Defence (MoD) and the United States (US) Air Force Research Laboratory (AFRL) have collaborated to develop a jointly-owned, PRA-based, laser range safety tool, the Military Advanced Technology Integrated Laser hazarD Assessment (MATILDA) system. For an airborne laser designator illuminating a target on a military test range, MATILDA performs a dual hazard analysis to determine the suitability of a specified aircraft attack track. The probability of injury to an unprotected person outside the Controlled Range Area (CRA), is calculated for two different regimes: i) a "fault-free" regime, where the laser directional control system is operating as designed, with the standard pointing error distribution, and ii) a "fault/failure" regime, where the directional control system fails to operate as designed, producing potentially large pointing errors depending on the system safeguards. Based on the analysis, restrictions on laser firing are subsequently imposed on those portions of the attack track for which the calculated hazard exceeds acceptable limits.

Cone M.T.,Texas A&M University | Mason J.D.,Texas A&M University | Figueroa E.,Texas A&M University | Hokr B.H.,Texas A&M University | And 8 more authors.
Optica | Year: 2015

A number of imaging modalities rely on the exact knowledge of both the absorption and scattering properties of cells and organelles. We report a simple method for accurate and precise measurement of the optical absorption coefficient of biological samples, even in the presence of strong scattering. The technique is based on cavity ring-down spectroscopy, but the traditional mirrored cavity is replaced with a high-reflectivity integrating cavity. The Lambertian behavior of the cavity walls creates an isotropic field inside the cavity, thereby eliminating the effects of scattering in the sample. Thus, integrating cavity ring-down spectroscopy (ICRDS) provides a true, direct measurement of the absorption coefficient, as opposed to the net attenuation. We demonstrate the effectiveness of this technique by measuring the absorption coefficient of retinal pigmented epithelium cells. Furthermore, we demonstrate that ICRDS is insensitive to scattering effects using suspensions of copolymer microspheres and an absorbing dye solution. These results are compared with measurements made using a more traditional transmission-style setup. This technique will have an impact on the field of nanoscience, where optical characterization of nanoparticles is still done using a conventional spectrometer that is only capable of providing measurements of the extinction coefficient. © 2015 Optical Society of America.

Schuster K.,TASC Inc | Vincelette R.,TASC Inc | Shingledecker A.,TASC Inc | Bixler J.,Optical Radiation Bioeffects Branch | And 2 more authors.
The World's Leading Conference on Laser Safety, ILSC 2015 - International Laser Safety Conference, Conference Program and Proceedings | Year: 2015

Advanced imaging techniques and proteomic technology continue to push the boundaries for diagnosing and understanding retinal laser lesion exposures. We conducted retinal imaging in the rhesus macaque to compare the appearance of suprathreshold laser lesions in the macula from both photothermal (532 nm, 100 ms) and photomechanical (532 nm, 9 ns) insult using five different imaging systems: Three clinically approved systems; Heidelberg Spectralis SD- OCT-SLO, Heidelberg HRT3 cSLO, and Topcon Fundus camera, and two experimental systems; multispectral using a fundus camera and hyperspectral detection using a PSI Inc. LSLO. In addition to imaging, blood plasma samples were acquired before and after (6 and 24 hrs) laser exposure to search for biomarkers occurring from two different laser damage mechanisms. Imaging results should help identify the best potential imaging systems for capturing retinal laser lesions from photothermal or photomechanical injury. The proteomics results will assist in understanding the elicited molecular pathways involved in damage response to the two types of retinal laser insult, and may be used to hallmark approaches for potential treatment options.

Rockwell B.,Optical Radiation Bioeffects Branch | Thomas R.,Optical Radiation Bioeffects Branch | Zimmerman S.,U.S. Navy
The World's Leading Conference on Laser Safety, ILSC 2015 - International Laser Safety Conference, Conference Program and Proceedings | Year: 2015

The ANSI Z136.1 laser safety standard serves as the 'foundation for laser safety in the United States. An update to this document was released in 2014, with significant re-organization of the documented material and updates to processes and exposure limits. We will review the changes in this document and their implications for laser safety programs.

Early E.,ITASC Inc. | Bailey A.,ITASC Inc. | Kumru S.,Optical Radiation Bioeffects Branch | Thomas R.,Optical Radiation Bioeffects Branch
The World's Leading Conference on Laser Safety, ILSC 2015 - International Laser Safety Conference, Conference Program and Proceedings | Year: 2015

Reflection of a laser beam from a surface depends on t the optical properties of the surface, and can have I components that are diffuse (in all directions) or I specular (in one direction). Hazard distances tend to, be short and easily calculated for diffuse reflections. ' However, specular reflections have longer hazard • distances and their calculation poses challenges due to I the spatial and temporal characteristics of the reflected | beam. We have developed and refined a methodology to calculate hazard distances from specular reflections, i This methodology uses analytical expressions to ; determine the irradiance and exposure time of the I reflected beam, from which hazard distances are { calculated. The method accounts for the properties of | the incident beam, the material reflecting properties, j and the shape of the surface. The motivations and concepts of the specular ] methodology are presented, along with the equations | resulting from this approach. The spatial and temporal i characteristics of the reflected beam for a specific laser and surface are calculated from the application of these j equations. These characteristics are then used to j determine either localization of hazardous regions in i the surrounding space or a description of possible 1 hazards at specific locations. Examples of the | application of the specular methodology are presented | with their corresponding hazardous conditions. I.

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