Influence of the ablation plume on the removal process during ArF-excimer laser photoablation

NASA Astrophysics Data System (ADS)

Doerbecker, Christina; Lubatschowski, Holger; Lohmann, Stefan; Ruff, Christine; Kermani, Omid; Ertmer, Wolfgang

1996-01-01

Correction of myopia with the ArF-excimer laser (PRK) sometimes leads to a so called 'central island' formation on the anterior corneal surface. The attenuation of the laser beam by the ablation plume might be one reason for this phenomenon. The attenuation properties of the ablation plume were investigated by a probe beam parallel to the surface of the tissue probe. By varying the laser parameters (fluence, repetition rate, spot size) and the target tissue (cornea, PMMA) the attenuation of the probe beam was measured time and spatial resolved. As a result of this study, a significant influence of the removal process due to scattering and absorption within the ablation plume can be assumed as a function of repetition rate, spot size and air flow on the tissue surface.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE PAGES

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole; ...

2017-06-19

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

SciTech Connect

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

SciTech Connect

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole L.

We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security applications.

Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere

SciTech Connect

Harilal, S. S.; Miloshevsky, G. V.; Diwakar, P. K.

2012-08-15

We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100-500 ns with instabilities near themore » laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times {<=}400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.« less

Dynamics of thermal plumes in three-dimensional isoviscous thermal convection

NASA Astrophysics Data System (ADS)

Zhong, Shijie

2005-07-01

The dynamics of mantle plumes are important for understanding intraplate volcanism and heat transfer in the mantle. Using 3-D numerical models and scaling analyses, we investigated the controls of convective vigour or Ra (Rayleigh number) on the dynamics of thermal plumes in isoviscous and basal heating thermal convection. We examined the Ra dependence of plume number, plume spacing, plume vertical velocity and plume radius. We found that plume number does not increase monotonically with Ra. At relatively small Ra(<=106), plume number is insensitive to Ra. For 3 × 106<=Ra<= 3 × 107, plume number scales as Ra0.31 and plume spacing λ~Ra-0.16~δ1/2, where δ is the thickness of the thermal boundary layer. However, for larger Ra(~108) plume number and plume spacing again become insensitive to Ra. This indicates that the box depth poses a limit on plume spacing and plume number. We demonstrate from both scaling analyses and numerical experiments that the scaling exponents for plume number, n, heat flux, β, and average velocity on the bottom boundary, v, satisfy n= 4β- 2v. Our scaling analyses also suggest that vertical velocity in upwelling plumes Vup~Ra2(1-n+β/2)/3 and that plume radius Rup~Ra(β-1-n/2)/3, which differ from the scalings for the bottom boundary velocity and boundary layer thickness.

Thermal Ablation Modeling for Silicate Materials

NASA Technical Reports Server (NTRS)

Chen, Yih-Kanq

2016-01-01

A thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in ablation simulations of the meteoroid or glassy Thermal Protection Systems for spacecraft. Time-dependent axi-symmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. For model validation, the surface recession of fused amorphous quartz rod is computed, and the recession predictions reasonably agree with available data. The present parametric studies for two groups of meteoroid earth entry conditions indicate that the mass loss through moving molten layer is negligibly small for heat-flux conditions at around 1 MW/cm(exp. 2).

Periodic Phenomena In Laser-Ablation Plasma Plumes: A Self-Organization Scenario

SciTech Connect

Gurlui, S.; Sanduloviciu, M.; Mihesan, C.

2006-01-15

Experimental evidence of the appearance of a proper periodic dynamics in a plasma plume created by pulsed laser ablation is considered as a hint for the presence of a self-organization scenario that explains similar phenomena observed in plasma diodes.

Toward single-cell analysis by plume collimation in laser ablation electrospray ionization mass spectrometry.

PubMed

Stolee, Jessica A; Vertes, Akos

2013-04-02

Ambient ionization methods for mass spectrometry have enabled the in situ and in vivo analysis of biological tissues and cells. When an etched optical fiber is used to deliver laser energy to a sample in laser ablation electrospray ionization (LAESI) mass spectrometry, the analysis of large single cells becomes possible. However, because in this arrangement the ablation plume expands in three dimensions, only a small portion of it is ionized by the electrospray. Here we show that sample ablation within a capillary helps to confine the radial expansion of the plume. Plume collimation, due to the altered expansion dynamics, leads to greater interaction with the electrospray plume resulting in increased ionization efficiency, reduced limit of detection (by a factor of ~13, reaching 600 amol for verapamil), and extended dynamic range (6 orders of magnitude) compared to conventional LAESI. This enhanced sensitivity enables the analysis of a range of metabolites from small cell populations and single cells in the ambient environment. This technique has the potential to be integrated with flow cytometry for high-throughput metabolite analysis of sorted cells.

The role of laser wavelength on plasma generation and expansion of ablation plumes in air

SciTech Connect

Hussein, A. E.; Department of Physics, McGill University, Montreal, Quebec H3A 0G4; Diwakar, P. K.

2013-04-14

We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photographymore » and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.« less

Higher Order Chemistry Models in the CFD Simulation of Laser-Ablated Carbon Plumes

NASA Technical Reports Server (NTRS)

Scott, C. D.; Greendyke, R. B.; Creel, J. R.; Payne, B. T.

2005-01-01

Production of single-walled carbon nanotubes (SWNT) has taken place for a number of years and by a variety of methods such-as laser ablation, chemical vapor deposition, and arc-jet ablation. Yet, little is actually understood about the exact chemical kinetics and processes that occur in SWNT formation. In recent time, NASA Johnson Space Center has devoted a considerable effort to the experimental evaluation of the laser ablation production process for SWNT originally developed at Rice University. To fully understand the nature of the laser ablation process it is necessary to understand the development of the carbon plume dynamics within the laser ablation oven. The present work is a continuation of previous studies into the efforts to model plume dynamics using computational fluid dynamics (CFD). The ultimate goal of the work is to improve understanding of the laser ablation process, and through that improved understanding, refine the laser ablation production of SWNT. Fig. 1 shows a basic schematic of the laser-ablation oven at NASA-JSC. Construction of the facility is simple in concept. Two concentric quartz tubes of 1.5 mm thickness form the inner and outer tubes with inside diameters of 2.2 and 5.08 cm respectively. At one end of the inner tube are located two 60 Hz pulsed lasers operating at 1064 nm and 532 nm wavelength with beam diameters of 5 mm aligned coaxially with the longitudinal axis of the inner quartz tube. For standard nanotube production runs, a 10 ns 532 nm pulse is followed 50 ns later by a 10 ns 1064 nm pulse. Each pulse is of 300 mJ energy. A target of carbon graphite with approximately 1% nickel and cobalt catalysts is located at the other end of the inner quartz tube. In the ordinary processing of SWNT, a base flow of 100 sccm of argon is maintained from the laser location and exits past the carbon target at a pressure of 66.7 kPa. These conditions yield a baseline mass flow through the chamber of 2.723x10(exp -6)kg/s of argon. The whole

Condensation of ablation plumes in the irradiation of metals by high-intensity nanosecond laser pulses at atmospheric pressure

SciTech Connect

Kozadaev, K V

2016-01-31

The Anisimov–Luk'yanchuk model is adapted for describing the condensation of vapour-plasma plumes produced in the irradiation of metal targets by high-intensity (10{sup 8} – 10{sup 10} W cm{sup -2}) nanosecond (10 – 100 ns) pulses at atmospheric pressure. The resultant data suggest that the initial stages of the development of metal ablation plumes correspond with a high degree of accuracy to the Zel'dovich–Raizer theory of dynamic condensation; however, at the stage of the ablation plume decay, the liquid-droplet phase is formed primarily by coalescence of 'nuclei'. (interaction of laser radiation with matter. laser plasma)

Characterization of ultrafast laser-ablation plasma plumes at various Ar ambient pressures

DOE PAGES

Diwakar, P. K.; Harilal, S. S.; Phillips, M. C.; ...

2015-07-30

Expansion dynamics and internal plume structures of fs laser ablated brass plasma in Ar at various pressure levels ranging from vacuum to atmospheric were studied using multitude of diagnostic tools including time resolved and time integrated 2-dimensional imaging, optical time of flight measurements and visible emission spectroscopy. Temporal evolution of excited Cu and Zn species in the plume were imaged using band pass interference filters and compared its hydrodynamic expansion features with spectrally integrated images of the plume. 2D imaging coupled with monochromatic line selection showed several interesting features at various pressure levels which include velocity differences among the plumemore » species, emission intensity distribution, plasma temperature, electron density etc. Plume confinement, enhanced signal intensity, and dual peak structures in time-of-flight profiles were observed at intermediate pressure range of ~10 Torr. Optimum signal to background ratio was also observed in this pressure range. As a result, possible mechanisms for observed changes in plume shape, optical emission intensity and dual peak structures in time-of-flight profiles were discussed.« less

3D Multifunctional Ablative Thermal Protection System

NASA Technical Reports Server (NTRS)

Feldman, Jay; Venkatapathy, Ethiraj; Wilkinson, Curt; Mercer, Ken

2015-01-01

NASA is developing the Orion spacecraft to carry astronauts farther into the solar system than ever before, with human exploration of Mars as its ultimate goal. One of the technologies required to enable this advanced, Apollo-shaped capsule is a 3-dimensional quartz fiber composite for the vehicle's compression pad. During its mission, the compression pad serves first as a structural component and later as an ablative heat shield, partially consumed on Earth re-entry. This presentation will summarize the development of a new 3D quartz cyanate ester composite material, 3-Dimensional Multifunctional Ablative Thermal Protection System (3D-MAT), designed to meet the mission requirements for the Orion compression pad. Manufacturing development, aerothermal (arc-jet) testing, structural performance, and the overall status of material development for the 2018 EM-1 flight test will be discussed.

Characteristics of plasma plume in ultrafast laser ablation with a weakly ionized air channel

SciTech Connect

Hou, Huaming; Yang, Bo; Mao, Xianglei

We report the influence of femtosecond (fs) laser weakly ionized air channel on characteristics of plasma induced from fs-laser ablation of solid Zr metal target. A novel method to create high temperature, low electron density plasma with intense elemental emission and weak bremsstrahlung emission was demonstrated. Weakly ionized air channel was generated as a result of a non-linear phenomenon. Two-dimensional time-resolved optical-emission images of plasma plumes were taken for plume dynamics analysis. Dynamic physical properties of filament channels were simulated. In particular, we investigated the influence of weakly ionized air channel on the evolution of solid plasma plume. Plasma plumemore » splitting was observed whilst longer weakly ionized air channel formed above the ablation spot. The domination mechanism for splitting is attributed to the long-lived underdense channel created by fs-laser induced weakly ionization of air. The evolutions of atomic/molecular emission intensity, peak broadening, and plasma temperature were analyzed, and the results show that the part of plasma entering weakly ionized air channel features higher initial temperature, lower electron density and faster decay.« less

Characteristics of plasma plume in ultrafast laser ablation with a weakly ionized air channel

DOE PAGES

Hou, Huaming; Yang, Bo; Mao, Xianglei; ...

2018-05-10

We report the influence of femtosecond (fs) laser weakly ionized air channel on characteristics of plasma induced from fs-laser ablation of solid Zr metal target. A novel method to create high temperature, low electron density plasma with intense elemental emission and weak bremsstrahlung emission was demonstrated. Weakly ionized air channel was generated as a result of a non-linear phenomenon. Two-dimensional time-resolved optical-emission images of plasma plumes were taken for plume dynamics analysis. Dynamic physical properties of filament channels were simulated. In particular, we investigated the influence of weakly ionized air channel on the evolution of solid plasma plume. Plasma plumemore » splitting was observed whilst longer weakly ionized air channel formed above the ablation spot. The domination mechanism for splitting is attributed to the long-lived underdense channel created by fs-laser induced weakly ionization of air. The evolutions of atomic/molecular emission intensity, peak broadening, and plasma temperature were analyzed, and the results show that the part of plasma entering weakly ionized air channel features higher initial temperature, lower electron density and faster decay.« less

Analysis of iodinated contrast delivered during thermal ablation: is material trapped in the ablation zone?

PubMed

Wu, Po-Hung; Brace, Chris L

2016-08-21

Intra-procedural contrast-enhanced CT (CECT) has been proposed to evaluate treatment efficacy of thermal ablation. We hypothesized that contrast material delivered concurrently with thermal ablation may become trapped in the ablation zone, and set out to determine whether such an effect would impact ablation visualization. CECT images were acquired during microwave ablation in normal porcine liver with: (A) normal blood perfusion and no iodinated contrast, (B) normal perfusion and iodinated contrast infusion or (C) no blood perfusion and residual iodinated contrast. Changes in CT attenuation were analyzed from before, during and after ablation to evaluate whether contrast was trapped inside of the ablation zone. Visualization was compared between groups using post-ablation contrast-to-noise ratio (CNR). Attenuation gradients were calculated at the ablation boundary and background to quantitate ablation conspicuity. In Group A, attenuation decreased during ablation due to thermal expansion of tissue water and water vaporization. The ablation zone was difficult to visualize (CNR  =  1.57  ±  0.73, boundary gradient  =  0.7  ±  0.4 HU mm(-1)), leading to ablation diameter underestimation compared to gross pathology. Group B ablations saw attenuation increase, suggesting that iodine was trapped inside the ablation zone. However, because the normally perfused liver increased even more, Group B ablations were more visible than Group A (CNR  =  2.04  ±  0.84, boundary gradient  =  6.3  ±  1.1 HU mm(-1)) and allowed accurate estimation of the ablation zone dimensions compared to gross pathology. Substantial water vaporization led to substantial attenuation changes in Group C, though the ablation zone boundary was not highly visible (boundary gradient  =  3.9  ±  1.1 HU mm(-1)). Our results demonstrate that despite iodinated contrast being trapped in the ablation zone, ablation visibility

Comparison of plume dynamics for laser ablated metals: Al and Ti

NASA Astrophysics Data System (ADS)

Bauer, William; Perram, Glen P.; Haugan, Timothy

2018-03-01

Emissive plumes from pulsed laser ablation of bulk Ti and Al from KrF laser irradiation at laser fluence up to 3.5 J/cm2 and argon background pressures of 0-1 Torr have been observed using gated intensified charged-coupled device imagery. Mass loss for Ti increases from 0.1 to 0.8 μg/pulse as pulse energy increase from 174 to 282 mJ/pulse (35-170 photons/atom) and decreases by ˜30% as pressure increases from vacuum to 1 Torr. Early plume energies are described by the free expansion velocities of 1.57 ± 0.02 and of 1.81 ± 0.07 cm/μs for Ti and Al, respectively, and up to 90% of the incoming laser energy can be attributed to the Al shock front in the mid-field. The ablation thresholds of 90 ± 27 mJ (1.12 ± 0.34 J/cm2) for Ti and 126 ± 13 mJ (1.58 ± 0.16 J/cm2) for Al also represent 30%-70% of the incident laser energy. The decrease in mass loss at higher pressures is attributed to plasma shielding of the target surface.

Investigation of plume dynamics during picosecond laser ablation of H13 steel using high-speed digital holography

NASA Astrophysics Data System (ADS)

Pangovski, Krste; Otanocha, Omonigho B.; Zhong, Shan; Sparkes, Martin; Liu, Zhu; O'Neill, William; Li, Lin

2017-02-01

Ablation of H13 tool steel using pulse packets with repetition rates of 400 and 1000 kHz and pulse energies of 75 and 44 μ {J}, respectively, is investigated. A drop in ablation efficiency (defined here as the depth per pulse or μ {m}{/}μ {J}) is shown to occur when using pulse energies of E_{{pulse}} > 44 μ {J}, accompanied by a marked difference in crater morphology. A pulsed digital holographic system is applied to image the resulting plumes, showing a persistent plume in both cases. Holographic data are used to calculate the plume absorption and subsequently the fraction of pulse energy arriving at the surface after traversing the plume for different pulse arrival times. A significant proportion of the pulse energy is shown to be absorbed in the plume for E_{{pulse}} > 44 μ {J} for pulse arrival times corresponding to {>}1 MHz pulse repetition rate, shifting the interaction to a vapour-dominated ablation regime, an energetically costlier ablation mechanism.

Thermal distribution of microwave antenna for atrial fibrillation catheter ablation.

PubMed

Zhang, Huijuan; Nan, Qun; Liu, Youjun

2013-09-01

The aim of this study is to investigate the effects of ablation parameters on thermal distribution during microwave atrial fibrillation catheter ablation, such as ablation time, ablation power, blood condition and antenna placement, and give proper ablative parameters to realise transmural ablation. In this paper, simplified 3D antenna-myocardium-blood finite element method models were built to simulate the endocardial ablation operation. Thermal distribution was obtained based on the coupled electromagnetic-thermal analysis. Under different antenna placement conditions and different microwave power inputs within 60 s, the lesion dimensions (maximum depth, maximum width) of the ablation zones were analysed. The ablation width and depth increased with the ablation time. The increase rate significantly slowed down after 10 s. The maximum temperature was located in 1 mm under the antenna tip when perpendicular to the endocardium, while 1.5 mm away from the antenna axis and 26 mm along the antenna (with antenna length about 30 mm) in the myocardium when parallel to the endocardium. The maximum temperature in the ablated area decreased and the effective ablation area (with the temperature raised to 50°C) shifted deeper into the myocardium due to the blood cooling. The research validated that the microwave antenna can provide continuous long and linear lesions for the treatment of atrial fibrillation. The dimensions of the created lesion widths were all larger than those of the depths. It is easy for the microwave antenna to produce transmural lesions for an atrial wall thickness of 2-6 mm by adjusting the applied power and ablation time.

Ablative Thermal Response Analysis Using the Finite Element Method

NASA Technical Reports Server (NTRS)

Dec John A.; Braun, Robert D.

2009-01-01

A review of the classic techniques used to solve ablative thermal response problems is presented. The advantages and disadvantages of both the finite element and finite difference methods are described. As a first step in developing a three dimensional finite element based ablative thermal response capability, a one dimensional computer tool has been developed. The finite element method is used to discretize the governing differential equations and Galerkin's method of weighted residuals is used to derive the element equations. A code to code comparison between the current 1-D tool and the 1-D Fully Implicit Ablation and Thermal Response Program (FIAT) has been performed.

Flow-dependent vascular heat transfer during microwave thermal ablation.

PubMed

Chiang, Jason; Hynes, Kieran; Brace, Christopher L

2012-01-01

Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

An analytic model of axisymmetric mantle plume due to thermal and chemical diffusion

NASA Technical Reports Server (NTRS)

Liu, Mian; Chase, Clement G.

1990-01-01

An analytic model of axisymmetric mantle plumes driven by either thermal diffusion or combined diffusion of both heat and chemical species from a point source is presented. The governing equations are solved numerically in cylindrical coordinates for a Newtonian fluid with constant viscosity. Instead of starting from an assumed plume source, constraints on the source parameters, such as the depth of the source regions and the total heat input from the plume sources, are deduced using the geophysical characteristics of mantle plumes inferred from modelling of hotspot swells. The Hawaiian hotspot and the Bermuda hotspot are used as examples. Narrow mantle plumes are expected for likely mantle viscosities. The temperature anomaly and the size of thermal plumes underneath the lithosphere can be sensitive indicators of plume depth. The Hawaiian plume is likely to originate at a much greater depth than the Bermuda plume. One suggestive result puts the Hawaiian plume source at a depth near the core-mantle boundary and the source of the Bermuda plume in the upper mantle, close to the 700 km discontinuity. The total thermal energy input by the source region to the Hawaiian plume is about 5 x 10(10) watts. The corresponding diameter of the source region is about 100 to 150 km. Chemical diffusion from the same source does not affect the thermal structure of the plume.

Alternative High Performance Polymers for Ablative Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Boghozian, Tane; Stackpoole, Mairead; Gonzales, Greg

2015-01-01

Ablative thermal protection systems are commonly used as protection from the intense heat during re-entry of a space vehicle and have been used successfully on many missions including Stardust and Mars Science Laboratory both of which used PICA - a phenolic based ablator. Historically, phenolic resin has served as the ablative polymer for many TPS systems. However, it has limitations in both processing and properties such as char yield, glass transition temperature and char stability. Therefore alternative high performance polymers are being considered including cyanate ester resin, polyimide, and polybenzoxazine. Thermal and mechanical properties of these resin systems were characterized and compared with phenolic resin.

Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures

SciTech Connect

Miloshevsky, Alexander; Harilal, Sivanandan S.; Miloshevsky, Gennady, E-mail: gennady@purdue.edu

2014-04-15

Plasma expansion with shockwave formation during laser ablation of materials in a background gasses is a complex process. The spatial and temporal evolution of pressure, temperature, density, and velocity fields is needed for its complete understanding. We have studied the expansion of femtosecond (fs) laser-ablated aluminum (Al) plumes in Argon (Ar) gas at 0.5 and 1 atmosphere (atm). The expansion of the plume is investigated experimentally using shadowgraphy and fast-gated imaging. The computational fluid dynamics (CFD) modeling is also carried out. The position of the shock front measured by shadowgraphy and fast-gated imaging is then compared to that obtained frommore » the CFD modeling. The results from the three methods are found to be in good agreement, especially during the initial stage of plasma expansion. The computed time- and space-resolved fields of gas-dynamic parameters have provided valuable insights into the dynamics of plasma expansion and shockwave formation in fs-pulse ablated Al plumes in Ar gas at 0.5 and 1 atm. These results are compared to our previous data on nanosecond (ns) laser ablation of Al [S. S. Harilal et al., Phys. Plasmas 19, 083504 (2012)]. It is observed that both fs and ns plumes acquire a nearly spherical shape at the end of expansion in Ar gas at 1 atm. However, due to significantly lower pulse energy of the fs laser (5 mJ) compared to pulse energy of the ns laser (100 mJ) used in our studies, the values of pressure, temperature, mass density, and velocity are found to be smaller in the fs laser plume, and their time evolution occurs much faster on the same time scale. The oscillatory shock waves clearly visible in the ns plume are not observed in the internal region of the fs plume. These experimental and computational results provide a quantitative understanding of plasma expansion and shockwave formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures.« less

Thermal radiation from large bolides and impact plumes

NASA Astrophysics Data System (ADS)

Svetsov, V.; Shuvalov, V.

2017-09-01

Numerical simulations of the impacts of asteroids and comets from 20 m to 3 km in diameter have been carried out and thermal radiation fluxes on the ground and luminous efficiencies of the impacts have been calculated. It was assumed that the cosmic objects have no strength, deform, fragment, and vaporize in the atmosphere. After the impact on the ground, formation of craters and plumes was simulated taking into account internal friction of destroyed rocks and a wake formed in the atmosphere. The equations of radiative transfer, added to the equations of gas dynamics, were used in the approximation of radiative heat diffusion or, if the Rosseland optical depth of a radiating volume of gas and vapor was less than unity, in the approximation of volume emission. Radiation fluxes on the Earth's surface were calculated by integrating the equation of radiative transfer along rays passing through a luminous area. Direct thermal radiation from fireballs and impact plumes produced by asteroids and comets larger than 50 m in diameter is dangerous for people, animals, plants, economic objects. Forest fires can be ignited on the ground within a radius of roughly 1000 times the body's diameter (for diameters of the order or smaller than 1 km), 50-m-diameter bodies can ignite forest fires within a radius of up to 40 km and 3-km asteroids - within 1700 km.

Plume splitting and oscillatory behavior in transient plasmas generated by high-fluence laser ablation in vacuum

NASA Astrophysics Data System (ADS)

Focsa, C.; Gurlui, S.; Nica, P.; Agop, M.; Ziskind, M.

2017-12-01

We present a short overview of studies performed in our research groups over the last decade on the characterization of transient plasma plumes generated by laser ablation in various temporal regimes, from nanosecond to femtosecond. New results are also presented along with this overview, both being placed in the context of similar studies performed by other investigators. Optical (fast gate intensified CCD camera imaging and space- and time-resolved emission spectroscopy) and electrical (mainly Langmuir probe) methods have been applied to experimentally explore the dynamics of the plasma plume and its constituents. Peculiar effects as plume splitting and sharpening or oscillations onset have been evidenced in vacuum at high laser fluence. New theoretical approaches have been developed to account for the experimental observations.

Understanding plume splitting of laser ablated plasma: A view from ion distribution dynamics

SciTech Connect

Wu, Jian; Li, Xingwen; Wei, Wenfu

2013-11-15

Plume splitting in low-pressure ambient air was understood in view of ion distribution dynamics from the laser ablated Al plasma (1064 nm 0.57 J/mm{sup 2}) by combining fast photography and spatially resolved spectroscopy. In the beginning, the spectral lines were mainly from the Al III ion. Then, the Bragg peak in stopping power of the ambient gas to Al III could be the dominant reason for the enhanced emission from the fast moving part, and the recombination of Al III to Al I-II ions near the target surface was response to the radiations from the slow moving/stationary part. As themore » ambient gas pressure increased, stopping distances of the Al III decreased, and radiation from the air ions became pronounced. The laser shadowgraph image at 1100 Pa indicated that the shock wave front located between the fast moving and slow moving parts. Electron densities of the fast moving plasma, which peaked at the plasma front, were on the order of 10{sup 16} cm{sup −3}, and the electron temperatures were 2–3 eV.« less

Impact of oxygen chemistry on the emission and fluorescence spectroscopy of laser ablation plumes

NASA Astrophysics Data System (ADS)

Hartig, K. C.; Brumfield, B. E.; Phillips, M. C.; Harilal, S. S.

2017-09-01

Oxygen present in the ambient gas medium may affect both laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) emission through a reduction of emission intensity and persistence. In this study, an evaluation is made on the role of oxygen in the ambient environment under atmospheric pressure conditions in LIBS and laser ablation (LA)-LIF emission. To generate plasmas, 1064 nm, 10 ns pulses were focused on an aluminum alloy sample. LIF was performed by frequency scanning a CW laser over the 396.15 nm (3s24s 2S1/2 → 3s23p 2P°3/2) Al I transition. Time-resolved emission and fluorescence signals were recorded to evaluate the variation in emission intensity caused by the presence of oxygen. The oxygen partial pressure (po) in the atmospheric pressure environment using N2 as the makeup gas was varied from 0 to 400 Torr O2. 2D-fluorescence spectroscopy images were obtained for various oxygen concentrations for simultaneous evaluation of the emission and excitation spectral features. Results showed that the presence of oxygen in the ambient environment reduces the persistence of the LIBS and LIF emission through an oxidation process that depletes the density of atomic species within the resulting laser-produced plasma (LPP) plume.

Ablation and Thermal Response Property Model Validation for Phenolic Impregnated Carbon Ablator

NASA Technical Reports Server (NTRS)

Milos, F. S.; Chen, Y.-K.

2009-01-01

Phenolic Impregnated Carbon Ablator was the heatshield material for the Stardust probe and is also a candidate heatshield material for the Orion Crew Module. As part of the heatshield qualification for Orion, physical and thermal properties were measured for newly manufactured material, included emissivity, heat capacity, thermal conductivity, elemental composition, and thermal decomposition rates. Based on these properties, an ablation and thermal-response model was developed for temperatures up to 3500 K and pressures up to 100 kPa. The model includes orthotropic and pressure-dependent thermal conductivity. In this work, model validation is accomplished by comparison of predictions with data from many arcjet tests conducted over a range of stagnation heat flux and pressure from 107 Watts per square centimeter at 2.3 kPa to 1100 Watts per square centimeter at 84 kPa. Over the entire range of test conditions, model predictions compare well with measured recession, maximum surface temperatures, and in depth temperatures.

Thermally-Driven Mantle Plumes Reconcile Hot-spot Observations

NASA Astrophysics Data System (ADS)

Davies, D.; Davies, J.

2008-12-01

Hot-spots are anomalous regions of magmatism that cannot be directly associated with plate tectonic processes (e.g. Morgan, 1972). They are widely regarded as the surface expression of upwelling mantle plumes. Hot-spots exhibit variable life-spans, magmatic productivity and fixity (e.g. Ito and van Keken, 2007). This suggests that a wide-range of upwelling structures coexist within Earth's mantle, a view supported by geochemical and seismic evidence, but, thus far, not reproduced by numerical models. Here, results from a new, global, 3-D spherical, mantle convection model are presented, which better reconcile hot-spot observations, the key modification from previous models being increased convective vigor. Model upwellings show broad-ranging dynamics; some drift slowly, while others are more mobile, displaying variable life-spans, intensities and migration velocities. Such behavior is consistent with hot-spot observations, indicating that the mantle must be simulated at the correct vigor and in the appropriate geometry to reproduce Earth-like dynamics. Thermally-driven mantle plumes can explain the principal features of hot-spot volcanism on Earth.

Time-of-flight spectroscopy characterization of the plasma plume from a laser-ablated potassium titanyl phosphate crystal

NASA Astrophysics Data System (ADS)

Ying, Minju; Wang, XiaoXiao; Cheng, Wei; Liao, Bin; Zhang, Xu

2015-06-01

Optical emission spectra of the plasma produced by 1.06-μm Nd:YAG laser irradiation of a potassium titanyl phosphate (KTP) crystal were recorded and analyzed in a time- and spatially resolved manner. The composition and evolution of the plasma plume were studied in low vacuum conditions. Emission lines associated with Ti(I), Ti(II) and K(I) were identified in the plasma. The delay times of emission peaks for the ablated species were investigated as a function of the observation distance from the target surface, and the velocities of these species were derived accordingly. Two emission peaks corresponding to a fast and a slow component of ablated Ti(I) were observed by optical time-of-flight spectroscopy. The origins of the two peaks and a possible mechanism for the laser ablation are discussed.

Monitoring of KrF excimer laser ablation for burn scars: a comparative study of transient reflection measurement and time-resolved photography of ablation plume

NASA Astrophysics Data System (ADS)

Nakajima, Akio; Arai, Tsunenori; Kikuchi, Makoto; Iwaya, Akimi; Arai, Katsuyuki; Inazaki, Satoshi; Takaoka, Takatsugu; Kato, Masayoshi

1995-05-01

A simple laser ablation monitoring during burn scar removal by KrF laser irradiation was studied to control laser fluence in real-time. Because, to obtain suitable surface for auto skin-graft, the laser fluence should be precisely controlled at each laser shot. We employed simple probe transmission method which could detect ejected material/phenomena from irradiated surface. The time-course of measured probe intensity contained a couple of attenuated peaks, which might corresponded to a shock wave front and debris plume. The delay time from laser irradiation to the debris plume peak appearance varied with the ablation fluence. The delay time of 1 J/cm2 (near ablation threshold) case prolonged 25% from 8 J/cm2 (far above threshold) case. Therefore, we think the delay time measurement by means of the simple probe transmission method may be available to attain the laser fluence control for nonuniform burn scar removal. The time-resolved photography and probe reflection method were also studied to understand the measured time-course of the transmitted probe intensity.

Ablation, Thermal Response, and Chemistry Program for Analysis of Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Milos, Frank S.; Chen, Yih-Kanq

2010-01-01

In previous work, the authors documented the Multicomponent Ablation Thermochemistry (MAT) and Fully Implicit Ablation and Thermal response (FIAT) programs. In this work, key features from MAT and FIAT were combined to create the new Fully Implicit Ablation, Thermal response, and Chemistry (FIATC) program. FIATC is fully compatible with FIAT (version 2.5) but has expanded capabilities to compute the multispecies surface chemistry and ablation rate as part of the surface energy balance. This new methodology eliminates B' tables, provides blown species fractions as a function of time, and enables calculations that would otherwise be impractical (e.g. 4+ dimensional tables) such as pyrolysis and ablation with kinetic rates or unequal diffusion coefficients. Equations and solution procedures are presented, then representative calculations of equilibrium and finite-rate ablation in flight and ground-test environments are discussed.

Remote monitoring of the Gravelly Run thermal plume at Hopewell and the thermal plume at the Surry Nuclear Power Plant on the James River

NASA Technical Reports Server (NTRS)

Talay, T. A.; Sykes, K. W.; Kuo, C. Y.

1979-01-01

On May 17, 1977, a remote sensing experiment was conducted on the James River, Virginia, whereby thermal spectrometer and near-infrared photography data of thermal discharges at Hopewell and the Surry nuclear power plant were obtained by an aircraft for one tidal cycle. These data were used in subsequent investigations into the near field discharge trajectories. For the Gravelly Run thermal plume at Hopewell, several empirical expressions for the plume centerline were evaluated by comparisons of the computed trajectories and those observed in the remote sensing images.

Unsteady motion of laser ablation plume by vortex induced by the expansion of curved shock wave

NASA Astrophysics Data System (ADS)

Tran, D. T.; Mori, K.

2017-02-01

There are a number of industrial applications of laser ablation in a gas atmosphere. When an intense pulsed laser beam is irradiated on a solid surface in the gas atmosphere, the surface material is ablated and expands into the atmosphere. At the same time, a spherical shock wave is launched by the ablation jet to induce the unsteady flow around the target surface. The ablated materials, luminously working as tracer, exhibit strange unsteady motions depending on the experimental conditions. By using a high-speed video camera (HPV-X2), unsteady motion ablated materials are visualized at the frame rate more than 106 fps, and qualitatively characterized.

Ablative thermal management structural material on the hypersonic vehicles

NASA Astrophysics Data System (ADS)

Shortland, H.; Tsai, C.

A hypersonic vehicle is designed to fly at high Mach number in the earth's atmosphere that will result in higher aerodynamic heating loads on specific areas of the vehicle. A thermal protection system is required for these areas that may exceed the operating temperature limit of structural materials. This paper delineates the application of ablative material as the passive type of thermal protection system for the nose or wing leading edges. A simplified quasi-steady-state one-dimensional computer model was developed to evaluate the performance and thermal design of a leading edge. The detailed description of the governing mathematical equations and results are presented. This model provides a quantitative information to support the design estimate, performance optimization, and assess preliminary feasibility of using ablation as a design approach.

Satellite infrared imagery for thermal plume contamination monitoring in coastal ecosystem of Cernavoda NPP

NASA Astrophysics Data System (ADS)

Zoran, M. A.; Zoran, Liviu Florin V.; Dida, Adrian I.

2017-10-01

Satellite remote sensing is an important tool for spatio-temporal analysis and surveillance of NPP environment, thermal heat waste of waters being a major concern in many coastal ecosystems involving nuclear power plants. As a test case the adopted methodology was applied for 700x2 MW Cernavoda nuclear power plant (NPP) located in the South-Eastern part of Romania, which discharges warm water affecting coastal ecology. The thermal plume signatures in the NPP hydrological system have been investigated based on TIR (Thermal Infrared) spectral bands of NOAA AVHRR, Landsat TM/ETM+/OLI, and MODIS Terra/Aqua time series satellite data during 1990-2016 period. If NOAA AVHRR data proved the general pattern and extension of the thermal plume signature in Danube river and Black Sea coastal areas, Landsat TM/ETM and MODIS data used for WST (Water Surface Temperature) change detection, mapping and monitoring provided enhanced information about the plume shape, dimension and direction of dispersion in these waters. Thermal discharge from two nuclear reactors cooling is dissipated as waste heat in Danube-Black -Sea Channel and Danube River. From time-series analysis of satellite data during period 1990-2016 was found that during the winter season thermal plume was localized to an area of a few km of NPP, and the mean temperature difference between the plume and non-plume areas was about 1.7 oC. During summer and fall, derived mean temperature difference between the plume and non-plume areas was of about 1.3°C and thermal plume area was extended up to 5- 10 km far along Danube Black Sea Channel.

Non-Fourier based thermal-mechanical tissue damage prediction for thermal ablation.

PubMed

Li, Xin; Zhong, Yongmin; Smith, Julian; Gu, Chengfan

2017-01-02

Prediction of tissue damage under thermal loads plays important role for thermal ablation planning. A new methodology is presented in this paper by combing non-Fourier bio-heat transfer, constitutive elastic mechanics as well as non-rigid motion of dynamics to predict and analyze thermal distribution, thermal-induced mechanical deformation and thermal-mechanical damage of soft tissues under thermal loads. Simulations and comparison analysis demonstrate that the proposed methodology based on the non-Fourier bio-heat transfer can account for the thermal-induced mechanical behaviors of soft tissues and predict tissue thermal damage more accurately than classical Fourier bio-heat transfer based model.

Thermal-mechanical modeling of laser ablation hybrid machining

NASA Astrophysics Data System (ADS)

Matin, Mohammad Kaiser

2001-08-01

Hard, brittle and wear-resistant materials like ceramics pose a problem when being machined using conventional machining processes. Machining ceramics even with a diamond cutting tool is very difficult and costly. Near net-shape processes, like laser evaporation, produce micro-cracks that require extra finishing. Thus it is anticipated that ceramic machining will have to continue to be explored with new-sprung techniques before ceramic materials become commonplace. This numerical investigation results from the numerical simulations of the thermal and mechanical modeling of simultaneous material removal from hard-to-machine materials using both laser ablation and conventional tool cutting utilizing the finite element method. The model is formulated using a two dimensional, planar, computational domain. The process simulation acronymed, LAHM (Laser Ablation Hybrid Machining), uses laser energy for two purposes. The first purpose is to remove the material by ablation. The second purpose is to heat the unremoved material that lies below the ablated material in order to ``soften'' it. The softened material is then simultaneously removed by conventional machining processes. The complete solution determines the temperature distribution and stress contours within the material and tracks the moving boundary that occurs due to material ablation. The temperature distribution is used to determine the distance below the phase change surface where sufficient ``softening'' has occurred, so that a cutting tool may be used to remove additional material. The model incorporated for tracking the ablative surface does not assume an isothermal melt phase (e.g. Stefan problem) for laser ablation. Both surface absorption and volume absorption of laser energy as function of depth have been considered in the models. LAHM, from the thermal and mechanical point of view is a complex machining process involving large deformations at high strain rates, thermal effects of the laser, removal of

Effect of boundary conditions on thermal plume growth

NASA Astrophysics Data System (ADS)

Kondrashov, A.; Sboev, I.; Rybkin, K.

2016-07-01

We have investigated the influence of boundary conditions on the growth rate of convective plumes. Temperature and rate fields were studied in a rectangular convective cell heated by a spot heater. The results of the full-scale test were compared with the numerical data calculated using the ANSYS CFX software package. The relationship between the heat plume growth rate and heat boundary conditions, the width and height of the cell, size of heater for different kinds of liquid was established.

An algorithm for the detection and characterisation of volcanic plumes using thermal camera imagery

NASA Astrophysics Data System (ADS)

Bombrun, Maxime; Jessop, David; Harris, Andrew; Barra, Vincent

2018-02-01

Volcanic plumes are turbulent mixtures of particles and gas which are injected into the atmosphere during a volcanic eruption. Depending on the intensity of the eruption, plumes can rise from a few tens of metres up to many tens of kilometres above the vent and thus, present a major hazard for the surrounding population. Currently, however, few if any algorithms are available for automated plume tracking and assessment. Here, we present a new image processing algorithm for segmentation, tracking and parameters extraction of convective plume recorded with thermal cameras. We used thermal video of two volcanic eruptions and two plumes simulated in laboratory to develop and test an efficient technique for analysis of volcanic plumes. We validated our method by two different approaches. First, we compare our segmentation method to previously published algorithms. Next, we computed plume parameters, such as height, width and spreading angle at regular intervals of time. These parameters allowed us to calculate an entrainment coefficient and obtain information about the entrainment efficiency in Strombolian eruptions. Our proposed algorithm is rapid, automated while producing better visual outlines compared to the other segmentation algorithms, and provides output that is at least as accurate as manual measurements of plumes.

Ablation Modeling of Ares-I Upper State Thermal Protection System Using Thermal Desktop

NASA Technical Reports Server (NTRS)

Sharp, John R.; Page, Arthur T.

2007-01-01

The thermal protection system (TPS) for the Ares-I Upper Stage will be based on Space Transportation System External Tank (ET) and Solid Rocket Booster (SRB) heritage materials. These TPS materials were qualified via hot gas testing that simulated ascent and re-entry aerothermodynamic convective heating environments. From this data, the recession rates due to ablation were characterized and used in thermal modeling for sizing the thickness required to maintain structural substrate temperatures. At Marshall Space Flight Center (MSFC), the in-house code ABL is currently used to predict TPS ablation and substrate temperatures as a FORTRAN application integrated within SINDA/G. This paper describes a comparison of the new ablation utility in Thermal Desktop and SINDA/FLUINT with the heritage ABL code and empirical test data which serves as the validation of the Thermal Desktop software for use on the design of the Ares-I Upper Stage project.

Thermal Analysis on Plume Heating of the Main Engine on the Crew Exploration Vehicle Service Module

NASA Technical Reports Server (NTRS)

Wang, Xiao-Yen J.; Yuko, James R.

2007-01-01

The crew exploration vehicle (CEV) service module (SM) main engine plume heating is analyzed using multiple numerical tools. The chemical equilibrium compositions and applications (CEA) code is used to compute the flow field inside the engine nozzle. The plume expansion into ambient atmosphere is simulated using an axisymmetric space-time conservation element and solution element (CE/SE) Euler code, a computational fluid dynamics (CFD) software. The thermal analysis including both convection and radiation heat transfers from the hot gas inside the engine nozzle and gas radiation from the plume is performed using Thermal Desktop. Three SM configurations, Lockheed Martin (LM) designed 604, 605, and 606 configurations, are considered. Design of multilayer insulation (MLI) for the stowed solar arrays, which is subject to plume heating from the main engine, among the passive thermal control system (PTCS), are proposed and validated.

Infrared laser ablation of polymeric nanocomposites: A study of surface structure and plume formation

NASA Astrophysics Data System (ADS)

Bartolucci, S. F.; Miller, M. J.; Warrender, J. M.

2016-12-01

The behavior of carbon nanotube composites subjected to laser pulse heating with a 1070 nm variable pulse duration laser has been studied. Previous work has shown that carbon nanotube composites form a protective network on the surface of a composite, which reduces heat input to the underlying polymer and slows mass loss. In this work, we have studied the interaction between the incident laser and the plume formed above the composite. We have correlated these interactions with features observed in the time-resolved mass loss data and confirmed them with observations using high-speed video of the laser irradiations. Beam interactions were studied as a function of laser irradiance and nanotube content. It is shown that beam-plume interactions occur for the carbon nanotube composites and that the interactions occur at shorter pulse durations for increased nanotube content and laser irradiance. When we eliminate beam-plume interaction through alteration of the sample orientation relative to the incident beam, we are able to elucidate the individual contributions of the carbon nanotube surface network and the plume to the observed decrease in mass loss after laser irradiation. We examine the plume content using microscopy and Raman spectroscopy and show that greater beam absorption occurs when there is a higher graphitic content in the plume.

The Thermal Evolution of the Galapagos Mantle Plume: Insights from Al-in-Olivine Thermometry

NASA Astrophysics Data System (ADS)

Trela, J.; Gazel, E.; Sobolev, A. V.; Class, C.; Bizimis, M.; Jicha, B. R.; Batanova, V. G.; Denyer, P.

2016-12-01

The mantle plume hypothesis is widely accepted for the formation of large igneous provinces (LIP) and many ocean island basalts (OIB). Petrologic models support a mantle plume origin by indicating high mantle temperatures (>1500 °C) for some plume-melts relative to melts generated at ambient mid ocean ridge conditions (1350 °C). Mantle plumes forming LIPs and OIBs provide our primary source of information on the geochemical and lithological heterogeneity of the lower mantle. The Galapagos hotspot represents one of the most thermally and geochemically heterogeneous plumes on the planet, sustaining long-lived isotopic and lithological heterogeneity over its 90 Ma evolution. Previous petrologic studies showed that the Galapagos plume secularly cooled over time and that the decrease in the plume's temperature correlates with an increase in a recycled (pyroxenite) component. We used Al-in-olivine thermometry to show that maximum olivine crystallization temperatures confirm secular cooling of the Galapagos plume. Olivines from the early melting stages of the plume at 90 Ma (Caribbean LIP) record the highest crystallization temperatures (1600 °C). Olivines from the current archipelago record the lowest temperatures of only 1300 °C. The largest decrease in temperature occurred between 90 and 70 Ma ( 200 °C decrease) and coincides with the plume head-tail transition. Olivines from the 60-90 Ma-old accreted Galapagos-tracks in Costa Rica and Panama record higher Ni, Fe/Mn, and lower Ca contents than those from the present-day archipelago, indicating a higher abundance of pyroxenite (recycled oceanic crust) entrained in parts of the plume head that melted to form the Caribbean LIP. However, the Galapagos plume was pyroxenite-rich for 40 Ma thus pyroxenite-entrainment goes beyond the plume-tail transition. Our results suggest that hotter regions of the Galapagos plume entrained larger amounts of dense, recycled components due to their greater buoyancy; however, this

Ablation study of tungsten-based nuclear thermal rocket fuel

NASA Astrophysics Data System (ADS)

Smith, Tabitha Elizabeth Rose

The research described in this thesis has been performed in order to support the materials research and development efforts of NASA Marshall Space Flight Center (MSFC), of Tungsten-based Nuclear Thermal Rocket (NTR) fuel. The NTR was developed to a point of flight readiness nearly six decades ago and has been undergoing gradual modification and upgrading since then. Due to the simplicity in design of the NTR, and also in the modernization of the materials fabrication processes of nuclear fuel since the 1960's, the fuel of the NTR has been upgraded continuously. Tungsten-based fuel is of great interest to the NTR community, seeking to determine its advantages over the Carbide-based fuel of the previous NTR programs. The materials development and fabrication process contains failure testing, which is currently being conducted at MSFC in the form of heating the material externally and internally to replicate operation within the nuclear reactor of the NTR, such as with hot gas and RF coils. In order to expand on these efforts, experiments and computational studies of Tungsten and a Tungsten Zirconium Oxide sample provided by NASA have been conducted for this dissertation within a plasma arc-jet, meant to induce ablation on the material. Mathematical analysis was also conducted, for purposes of verifying experiments and making predictions. The computational method utilizes Anisimov's kinetic method of plasma ablation, including a thermal conduction parameter from the Chapman Enskog expansion of the Maxwell Boltzmann equations, and has been modified to include a tangential velocity component. Experimental data matches that of the computational data, in which plasma ablation at an angle shows nearly half the ablation of plasma ablation at no angle. Fuel failure analysis of two NASA samples post-testing was conducted, and suggestions have been made for future materials fabrication processes. These studies, including the computational kinetic model at an angle and the

On the relationship between tectonic plates and thermal mantle plume morphology

NASA Technical Reports Server (NTRS)

Lenardic, A.; Kaula, W. M.

1993-01-01

Models incorporating plate-like behavior, i.e., near uniform surface velocity and deformation concentrated at plate boundaries, into a convective system, heated by a mix of internal and basal heating and allowing for temperature dependent viscosity, were constructed and compared to similar models not possessing plate-like behavior. The simplified numerical models are used to explore how plate-like behavior in a convective system can effect the lower boundary layer from which thermal plumes form. A principal conclusion is that plate-like behavior can significantly increase the temperature drop across the lower thermal boundary layer. This temperature drop affects the morphology of plumes by determining the viscosity drop across the boundary layer. Model results suggest that plumes on planets possessing plate-like behavior, e.g., the Earth, may differ in morphologic type from plumes on planets not possessing plate-like behavior, e.g., Venus and Mars.

Anatomy of a laminar starting thermal plume at high Prandtl number

NASA Astrophysics Data System (ADS)

Davaille, Anne; Limare, Angela; Touitou, Floriane; Kumagai, Ichiro; Vatteville, Judith

2011-02-01

We present an experimental study of the dynamics of a plume generated from a small heat source in a high Prandtl number fluid with a strongly temperature-dependent viscosity. The velocity field was determined with particle image velocimetry, while the temperature field was measured using differential interferometry and thermochromic liquid crystals. The combination of these different techniques run simultaneously allows us to identify the different stages of plume development, and to compare the positions of key-features of the velocity field (centers of rotation, maximum vorticity locations, stagnation points) respective to the plume thermal anomaly, for Prandtl numbers greater than 103. We further show that the thermal structure of the plume stem is well predicted by the constant viscosity model of Batchelor (Q J R Met Soc 80: 339-358, 1954) for viscosity ratios up to 50.

Thermal protection during percutaneous thermal ablation procedures: interest of carbon dioxide dissection and temperature monitoring.

PubMed

Buy, Xavier; Tok, Chung-Hong; Szwarc, Daniel; Bierry, Guillaume; Gangi, Afshin

2009-05-01

Percutaneous image-guided thermal ablation of tumor is widely used, and thermal injury to collateral structures is a known complication of this technique. To avoid thermal damage to surrounding structures, several protection techniques have been reported. We report the use of a simple and effective protective technique combining carbon dioxide dissection and thermocouple: CO(2) displaces the nontarget structures, and its low thermal conductivity provides excellent insulation; insertion of a thermocouple in contact with vulnerable structures achieves continuous thermal monitoring. We performed percutaneous thermal ablation of 37 tumors in 35 patients (4 laser, 10 radiofrequency, and 23 cryoablations) with protection of adjacent vulnerable structures by using CO(2) dissection combined with continuous thermal monitoring with thermocouple. Tumor locations were various (19 intra-abdominal tumors including 4 livers and 9 kidneys, 18 musculoskeletal tumors including 11 spinal tumors). CO(2) volume ranged from 10 ml (epidural space) to 1500 ml (abdominal). Repeated insufflations were performed if necessary, depending on the information given by the thermocouple and imaging control. Dissection with optimal thermal protection was achieved in all cases except two patients where adherences (one postoperative, one arachnoiditis) blocked proper gaseous distribution. No complication referred to this technique was noted. This safe, cost-effective, and simple method increases the safety and the success rate of percutaneous thermal ablation procedures. It also offers the potential to increase the number of tumors that can be treated via a percutaneous approach.

Tectonic plates, D (double prime) thermal structure, and the nature of mantle plumes

NASA Technical Reports Server (NTRS)

Lenardic, A.; Kaula, W. M.

1994-01-01

It is proposed that subducting tectonic plates can affect the nature of thermal mantle plumes by determining the temperature drop across a plume source layer. The temperature drop affects source layer stability and the morphology of plumes emitted from it. Numerical models are presented to demonstrate how introduction of platelike behavior in a convecting temperature dependent medium, driven by a combination of internal and basal heating, can increase the temperature drop across the lower boundary layer. The temperature drop increases dramatically following introduction of platelike behavior due to formation of a cold temperature inversion above the lower boundary layer. This thermal inversion, induced by deposition of upper boundary layer material to the system base, decays in time, but the temperature drop across the lower boundary layer always remains considerably higher than in models lacking platelike behavior. On the basis of model-inferred boundary layer temperature drops and previous studies of plume dynamics, we argue that generally accepted notions as to the nature of mantle plumes on Earth may hinge on the presence of plates. The implication for Mars and Venus, planets apparently lacking plate tectonics, is that mantle plumes of these planets may differ morphologically from those of Earth. A corollary model-based argument is that as a result of slab-induced thermal inversions above the core mantle boundary the lower most mantle may be subadiabatic, on average (in space and time), if major plate reorganization timescales are less than those acquired to diffuse newly deposited slab material.

Meta-analysis of bipolar radiofrequency endometrial ablation versus thermal balloon endometrial ablation for the treatment of heavy menstrual bleeding.

PubMed

Zhai, Yan; Zhang, Zihan; Wang, Wei; Zheng, Tingping; Zhang, Huili

2018-01-01

Heavy menstrual bleeding is a common problem that can severely affect quality of life. To compare bipolar radiofrequency endometrial ablation and thermal balloon ablation for heavy menstrual bleeding in terms of efficacy and health-related quality of life (HRQoL). Online registries were systematically searched using relevant terms without language restriction from inception to November 24, 2016. Randomized control trials or cohort studies of women with heavy menstrual bleeding comparing the efficacy of two treatments were eligible. Data were extracted. Results were expressed as risk ratios (RRs) or weighted mean differences (WMDs) with 95% confidence intervals (CIs). Six studies involving 901 patients were included. Amenorrhea rate at 12 months was significantly higher after bipolar radiofrequency endometrial ablation than after thermal balloon ablation (RR 2.73, 95% CI 2.00-3.73). However, no difference at 12 months was noted for dysmenorrhea (RR 1.04, 95% CI 0.68-1.58) or treatment failure (RR 0.78, 95% CI 0.38-1.60). The only significant difference for HRQoL outcomes was for change in SAQ pleasure score (12 months: WMD -3.51, 95% CI -5.42 to -1.60). Bipolar radiofrequency endometrial ablation and thermal balloon ablation reduce menstrual loss and improve quality of life. However, bipolar radiofrequency endometrial ablation is more effective in terms of amenorrhea rate and SAQ pleasure. © 2017 International Federation of Gynecology and Obstetrics.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2017-09-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-06-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Thermal Ablation of T1c Renal Cell Carcinoma: A Comparative Assessment of Technical Performance, Procedural Outcome, and Safety of Microwave Ablation, Radiofrequency Ablation, and Cryoablation.

PubMed

Zhou, Wenhui; Arellano, Ronald S

2018-04-06

To evaluate perioperative outcomes of thermal ablation with microwave (MW), radiofrequency (RF), and cryoablation for stage T1c renal cell carcinoma (RCC). A retrospective analysis of 384 patients (mean age, 71 y; range, 22-88 y) was performed between October 2006 and October 2016. Mean radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, and location relative to polar lines; preoperative aspects and dimensions used for anatomic classification; and centrality index scores were 6.3, 7.9, and 2.7, respectively. Assessment of pre- and postablation serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate was performed to assess functional outcomes. Linear regression analyses were performed to compare sedation medication dosages among the three treatment cohorts. Univariable and multivariable logistic regression analyses were performed to compare rates of residual disease and complications among treatment modalities. A total of 437 clinical stage T1N0M0 biopsy-proven RCCs measuring 1.2-6.9 cm were treated with computed tomography (CT)-guided MW ablation (n = 44; 10%), RF ablation (n = 347; 79%), or cryoablation (n = 46; 11%). There were no significant differences in patient demographic or tumor characteristics among cohorts. Complication rates and immediate renal function changes were similar among the three ablation modalities (P = .46 and P = .08, respectively). MW ablation was associated with significantly decreased ablation time (P < .05), procedural time (P < .05), and dosage of sedative medication (P < .05) compared with RF ablation and cryoablation. CT-guided percutaneous MW ablation is comparable to RF ablation or cryoablation for the treatment of stage T1N0M0 RCC with regard to treatment response and is associated with shorter treatment times and less sedation than RF ablation or cryoablation. In addition, the safety profile of CT-guided MW ablation is noninferior to those of RF ablation or

ALMA Thermal Observations of a Proposed Plume Source Region on Europa

SciTech Connect

Trumbo, Samantha K.; Brown, Michael E.; Butler, Bryan J.

We present a daytime thermal image of Europa taken with the Atacama Large Millimeter Array. The imaged region includes the area northwest of Pwyll Crater, which is associated with a nighttime thermal excess seen by the Galileo Photopolarimeter Radiometer and with two potential plume detections. We develop a global thermal model of Europa and simulate both the daytime and nighttime thermal emission to determine if the nighttime thermal anomaly is caused by excess endogenic heat flow, as might be expected from a plume source region. We find that the nighttime and daytime brightness temperatures near Pwyll Crater cannot be matchedmore » by including excess heat flow at that location. Rather, we can successfully model both measurements by increasing the local thermal inertia of the surface.« less

Thermal ablation for partial splenectomy hemostasis, spleen trauma, splenic metastasis and hypersplenism.

PubMed

Duan, Ya-Qi; Liang, Ping

2013-05-01

Many studies have been conducted on splenic thermal ablation for partial splenectomy hemostasis, spleen trauma, splenic metastasis and hypersplenism. In this article, we review the evolution and current status of radiofrequency and microwave ablation in the treatment of spleen diseases. All publications from 1990 to 2011 on radiofrequency and microwave ablation for partial splenectomy hemostasis, spleen trauma, splenic metastasis and hypersplenism were retrieved by searching PubMed. Thermal ablation in the spleen for partial splenectomy hemostasis, spleen trauma, splenic metastasis and hypersplenism can preserve part of the spleen and maintain splenic immunologic function. Thermal ablation for assisting hemostasis in partial splenectomy minimizes blood loss during operation. Thermal ablation for spleen trauma reduces the number of splenectomy and the amount of blood transfusion. Thermal ablation for splenic metastasis is minimally invasive and can be done under the guidance of an ultrasound, which helps shorten the recovery time. Thermal ablation for hypersplenism increases platelet (PLT) and white blood cell (WBC) counts and improves liver function. It also helps to maintain splenic immunologic function and even improves splenic immunologic function in the short-term. In conclusion, thermal ablative approaches are promising for partial splenectomy hemostasis, spleen trauma, splenic metastasis and hypersplenism. In order to improve therapeutic effects, directions for future studies may include standardized therapeutic indications, prolonged observation periods and enlarged sample sizes.

Non-Fourier based thermal-mechanical tissue damage prediction for thermal ablation

PubMed Central

Li, Xin; Zhong, Yongmin; Smith, Julian; Gu, Chengfan

2017-01-01

ABSTRACT Prediction of tissue damage under thermal loads plays important role for thermal ablation planning. A new methodology is presented in this paper by combing non-Fourier bio-heat transfer, constitutive elastic mechanics as well as non-rigid motion of dynamics to predict and analyze thermal distribution, thermal-induced mechanical deformation and thermal-mechanical damage of soft tissues under thermal loads. Simulations and comparison analysis demonstrate that the proposed methodology based on the non-Fourier bio-heat transfer can account for the thermal-induced mechanical behaviors of soft tissues and predict tissue thermal damage more accurately than classical Fourier bio-heat transfer based model. PMID:27690290

Thermal particle image velocity estimation of fire plume flow

Treesearch

Xiangyang Zhou; Lulu Sun; Shankar Mahalingam; David R. Weise

2003-01-01

For the purpose of studying wildfire spread in living vegetation such as chaparral in California, a thermal particle image velocity (TPIV) algorithm for nonintrusively measuring flame gas velocities through thermal infrared (IR) imagery was developed. By tracing thermal particles in successive digital IR images, the TPIV algorithm can estimate the velocity field in a...

Two-Dimensional Finite Element Ablative Thermal Response Analysis of an Arcjet Stagnation Test

NASA Technical Reports Server (NTRS)

Dec, John A.; Laub, Bernard; Braun, Robert D.

2011-01-01

The finite element ablation and thermal response (FEAtR, hence forth called FEAR) design and analysis program simulates the one, two, or three-dimensional ablation, internal heat conduction, thermal decomposition, and pyrolysis gas flow of thermal protection system materials. As part of a code validation study, two-dimensional axisymmetric results from FEAR are compared to thermal response data obtained from an arc-jet stagnation test in this paper. The results from FEAR are also compared to the two-dimensional axisymmetric computations from the two-dimensional implicit thermal response and ablation program under the same arcjet conditions. The ablating material being used in this arcjet test is phenolic impregnated carbon ablator with an LI-2200 insulator as backup material. The test is performed at the NASA, Ames Research Center Interaction Heating Facility. Spatially distributed computational fluid dynamics solutions for the flow field around the test article are used for the surface boundary conditions.

Artificial ascites and pneumoperitoneum to facilitate thermal ablation of liver tumors: a pictorial essay.

PubMed

Bhagavatula, Sharath K; Chick, Jeffrey F B; Chauhan, Nikunj R; Shyn, Paul B

2017-02-01

Image-guided percutaneous thermal ablation is increasingly utilized in the treatment of hepatic malignancies. Peripherally located hepatic tumors can be difficult to access or located adjacent to critical structures that can be injured. As a result, ablation of peripheral tumors may be avoided or may be performed too cautiously, leading to inadequate ablation coverage. In these cases, separating the tumor from adjacent critical structures can increase the efficacy and safety of procedures. Artificial ascites and artificial pneumoperitoneum are techniques that utilize fluid and gas, respectively, to insulate critical structures from the thermal ablation zone. Induction of artificial ascites and artificial pneumoperitoneum can enable complete ablation of otherwise inaccessible hepatic tumors, improve tumor visualization, minimize unintended thermal injury to surrounding organs, and reduce post-procedural pain. This pictorial essay illustrates and discusses the proper technique and clinical considerations for successful artificial ascites and pneumoperitoneum creation to facilitate safe peripheral hepatic tumor ablation.

Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

PubMed Central

Lee, Jeong Hyun; Valcavi, Roberto; Pacella, Claudio M.; Rhim, Hyunchul; Na, Dong Gyu

2011-01-01

Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation. PMID:21927553

Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy

NASA Technical Reports Server (NTRS)

deBoer, Gary; Scott, Carl

2003-01-01

Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal

Co:MgF2 laser ablation of tissue: effect of wavelength on ablation threshold and thermal damage.

PubMed

Schomacker, K T; Domankevitz, Y; Flotte, T J; Deutsch, T F

1991-01-01

The wavelength dependence of the ablation threshold of a variety of tissues has been studied by using a tunable pulsed Co:MgF2 laser to determine how closely it tracks the optical absorption length of water. The Co:MgF2 laser was tuned between 1.81 and 2.14 microns, a wavelength region in which the absorption length varies by a decade. For soft tissues the ablation threshold tracks the optical absorption length; for bone there is little wavelength dependence, consistent with the low water content of bone. Thermal damage vs. wavelength was also studied for cornea and bone. Thermal damage to cornea has a weak wavelength dependence, while that to bone shows little wavelength dependence. Framing-camera pictures of the ablation of both cornea and liver show explosive removal of material, but differ as to the nature of the explosion.

Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets.

PubMed

Chang, Nan; Lu, Shukuan; Qin, Dui; Xu, Tianqi; Han, Meng; Wang, Supin; Wan, Mingxi

2018-07-01

A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration. Copyright © 2018. Published by Elsevier B.V.

Thermal infrared images to quantify thermal ablation effects of acid and base on target tissues

NASA Astrophysics Data System (ADS)

Liu, Ran; Wang, Jia; Liu, Jing

2015-07-01

Hyperthermia (42-46°C), treatment of tumor tissue through elevated temperature, offers several advantages including high cost-effectiveness, highly targeted ablation and fewer side effects and hence higher safety level over traditional therapies such as chemotherapy and radiotherapy. Recently, hyperthermia using heat release through exothermic acid-base neutralization comes into view owing to its relatively safe products of salt and water and highly confined ablation. However, lack of quantitative understanding of the spatial and temporal temperature profiles that are produced by simultaneous diffusion of liquid chemical and its chemical reaction within tumor tissue impedes the application of this method. This article is dedicated to quantify thermal ablation effects of acid and base both individually and as in neutralization via infrared captured thermal images. A theoretical model is used to approximate specific heat absorption rate (SAR) based on experimental measurements that contrast two types of tissue, normal pork and pig liver. According to the computation, both pork and liver tissue has a higher ability in absorbing hydrochloric acid (HCl) than sodium hydroxide, hence suggesting that a reduced dosage for HCl is appropriate in a surgery. The heating effect depends heavily on the properties of tissue types and amount of chemical reagents administered. Given thermal parameters such as SAR for different tissues, a computational model can be made in predicting temperature transitions which will be helpful in planning and optimizing surgical hyperthermia procedures.

Thermal infrared images to quantify thermal ablation effects of acid and base on target tissues

SciTech Connect

Liu, Ran, E-mail: jliubme@tsinghua.edu.cn, E-mail: liuran@tsinghua.edu.cn; Liu, Jing, E-mail: jliubme@tsinghua.edu.cn, E-mail: liuran@tsinghua.edu.cn; Wang, Jia

Hyperthermia (42-46°C), treatment of tumor tissue through elevated temperature, offers several advantages including high cost-effectiveness, highly targeted ablation and fewer side effects and hence higher safety level over traditional therapies such as chemotherapy and radiotherapy. Recently, hyperthermia using heat release through exothermic acid-base neutralization comes into view owing to its relatively safe products of salt and water and highly confined ablation. However, lack of quantitative understanding of the spatial and temporal temperature profiles that are produced by simultaneous diffusion of liquid chemical and its chemical reaction within tumor tissue impedes the application of this method. This article is dedicated tomore » quantify thermal ablation effects of acid and base both individually and as in neutralization via infrared captured thermal images. A theoretical model is used to approximate specific heat absorption rate (SAR) based on experimental measurements that contrast two types of tissue, normal pork and pig liver. According to the computation, both pork and liver tissue has a higher ability in absorbing hydrochloric acid (HCl) than sodium hydroxide, hence suggesting that a reduced dosage for HCl is appropriate in a surgery. The heating effect depends heavily on the properties of tissue types and amount of chemical reagents administered. Given thermal parameters such as SAR for different tissues, a computational model can be made in predicting temperature transitions which will be helpful in planning and optimizing surgical hyperthermia procedures.« less

A computer program for thermal radiation from gaseous rocket exhuast plumes (GASRAD)

NASA Technical Reports Server (NTRS)

Reardon, J. E.; Lee, Y. C.

1979-01-01

A computer code is presented for predicting incident thermal radiation from defined plume gas properties in either axisymmetric or cylindrical coordinate systems. The radiation model is a statistical band model for exponential line strength distribution with Lorentz/Doppler line shapes for 5 gaseous species (H2O, CO2, CO, HCl and HF) and an appoximate (non-scattering) treatment of carbon particles. The Curtis-Godson approximation is used for inhomogeneous gases, but a subroutine is available for using Young's intuitive derivative method for H2O with Lorentz line shape and exponentially-tailed-inverse line strength distribution. The geometry model provides integration over a hemisphere with up to 6 individually oriented identical axisymmetric plumes, a single 3-D plume, Shading surfaces may be used in any of 7 shapes, and a conical limit may be defined for the plume to set individual line-of-signt limits. Intermediate coordinate systems may specified to simplify input of plumes and shading surfaces.

Multispectral Thermal Infrared Mapping of Sulfur Dioxide Plumes: A Case Study from the East Rift Zone of Kilauea Volcano, Hawaii

NASA Technical Reports Server (NTRS)

Realmuto, V. J.; Sutton, A. J.; Elias, T.

1996-01-01

The synoptic perspective and rapid mode of data acquisition provided by remote sensing are well-suited for the study of volcanic SO2 plumes. In this paper we describe a plume-mapping procedure that is based on image data acquired with NASA's airborne Thermal Infrared Multispectral Scanner (TIMS).

Improving Thermal Ablation Delineation With Electrode Vibration Elastography Using a Bidirectional Wave Propagation Assumption

PubMed Central

DeWall, Ryan J.; Varghese, Tomy

2013-01-01

Thermal ablation procedures are commonly used to treat hepatic cancers and accurate ablation representation on shear wave velocity images is crucial to ensure complete treatment of the malignant target. Electrode vibration elastography is a shear wave imaging technique recently developed to monitor thermal ablation extent during treatment procedures. Previous work has shown good lateral boundary delineation of ablated volumes, but axial delineation was more ambiguous, which may have resulted from the assumption of lateral shear wave propagation. In this work, we assume both lateral and axial wave propagation and compare wave velocity images to those assuming only lateral shear wave propagation in finite element simulations, tissue-mimicking phantoms, and bovine liver tissue. Our results show that assuming bidirectional wave propagation minimizes artifacts above and below ablated volumes, yielding a more accurate representation of the ablated region on shear wave velocity images. Area overestimation was reduced from 13.4% to 3.6% in a stiff-inclusion tissue-mimicking phantom and from 9.1% to 0.8% in a radio-frequency ablation in bovine liver tissue. More accurate ablation representation during ablation procedures increases the likelihood of complete treatment of the malignant target, decreasing tumor recurrence. PMID:22293748

Improving thermal ablation delineation with electrode vibration elastography using a bidirectional wave propagation assumption.

PubMed

DeWall, Ryan J; Varghese, Tomy

2012-01-01

Thermal ablation procedures are commonly used to treat hepatic cancers and accurate ablation representation on shear wave velocity images is crucial to ensure complete treatment of the malignant target. Electrode vibration elastography is a shear wave imaging technique recently developed to monitor thermal ablation extent during treatment procedures. Previous work has shown good lateral boundary delineation of ablated volumes, but axial delineation was more ambiguous, which may have resulted from the assumption of lateral shear wave propagation. In this work, we assume both lateral and axial wave propagation and compare wave velocity images to those assuming only lateral shear wave propagation in finite element simulations, tissue-mimicking phantoms, and bovine liver tissue. Our results show that assuming bidirectional wave propagation minimizes artifacts above and below ablated volumes, yielding a more accurate representation of the ablated region on shear wave velocity images. Area overestimation was reduced from 13.4% to 3.6% in a stiff-inclusion tissue-mimicking phantom and from 9.1% to 0.8% in a radio-frequency ablation in bovine liver tissue. More accurate ablation representation during ablation procedures increases the likelihood of complete treatment of the malignant target, decreasing tumor recurrence. © 2012 IEEE

Thermal Testing of Ablators in the NASA Johnson Space Center Radiant Heat Test Facility

NASA Technical Reports Server (NTRS)

Del Papa, Steven; Milhoan, Jim; Remark, Brian; Suess, Leonard

2016-01-01

A spacecraft's thermal protection system (TPS) is required to survive the harsh environment experienced during reentry. Accurate thermal modeling of the TPS is required to since uncertainties in the thermal response result in higher design margins and an increase in mass. The Radiant Heat Test Facility (RHTF) located at the NASA Johnson Space Center (JSC) replicates the reentry temperatures and pressures on system level full scale TPS test models for the validation of thermal math models. Reusable TPS, i.e. tile or reinforced carbon-carbon (RCC), have been the primary materials tested in the past. However, current capsule designs for MPCV and commercial programs have required the use of an ablator TPS. The RHTF has successfully completed a pathfinder program on avcoat ablator material to demonstrate the feasibility of ablator testing. The test results and corresponding ablation analysis results are presented in this paper.

Effect of the Temperature-Emissivity Contrast on the Chemical Signal for Gas Plume Detection Using Thermal Image Data

PubMed Central

Walsh, Stephen; Chilton, Larry; Tardiff, Mark; Metoyer, Candace

2008-01-01

Detecting and identifying weak gaseous plumes using thermal imaging data is complicated by many factors. These include variability due to atmosphere, ground and plume temperature, and background clutter. This paper presents an analysis of one formulation of the physics-based radiance model, which describes at-sensor observed radiance. The background emissivity and plume/ground temperatures are isolated, and their effects on chemical signal are described. This analysis shows that the plume's physical state, emission or absorption, is directly dependent on the background emissivity and plume/ground temperatures. It then describes what conditions on the background emissivity and plume/ground temperatures have inhibiting or amplifying effects on the chemical signal. These claims are illustrated by analyzing synthetic hyperspectral imaging data with the adaptive matched filter using two chemicals and three distinct background emissivities. PMID:27873881

Thermal modeling of lesion growth with radiofrequency ablation devices

PubMed Central

Chang, Isaac A; Nguyen, Uyen D

2004-01-01

Background Temperature is a frequently used parameter to describe the predicted size of lesions computed by computational models. In many cases, however, temperature correlates poorly with lesion size. Although many studies have been conducted to characterize the relationship between time-temperature exposure of tissue heating to cell damage, to date these relationships have not been employed in a finite element model. Methods We present an axisymmetric two-dimensional finite element model that calculates cell damage in tissues and compare lesion sizes using common tissue damage and iso-temperature contour definitions. The model accounts for both temperature-dependent changes in the electrical conductivity of tissue as well as tissue damage-dependent changes in local tissue perfusion. The data is validated using excised porcine liver tissues. Results The data demonstrate the size of thermal lesions is grossly overestimated when calculated using traditional temperature isocontours of 42°C and 47°C. The computational model results predicted lesion dimensions that were within 5% of the experimental measurements. Conclusion When modeling radiofrequency ablation problems, temperature isotherms may not be representative of actual tissue damage patterns. PMID:15298708

Infrasonic ray tracing applied to small-scale atmospheric structures: thermal plumes and updrafts/downdrafts.

PubMed

Jones, R Michael; Bedard, Alfred J

2015-02-01

A ray-tracing program is used to estimate the refraction of infrasound by the vertical structure of the atmosphere in thermal plumes, showing only weak effects, as well as in updrafts and downdrafts, which can act as vertical wave guides. Thermal plumes are ubiquitous features of the daytime atmospheric boundary layer. The effects of thermal plumes on lower frequency sound propagation are minor with the exception of major events, such as volcanoes, forest fires, or industrial explosions where quite strong temperature gradients are involved. On the other hand, when strong, organized vertical flows occur (e.g., in mature thunderstorms and microbursts), there are significant effects. For example, a downdraft surrounded by an updraft focuses sound as it travels upward, and defocuses sound as it travels downward. Such propagation asymmetry may help explain observations that balloonists can hear people on the ground; but conversely, people on the ground cannot hear balloonists aloft. These results are pertinent for those making surface measurements from acoustic sources aloft, as well as for measurements of surface sound sources using elevated receivers.

Effect of thermal diffusion on the stability of strongly tilted mantle plume tails

NASA Astrophysics Data System (ADS)

Kerr, R. C.; MéRiaux, C.; Lister, J. R.

2008-09-01

The effect of thermal diffusion on the stability of strongly tilted mantle plume tails is explored by investigating experimentally and numerically the gravitational instability of a rising horizontal cylindrical region of buoyant viscous fluid. At large viscosity ratios, we find that the instability is unaffected by diffusion when the Rayleigh number Ra is greater than about 300. When Ra is less than 300, diffusion significantly increases the time for instability, as the rising fluid region needs to grow substantially by entrainment before it becomes unstable. When Ra is less than about 140 and the rise height available H is less than about 40 times the cylinder radius, the rising region of fluid is unable to grow sufficiently and instability is prevented. When our results are applied to the Earth, we predict that thermal diffusion will stabilize plume tails in both the upper and lower mantle. We also predict that some of the buoyancy flux in mantle plumes is lost during ascent to form downstream thermal wakes in any larger-scale mantle flow.

Simulation of regimes of convection and plume dynamics by the thermal Lattice Boltzmann Method

NASA Astrophysics Data System (ADS)

Mora, Peter; Yuen, David A.

2018-02-01

We present 2D simulations using the Lattice Boltzmann Method (LBM) of a fluid in a rectangular box being heated from below, and cooled from above. We observe plumes, hot narrow upwellings from the base, and down-going cold chutes from the top. We have varied both the Rayleigh numbers and the Prandtl numbers respectively from Ra = 1000 to Ra =1010 , and Pr = 1 through Pr = 5 ×104 , leading to Rayleigh-Bénard convection cells at low Rayleigh numbers through to vigorous convection and unstable plumes with pronounced vortices and eddies at high Rayleigh numbers. We conduct simulations with high Prandtl numbers up to Pr = 50, 000 to simulate in the inertial regime. We find for cases when Pr ⩾ 100 that we obtain a series of narrow plumes of upwelling fluid with mushroom heads and chutes of downwelling fluid. We also present simulations at a Prandtl number of 0.7 for Rayleigh numbers varying from Ra =104 through Ra =107.5 . We demonstrate that the Nusselt number follows power law scaling of form Nu ∼Raγ where γ = 0.279 ± 0.002 , which is consistent with published results of γ = 0.281 in the literature. These results show that the LBM is capable of reproducing results obtained with classical macroscopic methods such as spectral methods, and demonstrate the great potential of the LBM for studying thermal convection and plume dynamics relevant to geodynamics.

Application of satellite infrared data for mapping of thermal plume contamination in coastal ecosystem of Korea.

PubMed

Ahn, Yu-Hwan; Shanmugam, Palanisamy; Lee, Jae-Hak; Kang, Yong Q

2006-03-01

The 5900 MW Younggwang nuclear power station on the west coast of Korea discharges warm water affecting coastal ecology [KORDI report (2003). Wide area observation of the impact of the operation of Younggwang nuclear power plant 5 and 6, No. BSPI 319-00-1426-3, KORDI, Seoul, Korea]. Here the spatial and temporal characteristics of the thermal plume signature of warm water are reported from a time series (1985-2003) of space-borne, thermal infrared data from Landsat and National Oceanic and Atmospheric Administration (NOAA) satellites. Sea surface temperature (SST) were characterized using advanced very high resolution radiometer data from the NOAA satellites. These data demonstrated the general pattern and extension of the thermal plume signature in the Younggwang coastal areas. In contrast, the analysis of SST from thematic mapper data using the Landsat-5 and 7 satellites provided enhanced information about the plume shape, dimension and direction of dispersion in these waters. The thermal plume signature was detected from 70 to 100 km to the south of the discharge during the summer monsoon and 50 to 70 km to the northwest during the winter monsoon. The mean detected plume temperature was 28 degrees C in summer and 12 degrees C in winter. The DeltaT varied from 2 to 4 degrees C in winter and 2 degrees C in summer. These values are lower than the re-circulating water temperature (6-9 degrees C). In addition the temperature difference between tidal flats and offshore (SSTtidal flats - SSToffsore) was found to vary from 5.4 to 8.5 degrees C during the flood tides and 3.5 degrees C during the ebb tide. The data also suggest that water heated by direct solar radiation on the tidal flats during the flood tides might have been transported offshore during the ebb tide. Based on these results we suggest that there is an urgent need to protect the health of Younggwang coastal marine ecosystem from the severe thermal impact by the large quantity of warm water discharged from

A New GPU-Enabled MODTRAN Thermal Model for the PLUME TRACKER Volcanic Emission Analysis Toolkit

NASA Astrophysics Data System (ADS)

Acharya, P. K.; Berk, A.; Guiang, C.; Kennett, R.; Perkins, T.; Realmuto, V. J.

2013-12-01

Real-time quantification of volcanic gaseous and particulate releases is important for (1) recognizing rapid increases in SO2 gaseous emissions which may signal an impending eruption; (2) characterizing ash clouds to enable safe and efficient commercial aviation; and (3) quantifying the impact of volcanic aerosols on climate forcing. The Jet Propulsion Laboratory (JPL) has developed state-of-the-art algorithms, embedded in their analyst-driven Plume Tracker toolkit, for performing SO2, NH3, and CH4 retrievals from remotely sensed multi-spectral Thermal InfraRed spectral imagery. While Plume Tracker provides accurate results, it typically requires extensive analyst time. A major bottleneck in this processing is the relatively slow but accurate FORTRAN-based MODTRAN atmospheric and plume radiance model, developed by Spectral Sciences, Inc. (SSI). To overcome this bottleneck, SSI in collaboration with JPL, is porting these slow thermal radiance algorithms onto massively parallel, relatively inexpensive and commercially-available GPUs. This paper discusses SSI's efforts to accelerate the MODTRAN thermal emission algorithms used by Plume Tracker. Specifically, we are developing a GPU implementation of the Curtis-Godson averaging and the Voigt in-band transmittances from near line center molecular absorption, which comprise the major computational bottleneck. The transmittance calculations were decomposed into separate functions, individually implemented as GPU kernels, and tested for accuracy and performance relative to the original CPU code. Speedup factors of 14 to 30× were realized for individual processing components on an NVIDIA GeForce GTX 295 graphics card with no loss of accuracy. Due to the separate host (CPU) and device (GPU) memory spaces, a redesign of the MODTRAN architecture was required to ensure efficient data transfer between host and device, and to facilitate high parallel throughput. Currently, we are incorporating the separate GPU kernels into a

Analysis of internal ablation for the thermal control of aerospace vehicles

NASA Technical Reports Server (NTRS)

Camberos, Jose A.; Roberts, Leonard

1989-01-01

A new method of thermal protection for transatmospheric vehicles is introduced. The method involves the combination of radiation, ablation and transpiration cooling. By placing an ablating material behind a fixed-shape, porous outer shield, the effectiveness of transpiration cooling is made possible while retaining the simplicity of a passive mechanism. A simplified one-dimensional approach is used to derive the governing equations. Reduction of these equations to non-dimensional form yields two parameters which characterize the thermal protection effectiveness of the shield and ablator combination for a given trajectory. The non-dimensional equations are solved numerically for a sample trajectory corresponding to glide re-entry. Four typical ablators are tested and compared with results obtained by using the thermal properties of water. For the present level of analysis, the numerical computations adequately support the analytical model.

Thyroid tissue: US-guided percutaneous laser thermal ablation.

PubMed

Pacella, Claudio Maurizio; Bizzarri, Giancarlo; Spiezia, Stefano; Bianchini, Antonio; Guglielmi, Rinaldo; Crescenzi, Anna; Pacella, Sara; Toscano, Vincenzo; Papini, Enrico

2004-07-01

To evaluate in vivo the safety and effectiveness of percutaneous laser thermal ablation (LTA) in the debulking of thyroid lesions. Twenty-five adult patients at poor surgical risk with cold nodules (n = 8), autonomously hyperfunctioning thyroid nodules (n = 16), or anaplastic carcinoma (n = 1) underwent LTA. One to four 21-gauge spinal needles were inserted with ultrasonographic (US) guidance into the thyroid lesions. A 300-microm-diameter quartz optical fiber was advanced through the sheath of the needle. Nd:YAG laser was used with output power of 3-5 W. Side effects, complications, and clinical and hormonal changes were evaluated at the end of LTA and during follow-up. Linear regression analysis was used to investigate the correlation between energy delivered and reduction in nodule volume. Volume of induced necrosis and reduction in nodule volume were assessed with US or computed tomography. LTA was performed without difficulties in 76 LTA sessions. After treatment with 5 W, two patients experienced mild dysphonia, which resolved after 48 hours and 2 months. Improvement of local compression symptoms was experienced by 12 of 14 (86%) patients. Thyroid-stimulating hormone (TSH) was detectable in five of 16 (31%) patients with hyperfunctioning nodules at 6 months after LTA. Volume of induced necrosis ranged from 0.8 to 3.9 mL per session. Anaplastic carcinoma treated with four fibers yielded 32.0 mL of necrosis. Echo structure and baseline volume did not influence response. Energy load and reduction in nodule volume were significantly correlated (r(2) =.75, P <.001). Mean nodule volume reduction at 6 months in hyperfunctioning nodules was 3.3 mL +/- 2.8 (62% +/- 21.4 [SD]) and in cold nodules was 7.7 mL +/- 7.5 (63% +/- 13.8). LTA may be a therapeutic tool for highly selected problems in the treatment of thyroid lesions. Copyright RSNA, 2004

Basaltic thermals and Subplinian plumes: Constraints from acoustic measurements at Shishaldin volcano, Alaska

USGS Publications Warehouse

Vergniolle, Sylvie; Caplan-Auerbach, Jacqueline

2006-01-01

The 1999 basaltic eruption of Shishaldin volcano (Alaska, USA) included both Strombolian and Subplinian activity, as well as a “pre-Subplinian” phase interpreted as the local coalescence within a long foam in the conduit. Although few visual observations were made of the eruption, a great deal of information regarding gas velocity, gas flux at the vent and plume height may be inferred by using acoustic recordings of the eruption. By relating acoustic power to gas velocity, a time series of gas velocity is calculated for the Subplinian and pre-Subplinian phases. These time series show trends in gas velocity that are interpreted as plumes or, for those signals lasting only a short time, thermals. The Subplinian phase is shown to be composed of a thermal followed by five plumes with a total expelled gas volume of ≈1.5×107m3">≈1.5×107m3.The initiation of the Subplinian activity is probably related to the arrival of a large overpressurised bubble close to the top of the magma column. A gradual increase in low-frequency (0.01–0.5 Hz) signal prior to this “trigger bubble” may be due to the rise of the bubble in the conduit. This delay corresponds to a reservoir located at ≈3.9 km below the surface, in good agreement with studies on other volcanoes.The presence of two thermal phases is also identified in the middle of the pre-Subplinian phase with a total gas release of ≈4.3×106m3">≈4.3×106m3 and ≈3.6×106m3">≈3.6×106m3. Gas velocity at the vent is found to be ≈82m.s−1">≈82m.s−1 and ≈90m.s−1">≈90m.s−1 for the Subplinian plumes and the pre-Subplinian thermals respectively.The agreement is very good between estimates of the gas flux from modelling the plume height and those obtained from acoustic measurements, leading to a new method by which eruption physical parameters may be quantified. Furthermore, direct measurements of gas velocity can be used for better estimates of the SO2">SO2 flux released during the eruption.

Application of Landsat Thematic Mapper data for coastal thermal plume analysis at Diablo Canyon

NASA Technical Reports Server (NTRS)

Gibbons, D. E.; Wukelic, G. E.; Leighton, J. P.; Doyle, M. J.

1989-01-01

The possibility of using Landsat Thematic Mapper (TM) thermal data to derive absolute temperature distributions in coastal waters that receive cooling effluent from a power plant is demonstrated. Landsat TM band 6 (thermal) data acquired on June 18, 1986, for the Diablo Canyon power plant in California were compared to ground truth temperatures measured at the same time. Higher-resolution band 5 (reflectance) data were used to locate power plant discharge and intake positions and identify locations of thermal pixels containing only water, no land. Local radiosonde measurements, used in LOWTRAN 6 adjustments for atmospheric effects, produced corrected ocean surface radiances that, when converted to temperatures, gave values within approximately 0.6 C of ground truth. A contour plot was produced that compared power plant plume temperatures with those of the ocean and coastal environment. It is concluded that Landsat can provide good estimates of absolute temperatures of the coastal power plant thermal plume. Moreover, quantitative information on ambient ocean surface temperature conditions (e.g., upwelling) may enhance interpretation of numerical model prediction.

Three-Dimensional Finite Element Ablative Thermal Response and Thermostructural Design of Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Dec, John A.; Braun, Robert D.

2011-01-01

A finite element ablation and thermal response program is presented for simulation of three-dimensional transient thermostructural analysis. The three-dimensional governing differential equations and finite element formulation are summarized. A novel probabilistic design methodology for thermal protection systems is presented. The design methodology is an eight step process beginning with a parameter sensitivity study and is followed by a deterministic analysis whereby an optimum design can determined. The design process concludes with a Monte Carlo simulation where the probabilities of exceeding design specifications are estimated. The design methodology is demonstrated by applying the methodology to the carbon phenolic compression pads of the Crew Exploration Vehicle. The maximum allowed values of bondline temperature and tensile stress are used as the design specifications in this study.

Plume Tracker: A New Toolkit for the Mapping of Volcanic Plumes with Multispectral Thermal Infrared Remote Sensing

NASA Astrophysics Data System (ADS)

Realmuto, V. J.; Baxter, S.; Webley, P. W.

2011-12-01

Plume Tracker is the next generation of interactive plume mapping tools pioneered by MAP_SO2. First developed in 1995, MAP_SO2 has been used to study plumes at a number of volcanoes worldwide with data acquired by both airborne and space-borne instruments. The foundation of these tools is a radiative transfer (RT) model, based on MODTRAN, which we use as the forward model for our estimation of ground temperature and sulfur dioxide concentration. Plume Tracker retains the main functions of MAP_SO2, providing interactive tools to input radiance measurements and ancillary data, such as profiles of atmospheric temperature and humidity, to the retrieval procedure, generating the retrievals, and visualizing the resulting retrievals. Plume Tracker improves upon MAP_SO2 in the following areas: (1) an RT model based on an updated version of MODTRAN, (2) a retrieval procedure based on maximizing the vector projection of model spectra onto observed spectra, rather than minimizing the least-squares misfit between the model and observed spectra, (3) an ability to input ozone profiles to the RT model, (4) increased control over the vertical distribution of the atmospheric gas species used in the model, (5) a standard programmatic interface to the RT model code, based on the Component Object Model (COM) interface, which will provide access to any programming language that conforms to the COM standard, and (6) a new binning algorithm that decreases running time by exploiting spatial redundancy in the radiance data. Based on our initial testing, the binning algorithm can reduce running time by an order of magnitude. The Plume Tracker project is a collaborative effort between the Jet Propulsion Laboratory and Geophysical Institute (GI) of the University of Alaska-Fairbanks. Plume Tracker is integrated into the GI's operational plume dispersion modeling system and will ingest temperature and humidity profiles generated by the Weather Research and Forecasting model, together with

The thermal and mechanical properties of a low density elastomeric ablation material

NASA Technical Reports Server (NTRS)

Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

1973-01-01

Thermal and mechanical properties data were obtained for a low density elastomeric resin based ablation material with phenolic-glass honeycomb reinforcement. Data were obtained for the material in the charred and uncharred state. Ablation material specimens were charred in a laboratory furnace at temperatures in the range from 600 K to 1700 K to obtain char specimens representative of the ablation char layer formed during reentry. These specimens were then used to obtain effective thermal conductivity, heat capacity, porosity, and permeability data at the char formation temperature. This provided a boxing of the data which enables the prediction of the transient response of the material during ablation. Limited comparisons were made between the furnace charred specimens and specimens which had been exposed to simulated reentry conditions.

Response Modeling of Lightweight Charring Ablators and Thermal Radiation Testing Results

NASA Technical Reports Server (NTRS)

Congdon, William M.; Curry, Donald M.; Rarick, Douglas A.; Collins, Timothy J.

2003-01-01

Under NASA's In-Space Propulsion/Aerocapture Program, ARA conducted arc-jet and thermal-radiation ablation test series in 2003 for advanced development, characterization, and response modeling of SRAM-20, SRAM-17, SRAM-14, and PhenCarb-20 ablators. Testing was focused on the future Titan Explorer mission. Convective heating rates (CW) were as high as 153 W/sq cm in the IHF and radiation rates were 100 W/sq cm in the Solar Tower Facility. The ablators showed good performance in the radiation environment without spallation, which was initially a concern, but they also showed higher in-depth temperatures when compared to analytical predictions based on arc-jet thermal-ablation response models. More testing in 2003 is planned in both of these facility to generate a sufficient data base for Titan TPS engineering.

Microwave thermal ablation of spinal metastatic bone tumors.

PubMed

Kastler, Adrian; Alnassan, Hussein; Aubry, Sébastien; Kastler, Bruno

2014-09-01

To assess feasibility, safety, and efficacy of microwave ablation of spinal metastatic bone tumors. Retrospective study of 17 patients with 20 spinal metastatic tumors treated with microwave ablation under computed tomographic guidance between March 2011 and August 2013 was performed. Ablations were performed under local anesthesia and nitrous oxide ventilation. Lesions were lumbar (n = 10), sacral (n = 7), and thoracic (n = 3) in location. Primary neoplastic sites were lung (n = 9), prostate (n = 4), kidney (n = 6), and uterus (n = 1). Adjunct cementoplasty was performed in nine cases, and a temperature-monitoring device was used in four cases. Procedure effectiveness was evaluated by visual analog scale (VAS) during a 6-month follow-up. Patient medical records were reviewed, and demographic and clinical data, tumor characteristics, and information on pain were assessed. Mean ablation time was 4.4 minutes ± 2.7 (range, 1-8 min), with an average of 3.8 cycles per ablation at 60 W (range, 30-70 W). The preprocedure mean VAS score was 7.4 ± 1.2 (range, 6-9). Pain relief was achieved in all but one patient. Follow-up VAS scores were as follows: day 0, 1.3 ± 1.8 (P < .001); day 7, 1.6 ± 1.7 (P < .001); month 1, 1.9 ± 1.6 (P < .001); month 3, 2.2 ± 1.5 (P < .001); and month 6, 2.3 ± 1.4 (P < .01). No complications were noted. Microwave ablation appears to be feasible, safe, and an effective treatment of painful refractory spinal metastases and may be considered as a potential alternative percutaneous technique in the management of spinal metastases. Copyright © 2014 SIR. Published by Elsevier Inc. All rights reserved.

Microwave endometrial ablation versus thermal balloon endometrial ablation (MEATBall): 5-year follow up of a randomised controlled trial.

PubMed

Sambrook, A M; Elders, A; Cooper, K G

2014-05-01

To compare long-term outcomes following microwave endometrial ablation (MEA™) and thermal balloon ablation (TBall). Follow up of a prospective, double-blind randomised controlled trial at 5 years. A teaching hospital in the UK. A total of 320 women eligible for and requesting endometrial ablation. Eligible women were randomised in a 1:1 ratio to undergo MEA or Tball. Postal questionnaires were sent to participants at a minimum of 5 years postoperatively to determine satisfaction with outcome, menstrual status, bleeding scores and quality of life measurement. Subsequent surgery was ascertained from the women and the hospital operative database. The primary outcome measure was overall satisfaction with treatment. Secondary outcomes included evaluation of menstrual loss, change in quality of life scores and subsequent surgery. Of the women originally randomised 217/314 (69.1%) returned questionnaires. Nonresponders were assumed to be treatment failures for data analysis. The primary outcome of satisfaction was similar in both groups (58% for MEA™ versus 53% for TBall, difference 5%; 95% CI -6 to 16%). Amenorrhoea rates were high following both techniques (51% versus 45%, difference 6%; 95% CI -5 to 17%). There was no significant difference in the hysterectomy rates between the two arms (9% versus 7%, difference 2%; 95% CI -5 to 9%). At 5 years post-treatment there were no significant clinical differences in patient satisfaction, menstrual status, quality of life scores or hysterectomy rates between MEA™ and Thermachoice 3, thermal balloon ablation. © 2014 Royal College of Obstetricians and Gynaecologists.

Simulation of ablation and plume dynamics under femtosecond double-pulse laser irradiation of aluminum: Comparison of atomistic and continual approaches

NASA Astrophysics Data System (ADS)

Fokin, Vladimir B.; Povarnitsyn, Mikhail E.; Levashov, Pavel R.

2017-02-01

We elaborated two numerical methods, two-temperature hydrodynamics and hybrid two-temperature molecular dynamics, which take into account basic mechanisms of a metal target response to ultrashort laser irradiation. The model used for the description of the electronic subsystem is identical for both approaches, while the ionic part is defined by an equation of state in hydrodynamics and by an interatomic potential in molecular dynamics. Since the phase diagram of the equation of state and corresponding potential match reasonably well, the dynamics of laser ablation obtained by both methods is quite similar. This correspondence can be considered as a first step towards the development of a self-consistent combined model. Two important processes are highlighted in simulations of double-pulse ablation: (1) the crater depth decrease as a result of recoil flux formation in the nascent plume when the delay between the pulses increases; (2) the plume reheating by the second pulse that gives rise to two- three-fold growth of the electron temperature with the delay varying from 0 to 200 ps.

Investigating the Mantle Source of the Lunar Crater Volcanic Field, Nevada: Evidence of a Thermal Plume?

NASA Astrophysics Data System (ADS)

Lee, J. W.; Roden, M.

2016-12-01

The Easy Chair Crater (ECC), located within the Lunar Crater Volcanic Field (LCVF) in central Nevada is particularly interesting because of the unusually high equilibrium temperatures and strain recorded by the mantle-derived xenoliths at LCVF1. In addition, a gravity and elevation anomaly suggests the possibility of an underlying thermal plume in the region2. In order to determine if the rocks at ECC are geochemically similar to rocks from other plume-related regions, we analyzed melt inclusions and olivine phenocrysts collected from basalts near the crater. Chlorine amounts in melt inclusions were normalized to the highly incompatible K to produce a ratio that is insensitive to crystallization within or along the walls of the inclusion3. Because Cl is implicated in lithosphere recycling, the Cl/K ratio can be used to differentiate magmatic source components. Initial results (Fig. 1) indicate that basalts from ECC are geochemically more similar to ocean island basalts than to MORB or arc basalts. Elemental ratios in olivine phenocrysts from basaltic magmas can be used to determine the petrology of the source rock for particular silicate melts. In turn, petrology of mantle sources is thought to correlate with source nature (e.g., plume versus upper mantle)4. Specifically, Ni and Mn amounts were evaluated in order to determine if magma sources were pyroxenite-rich. Preliminary calculations of the wt. fraction of pyroxenite in the source of ECC basalts ranged from 0.13 to 0.68 indicating the possibility of a significant amount of pyroxenite in the magmatic source which would be expected if a plume was present beneath LCVF. References:1Smith, D. (2000) JGR 105: 16769; 2Saltus, R.W. & Thompson, G.A. (1995) Tectonics 14:1235; 3Patiño Douce, A.E. & Roden, M.F. (2006) Geochim Cosmochim Acta 70: 3173; 4Gurenko et al. (2010) Contrib Mineral Petrol 159: 689

Doppler signals observed during high temperature thermal ablation are the result of boiling.

PubMed

Nahirnyak, Volodymyr M; Moros, Eduardo G; Novák, Petr; Suzanne Klimberg, V; Shafirstein, Gal

2010-01-01

To elucidate the causation mechanism of Spectral Doppler ultrasound signals (DUS) observed during high temperature thermal ablation and evaluate their potential for image-guidance. Sixteen ex vivo ablations were performed in fresh turkey breast muscle, eight with radiofrequency ablation (RFA) devices, and eight with a conductive interstitial thermal therapy (CITT) device. Temperature changes in the ablation zone were measured with thermocouples located at 1 to 10 mm away from the ablation probes. Concomitantly, DUS were recorded using a standard diagnostic ultrasound scanner. Retrospectively, sustained observations of DUS were correlated with measured temperatures. Sustained DUS was arbitrarily defined as the Doppler signals lasting more than 10 s as observed in the diagnostic ultrasound videos captured from the scanner. For RFA experiments, minimum average temperature (T1 +/- SD) at which sustained DUS were observed was 97.2 +/- 7.3 degrees C, while the maximum average temperature (T2 +/- SD) at which DUS were not seen was 74.3 +/- 9.1 degrees C. For CITT ablation, T1 and T2 were 95.7 +/- 5.9 degrees C and 91.6 +/- 7.2 degrees C, respectively. It was also observed, especially during CITT ablation, that temperatures remained relatively constant during Doppler activity. The value of T1 was near the standard boiling point of water (99.61 degrees C) while T2 was below it. Together, T1 and T2 support the conclusion that DUS during high temperature thermal ablation are the result of boiling (phase change). This conclusion is also supported by the nearly constant temperature histories maintained at locations from which DUS emanated.

A closer look at Galileo Thermal data from a Possible Plume Source North of Pwyll, Europa

NASA Astrophysics Data System (ADS)

Rathbun, J. A.; Spencer, J. R.

2017-12-01

Two different observing techniques, both employing the Hubble Space Telescope, have found evidence for plumes just off Europa's limb (Roth et al., 2014; Sparks et al., 2016). More recent observations using the Jovian transit technique enabled Sparks et al. (2017) to determine that one location was the source of two separate detections: just north of the impact crater Pwyll at 275 W, -16 S, a region we informally call North Pwyll. This source was detected on March 17, 2014 and February 22, 2016. Coinciding with this source is a broad thermal anomaly observed by the Galileo Photopolarimeter-Radiometer (PPR) during the Europan night (Sparks et al., 2017; Spencer et al., 1999). Rathbun et al. (2010) determined detection limits for the PPR observations and found that a 100 km2 hotspot in the vicinity of North Pwyll would have been detected if it had a temperature above about 150 K. We took a closer look at the PPR data and found that there are 5 PPR observations that include the North Pwyll region, at local times varying from midway between midnight and sunrise (the data already published) through midway between sunrise and noon. While at least one observation near noon is required for a complete measurement of the diurnal variation, we were able to fit a thermal model to the available data and found that endogenic heating is not required and that the data can be fit using an albedo of 0.4 and a thermal inertia of 114 in MKS units. Due to the sparseness and noisiness of the data, these values are very uncertain. Rathbun et al. (2010) found Europa's thermal inertias to be in the range of 20-140 MKS and albedos 0.3-0.7, so North Pwyll has a high thermal inertia and low albedo. Unfortunately, the high latitude of the other putative plume source locations (63 S and 75 S) puts them in areas poorly imaged by PPR.

Incidence and Risk Factors for Liver Abscess After Thermal Ablation of Liver Neoplasm

PubMed Central

Su, Xiu-Feng; Li, Na; Chen, Xu-Fang; Zhang, Lei; Yan, Ming

2016-01-01

Background Radiofrequency ablation (RFA) and microwave ablation (MWA) are the most frequently used thermal ablation methods for the treatment of liver cancer. Liver abscess is a common and severe complication of thermal ablation treatment. Objectives The objective of this study was to determine the incidence and risk factors of liver abscess formation after thermal ablation of liver cancer. Materials and Methods The clinical data of 423 patients who underwent 691 thermal ablation procedures for liver cancer were collected in order to retrospectively analyze the basic characteristics, incidence, and risk factors associated with liver abscess formation. Patients with multiple risk factors for liver abscess formation were enrolled in a risk factor group, and patients with no risk factors were enrolled in a control group. The chi-square test and multiple logistic regression analysis were used to analyze the relationship between the occurrence of liver abscesses and potential risk factors. Results Two hundred and eight patients underwent 385 RFA procedures, and 185 patients underwent 306 MWA procedures. The total incidence of liver abscesses was 1.7%, while the rates in the RFA group (1.8%) and MWA groups (1.6%) were similar (P > 0.05). The rates of liver abscesses in patients who had child-pugh class B and class C cirrhosis (P = 0.0486), biliary tract disease (P = 0.0305), diabetes mellitus (P = 0.0344), and porta hepatis tumors (P = 0.0123) were 4.0%, 6.7%, 6.5%, and 13.0%, respectively. There was a statistically significant difference between these four groups and the control group (all P < 0.05). The incidence of liver abscesses in the combined ablation and percutaneous ethanol injection (PEI) group (P = 0.0026) was significantly lower than that of the ablation group (P < 0.05). Conclusions The incidence of liver abscesses after liver cancer thermal ablation is low. Child-Pugh Class B and Class C cirrhosis, biliary tract disease, diabetes mellitus, and porta hepatis

Study of organic ablative thermal-protection coating for solid rocket motor

NASA Astrophysics Data System (ADS)

Hua, Zenggong

1992-06-01

A study is conducted to find a new interior thermal-protection material that possesses good thermal-protection performance and simple manufacturing possibilities. Quartz powder and Cr2O3 are investigated using epoxy resin as a binder and Al2O3 as the burning inhibitor. Results indicate that the developed thermal-protection coating is suitable as ablative insulation material for solid rocket motors.

Optical fiber biocompatible sensors for monitoring selective treatment of tumors via thermal ablation

NASA Astrophysics Data System (ADS)

Tosi, Daniele; Poeggel, Sven; Dinesh, Duraibabu B.; Macchi, Edoardo G.; Gallati, Mario; Braschi, Giovanni; Leen, Gabriel; Lewis, Elfed

2015-09-01

Thermal ablation (TA) is an interventional procedure for selective treatment of tumors, that results in low-invasive outpatient care. The lack of real-time control of TA is one of its main weaknesses. Miniature and biocompatible optical fiber sensors are applied to achieve a dense, multi-parameter monitoring, that can substantially improve the control of TA. Ex vivo measurements are reported performed on porcine liver tissue, to reproduce radiofrequency ablation of hepatocellular carcinoma. Our measurement campaign has a two-fold focus: (1) dual pressure-temperature measurement with a single probe; (2) distributed thermal measurement to estimate point-by-point cells mortality.

A Spectrum of Nerve Injury after Thermal Ablation: A Report of Four Cases and Review of the Literature

SciTech Connect

Philip, Asher; Gupta, Sanjay, E-mail: sgupta@mdanderson.org; Ahrar, Kamran, E-mail: kahrar@mdanderson.org

2013-10-15

Thermal ablation is an accepted alternative for the palliation of pain from bone metastases. Although rare, neurologic complications after thermal ablation have been reported. We present four cases, including two cases of rapid reversal of postcryoablation neurapraxia after the administration of steroid therapy, and review the literature.

Experimental application of thermosensitive paramagnetic liposomes for monitoring magnetic resonance imaging guided thermal ablation.

PubMed

Frich, Lars; Bjørnerud, Atle; Fossheim, Sigrid; Tillung, Terje; Gladhaug, Ivar

2004-12-01

The use of a liposomal paramagnetic agent with a T(1)-relaxivity that increases markedly at temperatures above the phase transition temperature (T(m)) of the liposomal membrane was evaluated during magnetic resonance imaging (MRI) guided hyperthermia ablation. A neodymium-yttrium aluminum garnet (Nd-YAG) laser unit and a radiofrequency ablation system were used for tissue ablation in eight rabbit livers in vivo. One ablation was made in each animal prior to administration of the liposomal agent. Liposomes with a T(m) of 57 degrees C containing gadodiamide (GdDTPA-BMA) were injected iv, and two additional ablations were performed. T(1)-weighted scans were performed in heated tissue, after tissue temperature had normalized, and 15-20 min after normalization of tissue temperature. Increase in signal intensity (DeltaSI) for ablations prior to injection of the agent was 13.0% (SD = 5.7) for the laser group and 9.1% (SD = 7.9) for the radiofrequency group. Signal intensity after administration of the agent unrelated to heating was not statistically significant (DeltaSI = 1.4%, P = 0.35). For ablations made after injection of the agent, a significant increase was found in the laser (DeltaSI = 34.5%, SD = 11.9) and radiofrequency group (DeltaSI = 21.6%, SD = 22.7). The persistent signal enhancement found in areas exposed to a temperature above the threshold temperature above T(m) allows thermal monitoring of MRI guided thermal ablation. (c) 2004 Wiley-Liss, Inc.

Phenolic Impregnated Carbon Ablators (PICA) as Thermal Protection Systems for Discovery Missions

NASA Technical Reports Server (NTRS)

Tran, Huy K.; Johnson, Christine E.; Rasky, Daniel J.; Hui, Frank C. L.; Hsu, Ming-Ta; Chen, Timothy; Chen, Y. K.; Paragas, Daniel; Kobayashi, Loreen

1997-01-01

This paper presents the development of the light weight Phenolic Impregnated Carbon Ablators (PICA) and its thermal performance in a simulated heating environment for planetary entry vehicles. The PICA material was developed as a member of the Light Weight Ceramic Ablators (LCA's), and the manufacturing process of this material has since been significantly improved. The density of PICA material ranges from 14 to 20 lbm/ft(exp 3), having uniform resin distribution with and without a densified top surface. The thermal performance of PICA was evaluated in the Ames arc-jet facility at cold wall heat fluxes from 375 to 2,960 BtU/ft(exp 2)-s and surface pressures of 0.1 to 0.43 atm. Heat loads used in these tests varied from 5,500 to 29,600 BtU/ft(exp 2) and are representative of the entry conditions of the proposed Discovery Class Missions. Surface and in-depth temperatures were measured using optical pyrometers and thermocouples. Surface recession was also measured by using a template and a height gage. The ablation characteristics and efficiency of PICA are quantified by using the effective heat of ablation, and the thermal penetration response is evaluated from the thermal soak data. In addition, a comparison of thermal performance of standard and surface densified PICA is also discussed.

An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

NASA Technical Reports Server (NTRS)

Dec, John A.; Braun, Robert D.

2005-01-01

A computer tool to perform entry vehicle ablative thermal protection systems sizing has been developed. Two options for calculating the thermal response are incorporated into the tool. One, an industry-standard, high-fidelity ablation and thermal response program was integrated into the tool, making use of simulated trajectory data to calculate its boundary conditions at the ablating surface. Second, an approximate method that uses heat of ablation data to estimate heat shield recession during entry has been coupled to a one-dimensional finite-difference calculation that calculates the in-depth thermal response. The in-depth solution accounts for material decomposition, but does not account for pyrolysis gas energy absorption through the material. Engineering correlations are used to estimate stagnation point convective and radiative heating as a function of time. The sizing tool calculates recovery enthalpy, wall enthalpy, surface pressure, and heat transfer coefficient. Verification of this tool is performed by comparison to past thermal protection system sizings for the Mars Pathfinder and Stardust entry systems and calculations are performed for an Apollo capsule entering the atmosphere at lunar and Mars return speeds.

An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

NASA Technical Reports Server (NTRS)

Dec, John A.; Braun, Robert D.

2006-01-01

A computer tool to perform entry vehicle ablative thermal protection systems sizing has been developed. Two options for calculating the thermal response are incorporated into the tool. One, an industry-standard, high-fidelity ablation and thermal response program was integrated into the tool, making use of simulated trajectory data to calculate its boundary conditions at the ablating surface. Second, an approximate method that uses heat of ablation data to estimate heat shield recession during entry has been coupled to a one-dimensional finite-difference calculation that calculates the in-depth thermal response. The in-depth solution accounts for material decomposition, but does not account for pyrolysis gas energy absorption through the material. Engineering correlations are used to estimate stagnation point convective and radiative heating as a function of time. The sizing tool calculates recovery enthalpy, wall enthalpy, surface pressure, and heat transfer coefficient. Verification of this tool is performed by comparison to past thermal protection system sizings for the Mars Pathfinder and Stardust entry systems and calculations are performed for an Apollo capsule entering the atmosphere at lunar and Mars return speeds.

Graphite Ablation and Thermal Response Simulation Under Arc-Jet Flow Conditions

NASA Technical Reports Server (NTRS)

Chen, Y.-K.; Milos, F. S.; Reda, D. C.; Stewart, D. A.; Venkatapathy, Ethiraj (Technical Monitor)

2002-01-01

The Two-dimensional Implicit Thermal Response and Ablation program, TITAN, was developed and integrated with a Navier-Stokes solver, GIANTS, for multidimensional ablation and shape change simulation of thermal protection systems in hypersonic flow environments. The governing equations in both codes are demoralized using the same finite-volume approximation with a general body-fitted coordinate system. Time-dependent solutions are achieved by an implicit time marching technique using Gauess-Siedel line relaxation with alternating sweeps. As the first part of a code validation study, this paper compares TITAN-GIANTS predictions with thermal response and recession data obtained from arc-jet tests recently conducted in the Interaction Heating Facility (IHF) at NASA Ames Research Center. The test models are graphite sphere-cones. Graphite was selected as a test material to minimize the uncertainties from material properties. Recession and thermal response data were obtained from two separate arc-jet test series. The first series was at a heat flux where graphite ablation is mainly due to sublimation, and the second series was at a relatively low heat flux where recession is the result of diffusion-controlled oxidation. Ablation and thermal response solutions for both sets of conditions, as calculated by TITAN-GIANTS, are presented and discussed in detail. Predicted shape change and temperature histories generally agree well with the data obtained from the arc-jet tests.

Monitoring of thermal dose during ablation therapy using quantum dot-mediated fluorescence thermometry.

PubMed

Bensalah, Karim; Tuncel, Altug; Hanson, Willard; Stern, Joshua; Han, Bumsoo; Cadeddu, Jeffrey

2010-12-01

The objective of this study was to demonstrate the feasibility of quantum dot (QD)-mediated fluorescence thermometry to monitor thermal dose in an in-vitro thermal ablation zone generated by laser-heated gold nanoshells (LGNS). Hyperthermic cell death of human prostate cancer cell line (PC-3) was determined after various heating settings and correlated to the thermal conditions using an Arrhenius model prior to LGNS ablation. PC-3 cells with gold nanoshells (GNS) and QDs were exposed to a near-infrared laser and QD excitation light. When the cells were heated by GNS, local temperature was measured using the temperature-dependent fluorescence intensity of QDs. Using the predetermined Arrhenius model, the thermal dose (i.e., cell death of PC-3 cells) by LGNS was estimated with local temperatures measured with QD-mediated thermometry. The estimated thermal dose was confirmed with calcein-acetoxy-methylester viability assay. For PC-3 cell line, the activation energy and frequency factor of the Arrhenius model were 86.78 kcal/mol and 6.35 × 10(55) Hz, respectively. During LGNS ablation of PC-3 cells, QD-mediated temperature measurement showed that the temperature of the laser spot increased rapidly to ∼58 °C ± 4 °C. The estimated thermal dose showed that cell death reached to ∼90% in 120 seconds. The death cell zone observed after staining corresponded to a peak area of the temperature profile generated after analysis of the QD fluorescence intensity. This study shows that the QD fluorescence thermometry can accurately monitor the PC-3 cell death by LGNS ablation. This approach holds promises for a better monitoring of thermal ablation procedures in clinical practice.

A Novel Combination of Thermal Ablation and Heat-Inducible Gene Therapy for Breast Cancer Treatment

DTIC Science & Technology

2008-04-01

focused ultrasound ( HIFU ) thermal ablation and HIFU -induced gene therapy represents a promising approach in improving the overall efficacy and quality...STATEMENT Approved for Public Release; Distribution Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT High intensity focused ultrasound ...al., High intensity focused ultrasound -induced gene activation in solid tumors. Journal of the Acoustical Society of America, 2006. 120(1): p. 492

A novel thermal accelerant for augmentation of microwave energy during image-guided tumor ablation

NASA Astrophysics Data System (ADS)

Park, William K. C.; Maxwell, Aaron W. P.; Frank, Victoria E.; Primmer, Michael P.; Paul, Jarod B.; Susai, Cynthia; Collins, Scott A.; Borjeson, Tiffany M.; Baird, Greyson L.; Lombardo, Kara A.; Dupuy, Damian E.

2017-02-01

The greatest challenge in image-guided thermal ablation (IGTA) of liver tumors is a relatively high recurrence rate (ca. 30%) due to incomplete ablation. To meet this challenge, we have developed a novel Thermal Accelerator (TA) to demonstrate its capability to, 1) augment microwave (MW) energy from a distance unattainable by antenna alone; 2) turn into a gel at body temperature; 3) act as a CT or US contrast. We have examined the TA efficiency using in vitro and ex vivo models: microwave power, TA dose, frequencies and TA-to-tip distance were varied, and temperature readings compared with and without TA. Using the in vitro model, it was established that both the rate and magnitude of increase in ablation zone temperature were significantly greater with TA under all tested conditions (p<0.0001). On ultrasound imaging, the TA was echogenic as gel. On CT, TA density was proportional to dose, with average values ranging from 329 HU to 3071 HU at 10 mg/mL and 1,000mg/mL, respectively. TA can be accurately deposited to a target area using CT or US as image-guidance and augment MW energy effectively so that ablation time is significantly reduced, which will contribute to complete ablation. The preliminary results obtained from in vivo experiments using swine as an animal model are consistent with the observations made in in vitro and en vivo studies.

CT-based investigation of the contraction of ex vivo tissue undergoing microwave thermal ablation

NASA Astrophysics Data System (ADS)

Lopresto, Vanni; Strigari, Lidia; Farina, Laura; Minosse, Silvia; Pinto, Rosanna; D'Alessio, Daniela; Cassano, Bartolomeo; Cavagnaro, Marta

2018-03-01

Treatment planning in microwave thermal ablation (MTA) requires the capability to predict and estimate the shape and dimension of the thermally coagulated zone obtainable following a clinical protocol. The ultimate result relies on the knowledge of the performance of the ablation device, as well as of the temperature-dependent structural modifications that the tissue undergoes during the treatment, because of the very high temperatures reached (up to 100 °C or higher). In this respect, tissue shrinkage plays an important role, since the dimension of the ablated tissue evaluated at the end of the MTA procedure (e.g. by way of CT imaging) could underestimate the actual treated tissue, leading to inaccurate assessment of the treatment outcome. In this study, CT imaging was used for real-time monitoring of tissue contraction during MTA experiments carried out in ex vivo bovine liver. Fiducial lead markers were positioned into the tissue in a 3D spatial grid around the MTA applicator. The spatial and temporal evolution of tissue contraction was imaged during the experiments, and analysed in terms of displacements of clusters of fiducial markers. The results obtained indicated that contraction is highly heterogeneous in the zone of ablation, depending both on the heating and on interactions with nearby tissue. In particular, tissue shrinkage appeared asymmetric with respect to the direction of insertion of the microwave applicator in the central area of carbonised tissue (about 30% and 19% along the radial and longitudinal directions, respectively), and isotropic in the region of coagulated (but not carbonised) tissue (about 11%). The total ablated volume was reduced by approximately 43% with respect to its pre-ablation value. Finally, temperature measurements displayed a correlation between temperature increment and temporal evolution of tissue contraction in the zone of ablation.

Winter movements of four fish species near a thermal plume in northern Minnesota

SciTech Connect

Ross, M.J.; Winter, J.D.

1981-01-01

Four fish species were studied during the winter of 1975 to compare their winter movements near the thermal plume of a power plant. Seventeen yellow perch (Perca flavescens), six northern pike (Esox lucius), three walleyes (Stizostedion vitreum), and two largemouth bass (Micropterus salmoides) were equipped with radio frequency transmitters. The spatial distributions differed among species. Only the largemouth bass confined their movements to heated water areas. The yellow perch, which was of particular interest, do not seem to be attracted to warm winter waters, and thus locate themselves in the peripheral areas of the discharge bay and fail to reproduce.more » This finding is contrary to those of previous studies.« less

High-intensity interstitial ultrasound for thermal ablation of focal cancer targets in prostate

NASA Astrophysics Data System (ADS)

Salgaonkar, Vasant A.; Scott, Serena; Kurhanewicz, John; Diederich, Chris J.

2017-03-01

Recent advances in image based techniques such as multi-parametric MRI (MP-MRI) can provide precise targeting of focal disease in the prostate. Thermal ablation of such cancer targets while avoiding rectum, urethra, neurovascular bundles (NVB) and sphincter is clinically challenging. The approach described here employs multi-element ultrasound linear arrays designed for transperineal placement within prostate. They consist of independently powered sectored tubular transducers (6.5 - 8.0 MHz) that provide spatial control of energy deposition in angle and length. Volumetric ablation strategies were investigated through patient-specific biothermal models based on Pennes bioheat transfer equation. The acoustic and heat transfer models used here have been validated in several previous simulation and experimental studies. Focal disease sites in prostate were identified through multi-parametric MR images of representative patient cases (n=3). Focal cancer lesions and critical anatomy (prostate, urethra, rectum, bladder, seminal vesicles) were manually segmented (Mimics, Materialise) and converted to 3D finite element meshes (3-Matic, Materialise). The chosen test cases consisted of patients with medium and large sized glands and models of bulk tissue ablation covered volumes in a single quadrant in posterior prostate, hemi-gland targets and "hockey-stick" targets (lesions in three quadrants). Ultrasound applicator placement was determined such that devices were positioned along the prostate periphery while avoiding surrounding anatomy. Transducer sector angles were chosen based on applicator location within limits of fabrication practicability. Thermal models were numerically solved using finite element methods (FEM) in COMSOL Multiphysics. Temperature and thermal dose distributions were calculated to determine treated volumes (> 240 CEM43C, >52 °C) and safety profiles (<10 CEM43C, <45 °C) for nerve, rectal and urethral sparing. Modeling studies indicated that focal

Conformal Ablative Thermal Protection Systems (CA-TPS) for Venus and Saturn Backshells

NASA Technical Reports Server (NTRS)

Beck, R.; Gasch, M.; Stackpoole, M.; Wilder, M.; Boghozian, T.; Chavez-Garcia, J.; Prabhu, Dinesh; Kazemba, Cole D.; Venkatapathy, E.

2016-01-01

This poster provides an overview of the work performed to date on the Conformal Ablative TPS (CA-TPS) element of the TPSM project out of GCDP. Under this element, NASA is developing improved ablative TPS materials based on flexible felt for reinforcement rather than rigid reinforcements. By replacing the reinforcements with felt, the resulting materials have much higher strain-to-failure and are much lower in thermal conductivity than their rigid counterparts. These characteristics should allow for larger tile sizes, direct bonding to aeroshells and even lower weight TPS. The conformal phenolic impregnated carbon felt (C-PICA) is a candidate for backshell TPS for both Venus and Saturn entry vehicles.

Ash-plume dynamics and eruption source parameters by infrasound and thermal imagery: The 2010 Eyjafjallajökull eruption

NASA Astrophysics Data System (ADS)

Ripepe, M.; Bonadonna, C.; Folch, A.; Delle Donne, D.; Lacanna, G.; Marchetti, E.; Höskuldsson, A.

2013-03-01

During operational ash-cloud forecasting, prediction of ash concentration and total erupted mass directly depends on the determination of mass eruption rate (MER), which is typically inferred from plume height. Uncertainties for plume heights are large, especially for bent-over plumes in which the ascent dynamics are strongly affected by the surrounding wind field. Here we show how uncertainties can be reduced if MER is derived directly from geophysical observations of source dynamics. The combination of infrasound measurements and thermal camera imagery allows for the infrasonic type of source to be constrained (a dipole in this case) and for the plume exit velocity to be calculated (54-142 m/s) based on the acoustic signal recorded during the 2010 Eyjafjallajökull eruption from 4 to 21 May. Exit velocities are converted into MER using additional information on vent diameter (50±10 m) and mixture density (5.4±1.1 kg/m3), resulting in an average ∼9×105 kg/s MER during the considered period of the eruption. We validate our acoustic-derived MER by using independent measurements of plume heights (Icelandic Meteorological Office radar observations). Acoustically derived MER are converted into plume heights using field-based relationships and a 1D radially averaged buoyant plume theory model using a reconstructed total grain size distribution. We conclude that the use of infrasonic monitoring may lead to important understanding of the plume dynamics and allows for real-time determination of eruption source parameters. This could improve substantially the forecasting of volcano-related hazards, with important implications for civil aviation safety.

Replacement of Ablators with Phase-Change Material for Thermal Protection of STS Elements

NASA Technical Reports Server (NTRS)

Kaul, Raj K.; Stuckey, Irvin; Munafo, Paul M. (Technical Monitor)

2002-01-01

As part of the research and development program to develop new Thermal Protection System (TPS) materials for aerospace applications at NASA's Marshall Space Flight Center (MSFC), an experimental study was conducted on a new concept for a non-ablative TPS material. Potential loss of TPS material and ablation by-products from the External Tank (ET) or Solid Rocket Booster (SRB) during Shuttle flight with the related Orbiter tile damage necessitates development of a non-ablative thermal protection system. The new Thermal Management Coating (TMC) consists of phase-change material encapsulated in micro spheres and a two-part resin system to adhere the coating to the structure material. The TMC uses a phase-change material to dissipate the heat produced during supersonic flight rather than an ablative material. This new material absorbs energy as it goes through a phase change during the heating portion of the flight profile and then the energy is slowly released as the phase-change material cools and returns to its solid state inside the micro spheres. The coating was subjected to different test conditions simulating design flight environments at the NASA/MSFC Improved Hot Gas Facility (IHGF) to study its performance.

Time-resolved investigations of the non-thermal ablation process of graphite induced by femtosecond laser pulses

SciTech Connect

Kalupka, C., E-mail: christian.kalupka@llt.rwth-aachen.de; Finger, J.; Reininghaus, M.

2016-04-21

We report on the in-situ analysis of the ablation dynamics of the, so-called, laser induced non-thermal ablation process of graphite. A highly oriented pyrolytic graphite is excited by femtosecond laser pulses with fluences below the classic thermal ablation threshold. The ablation dynamics are investigated by axial pump-probe reflection measurements, transversal pump-probe shadowgraphy, and time-resolved transversal emission photography. The combination of the applied analysis methods allows for a continuous and detailed time-resolved observation of the non-thermal ablation dynamics from several picoseconds up to 180 ns. Formation of large, μm-sized particles takes place within the first 3.5 ns after irradiation. The following propagation ofmore » ablation products and the shock wave front are tracked by transversal shadowgraphy up to 16 ns. The comparison of ablation dynamics of different fluences by emission photography reveals thermal ablation products even for non-thermal fluences.« less

Laser-induced thermal ablation of cancerous cell organelles.

PubMed

Letfullin, Renat R; Szatkowski, Scott A

2017-07-01

By exploiting the physical changes experienced by cancerous organelles, we investigate the feasibility of destroying cancerous cells by single and multipulse modes of laser heating. Our procedure consists of two primary steps: determining the normal and cancerous organelles optical properties and simulating the heating of all of the major organelles in the cell to find the treatment modes for the laser ablation of cancerous organelles without harming healthy cells. Our simulations show that the cancerous nucleus can be selectively heated to damaging temperatures, making this nucleus a feasible therapeutic particle and removing the need for nanoparticle injection. Because of the removal of this extra step, the procedure we propose is simpler and safer for the patient.

Thermal ablation therapeutics based on CNx multi-walled nanotubes

PubMed Central

Torti, Suzy V; Byrne, Fiona; Whelan, Orla; Levi, Nicole; Ucer, Burak; Schmid, Michael; Torti, Frank M; Akman, Steven; Liu, Jiwen; Ajayan, Pulickel M; Nalamasu, Omkaram; Carroll, David L

2007-01-01

We demonstrate that nitrogen doped, multi-walled carbon nanotubes (CNx-MWNT) result in photo-ablative destruction of kidney cancer cells when excited by near infrared (NIR) irradiation. Further, we show that effective heat transduction and cellular cytotoxicity depends on nanotube length: effective NIR coupling occurs at nanotube lengths that exceed half the wavelength of the stimulating radiation, as predicted in classical antenna theory. We also demonstrate that this radiation heats the nanotubes through induction processes, resulting in significant heat transfer to surrounding media and cell killing at extraordinarily small radiation doses. This cell death was attributed directly to photothermal effect generated within the culture, since neither the infrared irradiation itself nor the CNx-MWNT were toxic to the cells. PMID:18203437

Considerations for theoretical modeling of thermal ablation with catheter-based ultrasonic sources: implications for treatment planning, monitoring and control

PubMed Central

Prakash, Punit; Diederich, Chris J.

2012-01-01

Purpose To determine the impact of including dynamic changes in tissue physical properties during heating on feedback controlled thermal ablation with catheter-based ultrasound. Additionally, we compared impact several indicators of thermal damage on predicted extents of ablation zones for planning and monitoring ablations with this modality. Methods A 3D model of ultrasound ablation with interstitial and transurethral applicators incorporating temperature based feedback control was used to simulate thermal ablations in prostate and liver tissue. We investigated five coupled models of heat dependent changes in tissue acoustic attenuation/absorption and blood perfusion of varying degrees of complexity.. Dimensions of the ablation zone were computed using temperature, thermal dose, and Arrhenius thermal damage indicators of coagulative necrosis. A comparison of the predictions by each of these models was illustrated on a patient-specific anatomy in the treatment planning setting. Results Models including dynamic changes in blood perfusion and acoustic attenuation as a function of thermal dose/damage predicted near-identical ablation zone volumes (maximum variation < 2.5%). Accounting for dynamic acoustic attenuation appeared to play a critical role in estimating ablation zone size, as models using constant values for acoustic attenuation predicted ablation zone volumes up to 50% larger or 47% smaller in liver and prostate tissue, respectively. Thermal dose (t43 ≥ 240min) and thermal damage (Ω ≥ 4.6) thresholds for coagulative necrosis are in good agreement for all heating durations, temperature thresholds in the range of 54 °C for short (< 5 min) duration ablations and 50 °C for long (15 min) ablations may serve as surrogates for determination of the outer treatment boundary. Conclusions Accounting for dynamic changes in acoustic attenuation/absorption appeared to play a critical role in predicted extents of ablation zones. For typical 5—15 min ablations

An analysis of a charring ablator with thermal nonequilibrium, chemical kinetics, and mass transfer

NASA Technical Reports Server (NTRS)

Clark, R. K.

1973-01-01

The differential equations governing the transient response of a one-dimensional ablative thermal protection system are presented for thermal nonequilibrium between the pyrolysis gases and the char layer and with finite rate chemical reactions occurring. The system consists of three layers (the char layer, the uncharred layer, and an optical insulation layer) with concentrated heat sinks at the back surface and between the second and third layers. The equations are solved numerically by using a modified implicit finite difference scheme to obtain solutions for the thickness of the charred and uncharred layers, surface recession and pyrolysis rates, solid temperatures, porosity profiles, and profiles of pyrolysis-gas temperature, pressure, composition, and flow rate. Good agreement is obtained between numerical results and exact solutions for a number of simplified cases. The complete numerical analysis is used to obtain solutions for an ablative system subjected to a constant heating environment. Effects of thermal, chemical, and mass transfer processes are shown.

Ultrathin Injectable Sensors of Temperature, Thermal Conductivity, and Heat Capacity for Cardiac Ablation Monitoring

PubMed Central

Koh, Ahyeon; Gutbrod, Sarah R.; Meyers, Jason D.; Lu, Chaofeng; Webb, Richard Chad; Shin, Gunchul; Li, Yuhang; Kang, Seung-Kyun; Huang, Yonggang

2016-01-01

Knowledge of the distributions of temperature in cardiac tissue during and after ablation is important in advancing a basic understanding of this process, and for improving its efficacy in treating arrhythmias. Technologies that enable real-time temperature detection and thermal characterization in the transmural direction can help to predict the depths and sizes of lesion that form. Herein, materials and designs for an injectable device platform that supports precision sensors of temperature and thermal transport properties distributed along the length of an ultrathin and flexible needle-type polymer substrate are introduced. The resulting system can insert into the myocardial tissue, in a minimally invasive manner, to monitor both radiofrequency ablation and cryoablation, in a manner that has no measurable effects on the natural mechanical motions of the heart. The measurement results exhibit excellent agreement with thermal simulations, thereby providing improved insights into lesion transmurality. PMID:26648177

Ultrathin Injectable Sensors of Temperature, Thermal Conductivity, and Heat Capacity for Cardiac Ablation Monitoring.

PubMed

Koh, Ahyeon; Gutbrod, Sarah R; Meyers, Jason D; Lu, Chaofeng; Webb, Richard Chad; Shin, Gunchul; Li, Yuhang; Kang, Seung-Kyun; Huang, Yonggang; Efimov, Igor R; Rogers, John A

2016-02-04

Knowledge of the distributions of temperature in cardiac tissue during and after ablation is important in advancing a basic understanding of this process, and for improving its efficacy in treating arrhythmias. Technologies that enable real-time temperature detection and thermal characterization in the transmural direction can help to predict the depths and sizes of lesion that form. Herein, materials and designs for an injectable device platform that supports precision sensors of temperature and thermal transport properties distributed along the length of an ultrathin and flexible needle-type polymer substrate are introduced. The resulting system can insert into the myocardial tissue, in a minimally invasive manner, to monitor both radiofrequency ablation and cryoablation, in a manner that has no measurable effects on the natural mechanical motions of the heart. The measurement results exhibit excellent agreement with thermal simulations, thereby providing improved insights into lesion transmurality. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal Structure of Jupiter's Infrared Hotspots and Plumes in the Northern Equatorial Region

NASA Astrophysics Data System (ADS)

Fletcher, Leigh N.; Orton, Glenn S.; Rogers, John H.; Greathouse, Thomas K.; Momary, Thomas W.; Giles, Rohini Sara; Melin, Henrik; Sinclair, James; Irwin, Patrick Gerard Joseph; Vedovato, Marco

2016-10-01

The most prominent features of Jupiter's northern equatorial region are the visibly dark, 5-µm-bright 'hotspots' that move rapidly eastward on the southern edge of the North Equatorial Belt (NEB, Allison 1990, doi:10.1016/0019-1035(90)90069-L). We combine high-resolution thermal-infrared (5-20 µm) imaging from VLT/VISIR and IRTF/SpeX with spatially resolved spectroscopy from IRTF/TEXES to examine the thermal and chemical conditions in the equatorial region during the 2015-2016 apparition. The high spatial resolution permits the first detailed cross-comparison of thermal and visible-albedo conditions within the hotspots. We find that: (i) cloud-clearing within the hotspots creates 8.6-µm bright patches that are broader and more diffuse than their 5-µm counterparts; (ii) cloudy, cool cells ("plumes") in the northern Equatorial Zone are ammonia-rich and dark in the 5- and 8-12 µm range; (iii) the hotspots sometimes demonstrate a westward tilt with altitude in the 0.1-0.8 bar region (Fletcher et al., 2016, doi:10.1016/j.icarus.2016.06.008); and (iv) blue-grey streaks on the southeastern edges of these ammonia-rich cells are also cloud free and bright at 5-12 µm. This regular longitudinal pattern of cloudy cells and cloud-free hotspots is consistent with condensation of NH3-rich air as it ascends in cells, and subsidence of dry, volatile-depleted air in the hotspots. The westward tilt of the NEB hotspots with height that was detected in 2014 (but not in 2016) supports the equatorial Rossby-wave hypothesis for the NEB pattern. This equatorial wave is distinct from those in the upper troposphere during the 2015-16 NEB expansion event (Orton et al., DPS/EPSC 2016). The cells and hotspots observed in the thermal-IR are the same type as those detected at near-IR wavelengths by Galileo/NIMS (Baines et al. 2002, doi:10.1006/icar.2002.6901) and in the radio, probing the deep atmosphere (de Pater et al., 2016, doi:10.1126/science.aaf2210), suggesting a coherent structure

A probabilistic sizing tool and Monte Carlo analysis for entry vehicle ablative thermal protection systems

NASA Astrophysics Data System (ADS)

Mazzaracchio, Antonio; Marchetti, Mario

2010-03-01

Implicit ablation and thermal response software was developed to analyse and size charring ablative thermal protection systems for entry vehicles. A statistical monitor integrated into the tool, which uses the Monte Carlo technique, allows a simulation to run over stochastic series. This performs an uncertainty and sensitivity analysis, which estimates the probability of maintaining the temperature of the underlying material within specified requirements. This approach and the associated software are primarily helpful during the preliminary design phases of spacecraft thermal protection systems. They are proposed as an alternative to traditional approaches, such as the Root-Sum-Square method. The developed tool was verified by comparing the results with those from previous work on thermal protection system probabilistic sizing methodologies, which are based on an industry standard high-fidelity ablation and thermal response program. New case studies were analysed to establish thickness margins on sizing heat shields that are currently proposed for vehicles using rigid aeroshells for future aerocapture missions at Neptune, and identifying the major sources of uncertainty in the material response.

Laser heating and ablation at high repetition rate in thermal confinement regime

NASA Astrophysics Data System (ADS)

Brygo, François; Semerok, A.; Oltra, R.; Weulersse, J.-M.; Fomichev, S.

2006-09-01

Laser heating and ablation of materials with low absorption and thermal conductivity (paint and cement) were under experimental and theoretical investigations. The experiments were made with a high repetition rate Q-switched Nd:YAG laser (10 kHz, 90 ns pulse duration and λ = 532 nm). High repetition rate laser heating resulted in pulse per pulse heat accumulation. A theoretical model of laser heating was developed and demonstrated a good agreement between the experimental temperatures measured with the infrared pyrometer and the calculated ones. With the fixed wavelength and laser pulse duration, the ablation threshold fluence of paint was found to depend on the repetition rate and the number of applied pulses. With a high repetition rate, the threshold fluence decreased significantly when the number of applied pulses was increasing. The experimentally obtained thresholds were well described by the developed theoretical model. Some specific features of paint heating and ablation with high repetition rate lasers are discussed.

Percutaneous thermal ablation of lung tumors - Radiofrequency, microwave and cryotherapy: Where are we going?

PubMed

Palussière, J; Catena, V; Buy, X

2017-09-01

Main indications of percutaneous pulmonary thermal ablation are early stage non-small cell lung carcinoma (NSCLC) for patients who are not amenable to surgery and slow-evolving localized metastatic disease, either spontaneous or following a general treatment. Radiofrequency ablation (RFA) is the most evaluated technique. This technique offers a local control rate ranging between 80 and 90% for tumors <3cm in diameter. Other more recently used ablation techniques such as microwaves and cryotherapy could overcome some limitations of RFA. One common characteristic of these techniques is an excellent tolerance with very few complications. This article reviews the differences between these techniques when applied to lung tumors, indications, results and complications. Future potential associations with immunotherapy will be discussed. Copyright © 2017. Published by Elsevier Masson SAS.

Characterization of a 50kW Inductively Coupled Plasma Torch for Testing of Ablative Thermal Protection Materials

NASA Technical Reports Server (NTRS)

Greene, Benton R.; Clemens, Noel T.; Varghese, Philip L.; Bouslog, Stanley A.; Del Papa, Steven V.

2017-01-01

With the development of new manned spaceflight capabilities including NASA's Orion capsule and the Space-X Dragon capsule, there is a renewed importance of understanding the dynamics of ablative thermal protection systems. To this end, a new inductively coupled plasma torch facility is being developed at UT-Austin. The torch operates on argon and/or air at plasma powers up to 50 kW. In the present configuration the flow issues from a low-speed subsonic nozzle and the hot plume is characterized using slug calorimetry and emission spectroscopy. Preliminary measurements using emission spectroscopy have indicated that the torch is capable of producing an air plasma with a temperature between 6,000 K and 8,000 K depending on the power and flow settings and an argon plasma with a temperature of approximately 12,000 K. The operation envelope was measured, and heat flux measured for every point within the envelope using both a slug calorimeter and a Gardon gauge heat flux sensor. The torch was found to induce a stagnation point heat flux of between 90 and 225 W/sq cm.

The thermal and mechanical properties of a low-density glass-fiber-reinforced elastomeric ablation material

NASA Technical Reports Server (NTRS)

Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

1974-01-01

An evaluation of the thermal and mechanical properties was performed on a molded low-density elastomeric ablation material designated as Material B. Both the virgin and charred states were examined to provide meaningful inputs to the design of a thermal protection system. Chars representative of the flight chars formed during ablation were prepared in a laboratory furnace from 600 K to 1700 K and properties of effective thermal conductivity, heat capacity, porosity and permeability were determined on the furnace chars formed at various temperature levels within the range. This provided a boxing of the data which will enable the prediction of the transient response of the material during flight ablation.

Thermal response of a 4D carbon/carbon composite with volume ablation: a numerical simulation study

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-02-01

As carbon/carbon composites usually work at high temperature environments, material ablation inevitably occurs, which further affects the system stability and safety. In this paper, the thermal response of a thermoprotective four-directional carbon/carbon (4D C/C) composite is studied herein using a numerical model focusing on volume ablation. The model is based on energy- and mass-conservation principles as well as on the thermal decomposition equation of solid materials. The thermophysical properties of the C/C composite during the ablation process are calculated, and the thermal response during ablation, including temperature distribution, density, decomposition rate, char layer thickness, and mass loss, are quantitatively predicted. The present numerical study provides a fundamental understanding of the ablative mechanisms of a 4D C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Petrologic evidence that most ocean islands derive from thermally driven mantle plumes

NASA Astrophysics Data System (ADS)

Putirka, K. D.

2006-12-01

inter- island compositional variation is accounted for, all OIB except Galapagos yield excess temperatures (Tp^{OIB} - Tp^{MORB}) of 133-280°C, with a mean of 186± 36°C. Galapagos lavas yield an excess temperature of 16°C; perhaps mixing has diluted its thermal signal, but in any event, its Tp is essentially identical to MORB. Nevertheless, most OIB (93% in this sample) exhibit large excess temperatures. Thermally driven mantle plumes, as proposed by Morgan (1971), thus appear to be common, not rare. A second implication, less certain than the first, involves the narrow standard deviation of ±36°C for Tp at OIB, which almost certainly reflects a lower limit to actual thermal variability. This narrow range indicates that all hot spots derive from a single thermal boundary layer.

Development of a fine thermocouple-needle system for real-time feedback of thermal tumour ablation margin

PubMed Central

Ishizaka, H; Shiraishi, A; Awata, S; Shimizu, A; Hirasawa, S

2011-01-01

Thermal tumour ablation techniques such as radiofrequency (RF) ablation are applied for radical removal of local tumours as an easier, less invasive alternative to surgical resection. A serious drawback of thermal ablation, however, is that the ablation area cannot be accurately assessed during the procedure. To achieve real-time feedback and exact and safe ablation, a superfine thermocouple-needle system (TNS) comprising a 0.25-mm diameter thermocouple embedded in a 22-G, 15-cm-long needle was devised and efficacy was tested in vitro using porcine livers (n = 15) and in vivo using rabbit back muscles (n = 2) and livers (n = 3). A 17-gauge RF electrode with a 2 cm active tip was used for ablation. The TNS was inserted 1 cm from the active tip of the RF electrode and liver temperature around the electrode was measured concurrently. The RF current was cut off when the temperature reached 60°C or after 5 min at ≥50°C. Porcine livers and rabbit back muscles were then cut along a plane passing through the axes of the electrode and the TNS. In rabbit livers, contrast-enhanced CT was performed to evaluate ablation areas. Ablation areas in cut surfaces of porcine livers exhibited well-defined discoloured regions and the TNS tip precisely pinpointed the margin of the ablation area. Contrast-enhanced CT of rabbit livers showed the TNS tip accurately located at the margin of areas without contrast enhancement. These results indicate that the TNS can accurately show ablation margins and that placing the TNS tip at the intended ablation margin permits exact thermal ablation. PMID:21937618

Short communication. Development of a fine thermocouple-needle system for real-time feedback of thermal tumour ablation margin.

PubMed

Ishizaka, H; Shiraishi, A; Awata, S; Shimizu, A; Hirasawa, S

2011-12-01

Thermal tumour ablation techniques such as radiofrequency (RF) ablation are applied for radical removal of local tumours as an easier, less invasive alternative to surgical resection. A serious drawback of thermal ablation, however, is that the ablation area cannot be accurately assessed during the procedure. To achieve real-time feedback and exact and safe ablation, a superfine thermocouple-needle system (TNS) comprising a 0.25-mm diameter thermocouple embedded in a 22-G, 15-cm-long needle was devised and efficacy was tested in vitro using porcine livers (n = 15) and in vivo using rabbit back muscles (n = 2) and livers (n = 3). A 17-gauge RF electrode with a 2 cm active tip was used for ablation. The TNS was inserted 1 cm from the active tip of the RF electrode and liver temperature around the electrode was measured concurrently. The RF current was cut off when the temperature reached 60°C or after 5 min at ≥50°C. Porcine livers and rabbit back muscles were then cut along a plane passing through the axes of the electrode and the TNS. In rabbit livers, contrast-enhanced CT was performed to evaluate ablation areas. Ablation areas in cut surfaces of porcine livers exhibited well-defined discoloured regions and the TNS tip precisely pinpointed the margin of the ablation area. Contrast-enhanced CT of rabbit livers showed the TNS tip accurately located at the margin of areas without contrast enhancement. These results indicate that the TNS can accurately show ablation margins and that placing the TNS tip at the intended ablation margin permits exact thermal ablation.

An in-vitro animal experiment on metal implants’ thermal effect on radiofrequency ablation

PubMed Central

2013-01-01

Background To explore metal implants’ thermal effect on radiofrequency ablation (RFA) and ascertain distance-thermal relationship between the metal implants and radiofrequency (RF) electrode. Methods Metal implants models were established in seven in-vitro porcine livers using silver clips or 125I seeds. RFA were conducted centering the RF electrode axis1 cm away from them, with one side containing a metal implants model the test group and the other side the control group. The thermometric needles were used to measure multi-point temperatures in order to compare the time-distance-temperature difference between the two groups. The gross scopes of the ablation of the two groups were measured and the tissues were analyzed for microscopic histology. Results At the ablation times of 8, 12, and 15 min, the average multi-point temperatures of the test group and the control group were 48.2±18.07°C, 51.5±19.57°C, 54.6±19.75°C, and 48.6±17.69°C, 52.2±19.73°C, 54.9±19.24°C, respectively, and the differences were not statistically significant (n=126, P>0.05). At the ablation times of 12 and 15 min, the ablation scopes of the test group and the control group were (horizontal/longitudinal diameter) 1.55/3.48 cm, 1.89/3.72 cm, and 1.56/3.48 cm, 1.89/3.72 cm, respectively, and the differences were not statistically significant (n=14, P>0.05). The two groups had the same manifestations in microscopy. Conclusions Metal implants do not cause significant thermal effect on RFA. PMID:23799942

Mathematical study of the effects of different intrahepatic cooling on thermal ablation zones.

PubMed

Peng, Tingying; O'Neill, David; Payne, Stephen

2011-01-01

Thermal ablation of a tumour in the liver with Radio Frequency energy can be accomplished by using a probe inserted into the tissue under the guidance of medical imaging. The extent of ablation can be significantly affected by heat loss due to the high blood perfusion in the liver, especially when the tumour is located close to large vessels. A mathematical model is thus presented here to investigate the heat sinking effects of large vessels, combining a 3D two-equation coupled bio-heat model and a 1D model of convective heat transport across the blood vessel surface. The model simulation is able to recover the experimentally observed different intrahepatic cooling on thermal ablation zones: hepatic veins showed a focal indentation whereas portal veins showed broad flattening of the ablation zones. Moreover, this study also illustrates that this shape derivation can largely be attributed to the temperature variations between the microvascular branches of portal vein as compared with hepatic vein. In contrast, different amount of surface heat convection on the vessel wall between these two types of veins, however, has a minor effect.

Study on mechanical and ablative properties of EPDM/OMMT thermal insulating nanocomposites.

PubMed

Gao, Guoxin; Zhang, Zhicheng; Li, Xuefei; Meng, Qingjie; Zheng, Yuansuo; Jin, Zhihao

2010-11-01

In order to enhance the elongation at break, the ablation resistant properties as well as the tensile strength of the thermal insulating materials, organo-montmorillonite (OMMT) was introduced into the short aramid fibers reinforced Ethylene-Propylene-Diene Monomer (EPDM) based nanocomposites. The effects of OMMT content on the mechanical and ablative properties of the nanocomposites were investigated systematically. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirm that EPDM-matrix has been intercalated into OMMT interlayers after a mixing process on a two-roll mill. The brittle fracture of nanocomposites also indicates that OMMT can lubricate aramid fiber to weaken the interfacial adhesive strength between the fibers and the matrix. As a result, the tensile strength and elongation at break are both improved sharply with OMMT content increasing from 1 phr to 7 phr. However, thanks to the inevitable agglomeration of OMMT with high loading inside the nanocomposites, the tensile strength and elongation at break reduce gently once OMMT is over 7 phr. Furthermore, the ablation resistant properties are improved greatly by increasing OMMT from 1 phr to 11 phr. Therefore, the optimal content of OMMT is 7-11 phr for the thermal insulating nanocomposites with big elongation and excellent ablation resistant properties.

Radiofrequency thermal ablation in canine femur: evaluation of coagulation necrosis reproducibility and MRI-histopathologic correlation.

PubMed

Lee, Jeong Min; Choi, Seong Hong; Park, Hee Seon; Lee, Min Woo; Han, Chang Jin; Choi, Joon-il; Choi, Ja-Young; Hong, Sung Hwan; Han, Joon Koo; Choi, Byung Ihn

2005-09-01

Our purposes were to determine whether a single application of radiofrequency energy to normal bone can create coagulation necrosis reproducibly and to assess the accuracy of MRI at revealing the extent of radiofrequency-induced thermal bone injury. Using a 200-W generator and a 17-gauge cooled-tip electrode, a total of 11 radiofrequency ablations were performed under fluoroscopic guidance in the distal femurs of seven dogs. Radiofrequency was applied in standard monopolar mode at 100 W for 10 min. During radiofrequency ablation, the changes in impedance and currents were recorded. MRI, including unenhanced T1- and T2-weighted images and contrast-enhanced fat-suppressed T1-weighted images, was performed to evaluate ablation regions. Six dogs were killed on day 4 after MRI and one dog on day 7. In all animals, radiofrequency ablation created a well-defined coagulation necrosis and no significant complications were noted. The mean long-axis diameter and the mean short-axis diameter of the coagulation zones produced were 45.9 +/- 5.5 mm and 17.7 +/- 2.7 mm, respectively. At gross examination, thermal ablation regions appeared as a central, light-brown area with a dark-brown peripheral hemorrhagic zone, which was surrounded by a pale-yellow rim. On MRI, the ablated areas showed multilayered zones with signal intensities that differed from normal marrow on unenhanced images and a perfusion defect on contrast-enhanced T1-weighted images. The maximum difference between lesion sizes on MR images, established by measuring macroscopic coagulation necrosis, was 3 mm. The correlation between the diameter of coagulation necrosis and lesion size at MRI was strong, with correlation coefficients ranging from 0.89 for unenhanced T1-weighted images and 0.97 for unenhanced T2-weighted images to 0.98 for contrast-enhanced T1-weighted images (p < 0.05). Radiofrequency ablation created well-defined coagulation necrosis in a reproducible manner, and MRI accurately determined the extent

Volcanic plume and bomb field masses from thermal infrared camera imagery

NASA Astrophysics Data System (ADS)

Harris, A. J. L.; Delle Donne, D.; Dehn, J.; Ripepe, M.; Worden, A. K.

2013-03-01

Masses erupted during normal explosions at Stromboli volcano (Italy) are notoriously difficult to measure. We present a method that uses thermal infrared video for cooling bomb fields to obtain the total power emitted by all hot particles emitted during an explosion. A given mass of magma (M) will emit a finite amount of thermal power, defined by M cp(Te-T0), cp and Te being magma specific heat capacity and temperature, and T0 being ambient temperature. We use this relation to convert the total power emitted by the bomb field to the mass required to generate that power. To do this we extract power flux curves for the field and integrate this through time to obtain total power (E). This is used to estimate mass (Q) in Q=E/cp(Te-T0). When applied to individual bombs we obtain masses of between 1 and 9 kg per bomb, or a volume of 970 and 6500 cm3. These volumes equate to spheres with diameters 12 and 27 cm. For the entire bomb field we obtain volumes of 7-28 m3. We calculate masses for 32 eruptions and obtain typical bomb masses of between 103 and 104 kg per eruption. In addition, we estimate that between 102 and 103 kg of gas and ash are emitted as part of a mixed plume of bombs, gas and ash. We identify two types of eruption on the basis of the erupted bomb masses and the ratio of the plume's gas-and-ash component to the bomb component. The first type is bomb-dominated, is characterized by bomb masses of 104 kg and has ash-gas/ bomb ratios of ˜0.02. The second type is ash-and-gas dominated, is characterized by erupted bomb masses of 103 kg and has ash-gas/bomb ratios of around one, and as high as two. There is no correlation between the quantity of bombs and quantity of gas-ash erupted. In addition, while source pressure for each explosion correlates with the quantity of gas and ash erupted, the mass of bombs emitted varies independently of pressure.

Gold Nanoparticles as a Photothermal Agent in Cancer Therapy: The Thermal Ablation Characteristic Length.

PubMed

Grosges, Thomas; Barchiesi, Dominique

2018-05-31

In cancer therapy, the thermal ablation of diseased cells by embedded nanoparticles is one of the known therapies. It is based on the absorption of the energy of the illuminating laser by nanoparticles. The resulting heating of nanoparticles kills the cell where these photothermal agents are embedded. One of the main constraints of this therapy is preserving the surrounding healthy cells. Therefore, two parameters are of interest. The first one is the thermal ablation characteristic length, which corresponds to an action distance around the nanoparticles for which the temperature exceeds the ablation threshold. This critical geometric parameter is related to the expected conservation of the body temperature in the surroundings of the diseased cell. The second parameter is the temperature that should be reached to achieve active thermal agents. The temperature depends on the power of the illuminating laser, on the size of nanoparticles and on their physical properties. The purpose of this paper is to propose behavior laws under the constraints of both the body temperature at the boundary of the cell to preserve surrounding cells and an acceptable range of temperature in the target cell. The behavior laws are deduced from the finite element method, which is able to model aggregates of nanoparticles. We deduce sensitivities to the laser power and to the particle size. We show that the tuning of the temperature elevation and of the distance of action of a single nanoparticle is not significantly affected by variations of the particle size and of the laser power. Aggregates of nanoparticles are much more efficient, but represent a potential risk to the surrounding cells. Fortunately, by tuning the laser power, the thermal ablation characteristic length can be controlled.

A Novel Combination of Thermal Ablation and Heat-Inducible Gene therapy for Breast Cancer Treatment

DTIC Science & Technology

2009-04-01

intensity focused ultrasound ( HIFU ) has been developed as an emerging non-invasive strategy for cancer treatment by thermal ablation of tumor tissue. The...Leenders, G., et al., Histopathological changes associated with high intensity focused ultrasound ( HIFU ) treatment for localised adenocarcinoma of...invasive strategy for cancer therapy [1, 2]. Through HIFU exposure, acoustic energy is focused into a deep-sited tumor volume and converted into heat

Thermal and mechanical high-intensity focused ultrasound: perspectives on tumor ablation, immune effects and combination strategies.

PubMed

van den Bijgaart, Renske J E; Eikelenboom, Dylan C; Hoogenboom, Martijn; Fütterer, Jurgen J; den Brok, Martijn H; Adema, Gosse J

2017-02-01

Tumor ablation technologies, such as radiofrequency-, cryo- or high-intensity focused ultrasound (HIFU) ablation will destroy tumor tissue in a minimally invasive manner. Ablation generates large volumes of tumor debris in situ, releasing multiple bio-molecules like tumor antigens and damage-associated molecular patterns. To initiate an adaptive antitumor immune response, antigen-presenting cells need to take up tumor antigens and, following activation, present them to immune effector cells. The impact of the type of tumor ablation on the precise nature, availability and suitability of the tumor debris for immune response induction, however, is poorly understood. In this review, we focus on immune effects after HIFU-mediated ablation and compare these to findings using other ablation technologies. HIFU can be used both for thermal and mechanical destruction of tissue, inducing coagulative necrosis or subcellular fragmentation, respectively. Preclinical and clinical results of HIFU tumor ablation show increased infiltration and activation of CD4 + and CD8 + T cells. As previously observed for other types of tumor ablation technologies, however, this ablation-induced enhanced infiltration alone appears insufficient to generate consistent protective antitumor immunity. Therapies combining ablation with immune stimulation are therefore expected to be key to boost HIFU-induced immune effects and to achieve systemic, long-lasting, antitumor immunity.

Yield of Routine Image-Guided Biopsy of Renal Mass Thermal Ablation Zones: 11-Year Experience.

PubMed

Wasnik, Ashish P; Higgins, Ellen J; Fox, Giovanna A; Caoili, Elaine M; Davenport, Matthew S

2018-06-19

To determine the yield of routine image-guided core biopsy of renal cell carcinoma (RCC) thermal ablation zones. Institutional review board approval was obtained for this Health Insurance Portability and Accountability Act-compliant quality improvement effort. Routine core biopsy of RCC ablation zones was performed 2 months postablation from July 2003 to December 2014. Routine nicotinamide adenine dinucleotide staining was performed by specialized genitourinary pathologists to assess cell viability. The original purpose of performing routine postablation biopsy was to verify, in addition to imaging, whether the mass was completely treated. Imaging was stratified as negative, indeterminate, or positive for viable malignancy. Histology was stratified as negative, indeterminate, positive, or nondiagnostic for viable malignancy. Histology results were compared to prebiopsy imaging findings. Routine ablation zone biopsy was performed after 50% (146/292) of index ablations (24 cryoablations, 122 radiofrequency ablations), and postablation imaging was performed more often with multiphasic computed tomography than magnetic resonance imaging (100 vs 46, p < 0.0001). When imaging was negative (n = 117), biopsy added no additional information (92% [n = 108] negative, 0.9% [n = 1] indeterminate, 7% [n = 8] nondiagnostic). When imaging was indeterminate (n = 19), 11% (n = 2) of biopsies had viable RCC and 89% (n = 17) were negative. When imaging was positive, biopsy detected viable neoplasm in only 10% (1/10) of cases; 80% (8/10) were negative and 10% (1/10) were nondiagnostic. Routine biopsy of renal ablation zones to validate postablation imaging results was not value-added and therefore was discontinued at the study institution. Copyright © 2018. Published by Elsevier Inc.

Thermal and non-thermal explosion in metals ablation by femtosecond laser pulse: classical approach of the Two Temperature Model

NASA Astrophysics Data System (ADS)

Abdelmalek, Ahmed; Bedrane, Zeyneb; Amara, El-Hachemi

2018-03-01

We propose a classical Two Temperature Model TTMc where we consider the metal film during the irradiation like an ideal plasma. The numerical results are comparing to those finding by the existing TTM and the experimental data. In our model The cooper is taken as a target irradiated by a single laser pulse with 120 fs at 800 nm wavelength in air room. Our numerical results shown that there are a thermal and non-thermal explosion successively occurs in metal ablation by ultrashort laser pulse.

Evaluation of a Novel Thermal Accelerant for Augmentation of Microwave Energy during Image-guided Tumor Ablation.

PubMed

Park, William Keun Chan; Maxwell, Aaron Wilhelm Palmer; Frank, Victoria Elizabeth; Primmer, Michael Patrick; Collins, Scott Andrew; Baird, Grayson Luderman; Dupuy, Damian Edward

2017-01-01

The primary challenge in thermal ablation of liver tumors (e.g. hepatocellular carcinoma and hepatic colorectal cancer) is the relatively high recurrence rate (~30%) for which incomplete ablation at the periphery of the tumor is the most common reason. In an attempt to overcome this, we have developed a novel thermal accelerant (TA) agent capable of augmenting microwave energy from a distance normally unattainable by a single microwave ablation antenna. This cesium-based block co-polymer compound transforms from a liquid to a gel at body temperature and is intrinsically visible by computed tomography. Using an agarose phantom model, herein we demonstrate that both the rate and magnitude of temperature increase during microwave ablation were significantly greater in the presence of TA when compared with controls. These results suggest robust augmentation of microwave energy, and may translate into larger ablation zone volumes within biologic tissues. Further work using in vivo techniques is necessary to confirm these findings.

Ultrasound-directed robotic system for thermal ablation of liver tumors: a preliminary report

NASA Astrophysics Data System (ADS)

Zheng, Jian; Tian, Jie; Dai, Yakang; Zhang, Xing; Dong, Di; Xu, Min

2010-03-01

Thermal ablation has been proved safe and effective as the treatment for liver tumors that are not suitable for resection. Currently, manually performed thermal ablation is greatly dependent on the surgeon's acupuncture manipulation against hand tremor. Besides that, inaccurate or inappropriate placement of the applicator will also directly decrease the final treatment effect. In order to reduce the influence of hand tremor, and provide an accurate and appropriate guidance for a better treatment, we develop an ultrasound-directed robotic system for thermal ablation of liver tumors. In this paper, we will give a brief preliminary report of our system. Especially, three innovative techniques are proposed to solve the critical problems in our system: accurate ultrasound calibration when met with artifacts, realtime reconstruction with visualization using Graphic Processing Unit (GPU) acceleration and 2D-3D ultrasound image registration. To reduce the error of point extraction with artifacts, we propose a novel point extraction method by minimizing an error function which is defined based on the geometric property of our N-fiducial phantom. Then realtime reconstruction with visualization using GPU acceleration is provided for fast 3D ultrasound volume acquisition with dynamic display of reconstruction progress. After that, coarse 2D-3D ultrasound image registration is performed based on landmark points correspondences, followed by accurate 2D-3D ultrasound image registration based on Euclidean distance transform (EDT). The effectiveness of our proposed techniques is demonstrated in phantom experiments.

Ultrasound elastographic imaging of thermal lesions and temperature profiles during radiofrequency ablation

NASA Astrophysics Data System (ADS)

Techavipoo, Udomchai

Manual palpation to sense variations in tissue stiffness for disease diagnosis has been regularly performed by clinicians for centuries. However, it is generally limited to large and superficial structures and the ability of the physician performing the palpation. Imaging of tissue stiffness or elastic properties via the aid of modern imaging such as ultrasound and magnetic resonance imaging, referred to as elastography, enhances the capability for disease diagnosis. In addition, elastography could be used for monitoring tissue response to minimally invasive ablative therapies, which are performed percutaneously to destruct tumors with minimum damage to surrounding tissue. Monitoring tissue temperature during ablation is another approach to estimate tissue damage. The ultimate goal of this dissertation is to improve the image quality of elastograms and temperature profiles for visualizing thermal lesions during and after ablative therapies. Elastographic imaging of thermal lesions is evaluated by comparison of sizes, shapes, and volumes with the results obtained using gross pathology. Semiautomated segmentation of lesion boundaries on elastograms is also developed. It provides comparable results to those with manual segmentation. Elastograms imaged during radiofrequency ablation in vitro show that the impact of gas bubbles during ablation on the ability to delineate the thermal lesion is small. Two novel methods to reduce noise artifacts in elastograms, and an accurate estimation of displacement vectors are proposed. The first method applies wavelet-denoising algorithms to the displacement estimates. The second method utilizes angular compounding of the elastograms generated using ultrasound signal frames acquired from different insonification angles. These angular frames are also utilized to estimate all tissue displacement vector components in response to a deformation. These enable the generation of normal and shear strain elastograms and Poisson's ratio

Recurrence and Survival Outcomes After Percutaneous Thermal Ablation of Oligometastatic Melanoma.

PubMed

White, Mariah L; Atwell, Thomas D; Kurup, A Nicholas; Schmit, Grant D; Carter, Rickey E; Geske, Jennifer R; Kottschade, Lisa A; Pulido, Jose S; Block, Matthew S; Jakub, James W; Callstrom, Matthew R; Markovic, Svetomir N

2016-03-01

To evaluate focal treatment of melanoma metastases and to explore whether any potential extended survival benefit exists in a select patient population. All patients who underwent image-guided local thermal ablation of metastatic melanoma over an 11-year period (January 1, 2002, to December 31, 2013) were retrospectively identified using an internally maintained clinical registry. Only patients with oligometastatic stage IV disease amenable to complete ablation of all clinical disease at the time of ablation were included in the analysis. Overall survival and median progression-free survival periods were calculated. Thirty-three patients with primary ocular or nonocular melanoma had 66 metastases treated in the lungs, liver, bones, or soft tissues. Eleven (33%) patients were on systemic medical therapy at the time of the procedure. The median survival time was 3.8 years (range, 0.5-10.5 years), with a 4-year estimated survival of 44.1% (95% CI, 28%-68%). Local recurrence at the ablation site developed in 15.1% (5 of 33) of the patients and 13.6% of the tumors (9 of 66). The median progression-free survival time was 4.4 months (95% CI, 1.4 months to 10.5 years), with an estimated 1-year progression-free survival of 30.3% (95% CI, 18%-51%). A subgroup analysis identified 11 patients with primary ocular melanoma and 22 with nonocular melanoma, with a median survival time of 3.9 years (range, 0.9-4.7 years) and 3.8 years (range, 0.5-10.5 years), respectively (P=.58). There were no major complications and no deaths within 30 days of the procedure. Selective use of image-guided thermal ablation of oligometastatic melanoma may provide results similar to surgical resection in terms of technical effectiveness and oncologic outcomes with minimal risk. Copyright © 2016 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.

Ambient infrared laser ablation mass spectrometry (AIRLAB-MS) with plume capture by continuous flow solvent probe

DOEpatents

O'Brien, Jeremy T.; Williams, Evan R.; Holman, Hoi-Ying N.

2017-10-31

A new experimental setup for spatially resolved ambient infrared laser ablation mass spectrometry (AIRLAB-MS) that uses an infrared microscope with an infinity-corrected reflective objective and a continuous flow solvent probe coupled to a Fourier transform ion cyclotron resonance mass spectrometer is described. The efficiency of material transfer from the sample to the electrospray ionization emitter was determined using glycerol/methanol droplets containing 1 mM nicotine and is .about.50%. This transfer efficiency is significantly higher than values reported for similar techniques.

Thermal ablation of intrahepatic cholangiocarcinoma: Safety, efficacy, and factors affecting local tumor progression.

PubMed

Takahashi, Edwin A; Kinsman, Kristin A; Schmit, Grant D; Atwell, Thomas D; Schmitz, John J; Welch, Brian T; Callstrom, Matthew R; Geske, Jennifer R; Kurup, A Nicholas

2018-06-04

To evaluate the safety and oncologic efficacy of percutaneous thermal ablation of intrahepatic cholangiocarcinoma (ICC) and identify risk factors for local tumor progression (LTP). Retrospective review of an institutional tumor ablation registry demonstrated that 20 patients (9 males, 11 females; mean age 62.5 ± 15.8 years) with 50 ICCs (mean size 1.8 ± 1.3 cm) were treated with percutaneous radiofrequency ablation (RFA) or microwave ablation (MWA) between 2006 and 2015. Thirty-eight of the treated ICCs (76%) were metastases that developed after surgical resection of the primary tumor. Patient demographics, procedure technical parameters, and clinical outcomes were reviewed. A Cox proportional hazards model was used to examine the risk of LTP by ablation modality. Survival analyses were performed using the Kaplan-Meier method. Mean imaging follow-up time was 41.5 ± 42.7 months. Forty-four (88%) ICCs were treated with RFA, and 6 (12%) with MWA. Eleven (22%) cases of LTP developed in 5 (25%) patients. The median time to LTP among these 11 tumors was 7.1 months (range, 2.3-22.9 months). Risk of LTP was not significantly different for ICCs treated with MWA compared to RFA (HR 2.72; 95% CI 0.58-12.84; p = 03.21). Median disease-free survival was 8.2 months (1.1-70.4 months), and median overall survival was 23.6 months (7.4-122.5 months). No major complication occurred. Percutaneous thermal ablation is a safe and effective treatment for patients with ICCs and may be particularly valuable in unresectable patients, or those who have already undergone hepatic surgery. Tumor size and ablation modality were not associated with LTP, whereas primary tumors and superficially located tumors were more likely to subsequently recur.

Development and evaluation of an ablative closeout material for solid rocket booster thermal protection system

NASA Technical Reports Server (NTRS)

Patterson, W. J.

1979-01-01

A trowellable closeout/repair material designated as MTA-2 was developed and evaluated for use on the Solid Rocket Booster. This material is composed of an epoxy-polysulfide binder and is highly filled with phenolic microballoons for density control and ablative performance. Mechanical property testing and thermal testing were performed in a wind tunnel to simulate the combined Solid Rocket Booster trajectory aeroshear and heating environments. The material is characterized by excellent thermal performance and was used extensively on the Space Shuttle STS-1 and STS-2 flight hardware.

Winter movements of four fish species near a thermal plume in northern Minnesota

SciTech Connect

Ross, M.J.; Winter, J.D.

1981-01-01

During winter 1975, 17 yellow perch (Perca flavescens), 6 northern pike (Esox lucius), 3 walleyes (Stizostedion vitreum), and 2 largemouth bass (Micropterus salmoides) were equipped with radio frequency transmitters to compare their winter movements near the thermal plume of a power plant. The mean home range sizes, in hectares, were northern pike 19.0; yellow perch 13.4; largemouth bass 3.7; walleye 2.2. Northern pike and yellow perch had mean home range sizes larger than the discharge area. Mean water depths at fish locations were as follows: largemouth bass 0.8 m; northern pike 1.2 m; yellow perch 1.6 m; walleye 3.5 m.more » Largemouth bass preferred the warmest locations near the discharge point. Yellow perch were most often located in the peripheral areas of the discharge bay while walleyes were most often located in the deeper center area. Northern pike moved over the entire discharge area. All species except largemouth bass moved freely between discharge-affected and unaltered waters. The average numbers of movements per individual per week between heated and unheated areas were the following: northern pike 0.8; yellow perch 1.2; walleye 1.1; largemouth bass, 0.« less

First noninvasive thermal ablation of a brain tumor with MR-guided focused ultrasound

PubMed Central

2014-01-01

Magnetic resonance-guided focused ultrasound surgery (MRgFUS) allows for precise thermal ablation of target tissues. While this emerging modality is increasingly used for the treatment of various types of extracranial soft tissue tumors, it has only recently been acknowledged as a modality for noninvasive neurosurgery. MRgFUS has been particularly successful for functional neurosurgery, whereas its clinical application for tumor neurosurgery has been delayed for various technical and procedural reasons. Here, we report the case of a 63-year-old patient presenting with a centrally located recurrent glioblastoma who was included in our ongoing clinical phase I study aimed at evaluating the feasibility and safety of transcranial MRgFUS for brain tumor ablation. Applying 25 high-power sonications under MR imaging guidance, partial tumor ablation could be achieved without provoking neurological deficits or other adverse effects in the patient. This proves, for the first time, the feasibility of using transcranial MR-guided focused ultrasound to safely ablate substantial volumes of brain tumor tissue. PMID:25671132

Electrical conductivity measurement of excised human metastatic liver tumours before and after thermal ablation.

PubMed

Haemmerich, Dieter; Schutt, David J; Wright, Andrew W; Webster, John G; Mahvi, David M

2009-05-01

We measured the ex vivo electrical conductivity of eight human metastatic liver tumours and six normal liver tissue samples from six patients using the four electrode method over the frequency range 10 Hz to 1 MHz. In addition, in a single patient we measured the electrical conductivity before and after the thermal ablation of normal and tumour tissue. The average conductivity of tumour tissue was significantly higher than normal tissue over the entire frequency range (from 4.11 versus 0.75 mS cm(-1) at 10 Hz, to 5.33 versus 2.88 mS cm(-1) at 1 MHz). We found no significant correlation between tumour size and measured electrical conductivity. While before ablation tumour tissue had considerably higher conductivity than normal tissue, the two had similar conductivity throughout the frequency range after ablation. Tumour tissue conductivity changed by +25% and -7% at 10 Hz and 1 MHz after ablation (0.23-0.29 at 10 Hz, and 0.43-0.40 at 1 MHz), while normal tissue conductivity increased by +270% and +10% at 10 Hz and 1 MHz (0.09-0.32 at 10 Hz and 0.37-0.41 at 1 MHz). These data can potentially be used to differentiate tumour from normal tissue diagnostically.

The Mixed Processing Models Development Of Thermal Fracture And Laser Ablation On Glass Substrate

NASA Astrophysics Data System (ADS)

Huang, Kuo-Cheng; Wu, Wen-Hong; Tseng, Shih-Feng; Hwang, Chi-Hung

2011-01-01

As the industries of cell phone and LCD TV were vigorously flourishing and the manufacturing requirements for LCD glass substrate were getting higher, the thermal fracture cutting technology (TFCT) has progressively become the main technology for LCD glass substrate cutting. Due to using laser as the heat source, the TFCT has many advantages, such as uniform heating, small heat effect zone, and high cutting speed, smooth cutting surface and low residual stress, etc. Moreover, a general laser ablation processing or traditional diamond wheel cutting does not have the last two advantages. The article presents a mixed processing of glass substrate, which consists of TFCT and laser ablation mechanisms, and how to enhance the cutting speed with little ablation laser energy. In this study, a 10W Nd:YAG laser and a 40W CO2 laser are used as the heat source of TFCT and laser ablation processing, respectively. The result indicates that the speed of the mixed processing is more than twice the speed of TFCT. Furthermore, after the mixed processing, the residual stresses in the glass substrates are also smaller.

Microwave thermal ablation: Effects of tissue properties variations on predictive models for treatment planning.

PubMed

Lopresto, Vanni; Pinto, Rosanna; Farina, Laura; Cavagnaro, Marta

2017-08-01

Microwave thermal ablation (MTA) therapy for cancer treatments relies on the absorption of electromagnetic energy at microwave frequencies to induce a very high and localized temperature increase, which causes an irreversible thermal damage in the target zone. Treatment planning in MTA is based on experimental observations of ablation zones in ex vivo tissue, while predicting the treatment outcomes could be greatly improved by reliable numerical models. In this work, a fully dynamical simulation model is exploited to look at effects of temperature-dependent variations in the dielectric and thermal properties of the targeted tissue on the prediction of the temperature increase and the extension of the thermally coagulated zone. In particular, the influence of measurement uncertainty of tissue parameters on the numerical results is investigated. Numerical data were compared with data from MTA experiments performed on ex vivo bovine liver tissue at 2.45GHz, with a power of 60W applied for 10min. By including in the simulation model an uncertainty budget (CI=95%) of ±25% in the properties of the tissue due to inaccuracy of measurements, numerical results were achieved in the range of experimental data. Obtained results also showed that the specific heat especially influences the extension of the thermally coagulated zone, with an increase of 27% in length and 7% in diameter when a variation of -25% is considered with respect to the value of the reference simulation model. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

The effects of 1 kW class arcjet thruster plumes on spacecraft charging and spacecraft thermal control materials

NASA Technical Reports Server (NTRS)

Bogorad, A.; Lichtin, D. A.; Bowman, C.; Armenti, J.; Pencil, E.; Sarmiento, C.

1992-01-01

Arcjet thrusters are soon to be used for north/south stationkeeping on commercial communications satellites. A series of tests was performed to evaluate the possible effects of these thrusters on spacecraft charging and the degradation of thermal control material. During the tests the interaction between arcjet plumes and both charged and uncharged surfaces did not cause any significant material degradation. In addition, firing an arcjet thruster benignly reduced the potential of charged surfaces to near zero.

Quantification of the effect of electrical and thermal parameters on radiofrequency ablation for concentric tumour model of different sizes.

PubMed

Jamil, Muhammad; Ng, E Y K

2015-07-01

Radiofrequency ablation (RFA) has been increasingly used in treating cancer for multitude of situations in various tissue types. To perform the therapy safely and reliably, the effect of critical parameters needs to be known beforehand. Temperature plays an important role in the outcome of the therapy and any uncertainties in temperature assessment can be lethal. This study presents the RFA case of fixed tip temperature where we've analysed the effect of electrical conductivity, thermal conductivity and blood perfusion rate of the tumour and surrounding normal tissue on the radiofrequency ablation. Ablation volume was chosen as the characteristic to be optimised and temperature control was achieved via PID controller. The effect of all 6 parameters each having 3 levels was quantified with minimum number of experiments harnessing the fractional factorial characteristic of Taguchi's orthogonal arrays. It was observed that as the blood perfusion increases the ablation volume decreases. Increasing electrical conductivity of the tumour results in increase of ablation volume whereas increase in normal tissue conductivity tends to decrease the ablation volume and vice versa. Likewise, increasing thermal conductivity of the tumour results in enhanced ablation volume whereas an increase in thermal conductivity of the surrounding normal tissue has a debilitating effect on the ablation volume and vice versa. With increase in the size of the tumour (i.e., 2-3cm) the effect of each parameter is not linear. The parameter effect varies with change in size of the tumour that is manifested by the different gradient observed in ablation volume. Most important is the relative insensitivity of ablation volume to blood perfusion rate for smaller tumour size (2cm) that is also in accordance with the previous results presented in literature. These findings will provide initial insight for safe, reliable and improved treatment planning perceptively. Copyright © 2015 Elsevier Ltd. All

Patient specific optimization-based treatment planning for catheter-based ultrasound hyperthermia and thermal ablation

NASA Astrophysics Data System (ADS)

Prakash, Punit; Chen, Xin; Wootton, Jeffery; Pouliot, Jean; Hsu, I.-Chow; Diederich, Chris J.

2009-02-01

to model thermal ablation, including the addition of temperature dependent attenuation, perfusion, and tissue damage. Pilot point control at the target boundaries was implemented to control power delivery to each transducer section, simulating an approach feasible for MR guided procedures. The computer model of thermal ablation was evaluated on representative patient anatomies to demonstrate the feasibility of using catheter-based ultrasound thermal ablation for treatment of benign prostate hyperplasia (BPH) and prostate cancer, and to assist in designing applicators and treatment delivery strategies.

CHAP III- CHARRING ABLATOR PROGRAM FOR ADVANCED INVESTIGATION OF THERMAL PROTECTION SYSTEMS FOR ENTRY

NASA Technical Reports Server (NTRS)

Stroud, C. W.

1994-01-01

The transient response of a thermal protection material to heat applied to the surface can be calculated using the CHAP III computer program. CHAP III can be used to analyze pyrolysis gas chemical kinetics in detail and examine pyrolysis reactions-indepth. The analysis includes the deposition of solid products produced by chemical reactions in the gas phase. CHAP III uses a modelling technique which can approximate a wide range of ablation problems. The energy equation used in CHAP III incorporates pyrolysis (both solid and gas reactions), convection, conduction, storage, work, kinetic energy, and viscous dissipation. The chemically reacting components of the solid are allowed to vary as a function of position and time. CHAP III employs a finite difference method to approximate the energy equations. Input values include specific heat, thermal conductivity, thermocouple locations, enthalpy, heating rates, and a description of the chemical reactions expected. The output tabulates the temperature at locations throughout the ablator, gas flow within the solid, density of the solid, weight of pyrolysis gases, and rate of carbon deposition. A sample case is included, which analyzes an ablator material containing several pyrolysis reactions subjected to an environment typical of entry at lunar return velocity. CHAP III is written in FORTRAN IV for batch execution and has been implemented on a CDC CYBER 170 series computer operating under NOS with a central memory requirement of approximately 102K (octal) of 60 bit words. This program was developed in 1985.

Light Weight Ceramic Ablators for Mars Follow-on Mission Vehicle Thermal Protection System

NASA Technical Reports Server (NTRS)

Tran, Huy K.; Rasky, Daniel J.; Hsu, Ming-Ta; Turan, Ryan

1994-01-01

New Light Weight Ceramic Ablators (LCA) were produced by using ceramic and carbon fibrous substrates, impregnated with silicone and phenolic resins. The special infiltration techniques (patent pending) were developed to control the amount of organic resins in the highly porous fiber matrices so that the final densities of LCA's range from 0.22 to 0.24 g/cc. This paper presents the thermal and ablative performance of the Silicone Impregnated Reusable Ceramic Ablators (SIRCA) in simulated entry conditions for Mars-Pathfinder in the Ames 60 MW Interaction Heating Facility (I HF). Arc jet test results yielded no evidence of char erosion and mass loss at high stagnation pressures to 0.25 atm. Minimal silica melt was detected on surface char at a stagnation pressure of 0.31 atm. Four ceramic substrates were used in the production of SIRCA's to obtain the effective of boron oxide present in substrate so the thermal performance of SIRCA's. A sample of SIRCA was also exposed to the same heating condition for five cycles and no significant mass loss or recession was observed. Tensile testing established that the SIRCA tensile strength is about a factor of two higher than that of the virgin substrates. Thermogravimetric Analysis (TGA) of the char in nitrogen and air showed no evidence of free carbon in the char. Scanning Electron Microscopy of the post test sample showed that the char surface consists of a fibrous structure that was sealed with a thin layer of silicon oxide melt.

[Application of TB type thermal balloon endometrial ablation for the treatment of abnormal uterine bleeding].

PubMed

Wang, W; Zhai, Y; Zhang, Z H; Li, Y; Zhang, Z Y

2016-11-08

Objective: To investigate the clinical efficacy, safety and promotion value of TB type thermal balloon endometrial ablation in the treatment of abnormal uterine bleeding. Methods: Fourty three patients who had received TB type endometrial ablation system for treatment of abnormal uterine bleeding from January, 2015 to January, 2016 in theDepartment of gynecology, Beijing Chaoyang Hospital were enrolled in this study. The intra-operative and post-operative complications and improvement of abnormal uterine bleeding and dysmenorrhea were observed. Results: There were nointra-operative complication occurred, such as uterine perforation, massive hemorrhage or surrounding organ damage. At 6 months after operation, 32 patients developed amenorrhea, 6 developed menstrual spotting, 3 developed menstruation with a small volume and 1 had a normal menstruation. No menstruation with an increased volume occurred. The occurrence of amenorrhea was 76.19% and the response rate was 97.62%.At 6 months after operation, 1 case had no response, 2 cases had partial response and 11 cases had complete response among the 14 cases of pre-operative dysmenorrhea; only 3 cases still had anemia among the 23 cases of pre-operative anemia. Compared with before treatment, patients with dysmenorrhea and anemia both significantly reduced with a statistically significant difference( P <0.01). Conclusion: TB type thermal balloon endometrial ablation has a significant efficacy with high safety for the treatment of abnormal uterine bleeding, which could have clinical promotion practice.

Near-IR Imaging of Thermal Changes in Enamel during Laser Ablation.

PubMed

Maung, Linn H; Lee, Chulsung; Fried, Daniel

2010-03-05

The objective of this work was to observe the various thermal-induced optical changes that occur in the near-infrared (NIR) during drilling in dentin and enamel with the laser and the high-speed dental handpiece. Tooth sections of ~ 3 mm-thickness were prepared from extracted human incisors (N=60). Samples were ablated with a mechanically scanned CO(2) laser operating at a wavelength of 9.3-µm, a 300-Hz laser pulse repetition rate, and a laser pulse duration of 10-20 µs. An InGaAs imaging camera was used to acquire real-time NIR images at 1300-nm of thermal and mechanical changes (cracks). Enamel was rapidly removed by the CO(2) laser without peripheral thermal damage by mechanically scanning the laser beam while a water spray was used to cool the sample. Comparison of the peripheral thermal and mechanical changes produced while cutting with the laser and the high-speed hand-piece suggest that enamel and dentin can be removed at high speed by the CO(2) laser without excessive peripheral thermal or mechanical damage. Only 2 of the 15 samples ablated with the laser showed the formation of small cracks while 9 out of 15 samples exhibited crack formation with the dental hand-piece. The first indication of thermal change is a decrease in transparency due to loss of the mobile water from pores in the enamel which increase light-scattering. To test the hypothesis that peripheral thermal changes were caused by loss of mobile water in the enamel, thermal changes were intentionally induced by heating the surface. The mean attenuation coefficient of enamel increased significantly from 2.12 ± 0.82 to 5.08 ± 0.98 with loss of mobile water due to heating.

Near-IR imaging of thermal changes in enamel during laser ablation

NASA Astrophysics Data System (ADS)

Maung, Linn H.; Lee, Chulsung; Fried, Daniel

2010-02-01

The objective of this work was to observe the various thermal-induced optical changes that occur in the near-infrared (NIR) during drilling in dentin and enamel with the laser and the high-speed dental handpiece. Tooth sections of ~ 3 mm-thickness were prepared from extracted human incisors (N=60). Samples were ablated with a mechanically scanned CO2 laser operating at a wavelength of 9.3-μm, a 300-Hz laser pulse repetition rate, and a laser pulse duration of 10-20 μs. An InGaAs imaging camera was used to acquire real-time NIR images at 1300-nm of thermal and mechanical changes (cracks). Enamel was rapidly removed by the CO2 laser without peripheral thermal damage by mechanically scanning the laser beam while a water spray was used to cool the sample. Comparison of the peripheral thermal and mechanical changes produced while cutting with the laser and the high-speed hand-piece suggest that enamel and dentin can be removed at high speed by the CO2 laser without excessive peripheral thermal or mechanical damage. Only 2 of the 15 samples ablated with the laser showed the formation of small cracks while 9 out of 15 samples exhibited crack formation with the dental hand-piece. The first indication of thermal change is a decrease in transparency due to loss of the mobile water from pores in the enamel which increase lightscattering. To test the hypothesis that peripheral thermal changes were caused by loss of mobile water in the enamel, thermal changes were intentionally induced by heating the surface. The mean attenuation coefficient of enamel increased significantly from 2.12 +/- 0.82 to 5.08 +/- 0.98 with loss of mobile water due to heating.

Near-IR Imaging of Thermal Changes in Enamel during Laser Ablation

PubMed Central

Maung, Linn H.; Lee, Chulsung; Fried, Daniel

2011-01-01

The objective of this work was to observe the various thermal-induced optical changes that occur in the near-infrared (NIR) during drilling in dentin and enamel with the laser and the high-speed dental handpiece. Tooth sections of ~ 3 mm-thickness were prepared from extracted human incisors (N=60). Samples were ablated with a mechanically scanned CO2 laser operating at a wavelength of 9.3-µm, a 300-Hz laser pulse repetition rate, and a laser pulse duration of 10–20 µs. An InGaAs imaging camera was used to acquire real-time NIR images at 1300-nm of thermal and mechanical changes (cracks). Enamel was rapidly removed by the CO2 laser without peripheral thermal damage by mechanically scanning the laser beam while a water spray was used to cool the sample. Comparison of the peripheral thermal and mechanical changes produced while cutting with the laser and the high-speed hand-piece suggest that enamel and dentin can be removed at high speed by the CO2 laser without excessive peripheral thermal or mechanical damage. Only 2 of the 15 samples ablated with the laser showed the formation of small cracks while 9 out of 15 samples exhibited crack formation with the dental hand-piece. The first indication of thermal change is a decrease in transparency due to loss of the mobile water from pores in the enamel which increase light-scattering. To test the hypothesis that peripheral thermal changes were caused by loss of mobile water in the enamel, thermal changes were intentionally induced by heating the surface. The mean attenuation coefficient of enamel increased significantly from 2.12 ± 0.82 to 5.08 ± 0.98 with loss of mobile water due to heating. PMID:21935291

Noninvasive thermal ablation of hepatocellular carcinoma by using magnetic resonance imaging-guided focused ultrasound.

PubMed

Jolesz, Ferenc A; Hynynen, Kullervo; McDannold, Nathan; Freundlich, David; Kopelman, Doron

2004-11-01

A number of minimally invasive methods have been tested for the thermal ablation of liver tumors as an alternative to surgical resection. The use of focused ultrasound transducers to ablate deep tumors offers the first completely noninvasive alternative to these techniques. By increasing the flexibility of this technology with modern phased-array transducer design and by combining it with magnetic resonance imaging for targeting and online guidance, a powerful tool results with the potential to offer treatment to a larger population of patients, to reduce trauma to the patient, and to reduce the cost of treatment. In this article, we review previous work with focused ultrasound in the liver and recent experimental results with magnetic resonance imaging guidance.

Numerical models to evaluate the temperature increase induced by ex vivo microwave thermal ablation.

PubMed

Cavagnaro, M; Pinto, R; Lopresto, V

2015-04-21

Microwave thermal ablation (MTA) therapies exploit the local absorption of an electromagnetic field at microwave (MW) frequencies to destroy unhealthy tissue, by way of a very high temperature increase (about 60 °C or higher). To develop reliable interventional protocols, numerical tools able to correctly foresee the temperature increase obtained in the tissue would be very useful. In this work, different numerical models of the dielectric and thermal property changes with temperature were investigated, looking at the simulated temperature increments and at the size of the achievable zone of ablation. To assess the numerical data, measurement of the temperature increases close to a MTA antenna were performed in correspondence with the antenna feed-point and the antenna cooling system, for increasing values of the radiated power. Results show that models not including the changes of the dielectric and thermal properties can be used only for very low values of the power radiated by the antenna, whereas a good agreement with the experimental values can be obtained up to 20 W if water vaporization is included in the numerical model. Finally, for higher power values, a simulation that dynamically includes the tissue's dielectric and thermal property changes with the temperature should be performed.

Optoacoustic monitoring of cutting efficiency and thermal damage during laser ablation.

PubMed

Bay, Erwin; Douplik, Alexandre; Razansky, Daniel

2014-05-01

Successful laser surgery is characterized by a precise cut and effective hemostasis with minimal collateral thermal damage to the adjacent tissues. Consequently, the surgeon needs to control several parameters, such as power, pulse repetition rate, and velocity of movements. In this study we propose utilizing optoacoustics for providing the necessary real-time feedback of cutting efficiency and collateral thermal damage. Laser ablation was performed on a bovine meat slab using a Q-switched Nd-YAG laser (532 nm, 4 kHz, 18 W). Due to the short pulse duration of 7.6 ns, the same laser has also been used for generation of optoacoustic signals. Both the shockwaves, generated due to tissue removal, as well as the normal optoacoustic responses from the surrounding tissue were detected using a single broadband piezoelectric transducer. It has been observed that the rapid reduction in the shockwave amplitude occurs as more material is being removed, indicating decrease in cutting efficiency, whereas gradual decrease in the optoacoustic signal likely corresponds to coagulation around the ablation crater. Further heating of the surrounding tissue leads to carbonization accompanied by a significant shift in the optoacoustic spectra. Our results hold promise for real-time monitoring of cutting efficiency and collateral thermal damage during laser surgery. In practice, this could eventually facilitate development of automatic cut-off mechanisms that will guarantee an optimal tradeoff between cutting and heating while avoiding severe thermal damage to the surrounding tissues.

Validation of PICA Ablation and Thermal-Response Model at Low Heat Flux

NASA Technical Reports Server (NTRS)

Milos, Frank S.; Chen, Yih-Kanq

2009-01-01

Phenolic Impregnated Carbon Ablator (PICA) was the forebody heatshield material on the Stardust sample-return capsule and is also a primary candidate material for the Mars Science Lander (MSL), the Orion Crew Module, and the SpaceX Dragon vehicle. As part of the heatshield qualification for Orion, physical and thermal properties of virgin and charred PICA were measured, and an ablation and thermal response model was developed. We validated the model by comparing it with recession and temperature data from stagnation arcjet tests conducted over a wide range of stagnation heat flux of 107 to 1102 W/sq cm. The effect of orthotropic thermal conductivity was evident in the thermal response of the arcjet models. In general, model predictions compared well with the data; however, the uncertainty of the recession prediction was greatest for heat fluxes below 200 W/sq cm. More recent MSL testing focused on the low heat flux regime of 45 to 250 W/sq cm. The new results confirm the recession uncertainty, especially for pressures below 6 kPa. In this work we focus on improving the model predictions for MSL and Orion tests below 250 W/sq cm.

A breakdown surface model for thermal backscattering from the exhaust plume of a space-based HF laser

NASA Astrophysics Data System (ADS)

Falcovitz, J.

1986-06-01

The purpose of this report is to present a breakdown surface model for evaluating thermal backscattering flow from the supersonic exhaust plume of a gaseous mixture of H, HF, H2, DF and He. Fluxes of these species are considered separately. The model is carefully analyzed and is shown to overestimate the flux. Actual flux levels of the heavy corrosive molecules (HD, DF) have been found to be exceedingly low. It is concluded that the contribution of thermal backscattering to contaminating flux of HF and DF can be neglected.

Thermal evolution of flattening slab and formation of wet plume: Insight into intraplate volcanism in East Asia

NASA Astrophysics Data System (ADS)

He, L.

2016-12-01

Geophysical observations imply the intraplate volcanism in East Asia is related to dehydration of slab stagnating in the transition zone. To better understand the dynamics of such process, a thermochemical mantle convection model is constructed to simulate numerically the thermal evolution of slab and the transportation of water in the process of subduction. Equation of water transfer is explicitly included, and water effects on density and viscosity are considered. Modeling results indicate that behavior of water transport relates closely to the transient thermal state and viscosities both of the slab and the surrounding mantle. Generally, initiation of wet plume is mainly influenced by the viscosity of the wet layer in the uppermost slab, whereas the horizontal distance of water transport and its ascending rate is affected strongly by the viscosity of the big mantle wedge. Whether water can be carried successfully by slab into the mantle transition zone and trigger wet plume at the surface of flattening slab depends on the viscosity contrast between wet layer and surrounding mantle. The complex fluid flow superposed by corner flow and free thermal convection controls the water transport pattern in the upper mantle. Modeling results together with previous modeling infer three stages of water circulation in the big mantle wedge: 1) water is brought into the mantle transition zone by downward subducting slab when water layer viscosity is much higher than the wedge viscosity, otherwise water is released at shallow depth near wedge tip; 2) wet plume generates from surface of warm flattening slab if containing water, which arrives at the lithospheric base and induces melting; and 3) water spreads all over the big mantle wedge, mantle convection within the big mantle wedge becomes more active, leading to upwelling of asthenosphere and erosion of the overriding continental lithosphere. Wet plume from the flattening Pacific Plate can explain the intraplate Cenozoic

Analysis of Indium Tin Oxide Film Using Argon Fluroide (ArF) Laser-Excited Atomic Fluorescence of Ablated Plumes.

PubMed

Ho, Sut Kam; Garcia, Dario Machado

2017-04-01

A two-pulse laser-excited atomic fluorescence (LEAF) technique at 193 nm wavelength was applied to the analysis of indium tin oxide (ITO) layer on polyethylene terephthalate (PET) film. Fluorescence emissions from analytes were induced from plumes generated by first laser pulse. Using this approach, non-selective LEAF can be accomplished for simultaneous multi-element analysis and it overcomes the handicap of strict requirement for laser excitation wavelength. In this study, experimental conditions including laser fluences, times for gating and time delay between pulses were optimized to reveal high sensitivity with minimal sample destruction and penetration. With weak laser fluences of 100 and 125 mJ/cm 2 for 355 and 193 nm pulses, detection limits were estimated to be 0.10% and 0.43% for Sn and In, respectively. In addition, the relation between fluorescence emissions and number of laser shots was investigated; reproducible results were obtained for Sn and In. It shows the feasibility of depth profiling by this technique. Morphologies of samples were characterized at various laser fluences and number of shots to examine the accurate penetration. Images of craters were also investigated using scanning electron microscopy (SEM). The results demonstrate the imperceptible destructiveness of film after laser shot. With such weak laser fluences and minimal destructiveness, this LEAF technique is suitable for thin-film analysis.

Multispectral thermal infrared mapping of sulfur dioxide plumes: A case study from the East Rift Zone of Kilauea Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Realmuto, V. J.; Sutton, A. J.; Elias, T.

1997-07-01

The synoptic perspective and rapid mode of data acquisition provided by remote sensing are well suited for the study of volcanic SO2 plumes. In this paper we describe a plume-mapping procedure that is based on image data acquired with NASA's airborne thermal infrared multispectral scanner (TIMS) and apply the procedure to TIMS data collected over the East Rift Zone of Kilauea Volcano, Hawaii, on September 30, 1988. These image data covered the Pu`u `O `o and Kupaianaha vents and a skylight in the lava tube that was draining the Kupaianaha lava pond. Our estimate of the SO2 emission rate from Pu`u `O `o (17-20 kg s-1) is roughly twice the average of estimates derived from correlation spectrometer (COSPEC) measurements collected 10 days prior to the TIMS overflight (10 kg s-1). The agreement between the TIMS and COSPEC results improves when we compare SO2 burden estimates, which are relatively independent of wind speed. We demonstrate the feasibility of mapping Pu`u `O `o - scale SO2 plumes from space in anticipation of the 1998 launch of the advanced spaceborne thermal emission and reflectance radiometer (ASTER).

Multispectral thermal infrared mapping of sulfur dioxide plumes: A case study from the East Rift Zone of Kilauea Volcano, Hawaii

USGS Publications Warehouse

Realmuto, V.J.; Sutton, A.J.; Elias, T.

1997-01-01

The synoptic perspective and rapid mode of data acquisition provided by remote sensing are well suited for the study of volcanic SO2 plumes. In this paper we describe a plume-mapping procedure that is based on image data acquired with NASA's airborne thermal infrared multispectral scanner (TIMS) and apply the procedure to TIMS data collected over the East Rift Zone of Kilauea Volcano, Hawaii, on September 30, 1988. These image data covered the Pu'u 'O'o and Kupaianaha vents and a skylight in the lava tube that was draining the Kupaianaha lava pond. Our estimate of the SO2 emission rate from Pu'u 'O'o (17 - 20 kg s-1) is roughly twice the average of estimates derived from correlation spectrometer (COSPEC) measurements collected 10 days prior to the TIMS overflight (10 kg s-1). The agreement between the TIMS and COSPEC results improves when we compare SO2 burden estimates, which are relatively independent of wind speed. We demonstrate the feasibility of mapping Pu'u 'O'o - scale SO2 plumes from space in anticipation of the 1998 launch of the advanced spaceborne thermal emission and reflectance radiometer (ASTER). Copyright 1997 by the American Geophysical Union.

Lightweight Ablative and Ceramic Thermal Protection System Materials for NASA Exploration Systems Vehicles

NASA Technical Reports Server (NTRS)

Valentine, Peter G.; Lawrence, Timothy W.; Gubert, Michael K.; Milos, Frank S.; Kiser, James D.; Ohlhorst, Craig W.; Koenig, John R.

2006-01-01

As a collaborative effort among NASA Centers, the "Lightweight Nonmetallic Thermal Protection Materials Technology" Project was set up to assist mission/vehicle design trade studies, to support risk reduction in thermal protection system (TPS) material selections, to facilitate vehicle mass optimization, and to aid development of human-rated TPS qualification and certification plans. Missions performing aerocapture, aerobraking, or direct aeroentry rely on advanced heatshields that allow reductions in spacecraft mass by minimizing propellant requirements. Information will be presented on candidate materials for such reentry approaches and on screening tests conducted (material property and space environmental effects tests) to evaluate viable candidates. Seventeen materials, in three classes (ablatives, tiles, and ceramic matrix composites), were studied. In additional to physical, mechanical, and thermal property tests, high heat flux laser tests and simulated-reentry oxidation tests were performed. Space environmental effects testing, which included exposures to electrons, atomic oxygen, and hypervelocity impacts, was also conducted.

Elucidating the thermal, chemical, and mechanical mechanisms of ultraviolet ablation in poly(methyl methacrylate) via molecular dynamics simulations.

PubMed

Conforti, Patrick F; Prasad, Manish; Garrison, Barbara J

2008-08-01

[Figure: see text]. Laser ablation harnesses photon energy to remove material from a surface. Although applications such as laser-assisted in situ keratomileusis (LASIK) surgery, lithography, and nanoscale device fabrication take advantage of this process, a better understanding the underlying mechanism of ablation in polymeric materials remains much sought after. Molecular simulation is a particularly attractive technique to study the basic aspects of ablation because it allows control over specific process parameters and enables observation of microscopic mechanistic details. This Account describes a hybrid molecular dynamics-Monte Carlo technique to simulate laser ablation in poly(methyl methacrylate) (PMMA). It also discusses the impact of thermal and chemical excitation on the ensuing ejection processes. We used molecular dynamics simulation to study the molecular interactions in a coarse-grained PMMA substrate following photon absorption. To ascertain the role of chemistry in initiating ablation, we embedded a Monte Carlo protocol within the simulation framework. These calculations permit chemical reactions to occur probabilistically during the molecular dynamics calculation using predetermined reaction pathways and Arrhenius rates. With this hybrid scheme, we can examine thermal and chemical pathways of decomposition separately. In the simulations, we observed distinct mechanisms of ablation for each type of photoexcitation pathway. Ablation via thermal processes is governed by a critical number of bond breaks following the deposition of energy. For the case in which an absorbed photon directly causes a bond scission, ablation occurs following the rapid chemical decomposition of material. A detailed analysis of the processes shows that a critical energy for ablation can describe this complex series of events. The simulations show a decrease in the critical energy with a greater amount of photochemistry. Additionally, the simulations demonstrate the effects

Validation of a Three-Dimensional Ablation and Thermal Response Simulation Code

NASA Technical Reports Server (NTRS)

Chen, Yih-Kanq; Milos, Frank S.; Gokcen, Tahir

2010-01-01

The 3dFIAT code simulates pyrolysis, ablation, and shape change of thermal protection materials and systems in three dimensions. The governing equations, which include energy conservation, a three-component decomposition model, and a surface energy balance, are solved with a moving grid system to simulate the shape change due to surface recession. This work is the first part of a code validation study for new capabilities that were added to 3dFIAT. These expanded capabilities include a multi-block moving grid system and an orthotropic thermal conductivity model. This paper focuses on conditions with minimal shape change in which the fluid/solid coupling is not necessary. Two groups of test cases of 3dFIAT analyses of Phenolic Impregnated Carbon Ablator in an arc-jet are presented. In the first group, axisymmetric iso-q shaped models are studied to check the accuracy of three-dimensional multi-block grid system. In the second group, similar models with various through-the-thickness conductivity directions are examined. In this group, the material thermal response is three-dimensional, because of the carbon fiber orientation. Predictions from 3dFIAT are presented and compared with arcjet test data. The 3dFIAT predictions agree very well with thermocouple data for both groups of test cases.

Development of a 3D ultrasound-guided system for thermal ablation of liver tumors

NASA Astrophysics Data System (ADS)

Neshat, Hamid R. S.; Cool, Derek W.; Barker, Kevin; Gardi, Lori; Kakani, Nirmal; Fenster, Aaron

2013-03-01

Two-dimensional ultrasound (2D US) imaging is commonly used for diagnostic and intraoperative guidance of interventional abdominal procedures including percutaneous thermal ablation of focal liver tumors with radiofrequency (RF) or microwave (MW) induced energy. However, in many situations 2D US may not provide enough anatomical detail and guidance information. Therefore, intra-procedural CT or MR imaging are used in many centers for guidance purposes. These modalities are costly and are mainly utilized to confirm tool placement rather than guiding the insertion. Three-dimensional ultrasound (3D US) has been introduced to address these issues. In this paper, we present our integrated solution to provide 3D US images using a newly developed mechanical transducer with a large field-ofview and without the need for external tracking devices to combine diagnostic and planning information of different modalities for intraoperative guidance. The system provides tools to segment the target(s), plan the treatment, and detect the ablation applicators during the procedure for guiding purposes. We present experimental results used to ensure that our system generates accurate measurements and our early clinical evaluation results. The results suggest that 3D US used for focal liver ablation can provide a more reliable planning and guidance tool compared to 2D US only, and in many cases offers comparable measurements to other alternatives at significantly lower cost, faster time and with no harmful radiation.

Pathology of non-thermal irreversible electroporation (N-TIRE)-induced ablation of the canine brain.

PubMed

Rossmeisl, John H; Garcia, Paulo A; Roberston, John L; Ellis, Thomas L; Davalos, Rafael V

2013-01-01

This study describes the neuropathologic features of normal canine brain ablated with non-thermal irreversible electroporation (N-TIRE). The parietal cerebral cortices of four dogs were treated with N-TIRE using a dose-escalation protocol with an additional dog receiving sham treatment. Animals were allowed to recover following N-TIRE ablation and the effects of treatment were monitored with clinical and magnetic resonance imaging examinations. Brains were subjected to histopathologic and ultrastructural assessment along with Bcl-2, caspase-3, and caspase-9 immunohistochemical staining following sacrifice 72 h post-treatment. Adverse clinical effects of N-TIRE were only observed in the dog treated at the upper energy tier. MRI and neuropathologic examinations indicated that N-TIRE ablation resulted in focal regions of severe cytoarchitectural and blood-brain-barrier disruption. Lesion size correlated to the intensity of the applied electrical field. N-TIRE-induced lesions were characterized by parenchymal necrosis and hemorrhage; however, large blood vessels were preserved. A transition zone containing parenchymal edema, perivascular inflammatory cuffs, and reactive gliosis was interspersed between the necrotic focus and normal neuropil. Apoptotic labeling indices were not different between the N-TIRE-treated and control brains. This study identified N-TIRE pulse parameters that can be used to safely create circumscribed foci of brain necrosis while selectively preserving major vascular structures.

Thermal effect of laser ablation on the surface of carbon fiber reinforced plastic during laser processing

NASA Astrophysics Data System (ADS)

Ohkubo, Tomomasa; Sato, Yuji; Matsunaga, Ei-ichi; Tsukamoto, Masahiro

2018-02-01

Although laser processing is widely used for many applications, the cutting quality of carbon fiber reinforced plastic (CFRP) decreases around the heat-affected zone (HAZ) during laser processing. Carbon fibers are exposed around the HAZ, and tensile strength decreases with increasing length of the HAZ. Some theoretical studies of thermal conductions that do not consider fluid dynamics have been performed; however, theoretical considerations that include the dynamics of laser ablation are scarce. Using removed mass and depth observed from experiments, the dynamics of laser ablation of CFRP with high-temperature and high-pressure of compressive gas is simulated herein. In this calculation, the mushroom-like shape of laser ablation is qualitatively simulated compared with experiments using a high-speed camera. Considering the removal temperature of the resin and the temperature distribution at each point on the surface, the simulation results suggest that a wide area of the resin is removed when the processing depth is shallow, and a rounded kerf is generated as the processing depth increases.

Thermal protection for hypervelocity flight in earth's atmosphere by use of radiation backscattering ablating materials

NASA Technical Reports Server (NTRS)

Howe, John T.; Yang, Lily

1991-01-01

A heat-shield-material response code predicting the transient performance of a material subject to the combined convective and radiative heating associated with the hypervelocity flight is developed. The code is dynamically interactive to the heating from a transient flow field, including the effects of material ablation on flow field behavior. It accomodates finite time variable material thickness, internal material phase change, wavelength-dependent radiative properties, and temperature-dependent thermal, physical, and radiative properties. The equations of radiative transfer are solved with the material and are coupled to the transfer energy equation containing the radiative flux divergence in addition to the usual energy terms.

Lightning Strike Ablation Damage Influence Factors Analysis of Carbon Fiber/Epoxy Composite Based on Coupled Electrical-Thermal Simulation

NASA Astrophysics Data System (ADS)

Yin, J. J.; Chang, F.; Li, S. L.; Yao, X. L.; Sun, J. R.; Xiao, Y.

2017-10-01

According to the mathematical analysis model constructed on the basis of energy-balance relationship in lightning strike, and accompany with the simplified calculation strategy of composite resin pyrolysis degree dependent electrical conductivity, an effective three dimensional thermal-electrical coupling analysis finite element model of composite laminate suffered from lightning current was established based on ABAQUS, to elucidate the effects of lighting current waveform parameters and thermal/electrical properties of composite laminate on the extent of ablation damage. Simulated predictions agree well with the composite lightning strike directed effect experimental data, illustrating the potential accuracy of the constructed model. The analytical results revealed that extent of composite lightning strike ablation damage can be characterized by action integral validly, there exist remarkable power function relationships between action integral and visual damage area, projected damage area, maximum damage depth and damage volume of ablation damage, and enhancing the electrical conductivity and specific heat of composite, ablation damage will be descended obviously, power function relationships also exist between electrical conductivity, specific heat and ablation damage, however, the impact of thermal conductivity on the extent of ablation damage is not notable. The conclusions obtained provide some guidance for composite anti-lightning strike structure-function integration design.

RF tumour ablation: computer simulation and mathematical modelling of the effects of electrical and thermal conductivity.

PubMed

Lobo, S M; Liu, Z-J; Yu, N C; Humphries, S; Ahmed, M; Cosman, E R; Lenkinski, R E; Goldberg, W; Goldberg, S N

2005-05-01

This study determined the effects of thermal conductivity on RF ablation tissue heating using mathematical modelling and computer simulations of RF heating coupled to thermal transport. Computer simulation of the Bio-Heat equation coupled with temperature-dependent solutions for RF electric fields (ETherm) was used to generate temperature profiles 2 cm away from a 3 cm internally-cooled electrode. Multiple conditions of clinically relevant electrical conductivities (0.07-12 S m-1) and 'tumour' radius (5-30 mm) at a given background electrical conductivity (0.12 S m-1) were studied. Temperature response surfaces were plotted for six thermal conductivities, ranging from 0.3-2 W m-1 degrees C (the range of anticipated clinical and experimental systems). A temperature response surface was obtained for each thermal conductivity at 25 electrical conductivities and 17 radii (n=425 temperature data points). The simulated temperature response was fit to a mathematical model derived from prior phantom data. This mathematical model is of the form (T=a+bRc exp(dR) s(f) exp(g)(s)) for RF generator-energy dependent situations and (T=h+k exp(mR)+n?exp(p)(s)) for RF generator-current limited situations, where T is the temperature (degrees C) 2 cm from the electrode and a, b, c, d, f, g, h, k, m, n and p are fitting parameters. For each of the thermal conductivity temperature profiles generated, the mathematical model fit the response surface to an r2 of 0.97-0.99. Parameters a, b, c, d, f, k and m were highly correlated to thermal conductivity (r2=0.96-0.99). The monotonic progression of fitting parameters permitted their mathematical expression using simple functions. Additionally, the effect of thermal conductivity simplified the above equation to the extent that g, h, n and p were found to be invariant. Thus, representation of the temperature response surface could be accurately expressed as a function of electrical conductivity, radius and thermal conductivity. As a result

Acoustic Droplet Vaporization for Enhancement of Thermal Ablation by High Intensity Focused Ultrasound

PubMed Central

Zhang, Man; Fabiilli, Mario L.; Haworth, Kevin J.; Padilla, Frederic; Swanson, Scott D.; Kripfgans, Oliver D.; Carson, Paul L.; Fowlkes, J. Brian

2011-01-01

Rationale and Objectives Acoustic droplet vaporization (ADV) shows promise for spatial control and acceleration of thermal lesion production. Our hypothesis was that microbubbles generated by ADV could enhance high intensity focused ultrasound (HIFU) thermal ablation by controlling and increasing local energy absorption. Materials and Methods Thermal lesions were produced in tissue-mimicking phantoms using focused ultrasound (1.44 MHz) with a focal intensity of 4000 W·cm-2 in degassed water at 37°C. The average lesion volume was measured by visible change in optical opacity and by T2-weighted MRI. In addition, in vivo HIFU lesions were generated in a canine liver before and after an intravenous injection of droplets with a similar acoustic setup. Results Thermal lesions were seven-fold larger in phantoms containing droplets (3×105 droplets/mL) compared to phantoms without droplets. The mean lesion volume with a 2 s HIFU exposure in droplet-containing phantoms was comparable to that made by a 5 s exposure in phantoms without droplets. In the in vivo study, the average lesion volumes without and with droplets were 0.017 ± 0.006 cm3 (n = 4, 5 s exposure) and 0.265 ± 0.005 cm3 (n = 3, 5 s exposure), respectively – a factor of 15 difference. The shape of ADV bubbles imaged with B-mode ultrasound was very similar to the actual lesion shape as measured optically and by MRI. Conclusion ADV bubbles may facilitate clinical HIFU ablation by reducing treatment time or requisite in situ total acoustic power, and provide ultrasonic imaging feedback of the thermal therapy. PMID:21703883

Thermal History of CBb Chondrules and Cooling Rate Distributions of Ejecta Plumes

NASA Astrophysics Data System (ADS)

Hewins, R. H.; Condie, C.; Morris, M.; Richardson, M. L. A.; Ouellette, N.; Metcalf, M.

2018-03-01

It has been proposed that some meteorites, CB and CH chondrites, contain material formed as a result of a protoplanetary collision during accretion. Their melt droplets (chondrules) and FeNi metal are proposed to have formed by evaporation and condensation in the resulting impact plume. We observe that the skeletal olivine (SO) chondrules in CBb chondrites have a blebby texture and an enrichment in refractory elements not found in normal chondrules. Because the texture requires complete melting, their maximum liquidus temperature of 1928 K represents a minimum temperature for the putative plume. Dynamic crystallization experiments show that the SO texture can be created only by brief reheating episodes during crystallization, giving a partial dissolution of olivine. The ejecta plume formed in a smoothed particle hydrodynamics simulation served as the basis for 3D modeling with the adaptive mesh refinement code FLASH4.3. Tracer particles that move with the fluid cells are used to measure the in situ cooling rates. Their cooling rates are ∼10,000 K hr‑1 briefly at peak temperature and, in the densest regions of the plume, ∼100 K hr‑1 for 1400–1600 K. A small fraction of cells is seen to be heating at any one time, with heating spikes explained by the compression of parcels of gas in a heterogeneous patchy plume. These temperature fluctuations are comparable to those required in crystallization experiments. For the first time, we find an agreement between experiments and models that supports the plume model specifically for the formation of CBb chondrules.

Characterization of Pancreatic Cancer Cell Thermal Response to Heat Ablation or Cryoablation.

PubMed

Baumann, Kenneth W; Baust, John M; Snyder, Kristi K; Baust, John G; Van Buskirk, Robert G

2017-08-01

One of the most lethal carcinomas is pancreatic cancer. As standard treatment using chemotherapy and radiation has shown limited success, thermal regimens (cryotherapy or heat ablation) are emerging as viable alternatives. Although promising, our understanding of pancreatic cancer response to thermal ablation remains limited. In this study, we investigated the thermal responses of 2 pancreatic cancer cell lines in an effort to identify the minimum lethal temperature needed for complete cell death to provide guidance for in vivo applications. PANC-1 and BxPC-3 were frozen (-10°C to -25°C) or heated (45°C-50°C) in single and repeated exposure regimes. Posttreatment survival and recovery were analyzed using alamarBlue assay over a 7-day interval. Modes of cell death were assessed using fluorescence microscopy (calcein acetoxymethyl ester/propidium iodide) and flow cytometry (YO-PRO-1/propidium iodide). Freezing to -10°C resulted in minimal cell death. Exposure to -15°C had a mild impact on PANC-1 survival (93%), whereas BxPC-3 was more severely damaged (33%). Exposure to -20°C caused a significant reduction in viability (PANC-1 = 23%; BxPC-3 = 2%) whereas -25°C yielded complete death. Double freezing exposure was more effective than single exposure. Repeat exposure to -15°C resulted in complete death of BxPC-3, whereas -20°C severely impacted PANC-1 (7%). Heating to 45°C resulted in minimum cell death. Exposure to 48°C yielded a slight increase in cell loss (PANC-1 = 85%; BxPC-3 = 98%). Exposure to 50°C caused a significant decline (PANC-1 = 70%; BxPC-3 = 9%) with continued deterioration to 0%. Double heating to 45°C resulted in similar effects observed in single exposures, whereas repeated 48°C resulted in significant increases in cell death (PANC-1 = 68%; BxPC-3 = 29%). In conclusion, we observed that pancreatic cancer cells were completely destroyed at temperatures <-25°C or >50°C using single thermal exposures. Repeated exposures resulted in

Measurement of thermally ablated lesions in sonoelastographic images using level set methods

NASA Astrophysics Data System (ADS)

Castaneda, Benjamin; Tamez-Pena, Jose Gerardo; Zhang, Man; Hoyt, Kenneth; Bylund, Kevin; Christensen, Jared; Saad, Wael; Strang, John; Rubens, Deborah J.; Parker, Kevin J.

2008-03-01

The capability of sonoelastography to detect lesions based on elasticity contrast can be applied to monitor the creation of thermally ablated lesion. Currently, segmentation of lesions depicted in sonoelastographic images is performed manually which can be a time consuming process and prone to significant intra- and inter-observer variability. This work presents a semi-automated segmentation algorithm for sonoelastographic data. The user starts by planting a seed in the perceived center of the lesion. Fast marching methods use this information to create an initial estimate of the lesion. Subsequently, level set methods refine its final shape by attaching the segmented contour to edges in the image while maintaining smoothness. The algorithm is applied to in vivo sonoelastographic images from twenty five thermal ablated lesions created in porcine livers. The estimated area is compared to results from manual segmentation and gross pathology images. Results show that the algorithm outperforms manual segmentation in accuracy, inter- and intra-observer variability. The processing time per image is significantly reduced.

Characterization and initial field test of a long wave thermal infrared hyperspectral imager for measuring SO2 in volcanic plumes

NASA Astrophysics Data System (ADS)

Gabrieli, A.; Wright, R.; Porter, J. N.; Lucey, P. G.; Crites, S.; Garbeil, H.; Pilger, E. J.; Wood, M.

2015-12-01

The ability to quantify volcanic SO2 and image the spatial distribution in plumes either by day or by night would be beneficial to volcanologists. In this project, a newly developed remote sensing long-wave thermal infrared imaging hyperspectral sensor, was tested. The system employs a Sagnac interferometer and an uncooled microbolometer in rapid scanning configuration. This instrument is able to collect hyperspectral images of the scene between 8 and 14 and for each pixel a spectrum containing 50 samples can be retrieved. Images are spectrally and radiometrically calibrated using an IR source with a narrow band filter and two black bodies. The sensitivity of the system was studied by using a gas cell containing various known concentrations of SO2, which are representative of those found in volcanic plumes. Measured spectra were compared with theoretical spectra obtained from MODTRAN5 with the same viewing geometry and spectral resolution as the sensor. The MODTRAN5 calculations were carried out using a radiative transfer algorithm which accounts for the transmission and emission both inside and outside of the gas cell. These preliminary results and field measurements at Kīlauea volcano, Hawai'i will be discussed demonstrating the performance of the system and the ability of retrieving SO2 plume concentrations.

Spallation modeling in the Charring Material Thermal Response and Ablation (CMA) computer program

NASA Astrophysics Data System (ADS)

Sullivan, J. M.; Kobayashi, W. S.

1987-06-01

It has been observed during tests of certain laminated composite materials exposed to relatively high continuous wave laser irradiation, that the heated surface will spall. To model this phenomenon, the Charring Material Thermal Response and Ablation code has been updated. In addition to temperature response, in-depth decomposition, and surface recession, thermal and mechanical stresses are calculated. Spall is modeled as a discrete mass removal event occurring when the stresses exceed the ultimate strength of the char through a critical depth. Comparisons are made with test data for a carbon phenolic cylinder exposed to a shock tube environment and for a flat plate Kevlar epoxy test specimen exposed to high intensity laser irradiation. Good agreement is shown; however, the results indicate a requirement for more comprehensive elevated-temperature material properties for further validation.

Development and Verification of the Charring, Ablating Thermal Protection Implicit System Simulator

NASA Technical Reports Server (NTRS)

Amar, Adam J.; Calvert, Nathan; Kirk, Benjamin S.

2011-01-01

The development and verification of the Charring Ablating Thermal Protection Implicit System Solver (CATPISS) is presented. This work concentrates on the derivation and verification of the stationary grid terms in the equations that govern three-dimensional heat and mass transfer for charring thermal protection systems including pyrolysis gas flow through the porous char layer. The governing equations are discretized according to the Galerkin finite element method (FEM) with first and second order fully implicit time integrators. The governing equations are fully coupled and are solved in parallel via Newton s method, while the linear system is solved via the Generalized Minimum Residual method (GMRES). Verification results from exact solutions and Method of Manufactured Solutions (MMS) are presented to show spatial and temporal orders of accuracy as well as nonlinear convergence rates.

Development and Verification of the Charring Ablating Thermal Protection Implicit System Solver

NASA Technical Reports Server (NTRS)

Amar, Adam J.; Calvert, Nathan D.; Kirk, Benjamin S.

2010-01-01

The development and verification of the Charring Ablating Thermal Protection Implicit System Solver is presented. This work concentrates on the derivation and verification of the stationary grid terms in the equations that govern three-dimensional heat and mass transfer for charring thermal protection systems including pyrolysis gas flow through the porous char layer. The governing equations are discretized according to the Galerkin finite element method with first and second order implicit time integrators. The governing equations are fully coupled and are solved in parallel via Newton's method, while the fully implicit linear system is solved with the Generalized Minimal Residual method. Verification results from exact solutions and the Method of Manufactured Solutions are presented to show spatial and temporal orders of accuracy as well as nonlinear convergence rates.

Radio-physical properties of radiotransparent thermal protection materials in ablation mode

NASA Astrophysics Data System (ADS)

Petrovskiy, V. P.; Pakhomov, E. P.; Politiko, A. A.; Semenenko, V. N.; Chistyaev, V. A.; Balakirev, B. A.; Pervov, A. Yu; Kamalov, A. D.; Sotskova, L. P.

2018-01-01

Experimental method for assessing the impact of the effects of high-temperature ablation processes on the radio physical characteristics of radiotransparent thermal protection materials (RTPM) is developed. Researches for the following RTPM with various structures of glass fillers are completed: press material (radiotransparent thermal protection press material or RTP-200); glass-fiber laminate (glass-fiber radiotransparent organic ceramic matrix or GFR-CM); reinforced composite material of class SiO2-SiO2 (high-temperature radiotransparent ceramic organic matrix or HTRC-OM). The influence of physicochemical transformations in the surface layer of RTPM on transmission and reflection coefficients of electromagnetic waves of RTPM samples and on the value of their complex permittivity is determined.

Enhanced Thermal Ablation by Combining Ultrasound Contrast Agents with a Miniature Flat Transducer

NASA Astrophysics Data System (ADS)

Murillo, A.; Goldendstedt, C.; Lafon, C.; Cathignol, D.; Chapelon, J.-Y.

2007-05-01

Miniature transducers can be used for performing interstitial thermal ablation. Increasing the frequency of non-focused transducers enhances energy deposition but limits the therapeutic range. In order to treat extended tumors, new therapeutic strategies must be explored. This work aimed to combine ultrasound contrast agents (UCA) with flat transducers for increasing the treatment depth. The idea consists in increasing attenuation away from the transducer to favor remote heat deposition. Thermal ablation is induced in three steps. 1- Attenuation raises by injecting UCA; 2- Destruction of bubbles next to the transducer by pulsed high intensity bursts, results in a gradient of attenuation; 3- Continuous ultrasound are applied for generating a localized thermal lesion. In vitro tests were performed on temperature-sensitive tissue phantoms in which the UCA BR14 (Bracco) was injected during the liquid phase. The feasibility of the idea was demonstrated in three stages. 1- The coefficient of attenuation was measured with the force balance as a function of the concentration of BR14. For 0.8 and 4.8% attenuation at 10MHz was found to be 0.35 and 1.33 Np/cm respectively. 2- Pulsed ultrasound was applied on phantoms to destroy UCA. Based on the echogenicity decay evidenced on ultrasound images, a 1MPa-pressure was required at 10MHz. 3- Heating beams were applied on phantoms presenting a gradient in attenuation. Lesions were 1.5 times larger than in phantoms with constant attenuation. This study demonstrates that UCA can be selectively destroyed in order to generate a gradient of attenuation and extended thermal lesions.

An Update to a Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions

NASA Technical Reports Server (NTRS)

Beck, R.; Arnold, J.; Gasch, M.; Stackpoole, M.; Venkatapathy, E.

2014-01-01

As described at IPPW-10, in FY12, the CA-TPS element focused on establishing materials requirements based on MSL-type and COTS Low Earth orbit (LEO) conditions (q 250 Wcm2) to develop and deliver a conformal ablative TPS. This involved down selecting, manufacturing and testing two of the best candidate materials, demonstrating uniform infiltration of resins into baseline 2-cm thick carbon felt, selecting a primary conformal material formulation based on novel arc jet and basic material properties testing, developing and demonstrating instrumentation for felt-based materials and, based on the data, developing a low fidelity material response model so that the conformal ablator TPS thickness for missions could be established. In addition, the project began to develop Industry Partnerships. Since the nominal thickness of baseline carbon felts was only 2-cm, a partnership with a rayon felt developer was made in order to upgrade equipment, establish the processes required and attempt to manufacture 10-cm thick white goods. A partnership with a processing house was made to develop the methodology to carbonize large pieces of the white goods into 7.5-cm thick carbon felt. In FY13, more advanced testing and modeling of the down selected conformal material was performed. Material thermal properties tests and structural properties tests were performed. The first 3 and 4-point bend tests were performed on the conformal ablator as well as PICA for comparison and the conformal ablator had outstanding behavior compared to PICA. Arc jet testing was performed with instrumented samples of both the conformal ablator and standard PICA at heating rates ranging from 40 to 400 Wcm2 and shear as high as 600 Pa. The results from these tests showed a remarkable improvement in the thermal penetration through the conformal ablator when compared to PICAs response. The data from these tests were used to develop a mid-fidelity thermal response model. Additional arc jet testing in the same

Thermal fixation of swine liver tissue after magnetic resonance-guided high-intensity focused ultrasound ablation.

PubMed

Courivaud, Frédéric; Kazaryan, Airazat M; Lund, Alice; Orszagh, Vivian C; Svindland, Aud; Marangos, Irina Pavlik; Halvorsen, Per Steinar; Jebsen, Peter; Fosse, Erik; Hol, Per Kristian; Edwin, Bjørn

2014-07-01

The aim of this study was to investigate experimental conditions for efficient and controlled in vivo liver tissue ablation by magnetic resonance (MR)-guided high-intensity focused ultrasound (HIFU) in a swine model, with the ultimate goal of improving clinical treatment outcome. Histological changes were examined both acutely (four animals) and 1 wk after treatment (five animals). Effects of acoustic power and multiple sonication cycles were investigated. There was good correlation between target size and observed ablation size by thermal dose calculation, post-procedural MR imaging and histopathology, when temperature at the focal point was kept below 90°C. Structural histopathology investigations revealed tissue thermal fixation in ablated regions. In the presence of cavitation, mechanical tissue destruction occurred, resulting in an ablation larger than the target. Complete extra-corporeal MR-guided HIFU ablation in the liver is feasible using high acoustic power. Nearby large vessels were preserved, which makes MR-guided HIFU promising for the ablation of liver tumors adjacent to large veins. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Percutaneous thermal ablation for stage IA non-small cell lung cancer: long-term follow-up.

PubMed

Narsule, Chaitan K; Sridhar, Praveen; Nair, Divya; Gupta, Avneesh; Oommen, Roy G; Ebright, Michael I; Litle, Virginia R; Fernando, Hiran C

2017-10-01

Surgical resection is the most effective curative therapy for non-small cell lung cancer (NSCLC). However, many patients are unable to tolerate resection secondary to poor reserve or comorbid disease. Radiofrequency ablation (RFA) and microwave ablation (MWA) are methods of percutaneous thermal ablation that can be used to treat medically inoperable patients with NSCLC. We present long-term outcomes following thermal ablation of stage IA NSCLC from a single center. Patients with stage IA NSCLC and factors precluding resection who underwent RFA or MWA from July 2005 to September 2009 were studied. CT and PET-CT scans were performed at 3 and 6 month intervals, respectively, for first 24 months of follow-up. Factors associated with local progression (LP) and overall survival (OS) were analyzed. Twenty-one patients underwent 21 RFA and 4 MWA for a total of 25 ablations. Fifteen patients had T1a and six patients had T1b tumors. Mean follow-up was 42 months, median survival was 39 months, and OS at three years was 52%. There was no significant difference in median survival between T1a nodules and T1b nodules (36 vs . 39 months, P=0.29) or for RFA and MWA (36 vs . 50 months, P=0.80). Ten patients had LP (47.6%), at a median time of 35 months. There was no significant difference in LP between T1a and T1b tumors (22 vs . 35 months, P=0.94) or RFA and MWA (35 vs . 17 months, P=0.18). Median OS with LP was 32 months compared to 39 months without LP (P=0.68). Three patients underwent repeat ablations. Mean time to LP following repeat ablation was 14.75 months. One patient had two repeat ablations and was disease free at 40-month follow-up. Thermal ablation effectively treated or controlled stage IA NSCLC in medically inoperable patients. Three-year OS exceeded 50%, and LP did not affect OS. Therefore, thermal ablation is a viable option for medically inoperable patients with early stage NSCLC.

Detection of thermal gradients through fiber-optic Chirped Fiber Bragg Grating (CFBG): Medical thermal ablation scenario

NASA Astrophysics Data System (ADS)

Korganbayev, Sanzhar; Orazayev, Yerzhan; Sovetov, Sultan; Bazyl, Ali; Schena, Emiliano; Massaroni, Carlo; Gassino, Riccardo; Vallan, Alberto; Perrone, Guido; Saccomandi, Paola; Arturo Caponero, Michele; Palumbo, Giovanna; Campopiano, Stefania; Iadicicco, Agostino; Tosi, Daniele

2018-03-01

In this paper, we describe a novel method for spatially distributed temperature measurement with Chirped Fiber Bragg Grating (CFBG) fiber-optic sensors. The proposed method determines the thermal profile in the CFBG region from demodulation of the CFBG optical spectrum. The method is based on an iterative optimization that aims at minimizing the mismatch between the measured CFBG spectrum and a CFBG model based on coupled-mode theory (CMT), perturbed by a temperature gradient. In the demodulation part, we simulate different temperature distribution patterns with Monte-Carlo approach on simulated CFBG spectra. Afterwards, we obtain cost function that minimizes difference between measured and simulated spectra, and results in final temperature profile. Experiments and simulations have been carried out first with a linear gradient, demonstrating a correct operation (error 2.9 °C); then, a setup has been arranged to measure the temperature pattern on a 5-cm long section exposed to medical laser thermal ablation. Overall, the proposed method can operate as a real-time detection technique for thermal gradients over 1.5-5 cm regions, and turns as a key asset for the estimation of thermal gradients at the micro-scale in biomedical applications.

Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation.

PubMed

Guntur, Sitaramanjaneya Reddy; Lee, Kang Il; Paeng, Dong-Guk; Coleman, Andrew John; Choi, Min Joo

2013-10-01

Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing

Radiofrequency Thermal Ablation: Increase in Lesion Diameter with Continuous Acetic Acid Infusion

SciTech Connect

Lubienski, Andreas; Duex, Markus; Lubienski, Katrin

Purpose. To evaluate the influence of continuous infusion of acetic acid 50% during radiofrequency ablation (RFA) on the size of the thermal lesion produced. Methods. Radiofrequency (RF) was applied to excised bovine liver by using an expandable needle electrode with 10 retractable tines (LeVeen Needle Electrode, RadioTherapeutics, Sunnyvale, CA) connected to a commercially available RF generator (RF 2000, RadioTherapeutics, Sunnyvale, CA). Experiments were performed using three different treatment modalities: RF only (n = 15), RF with continuous saline 0.9% infusion (n = 15), and RF with continuous acetic acid 50% infusion (n = 15). RF duration, power output, tissue impedance,more » and time to a rapid rise in impedance were recorded. The ablated lesions were evaluated both macroscopically and histologically. Results. The ablated lesions appeared as spherical or ellipsoid, well-demarcated pale areas with a surrounding brown rim with both RF only and RF plus saline 0.9% infusion. In contrast, thermolesions generated with RF in combination with acetic acid 50% infusion were irregular in shape and the central portion was jelly-like. Mean diameter of the coagulation necrosis was 22.3 {+-} 2.1 mm (RF only), 29.2 {+-} 4.8 mm (RF + saline 0.9%) and 30.7 {+-} 5.7 mm (RF + acetic acid 50%), with a significant increase in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone. Time to a rapid rise in impedance was significantly prolonged in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone. Conclusions. A combination of RF plus acetic acid 50% infusion is able to generate larger thermolesions than RF only or RF combined with saline 0.9% infusion.« less

FAST SIMULATION OF SOLID TUMORS THERMAL ABLATION TREATMENTS WITH A 3D REACTION DIFFUSION MODEL *

PubMed Central

BERTACCINI, DANIELE; CALVETTI, DANIELA

2007-01-01

An efficient computational method for near real-time simulation of thermal ablation of tumors via radio frequencies is proposed. Model simulations of the temperature field in a 3D portion of tissue containing the tumoral mass for different patterns of source heating can be used to design the ablation procedure. The availability of a very efficient computational scheme makes it possible update the predicted outcome of the procedure in real time. In the algorithms proposed here a discretization in space of the governing equations is followed by an adaptive time integration based on implicit multistep formulas. A modification of the ode15s MATLAB function which uses Krylov space iterative methods for the solution of for the linear systems arising at each integration step makes it possible to perform the simulations on standard desktop for much finer grids than using the built-in ode15s. The proposed algorithm can be applied to a wide class of nonlinear parabolic differential equations. PMID:17173888

Evaluation of thermal infrared hyperspectral imagery for the detection of onshore methane plumes: Significance for hydrocarbon exploration and monitoring

NASA Astrophysics Data System (ADS)

Scafutto, Rebecca DeĺPapa Moreira; de Souza Filho, Carlos Roberto; Riley, Dean N.; de Oliveira, Wilson Jose

2018-02-01

Methane (CH4) is the main constituent of natural gas. Fugitive CH4 emissions partially stem from geological reservoirs (seepages) and leaks in pipelines and petroleum production plants. Airborne hyperspectral sensors with enough spectral and spatial resolution and high signal-to-noise ratio can potentially detect these emissions. Here, a field experiment performed with controlled release CH4 sources was conducted in the Rocky Mountain Oilfield Testing Center (RMOTC), Casper, WY (USA). These sources were configured to deliver diverse emission types (surface and subsurface) and rates (20-1450 scf/hr), simulating natural (seepages) and anthropogenic (pipeline) CH4 leaks. The Aerospace Corporation's SEBASS (Spatially-Enhanced Broadband Array Spectrograph System) sensor acquired hyperspectral thermal infrared data over the experimental site with 128 bands spanning the 7.6 μm-13.5 μm range. The data was acquired with a spatial resolution of 0.5 m at 1500 ft and 0.84 m at 2500 ft above ground level. Radiance images were pre-processed with an adaptation of the In-Scene Atmospheric Compensation algorithm and converted to emissivity through the Emissivity Normalization algorithm. The data was processed with a Matched Filter. Results allowed the separation between endmembers related to the spectral signature of CH4 from the background. Pixels containing CH4 signatures (absorption bands at 7.69 μm and 7.88 μm) were highlighted and the gas plumes mapped with high definition in the imagery. The dispersion of the mapped plumes is consistent with the wind direction measured independently during the experiment. Variations in the dimension of mapped gas plumes were proportional to the emission rate of each CH4 source. Spectral analysis of the signatures within the plumes shows that CH4 spectral absorption features are sharper and deeper in pixels located near the emitting source, revealing regions with higher gas density and assisting in locating CH4 sources in the field

Thermal Ablation of the Pancreas With Intraoperative High-Intensity Focused Ultrasound: Safety and Efficacy in a Porcine Model.

PubMed

Dupré, Aurélien; Melodelima, David; Pflieger, Hannah; Chen, Yao; Vincenot, Jérémy; Kocot, Anthony; Langonnet, Stéphan; Rivoire, Michel

2017-02-01

New focal destruction technologies such as high-intensity focused ultrasound (HIFU) may improve the prognosis of pancreatic ductal adenocarcinoma. Our objectives were to demonstrate the safety and efficacy of intraoperative pancreatic HIFU ablation in a porcine model. In a porcine model (N = 12), a single HIFU ablation was performed in either the body or tail of the pancreas, distant to superior mesenteric vessels. All animals were sacrificed on the eighth day. The primary objective was to obtain an HIFU ablation measuring at least 1 cm without premature death. In total, 12 HIFU ablations were carried out. These ablations were performed within 160 seconds and on average measured 20 (15-27) × 16 (8-26) mm. The primary objective was fulfilled in all but 1 pig. There were no premature deaths or severe complications. High-intensity focused ultrasound treatment was associated with a transitory increase in amylase and lipase levels, and pseudocysts were observed in half of the pigs without being clinically apparent. All ablations were well delimited at both gross and histological examinations. Intraoperative thermal destruction of porcine pancreas with HIFU is feasible. Reproducibility and safety have to be confirmed when applied close to mesenteric vessels and in long-term preclinical studies.

A 915-MHz antenna for microwave thermal ablation treatment: physical design, computer modeling and experimental measurement.

PubMed

Pisa, S; Cavagnaro, M; Bernardi, P; Lin, J C

2001-05-01

A 915-MHz antenna design that produces specific absorption rate distributions with preferential power deposition in tissues surrounding and including the distal end of the catheter antenna is described. The design features minimal reflected microwave current from the antenna flowing up the transmission line. This cap-choke antenna consists of an annular cap and a coaxial choke which matches the antenna to the coaxial transmission line. The design minimizes heating of the coaxial cable and its performance is not affected by the depth of insertion of the antenna into tissue. The paper provides a comparison of results obtained from computer modeling and experimental measurements made in tissue equivalent phantom materials. There is excellent agreement between numerical modeling and experimental measurement. The cap-choke, matched-dipole type antenna is suitable for intracavitary microwave thermal ablation therapy.

Conformal Ablative Thermal Protection Systems (CA-TPS) for Venus and Saturn Backshells

NASA Technical Reports Server (NTRS)

Beck, R.; Gasch, M.; Stackpoole, M.; Wilder, M.; Boghozian, T.; Chavez-Garcia, J.; Prabhu, D.; Kazemba, C.; Venkatapathy, E.

2015-01-01

The new conformal ablator C-PICA, which was developed under STMD GCD, is an optimal candidate for use on the backshells for high velocity entry vehicles at both Venus and Saturn. The material has been tested at heat fluxes up to 400 Wcm2 in shear and over 1800 Wcm2 and 1.5 atm in stagnation with good results. C-PICA has similar density to PICA, but shows half the thermal penetration and similar recession at the same conditions, allowing for a lighter weight TPS to be flown. This poster for VEXAG will show the progress made in the development of the material and why it should be considered for use.

Thermal ablation of pancreatic cyst with a prototype endoscopic ultrasound capable radiofrequency needle device: A pilot feasibility study

PubMed Central

Moris, Maria; Atar, Mustafa; Kadayifci, Abdurrahman; Krishna, Murli; Librero, Ariston; Richie, Eugene; Brugge, William; Wallace, Michael B.

2017-01-01

Background and Objectives: Pancreatic cysts are evaluated by endoscopic ultrasound and fine needle aspiration (EUS). The only accepted treatment is pancreatectomy, which is associated with morbidity and mortality. This study evaluated the optimal thermal dosimetry of a novel radiofrequency ablation device using a standard electrosurgical unit in ex vivo cyst models. Methods: A modified EUS 22-gauge monopolar needle prototype with a tip electrode connected to a standard electrosurgical unit (Erbe USA, Marietta, GA, USA) was used to induce a subboiling point temperature. A cyst model was created using 2-cm sections of porcine small intestine ligated and filled with saline. After ablation, the cyst models were prepared for pathological evaluation. The epithelial layers were measured in at least two different sites with a micrometer and compared with the corresponding control sample. Results: Thirty-two cyst models were ablated with maximum temperatures of 50°C, 60°C, 90°C, and 97°C in 8, 11, 11, and 2 cysts, respectively. Longer ablation times were required to induce higher temperatures. A trend in the reduction in thickness of the measured layers was observed after exposure to higher temperatures. A temperature over 50°C was required for the ablation of the muscularis, submucosa, and villi, and over 60°C was required to ablate the mucosal crypts. Conclusions: In a preclinical model, a novel radiofrequency EUS-capable needle connected to a standard electrosurgical unit using standard low-voltage coagulation provided ablation in a temperature-dependent fashion with a threshold of at least 60°C and a safe cyst margin below 97°C. This potentially will allow low-cost, convenient cyst ablation. PMID:28440238

[Monitoring the thermal plume from coastal nuclear power plant using satellite remote sensing data: modeling, and validation].

PubMed

Zhu, Li; Zhao, Li-Min; Wang, Qiao; Zhang, Ai-Ling; Wu, Chuan-Qing; Li, Jia-Guo; Shi, Ji-Xiang

2014-11-01

Thermal plume from coastal nuclear power plant is a small-scale human activity, mornitoring of which requires high-frequency and high-spatial remote sensing data. The infrared scanner (IRS), on board of HJ-1B, has an infrared channel IRS4 with 300 m and 4-days as its spatial and temporal resolution. Remote sensing data aquired using IRS4 is an available source for mornitoring thermal plume. Retrieval pattern for coastal sea surface temperature (SST) was built to monitor the thermal plume from nuclear power plant. The research area is located near Guangdong Daya Bay Nuclear Power Station (GNPS), where synchronized validations were also implemented. The National Centers for Environmental Prediction (NCEP) data was interpolated spatially and temporally. The interpolated data as well as surface weather conditions were subsequently employed into radiative transfer model for the atmospheric correction of IRS4 thermal image. A look-up-table (LUT) was built for the inversion between IRS4 channel radiance and radiometric temperature, and a fitted function was also built from the LUT data for the same purpose. The SST was finally retrieved based on those preprocessing procedures mentioned above. The bulk temperature (BT) of 84 samples distributed near GNPS was shipboard collected synchronically using salinity-temperature-deepness (CTD) instruments. The discrete sample data was surface interpolated and compared with the satellite retrieved SST. Results show that the average BT over the study area is 0.47 degrees C higher than the retrieved skin temperature (ST). For areas far away from outfall, the ST is higher than BT, with differences less than 1.0 degrees C. The main driving force for temperature variations in these regions is solar radiation. For areas near outfall, on the contrary, the retrieved ST is lower than BT, and greater differences between the two (meaning > 1.0 degrees C) happen when it gets closer to the outfall. Unlike the former case, the convective heat

Non-linear dual-phase-lag model for analyzing heat transfer phenomena in living tissues during thermal ablation.

PubMed

Kumar, P; Kumar, Dinesh; Rai, K N

2016-08-01

In this article, a non-linear dual-phase-lag (DPL) bio-heat transfer model based on temperature dependent metabolic heat generation rate is derived to analyze the heat transfer phenomena in living tissues during thermal ablation treatment. The numerical solution of the present non-linear problem has been done by finite element Runge-Kutta (4,5) method which combines the essence of Runge-Kutta (4,5) method together with finite difference scheme. Our study demonstrates that at the thermal ablation position temperature predicted by non-linear and linear DPL models show significant differences. A comparison has been made among non-linear DPL, thermal wave and Pennes model and it has been found that non-linear DPL and thermal wave bio-heat model show almost same nature whereas non-linear Pennes model shows significantly different temperature profile at the initial stage of thermal ablation treatment. The effect of Fourier number and Vernotte number (relaxation Fourier number) on temperature profile in presence and absence of externally applied heat source has been studied in detail and it has been observed that the presence of externally applied heat source term highly affects the efficiency of thermal treatment method. Copyright © 2016 Elsevier Ltd. All rights reserved.

Changes in the dielectric properties of ex vivo bovine liver during microwave thermal ablation at 2.45 GHz

NASA Astrophysics Data System (ADS)

Lopresto, Vanni; Pinto, Rosanna; Lovisolo, Giorgio A.; Cavagnaro, Marta

2012-04-01

In microwave thermal ablation (MTA) therapy, the dielectric properties of the target tissue play an important role in determining the radiation properties of the microwave ablation antenna. In this work, the ex vivo dielectric properties of bovine liver were experimentally characterized as a function of the temperature during MTA at the frequency of 2.45 GHz. The obtained data were compared with measurements performed at the end of the MTA treatment, and considering the heating achieved with a temperature-controlled water bath. Finally, measured data were used to perform a numerical study evaluating the effects of changes in tissue's dielectric properties during the MTA treatment on the radiation properties of a microwave interstitial ablation antenna, as well as on the obtained thermal lesion. Results evidenced a significant decrease of both relative permittivity (about 38%) and electric conductivity (about 33%) in the tissue during treatment as the temperature increased to over 60 °C, with a dramatic drop when the temperature approached 100 °C. Moreover, the numerical study evidenced that changes in tissue's dielectric properties during the MTA treatment affect the distribution of the power absorbed by the tissue (specific absorption rate—SAR, W kg-1) surrounding the microwave interstitial ablation antenna, leading to a peak SAR up to 20% lower, as well as to a thermal lesion up to 8% longer. This work may represent a preliminary step towards the future development of a procedure for MTA treatment planning.

Gd-EOB-DTPA-Enhanced MR Guidance in Thermal Ablation of Liver Malignancies

PubMed Central

Rosenberg, Christian; Jahn, Andrea; Pickartz, Tilman; Wahnschaffe, Ulrich; Patrzyk, Maciej; Hosten, Norbert

2014-01-01

Objective To evaluate the potency of Gd-EOB-DTPA to support hepatic catheter placement in laser ablation procedures by quantifying time-dependent delineation effects for instrumentation and target tumor within liver parenchyma. Monitoring potential influence on online MR thermometry during the ablation procedure is a secondary aim. Materials and Methods 30 cases of MR-guided laser ablation were performed after i.v. bolus injection of gadoxetic acid (0.025 mmol/Kg Gd-EOB-DTPA; Bayer Healthcare, Berlin, Germany). T1-weighted GRE sequences were used for applicator guidance (FLASH 3D) in the catheter placement phase and for therapy monitoring (FLASH 2D) in the therapy phase. SNR and consecutive CNR values were measured for elements of interest plotted over time both for catheter placement and therapy phase and compared with a non-contrast control group of 19 earlier cases. Statistical analysis was realized using the paired Wilcoxon test. Results Sustainable signal elevation of liver parenchyma in the contrast-enhanced group was sufficient to silhouette both target tumor and applicator against the liver. Differences in time dependent CNR alteration were highly significant between contrast-enhanced and non-contrast interventions for parenchyma and target on the one hand (p = 0.020) and parenchyma and instrument on the other hand (p = 0.002). Effects lasted for the whole procedure (monitoring up to 60 min) and were specific for the contrast-enhanced group. Contrasting maxima were seen after median 30 (applicator) and 38 (tumor) minutes, in the potential core time of a multineedle procedure. Contrast influence on T1 thermometry for real-time monitoring of thermal impact was not significant (p = 0.068–0.715). Conclusion Results strongly support anticipated promotive effects of Gd-EOB-DTPA for MR-guided percutaneous liver interventions by proving and quantifying the delineating effects for therapy-relevant elements in the procedure. Time benefit, cost

Gd-EOB-DTPA-enhanced MR guidance in thermal ablation of liver malignancies.

PubMed

Rosenberg, Christian; Jahn, Andrea; Pickartz, Tilman; Wahnschaffe, Ulrich; Patrzyk, Maciej; Hosten, Norbert

2014-01-01

To evaluate the potency of Gd-EOB-DTPA to support hepatic catheter placement in laser ablation procedures by quantifying time-dependent delineation effects for instrumentation and target tumor within liver parenchyma. Monitoring potential influence on online MR thermometry during the ablation procedure is a secondary aim. 30 cases of MR-guided laser ablation were performed after i.v. bolus injection of gadoxetic acid (0.025 mmol/Kg Gd-EOB-DTPA; Bayer Healthcare, Berlin, Germany). T1-weighted GRE sequences were used for applicator guidance (FLASH 3D) in the catheter placement phase and for therapy monitoring (FLASH 2D) in the therapy phase. SNR and consecutive CNR values were measured for elements of interest plotted over time both for catheter placement and therapy phase and compared with a non-contrast control group of 19 earlier cases. Statistical analysis was realized using the paired Wilcoxon test. Sustainable signal elevation of liver parenchyma in the contrast-enhanced group was sufficient to silhouette both target tumor and applicator against the liver. Differences in time dependent CNR alteration were highly significant between contrast-enhanced and non-contrast interventions for parenchyma and target on the one hand (p = 0.020) and parenchyma and instrument on the other hand (p = 0.002). Effects lasted for the whole procedure (monitoring up to 60 min) and were specific for the contrast-enhanced group. Contrasting maxima were seen after median 30 (applicator) and 38 (tumor) minutes, in the potential core time of a multineedle procedure. Contrast influence on T1 thermometry for real-time monitoring of thermal impact was not significant (p = 0.068-0.715). Results strongly support anticipated promotive effects of Gd-EOB-DTPA for MR-guided percutaneous liver interventions by proving and quantifying the delineating effects for therapy-relevant elements in the procedure. Time benefit, cost effectiveness and oncologic outcome of the described beneficiary effects

Bronchoscopic Thermal Vapor Ablation: Best Practice Recommendations from an Expert Panel on Endoscopic Lung Volume Reduction.

PubMed

Gompelmann, Daniela; Shah, Pallav L; Valipour, Arschang; Herth, Felix J F

2018-06-12

Bronchoscopic thermal vapor ablation (BTVA) represents one of the endoscopic lung volume reduction (ELVR) techniques that aims at hyperinflation reduction in patients with advanced emphysema to improve respiratory mechanics. By targeted segmental vapor ablation, an inflammatory response leads to tissue and volume reduction of the most diseased emphysematous segments. So far, BTVA has been demonstrated in several single-arm trials and 1 multinational randomized controlled trial to improve lung function, exercise capacity, and quality of life in patients with upper lobe-predominant emphysema irrespective of the collateral ventilation. In this review, we emphasize the practical aspects of this ELVR method. Patients with upper lobe-predominant emphysema, forced expiratory volume in 1 second (FEV1) between 20 and 45% of predicted, residual volume (RV) > 175% of predicted, and carbon monoxide diffusing capacity (DLCO) ≥20% of predicted can be considered for BTVA treatment. Prior to the procedure, a special software assists in identifying the target segments with the highest emphysema index, volume and the highest heterogeneity index to the untreated ipsilateral lung lobes. The procedure may be performed under deep sedation or preferably under general anesthesia. After positioning of the BTVA catheter and occlusion of the target segment by the occlusion balloon, heated water vapor is delivered in a predetermined specified time according to the vapor dose. After the procedure, patients should be strictly monitored to proactively detect symptoms of localized inflammatory reaction that may temporarily worsen the clinical status of the patient and to detect complications. As the data are still very limited, BTVA should be performed within clinical trials or comprehensive registries where the product is commercially available. © 2018 S. Karger AG, Basel.

Thermal Shock and Ablation Behavior of Tungsten Nozzle Produced by Plasma Spray Forming and Hot Isostatic Pressing

NASA Astrophysics Data System (ADS)

Wang, Y. M.; Xiong, X.; Zhao, Z. W.; Xie, L.; Min, X. B.; Yan, J. H.; Xia, G. M.; Zheng, F.

2015-08-01

Tungsten nozzle was produced by plasma spray forming (PSF, relative density of 86 ± 2%) followed by hot isostatic pressing (HIPing, 97 ± 2%) at 2000 °C and 180 MPa for 180 min. Scanning electron microscope, x-ray diffractometer, Archimedes method, Vickers hardness, and tensile tests have been employed to study microstructure, phase composition, density, micro-hardness, and mechanical properties of the parts. Resistance of thermal shock and ablation behavior of W nozzle were investigated by hot-firing test on solid rocket motor (SRM). Comparing with PSF nozzle, less damage was observed for HIPed sample after SRM test. Linear ablation rate of nozzle made by PSF was (0.120 ± 0.048) mm/s, while that after HIPing reduced to (0.0075 ± 0.0025) mm/s. Three types of ablation mechanisms including mechanical erosion, thermophysical erosion, and thermochemical ablation took place during hot-firing test. The order of degree of ablation was nozzle throat > convergence > dilation inside W nozzle.

[Thermal balloon endometrial ablation for dysfunctional uterine bleeding: technical aspects and results. A prospective cohort study of 152 cases].

PubMed

Kdous, Moez; Jacob, Denis; Gervaise, Amélie; Risk, Elie; Sauvanet, Eric

2008-05-01

Thermal balloon endometrial ablation is a new operative technique recently proposed in the treatment of dysfunctional uterine bleeding. To evaluate the efficacy of thermal balloon endometrial ablation in the treatment of dysfunctional uterine bleeding, and to identify the possible predictive factors for a successful outcome. A prospective study was conducted including 152 patients with chronic abnormal uterine bleeding refractory to medical treatment. All patients were treated by thermal balloon endometrial ablation (Thermachoice, Gynecare) between January 1, 1996 and December 31, 2003. patients were included if their uterine cavities sounded to less than 12 cm and had undergone hysteroscopy, pelvic ultrasound and endometrial biopsie showing no structural or (pre) malignant endometrial abnormalities. A balloon catheter was placed through the cervix and after inflation in the endometrial cavity with 5% dextrose in water, was heated to 87 +/- 5 degrees C. No one required cervical dilatation. Balloon pressures were 160 to 170 mm Hg. All patients underwent 8 minutes of therapy. The average patient was 47 years (range: 30-62 years) and was followed for a mean of 3 years and 7 months (range: 6 months - 8 years). 31.6% of women reported amennorhea, 16.5% hypomenorrhea and 21% eumenorrhea. Menorrhagea persisted in 11.2% of patients. No intraoperative complications and minor postoperative morbidity occured in 10.5% of patients. Three prgnancy complicated by spontaneous abortions were reported after the treatment. A total of 78% of women reported overall satisfaction with the endometrial ablation procedure and 18% were dissatisfied. 17.8% of patients underwent hysterectomy within 1 to 5 years of balloon endometrial ablation. Increasing age and menopause were significantly associated with increased odds of success (p < 0.05). Thermal balloon endometrial ablation is a simple, easy, effective, and minimally invasive procedure in menhorragic women with no desire for further

Subcellular analysis by laser ablation electrospray ionization mass spectrometry

DOEpatents

Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

2014-12-02

In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

Speed of sound estimation for thermal monitoring using an active ultrasound element during liver ablation therapy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kim, Younsu; Audigier, Chloé; Dillow, Austin; Cheng, Alexis; Boctor, Emad M.

2017-03-01

Thermal monitoring for ablation therapy has high demands for preserving healthy tissues while removing malignant ones completely. Various methods have been investigated. However, exposure to radiation, cost-effectiveness, and inconvenience hinder the use of X-ray or MRI methods. Due to the non-invasiveness and real-time capabilities of ultrasound, it is widely used in intraoperative procedures. Ultrasound thermal monitoring methods have been developed for affordable monitoring in real-time. We propose a new method for thermal monitoring using an ultrasound element. By inserting a Lead-zirconate-titanate (PZT) element to generate the ultrasound signal in the liver tissues, the single travel time of flight is recorded from the PZT element to the ultrasound transducer. We detect the speed of sound change caused by the increase in temperature during ablation therapy. We performed an ex vivo experiment with liver tissues to verify the feasibility of our speed of sound estimation technique. The time of flight information is used in an optimization method to recover the speed of sound maps during the ablation, which are then converted into temperature maps. The result shows that the trend of temperature changes matches with the temperature measured at a single point. The estimation error can be decreased by using a proper curve linking the speed of sound to the temperature. The average error over time was less than 3 degrees Celsius for a bovine liver. The speed of sound estimation using a single PZT element can be used for thermal monitoring.

Review of temperature dependence of thermal properties, dielectric properties, and perfusion of biological tissues at hyperthermic and ablation temperatures.

PubMed

Rossmanna, Christian; Haemmerich, Dieter

2014-01-01

The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes.

Review of temperature dependence of thermal properties, dielectric properties, and perfusion of biological tissues at hyperthermic and ablation temperatures

PubMed Central

Rossmann, Christian; Haemmerich, Dieter

2016-01-01

The application of supraphysiological temperatures (>40°C) to biological tissues causes changes at the molecular, cellular, and structural level, with corresponding changes in tissue function and in thermal, mechanical and dielectric tissue properties. This is particularly relevant for image-guided thermal treatments (e.g. hyperthermia and thermal ablation) delivering heat via focused ultrasound (FUS), radiofrequency (RF), microwave (MW), or laser energy; temperature induced changes in tissue properties are of relevance in relation to predicting tissue temperature profile, monitoring during treatment, and evaluation of treatment results. This paper presents a literature survey of temperature dependence of electrical (electrical conductivity, resistivity, permittivity) and thermal tissue properties (thermal conductivity, specific heat, diffusivity). Data of soft tissues (liver, prostate, muscle, kidney, uterus, collagen, myocardium and spleen) for temperatures between 5 to 90°C, and dielectric properties in the frequency range between 460 kHz and 3 GHz are reported. Furthermore, perfusion changes in tumors including carcinomas, sarcomas, rhabdomyosarcoma, adenocarcinoma and ependymoblastoma in response to hyperthmic temperatures up to 46°C are presented. Where appropriate, mathematical models to describe temperature dependence of properties are presented. The presented data is valuable for mathematical models that predict tissue temperature during thermal therapies (e.g. hyperthermia or thermal ablation), as well as for applications related to prediction and monitoring of temperature induced tissue changes. PMID:25955712

Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

NASA Astrophysics Data System (ADS)

Peña-Díaz, M.; Ponce, L.; Arronte, M.; Flores, T.

2007-04-01

Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

Thermal ablation of an aluminium film upon absorption of a femtosecond laser pulse

SciTech Connect

Bezhanov, S G; Kanavin, A P; Uryupin, S A

We have found the time dependence of the ablation depth of aluminium irradiated by a femtosecond laser pulse. It is shown to what extent an increase in the radiation energy flux density leads to an increase in the quasi-stationary value of the ablation depth. By reducing the aluminium film thickness down to one hundred nanometres and less, the ablation depth significantly increases. At the same time, the quasi-stationary value of the ablation depth of a thin film is obtained due to the removal of heat from the focal spot region. (interaction of laser radiation with matter. laser plasma)

Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions

NASA Technical Reports Server (NTRS)

Beck, R.; Arnold, J.; Gasch, M.; Stackpole, M.; Wercinski, R.; Venkatapathy, E.; Fan, W.; Thornton, J; Szalai, C.

2012-01-01

interest. The entry environment is not always guaranteed with a direct entry, and improving the entry systems robustness to a variety of environmental conditions could aid in reaching more varied landing sites. The National Research Council (NRC) Space Technology Roadmaps and Priorities report highlights six challenges and they are: 1) Mass to Surface, 2) Surface Access, 3) Precision Landing, 4) Surface Hazard Detection and Avoidance, 5) Safety and Mission Assurance, and 6) Affordability. In order for NASA to meet these challenges, the report recommends immediate focus on Rigid and Flexible Thermal Protection Systems. Rigid TPS systems such as Avcoat or SLA are honeycomb based and PICA is in the form of tiles. The honeycomb systems is manufactured using techniques that require filling of each (3/8 cell) by hand and within a limited amount of time once the ablative compound is mixed, all of the cells have to be filled and the entire heat-shield has to be cured. The tile systems such as PICA pose a different challenge as the mechanical strength characteristic and the manufacturing limitations require large number of small tiles with gap-fillers between the tiles. Recent investments in flexible ablative systems have given rise to the potential for conformal ablative TPS> A conformal TPS over a rigid aeroshell has the potential to solve a number of challenges faced by traditional rigid TPS materials.

Feasibility of Intraoperative Nerve Monitoring in Preventing Thermal Damage to the “Nerve at Risk” During Image-Guided Ablation of Tumors

SciTech Connect

Marshall, Richard H., E-mail: rmars1@lsuhsc.edu; Avila, Edward K., E-mail: avilae@mskcc.org; Solomon, Stephen B., E-mail: solomons@mskcc.org

PurposeTo assess feasibility of intraoperative neurophysiologic monitoring (IONM) during image-guided, percutaneous thermal ablation of tumors.Materials and MethodsFrom February 2009 to October 2013, a retrospective review of all image-guided percutaneous thermal ablation interventions using IONM was performed and data was compiled using electronic medical records and imaging studies.ResultsTwelve patients were treated in 13 ablation interventions. In 4 patients, real-time feedback from the monitoring neurologist was used to adjust applicator placement and ablation settings. IONM was technically feasible in all procedures and there were no complications related to monitoring or ablation. All nerves at risk remained intact and of the 11 patientsmore » who could be followed, none developed new nerve deficit up to a minimum of 2 months after ablation.ConclusionIONM is safe and feasible for use during image-guided thermal ablation of tumors in the vicinity of nerves. Outcomes in this study demonstrate its potential utility in image-guided ablation interventions.« less

Experiment on large scale plume interaction with a stratified gas environment resembling the thermal activity of a autocatalytic recombiner

SciTech Connect

Mignot, G.; Kapulla, R.; Paladino, D.

Computational Fluid Dynamics codes (CFD) are increasingly being used to simulate containment conditions after various transient accident scenarios. Consequently, the reliability of such codes must be tested against experimental data. Such validation experiments related to gas mixing and hydrogen transport within containment compartments addressing the effect of heat source are presented in this paper. The experiments were conducted in the large-scale thermal-hydraulics PANDA facility located at the Paul-Scherrer-Inst. (PSI) in Switzerland, in the frame of the OECD/SETH-2 project. A 10 kW electric heater simulating the thermal activity of the autocatalytic recombiner was activated at full power in a containment vesselmore » at the top of which a thick helium layer is initially present. The hot plume interacts with the bottom of the helium layer which is slowly eroded until complete break up at 1350 s. After final erosion of the layer a strong temperature and concentration gradient is maintained in the vessel below the heater inlet as well as in the adjacent vessel below the interconnecting pipe. A detailed characterization of the operating heater suggests the presence of cold gas ingress at the outlet that affects the flow in the chimney. This can be of concern if present in a real PAR unit. (authors)« less

Thermal Versus Impedance-Based Ablation of Renal Cell Carcinoma: A Meta-analysis

SciTech Connect

Modabber, Milad, E-mail: mmodabber@gmail.com; Martin, Jason, E-mail: jason.martin@medportal.ca; Athreya, Sriharsha, E-mail: sathreya@stjosham.on.ca

2013-10-04

BackgroundPercutaneous radiofrequency ablation (RFA) of renal carcinoma has become an established treatment modality. However, thermal (TB) versus impedance-based (IB)-RF generators have not been previously compared.MethodsA literature search on the application of RFA for renal masses using TB or IB-RF generators was performed. The safety, efficacy, and long-term outcomes of TB versus IB-based RFA were assessed using the outcome measures of technical success, local recurrence rate, complications, and preservation of renal function.ResultsAcross the 27 included studies, pooled results suggested comparable results for technical success (TB-RFA 98.53 % vs. IB-RFA 98.78 %, P = 0.9813). Clinical efficacy results were also similar across both generators (91.0 % TB-RFAmore » vs. 91.5 % IB-RFA; P = 0.73). At follow-up, no differences in renal function (relative risk [RR] 0.5, 95 % confidence interval [CI] 0.45–5.48), and local recurrence (RR 0.717, 95 % CI 0.49–1.50) were observed. The pooled proportion of overall complication rates was 13.1 % for TB-RFA and 11.5 % for IB-RFA.ConclusionNo differences in the observed parameters were found either during surgery or at follow-up.« less

The Feasibility of Using Thermal Strain Imaging to Regulate Energy Delivery During Intracardiac Radio-Frequency Ablation

PubMed Central

Seo, Chi Hyung; Stephens, Douglas N.; Cannata, Jonathan; Dentinger, Aaron; Lin, Feng; Park, Suhyun; Wildes, Douglas; Thomenius, Kai E.; Chen, Peter; Nguyen, Tho; de La Rama, Alan; Jeong, Jong Seob; Mahajan, Aman; Shivkumar, Kalyanam; Nikoozadeh, Amin; Oralkan, Omer; Truong, Uyen; Sahn, David J.; Khuri-Yakub, Pierre T.; O’Donnell, Matthew

2011-01-01

A method is introduced to monitor cardiac ablative therapy by examining slope changes in the thermal strain curve caused by speed of sound variations with temperature. The sound speed of water-bearing tissue such as cardiac muscle increases with temperature. However, at temperatures above about 50°C, there is no further increase in the sound speed and the temperature coefficient may become slightly negative. For ablation therapy, an irreversible injury to tissue and a complete heart block occurs in the range of 48 to 50°C for a short period in accordance with the well-known Arrhenius equation. Using these two properties, we propose a potential tool to detect the moment when tissue damage occurs by using the reduced slope in the thermal strain curve as a function of heating time. We have illustrated the feasibility of this method initially using porcine myocardium in vitro. The method was further demonstrated in vivo, using a specially equipped ablation tip and an 11-MHz microlinear intracardiac echocardiography (ICE) array mounted on the tip of a catheter. The thermal strain curves showed a plateau, strongly suggesting that the temperature reached at least 50°C. PMID:21768025

Comparison of Radiofrequency Thermal Ablation and Microdebrider-Assisted Turbinoplasty in Inferior Turbinate Hypertrophy: A Prospective, Randomized, and Clinical Study

PubMed Central

Akagün, Fatih; İmamoğlu, Mehmet; Çobanoğlu, Hatice Bengü; Ural, Ahmet

2016-01-01

Objective To compare the effectiveness of radiofrequency thermal ablation with those of microdebrider-assisted turbinoplasty, we designed a prospective, randomized clinical study. Methods Forty patients suffering from nasal obstruction due to bilateral inferior turbinate hypertrophy were enrolled. Half of the patients were operated by radiofrequency thermal ablation, while the other half underwent microdebrider-assisted turbinoplasty. The outcomes of both techniques were compared in terms of symptomatology, nasal patency, and mucociliary transport. Results A statistically significant difference existed between the two groups with respect to nasal obstruction and the frequency of obstruction at the first post-operative week and first and third post-operative months (p<0.05). Rhinomanometry detected a significant decrease in nasal resistance values in both surgical groups compared to the preoperative values. The mucociliary transport time was significantly prolonged in the first postoperative week and first postoperative month in microdebrider-assisted inferior turbinoplasty group. Conclusion Both radiofrequency thermal ablation and microdebrider-assisted turbinoplasty are effective techniques for treating inferior turbinate hypertrophy. The treatment modality should be individually determined, and parameters such as tissue healing, volume reduction, and mucociliary activity must be taken into account. PMID:29392030

Expanded modeling of temperature-dependent dielectric properties for microwave thermal ablation

PubMed Central

Ji, Zhen; Brace, Christopher L

2011-01-01

Microwaves are a promising source for thermal tumor ablation due to their ability to rapidly heat dispersive biological tissues, often to temperatures in excess of 100 °C. At these high temperatures, tissue dielectric properties change rapidly and, thus, so do the characteristics of energy delivery. Precise knowledge of how tissue dielectric properties change during microwave heating promises to facilitate more accurate simulation of device performance and helps optimize device geometry and energy delivery parameters. In this study, we measured the dielectric properties of liver tissue during high-temperature microwave heating. The resulting data were compiled into either a sigmoidal function of temperature or an integration of the time–temperature curve for both relative permittivity and effective conductivity. Coupled electromagnetic–thermal simulations of heating produced by a single monopole antenna using the new models were then compared to simulations with existing linear and static models, and experimental temperatures in liver tissue. The new sigmoidal temperature-dependent model more accurately predicted experimental temperatures when compared to temperature–time integrated or existing models. The mean percent differences between simulated and experimental temperatures over all times were 4.2% for sigmoidal, 10.1% for temperature–time integration, 27.0% for linear and 32.8% for static models at the antenna input power of 50 W. Correcting for tissue contraction improved agreement for powers up to 75 W. The sigmoidal model also predicted substantial changes in heating pattern due to dehydration. We can conclude from these studies that a sigmoidal model of tissue dielectric properties improves prediction of experimental results. More work is needed to refine and generalize this model. PMID:21791728

Sheet-like and plume-like thermal flow in a spherical convection experiment performed under microgravity

NASA Astrophysics Data System (ADS)

Breuer, D.; Futterer, B.; Plesa, A.; Krebs, A.; Zaussinger, F.; Egbers, C.

2013-12-01

In mantle dynamics research, experiments, usually performed in rectangular geometries in Earth-based laboratories, have the character of ';exploring new physics and testing theories' [1]. In this work, we introduce our spherical geometry experiments on electro-hydrodynamical driven Rayleigh-Benard convection that have been performed for both temperature-independent (`GeoFlow I'), and temperature-dependent fluid viscosity properties (`GeoFlow II') with a measured viscosity contrast up to 1.5. To set up a self-gravitating force field, we use a high voltage potential between the inner and outer boundaries and a dielectric insulating liquid and perform the experiment under microgravity conditions at the ISS [2, 3]. Further, numerical simulations in 3D spherical geometry have been used to reproduce the results obtained in the `GeoFlow' experiments. For flow visualisation, we use Wollaston prism shearing interferometry which is an optical method producing fringe pattern images. Flow pattern differ between our two experiments (Fig. 1). In `GeoFlow I', we see a sheet-like thermal flow. In this case convection patterns have been successfully reproduced by 3D numerical simulations using two different and independently developed codes. In contrast, in `GeoFlow II' we obtain plume-like structures. Interestingly, numerical simulations do not yield this type of solution for the low viscosity contrast realised in the experiment. However, using a viscosity contrast of two orders of magnitude or higher, we can reproduce the patterns obtained in the `GeoFlow II' experiment, from which we conclude that non-linear effects shift the effective viscosity ratio [4]. References [1] A. Davaille and A. Limare (2009). In: Schubert, G., Bercovici, D. (Eds.), Treatise on Geophysics - Mantle Dynamics. [2] B. Futterer, C. Egbers, N. Dahley, S. Koch, L. Jehring (2010). Acta Astronautica 66, 193-100. [3] B. Futterer, N. Dahley, S. Koch, N. Scurtu, C. Egbers (2012). Acta Astronautica 71, 11-19. [4

Feasibility of real-time MR thermal dose mapping for predicting radiofrequency ablation outcome in the myocardium in vivo.

PubMed

Toupin, Solenn; Bour, Pierre; Lepetit-Coiffé, Matthieu; Ozenne, Valéry; Denis de Senneville, Baudouin; Schneider, Rainer; Vaussy, Alexis; Chaumeil, Arnaud; Cochet, Hubert; Sacher, Frédéric; Jaïs, Pierre; Quesson, Bruno

2017-01-25

Clinical treatment of cardiac arrhythmia by radiofrequency ablation (RFA) currently lacks quantitative and precise visualization of lesion formation in the myocardium during the procedure. This study aims at evaluating thermal dose (TD) imaging obtained from real-time magnetic resonance (MR) thermometry on the heart as a relevant indicator of the thermal lesion extent. MR temperature mapping based on the Proton Resonance Frequency Shift (PRFS) method was performed at 1.5 T on the heart, with 4 to 5 slices acquired per heartbeat. Respiratory motion was compensated using navigator-based slice tracking. Residual in-plane motion and related magnetic susceptibility artifacts were corrected online. The standard deviation of temperature was measured on healthy volunteers (N = 5) in both ventricles. On animals, the MR-compatible catheter was positioned and visualized in the left ventricle (LV) using a bSSFP pulse sequence with active catheter tracking. Twelve MR-guided RFA were performed on three sheep in vivo at various locations in left ventricle (LV). The dimensions of the thermal lesions measured on thermal dose images, on 3D T1-weighted (T1-w) images acquired immediately after the ablation and at gross pathology were correlated. MR thermometry uncertainty was 1.5 °C on average over more than 96% of the pixels covering the left and right ventricles, on each volunteer. On animals, catheter repositioning in the LV with active slice tracking was successfully performed and each ablation could be monitored in real-time by MR thermometry and thermal dosimetry. Thermal lesion dimensions on TD maps were found to be highly correlated with those observed on post-ablation T1-w images (R = 0.87) that also correlated (R = 0.89) with measurements at gross pathology. Quantitative TD mapping from real-time rapid CMR thermometry during catheter-based RFA is feasible. It provides a direct assessment of the lesion extent in the myocardium with precision in the range of one

Biomechanical assessment and monitoring of thermal ablation using Harmonic Motion Imaging for Focused Ultrasound (HMIFU)

NASA Astrophysics Data System (ADS)

Hou, Gary Yi

Cancer remains, one of the major public health problems in the United States as well as many other countries worldwide. According to According to the World Health Organization, cancer is currently the leading cause of death worldwide, accounting for 7.6 million deaths annually, and 25% of the annual death was due to Cancer during the year of 2011. In the long history of the cancer treatment field, many treatment options have been established up to date. Traditional procedures include surgical procedures as well as systemic therapies such as biologic therapy, chemotherapy, hormone therapy, and radiation therapy. Nevertheless, side-effects are often associated with such procedures due to the systemic delivery across the entire body. Recently technologies have been focused on localized therapy under minimally or noninvasive procedure with imaging-guidance, such as cryoablation, laser ablation, radio-frequency (RF) ablation, and High Intensity F-ocused Ultrasound (HIFU). HIFU is a non-invasive procedure aims to coagulate tissue thermally at a localized focal zone created with noninvasively emitting a set of focused ultrasound beams while the surrounding healthy tissues remain relatively untreated. Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a dynamic, radiation-force-based imaging technique, which utilizes a single HIFU transducer by emitting an Amplitude-modulated (AM) beam to both thermally ablate the tumor while inducing a stable oscillatory tissue displacement at its focal zone. The oscillatory response is then estimated by a cross-correlation based motion tracking technique on the signal collected by a confocally-aligned diagnostic transducer. HMIFU addresses the most critical aspect and one of the major unmet needs of HIFU treatment, which is the ability to perform real-time monitoring and mapping of tissue property change during the HIFU treatment. In this dissertation, both the assessment and monitoring aspects of HMIFU have been investigated

Investigation of the wavelength dependence of laser stratigraphy on Cu and Ni coatings using LIBS compared to a pure thermal ablation model

NASA Astrophysics Data System (ADS)

Paulis, Evgeniya; Pacher, Ulrich; Weimerskirch, Morris J. J.; Nagy, Tristan O.; Kautek, Wolfgang

2017-12-01

In this study, galvanic coatings of Cu and Ni, typically applied in industrial standard routines, were investigated. Ablation experiments were carried out using the first two harmonic wavelengths of a pulsed Nd:YAG laser and the resulting plasma spectra were analysed using a linear Pearson correlation method. For both wavelengths the absorption/ablation behaviour as well as laser-induced breakdown spectroscopy (LIBS) depth profiles were studied varying laser fluences between 4.3-17.2 J/cm^2 at 532 nm and 2.9-11.7 J/cm^2 at 1064 nm. The LIBS-stratigrams were compared with energy-dispersive X-ray spectroscopy of cross-sections. The ablation rates were calculated and compared to theoretical values originating from a thermal ablation model. Generally, higher ablation rates were obtained with 532 nm light for both materials. The light-plasma interaction is suggested as possible cause of the lower ablation rates in the infrared regime. Neither clear evidence of the pure thermal ablation, nor correlation with optical properties of investigated materials was obtained.

The Interaction of Mantle Plumes with Surface Thermal and Chemical Boundary Layers: Applications to Hotspots on Venus

NASA Technical Reports Server (NTRS)

Smrekar, S.; Parmentier, E.

1994-01-01

Describes the characteristics of possible hotspots on Venus, the approach used to simulate mantle upwelling, model results, and presents the implications for the properties of plumes and the lithosphere, hotspot evolution, and resurfacing on Venus.

US-guided percutaneous radiofrequency thermal ablation for the treatment of solid benign hyperfunctioning or compressive thyroid nodules.

PubMed

Deandrea, Maurilio; Limone, Paolo; Basso, Edoardo; Mormile, Alberto; Ragazzoni, Federico; Gamarra, Elena; Spiezia, Stefano; Faggiano, Antongiulio; Colao, Annamaria; Molinari, Filippo; Garberoglio, Roberto

2008-05-01

The aim of the study was to define the effectiveness and safety of ultrasound-guided percutaneous radiofrequency (RF) thermal ablation in the treatment of compressive solid benign thyroid nodules. Thirty-one patients not eligible for surgery or radioiodine (131I) treatment underwent RF ablation for benign nodules; a total of 33 nodules were treated (2 patients had 2 nodules treated in the same session): 10 cold nodules and 23 hyperfunctioning. Fourteen patients complained of compressive symptoms. Nodule volume, thyroid function and compressive symptoms were evaluated before treatment and at 1, 3 and 6 mo. Ultrasound-guided RF ablation was performed using a Starbust RITA needle, with nine expandable prongs; total exposure time was 6 to 10 min at 95 degrees C in one area or more of the nodule. Baseline volume (measured at the time of RF ablation) was 27.7 +/- 21.5 mL (mean +/- SD), but significantly decreased during follow-up: 19.2 +/- 16.2 at 1 mo (-32.7%; p < 0.001), 15.9 +/- 14.1 mL at 3 mo (-46.4 %; p < 0.001) and 14.6 +/- 12.6 mL at 6 mo (-50.7%; p < 0.001). After treatment, all patients with cold nodules remained euthyroid: five patients with hot nodules normalized thyroid function, and the remaining sixteen showed a partial remission of hyperthyroidism. Besides a sensation of heat and mild swelling of the neck, no major complications were observed. Improvement in compressive symptoms was reported by 13 patients, with a reduction on severity scale from 6.1 +/- 1.4 to 2.2 +/- 1.9 (p < 0.0001). Radiofrequency was effective and safe in reducing volume by about 50% and compressive symptoms in large benign nodules. Hyperfunction was fully controlled in 24% of patients and partially reduced in the others.

Performance of a Light-Weight Ablative Thermal Protection Material for the Stardust Mission Sample Return Capsule

NASA Technical Reports Server (NTRS)

Covington, M. A.

2005-01-01

New tests and analyses are reported that were carried out to resolve testing uncertainties in the original development and qualification of a lightweight ablative material used for the Stardust spacecraft forebody heat shield. These additional arcjet tests and analyses confirmed the ablative and thermal performance of low density Phenolic Impregnated Carbon Ablator (PICA) material used for the Stardust design. Testing was done under conditions that simulate the peak convective heating conditions (1200 W/cm2 and 0.5 atm) expected during Earth entry of the Stardust Sample Return Capsule. Test data and predictions from an ablative material response computer code for the in-depth temperatures were compared to guide iterative adjustment of material thermophysical properties used in the code so that the measured and predicted temperatures agreed. The PICA recession rates and maximum internal temperatures were satisfactorily predicted by the computer code with the revised properties. Predicted recession rates were also in acceptable agreement with measured rates for heating conditions 37% greater than the nominal peak heating rate of 1200 W/sq cm. The measured in-depth temperature response data show consistent temperature rise deviations that may be caused by an undocumented endothermic process within the PICA material that is not accurately modeled by the computer code. Predictions of the Stardust heat shield performance based on the present evaluation provide evidence that the maximum adhesive bondline temperature will be much lower than the maximum allowable of 250 C and an earlier design prediction. The re-evaluation also suggests that even with a 25 percent increase in peak heating rates, the total recession of the heat shield would be a small fraction of the as-designed thickness. These results give confidence in the Stardust heat shield design and confirm the potential of PICA material for use in new planetary probe and sample return applications.

Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions: An Update of the Technology Maturation Effort

NASA Technical Reports Server (NTRS)

Beck, R.; Arnold, J.; Gasch, M.; Stackpoole, M.; Venkatapathy, E.

2014-01-01

This presentation will update the community on the development of conformal ablative TPS. As described at IPPW-10, in FY12, the CA-TPS element focused on establishing materials requirements based on MSL-type and COTS Low Earth orbit (LEO) conditions (q 250 Wcm2) to develop and deliver a conformal ablative TPS. This involved downselecting, manufacturing and testing two of the best candidate materials, demonstrating uniform infiltration of resins into baseline 2-cm thick carbon felt, selecting a primary conformal material formulation based on novel arc jet and basic material properties testing, developing and demonstrating instrumentation for felt-based materials and, based on the data, developing a low fidelity material response model so that the conformal ablator TPS thickness for missions could be established. In addition, the project began to develop Industry Partnerships. Since the nominal thickness of baseline carbon felts was only 2-cm, a partnership with a rayon felt developer was made in order to upgrade equipment, establish the processes required and attempt to manufacture 10-cm thick white goods. A partnership with a processing house was made to develop the methodology to carbonize large pieces of the white goods into 7.5-cm thick carbon felt.In FY13, more advanced testing and modeling of the downselected conformal material was performed. Material thermal properties tests and structural properties tests were performed. The first 3 and 4-point bend tests were performed on the conformal ablator as well as PICA for comparison and the conformal ablator had outstanding behavior compared to PICA. Arc jet testing was performed with instrumented samples of both the conformal ablator and standard PICA at heating rates ranging from 40 to 400 Wcm2 and shear as high as 600 Pa. The results from these tests showed a remarkable improvement in the thermal penetration through the conformal ablator when compared to PICAs response. The data from these tests were used to

Effect of a poloxamer 407-based thermosensitive gel on minimization of thermal injury to diaphragm during microwave ablation of the liver.

PubMed

Zhang, Li-Li; Xia, Gui-Min; Liu, Yu-Jiang; Dou, Rui; Eisenbrey, John; Liu, Ji-Bin; Wang, Xiao-Wei; Qian, Lin-Xue

2017-03-28

To assess the insulating effect of a poloxamer 407 (P407)-based gel during microwave ablation of liver adjacent to the diaphragm. We prepared serial dilutions of P407, and 22.5% (w/w) concentration was identified as suitable for ablation procedures. Subsequently, microwave ablations were performed on the livers of 24 rabbits (gel, saline, control groups, n = 8 in each). The P407 solution and 0.9% normal saline were injected into the potential space between the diaphragm and liver in experimental groups. No barriers were applied to the controls. After microwave ablations, the frequency, size and degree of thermal injury were compared histologically among the three groups. Subsequently, another 8 rabbits were injected with the P407 solution and microwave ablation was performed. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN) and creatinine (Cr) in serum were tested at 1 d before microwave ablation and 3 and 7 d after operation. In vivo ablation thermal injury to the adjacent diaphragm was evaluated in the control, saline and 22.5% P407 gel groups ( P = 0.001-0.040). However, there was no significant difference in the volume of ablation zone among the three groups ( P > 0.05). Moreover, there were no statistical differences among the preoperative and postoperative gel groups according to the levels of ALT, AST, BUN and Cr in serum (all P > 0.05). Twenty-two point five percent P407 gel could be a more effective choice during microwave ablation of hepatic tumors adjacent to the diaphragm. Further studies for clinical translation are warranted.

Ambient infrared laser ablation mass spectrometry (AIRLAB-MS) of live plant tissue with plume capture by continuous flow solvent probe.

PubMed

O'Brien, Jeremy T; Williams, Evan R; Holman, Hoi-Ying N

2015-03-03

A new experimental setup for spatially resolved ambient infrared laser ablation-mass spectrometry (AIRLAB-MS) that uses an infrared microscope with an infinity-corrected reflective objective and a continuous flow solvent probe coupled to a Fourier transform ion cyclotron resonance mass spectrometer is described. The efficiency of material transfer from the sample to the electrospray ionization emitter was determined using glycerol/methanol droplets containing 1 mM nicotine and is ∼50%. This transfer efficiency is significantly higher than values reported for similar techniques. Laser desorption does not induce fragmentation of biomolecules in droplets containing bradykinin, leucine enkephalin and myoglobin, but loss of the heme group from myoglobin occurs as a result of the denaturing solution used. An application of AIRLAB-MS to biological materials is demonstrated for tobacco leaves. Chemical components are identified from the spatially resolved mass spectra of the ablated plant material, including nicotine and uridine. The reproducibility of measurements made using AIRLAB-MS on plant material was demonstrated by the ablation of six closely spaced areas (within 2 × 2 mm) on a young tobacco leaf, and the results indicate a standard deviation of <10% in the uridine signal obtained for each area. The spatial distribution of nicotine was measured for selected leaf areas and variation in the relative nicotine levels (15-100%) was observed. Comparative analysis of the nicotine distribution was demonstrated for two tobacco plant varieties, a genetically modified plant and its corresponding wild-type, indicating generally higher nicotine levels in the mutant.

Nanobubble Ultrasound Contrast Agents for Enhanced Delivery of Thermal Sensitizer to Tumors Undergoing Radiofrequency Ablation

PubMed Central

Perera, Reshani H.; Solorio, Luis; Wu, Hanping; Gangolli, Mihika; Silverman, Eric; Hernandez, Christopher; Peiris, Pubudu M.; Broome, Ann-Marie

2013-01-01

Purpose Pluronic has been shown to sensitize various tumor cell lines to chemotherapy and hyperthermia by altering the membrane fluidity, depleting ATP, and modulating the heat shock protein 70 expression. In our prior work, Pluronic was also used to formulate nanosized ultrasound contrast agents. In the current study we evaluate the use of these contrast agents as vehicles for image-guided delivery of Pluronic to improve outcomes of tumor radiofrequency (RF) ablation. Methods Lipid-shelled Pluronic nanobubbles were prepared and examined for size distribution, zeta potential, stability, biodistribution, accumulation of nanobubbles in the tumor, and treatment efficacy. LS174-T xenograft tumor-bearing mice were used to evaluate tumor growth suppression and measure treatment efficacy after RF ablation. Results The average diameter of Pluronic bubbles was 230 nm, and initial bubble echogenicity was 16 dB. In vitro, cells exposed to Pluronic nanobubbles exhibited low cytotoxicity in the absence of ultrasound, even if heat (43°C) was applied. When the cells were exposed to Pluronic nanobubbles, heat, and ultrasound; viability was significantly reduced. In vivo, tumors treated with ultrasound-modulated nanobubbles prior to RF ablation showed a significant reduction in growth compared to the RF alone (P<0.05). Conclusion Lipid and Pluronic-shelled, echogenic nanobubbles combined with ultrasound modulation can serve as an effective theranostic method for sensitization of tumors to RF ablation. PMID:23943542

Nanobubble ultrasound contrast agents for enhanced delivery of thermal sensitizer to tumors undergoing radiofrequency ablation.

PubMed

Perera, Reshani H; Solorio, Luis; Wu, Hanping; Gangolli, Mihika; Silverman, Eric; Hernandez, Christopher; Peiris, Pubudu M; Broome, Ann-Marie; Exner, Agata A

2014-06-01

Pluronic has been shown to sensitize various tumor cell lines to chemotherapy and hyperthermia by altering the membrane fluidity, depleting ATP, and modulating the heat shock protein 70 expression. In our prior work, Pluronic was also used to formulate nanosized ultrasound contrast agents. In the current study we evaluate the use of these contrast agents as vehicles for image-guided delivery of Pluronic to improve outcomes of tumor radiofrequency (RF) ablation. Lipid-shelled Pluronic nanobubbles were prepared and examined for size distribution, zeta potential, stability, biodistribution, accumulation of nanobubbles in the tumor, and treatment efficacy. LS174-T xenograft tumor-bearing mice were used to evaluate tumor growth suppression and measure treatment efficacy after RF ablation. The average diameter of Pluronic bubbles was 230 nm, and initial bubble echogenicity was 16 dB. In vitro, cells exposed to Pluronic nanobubbles exhibited low cytotoxicity in the absence of ultrasound, even if heat (43 ºC) was applied. When the cells were exposed to Pluronic nanobubbles, heat, and ultrasound; viability was significantly reduced. In vivo, tumors treated with ultrasound-modulated nanobubbles prior to RF ablation showed a significant reduction in growth compared to the RF alone (P<0.05). Lipid and Pluronic-shelled, echogenic nanobubbles combined with ultrasound modulation can serve as an effective theranostic method for sensitization of tumors to RF ablation.

Update on Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions

NASA Astrophysics Data System (ADS)

Beck, R. A. S.; Arnold, J. O.; Gasch, M. J.; Stackpoole, M. M.; Venkatapathy, E.

2014-06-01

In FY13, more advanced testing and modeling of the new NASA conformal ablative TPS material was performed. Most notable were the 3- and 4-point bending tests and the aerothermal testing on seams and joints in shear. The material outperformed PICA.

Modeling of endoluminal and interstitial ultrasound hyperthermia and thermal ablation: applications to device design, feedback control, and treatment planning

PubMed Central

Prakash, Punit; Salgaonkar, Vasant A.; Diederich, Chris J.

2014-01-01

Endoluminal and catheter-based ultrasound applicators are currently under development and are in clinical use for minimally invasive hyperthermia and thermal ablation of various tissue targets. Computational models play a critical role in in device design and optimization, assessment of therapeutic feasibility and safety, devising treatment monitoring and feedback control strategies, and performing patient-specific treatment planning with this technology. The critical aspects of theoretical modeling, applied specifically to endoluminal and interstitial ultrasound thermotherapy, are reviewed. Principles and practical techniques for modeling acoustic energy deposition, bioheat transfer, thermal tissue damage, and dynamic changes in the physical and physiological state of tissue are reviewed. The integration of these models and applications of simulation techniques in identification of device design parameters, development of real time feedback-control platforms, assessing the quality and safety of treatment delivery strategies, and optimization of inverse treatment plans are presented. PMID:23738697

Langmuir probe measurements and mass spectrometry of plasma plumes generated by laser ablation of La0.4Ca0.6MnO3

NASA Astrophysics Data System (ADS)

Chen, Jikun; Lunney, James G.; Lippert, Thomas; Ojeda-G-P, Alejandro; Stender, Dieter; Schneider, Christof W.; Wokaun, Alexander

2014-08-01

The plasma formed in vacuum by UV nanosecond laser ablation of La0.4Ca0.6MnO3 in the fluence range of 0.8 to 1.9 J cm-2 using both Langmuir probe analysis and energy-resolved mass spectrometry has been studied. Mass spectrometry shows that the main positive ion species are Ca+, Mn+, La+, and LaO+. The Ca+ and Mn+ energy distributions are quite broad and lie in the 0-100 eV region, with the average energies increasing with laser fluence. In contrast, the La+ and LaO+ distributions are strongly peaked around 10 eV. The net time-of-arrival signal derived from the measured positive ion energy distributions is broadly consistent with the positive ion signal measured by the Langmuir probe. We also detected a significant number of O- ions with energies in the range of 0 to 10 eV. The Langmuir probe was also used to measure the temporal variation of the electron density and temperature at 6 cm from the ablation target. In the period when O- ions are found at this position, the plasma conditions are consistent with those required for significant negative oxygen ion formation, as revealed by studies on radio frequency excited oxygen plasma.

Formation of thermal coagulum on multielectrode catheters during phased radiofrequency energy ablation of persistent atrial fibrillation.

PubMed

Debruyne, Philippe; Rossenbacker, Tom; Vankelecom, Bart; Charlier, Filip; Roosen, John; Ector, Bavo; Janssens, Luc

2014-02-01

Radiofrequency ablation (RFA) can unfavorably cause coagulum on the ablation electrode. The aim of this study was to assess this phenomenon on three different multielectrode catheters used to treat persistent atrial fibrillation with duty-cycled RFA. Twenty-six consecutive patients have been treated with the pulmonary vein ablation catheter (PVAC) and the multiarray ablation catheter (MAAC). In 13 patients, additional ablation with the multiarray septal catheter (MASC) has been performed. The multichannel RF generator GENius™ (Medtronic Inc., Minneapolis, MN, USA) independently delivered energy in a bipolar and unipolar mode (ratio of 4/1, 2/1, or 1/1) to any of the electrodes. Versions 14.2, 14.3, and 14.4 of the generator were used. Coagulum presence was determined postablation by careful visual inspection of the catheter electrodes. No coagulum formation was visualized on the PVACs. Coagulum formation was visualized in 59% of the electrodes of the MAACs using a 2/1 mode and the 14.2 software version versus 69% using the 14.4 version and a 2/1 mode (P = 0.7) versus 14% of the electrodes applying a 1/1 ratio and the 14.4 software version (P < 0.001). Duty-cycled RFA in 2/1 bipolar/unipolar ratio generates a substantial frequency of coagulum formation on the multielectrode catheters MAAC and MASC. The use of the 14.4 version of the software to drive the RF generator and the use of energy in the default 1/1 bipolar/unipolar ratio could significantly reduce the frequency of coagulum formation, but so far, could not completely overcome it. The PVAC did not form coagulum, regardless of generator version or energy ratio used. ©2013, The Authors. Journal compilation ©2013 Wiley Periodicals, Inc.

Moldable cork ablation material

NASA Technical Reports Server (NTRS)

1977-01-01

A successful thermal ablative material was manufactured. Moldable cork sheets were tested for density, tensile strength, tensile elongation, thermal conductivity, compression set, and specific heat. A moldable cork sheet, therefore, was established as a realistic product.

Plume radiation

NASA Astrophysics Data System (ADS)

Dirscherl, R.

1993-06-01

The electromagnetic radiation originating from the exhaust plume of tactical missile motors is of outstanding importance for military system designers. Both missile- and countermeasure engineer rely on the knowledge of plume radiation properties, be it for guidance/interference control or for passive detection of adversary missiles. To allow access to plume radiation properties, they are characterized with respect to the radiation producing mechanisms like afterburning, its chemical constituents, and reactions as well as particle radiation. A classification of plume spectral emissivity regions is given due to the constraints imposed by available sensor technology and atmospheric propagation windows. Additionally assessment methods are presented that allow a common and general grouping of rocket motor properties into various categories. These methods describe state of the art experimental evaluation techniques as well as calculation codes that are most commonly used by developers of NATO countries. Dominant aspects influencing plume radiation are discussed and a standardized test technique is proposed for the assessment of plume radiation properties that include prediction procedures. These recommendations on terminology and assessment methods should be common to all employers of plume radiation. Special emphasis is put on the omnipresent need for self-protection by the passive detection of plume radiation in the ultraviolet (UV) and infrared (IR) spectral band.

The in vivo performance of a novel thermal accelerant agent used for augmentation of microwave energy delivery within biologic tissues during image-guided thermal ablation: a porcine study.

PubMed

Park, William Keun Chan; Maxwell, Aaron Wilhelm Palmer; Frank, Victoria Elizabeth; Primmer, Michael Patrick; Paul, Jarod Brian; Collins, Scott Andrew; Lombardo, Kara Anne; Lu, Shaolei; Borjeson, Tiffany Marie; Baird, Grayson Luderman; Dupuy, Damian Edward

2018-02-01

To investigate the effects of a novel caesium-based thermal accelerant (TA) agent on ablation zone volumes following in vivo microwave ablation of porcine liver and skeletal muscle, and to correlate the effects of TA with target organ perfusion. This prospective study was performed following institutional animal care and use committee approval. Microwave ablation was performed in liver and resting skeletal muscle in eight Sus scrofa domesticus swine following administration of TA at concentrations of 0 mg/mL (control), 100 mg/mL and 250 mg/mL. Treated tissues were explanted and stained with triphenyltetrazolium chloride (TTC) for quantification of ablation zone volumes, which were compared between TA and control conditions. Hematoxylin and eosin (H&E) staining was also performed for histologic analysis. General mixed modelling with a log-normal distribution was used for all quantitative comparisons (p = 0.05). A total of 28 ablations were performed in the liver and 18 in the skeletal muscle. The use of TA significantly increased ablation zone volumes in a dose-dependent manner in both the porcine muscle and liver (p < 0.01). Both the absolute mean ablation zone volume and percentage increase in ablation zone volume were greater in the resting skeletal muscle than in the liver. In one swine, a qualitative mitigation of heat sink effects was observed by TTC and H&E staining. Non-lethal polymorphic ventricular tachycardia was identified in one swine, treated with intravenous amiodarone. The use of a novel TA agent significantly increased mean ablation zone volumes following microwave ablation using a porcine model. The relationship between TA administration and ablation size was dose-dependent and inversely proportional to the degree of target organ perfusion, and a qualitative reduction in heat-sink effects was observed.

Characterization and initial field test of an 8-14 μm thermal infrared hyperspectral imager for measuring SO2 in volcanic plumes

NASA Astrophysics Data System (ADS)

Gabrieli, Andrea; Wright, Robert; Lucey, Paul G.; Porter, John N.; Garbeil, Harold; Pilger, Eric; Wood, Mark

2016-10-01

The ability to image and quantify SO2 path-concentrations in volcanic plumes, either by day or by night, is beneficial to volcanologists. Gas emission rates are affected by the chemical equilibria in rising magmas and a better understanding of this relationship would be useful for short-term eruption prediction. A newly developed remote sensing long-wave thermal InfraRed (IR) imaging hyperspectral sensor - the Thermal Hyperspectral Imager (THI) - was built and tested. The system employs a Sagnac interferometer and an uncooled microbolometer in rapid scanning configuration to collect hyperspectral images of volcanic plumes. Each pixel in the resulting image yields a spectrum with 50 samples between 8 and 14 μm. Images are spectrally and radiometrically calibrated using an IR source with a narrow band filter and two blackbodies. In this paper, the sensitivity of the instrument for the purpose of quantifying SO2 using well constrained laboratory experiments is evaluated, and initial field results from Kīlauea volcano, Hawai'i, are presented. The sensitivity of THI was determined using gas cells filled with known concentrations of SO2 and using NIST-traceable blackbodies to simulate a range of realistic background conditions. Measurements made by THI were then benchmarked against a high spectral resolution off-the-shelf Michelson FTIR instrument. Theoretical thermal IR spectral radiances were computed with MODTRAN5 for the same optical conditions, to evaluate how well the (known) concentration of SO2 in the gas cells could be retrieved from the resulting THI spectra. Finally, THI was recently field-tested at Kīlauea to evaluate its ability to image the concentration of SO2 in a real volcanic plume. A path-concentration of 7150 ppm m was retrieved from measurements made near the Halema'uma'u vent.

A Systematic Review and Meta-analysis of Thrombotic Events Following Endovenous Thermal Ablation of the Great Saphenous Vein.

PubMed

Healy, Donagh A; Kimura, Shiori; Power, David; Elhaj, Abubaker; Abdeldaim, Yasser; Cross, Keith S; McGreal, Gerard T; Burke, Paul E; Moloney, Tony; Manning, Brian J; Kavanagh, Eamon G

2018-06-09

A systematic review and meta-analysis was performed to determine the incidence of thrombotic events following great saphenous vein (GSV) endovenous thermal ablation (EVTA). MEDLINE, Embase and conference abstracts were searched. Eligible studies were randomised controlled trials and case series that included at least 100 patients who underwent GSV EVTA (laser ablation or radiofrequency ablation [RFA]) with duplex ultrasound (DUS) within 30 days. The systematic review focused on the complications of endovenous heat induced thrombosis (EHIT), deep venous thrombosis (DVT), and pulmonary embolism (PE). The primary outcome for the meta-analysis was deep venous thrombotic events which were defined as DVT or EHIT Type 2, 3, or 4. Secondary outcomes for the meta-analysis were EHIT Type 2, 3, or 4, DVT and PE. Subgroup analyses were performed for both the RFA and EVLA groups. Pooled proportions were calculated using random effects modelling. Fifty-two studies (16,398 patients) were included. Thrombotic complications occurred infrequently. Deep venous thrombotic events occurred in 1.7% of cases (95% CI 0.9-2.7%) (25 studies; 10,012 patients; 274 events). EHIT Type 2, 3, or 4 occurred in 1.4% of cases (95% CI 0.8-2.3%) (26 studies; 10,225 patients; 249 events). DVT occurred in 0.3% of cases (95% CI = 0.2%-0.5%) (49 studies; 15,676 patients; 48 events). PE occurred in 0.1% of cases (95% CI = 0.1-0.2%) (29 studies; 8223 patients; 3 events). Similar results were found when the RFA and EVLA groups were analysed separately. Thrombotic events occur infrequently following GSV EVTA. Given the large numbers of procedures worldwide and the potential for serious consequences, further research is needed on the burden of these complications and their management. Copyright © 2018 European Society for Vascular Surgery. Published by Elsevier B.V. All rights reserved.

Radiographic Local Tumor Control and Pain Palliation of Sarcoma Metastases within the Musculoskeletal System with Percutaneous Thermal Ablation.

PubMed

Vaswani, Devin; Wallace, Adam N; Eiswirth, Preston S; Madaelil, Thomas P; Chang, Randy O; Tomasian, Anderanik; Jennings, Jack W

2018-03-14

To evaluate the effectiveness of percutaneous image-guided thermal ablation in achieving local tumor control and pain palliation of sarcoma metastases within the musculoskeletal system. Retrospective review of 64 sarcoma metastases within the musculoskeletal system in 26 women and 15 men (total = 41) treated with ablation between December 2011 and August 2016 was performed. Mean age of the cohort was 42.9 years ± 16.0 years. Two subgroups were treated: oligometastatic disease (n = 13) and widely metastatic disease (n = 51). A variety of sarcoma histologies were treated with average tumor volume of 42.5 cm 3 (range 0.1-484.7 cm 3 ). Pain scores were recorded before and 4 weeks after therapy for 59% (38/64) of treated lesions. Follow-up imaging was evaluated for local control and to monitor sites of untreated disease as an internal control. Fifty-eight percent (37/64) were lost to imaging follow-up at varying time points over a year. Complication rate was 5% (3/64; one minor and two major events). One-year local tumor control rates were 70% (19/27) in all patients, 67% (12/18) in the setting of progression of untreated metastases, and 100% (10/10) in the setting of oligometastatic disease. Median pain scores decreased from 8 (interquartile range 5.0-9.0) to 3 (interquartile range 0.1-4.0) 1 month after the procedure (P < 0.001). Image-guided percutaneous ablation is an effective option for local tumor control and pain palliation of metastatic sarcomas within the musculoskeletal system. Treatment in the setting of oligometastatic disease offers potential for remission. Level 4, Retrospective Review.

High-speed scanning ablation of dental hard tissues with a λ=9.3-μm CO2 laser: heat accumulation and peripheral thermal damage

NASA Astrophysics Data System (ADS)

Nguyen, Daniel; Staninec, Michal; Lee, Chulsung; Fried, Daniel

2010-02-01

A mechanically scanned CO2 laser operated at high laser pulse repetition rates can be used to rapidly and precisely remove dental decay. This study aims to determine whether these laser systems can safely ablate enamel and dentin without excessive heat accumulation and peripheral thermal damage. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. Samples were derived from noncarious extracted molars. Pulpal temperatures were recorded using microthermocouples situated at the pulp chamber roof of samples (n=12), which were occlusally ablated using a rapid-scanning, water-cooled 300 Hz CO2 laser over a two minute time course. The mechanical strength of facially ablated dentin (n=10) was determined via four-point bend test and compared to control samples (n=10) prepared with 320 grit wet sand paper to simulate conventional preparations. Composite-to-enamel bond strength was measured via single-plane shear test for ablated/non-etched (n=10) and ablated/acid-etched (n=8) samples and compared to control samples (n=9) prepared by 320 grit wet sanding. Thermocouple measurements indicated that the temperature remained below ambient temperature at 19.0°C (s.d.=0.9) if water-cooling was used. There was no discoloration of either dentin and enamel, the treated surfaces were uniformly ablated and there were no cracks observable on the laser treated surfaces. Fourpoint bend tests yielded mean mechanical strengths of 18.2 N (s.d.=4.6) for ablated dentin and 18.1 N (s.d.=2.7) for control (p>0.05). Shear tests yielded mean bond strengths of 31.2 MPa (s.d.=2.5, p<0.01) for ablated/acid-etched samples, 5.2 MPa (s.d.=2.4, p<0.001) for ablated/non-etched samples, and 37.0 MPa (s.d.=3.6) for control. The results indicate that a rapid-scanning 300 Hz CO2 laser can effectively ablate dentin and enamel without excessive heat accumulation and with minimal

Seismic Imaging of Mantle Plumes

NASA Astrophysics Data System (ADS)

Nataf, Henri-Claude

The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

Heat Stress-Induced PI3K/mTORC2-Dependent AKT Signaling Is a Central Mediator of Hepatocellular Carcinoma Survival to Thermal Ablation Induced Heat Stress

PubMed Central

Thompson, Scott M.; Callstrom, Matthew R.; Jondal, Danielle E.; Butters, Kim A.; Knudsen, Bruce E.; Anderson, Jill L.; Lien, Karen R.; Sutor, Shari L.; Lee, Ju-Seog; Thorgeirsson, Snorri S.; Grande, Joseph P.; Roberts, Lewis R.; Woodrum, David A.

2016-01-01

Thermal ablative therapies are important treatment options in the multidisciplinary care of patients with hepatocellular carcinoma (HCC), but lesions larger than 2–3 cm are plagued with high local recurrence rates and overall survival of these patients remains poor. Currently no adjuvant therapies exist to prevent local HCC recurrence in patients undergoing thermal ablation. The molecular mechanisms mediating HCC resistance to thermal ablation induced heat stress and local recurrence remain unclear. Here we demonstrate that the HCC cells with a poor prognostic hepatic stem cell subtype (Subtype HS) are more resistant to heat stress than HCC cells with a better prognostic hepatocyte subtype (Subtype HC). Moreover, sublethal heat stress rapidly induces phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dependent-protein kinase B (AKT) survival signaling in HCC cells in vitro and at the tumor ablation margin in vivo. Conversely, inhibition of PI3K/mTOR complex 2 (mTORC2)-dependent AKT phosphorylation or direct inhibition of AKT function both enhance HCC cell killing and decrease HCC cell survival to sublethal heat stress in both poor and better prognostic HCC subtypes while mTOR complex 1 (mTORC1)-inhibition has no impact. Finally, we showed that AKT isoforms 1, 2 and 3 are differentially upregulated in primary human HCCs and that overexpression of AKT correlates with worse tumor biology and pathologic features (AKT3) and prognosis (AKT1). Together these findings define a novel molecular mechanism whereby heat stress induces PI3K/mTORC2-dependent AKT survival signaling in HCC cells and provide a mechanistic rationale for adjuvant AKT inhibition in combination with thermal ablation as a strategy to enhance HCC cell killing and prevent local recurrence, particularly at the ablation margin. PMID:27611696

Radiofrequency Thermal Ablation Heat Energy Transfer in an Ex-Vivo Model.

PubMed

Thakur, Shivani; Lavito, Sandi; Grobner, Elizabeth; Grobner, Mark

2017-12-01

Little work has been done to consider the temperature changes and energy transfer that occur in the tissue outside the vein with ultrasound-guided vein ablation therapy. In this experiment, a Ex-Vivo model of the human calf was used to analyze heat transfer and energy degradation in tissue surrounding the vein during endovascular radiofrequency ablation (RFA). A clinical vein ablation protocol was used to determine the tissue temperature distribution in 10 per cent agar gel. Heat energy from the radiofrequency catheter was measured for 140 seconds at fixed points by four thermometer probes placed equidistant radially at 0.0025, 0.005, and 0.01 m away from the RFA catheter. The temperature rose 1.5°C at 0.0025 m, 0.6°C at 0.005 m, and 0.0°C at 0.01 m from the RFA catheter. There was a clinically insignificant heat transfer at the distances evaluated, 1.4 ± 0.2 J/s at 0.0025 m, 0.7 ± 0.3 J/s at 0.0050 m, and 0.3 ± 0.0 J/s at 0.01 m. Heat degradation occurred rapidly: 4.5 ± 0.5 J (at 0.0025 m), 4.0 ± 1.6 J (at 0.0050 m), and 3.9 ± 3.6 J (at 0.01 m). Tumescent anesthesia injected one centimeter around the vein would act as a heat sink to absorb the energy transferred outside the vein to minimize tissue and nerve damage and will help phlebologists strategize options for minimizing damage.

Considerations for ex vivo thermal tissue testing exemplified using the fresh porcine longissimus muscle model for endometrial ablation

NASA Astrophysics Data System (ADS)

Fugett, James H.; Bennett, Haydon E.; Shrout, Joshua L.; Coad, James E.

2017-02-01

Expansions in minimally invasive medical devices and technologies with thermal mechanisms of action are continuing to advance the practice of medicine. These expansions have led to an increasing need for appropriate animal models to validate and quantify device performance. The planning of these studies should take into consideration a variety of parameters, including the appropriate animal model (test system - ex vivo or in vivo; species; tissue type), treatment conditions (test conditions), predicate device selection (as appropriate, control article), study timing (Day 0 acute to more than Day 90 chronic survival studies), and methods of tissue analysis (tissue dissection - staining methods). These considerations are discussed and illustrated using the fresh extirpated porcine longissimus muscle model for endometrial ablation.

Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions:An Overview of the Technology Maturation Effort

NASA Technical Reports Server (NTRS)

Beck, Robin A S.; Arnold, James O.; Gasch, Matthew J.; Stackpoole, Margaret M.; Prabhu, Dinesh K.; Szalai, Christine E.; Wercinski, Paul F.; Venkatapathy, Ethiraj

2013-01-01

The Office of Chief Technologist, NASA identified the need for research and technology development in part from NASAs Strategic Goal 3.3 of the NASA Strategic Plan to develop and demonstrate the critical technologies that will make NASAs exploration, science, and discovery missions more affordable and more capable. Furthermore, the Game Changing Development Program is a primary avenue to achieve the Agencys 2011 strategic goal to Create the innovative new space technologies for our exploration, science, and economic future. The National Research Council (NRC) Space Technology Roadmaps and Priorities report highlights six challenges and they are: Mass to Surface, Surface Access, Precision Landing, Surface Hazard Detection and Avoidance, Safety and Mission Assurance, and Affordability. In order for NASA to meet these challenges, the report recommends immediate focus on Rigid and Flexible Thermal Protection Systems. Rigid TPS systems such as Avcoat or SLA are honeycomb based and PICA is in the form of tiles. The honeycomb systems are manufactured using techniques that require filling of each (38 cell) by hand, and in a limited amount of time all of the cells must be filled and the heatshield must be cured. The tile systems such as PICA pose a different challenge as the low strain-to-failure and manufacturing size limitations require large number of small tiles with gap-fillers between the tiles. Recent investments in flexible ablative systems have given rise to the potential for conformal ablative TPS. A conformal TPS over a rigid aeroshell has the potential to solve a number of challenges faced by traditional rigid TPS materials. The high strain-to-failure nature of the conformal ablative materials will allow integration of the TPS with the underlying aeroshell structure much easier and enable monolithic-like configuration and larger segments (or parts) to be used. By reducing the overall part count, the cost of installation (based on cost comparisons between blanket

Ablation velocity and thermal damage of myocardial tissue using a CO2 laser for transmyocardial laser revascularization

NASA Astrophysics Data System (ADS)

Sachinopoulou, Anna; Beek, Johan F.; van Leeuwen, Ton G. J. M.; Beek, W. J.

1999-02-01

Transmyocardial Laser Revascularization (TMLR) is a new experimental method for relief of angina pectoris in patients with severe coronary artery disease. TMLR aims at revascularizing chronic hibernating myocardium by creating transmural channels. One of the working mechanism hypotheses is that the endocardial side of the channels remains open, enabling perfusion of the hibernating myocardium directly from the left ventricle. Although the working mechanism of TMLR is still unknown (perfusion through patent channels, induction of angiogenesis, relief of angina through destruction of sympatic innervation, others?), first clinical studies are successful. Currently, the Heart LaserTM and other CO2 lasers, XeCl Excimer laser and Ho:YAG laser are under investigation for TMLR. The initial attempts of TMR with needles were soon replaced by laser induced channels. Efforts were focused on developing a CO2 laser that could penetrate a beating heart during its relaxation phase. Later, the position of the beam could be fixed in the myocardial wall using lasers with fiber delivery systems and perforation was achieved within multiple cycles. Various researchers reported on both patent and non-patent channels after TMLR. Our belief is that the extent of laser induced thermal damage is one of the factors that determine the clinical outcome and the extent of angiogenesis (and, possibly, the patency of the channel). The purpose of this study is to present a simple theoretical model to predict the extent of thermal damage around a transmyocardial channel. In vitro experiments were performed on myocardial bovine tissue and damage was assessed. The results were used to determine the final parameters of the approximating theoretical equation. To evaluate our results, we compared our results to in vitro data using the Heart LaserTM from the literature. Ablation velocities were also measured and the results were compared to ablation velocity calculations using a model described by Ostegar

The effects of electron thermal radiation on laser ablative shock waves from aluminum plasma into ambient air

SciTech Connect

Sai Shiva, S.; Leela, Ch.; Prem Kiran, P., E-mail: premkiranuoh@gmail.com, E-mail: prem@uohyd.ac.in

2016-05-15

The effect of electron thermal radiation on 7 ns laser ablative shock waves from aluminum (Al) plasma into an ambient atmospheric air has been numerically investigated using a one-dimensional, three-temperature (electron, ion, and radiation) radiation hydrodynamic code MULTI. The governing equations in Lagrangian form are solved using an implicit scheme for planar, cylindrical, and spherical geometries. The shockwave velocities (V{sub sw}) obtained numerically are compared with our experimental values obtained over the intensity range of 2.0 × 10{sup 10} to 1.4 × 10{sup 11 }W/cm{sup 2}. It is observed that the numerically obtained V{sub sw} is significantly influenced by the thermal radiation effects which are foundmore » to be dominant in the initial stage up to 2 μs depending on the input laser energy. Also, the results are found to be sensitive to the co-ordinate geometry used in the simulation (planar, cylindrical, and spherical). Moreover, it is revealed that shock wave undergoes geometrical transitions from planar to cylindrical nature and from cylindrical to spherical nature with time during its propagation into an ambient atmospheric air. It is also observed that the spatio-temporal evolution of plasma electron and ion parameters such as temperature, specific energy, pressure, electron number density, and mass density were found to be modified significantly due to the effects of electron thermal radiation.« less

Guidelines of the First International Consensus Conference on Endovenous Thermal Ablation for Varicose Vein Disease--ETAV Consensus Meeting 2012.

PubMed

Pavlović, Miloš D; Schuller-Petrović, Sanja; Pichot, Olivier; Rabe, Eberhard; Maurins, Uldis; Morrison, Nick; Pannier, Felizitas

2015-05-01

Endovenous thermal ablation (ETA) procedures are catheter-directed, ultrasound (US)-guided thermal methods for treatment in varicose veins disease. Radiofrequency, laser or steam energy thermally denatures vein wall collagen, leading first to vein wall inflammation, then fibrosis and finally to occlusion. The aim of this guideline is to give evidence-based recommendations for ETA procedures. These guidelines were drafted during a consensus meeting of a group of experts in the field of ETA in June 2012 (Hvar, Croatia) under the auspices of the International Union of Phlebology (IUP). These guidelines review the present state of knowledge as reflected in peer-reviewed published medical literature. The recommendations of these guidelines are graded according to the American College of Chest Physicians Task Force recommendations on Grading Strength of Recommendations and Quality of Evidence in Clinical Guidelines. Recommendations on the use of ETA procedures were made based on the quality of evidence for efficacy, safety, tolerability, cosmetic outcome, patient satisfaction/preference and, where appropriate, on the experts' opinion. Health economics were not considered, since differences in national health systems and pricing make it difficult to form general conclusions that are relevant at an international level. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Thermal Ablation in the Management of Adrenal Metastasis Originating from Non-small Cell Lung Cancer: A 5-year Single-center Experience

PubMed Central

Botsa, Evanthia I; Thanou, Ioanna L; Papatheodoropoulou, Aspasia T; Thanos, Loukas I

2017-01-01

Background: Treatment of adrenal metastasis from lung carcinoma may prolong survival in the selected patients. However, not all patients can undergo surgery; thus, minimally invasive ablation procedures such as radiofrequency ablation (RFA) and microwave ablation (MWA) have gained acceptance as alternative treatment methods. This study summarized a 5-year single-center experience regarding the evaluation of safety and efficacy of computed tomography (CT)-guided thermal ablation in the management of adrenal metastasis originating from non-small cell lung cancer (NSCLC). Methods: The data of NSCLC patients ablated for adrenal metastasis at the Department of Diagnostic Imaging and Interventional Radiology, General Hospital Sotiria, were retrospectively analyzed. Patients were divided into two groups: RFA group and MWA group according to the therapeutic approaches. Preprocedural blood tests included measurement of international normalized ratio, partial thromboplastin time, and platelet enumeration. A dual-phase contrast-enhanced spiral CT was performed immediately after the procedure to assess the immediate response after ablation and to screen for related complications. Follow-up was performed with CT or magnetic resonance imaging at 1, 3, 6 months and 1 year after ablation and every 6 months thereafter. Results: A total of 99 ablation sessions in 71 patients with adrenal metastasis originating from NSCLC were included in the final analysis. Self-limited, postablation syndrome occurred in 16/99 (16.1%) of ablation sessions. All procedures were technically successful. Immediate postablation imaging showed no contrast enhancement of the ablated tumor in all patients. Follow-up imaging at 3 months revealed local tumor progression in 8 (22.8%) patients of the RFA group and 7 (19.4%) patients of MWA group, all of them underwent a second session successfully. The 1-year assessment revealed local recurrence of the ablated tumor in six patients (17.1%) of RFA group and seven

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

NASA Astrophysics Data System (ADS)

Badin, Alice; Broholm, Mette M.; Jacobsen, Carsten S.; Palau, Jordi; Dennis, Philip; Hunkeler, Daniel

2016-09-01

Thermal tetrachloroethene (PCE) remediation by steam injection in a sandy aquifer led to the release of dissolved organic carbon (DOC) from aquifer sediments resulting in more reduced redox conditions, accelerated PCE biodegradation, and changes in microbial populations. These changes were documented by comparing data collected prior to the remediation event and eight years later. Based on the premise that dual C-Cl isotope slopes reflect ongoing degradation pathways, the slopes associated with PCE and TCE suggest the predominance of biotic reductive dechlorination near the source area. PCE was the predominant chlorinated ethene near the source area prior to thermal treatment. After thermal treatment, cDCE became predominant. The biotic contribution to these changes was supported by the presence of Dehalococcoides sp. DNA (Dhc) and Dhc targeted rRNA close to the source area. In contrast, dual C-Cl isotope analysis together with the almost absent VC 13C depletion in comparison to cDCE 13C depletion suggested that cDCE was subject to abiotic degradation due to the presence of pyrite, possible surface-bound iron (II) or reduced iron sulphides in the downgradient part of the plume. This interpretation is supported by the relative lack of Dhc in the downgradient part of the plume. The results of this study show that thermal remediation can enhance the biodegradation of chlorinated ethenes, and that this effect can be traced to the mobilisation of DOC due to steam injection. This, in turn, results in more reduced redox conditions which favor active reductive dechlorination and/or may lead to a series of redox reactions which may consecutively trigger biotically induced abiotic degradation. Finally, this study illustrates the valuable complementary application of compound-specific isotopic analysis combined with molecular biology tools to evaluate which biogeochemical processes are taking place in an aquifer contaminated with chlorinated ethenes.

Low altitude plume impingement handbook

NASA Technical Reports Server (NTRS)

Smith, Sheldon D.

1991-01-01

Plume Impingement modeling is required whenever an object immersed in a rocket exhaust plume must survive or remain undamaged within specified limits, due to thermal and pressure environments induced by the plume. At high altitudes inviscid plume models, Monte Carlo techniques along with the Plume Impingement Program can be used to predict reasonably accurate environments since there are usually no strong flowfield/body interactions or atmospheric effects. However, at low altitudes there is plume-atmospheric mixing and potential large flowfield perturbations due to plume-structure interaction. If the impinged surface is large relative to the flowfield and the flowfield is supersonic, the shock near the surface can stand off the surface several exit radii. This results in an effective total pressure that is higher than that which exists in the free plume at the surface. Additionally, in two phase plumes, there can be strong particle-gas interaction in the flowfield immediately ahead of the surface. To date there have been three levels of sophistication that have been used for low altitude plume induced environment predictions. Level 1 calculations rely on empirical characterizations of the flowfield and relatively simple impingement modeling. An example of this technique is described by Piesik. A Level 2 approach consists of characterizing the viscous plume using the SPF/2 code or RAMP2/LAMP and using the Plume Impingement Program to predict the environments. A Level 3 analysis would consist of using a Navier-Stokes code such as the FDNS code to model the flowfield and structure during a single calculation. To date, Level 1 and Level 2 type analyses have been primarily used to perform environment calculations. The recent advances in CFD modeling and computer resources allow Level 2 type analysis to be used for final design studies. Following some background on low altitude impingement, Level 1, 2, and 3 type analysis will be described.

Infra-red and vibration tests of hybrid ablative/ceramic matrix technological breadboards for earth re-entry thermal protection systems

NASA Astrophysics Data System (ADS)

Barcena, Jorge; Garmendia, Iñaki; Triantou, Kostoula; Mergia, Konstatina; Perez, Beatriz; Florez, Sonia; Pinaud, Gregory; Bouilly, Jean-Marc; Fischer, Wolfgang P. P.

2017-05-01

A new thermal protection system for atmospheric earth re-entry is proposed. This concept combines the advantages of both reusable and ablative materials to establish a new hybrid concept with advanced capabilities. The solution consists of the design and the integration of a dual shield resulting on the overlapping of an external thin ablative layer with a Ceramic Matrix Composite (CMC) thermo-structural core. This low density ablative material covers the relatively small heat peak encountered during re-entry the CMC is not able to bear. On the other hand the big advantage of the CMC based TPS is of great benefit which can deal with the high integral heat for the bigger time period of the re-entry. To verify the solution a whole testing plan is envisaged, which as part of it includes thermal shock test by infra-red heating (heating flux up to 1 MW/m2) and vibration test under launcher conditions (Volna and Ariane 5). Sub-scale tile samples (100×100 mm2) representative of the whole system (dual ablator/ceramic layers, insulation, stand-offs) are specifically designed, assembled and tested (including the integration of thermocouples). Both the thermal and the vibration test are analysed numerically by simulation tools using Finite Element Models. The experimental results are in good agreement with the expected calculated parameters and moreover the solution is qualified according to the specified requirements.

Design, qualification, manufacturing and integration of IXV Ablative Thermal Protection System

NASA Astrophysics Data System (ADS)

Cioeta, Mario; Di Vita, Gandolfo; Signorelli Maria, Teresa; Bianco, Gianluca; Cutroni, Maurizio; Damiani, Francesco; Ferretti, Viviana; Rotondo, Adriano

2016-07-01

In the present paper, all the activities carried out by Avio S.p.A in order to define, qualify, manufacture and integrate the IXV Ablative TPS will be presented. In particular the extensive numerical simulation in both small and full scale testing activities will be overviewed. Wide-ranging testing activity has been carried out in order to verify, confirm and correlate the numerical models used for TPS sizing. Tests ranged from classical thermo-mechanical characterization traction specimens to tests in plasma wind tunnels on dedicated prototypes. Finally manufacturing and integration activities will be described emphasizing technological aspects solved in order to meet the stringent requirements in terms of shape accuracy and integration tolerances.

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, D.N.

1996-09-24

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, Douglas N.

1996-01-01

A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target.

In vitro thermal profile suitability assessment of acids and bases for thermochemical ablation: underlying principles.

PubMed

Freeman, Laura A; Anwer, Bilal; Brady, Ryan P; Smith, Benjamin C; Edelman, Theresa L; Misselt, Andrew J; Cressman, Erik N K

2010-03-01

To measure and compare temperature changes in a recently developed gel phantom for thermochemical ablation as a function of reagent strength and concentration with several acids and bases. Aliquots (0.5-1 mL) of hydrochloric acid or acetic acid and sodium hydroxide or aqueous ammonia were injected for 5 seconds into a hydrophobic gel phantom. Stepwise increments in concentration were used to survey the temperature changes caused by these reactions. Injections were performed in triplicate, measured with a thermocouple probe, and plotted as functions of concentration and time. Maximum temperatures were reached almost immediately in all cases, reaching 75 degrees C-110 degrees C at the higher concentrations. The highest temperatures were seen with hydrochloric acid and either base. More concentrated solutions of sodium hydroxide tended to mix incompletely, such that experiments at 9 M and higher were difficult to perform consistently. Higher concentrations for any reagent resulted in higher temperatures. Stronger acid and base combinations resulted in higher temperatures versus weak acid and base combinations at the same concentration. Maximum temperatures obtained are in a range known to cause tissue coagulation, and all combinations tested therefore appeared suitable for further investigation in thermochemical ablation. Because of the loss of the reaction chamber shape at higher concentrations of stronger agents, the phantom does not allow complete characterization under these circumstances. Adequate mixing of reagents to maximize heating potential and avoid systemic exposure to unreacted acid and base must be addressed if the method is to be safely employed in tissues. In addition, understanding factors that control lesion shape in a more realistic tissue model will be critical. Copyright 2010 SIR. Published by Elsevier Inc. All rights reserved.

Computational modelling of internally cooled wet (ICW) electrodes for radiofrequency ablation: impact of rehydration, thermal convection and electrical conductivity.

PubMed

Trujillo, Macarena; Bon, Jose; Berjano, Enrique

2017-09-01

(1) To analyse rehydration, thermal convection and increased electrical conductivity as the three phenomena which distinguish the performance of internally cooled electrodes (IC) and internally cooled wet (ICW) electrodes during radiofrequency ablation (RFA), (2) Implement a RFA computer model with an ICW which includes these phenomena and (3) Assess their relative influence on the thermal and electrical tissue response and on the coagulation zone size. A 12-min RFA in liver was modelled using an ICW electrode (17 G, 3 cm tip) by an impedance-control pulsing protocol with a constant current of 1.5 A. A model of an IC electrode was used to compare the ICW electrode performance and the computational results with the experimental results. Rehydration and increased electrical conductivity were responsible for an increase in coagulation zone size and a delay (or absence) in the occurrence of abrupt increases in electrical impedance (roll-off). While the increased electrical conductivity had a remarkable effect on enlarging the coagulation zone (an increase of 0.74 cm for differences in electrical conductivity of 0.31 S/m), rehydration considerably affected the delay in roll-off, which, in fact, was absent with a sufficiently high rehydration level. In contrast, thermal convection had an insignificant effect for the flow rates considered (0.05 and 1 mL/min). Computer results suggest that rehydration and increased electrical conductivity were mainly responsible for the absence of roll-off and increased size of the coagulation zone, respectively, and in combination allow the thermal and electrical performance of ICW electrodes to be modelled during RFA.

Tapered fiber optic applicator for laser ablation: Theoretical and experimental assessment of thermal effects on ex vivo model.

PubMed

Saccomandi, P; Di Matteo, F M; Schena, E; Quero, G; Massaroni, C; Giurazza, F; Costamagna, G; Silvestri, S

2017-07-01

Laser Ablation (LA) is a minimally invasive technique for tumor removal. The laser light is guided into the target tissue by a fiber optic applicator; thus the physical features of the applicator tip strongly influence size and shape of the tissue lesion. This study aims to verify the geometry of the lesion achieved by a tapered-tip applicator, and to investigate the percentage of thermally damaged cells induced by the tapered-tip fiber optic applicator. A theoretical model was implemented to simulate: i) the distribution of laser light fluence rate in the tissue through Monte Carlo method, ii) the induced temperature distribution, by means of the Bio Heat Equation, iii) the tissue injury, by Arrhenius integral. The results obtained by the implementation of the theoretical model were experimentally assessed. Ex vivo porcine liver underwent LA with tapered-tip applicator, at different laser settings (laser power of 1 W and 1.7 W, deposited energy equal to 330 J and 500 J, respectively). Almost spherical volume lesions were produced. The thermal damage was assessed by measuring the diameter of the circular-shaped lesion. The comparison between experimental results and theoretical prediction shows that the thermal damage discriminated by visual inspection always corresponds to a percentage of damaged cells of 96%. A tapered-tip applicator allows obtaining localized and reproducible damage close to spherical shape, whose diameter is related to the laser settings, and the simple theoretical model described is suitable to predict the effects, in terms of thermal damage, on ex vivo liver. Further trials should be addressed to adapt the model also on in vivo tissue, aiming to develop a tool useful to support the physician in clinical application of LA.

Millisecond laser ablation of molybdenum target in reactive gas toward MoS2 fullerene-like nanoparticles with thermally stable photoresponse.

PubMed

Song, Shu-Tao; Cui, Lan; Yang, Jing; Du, Xi-Wen

2015-01-28

As a promising material for photoelectrical application, MoS2 has attracted extensive attention on its facile synthesis and unique properties. Herein, we explored a novel strategy of laser ablation to synthesize MoS2 fullerene-like nanoparticles (FL-NPs) with stable photoresponse under high temperature. Specifically, we employed a millisecond pulsed laser to ablate the molybdenum target in dimethyl trisulfide gas, and as a result, the molybdenum nanodroplets were ejected from the target and interacted with the highly reactive ambient gas to produce MoS2 FL-NPs. In contrast, the laser ablation in liquid could only produce core-shell nanoparticles. The crucial factors for controlling final nanostructures were found to be laser intensity, cooling rate, and gas reactivity. Finally, the MoS2 FL-NPs were assembled into a simple photoresponse device which exhibited excellent thermal stability, indicating their great potentialities for high-temperature photoelectrical applications.

Monitoring radio-frequency thermal ablation with ultrasound by low frequency acoustic emissions--in vitro and in vivo study.

PubMed

Winkler, Itai; Adam, Dan

2011-05-01

The object of this study was to evaluate the monitoring of thermal ablation therapy by measuring the nonlinear response to ultrasound insonation at the region being treated. Previous reports have shown that during tissue heating, microbubbles are formed. Under the application of ultrasound, these microbubbles may be driven into nonlinear motion that produces acoustic emissions at sub-harmonic frequencies and a general increase of emissions at low frequencies. These low frequency emissions may be used to monitor ablation surgery. In this study, a modified commercial ultrasound system was used for transmitting ultrasound pulses and for recording raw RF-lines from a scan plane in porcine (in vitro) and rabbit (in vivo) livers during radio-frequency ablation (RFA). The transmission pulse was 15 cycles in length at 4 MHz (in vitro) and 3.6 MHz (in vivo). Thermocouples were used for monitoring temperatures during the RFA treatment.In the in vitro experiments, recorded RF signals (A-lines) were segmented, and the total energy was measured at two different frequency bands: at a low frequency band (LFB) of 1-2.5 MHz and at the transmission frequency band (TFB) of 3.5-4.5 MHz. The mean energy at the LFB and at the TFB increased substantially in areas adjacent to the RF needle. These energies also changed abruptly at higher temperatures, thus, producing great variance in the received energy. Mean energies in areas distant from RF needle showed little change and variation during treatment. It was also shown that a 3 dB increase of energy at the low frequency band was typically obtained in regions in which temperature was above 53.3 ± 5° C. Thus, this may help in evaluating regions undergoing hyperthermia. In the in vivo experiments, an imaging algorithm based on measuring the LFB energy was used. The algorithm performs a moving average of the LFB energies measured at segments within the scan plane.Results show that a colored region is formed on the image and that it is

Noninvasive Thermal Ablation of Osteomyelitis-Causing Bacteria using Functionalized Nanoparticles

DTIC Science & Technology

2012-03-01

2008). One alternative approach to antibiotics includes the use of near infrared ( IR ) radiation to thermally kill pathogenic organisms (Kam, 2005...Zharov, 2006). Whereas near IR wavelengths pass harmlessly through the human body, they are known to heat gold nanoshells to high temperatures (>70°C...nanoparticles both alone and complexed with PlyCB (Fig. 8). Task 3. Determine depth of IR radiation penetration and range of thermal damage. (months 11- 15

Tvashtar's Plume

NASA Technical Reports Server (NTRS)

2007-01-01

This dramatic image of Io was taken by the Long Range Reconnaissance Imager (LORRI) on New Horizons at 11:04 Universal Time on February 28, 2007, just about 5 hours after the spacecraft's closest approach to Jupiter. The distance to Io was 2.5 million kilometers (1.5 million miles) and the image is centered at 85 degrees west longitude. At this distance, one LORRI pixel subtends 12 kilometers (7.4 miles) on Io.

This processed image provides the best view yet of the enormous 290-kilometer (180-mile) high plume from the volcano Tvashtar, in the 11 o'clock direction near Io's north pole. The plume was first seen by the Hubble Space Telescope two weeks ago and then by New Horizons on February 26; this image is clearer than the February 26 image because Io was closer to the spacecraft, the plume was more backlit by the Sun, and a longer exposure time (75 milliseconds versus 20 milliseconds) was used. Io's dayside was deliberately overexposed in this picture to image the faint plumes, and the long exposure also provided an excellent view of Io's night side, illuminated by Jupiter. The remarkable filamentary structure in the Tvashtar plume is similar to details glimpsed faintly in 1979 Voyager images of a similar plume produced by Io's volcano Pele. However, no previous image by any spacecraft has shown these mysterious structures so clearly.

The image also shows the much smaller symmetrical fountain of the plume, about 60 kilometers (or 40 miles) high, from the Prometheus volcano in the 9 o'clock direction. The top of a third volcanic plume, from the volcano Masubi, erupts high enough to catch the setting Sun on the night side near the bottom of the image, appearing as an irregular bright patch against Io's Jupiter-lit surface. Several Everest-sized mountains are highlighted by the setting Sun along the terminator, the line between day and night.

This is the last of a handful of LORRI images that New Horizons is sending 'home' during its busy close

Computer modeling of electromagnetic and thermal effects in microwave soft tissue ablation (Invited Paper)

NASA Astrophysics Data System (ADS)

Cronin, Nigel J.; Clegg, Peter J.

2005-04-01

Microwave Endometrial Ablation (MEA) is a technique that can be used for the treatment of abnormal uterine bleeding. The procedure involves sweeping a specially designed microwave applicator throughout the uterine cavity to achieve an ideally uniform depth of tissue necrosis of between 5 and 6mm. We have performed a computer analysis of the MEA procedure in which finite element analysis was used to determine the SAR pattern around the applicator. This was followed by a Green Function based solution of the Bioheat equation to determine the resulting induced temperatures. The method developed is applicable to situations involving a moving microwave source, as used in MEA. The validity of the simulation was verified by measurements in a tissue phantom material using a purpose built applicator and a calibrated pulling device. From the calculated temperatures the depth of necrosis was assessed through integration of the resulting rates of cell death estimated using the Arrhenius equation. The Arrhenius parameters used were derived from published data on BHK cells. Good agreement was seen between the calculated depths of cell necrosis and those found in human in-vivo testing.

Multifunctional magnetic-optical nanoparticle probes for simultaneous detection, separation, and thermal ablation of multiple pathogens.

PubMed

Wang, Chungang; Irudayaraj, Joseph

2010-01-01

Multifunctional nanoparticles possessing magnetization and near-infrared (NIR) absorption have warranted interest due to their significant applications in magnetic resonance imaging, diagnosis, bioseparation, target delivery, and NIR photothermal ablation. Herein, the site-selective assembly of magnetic nanoparticles onto the ends or ends and sides of gold nanorods with different aspect ratios (ARs) to create multifunctional nanorods decorated with varying numbers of magnetic particles is described for the first time. The resulting hybrid nanoparticles are designated as Fe(3)O(4)-Au(rod)-Fe(3)O(4) nanodumbbells and Fe(3)O(4)-Au(rod) necklacelike constructs with tunable optical and magnetic properties, respectively. These hybrid nanomaterials can be used for multiplex detection and separation because of their tunable magnetic and plasmonic functionality. More specifically, Fe(3)O(4)-Au(rod) necklacelike probes of different ARs are utilized for simultaneous optical detection based on their plasmon properties, magnetic separation, and photokilling of multiple pathogens from a single sample at one time. The combined functionalities of the synthesized probes will open up many exciting opportunities in dual imaging for targeted delivery and photothermal therapy.

A 1-MHz 2-D CMUT array for HIFU thermal ablation

NASA Astrophysics Data System (ADS)

Yoon, Hyo-Seon; Vaithilingam, Srikant; Park, Kwan Kyu; Nikoozadeh, Amin; Firouzi, Kamyar; Choe, Jung Woo; Watkins, Ronald D.; Oguz, Huseyin Kagan; Kupnik, Mario; Pauly, Kim Butts; Khuri-Yakub, Pierre

2017-03-01

We developed a fully-populated 2-D capacitive micromachined ultrasonic transducer (CMUT) array for high intensity focused ultrasound (HIFU) treatment. The 2-D CMUT array, which consists of 20 × 20 square CMUT elements with an element-to-element pitch of 1 mm, was designed and fabricated using the thick-buried-oxide (BOX) fabrication process. It was then assembled on a custom interface board that can provide various array configurations depending on the desired applications. In this study, the interface board groups the CMUT array elements into eight channels, based on the phase delay from the element to the targeted focal point at a 20-mm distance from the array surface, which corresponds to an F-number of 1. An 8-channel phase generating system supplies continuous waves with eight different phases to the eight channels of the CMUT array through bias-tees and amplifiers. This array aperture, grouped into eight channels, gives a focusing gain of 6.09 according to field simulation using Field II. Assuming a peak-to-peak pressure of 1 MPa at the surface of the array, our custom temperature simulator predicts successful tissue ablation at the focus. During the measurements, each channel was tuned with a series inductor for an operational frequency of 1 MHz. With a CMUT DC bias of 100 V and a 1-MHz AC input voltage of 55 V, we achieved peak-to-peak output pressures of 173.9 kPa and 568.7 kPa at the array surface and at the focus, respectively. The focusing gain calculated from this measurement is 3.27, which is lower than the simulated gain of 6.09 because of the mutual radiation impedance among the CMUT cells. Further optimization of the operating condition of this array and design improvements for reducing the effect of mutual radiation impedance are currently on-going.

Percutaneous Thermal Ablation with Ultrasound Guidance. Fusion Imaging Guidance to Improve Conspicuity of Liver Metastasis

SciTech Connect

Hakime, Antoine, E-mail: thakime@yahoo.com; Yevich, Steven; Tselikas, Lambros

PurposeTo assess whether fusion imaging-guided percutaneous microwave ablation (MWA) can improve visibility and targeting of liver metastasis that were deemed inconspicuous on ultrasound (US).Materials and MethodsMWA of liver metastasis not judged conspicuous enough on US was performed under CT/US fusion imaging guidance. The conspicuity before and after the fusion imaging was graded on a five-point scale, and significance was assessed by Wilcoxon test. Technical success, procedure time, and procedure-related complications were evaluated.ResultsA total of 35 patients with 40 liver metastases (mean size 1.3 ± 0.4 cm) were enrolled. Image fusion improved conspicuity sufficiently to allow fusion-targeted MWA in 33 patients. The time requiredmore » for image fusion processing and tumors’ identification averaged 10 ± 2.1 min (range 5–14). Initial conspicuity on US by inclusion criteria was 1.2 ± 0.4 (range 0–2), while conspicuity after localization on fusion imaging was 3.5 ± 1 (range 1–5, p < 0.001). Technical success rate was 83% (33/40) in intention-to-treat analysis and 100% in analysis of treated tumors. There were no major procedure-related complications.ConclusionsFusion imaging broadens the scope of US-guided MWA to metastasis lacking adequate conspicuity on conventional US. Fusion imaging is an effective tool to increase the conspicuity of liver metastases that were initially deemed non visualizable on conventional US imaging.« less

Hyaluronic Acid Gel Injection to Prevent Thermal Injury of Adjacent Gastrointestinal Tract during Percutaneous Liver Radiofrequency Ablation

SciTech Connect

Hasegawa, Takaaki, E-mail: hasegawat@clin.medic.mie-u.ac.jp; Takaki, Haruyuki; Miyagi, Hideki

2013-08-01

This study evaluated the safety, feasibility, and clinical utility of hyaluronic acid gel injection to separate the gastrointestinal tract from the tumor during liver radiofrequency ablation (RFA). Eleven patients with liver tumors measuring 0.9-3.5 cm (mean {+-} standard deviation, 2.1 {+-} 0.8 cm) that were adjacent to the gastrointestinal tracts received RFA after the mixture of hyaluronic acid gel and contrast material (volume, 26.4 {+-} 14.5 mL; range, 10-60 mL) was injected between the tumor and the gastrointestinal tract under computed tomographic-fluoroscopic guidance. Each tumor was separated from the gastrointestinal tract by 1.0-1.5 cm (distance, 1.2 {+-} 0.2 cm) aftermore » injection of hyaluronic acid gel, and subsequent RFA was performed without any complications in all patients. Although tumor enhancement disappeared in all patients, local tumor progression was found in a patient (9.1 %, 1 of 11) during the follow-up of 5.5 {+-} 3.2 months (range, 0.4-9.9 months). In conclusion, hyaluronic acid gel injection is a safe and useful technique to avoid thermal injury of the adjacent gastrointestinal tract during liver RFA.« less

Radiofrequency Thermal Ablation versus Bipolar Electrocautery for the Treatment of Inferior Turbinate Hypertrophy: Comparison of Efficacy and Postoperative Morbidity

PubMed Central

Uluyol, Sinan; Karakaya, Nermin Erdas; Gur, Mehmet Hafit; Kilicaslan, Saffet; Kantarcioglu, Esin Ozlem; Yagiz, Ozlem; Arslan, Ilker Burak

2015-01-01

Introduction Numerous surgical methods are used to treat nasal obstruction due to inferior turbinate hypertrophy. The primary goal of the therapy is to maximize the nasal airway for as extended a period of time as possible while minimizing therapeutic complications. Objectives The aim of this study was to assess the effects of radiofrequency thermal ablation (RFTA) and bipolar electrocautery (BEC) on the removal of nasal obstruction in patients with inferior turbinate hypertrophy and on nasal mucociliary clearance (MCC). Patients in both groups were also evaluated in terms of postoperative morbidity. Methods We compared the outcomes of two groups of patients: those treated with RFTA (n = 23) and those who underwent BEC (n = 20). Nasal obstruction was graded using a visual analog scale (VAS) and MCC was measured using a saccharin clearance test. Both measurements were performed before and 2 months after treatment. Results Pre- and postoperative VAS scores showed significant improvement for both groups. However, MCC results did not significantly differ between two groups. Neither edema nor crust formation persisted for more than 1 week in any patients. Conclusion Submucosal cauterization with preservation of the nasal mucosa and periosteum is as effective and safe as RFTA and should be considered when planning inferior turbinate interventions. PMID:26722337

Fast Conformal Thermal Ablation in the Prostate with Transurethral Multi-Sectored Ultrasound Devices and MR Guidance

NASA Astrophysics Data System (ADS)

Kinsey, Adam M.; Diederich, Chris J.; Nau, William H.; Ross, Anthony B.; Pauly, Kim Butts; Rieke, Viola; Sommer, Graham

2007-05-01

Transurethral ultrasound applicators incorporating an array of multisectored tubular transducers were evaluated in theoretical simulations and in vivo canine prostates under MR guidance as a method for fast, conformal thermal therapy of the prostate. Comprehensive simulations with a biothermal model investigated the effect on lesion creation of sector size, perfusion, treatment time, rectal cooling, prostate target dimensions, and feedback controller parameters (maximum temperature, pilot points at boundary, update times). In vivo canine prostates (n = 4) were treated with trisectored ultrasound transducers (3 mm OD) under MR temperature monitoring to contour the ablation zone (>52 C for 1-2 min) to the boundary of the prostate. Contiguous thermal lesions extended 2 cm in radius from the urethra in less than 15 min and independent sector control simultaneously allowed for conformal treatment in the angular dimension. Experiments investigated sequential translation of the transducer assembly within the catheter for tailoring heat treatments to different partitions in the prostate (base, apex) without changing the initial setup. This treatment method offered greater lesion shape control in three dimensions and slightly lengthened the overall treatment time. The MR temperature images correlated with post-treatment histology and accurately controlled the heating to the target boundary. MR-based control of transurethral ultrasound devices appeared more practical with multisectored transducers compared to rotating curvilinear and planar applicators due to less stringent requirements on spatial and temporal MR parameters. This study demonstrated the applicability of these devices in the prostate for anterior-lateral BPH treatment, and whole gland or quadrant target volumes for cancer treatment.

Thermal modeling for pulsed radiofrequency ablation: analytical study based on hyperbolic heat conduction.

PubMed

López Molina, Juan A; Rivera, María J; Trujillo, Macarena; Berjano, Enrique J

2009-04-01

The objectives of this study were to model the temperature progress of a pulsed radiofrequency (RF) power during RF heating of biological tissue, and to employ the hyperbolic heat transfer equation (HHTE), which takes the thermal wave behavior into account, and compare the results to those obtained using the heat transfer equation based on Fourier theory (FHTE). A theoretical model was built based on an active spherical electrode completely embedded in the biological tissue, after which HHTE and FHTE were analytically solved. We found three typical waveforms for the temperature progress depending on the relations between the dimensionless duration of the RF pulse delta(a) and the expression square root of lambda(rho-1), with lambda as the dimensionless thermal relaxation time of the tissue and rho as the dimensionless position. In the case of a unique RF pulse, the temperature at any location was the result of the overlapping of two different heat sources delayed for a duration delta(a) (each heat source being produced by a RF pulse of limitless duration). The most remarkable feature in the HHTE analytical solution was the presence of temperature peaks traveling through the medium at a finite speed. These peaks not only occurred during the RF power switch-on period but also during switch off. Finally, a physical explanation for these temperature peaks is proposed based on the interaction of forward and reverse thermal waves. All-purpose analytical solutions for FHTE and HHTE were obtained during pulsed RF heating of biological tissues, which could be used for any value of pulsing frequency and duty cycle.

Feasibility of Real-Time Intraprocedural Temperature Control during Bone Metastasis Thermal Microwave Ablation: A Bicentric Retrospective Study.

PubMed

Kastler, Adrian; Krainik, Alexandre; Sakhri, Linda; Mousseau, Mireille; Kastler, Bruno

2017-03-01

To evaluate feasibility of using a thermocouple for temperature monitoring during microwave (MW) ablation of metastatic bone disease. This retrospective study comprised 16 patients (8 men with mean age 63 y and 8 women with mean age 59 y) with 18 bone metastases treated with MW ablation using a thermocouple between March 2012 and October 2015. The mean maximum tumor size was 29.5 mm. MW ablation power was set between 15 W and 40 W and applied for 1-6 minutes. Thermocouple placements were as follows: epidural space (n = 7 cases), nerve roots (n = 9 cases), pleura (n = 1), and pericardium (n = 1). The procedure was considered technically successful when the MW and the thermocouple probes were accurately placed and thermoablation was initiated. Clinical success was defined as a 50% visual analog scale score decrease at 1 month as assessed by the operators. Mean MW ablation time was 4.3 minutes with a mean energy of 30 W. Procedural success was 100%. In 16 cases with neural structure monitoring, temperature did not increase > 43°C. In 8 cases, MW ablation had to be discontinued because of temperature reaching 42°C. Efficacy of the procedure in regard to pain was achieved in 17 of 18 ablation sessions at 1 month. Use of a thermocouple during bone MW ablation is a feasible technique and may be a potentially useful tool to help avoid nontarget ablation surrounding tumors. Copyright © 2016 SIR. Published by Elsevier Inc. All rights reserved.

Development of 3D Woven Ablative Thermal Protection Systems (TPS) for NASA Spacecraft

NASA Technical Reports Server (NTRS)

Feldman, Jay D.; Ellerby, Don; Stackpoole, Mairead; Peterson, Keith; Venkatapathy, Ethiraj

2015-01-01

The development of a new class of thermal protection system (TPS) materials known as 3D Woven TPS led by the Entry Systems and Technology Division of NASA Ames Research Center (ARC) will be discussed. This effort utilizes 3D weaving and resin infusion technologies to produce heat shield materials that are engineered and optimized for specific missions and requirements. A wide range of architectures and compositions have been produced and preliminarily tested to prove the viability and tailorability of the 3D weaving approach to TPS.

Three-year outcome of the Halt trial: a prospective analysis of radiofrequency volumetric thermal ablation of myomas.

PubMed

Berman, Jay M; Guido, Richard S; Garza Leal, José Gerardo; Pemueller, Rodolfo Robles; Whaley, Fredrick S; Chudnoff, Scott G

2014-01-01

To analyze the clinical success of radiofrequency volumetric thermal ablation (RFVTA) at 3-year follow-up in terms of subject responses to validated questionnaires and surgical repeat intervention to treat myomas. Prospective follow-up of patients for 36 months after treatment in a multicenter international trial of outpatient, laparoscopic ultrasound-guided RFVTA of symptomatic uterine myomas (Canadian Task Force classification II-1). University hospitals and private surgical centers. One hundred thirty-five premenopausal women (mean [SD] age, 42.5 [4.6] years; body mass index, 30.5 [6.1]) with symptomatic uterine myomas and objectively confirmed heavy menstrual bleeding (≥ 160 to ≤ 500 mL). Laparoscopic ultrasound-guided RFVTA. One hundred four participants were followed prospectively for 36 months after treatment of myomas via RFVTA. For 104 evaluable participants with 36-month data, change in mean (SD) symptom severity from baseline (60.2 [18.8]) to 36 months was -32.6 (95% confidence interval, -37.5 to -27.8; p < .001). Health-related quality of life also was improved, from the baseline value of 39.2 (19.2) to 38.6 (95% confidence interval, 33.3 to 43.9; p < .001) at 36 months. Patient-reported Uterine Fibroid Symptom and Health-Related Quality of Life questionnaire subscores demonstrated statistically significant improvement from baseline to 36 months in all categories (Concern, Activities, Energy/Mood, Control, Self-consciousness, and Sexual Function) (p < .001). For the 104 participants with 36-month data, mean state of health scores (EuroQOL-5D Health State Index) improved from a baseline value of 71.0 (19.3) to 86.2 (11.7) at 36 months. The cumulative repeat intervention rate of 11% (14 of 135 participants) at 36 months was well below the possible 25% maximum expected at the beginning of the trial. RFVTA of uterine myomas resulted in sustained relief from myoma symptoms and continued improvement in health-related quality of life through 36 months

Modeling of Laser Vaporization and Plume Chemistry in a Boron Nitride Nanotube Production Rig

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.; Fay, Catharine C.

2012-01-01

Flow in a pressurized, vapor condensation (PVC) boron nitride nanotube (BNNT) production rig is modeled. A laser provides a thermal energy source to the tip of a boron ber bundle in a high pressure nitrogen chamber causing a plume of boron-rich gas to rise. The buoyancy driven flow is modeled as a mixture of thermally perfect gases (B, B2, N, N2, BN) in either thermochemical equilibrium or chemical nonequilibrium assuming steady-state melt and vaporization from a 1 mm radius spot at the axis of an axisymmetric chamber. The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high temperature environment (T > 4400K) for elevated pressures within 1 mm of the surface sufficient to dissociate molecular nitrogen and form BN at the base of the plume. Modifications to Program LAURA, a finite-volume based solver for hypersonic flows including coupled radiation and ablation, are described to enable this simulation. Simulations indicate that high pressure synthesis conditions enable formation of BN vapor in the plume that may serve to enhance formation of exceptionally long nanotubes in the PVC process.

Linearly chirped fiber Bragg grating response to thermal gradient: from bench tests to the real-time assessment during in vivo laser ablations of biological tissue.

PubMed

Saccomandi, Paola; Varalda, Ambra; Gassino, Riccardo; Tosi, Daniele; Massaroni, Carlo; Caponero, Michele A; Pop, Raoul; Korganbayev, Sanzhar; Perrone, Guido; Diana, Michele; Vallan, Alberto; Costamagna, Guido; Marescaux, Jacques; Schena, Emiliano

2017-09-01

The response of a fiber optic sensor [linearly chirped fiber Bragg grating (LCFBG)] to a linear thermal gradient applied on its sensing length (i.e., 1.5 cm) has been investigated. After these bench tests, we assessed their feasibility for temperature monitoring during thermal tumor treatment. In particular, we performed experiments during ex vivo laser ablation (LA) in pig liver and in vivo thermal ablation in animal models (pigs). We investigated the following: (i) the relationship between the full width at half maximum of the LCFBG spectrum and the temperature difference among the extremities of the LCFBG and (ii) the relationship between the mean spectrum wavelength and the mean temperature acting on the LCFBG sensing area. These relationships showed a linear trend during both bench tests and LA in animal models. Thermal sensitivity was significant although different values were found with regards to bench tests and animal experiments. The linear trend and significant sensitivity allow hypothesizing a future use of this kind of sensor to monitor both temperature gradient and mean temperature within a tissue undergoing thermal treatment. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Modeling of Interactions of Ablated Plumes

DTIC Science & Technology

2008-02-01

code was tested and verified using the Sedov-Taylor explosion problem 24. The grid 300 x 300 is used so as the single code run takes 30 minutes in a...still air and b) temperature contours along with the vector field for 20 km at t-10ps. 9 Final report AFOSR FA9550-07-1-0457 February 2008 0960014 09 C ow...ia Figue9FrainoIeodr shok wves a-)pesr otus0 )~22,bt4F,adetJ n d) het trnsferat te TPSw9PS 00 As 10 04 J. ’ Figure 9:Formation of secondary shock

Harmonic motion imaging for focused ultrasound (HMIFU): a fully integrated technique for sonication and monitoring of thermal ablation in tissues.

PubMed

Maleke, C; Konofagou, E E

2008-03-21

FUS (focused ultrasound), or HIFU (high-intensity-focused ultrasound) therapy, a minimally or non-invasive procedure that uses ultrasound to generate thermal necrosis, has been proven successful in several clinical applications. This paper discusses a method for monitoring thermal treatment at different sonication durations (10 s, 20 s and 30 s) using the amplitude-modulated (AM) harmonic motion imaging for focused ultrasound (HMIFU) technique in bovine liver samples in vitro. The feasibility of HMI for characterizing mechanical tissue properties has previously been demonstrated. Here, a confocal transducer, combining a 4.68 MHz therapy (FUS) and a 7.5 MHz diagnostic (pulse-echo) transducer, was used. The therapy transducer was driven by a low-frequency AM continuous signal at 25 Hz, producing a stable harmonic radiation force oscillating at the modulation frequency. A pulser/receiver was used to drive the pulse-echo transducer at a pulse repetition frequency (PRF) of 5.4 kHz. Radio-frequency (RF) signals were acquired using a standard pulse-echo technique. The temperature near the ablation region was simultaneously monitored. Both RF signals and temperature measurements were obtained before, during and after sonication. The resulting axial tissue displacement was estimated using one-dimensional cross correlation. When temperature at the focal zone was above 48 degrees C during heating, the coagulation necrosis occurred and tissue damage was irreversible. The HMI displacement profiles in relation to the temperature and sonication durations were analyzed. At the beginning of heating, the temperature at the focus increased sharply, while the tissue stiffness decreased resulting in higher HMI displacements. This was confirmed by an increase of 0.8 microm degrees C(-1)(r=0.93, p<.005). After sustained heating, the tissue became irreversibly stiffer, followed by an associated decrease in the HMI displacement (-0.79 microm degrees C(-1), r=-0.92, p<0.001). Repeated

Nonequilibrium Ablation of Phenolic Impregnated Carbon Ablator

NASA Technical Reports Server (NTRS)

Milos, Frank S.; Chen, Yih K.; Gokcen, Tahir

2012-01-01

In previous work, an equilibrium ablation and thermal response model for Phenolic Impregnated Carbon Ablator was developed. In general, over a wide range of test conditions, model predictions compared well with arcjet data for surface recession, surface temperature, in-depth temperature at multiple thermocouples, and char depth. In this work, additional arcjet tests were conducted at stagnation conditions down to 40 W/sq cm and 1.6 kPa. The new data suggest that nonequilibrium effects become important for ablation predictions at heat flux or pressure below about 80 W/sq cm or 10 kPa, respectively. Modifications to the ablation model to account for nonequilibrium effects are investigated. Predictions of the equilibrium and nonequilibrium models are compared with the arcjet data.

Space shuttle main engine plume radiation model

NASA Technical Reports Server (NTRS)

Reardon, J. E.; Lee, Y. C.

1978-01-01

The methods are described which are used in predicting the thermal radiation received by space shuttles, from the plumes of the main engines. Radiation to representative surface locations were predicted using the NASA gaseous plume radiation GASRAD program. The plume model is used with the radiative view factor (RAVFAC) program to predict sea level radiation at specified body points. The GASRAD program is described along with the predictions. The RAVFAC model is also discussed.

Tm:fiber laser ablation with real-time temperature monitoring for minimizing collateral thermal damage: ex vivo dosimetry for ovine brain.

PubMed

Tunc, Burcu; Gulsoy, Murat

2013-01-01

The thermal damage of the surrounding tissue can be an unwanted result of continuous-wave laser irradiations. In order to propose an effective alternative to conventional surgical techniques, photothermal damage must be taken under control by a detailed dose study. Real-time temperature monitoring can be also an effective way to get rid of these negative effects. The aim of the present study is to investigate the potential of a new laser-thermoprobe, which consists of a continuous-wave 1,940-nm Tm:fiber laser and a thermocouple measurement system for brain surgery in an ex vivo study. A laser-thermoprobe was designed for using the near-by tissue temperature as a real-time reference for the applicator. Fresh lamb brain tissues were used for experiments. 320 laser shots were performed on both cortical and subcortical tissue. The relationship between laser parameters, temperature changes, and ablation (removal of tissue) efficiency was determined. The correlation between rate of temperature change and ablation efficiency was calculated. Laser-thermoprobe leads us to understand the basic laser-tissue interaction mechanism in a very cheap and easy way, without making a change in the experimental design. It was also shown that the ablation and coagulation (thermally irreversible damage) diameters could be predicted, and carbonization can be avoided by temperature monitoring. Copyright © 2013 Wiley Periodicals, Inc.

Thermal ablation system using high intensity focused ultrasound (HIFU) and guided by MRI

NASA Astrophysics Data System (ADS)

Damianou, C.; Ioannides, K.; HadjiSavas, V.; Milonas, N.; Couppis, A.; Iosif, D.; Komodromos, M.; Vrionides, F.

2009-04-01

In this paper magnetic resonance imaging (MRI) is investigated for monitoring lesions created by high intensity focused ultrasound (HIFU) in kidney, liver and brain in vitro and in vivo. Spherically focused transducers of 4 cm diameter, focusing at 10 cm and operating at 1 and 4 MHz were used. An MRI compatible positioning device was developed in order to scan the HIFU transducer. The MRI compatibility of the system was successfully demonstrated in a clinical high-field MRI scanner. The ability of the positioning device to accurately move the transducer thus creating discrete and overlapping lesions in biological tissue was tested successfully. A simple, cost effective, portable positioning device has been developed which can be used in virtually any clinical MRI scanner since it can be sited on the scanner's table. The propagation of HIFU can use either a lateral or superior-inferior approach. Both T1-w FSE and T2-w FSE imaged successfully lesions in kidney and liver. T1-w FSE and T2-w FSE and FLAIR shows better anatomical details in brain than T1-w FSE, but with T1-w FSE the contrast between lesion and brain is higher for both thermal and bubbly lesion. With this system we were able to create large lesions (by producing overlapping lesions). The length of the lesions in vivo brain was much higher than the length in vitro, proving that the penetration in the in vitro brain is limited by reflection due to trapped bubbles in the blood vessels.

Cardiac shear-wave elastography using a transesophageal transducer: application to the mapping of thermal lesions in ultrasound transesophageal cardiac ablation

NASA Astrophysics Data System (ADS)

Kwiecinski, Wojciech; Bessière, Francis; Constanciel Colas, Elodie; Apoutou N'Djin, W.; Tanter, Mickaël; Lafon, Cyril; Pernot, Mathieu

2015-10-01

Heart rhythm disorders, such as atrial fibrillation or ventricular tachycardia can be treated by catheter-based thermal ablation. However, clinically available systems based on radio-frequency or cryothermal ablation suffer from limited energy penetration and the lack of lesion’s extent monitoring. An ultrasound-guided transesophageal device has recently successfully been used to perform High-Intensity Focused Ultrasound (HIFU) ablation in targeted regions of the heart in vivo. In this study we investigate the feasibility of a dual therapy and imaging approach on the same transesophageal device. We demonstrate in vivo that quantitative cardiac shear-wave elastography (SWE) can be performed with the device and we show on ex vivo samples that transesophageal SWE can map the extent of the HIFU lesions. First, SWE was validated with the transesophageal endoscope in one sheep in vivo. The stiffness of normal atrial and ventricular tissues has been assessed during the cardiac cycle (n=11 ) and mapped (n= 7 ). Second, HIFU ablation has been performed with the therapy-imaging transesophageal device in ex vivo chicken breast samples (n  =  3), then atrial (left, n= 2 ) and ventricular (left n=1 , right n=1 ) porcine heart tissues. SWE provided stiffness maps of the tissues before and after ablation. Areas of the lesions were obtained by tissue color change with gross pathology and compared to SWE. During the cardiac cycle stiffness varied from 0.5   ±   0.1 kPa to 6.0   ±   0.3 kPa in the atrium and from 1.3   ±   0.3 kPa to 13.5   ±   9.1 kPa in the ventricles. The thermal lesions were visible on all SWE maps performed after ablation. Shear modulus of the ablated zones increased to 16.3   ±   5.5 kPa (versus 4.4   ±   1.6 kPa before ablation) in the chicken breast, to 30.3   ±   10.3 kPa (versus 12.2   ±   4.3 kPa) in the atria and to 73.8   ±   13

Cardiac shear-wave elastography using a transesophageal transducer: application to the mapping of thermal lesions in ultrasound transesophageal cardiac ablation.

PubMed

Kwiecinski, Wojciech; Bessière, Francis; Colas, Elodie Constanciel; N'Djin, W Apoutou; Tanter, Mickaël; Lafon, Cyril; Pernot, Mathieu

2015-10-21

Heart rhythm disorders, such as atrial fibrillation or ventricular tachycardia can be treated by catheter-based thermal ablation. However, clinically available systems based on radio-frequency or cryothermal ablation suffer from limited energy penetration and the lack of lesion's extent monitoring. An ultrasound-guided transesophageal device has recently successfully been used to perform High-Intensity Focused Ultrasound (HIFU) ablation in targeted regions of the heart in vivo. In this study we investigate the feasibility of a dual therapy and imaging approach on the same transesophageal device. We demonstrate in vivo that quantitative cardiac shear-wave elastography (SWE) can be performed with the device and we show on ex vivo samples that transesophageal SWE can map the extent of the HIFU lesions. First, SWE was validated with the transesophageal endoscope in one sheep in vivo. The stiffness of normal atrial and ventricular tissues has been assessed during the cardiac cycle (n = 11) and mapped (n = 7). Second, HIFU ablation has been performed with the therapy-imaging transesophageal device in ex vivo chicken breast samples (n  =  3), then atrial (left, n = 2) and ventricular (left n = 1, right n = 1) porcine heart tissues. SWE provided stiffness maps of the tissues before and after ablation. Areas of the lesions were obtained by tissue color change with gross pathology and compared to SWE. During the cardiac cycle stiffness varied from 0.5   ±   0.1 kPa to 6.0   ±   0.3 kPa in the atrium and from 1.3   ±   0.3 kPa to 13.5   ±   9.1 kPa in the ventricles. The thermal lesions were visible on all SWE maps performed after ablation. Shear modulus of the ablated zones increased to 16.3   ±   5.5 kPa (versus 4.4   ±   1.6 kPa before ablation) in the chicken breast, to 30.3   ±   10.3 kPa (versus 12.2   ±   4.3 kPa) in the atria and to 73.8�

TPS Ablator Technologies for Interplanetary Spacecraft

NASA Technical Reports Server (NTRS)

Curry, Donald M.

2004-01-01

This slide presentation reviews the status of Thermal Protection System (TPS) Ablator technologies and the preparation for use in interplanetary spacecraft. NASA does not have adequate TPS ablatives and sufficient selection for planned missions. It includes a comparison of shuttle and interplanetary TPS requirements, the status of mainline TPS charring ablator materials, a summary of JSC SBIR accomplishments in developing advanced charring ablators and the benefits of SBIR Ablator/fabrication technology.

Ultrasound-guided laser thermal ablation in the treatment of autonomous hyperfunctioning thyroid nodules and compressive nontoxic nodular goiter.

PubMed

Spiezia, Stefano; Vitale, Giovanni; Di Somma, Carolina; Pio Assanti, Angelo; Ciccarelli, Antonio; Lombardi, Gaetano; Colao, Annamaria

2003-10-01

Percutaneous laser thermal ablation (LTA) has been applied in several tumors. In this study we evaluated the safety and long-term efficacy of LTA in the treatment of benign thyroid nodules. Seven patients with autonomous hyperfunctioning thyroid nodule (group A) and five patients with compressive nodular goiter (group B) were treated with LTA. Up to three needles were positioned centrally in the thyroid nodule and laser fiber was placed in the lumen of the needle. Laser illumination was performed reaching a maximal energy deposition of 1800 J per fiber. Thyroid nodule volume, endocrinologic, and clinical evaluation were performed at baseline, 3, and 12 months after the treatment. Scintigraphy was performed at diagnosis and 12 months after the first session in group A. In group A, mean thyroid volume decreased from 3.15 +/- 1.26 mL to 0.83 +/- 0.49 mL (p < 0.001) after 12 months. The treatment induced disappearance of clinical signs and symptoms related to hyperthyroidism; normalization of free triiodothyronine (FT(3)), free thyroxine (FT(4)), and thyrotropin (TSH) serum levels and recovery of extranodular uptake at scintiscan. In group B, mean thyroid volume decreased from 11.14 +/- 4.99 mL to 3.73 +/- 1.47 mL (p < 0.01) after 12 months. Pressure symptoms in the neck, difficulty in swallowing and tracheal displacement improved in all patients. The treatment was well tolerated in both groups of patients. LTA appears to be a valid and safe alternative approach in the treatment of benign thyroid nodules.

Stereotactic robot-assisted MRI-guided laser thermal ablation of radiation necrosis in the posterior cranial fossa: technical note.

PubMed

Chan, Alvin Y; Tran, Diem Kieu T; Gill, Amandip S; Hsu, Frank P K; Vadera, Sumeet

2016-10-01

Laser interstitial thermal therapy (LITT) is a minimally invasive procedure used to treat a variety of intracranial lesions. Utilization of robotic assistance with stereotactic procedures has gained attention due to potential for advantages over conventional techniques. The authors report the first case in which robot-assisted MRI-guided LITT was used to treat radiation necrosis in the posterior fossa, specifically within the cerebellar peduncle. The use of a stereotactic robot allowed the surgeon to perform LITT using a trajectory that would be extremely difficult with conventional arc-based techniques. A 60-year-old man presented with facial weakness and brainstem symptoms consistent with radiation necrosis. He had a history of anaplastic astrocytoma that was treated with CyberKnife radiosurgery 1 year prior to presentation, and he did well for 11 months until his symptoms recurred. The location and form of the lesion precluded excision but made the patient a suitable candidate for LITT. The location and configuration of the lesion required a trajectory for LITT that was too low for arc-based stereotactic navigation, and thus the ROSA robot (Medtech) was used. Using preoperative MRI acquisitions, the lesion in the posterior fossa was targeted. Bone fiducials were used to improve accuracy in registration, and the authors obtained an intraoperative CT image that was then fused with the MR image by the ROSA robot. They placed the laser applicator and then ablated the lesion under real-time MR thermometry. There were no complications, and the patient tolerated the procedure well. Postoperative 2-month MRI showed complete resolution of the lesion, and the patient had some improvement in symptoms.

Gold nanorods coupled with upconverting nanophosphors for targeted thermal ablation and imaging of bladder cancer cells (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cho, Suehyun K.; Su, Lih-Jen; Flaig, Thomas W.; Park, Wounjhang

2016-09-01

NaYF4:Yb3+,Er3+ upconverting nanophosphors (UCNPs) are robust and stable nanoparticles that absorb near-infrared (NIR) photons and emit green and red visible photons through energy transfer upconversion. This mechanism provides UCNPs several advantages as a bioimaging agent over traditional fluorescence imaging agent in that NIR excitation allows high-contrast imaging without autofluorescence and that they can be used for deep-tissue imaging. However, additional surface modification of UCNPs is necessary for them to be biocompatible. We use an amphiphilic polymer (poly(maleic anhydride-alt-octadecene) (PMAO) and a hetero-functional polyethylene glycol with amine and thiol ends (NH2-PEG-SH)) to make the UCNPs water-soluble. This reaction yields a carboxylic group that allows functionalization with anti-epidermal growth factor receptor (aEGFR), which provides specific binding of UCNPs to EGFR-expressing bladder cancer cells. Additionally, the thiol ends of the PEGylated UCNPs are able to bind with gold nanorods (AuNRs) to create UCNP-AuNR complexes. The localized surface plasmon of the AuNR then allow localized heating of HTB9 bladder cancer cells, enabling in situ cell killing upon detection by UCNP fluorescence. Here, we report a successful synthesis, surface modification and conjugation of aEGFR functionalized UCNP-AuNR complexes and in vitro imaging and thermal ablation studies using them. Synthesis and surface modification of UCNP-AuNR complexes are confirmed by electron microscopy. Then, a combination of brightfield, NIR confocal fluorescence, and darkfield microscopy on the UCNP-AuNR treated bladder cancer cells revealed successful cancer targeting and imaging capabilities of the complex. Finally, cell viability assay showed that NIR irradiation of UCNP-AuNR conjugated cells resulted highly selective cell killing.

Spectroscopic diagnostics of plume rebound and shockwave dynamics of confined aluminum laser plasma plumes

SciTech Connect

Yeates, P.; Kennedy, E. T.; School of Physical Sciences, Dublin City University

2011-06-15

Generation and expansion dynamics of aluminum laser plasma plumes generated between parallel plates of varying separation ({Delta}Z = 2.0, 3.2, 4.0, and 5.6 mm), which confined plume expansion normal to the ablation surface, were diagnosed. Space and time resolved visible emission spectroscopy in the spectral range {lambda} = 355-470 nm and time gated visible imaging were employed to record emission spectra and plume dynamics. Space and time resolved profiles of N{sub e} (the electron density), T{sub e} (the electron temperature), and T{sub ionz} (the ionization temperature) were compared for different positions in the plasma plume. Significant modifications of the profilesmore » of the above parameters were observed for plasma-surface collisions at the inner surface of the front plate, which formed a barrier to the free expansion of the plasma plume generated by the laser light on the surface of the back plate. Shockwave generation at the collision interface resulted in delayed compression of the low-density plasma plume near the inner ablation surface, at late stages in the plasma history. Upon exiting the cavity formed by the two plates, through an aperture in the front plate, the plasma plume underwent a second phase of free expansion.« less

Thermal performance of 625-kg/cu m elastomeric ablative materials on spherically blunted 0.44-radian cones

NASA Technical Reports Server (NTRS)

Champman, A. J.

1972-01-01

Spherically blunted 0.44-radian (25 deg) half-angle conical models coated with elastomeric ablative materials were tested in supersonic arc-heated wind tunnels to evaluate performance of the ablators over a range of conditions typical of lifting entry. Four test conditions were combinations of stagnation point-heat transfer rates of 2.3 and 4.5 MW/m2 and stagnation pressures of 20 and 2kN/m2. Afterbody values of heat transfer rate and pressure were 0.05 to 0.20 of stagnation point values. Stagnation enthalpy varied from 4.4 to 25 MJ/kg (1900 to 11000 Btu/lbm) and free-stream Mach number was in a range from 3.5 to 4. Ablative materials retained the spherical nose shape throughout tests at the lower heat transfer level, but receded, assuming a flattened nose shape, during tests at the high heat transfer level. The residue layer that formed on the conical after-body was weak, friable, and extensively cracked. The reference ablative material, which contained phenolic microspheres, generally retained the conical shape on the model afterbody. However, a modified ablator, in which phenolic microspheres were replaced with silica microspheres, deformed and separated from the undegraded material, and thereby produced a very uneven surface. Substrate temperatures and ablator recession were in good agreement with values computed by a numerical analysis.

Space Shuttle Plume and Plume Impingement Study

NASA Technical Reports Server (NTRS)

Tevepaugh, J. A.; Penny, M. M.

1977-01-01

The extent of the influence of the propulsion system exhaust plumes on the vehicle performance and control characteristics is a complex function of vehicle geometry, propulsion system geometry, engine operating conditions and vehicle flight trajectory were investigated. Analytical support of the plume technology test program was directed at the two latter problem areas: (1) definition of the full-scale exhaust plume characteristics, (2) application of appropriate similarity parameters; and (3) analysis of wind tunnel test data. Verification of the two-phase plume and plume impingement models was directed toward the definition of the full-scale exhaust plume characteristics and the separation motor impingement problem.

Risk Factors for Bile Duct Injury After Percutaneous Thermal Ablation of Malignant Liver Tumors: A Retrospective Case-Control Study.

PubMed

Lin, Man-Xia; Ye, Jie-Yi; Tian, Wen-Shuo; Xu, Ming; Zhuang, Bo-Wen; Lu, Ming-De; Xie, Xiao-Yan; Kuang, Ming

2017-04-01

Bile duct injury after ablation of malignant liver tumors (MLTs) was not unusual and should be avoided. However, few studies have focused on evaluating the risk factors for intrahepatic bile duct injury. To evaluate the risk factors for intrahepatic bile duct injury after ablation of MLTs and to evaluate the minimum safe distance for ablating tumors abutting bile ducts. Sixty-five patients with intrahepatic bile duct injury after ablation of MLTs, and 65 controls were recruited. Risk factors for intrahepatic bile duct injury were analyzed. Tumor location was recorded as ≤5 mm (group A), 5-10 mm (group B), and >10 mm (group C) from the right/left main duct or segmental bile duct. Ascites history (P < 0.001), TACE treatment history (P = 0.025), intrahepatic bile duct dilatation before ablation (P < 0.001), and tumor location (P = 0.000) were identified as significant risk factors for intrahepatic bile duct injury. Significant differences in the risk of intrahepatic bile duct injury were found between groups B and C (P = 0.000), but not between groups A and B (P = 0.751). Ascites history (P = 0.002) and tumor location (P < 0.001) were independent predictors with the OR (95 % confidence interval) of 39.31(3.95-391.69) and 16.56 (5.87-46.71), respectively. Bile duct injury after ablation of MLTs was the result of local treatment-related factors combined with the patients' general condition. The minimum safe distance for ablation of tumor abutting a bile duct was 10 mm.

Temperature and heat flux datasets of a complex object in a fire plume for the validation of fire and thermal response codes.

SciTech Connect

Jernigan, Dann A.; Blanchat, Thomas K.

It is necessary to improve understanding and develop temporally- and spatially-resolved integral scale validation data of the heat flux incident to a complex object in addition to measuring the thermal response of said object located within the fire plume for the validation of the SIERRA/FUEGO/SYRINX fire and SIERRA/CALORE codes. To meet this objective, a complex calorimeter with sufficient instrumentation to allow validation of the coupling between FUEGO/SYRINX/CALORE has been designed, fabricated, and tested in the Fire Laboratory for Accreditation of Models and Experiments (FLAME) facility. Validation experiments are specifically designed for direct comparison with the computational predictions. Making meaningful comparisonmore » between the computational and experimental results requires careful characterization and control of the experimental features or parameters used as inputs into the computational model. Validation experiments must be designed to capture the essential physical phenomena, including all relevant initial and boundary conditions. This report presents the data validation steps and processes, the results of the penlight radiant heat experiments (for the purpose of validating the CALORE heat transfer modeling of the complex calorimeter), and the results of the fire tests in FLAME.« less

Transmural Ultrasound Imaging of Thermal Lesion and Action Potential Changes in Perfused Canine Cardiac Wedge Preparations by High Intensity Focused Ultrasound Ablation

PubMed Central

Wu, Ziqi; Gudur, Madhu S. R.; Deng, Cheri X.

2013-01-01

Intra-procedural imaging is important for guiding cardiac arrhythmia ablation. It is difficult to obtain intra-procedural correlation of thermal lesion formation with action potential (AP) changes in the transmural plane during ablation. This study tested parametric ultrasound imaging for transmural imaging of lesion and AP changes in high intensity focused ultrasound (HIFU) ablation using coronary perfused canine ventricular wedge preparations (n = 13). The preparations were paced from epi/endocardial surfaces and subjected to HIFU application (3.5 MHz, 11 Hz pulse-repetition-frequency, 70% duty cycle, duration 4 s, 3500 W/cm2), during which simultaneous optical mapping (1 kframes/s) using di-4-ANEPPS and ultrasound imaging (30 MHz) of the same transmural surface of the wedge were performed. Spatiotemporally correlated AP measurements and ultrasound imaging allowed quantification of the reduction of AP amplitude (APA), shortening of AP duration at 50% repolarization, AP triangulation, decrease of optical AP rise, and change of conduction velocity along tissue depth direction within and surrounding HIFU lesions. The threshold of irreversible change in APA correlating to lesions was determined to be 43±1% with a receiver operating characteristic (ROC) area under curve (AUC) of 0.96±0.01 (n = 13). Ultrasound imaging parameters such as integrated backscatter, Rayleigh (α) and log-normal (σ) parameters, cumulative extrema of σ were tested, with the cumulative extrema of σ performing the best in detecting lesion (ROC AUC 0.89±0.01, n = 13) and change of APA (ROC AUC 0.79±0.03, n = 13). In conclusion, characteristic tissue and AP changes in HIFU ablation were identified and spatiotemporally correlated using optical mapping and ultrasound imaging. Parametric ultrasound imaging using cumulative extrema of σ can detect HIFU lesion and APA reduction. PMID:24349337

Transmural ultrasound imaging of thermal lesion and action potential changes in perfused canine cardiac wedge preparations by high intensity focused ultrasound ablation.

PubMed

Wu, Ziqi; Gudur, Madhu S R; Deng, Cheri X

2013-01-01

Intra-procedural imaging is important for guiding cardiac arrhythmia ablation. It is difficult to obtain intra-procedural correlation of thermal lesion formation with action potential (AP) changes in the transmural plane during ablation. This study tested parametric ultrasound imaging for transmural imaging of lesion and AP changes in high intensity focused ultrasound (HIFU) ablation using coronary perfused canine ventricular wedge preparations (n = 13). The preparations were paced from epi/endocardial surfaces and subjected to HIFU application (3.5 MHz, 11 Hz pulse-repetition-frequency, 70% duty cycle, duration 4 s, 3500 W/cm(2)), during which simultaneous optical mapping (1 kframes/s) using di-4-ANEPPS and ultrasound imaging (30 MHz) of the same transmural surface of the wedge were performed. Spatiotemporally correlated AP measurements and ultrasound imaging allowed quantification of the reduction of AP amplitude (APA), shortening of AP duration at 50% repolarization, AP triangulation, decrease of optical AP rise, and change of conduction velocity along tissue depth direction within and surrounding HIFU lesions. The threshold of irreversible change in APA correlating to lesions was determined to be 43 ± 1% with a receiver operating characteristic (ROC) area under curve (AUC) of 0.96 ± 0.01 (n = 13). Ultrasound imaging parameters such as integrated backscatter, Rayleigh (α) and log-normal (σ) parameters, cumulative extrema of σ were tested, with the cumulative extrema of σ performing the best in detecting lesion (ROC AUC 0.89 ± 0.01, n = 13) and change of APA (ROC AUC 0.79 ± 0.03, n = 13). In conclusion, characteristic tissue and AP changes in HIFU ablation were identified and spatiotemporally correlated using optical mapping and ultrasound imaging. Parametric ultrasound imaging using cumulative extrema of σ can detect HIFU lesion and APA reduction.

Endometrial Ablation

MedlinePlus

... or lighter levels. If ablation does not control heavy bleeding, further treatment or surgery may be needed. ... ablation is used to treat many causes of heavy bleeding. In most cases, women with heavy bleeding ...

Assessment of analytical techniques for predicting solid propellant exhaust plumes and plume impingement environments

NASA Technical Reports Server (NTRS)

Tevepaugh, J. A.; Smith, S. D.; Penny, M. M.

1977-01-01

An analysis of experimental nozzle, exhaust plume, and exhaust plume impingement data is presented. The data were obtained for subscale solid propellant motors with propellant Al loadings of 2, 10 and 15% exhausting to simulated altitudes of 50,000, 100,000 and 112,000 ft. Analytical predictions were made using a fully coupled two-phase method of characteristics numerical solution and a technique for defining thermal and pressure environments experienced by bodies immersed in two-phase exhaust plumes.

Time-dependent convection models of mantle thermal structure constrained by seismic tomography and geodynamics: implications for mantle plume dynamics and CMB heat flux

NASA Astrophysics Data System (ADS)

Glišović, P.; Forte, A. M.; Moucha, R.

2012-08-01

surface plates and a rigid surface. The thermal interpretation of seismic tomography models does not provide a radial profile of the horizontally averaged temperature (i.e. the geotherm) in the mantle. One important goal of this study is to obtain a steady-state geotherm with boundary layers which satisfies energy balance of the system and provides the starting point for more realistic numerical simulations of the Earth's evolution. We obtain surface heat flux in the range of Earth-like values : 37 TW for a rigid surface and 44 TW for a surface with tectonic plates coupled to the mantle flow. Also, our convection simulations deliver CMB heat flux that is on the high end of previously estimated values, namely 13 TW and 20 TW, for rigid and plate-like surface boundary conditions, respectively. We finally employ these two end-member surface boundary conditions to explore the very-long-time scale evolution of convection over billion-year time windows. These billion-year-scale simulations will allow us to determine the extent to which a 'memory' of the starting tomography-based thermal structure is preserved and hence to explore the longevity of the structures in the present-day mantle. The two surface boundary conditions, along with the geodynamically inferred radial viscosity profiles, yield steady-state convective flows that are dominated by long wavelengths throughout the lower mantle. The rigid-surface condition yields a spectrum of mantle heterogeneity dominated by spherical harmonic degree 3 and 4, and the plate-like surface condition yields a pattern dominated by degree 1. Our exploration of the time-dependence of the spatial heterogeneity shows that, for both types of surface boundary condition, deep-mantle hot upwellings resolved in the present-day tomography model are durable and stable features. These deeply rooted mantle plumes show remarkable longevity over very long geological time spans, mainly owing to the geodynamically inferred high viscosity in the lower

Conformal Ablative Thermal Protection System for Small and Large Scale Missions: Approaching TRL 6 for Planetary and Human Exploration Missions and TRL 9 for Small Probe Missions

NASA Technical Reports Server (NTRS)

Beck, R. A. S.; Gasch, M. J.; Milos, F. S.; Stackpoole, M. M.; Smith, B. P.; Switzer, M. R.; Venkatapathy, E.; Wilder, M. C.; Boghhozian, T.; Chavez-Garcia, J. F.

2015-01-01

In 2011, NASAs Aeronautics Research Mission Directorate (ARMD) funded an effort to develop an ablative thermal protection system (TPS) material that would have improved properties when compared to Phenolic Impregnated Carbon Ablator (PICA) and AVCOAT. Their goal was a conformal material, processed with a flexible reinforcement that would result in similar or better thermal characteristics and higher strain-to-failure characteristics that would allow for easier integration on flight aeroshells than then-current rigid ablative TPS materials. In 2012, NASAs Space Technology Mission Directorate (STMD) began funding the maturation of the best formulation of the game changing conformal ablator, C-PICA. Progress has been reported at IPPW over the past three years, describing C-PICA with a density and recession rates similar to PICA, but with a higher strain-to-failure which allows for direct bonding and no gap fillers, and even more important, with thermal characteristics resulting in half the temperature rise of PICA. Overall, C-PICA should be able to replace PICA with a thinner, lighter weight, less complicated design. These characteristics should be particularly attractive for use as backshell TPS on high energy planetary entry vehicles. At the end of this year, the material should be ready for missions to consider including in their design, in fact, NASAs Science Mission Directorate (SMD) is considering incentivizing the use of C-PICA in the next Discovery Proposal call. This year both scale up of the material to large (1-m) sized pieces and the design and build of small probe heatshields for flight tests will be completed. NASA, with an industry partner, will build a 1-m long manufacturing demonstration unit (MDU) with a shape based on a mid LD lifting body. In addition, in an effort to fly as you test and test as you fly, NASA, with a second industry partner, will build a small probe to test in the Interactive Heating Facility (IHF) arc jet and, using nearly the

Analysis of Depth of Ablation,Thermal Damage, Wound Healing, and Wound Contraction With Erbium YAG Laser in a Yorkshire Pig Model.

PubMed

Alsaad, Salman M S; Ross, E Victor; Smith, Wiley J; DeRienzo, Damian P

2015-11-01

The erbium YAG laser is commonly used for skin resurfacing. It is known that varying the pulse duration can influence residual thermal damage and wound healing. Our study used a porcine model to evaluate a broad range of settings in a comparison of depth of ablation, depth of residual thermal damage (RTD), and wound contraction employing both a full coverage and fractional hand piece with an erbium YAG laser. The laser delivered an ablative pulse followed by a heating pulse of variable duration using either the full coverage or fractional hand piece. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of a single Yorkshire pig were irradiated. There were 14 treatment groups. 3 sites were treated per group for a total of 42 sites. Two of the 3 sites were for observational assessments and the 3rd site served as a reservoir for biopsies. Biopsy specimens were collected on days 0, 1, 3, 7, 14, and 28. Bleeding, erythema, wound healing, and wound contraction (in the fractional hand piece groups) were assessed. Wound healing is faster for fractional laser skin resurfacing compared with traditional contiguous resurfacing as demonstrated by textural changes and degree of erythema. The laser operator can be confident that the depth of ablation displayed on this system accurately reflects what is occurring in vivo for both confluent and fractional modes. Likewise, the measured degree of coagulation was consistent with panel display settings for the confluent mode. However, the degree of coagulation, as measured by the thickness of residual thermal damage, did not vary significantly between the fractional groups. In other words, the pulse duration of the second (heating) pulse did not impact the degree of coagulation in the fractional mode. There was a 2.3% wound contraction between some groups and a 6.5% wound contraction between other groups. A two way analysis of variance found a statistically

Renal Cell Carcinoma: Comparison of RENAL Nephrometry and PADUA Scores with Maximum Tumor Diameter for Prediction of Local Recurrence after Thermal Ablation.

PubMed

Maxwell, Aaron W P; Baird, Grayson L; Iannuccilli, Jason D; Mayo-Smith, William W; Dupuy, Damian E

2017-05-01

Purpose To evaluate the performance of the radius, exophytic or endophytic, nearness to collecting system or sinus, anterior or posterior, and location relative to polar lines (RENAL) nephrometry and preoperative aspects and dimensions used for anatomic classification (PADUA) scoring systems and other tumor biometrics for prediction of local tumor recurrence in patients with renal cell carcinoma after thermal ablation. Materials and Methods This HIPAA-compliant study was performed with a waiver of informed consent after institutional review board approval was obtained. A retrospective evaluation of 207 consecutive patients (131 men, 76 women; mean age, 71.9 years ± 10.9) with 217 biopsy-proven renal cell carcinoma tumors treated with thermal ablation was conducted. Serial postablation computed tomography (CT) or magnetic resonance (MR) imaging was used to evaluate for local tumor recurrence. For each tumor, RENAL nephrometry and PADUA scores were calculated by using imaging-derived tumor morphologic data. Several additional tumor biometrics and combinations thereof were also measured, including maximum tumor diameter. The Harrell C index and hazard regression techniques were used to quantify associations with local tumor recurrence. Results The RENAL (hazard ratio, 1.43; P = .003) and PADUA (hazard ratio, 1.80; P < .0001) scores were found to be significantly associated with recurrence when regression techniques were used but demonstrated only poor to fair discrimination according to Harrell C index results (C, 0.68 and 0.75, respectively). Maximum tumor diameter showed the highest discriminatory strength of any individual variable evaluated (C, 0.81) and was also significantly predictive when regression techniques were used (hazard ratio, 2.98; P < .0001). For every 1-cm increase in diameter, the estimated rate of recurrence risk increased by 198%. Conclusion Maximum tumor diameter demonstrates superior performance relative to existing tumor scoring systems and

Ablative skin resurfacing.

PubMed

Agrawal, Nidhi; Smith, Greg; Heffelfinger, Ryan

2014-02-01

Ablative laser resurfacing has evolved as a safe and effective treatment for skin rejuvenation. Although traditional lasers were associated with significant thermal damage and lengthy recovery, advances in laser technology have improved safety profiles and reduced social downtime. CO2 lasers remain the gold standard of treatment, and fractional ablative devices capable of achieving remarkable clinical improvement with fewer side effects and shorter recovery times have made it a more practical option for patients. Although ablative resurfacing has become safer, careful patient selection and choice of suitable laser parameters are essential to minimize complications and optimize outcomes. This article describes the current modalities used in ablative laser skin resurfacing and examines their efficacy, indications, and possible side effects. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Laser ablation based fuel ignition

DOEpatents

Early, J.W.; Lester, C.S.

1998-06-23

There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition. 3 figs.

Laser ablation based fuel ignition

DOEpatents

Early, James W.; Lester, Charles S.

1998-01-01

There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition.

Computer modeling of the combined effects of perfusion, electrical conductivity, and thermal conductivity on tissue heating patterns in radiofrequency tumor ablation.

PubMed

Ahmed, Muneeb; Liu, Zhengjun; Humphries, Stanley; Goldberg, S Nahum

2008-11-01

To use an established computer simulation model of radiofrequency (RF) ablation to characterize the combined effects of varying perfusion, and electrical and thermal conductivity on RF heating. Two-compartment computer simulation of RF heating using 2-D and 3-D finite element analysis (ETherm) was performed in three phases (n = 88 matrices, 144 data points each). In each phase, RF application was systematically modeled on a clinically relevant template of application parameters (i.e., varying tumor and surrounding tissue perfusion: 0-5 kg/m(3)-s) for internally cooled 3 cm single and 2.5 cm cluster electrodes for tumor diameters ranging from 2-5 cm, and RF application times (6-20 min). In the first phase, outer thermal conductivity was changed to reflect three common clinical scenarios: soft tissue, fat, and ascites (0.5, 0.23, and 0.7 W/m- degrees C, respectively). In the second phase, electrical conductivity was changed to reflect different tumor electrical conductivities (0.5 and 4.0 S/m, representing soft tissue and adjuvant saline injection, respectively) and background electrical conductivity representing soft tissue, lung, and kidney (0.5, 0.1, and 3.3 S/m, respectively). In the third phase, the best and worst combinations of electrical and thermal conductivity characteristics were modeled in combination. Tissue heating patterns and the time required to heat the entire tumor +/-a 5 mm margin to >50 degrees C were assessed. Increasing background tissue thermal conductivity increases the time required to achieve a 50 degrees C isotherm for all tumor sizes and electrode types, but enabled ablation of a given tumor size at higher tissue perfusions. An inner thermal conductivity equivalent to soft tissue (0.5 W/m- degrees C) surrounded by fat (0.23 W/m- degrees C) permitted the greatest degree of tumor heating in the shortest time, while soft tissue surrounded by ascites (0.7 W/m- degrees C) took longer to achieve the 50 degrees C isotherm, and complete ablation

Subduction disfigured mantle plumes: Plumes that are not plumes?

NASA Astrophysics Data System (ADS)

Druken, K. A.; Stegman, D. R.; Kincaid, C. R.; Griffiths, R. W.

2012-12-01

"Hotspot" volcanism is generally attributed to upwelling of anomalously warm mantle plumes, the intra-plate Hawaiian island chain and its simple age progression serving as an archetypal example. However, interactions of such plumes with plate margins, and in particular with subduction zones, is likely to have been a common occurrence and leads to more complicated geological records. Here we present results from a series of complementary, three-dimensional numerical and laboratory experiments that examine the dynamic interaction between negatively buoyant subducting slabs and positively buoyant mantle plumes. Slab-driven flow is shown to significantly influence the evolution and morphology of nearby plumes, which leads to a range of deformation regimes of the plume head and conduit. The success or failure of an ascending plume head to reach the lithosphere depends on the combination of plume buoyancy and position within the subduction system, where the mantle flow owing to downdip and rollback components of slab motion entrain plume material both vertically and laterally. Plumes rising within the sub-slab region tend to be suppressed by the surrounding flow field, while wedge-side plumes experience a slight enhancement before ultimately being entrained by subduction. Hotspot motion is more complex than that expected at intraplate settings and is primarily controlled by position alone. Regimes include severely deflected conduits as well as retrograde (corkscrew) motion from rollback-driven flow, often with weak and variable age-progression. The interaction styles and surface manifestations of plumes can be predicted from these models, and the results have important implications for potential hotspot evolution near convergent margins.

Plume Detection and Plume Top Height Estimation using SLSTR

NASA Astrophysics Data System (ADS)

Virtanen, Timo H.; Kolmonen, Pekka; Sogacheva, Larisa; Rodriguez, Edith; Saponaro, Giulia; de Leeuw, Gerrit

2017-04-01

We present preliminary results on ash and desert dust plume detection and plume top height estimates based on satellite data from the Sea and Land Surface Temperature Radiometer (SLSTR) aboard Sentinel-3, launched in 2016. The methods are based on the previously developed AATSR Correlation Method (ACM) height estimation algorithm, which utilized the data of the preceding similar instrument, Advanced Along Track Scanning Radiometer (AATSR). The height estimate is based on the stereo-viewing capability of SLSTR, which allows to determine the parallax between the satellite's 55° backward and nadir views, and thus the corresponding height. The ash plume detection is based on the brightness temperature difference between between thermal infrared (TIR) channels centered at 11 and 12 μm, which show characteristic signals for both desert dust and ash plumes. The SLSTR instrument provides a unique combination of dual-view capability and a wavelength range from visible to thermal infrared, rendering it an ideal instrument for this work. Accurate information on the volcanic ash position is important for air traffic safety. The ACM algorithm can provide valuable data of both horizontal and vertical ash dispersion. These data may be useful for comparisons with other volcanic ash and desert dust retrieval methods and dispersion models. The current work is being carried out as part of the H2020 project EUNADICS-AV ("European Natural Disaster Coordination and Information System for Aviation"), which started in October 2016.

Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

NASA Astrophysics Data System (ADS)

De Bonis, A.; Teghil, R.; Santagata, A.; Galasso, A.; Rau, J. V.

2012-09-01

Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

Rationale for the development and the mechanism of action of endoscopic thermal vapor ablation (InterVapor) for the treatment of emphysema.

PubMed

Kesten, Steven; Anderson, Joseph C; Tuck, Stephanie A

2012-07-01

Emphysema remains a disabling disease despite current treatment. Novel approaches to the underlying physiological abnormalities responsible for symptom generation are warranted. A review of current hypotheses and preclinical and clinical data on the utility of endoscopic thermal vapor ablation (InterVapor) in the treatment of emphysema. In animal studies, thermal energy in the form of heated water vapor both in healthy and in papain-induced emphysema in dogs and sheep leads to an inflammatory response followed by healing with airway and parenchymal fibrosis. The fibrosis and associated distal atelectasis result in volume reduction. The amount of thermal energy delivered has been based on the amount of target tissue mass determined from a high-resolution computed tomogram. Early human studies indicated the feasibility of InterVapor with 5 cal/g tissue; however, the dose appeared insufficient to induce lobar volume reduction. A study using 10 cal/g to 1 upper lobe (n=44) induced a mean of 46% lobar volume reduction at 12 months along with significant improvements in the physiology and health outcomes. InterVapor induces lung volume reduction in patients with emphysema. The mechanism of action is through a thermally induced inflammatory response followed by healing with subsequent remodeling of tissue (fibrosis and distal atelectasis).

Thermal ablation of a confluent lesion in the porcine kidney with a clinically available MR-HIFU system

NASA Astrophysics Data System (ADS)

van Breugel, J. M. M.; de Greef, M.; Wijlemans, J. W.; Schubert, G.; van den Bosch, M. A. A. J.; Moonen, C. T. W.; Ries, M. G.

2017-07-01

The incidence of small renal masses (SRMs) sized  <4 cm has increased over the decades (as co-findings/or due to introduction of cross sectional imaging). Currently, partial nephrectomy (PN) or watchful waiting is advised in these patients. Ultimately, 80-90% of these SRMs require surgical treatment and PN is associated with a 15% complication rate. In this aging population, with possible comorbidities and poor health condition, both PN and watchful waiting are non-ideal treatment options. This resulted in an increased need for early, non-invasive treatment strategies such as MR-guided high intensity focused ultrasound (MR-HIFU). (i) To investigate the feasibility of creating a confluent lesion in the kidney using respiratory-gated MR-HIFU under clinical conditions in a pre-clinical study and (ii) to evaluate the reproducibility of the MR-HIFU ablation strategy. Healthy pigs (n  =  10) under general anesthesia were positioned on a clinical MR-HIFU system with integrated cooling. A honeycomb pattern of seven overlapping ablation cells (4  ×  4  ×  10 mm3, 450 W, <30 s) was ablated successively in the cortex of the porcine kidney. Both MR thermometry and acoustic energy delivery were respiratory gated using a pencil beam navigator on the contralateral kidney. The non-perfused volume (NPV) was visualized after the last sonication by contrast-enhanced (CE) T 1-weighted MR (T 1 w) imaging. Cell viability staining was performed to visualize the extent of necrosis. Results: a median NPV of 0.62 ml was observed on CE-T 1 w images (IQR 0.58-1.57 ml, range 0.33-2.75 ml). Cell viability staining showed a median damaged volume of 0.59 ml (IQR 0.24-1.35 ml, range 0-4.1 ml). Overlooking of the false rib, shivering of the pig, and too large depth combined with a large heat-sink effect resulted in insufficient heating in 4 cases. The NPV and necrosed volume were confluent in all cases in which an ablated volume could be observed. Our

Enhanced laser thermal ablation for the in vitro treatment of liver cancer by specific delivery of multiwalled carbon nanotubes functionalized with human serum albumin.

PubMed

Iancu, Cornel; Mocan, Lucian; Bele, Constantin; Orza, Anamaria Ioana; Tabaran, Flaviu A; Catoi, Cornel; Stiufiuc, Rares; Stir, Ariana; Matea, Cristian; Iancu, Dana; Agoston-Coldea, Lucia; Zaharie, Florin; Mocan, Teodora

2011-01-17

The main goal of this investigation was to develop and test a new method of treatment for human hepatocellular carcinoma (HCC). We present a method of carbon nanotube-enhanced laser thermal ablation of HepG2 cells (human hepatocellular liver carcinoma cell line) based on a simple multiwalled carbon nanotube (MWCNT) carrier system, such as human serum albumin (HSA), and demonstrate its selective therapeutic efficacy compared with normal hepatocyte cells. Both HepG2 cells and hepatocytes were treated with HSA-MWCNTs at various concentrations and at various incubation times and further irradiated using a 2 W, 808 nm laser beam. Transmission electron, phase contrast, and confocal microscopy combined with immunochemical staining were used to demonstrate the selective internalization of HSA-MWCNTs via Gp60 receptors and the caveolin-mediated endocytosis inside HepG2 cells. The postirradiation apoptotic rate of HepG2 cells treated with HSA-MWCNTs ranged from 88.24% (for 50 mg/L) at 60 sec to 92.34% (for 50 mg/L) at 30 min. Significantly lower necrotic rates were obtained when human hepatocytes were treated with HSA-MWCNTs in a similar manner. Our results clearly show that HSA-MWCNTs selectively attach on the albondin (aka Gp60) receptor located on the HepG2 membrane, followed by an uptake through a caveolin-dependent endocytosis process. These unique results may represent a major step in liver cancer treatment using nanolocalized thermal ablation by laser heating.

Enhanced laser thermal ablation for the in vitro treatment of liver cancer by specific delivery of multiwalled carbon nanotubes functionalized with human serum albumin

PubMed Central

Iancu, Cornel; Mocan, Lucian; Bele, Constantin; Orza, Anamaria Ioana; Tabaran, Flaviu A; Catoi, Cornel; Stiufiuc, Rares; Stir, Ariana; Matea, Cristian; Iancu, Dana; Agoston-Coldea, Lucia; Zaharie, Florin; Mocan, Teodora

2011-01-01

The main goal of this investigation was to develop and test a new method of treatment for human hepatocellular carcinoma (HCC). We present a method of carbon nanotube-enhanced laser thermal ablation of HepG2 cells (human hepatocellular liver carcinoma cell line) based on a simple multiwalled carbon nanotube (MWCNT) carrier system, such as human serum albumin (HSA), and demonstrate its selective therapeutic efficacy compared with normal hepatocyte cells. Both HepG2 cells and hepatocytes were treated with HSA–MWCNTs at various concentrations and at various incubation times and further irradiated using a 2 W, 808 nm laser beam. Transmission electron, phase contrast, and confocal microscopy combined with immunochemical staining were used to demonstrate the selective internalization of HSA–MWCNTs via Gp60 receptors and the caveolin-mediated endocytosis inside HepG2 cells. The postirradiation apoptotic rate of HepG2 cells treated with HSA–MWCNTs ranged from 88.24% (for 50 mg/L) at 60 sec to 92.34% (for 50 mg/L) at 30 min. Significantly lower necrotic rates were obtained when human hepatocytes were treated with HSA–MWCNTs in a similar manner. Our results clearly show that HSA–MWCNTs selectively attach on the albondin (aka Gp60) receptor located on the HepG2 membrane, followed by an uptake through a caveolin-dependent endocytosis process. These unique results may represent a major step in liver cancer treatment using nanolocalized thermal ablation by laser heating. PMID:21289990

Advanced Ablative TPS

NASA Technical Reports Server (NTRS)

Gasch, Matthew J.

2011-01-01

Early NASA missions (Gemini, Apollo, Mars Viking) employed new ablative TPS that were tailored for the entry environment. After 40 years, heritage ablative TPS materials using Viking or Pathfinder era materials are at or near their performance limits and will be inadequate for future exploration missions. Significant advances in TPS materials technology are needed in order to enable any subsequent human exploration missions beyond Low Earth Orbit. This poster summarizes some recent progress at NASA in developing families of advanced rigid/conformable and flexible ablators that could potentially be used for thermal protection in planetary entry missions. In particular the effort focuses technologies required to land heavy (approx.40 metric ton) masses on Mars to facilitate future exploration plans.

Modeling Europa's dust plumes

NASA Astrophysics Data System (ADS)

Southworth, B. S.; Kempf, S.; Schmidt, J.

2015-12-01

The discovery of Jupiter's moon Europa maintaining a probably sporadic water vapor plume constitutes a huge scientific opportunity for NASA's upcoming mission to this Galilean moon. Measuring properties of material emerging from interior sources offers a unique chance to understand conditions at Europa's subsurface ocean. Exploiting results obtained for the Enceladus plume, we simulate possible Europa plume configurations, analyze particle number density and surface deposition results, and estimate the expected flux of ice grains on a spacecraft. Due to Europa's high escape speed, observing an active plume will require low-altitude flybys, preferably at altitudes of 5-100 km. At higher altitudes a plume may escape detection. Our simulations provide an extensive library documenting the possible structure of Europa dust plumes, which can be quickly refined as more data on Europa dust plumes are collected.

High intensity focused ultrasound (HIFU) and ethanol induced tissue ablation: Thermal lesion volume and temperature ex vivo

NASA Astrophysics Data System (ADS)

Hoang, Nguyen Hai

HIFU is the upcoming technology for noninvasive or minimally invasive tumor ablation via the localized acoustic energy deposition at the focal region within the tumor target. The presence of cavitation bubbles had been shown to improve the therapeutic effect of HIFU. In this study, we have investigated the effect of HIFU on temperature rise and cavitation bubble activity in ethanol-treated porcine liver and kidney tissues. We have also explored changes in the viability and proliferation rate of HepG2, SW1376, and FB1 cancer cells with their exposure to ethanol and HIFU. Tissues were submerged in 95% ethanol for five hours and then exposed to HIFU generated by a 1.1 MHz transducer or injected into focal spot before HIFU exposure. Cavitation events were measured by a passive cavitation detection technique for a range of acoustic power from 1.17 W to 20.52 W. The temperature around the focal zone was measured by type K or type E thermocouples embedded in the samples. In experiments with cancer cells, 2.7 millions cells were treated with concentration of ethanol at concentration 2%, 4%, 10%, 25%, and 50% and the cell were exposed to HIFU with power of 2.73 W, 8.72 W, and 12.0 W for 30 seconds. Our data show that the treatment of tissues with ethanol reduces the threshold power for inertial cavitation and increases the temperature rise. The exposure of cancer cells to various HIFU power only showed a higher number of viable cells 24 to 72 hours after HIFU exposure. On the other hand, both the viability and proliferation rate were significantly decreased in cells treated with ethanol and then HIFU at 8.7 W and 12.0 W even at ethanol concentration of 2 and 4 percent. In conclusion, the results of our study indicate that percutaneous ethanol injection (PEI) and HIFU have a synergistic effect on cancer cells ablation.

Endoluminal ultrasound applicators for MR-guided thermal ablation of pancreatic tumors: Preliminary design and evaluation in a porcine pancreas model

PubMed Central

Adams, Matthew S.; Salgaonkar, Vasant A.; Plata-Camargo, Juan; Jones, Peter D.; Pascal-Tenorio, Aurea; Chen, Hsin-Yu; Bouley, Donna M.; Sommer, Graham; Pauly, Kim Butts; Diederich, Chris J.

2016-01-01

Purpose: Endoluminal ultrasound may serve as a minimally invasive option for delivering thermal ablation to pancreatic tumors adjacent to the stomach or duodenum. The objective of this study was to explore the basic feasibility of this treatment strategy through the design, characterization, and evaluation of proof-of-concept endoluminal ultrasound applicators capable of placement in the gastrointestinal (GI) lumen for volumetric pancreas ablation under MR guidance. Methods: Two variants of the endoluminal applicator, each containing a distinct array of two independently powered transducers (10 × 10 mm 3.2 MHz planar; or 8 × 10 × 20 mm radius of curvature 3.3 MHz curvilinear geometries) at the distal end of a meter long flexible catheter assembly, were designed and fabricated. Transducers and circulatory water flow for acoustic coupling and luminal cooling were contained by a low-profile polyester balloon covering the transducer assembly fixture. Each applicator incorporated miniature spiral MR coils and mechanical features (guiding tips and hinges) to facilitate tracking and insertion through the GI tract under MRI guidance. Acoustic characterization of each device was performed using radiation force balance and hydrophone measurements. Device delivery into the upper GI tract, adjacent to the pancreas, and heating characteristics for treatment of pancreatic tissue were evaluated in MR-guided ex vivo and in vivo porcine experiments. MR guidance was utilized for anatomical target identification, tracking/positioning of the applicator, and MR temperature imaging (MRTI) for PRF-based multislice thermometry, implemented in the real-time RTHawk software environment. Results: Force balance and hydrophone measurements indicated efficiencies of 48.8% and 47.8% and −3 dB intensity beam-widths of 3.2 and 1.2 mm for the planar and curvilinear transducers, respectively. Ex vivo studies on whole-porcine carcasses revealed capabilities of producing ablative temperature rise

Endoluminal ultrasound applicators for MR-guided thermal ablation of pancreatic tumors: Preliminary design and evaluation in a porcine pancreas model

SciTech Connect

Adams, Matthew S., E-mail: matt.adams@ucsf.edu; Di

Purpose: Endoluminal ultrasound may serve as a minimally invasive option for delivering thermal ablation to pancreatic tumors adjacent to the stomach or duodenum. The objective of this study was to explore the basic feasibility of this treatment strategy through the design, characterization, and evaluation of proof-of-concept endoluminal ultrasound applicators capable of placement in the gastrointestinal (GI) lumen for volumetric pancreas ablation under MR guidance. Methods: Two variants of the endoluminal applicator, each containing a distinct array of two independently powered transducers (10 × 10 mm 3.2 MHz planar; or 8 × 10 × 20 mm radius of curvature 3.3 MHzmore » curvilinear geometries) at the distal end of a meter long flexible catheter assembly, were designed and fabricated. Transducers and circulatory water flow for acoustic coupling and luminal cooling were contained by a low-profile polyester balloon covering the transducer assembly fixture. Each applicator incorporated miniature spiral MR coils and mechanical features (guiding tips and hinges) to facilitate tracking and insertion through the GI tract under MRI guidance. Acoustic characterization of each device was performed using radiation force balance and hydrophone measurements. Device delivery into the upper GI tract, adjacent to the pancreas, and heating characteristics for treatment of pancreatic tissue were evaluated in MR-guided ex vivo and in vivo porcine experiments. MR guidance was utilized for anatomical target identification, tracking/positioning of the applicator, and MR temperature imaging (MRTI) for PRF-based multislice thermometry, implemented in the real-time RTHawk software environment. Results: Force balance and hydrophone measurements indicated efficiencies of 48.8% and 47.8% and −3 dB intensity beam-widths of 3.2 and 1.2 mm for the planar and curvilinear transducers, respectively. Ex vivo studies on whole-porcine carcasses revealed capabilities of producing ablative

Enceladus's Plumes: A Rocket Analogy

NASA Astrophysics Data System (ADS)

McNutt, R. L.; Perry, M. E.; Waite, J. H.; Fletcher, G.; Cravens, T. E.

2009-12-01

The plumes of Enceladus, and the source of the E-ring in the Saturnian system, easily rank as the major, significant, and unexpected discovery of the Cassini mission. While clearly the source of the E-ring,the nature of the sources and the energetics and dynamics of the plumes and underlying jets remains a subject of intensive study. Refinements of the observations suggest supersonic flow of the primary, water-vapor effluent. Such behavior implies a sonic critical point in the flow beginning from a heated reservoir of vapor, through a constriction, and out at supersonic speeds in the space above the plume/jet channels. Such geometry and thermal conditions mimic that of a de Laval nozzle, such as used in rocket engines for converting chemically heated combustion products into a directional flow. A chamber temperature of 180K suggests an outflow speed as high as 0.8 km/s. With a column density across a jet of ~3 x 1016 cm-2 (about twice that of the broad plume) and a jet width of ~10 km, the implied outflow of water molecules is ~3 x 1010 cm-3 x π/4 (106 cm)2 x 18 amu x 1.66 x 10-27 amu/kg x 8 x 104 cm/s = ~60 kg/s in each constituent jet, of which eight were identified by the Cassini Ultraviolet Imaging Spectrograph (UVIS) during the occultation measurements of the plume region of Enceladus carried out on 24 October 2007.

Percutaneous Lung Thermal Ablation of Non-surgical Clinical N0 Non-small Cell Lung Cancer: Results of Eight Years’ Experience in 87 Patients from Two Centers

SciTech Connect

Palussiere, Jean, E-mail: J.Palussiere@bordeaux.unicancer.fr; Lagarde, Philippe, E-mail: P.Lagarde@bordeaux.unicancer.fr; Aupérin, Anne, E-mail: auperin@igr.fr

2015-02-15

PurposeTo evaluate the survival outcomes of percutaneous thermal ablation (RFA + microwaves) for patients presenting N0 non-small-cell lung cancer (NSCLC) ineligible for surgery.Materials and MethodsEighty-seven patients from two comprehensive cancer centers were included. Eighty-two patients were treated with RFA electrodes and five with microwave antenna. Overall survival (OS) and disease-free survival (DFS) were estimated and predictive factors of local tumor progression, OS and DFS identified and compared by univariate and multivariate analysesResultsMedian follow-up was 30.5 months (interquartile range 16.7–51) and tumor size was 21 mm (range 10–54 mm). Treatment was incomplete for 14 patients with a local tumor progression of 11.5, 18.3, and 21.1 % atmore » 1, 2, and 3 years, respectively. Two patients presented with neurological (grade III or IV) complications, and one died of respiratory and multivisceral failure as a result of the procedure at 29 days. In univariate analysis, increasing tumor size (P = 0.003) was the only predictive factor related to risk of local tumor progression. 5-year OS and DFS were 58.1 and 27.9 %, respectively. Sex (P = 0.044), pathology (P = 0.032), and tumor size >2 cm (P = 0.046) were prognostic factors for DFS. In multivariate analysis, pathology (P = 0.033) and tumor size >2 cm (P = 0.032) were independent prognostic factors for DFS.ConclusionsOversized and overlapping ablation of N0 NSCLC was well tolerated, effective, with few local tumor progressions, even over long-term follow-up. Increasing tumor size was the main prognostic factor linked to OS, DFS, and local tumor progression.« less

Constraints on the coupled thermal evolution of the Earth's core and mantle, the age of the inner core, and the origin of the 186Os/188Os “core signal” in plume-derived lavas

NASA Astrophysics Data System (ADS)

Lassiter, J. C.

2006-10-01

The possibility that some mantle plumes may carry a geochemical signature of core/mantle interaction has rightly generated considerable interest and attention in recent years. Correlated 186Os- 187Os enrichments in some plume-derived lavas (Hawaii, Gorgona, Kostomuksha) have been interpreted as deriving from an outer core with elevated Pt/Os and Re/Os ratios due to the solidification of the Earth's inner core (c.f., [A.D. Brandon, R.J. Walker, The debate over core-mantle interaction, Earth Planet. Sci. Lett. 232 (2005) 211-225.] and references therein). Conclusive identification of a "core signal" in plume-derived lavas would profoundly influence our understanding of mantle convection and evolution. This paper reevaluates the Os-isotope evidence for core/mantle interaction by examining other geochemical constraints on core/mantle interaction, geophysical constraints on the thermal evolution of the outer core, and geochemical and cosmochemical constraints on the abundance of heat-producing elements in the core. Additional study of metal/silicate and sulfide/silicate partitioning of K, Pb, and other trace elements is needed to more tightly constrain the likely starting composition of the Earth's core. However, available data suggest that the observed 186Os enrichments in Hawaiian and other plume-derived lavas are unlikely to derive from core/mantle interaction. 1) Core/mantle interaction sufficient to produce the observed 186Os enrichments would likely have significant effects on other tracers such as Pb- and W-isotopes that are not observed. 2) Significant partitioning of K or other heat-producing elements into the core would produce a "core depletion" pattern in the Silicate Earth very different from that observed. 3) In the absence of heat-producing elements in the core, core/mantle heat flow of ˜ 6-15 TW estimated from several independent geophysical constraints suggests an inner core age (< ˜ 2.5 Ga) too young for the outer core to have developed a significant

Time resolved optical diagnostics of ZnO plasma plumes in air

SciTech Connect

Gupta, Shyam L.; Singh, Ravi Pratap; Thareja, Raj K.

2013-10-15

We report dynamical evolution of laser ablated ZnO plasma plumes using interferometry and shadowgraphy; 2-D fast imaging and optical emission spectroscopy in air ambient at atmospheric pressure. Recorded interferograms using Nomarski interferometer and shadowgram images at various time delays show the presence of electrons and neutrals in the ablated plumes. The inference drawn from sign change of fringe shifts is consistent with two dimensional images of the plume and optical emission spectra at varying time delays with respect to ablating pulse. Zinc oxide plasma plumes are created by focusing 1.06 μm radiation on to ZnO target in air and 532more » nm is used as probe beam.« less

Ablation article and method

NASA Technical Reports Server (NTRS)

Erickson, W. D.; Sullivan, E. M. (Inventor)

1973-01-01

An ablation article, such as a conical heat shield, having an ablating surface is provided with at least one discrete area of at least one seed material, such as aluminum. When subjected to ablation conditions, the seed material is ablated. Radiation emanating from the ablated seed material is detected to analyze ablation effects without disturbing the ablation surface. By providing different seed materials having different radiation characteristics, the ablating effects on various areas of the ablating surface can be analyzed under any prevailing ablation conditions. The ablating article can be provided with means for detecting the radiation characteristics of the ablated seed material to provide a self-contained analysis unit.

Ridge jumps associated with plume-ridge interaction: Mantle plume-lithosphere interaction and hotspot magmatism

NASA Astrophysics Data System (ADS)

Mittelstaedt, E.; Ito, G.

2007-12-01

Interaction of mantle plumes and young lithosphere near mid-ocean ridges can lead to changes in spreading geometry by shifts of the ridge-axis toward the plume as seen at various hotspots, notably Iceland and the Galapagos. Previous work has shown that, with a sufficient magma flux, heating of the lithosphere by magmatism can significantly weaken the plate and, in some cases, could cause ridge jumps. Upwelling hot asthenosphere can also weaken the plate through thermal and mechanical thinning of the lithosphere. Using the finite element code CITCOM, we solve the equations of continuity, momentum and energy to examine deformation in near-ridge lithosphere associated with relatively hot upwelling asthenosphere and seafloor spreading. The mantle and lithosphere obey a non-Newtonian viscous rheology with plastic failure in the cold part of the lithosphere simulated by imposing an effective yield stress. Temperatures of the lithospheric thermal boundary region are initially given a square-root of age thermal profile while a hot patch is placed at the bottom to initiate a mantle-plume like upwelling. The effect of upwelling asthenosphere on ridge jumps is evaluated by varying three parameters: the plume excess temperature, the spreading rate and the distance of the plume from the ridge axis. Preliminary results show plume related thinning and weakening of the lithosphere over a wide area (100's of km's) with the rate of thinning increasing with the excess temperature of the plume. Initially, thinning occurs as the plume approaches the lithosphere and asthenospheric material is forced out of the way. As the plume material comes into contact with the lithosphere, thinning occurs through heating and mechanical removal of the thermal boundary layer. Thinning of the lithosphere is one of the primary factors in achieving a ridge jump. Another is large tensile stresses which can facilitate the initiation of rifting at this weakened location. Model stresses induced by the

Improved therapeutic outcomes of thermal ablation on rat orthotopic liver allograft sarcoma models by radioiodinated hypericin induced necrosis targeted radiotherapy

PubMed Central

Gao, Long; Zhang, Jian; Ma, Tengchuang; Yao, Nan; Gao, Meng; Shan, Xin; Ni, Yicheng; Shao, Haibo; Xu, Ke

2016-01-01

Residual tumor resulting in tumor recurrence after various anticancer therapies is an unmet challenge in current clinical oncology. This study aimed to investigate the hypothesis that radioiodinated hypericin (131I-Hyp) may inhibit residual tumor recurrence after microwave ablation (MWA) on rat orthotopic liver allograft sarcoma models. Thirty Sprague-Dawley (SD) rats with hepatic tumors were divided into three groups: Group A received laparotomy MWA and sequential intravenous injection (i.v.) of 131I labelled hypericin (131I-Hyp) in a time interval of 24 h; Group B received only laparotomy MWA; Group C was a blank control. Tumor inhibitory effects were monitored with in vivo magnetic resonance imaging (MRI) and these findings were compared to histopathology data before (baseline, day 0) and 1, 4, and 8 days after MWA. In addition, biodistribution of 131I-Hyp was assessed with in vivo single-photon emission computed tomography-computed tomography (SPECT-CT) imaging, in vitro autoradiography, fluorescent microscopy, and gamma counting. A fast clearance of 131I-Hyp and increasing deposit in necrotic tumors appeared over time, with a significantly higher radioactivity than other organs (0.9169 ± 1.1138 % ID/g, P < 0.01) on day 9. Tumor growth was significantly slowed down in group A compared to group B and C according to MRI images and corresponding tumor doubling time (12.13 ± 1.99, 4.09 ± 0.97, 3.36 ± 0.72 days respectively). The crescent tagerability of 131I-Hyp to necrosis was visualized consistently by autoradiography and fluorescence microscopy. In conclusion, 131I-Hyp induced necrosis targeted radiotherapy improved therapeutic outcomes of MWA on rat orthotopic liver allograft sarcoma models. PMID:27285983

Constraints on The Coupled Thermal Evolution of the Earth's Core and Mantle, The Age of The Inner Core, And The Origin of the 186Os/188Os Core(?) Signal in Plume-Derived Lavas

NASA Astrophysics Data System (ADS)

Lassiter, J. C.

2005-12-01

Thermal and chemical interaction between the core and mantle has played a critical role in the thermal and chemical evolution of the Earth's interior. Outer core convection is driven by core cooling and inner core crystallization. Core/mantle heat transfer also buffers mantle potential temperature, resulting in slower rates of mantle cooling (~50-100 K/Ga) than would be predicted from the discrepancy between current rates of surface heat loss (~44 TW) and internal radioactive heat production (~20 TW). Core/mantle heat transfer may also generate thermal mantle plumes responsible for ocean island volcanic chains such as the Hawaiian Islands. Several studies suggest that mantle plumes, in addition to transporting heat from the core/mantle boundary, also carry a chemical signature of core/mantle interaction. Elevated 186Os/188Os ratios in lavas from Hawaii, Gorgona, and in the 2.8 Ga Kostomuksha komatiites have been interpreted as reflecting incorporation of an outer core component with high time-integrated Pt/Os and Re/Os ( Brandon et al., 1999, 2003; Puchtel et al., 2005). Preferential partitioning of Os relative to Re and Pt into the inner core during inner core growth may generate elevated Re/Os and Pt/Os ratios in the residual outer core. Because of the long half-life of 190Pt (the parent of 186Os, t1/2 = 489 Ga), an elevated 186Os/188Os outer core signature in plume lavas requires that inner core crystallization began early in Earth history, most likely prior to 3.5 Ga. This in turn requires low time-averaged core/mantle heat flow (<~2.5 TW) or large quantities of heat-producing elements in the core. Core/mantle heat flow may be estimated using boundary-layer theory, by measuring the heat transported in mantle plumes, by estimating the heat transported along the outer core adiabat, or by comparing the rates of heat production, surface heat loss, and secular cooling of the mantle. All of these independent methods suggest time-averaged core/mantle heat flow of ~5

A Numerical Analysis of the Transient Response of an Ablation System Including Effects of Thermal Nonequilibrium, Mass Transfer and Chemical Kinetics. Ph.D Thesis - Virginia Polytechnic Inst. and State Univ.

NASA Technical Reports Server (NTRS)

Clark, R. K.

1972-01-01

The differential equations governing the transient response of a one-dimensional ablative thermal protection system undergoing stagnation ablation are derived. These equations are for thermal nonequilibrium effects between the pyrolysis gases and the char layer and kinetically controlled chemical reactions and mass transfer between the pyrolysis gases and the char layer. The boundary conditions are written for the particular case of stagnation heating with surface removal by oxidation or sublimation and pyrolysis of the uncharred layer occurring in a plane. The governing equations and boundary conditions are solved numerically using the modified implicit method (Crank-Nicolson method). Numerical results are compared with exact solutions for a number of simplified cases. The comparison is favorable in each instance.

Geodynamic modelling of low-buoyancy thermo-chemical plumes

NASA Astrophysics Data System (ADS)

Dannberg, Juliane; Sobolev, Stephan

2015-04-01

The Earth's biggest magmatic events that form Large Igneous Provinces are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle reach the base of the lithosphere. Classical models of thermal mantle plumes predict a flattening of the plume head to a disk-like structure, a kilometer-scale surface uplift just before the initiation of LIPs and thin plume tails. However, there are seismic observations and paleo-topography data that are difficult to explain with this classical approach. Here, using numerical models, we show that the issue can be resolved if major mantle plumes are thermo-chemical rather than purely thermal. It has been suggested a long time ago that subducted oceanic crust could be recycled by mantle plumes; and based on geochemical data, they may contain up to 15-20% of this recycled material in the form of dense eclogite, which drastically decreases their buoyancy and makes it depth-dependent. We perform numerical experiments in a 3D spherical shell geometry to investigate the dynamics of the plume ascent, the interaction between plume- and plate-driven flow and the dynamics of melting in a plume head. For this purpose, we use the finite-element code ASPECT, which allows for complex temperature-, pressure- and composition-dependent material properties. Moreover, our models incorporate phase transitions (including melting) with the accompanying rheological and density changes, Clapeyron slopes and latent heat effects for both peridotite and eclogite, mantle compressibility and a strong temperature- and depth-dependent viscosity. We demonstrate that despite their low buoyancy, such plumes can rise through the whole mantle causing only negligible surface uplift. Conditions for this ascent are high plume volume and moderate lower mantle subadiabaticity. While high plume buoyancy results in plumes directly advancing to the base of the lithosphere, plumes with slightly lower buoyancy pond in a depth of 300-400 km

Advanced Rigid Ablative TPS

NASA Technical Reports Server (NTRS)

Gasch, Matthew J.

2011-01-01

NASA Exploration Systems Mission Directorate s (ESMD) Entry, Descent, and Landing (EDL) Technology Development Project (TDP) and the NASA Aeronautics Research Mission Directorate s (ARMD) Hypersonics Project are developing new advanced rigid ablators in an effort to substantially increase reliability, decrease mass, and reduce life cycle cost of rigid aeroshell-based entry systems for multiple missions. Advanced Rigid Ablators combine ablation resistant top layers capable of high heat flux entry and enable high-speed EDL with insulating mass-efficient bottom that, insulate the structure and lower the areal weight. These materials may benefit Commercial Orbital Transportation Services (COTS) vendors and may potentially enable new NASA missions for higher velocity returns (e.g. asteroid, Mars). The materials have been thermally tested to 400-450 W/sq cm at the Laser Hardened Materials Evaluation Lab (LHMEL), Hypersonics Materials Evaluation Test System (HyMETS) and in arcjet facilities. Tested materials exhibit much lower backface temperatures and reduced recession over the baseline materials (PICA). Although the EDL project is ending in FY11, NASA in-house development of advanced ablators will continue with a focus on varying resin systems and fiber/resin interactions.

Modelling ultrafast laser ablation

NASA Astrophysics Data System (ADS)

Rethfeld, Baerbel; Ivanov, Dmitriy S.; E Garcia, Martin; Anisimov, Sergei I.

2017-05-01

This review is devoted to the study of ultrafast laser ablation of solids and liquids. The ablation of condensed matter under exposure to subpicosecond laser pulses has a number of peculiar properties which distinguish this process from ablation induced by nanosecond and longer laser pulses. The process of ultrafast ablation includes light absorption by electrons in the skin layer, energy transfer from the skin layer to target interior by nonlinear electronic heat conduction, relaxation of the electron and ion temperatures, ultrafast melting, hydrodynamic expansion of heated matter accompanied by the formation of metastable states and subsequent formation of breaks in condensed matter. In case of ultrashort laser excitation, these processes are temporally separated and can thus be studied separately. As for energy absorption, we consider peculiarities of the case of metal irradiation in contrast to dielectrics and semiconductors. We discuss the energy dissipation processes of electronic thermal wave and lattice heating. Different types of phase transitions after ultrashort laser pulse irradiation as melting, vaporization or transitions to warm dense matter are discussed. Also nonthermal phase transitions, directly caused by the electronic excitation before considerable lattice heating, are considered. The final material removal occurs from the physical point of view as expansion of heated matter; here we discuss approaches of hydrodynamics, as well as molecular dynamic simulations directly following the atomic movements. Hybrid approaches tracing the dynamics of excited electrons, energy dissipation and structural dynamics in a combined simulation are reviewed as well.

Laser ablated copper plasmas in liquid and gas ambient

NASA Astrophysics Data System (ADS)

Kumar, Bhupesh; Thareja, Raj K.

2013-05-01

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (ne) determined using Stark broadening of the Cu I (3d104d1 2D3/2-3d104p1 2P3/2 at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (Te) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ˜590 nm.

Thermal Ablation by High-Intensity-Focused Ultrasound Using a Toroid Transducer Increases the Coagulated Volume and Allows Coagulation Near Portal and Hepatic veins in Pigs

SciTech Connect

Melodelima, D.; N'Djin, W. A.; Parmentier, H.

2009-04-14

A new geometry of HIFU transducer is described to enlarge the coagulated volume. The geometry of the transducer was not spherical. The surface of the transducer was built based on a toroid geometry. The transducer was generated by the revolution of a circle about an axis lying in its plane. Eight emitters operating at a frequency of 3 MHz were diced out of a single toroid piezocomposite element. Each of the eight emitters was divided into 32 transducers. The focal zone is conical and located at 70 mm from the transducer. A 7.5 MHz ultrasound imaging probe is placed inmore » the centre of the device for guiding the treatment. Our long-term objective is to develop a device that can be used during surgery. In vivo trials have been performed on 13 pigs to demonstrate this new principle and to evaluate the vascular tolerance of the treatment. This new geometry combined with consecutive activation of the eight emitters around the toroid allows achieving a mean thermal ablation of 7.0{+-}2.5 cm3 in 40 seconds. All lesions were visible with high contrast on sonograms. The correlation between the size of lesions observed on sonograms and during gross examination was 92%. This allows the user to easily enlarge the coagulated volume by juxtaposing single lesions. The pigs tolerate the treatment well over the experimental period even when coagulation was produced through portal and/or hepatic veins.« less

MISR Aoba Volcano Plume

Atmospheric Science Data Center

2018-06-07

... in ongoing eruptions using parallax. View the MISR Active Aerosol Plume-Height (AAP) Project paper to see peak altitude and settling ... R. Kahn/NASA GSFC Access Project Paper: MISR Active Aerosol Plume-Height (AAP) Project Access and Order MISR Data and ...

RELATIVE ABUNDANCE MEASUREMENTS IN PLUMES AND INTERPLUMES

SciTech Connect

Guennou, C.; Hahn, M.; Savin, D. W., E-mail: cguennou@iac.es

2015-07-10

We present measurements of relative elemental abundances in plumes and interplumes. Plumes are bright, narrow structures in coronal holes that extend along open magnetic field lines far out into the corona. Previous work has found that in some coronal structures the abundances of elements with a low first ionization potential (FIP) <10 eV are enhanced relative to their photospheric abundances. This coronal-to-photospheric abundance ratio, commonly called the FIP bias, is typically 1 for elements with a high-FIP (>10 eV). We have used Extreme Ultraviolet Imaging Spectrometer observations made on 2007 March 13 and 14 over a ≈24 hr period tomore » characterize abundance variations in plumes and interplumes. To assess their elemental composition, we used a differential emission measure analysis, which accounts for the thermal structure of the observed plasma. We used lines from ions of iron, silicon, and sulfur. From these we estimated the ratio of the iron and silicon FIP bias relative to that for sulfur. From the results, we have created FIP-bias-ratio maps. We find that the FIP-bias ratio is sometimes higher in plumes than in interplumes and that this enhancement can be time dependent. These results may help to identify whether plumes or interplumes contribute to the fast solar wind observed in situ and may also provide constraints on the formation and heating mechanisms of plumes.« less

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry

SciTech Connect

Wicklein, S.; Koehl, A.; Dittmann, R.

2012-09-24

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime ofmore » Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.« less

Effects of Plume Hydrodynamics and Oxidation on the Composition of a Condensing Laser-Induced Plasma

DOE PAGES

Weisz, David G.; Crowhurst, Jonathan C.; Finko, Mikhail S.; ...

2018-02-01

High-temperature chemistry in laser ablation plumes leads to vapor-phase speciation, which can induce chemical fractionation during condensation. In this work, using emission spectroscopy acquired after ablation of a SrZrO 3 target, we have experimentally observed the formation of multiple molecular species (ZrO and SrO) as a function of time as the laser ablation plume evolves. Although the stable oxides SrO and ZrO 2 are both refractory, we observed emission from the ZrO intermediate at earlier times than SrO. We deduced the time-scale of oxygen entrainment into the laser ablation plume using an 18O 2 environment by observing the in-growth ofmore » Zr 18O in the emission spectra relative to Zr 16O, which was formed by reaction of Zr with 16O from the target itself. Using temporally resolved plume-imaging, we determined that ZrO formed more readily at early times, volumetrically in the plume, while SrO formed later in time, around the periphery. Lastly, using a simple temperature-dependent reaction model, we have illustrated that the formation sequence of these oxides subsequent to ablation is predictable to first order.« less

Temperature monitoring by infrared radiation measurements during ArF excimer laser ablation with cornea

NASA Astrophysics Data System (ADS)

Ishihara, Miya; Arai, Tsunenori; Sato, Shunichi; Nakano, Hironori; Obara, Minoru; Kikuchi, Makoto

1999-06-01

We measured infrared thermal radiation from porcine cornea during various fluences ArF excimer laser ablations with 1 microsecond(s) rise time. To obtain absolute temperature by means of Stefan-Boltzman law of radiation, we carried out a collection efficiency and detective sensitivity by a pre-experiment using panel heater. We measured the time course of the thermal radiation intensity with various laser fluences. We studied the relation between the peak cornea temperature during the ablation and irradiation fluences. We found the ablation situations, i.e., sub-ablation threshold, normal thermal ablation, and over-heated ablation, may be judged by both of the measured temperature transient waveforms and peak temperature. The boundary fluences corresponding to normal thermal ablation were 90 and 160 mJ/cm2. Our fast remote temperature monitoring during cornea ablation might be useful to control ablation quality/quantity of the cornea ArF laser ablation, that is PRK.

Zone radiometer measurements on a model rocket exhaust plume

NASA Technical Reports Server (NTRS)

1972-01-01

Radiometer for analytical prediction of rocket plume-to-booster thermal radiation and convective heating is described. Applications for engine combustion analysis, incineration, and pollution control by high temperature processing are discussed. Illustrations of equipment are included.

High-speed scanning ablation of dental hard tissues with a λ = 9.3 μm CO2 laser: adhesion, mechanical strength, heat accumulation, and peripheral thermal damage

NASA Astrophysics Data System (ADS)

Nguyen, Daniel; Chang, Kwang; Hedayatollahnajafi, Saba; Staninec, Michal; Chan, Kenneth; Lee, Robert; Fried, Daniel

2011-07-01

CO2 lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO2 laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO2 lasers with minimal

High-speed scanning ablation of dental hard tissues with a λ = 9.3 μm CO2 laser: adhesion, mechanical strength, heat accumulation, and peripheral thermal damage

PubMed Central

Nguyen, Daniel; Chang, Kwang; Hedayatollahnajafi, Saba; Staninec, Michal; Chan, Kenneth; Lee, Robert; Fried, Daniel

2011-01-01

CO2 lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO2 laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO2 lasers with minimal

High-speed scanning ablation of dental hard tissues with a λ = 9.3 μm CO2 laser: adhesion, mechanical strength, heat accumulation, and peripheral thermal damage.

PubMed

Nguyen, Daniel; Chang, Kwang; Hedayatollahnajafi, Saba; Staninec, Michal; Chan, Kenneth; Lee, Robert; Fried, Daniel

2011-07-01

CO(2) lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO(2) laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO(2) lasers with

Radiofrequency-induced thermal therapy: results of a European multicentre study of resistive ablation of incompetent truncal varicose veins.

PubMed

Braithwaite, B; Hnatek, L; Zierau, U; Camci, M; Akkersdijk, Gjm; Nio, D; Sarlija, M; Ajduk, M; Santoro, P; Roche, E

2013-02-01

To investigate the effectiveness of bipolar radiofrequency-induced thermal therapy (RFITT) in a multicentre non-randomized study. Some 672 incompetent saphenous veins (85% great saphenous varicose vein, 15% short saphenous vein) in 462 patients (56.5% CEAP [clinical, aetiological, anatomical and pathological elements] class 3 or worse) were treated in eight European centres. Patients were assessed between 180 and 360 days postoperatively. Occlusion rates were determined by duplex ultrasound and compared with the power used for treatment, pull back rate and experience of the operating surgeon. Complete occlusion rates of 98.4% were achieved when treatments were performed by an experienced operator (more than 20 cases), when the maximum power setting on the RFITT generator was between 18 and 20 W and the applicator was withdrawn at a rate slower than 1.5 second/cm RFITT is efficacious, well tolerated by patients and has a low incidence of procedure-related post-operative complications.

Prometheus: Io's wandering plume.

PubMed

Kieffer, S W; Lopes-Gautier, R; McEwen, A; Smythe, W; Keszthelyi, L; Carlson, R

2000-05-19

Unlike any volcanic behavior ever observed on Earth, the plume from Prometheus on Io has wandered 75 to 95 kilometers west over the last 20 years since it was first discovered by Voyager and more recently observed by Galileo. Despite the source motion, the geometric and optical properties of the plume have remained constant. We propose that this can be explained by vaporization of a sulfur dioxide and/or sulfur "snowfield" over which a lava flow is moving. Eruption of a boundary-layer slurry through a rootless conduit with sonic conditions at the intake of the melted snow can account for the constancy of plume properties.

Thermodynamic properties and transport coefficients of air thermal plasmas mixed with ablated vapors of Cu and polytetrafluoroethylene

SciTech Connect

Zhang, JunMin, E-mail: jmzhang@buaa.edu.cn, E-mail: guanyg@tsinghua.edu.cn; Lu, ChunRong; Guan, YongGang, E-mail: jmzhang@buaa.edu.cn, E-mail: guanyg@tsinghua.edu.cn

2015-10-15

Because the fault arc in aircraft electrical system often causes a fire, it is particularly important to analyze its energy and transfer for aircraft safety. The calculation of arc energy requires the basic parameters of the arc. This paper is mainly devoted to the calculations of equilibrium composition, thermodynamic properties (density, molar weight, enthalpy, and specific heat at constant pressure) and transport coefficients (thermal conductivity, electrical conductivity, and viscosity) of plasmas produced by a mixture of air, Cu, and polytetrafluoroethylene under the condition of local thermodynamic equilibrium. The equilibrium composition is determined by solving a system of equations around themore » number densities of each species. The thermodynamic properties are obtained according to the standard thermodynamic relationships. The transport coefficients are calculated using the Chapman-Enskog approximations. Results are presented in the temperature range from 3000 to 30 000 K for pressures of 0.08 and 0.1 MPa, respectively. The results are more accurate and are reliable reference data for theoretical analysis and computational simulation of the behavior of fault arc.« less

Seismically imaging the Afar plume

NASA Astrophysics Data System (ADS)

Hammond, J. O.; Kendall, J. M.; Bastow, I. D.; Stuart, G. W.; Keir, D.; Ayele, A.; Ogubazghi, G.; Ebinger, C. J.; Belachew, M.

2011-12-01

Plume related flood basalt volcanism in Ethiopia has long been cited to have instigated continental breakup in northeast Africa. However, to date seismic images of the mantle beneath the region have not produced conclusive evidence of a plume-like structure. As a result the nature and even existence of a plume in the region and its role in rift initiation and continental rupture are debated. Previous seismic studies using regional deployments of sensors in East-Africa show that low seismic velocities underlie northeast Africa, but their resolution is limited to the top 200-300km of the Earth. Thus, the connection between the low velocities in the uppermost mantle and those imaged in global studies in the lower mantle is unclear. We have combined new data from Afar, Ethiopia with 6 other regional experiments and global network stations across Ethiopia, Eritrea, Djibouti and Yemen, to produce high-resolution models of upper mantle P- and S- wave velocities to the base of the transition zone. Relative travel time tomographic inversions show that the top 100km is dominated by focussed low velocity zones, likely associated with melt in the lithosphere/uppermost asthenosphere. Below these depths a broad SW-NE oriented sheet like upwelling extends down to the top of the transition zone. Within the transition zone two focussed sharp-sided low velocity regions exist: one beneath the Western Ethiopian plateau outside the rift valley, and the other beneath the Afar depression. The nature of the transition zone anomalies suggests that small upwellings may rise from a broader low velocity plume-like feature in the lower mantle. This interpretation is supported by numerical and analogue experiments that suggest the 660km phase change and viscosity jump may impede flow from the lower to upper mantle creating a thermal boundary layer at the base of the transition zone. This allows smaller, secondary upwellings to initiate and rise to the surface. Our images of secondary upwellings

The 2016 Case for Mantle Plumes and a Plume-Fed Asthenosphere (Augustus Love Medal Lecture)

NASA Astrophysics Data System (ADS)

Morgan, Jason P.

2016-04-01

The process of science always returns to weighing evidence and arguments for and against a given hypothesis. As hypotheses can only be falsified, never universally proved, doubt and skepticism remain essential elements of the scientific method. In the past decade, even the hypothesis that mantle plumes exist as upwelling currents in the convecting mantle has been subject to intense scrutiny; from geochemists and geochronologists concerned that idealized plume models could not fit many details of their observations, and from seismologists concerned that mantle plumes can sometimes not be 'seen' in their increasingly high-resolution tomographic images of the mantle. In the place of mantle plumes, various locally specific and largely non-predictive hypotheses have been proposed to explain the origins of non-plate boundary volcanism at Hawaii, Samoa, etc. In my opinion, this debate has now passed from what was initially an extremely useful restorative from simply 'believing' in the idealized conventional mantle plume/hotspot scenario to becoming an active impediment to our community's ability to better understand the dynamics of the solid Earth. Having no working hypothesis at all is usually worse for making progress than having an imperfect and incomplete but partially correct one. There continues to be strong arguments and strong emerging evidence for deep mantle plumes. Furthermore, deep thermal plumes should exist in a mantle that is heated at its base, and the existence of Earth's (convective) geodynamo clearly indicates that heat flows from the core to heat the mantle's base. Here I review recent seismic evidence by French, Romanowicz, and coworkers that I feel lends strong new observational support for the existence of deep mantle plumes. I also review recent evidence consistent with the idea that secular core cooling replenishes half the mantle's heat loss through its top surface, e.g. that the present-day mantle is strongly bottom heated. Causes for

CHLORINATED SOLVENT PLUME CONTROL

EPA Science Inventory

This lecture will cover recent success in controlling and assessing the treatment of shallow ground water plumes of chlorinated solvents, other halogenated organic compounds, and methyl tert-butyl ether (MTBE).

Cystic echinococcosis of the liver and lung treated by radiofrequency thermal ablation: an ex-vivo pilot experimental study in animal models.

PubMed

Lamonaca, Vincenzo; Virga, Antonino; Minervini, Marta Ida; Di Stefano, Roberta; Provenzani, Alessio; Tagliareni, Pietro; Fleres, Giovanna; Luca, Angelo; Vizzini, Giovanni; Palazzo, Ugo; Gridelli, Bruno

2009-07-14

To evaluate radiofrequency thermal ablation (RTA) for treatment of cystic echinococcosis in animal models (explanted organs). Infected livers and lungs from slaughtered animals, 10 bovine and two ovine, were collected. Cysts were photographed, and their volume, cyst content, germinal layer adhesion status, wall calcification and presence of daughter or adjacent cysts were evaluated by ultrasound. Some cysts were treated with RTA at 150 W, 80 degrees C, 7 min. Temperature was monitored inside and outside the cyst. A second needle was placed inside the cyst for pressure stabilization. After treatment, all cysts were sectioned and examined by histology. Cysts were defined as alive if a preserved germinal layer at histology was evident, and as successfully treated if the germinal layer was necrotic. The subjects of the study were 17 cysts (nine hepatic and eight pulmonary), who were treated with RTA. Pathology showed 100% success rate in both hepatic (9/9) and lung cysts (8/8); immediate volume reduction of at least 65%; layer of host tissue necrosis outside the cyst, with average extension of 0.64 cm for liver and 1.57 cm for lung; and endocyst attached to the pericystium both in hepatic and lung cysts with small and focal de novo endocyst detachment in just 3/9 hepatic cysts. RTA appears to be very effective in killing hydatid cysts of explanted liver and lung. Bile duct and bronchial wall necrosis, persistence of endocyst attached to pericystium, should help avoid or greatly decrease in vivo post-treatment fistula occurrence and consequent overlapping complications that are common after surgery or percutaneous aspiration, injection and reaspiration. In vivo studies are required to confirm and validate this new therapeutic approach.

Effects of pressure rise on cw laser ablation of tissue

NASA Astrophysics Data System (ADS)

LeCarpentier, Gerald L.; Motamedi, Massoud; Welch, Ashley J.

1991-06-01

The objectives of this research were to identify mechanisms responsible for the initiation of continuous wave (cw) laser ablation of tissue and investigate the role of pressure in the ablation process. Porcine aorta samples were irradiated in a chamber pressurized from 1 X 10-4 to 12 atmospheres absolute pressure. Acrylic and Zn-Se windows in the experimental pressure chamber allowed video and infrared cameras to simultaneously record mechanical and thermal events associated with cw argon laser ablation of these samples. Video and thermal images of tissue slabs documented the explosive nature of cw laser ablation of soft biological media and revealed similar ablation threshold temperatures and ablation onset times under different environmental pressures; however, more violent initiation explosions with decreasing environmental pressures were observed. These results suggest that ablation initiates with thermal alterations in the mechanical strength of the tissue and proceeds with an explosion induced by the presence superheated liquid within the tissue.

Sulfur plumes off Namibia

NASA Technical Reports Server (NTRS)

2002-01-01

Sulfur plumes rising up from the bottom of the ocean floor produce colorful swirls in the waters off the coast of Namibia in southern Africa. The plumes come from the breakdown of marine plant matter by anaerobic bacteria that do not need oxygen to live. This image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on April 24, 2002 Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

Intracranial inertial cavitation threshold and thermal ablation lesion creation using MRI-guided 220-kHz focused ultrasound surgery: preclinical investigation.

PubMed

Xu, Zhiyuan; Carlson, Carissa; Snell, John; Eames, Matt; Hananel, Arik; Lopes, M Beatriz; Raghavan, Prashant; Lee, Cheng-Chia; Yen, Chun-Po; Schlesinger, David; Kassell, Neal F; Aubry, Jean-Francois; Sheehan, Jason

2015-01-01

In biological tissues, it is known that the creation of gas bubbles (cavitation) during ultrasound exposure is more likely to occur at lower rather than higher frequencies. Upon collapsing, such bubbles can induce hemorrhage. Thus, acoustic inertial cavitation secondary to a 220-kHz MRI-guided focused ultrasound (MRgFUS) surgery is a serious safety issue, and animal studies are mandatory for laying the groundwork for the use of low-frequency systems in future clinical trials. The authors investigate here the in vivo potential thresholds of MRgFUS-induced inertial cavitation and MRgFUS-induced thermal coagulation using MRI, acoustic spectroscopy, and histology. Ten female piglets that had undergone a craniectomy were sonicated using a 220-kHz transcranial MRgFUS system over an acoustic energy range of 5600-14,000 J. For each piglet, a long-duration sonication (40-second duration) was performed on the right thalamus, and a short sonication (20-second duration) was performed on the left thalamus. An acoustic power range of 140-300 W was used for long-duration sonications and 300-700 W for short-duration sonications. Signals collected by 2 passive cavitation detectors were stored in memory during each sonication, and any subsequent cavitation activity was integrated within the bandwidth of the detectors. Real-time 2D MR thermometry was performed during the sonications. T1-weighted, T2-weighted, gradient-recalled echo, and diffusion-weighted imaging MRI was performed after treatment to assess the lesions. The piglets were killed immediately after the last series of posttreatment MR images were obtained. Their brains were harvested, and histological examinations were then performed to further evaluate the lesions. Two types of lesions were induced: thermal ablation lesions, as evidenced by an acute ischemic infarction on MRI and histology, and hemorrhagic lesions, associated with inertial cavitation. Passive cavitation signals exhibited 3 main patterns identified as

Selective ablation of rabbit atherosclerotic plaque with less thermal effect by the control of pulse structure of a quantum cascade laser in the 5.7 μm wavelength range

NASA Astrophysics Data System (ADS)

Hashimura, Keisuke; Ishii, Katsunori; Awazu, Kunio

2016-03-01

Cholesteryl esters are main components of atherosclerotic plaques and have an absorption peak at the wavelength of 5.75 μm originated from C=O stretching vibration mode of ester bond. Our group achieved the selective ablation of atherosclerotic lesions using a quantum cascade laser (QCL) in the 5.7 μm wavelength range. QCLs are relatively new types of semiconductor lasers that can emit mid-infrared range. They are sufficiently compact and considered to be useful for clinical application. However, large thermal effects were observed because the QCL worked as quasicontinuous wave (CW) lasers due to its short pulse interval. Then we tried macro pulse irradiation (irradiation of pulses at intervals) of the QCL and achieved effective ablation with less-thermal effects than conventional quasi-CW irradiation. However, lesion selectivity might be changed by changing pulse structure. Therefore, in this study, irradiation effects of the macro pulse irradiation to rabbit atherosclerotic plaque and normal vessel were compared. The macro pulse width and the macro pulse interval were set to 0.5 and 12 ms, respectively, because the thermal relaxation time of rabbit normal and atherosclerotic aortas in the oscillation wavelength of the QCL was 0.5-12 ms. As a result, cutting difference was achieved between rabbit atherosclerotic and normal aortas by the macro pulse irradiation. Therefore, macro pulse irradiation of a QCL in the 5.7 μm wavelength range is effective for reducing thermal effects and selective ablation of the atherosclerotic plaque. QCLs have the potential of realizing less-invasive laser angioplasty.

Modern Advances in Ablative TPS

NASA Technical Reports Server (NTRS)

Venkatapathy, Ethiraj

2013-01-01

Topics covered include: Physics of Hypersonic Flow and TPS Considerations. Destinations, Missions and Requirements. State of the Art Thermal Protection Systems Capabilities. Modern Advances in Ablative TPS. Entry Systems Concepts. Flexible TPS for Hypersonic Inflatable Aerodynamic Decelerators. Conformal TPS for Rigid Aeroshell. 3-D Woven TPS for Extreme Entry Environment. Multi-functional Carbon Fabric for Mechanically Deployable.

Magnetic Resonance Mediated Radiofrequency Ablation.

PubMed

Hue, Yik-Kiong; Guimaraes, Alexander R; Cohen, Ouri; Nevo, Erez; Roth, Abraham; Ackerman, Jerome L

2018-02-01

To introduce magnetic resonance mediated radiofrequency ablation (MR-RFA), in which the MRI scanner uniquely serves both diagnostic and therapeutic roles. In MR-RFA scanner-induced RF heating is channeled to the ablation site via a Larmor frequency RF pickup device and needle system, and controlled via the pulse sequence. MR-RFA was evaluated with simulation of electric and magnetic fields to predict the increase in local specific-absorption-rate (SAR). Temperature-time profiles were measured for different configurations of the device in agar phantoms and ex vivo bovine liver in a 1.5 T scanner. Temperature rise in MR-RFA was imaged using the proton resonance frequency method validated with fiber-optic thermometry. MR-RFA was performed on the livers of two healthy live pigs. Simulations indicated a near tenfold increase in SAR at the RFA needle tip. Temperature-time profiles depended significantly on the physical parameters of the device although both configurations tested yielded temperature increases sufficient for ablation. Resected livers from live ablations exhibited clear thermal lesions. MR-RFA holds potential for integrating RF ablation tumor therapy with MRI scanning. MR-RFA may add value to MRI with the addition of a potentially disposable ablation device, while retaining MRI's ability to provide real time procedure guidance and measurement of tissue temperature, perfusion, and coagulation.

Improved model for the angular dependence of excimer laser ablation rates in polymer materials

NASA Astrophysics Data System (ADS)

Pedder, J. E. A.; Holmes, A. S.; Dyer, P. E.

2009-10-01

Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer's law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.

A Brilliant Plume

NASA Technical Reports Server (NTRS)

2007-01-01

The Long Range Reconnaissance Imager (LORRI) on New Horizons captured another dramatic picture of Jupiter's moon Io and its volcanic plumes, 19 hours after the spacecraft's closest approach to Jupiter on Feb. 28, 2007. LORRI took this 75 millisecond exposure at 0035 Universal Time on March 1, 2007, when Io was 2.3 million kilometers (1.4 million miles) from the spacecraft.

Io's dayside is deliberately overexposed to bring out faint details in the plumes and on the moon's night side. The continuing eruption of the volcano Tvashtar, at the 1 o'clock position, produces an enormous plume roughly 330 kilometers (200 miles) high, which is illuminated both by sunlight and 'Jupiter light.'

The shadow of Io, cast by the Sun, slices across the plume. The plume is quite asymmetrical and has a complicated wispy texture, for reasons that are still mysterious. At the heart of the eruption incandescent lava, seen here as a brilliant point of light, is reminding scientists of the fire fountains spotted by the Galileo Jupiter orbiter at Tvashtar in 1999.

The sunlit plume faintly illuminates the surface underneath. 'New Horizons and Io continue to astonish us with these unprecedented views of the solar system's most geologically active body' says John Spencer, deputy leader of the New Horizons Jupiter Encounter Science Team and an Io expert from Southwest Research Institute.

Because this image shows the side of Io that faces away from Jupiter, the large planet does not illuminate the moon's night side except for an extremely thin crescent outlining the edge of the disk at lower right. Another plume, likely from the volcano Masubi, is illuminated by Jupiter just above this lower right edge. A third and much fainter plume, barely visible at the 2 o'clock position, could be the first plume seen from the volcano Zal Patera.

As in other New Horizons images of Io, mountains catch the setting Sun just beyond the terminator (the line dividing day and night

A Mass Spectrometry Study of Isotope Separation in the Laser Plume

NASA Astrophysics Data System (ADS)

Suen, Timothy Wu

Accurate quantification of isotope ratios is critical for both preventing the development of illicit weapons programs in nuclear safeguards and identifying the source of smuggled material in nuclear forensics. While isotope analysis has traditionally been performed by mass spectrometry, the need for in situ measurements has prompted the development of optical techniques, such as laser-induced breakdown spectroscopy (LIBS) and laser ablation molecular isotopic spectrometry (LAMIS). These optical measurements rely on laser ablation for direct solid sampling, but several past studies have suggested that the distribution of isotopes in the ablation plume is not uniform. This study seeks to characterize isotope separation in the laser plume through the use of orthogonal-acceleration time-of-flight mass spectrometry. A silver foil was ablated with a Nd:YAG at 355 nm at an energy of 50 muJ with a spot size of 71 mum, for a fluence of 1.3 J/cm2 and an irradiance of 250 MW/cm2. Flat-plate repellers were used to sample the plume, and a temporal profile of the ions was obtained by varying the time delay on the high-voltage pulse. A spatial profile along the axis of the plume was generated by changing the position of the sample, which yielded snapshots of the isotopic composition with time. In addition, the reflectron time-of-flight system was used as an energy filter in conjunction with the repellers to sample slices of the laser plasma orthogonal to the plume axis. Mass spectrometry of the plume revealed a fast ion distribution and a slow ion distribution. Measurements taken across the entire plume showed the fast 109Ag ions slightly ahead in both space and time, causing the 107Ag fraction to drop to 0.34 at 3 mus, 4 mm from the sample surface. Although measurements centered on the near side of the plume did not show isotope separation, the slow ions on the far side of the plume included much more 109Ag than 107Ag. In addition to examining the isotope content of the ablation

Ablative therapy for liver tumours

PubMed Central

Dick, E A; Taylor-Robinson, S D; Thomas, H C; Gedroyc, W M W

2002-01-01

Established ablative therapies for the treatment of primary and secondary liver tumours, including percutaneous ethanol injection, cryotherapy, and radiofrequency ablation, are discussed. Newer techniques such as magnetic resonance imaging guided laser interstitial thermal therapy of liver tumours has produced a median survival rate of 40.8 months after treatment. The merits of this newly emerging technique are discussed, together with future developments, such as focused ultrasound therapy, which holds the promise of non-invasive thermoablation treatment on an outpatient basis. PMID:11950826

Skylon Aerodynamics and SABRE Plumes

NASA Technical Reports Server (NTRS)

Mehta, Unmeel; Afosmis, Michael; Bowles, Jeffrey; Pandya, Shishir

2015-01-01

An independent partial assessment is provided of the technical viability of the Skylon aerospace plane concept, developed by Reaction Engines Limited (REL). The objectives are to verify REL's engineering estimates of airframe aerodynamics during powered flight and to assess the impact of Synergetic Air-Breathing Rocket Engine (SABRE) plumes on the aft fuselage. Pressure lift and drag coefficients derived from simulations conducted with Euler equations for unpowered flight compare very well with those REL computed with engineering methods. The REL coefficients for powered flight are increasingly less acceptable as the freestream Mach number is increased beyond 8.5, because the engineering estimates did not account for the increasing favorable (in terms of drag and lift coefficients) effect of underexpanded rocket engine plumes on the aft fuselage. At Mach numbers greater than 8.5, the thermal environment around the aft fuselage is a known unknown-a potential design and/or performance risk issue. The adverse effects of shock waves on the aft fuselage and plumeinduced flow separation are other potential risks. The development of an operational reusable launcher from the Skylon concept necessitates the judicious use of a combination of engineering methods, advanced methods based on required physics or analytical fidelity, test data, and independent assessments.

Plasma plume expansion dynamics in nanosecond Nd:YAG laserosteotome

NASA Astrophysics Data System (ADS)

Abbasi, Hamed; Rauter, Georg; Guzman, Raphael; Cattin, Philippe C.; Zam, Azhar

2018-02-01

In minimal invasive laser osteotomy precise information about the ablation process can be obtained with LIBS in order to avoid carbonization, or cutting of wrong types of tissue. Therefore, the collecting fiber for LIBS needs to be optimally placed in narrow cavities in the endoscope. To determine this optimal placement, the plasma plume expansion dynamics in ablation of bone tissue by the second harmonic of a nanosecond Nd:YAG laser at 532 nm has been studied. The laserinduced plasma plume was monitored in different time delays, from one nanosecond up to one hundred microseconds. Measurements were performed using high-speed gated illumination imaging. The expansion features were studied using illumination of the overall visible emission by using a gated intensified charged coupled device (ICCD). The camera was capable of having a minimum gate width (Optical FWHM) of 3 ns and the timing resolution (minimum temporal shift of the gate) of 10 ps. The imaging data were used to generate position-time data of the luminous plasma-front. Moreover, the velocity of the plasma plume expansion was studied based on the time-resolved intensity data. By knowing the plasma plume profile over time, the optimum position (axial distance from the laser spot) of the collecting fiber and optimal time delay (to have the best signal to noise ratio) in spatial-resolved and time-resolved laser-induced breakdown spectroscopy (LIBS) can be determined. Additionally, the function of plasma plume expansion could be used to study the shock wave of the plasma plume.

Parameters of thermochemical plumes responsible for the formation of batholiths: Results of experimental simulation

NASA Astrophysics Data System (ADS)

Kirdyashkin, A. A.; Kirdyashkin, A. G.; Gurov, V. V.

2017-07-01

Based on laboratory and theoretical modeling results, we present the thermal and hydrodynamical structure of the plume conduit during plume ascent and eruption on the Earth's surface. The modeling results show that a mushroom-shaped plume head forms after melt eruption on the surface for 1.9 < Ka < 10. Such plumes can be responsible for the formation of large intrusive bodies, including batholiths. The results of laboratory modeling of plumes with mushroom-shaped heads are presented for Ka = 8.7 for a constant viscosity and uniform melt composition. Images of flow patterns are obtained, as well as flow velocity profiles in the melt of the conduit and the head of the model plume. Based on the laboratory modeling data, we present a scheme of a thermochemical plume with a mushroom-shaped head responsible for the formation of a large intrusive body (batholith). After plume eruption to the surface, melting occurs along the base of the massif above the plume head, resulting in a mushroom-shaped plume head. A possible mechanism for the formation of localized surface manifestations of batholiths is presented. The parameters of some plumes with mushroom-shaped heads (plumes of the Altay-Sayan and Barguzin-Vitim large-igneous provinces, and Khangai and Khentei plumes) are estimated using geological data, including age intervals and volumes of magma melts.

Advanced film-forming gel formula vs spring thermal water and white petrolatum as primary dressings after full-face ablative fractional CO2 laser resurfacing: a comparative split-face pilot study.

PubMed

Marini, L

2018-01-01

Aesthetically pleasing results and fast, uneventful recovery are highly desirable after rejuvenating ablative laser procedures. Wound dressings following ablative laser procedures should ideally improve and optimize the wound healing environment. The purpose of this comparative split-face, single-blinded, prospective observational study was to assess the efficacy and acceptability of two primary wound dressings immediately after a full-face fractional CO 2 laser resurfacing procedure. The assessments of an innovative film-forming dressing called Stratacel (SC) vs spring thermal water + Vaseline (V+) were conducted after a standardized, single-pass, full-face ablative fractional CO 2 laser skin resurfacing procedure. Clinical parameters, such as haemoglobin - HB; surface temperature - ST; micro-textural modifications - MT; superficial melanin - M; intrafollicular porphyrins - P, were assessed at different phases of the healing process using standardized, non-invasive technologies. Five female volunteers were enrolled in this inpatient, controlled pilot study. Most of the clinical parameters considered, including 3D surface texture analysis, revealed a better performance of SC vs. V+ during the early, more delicate phases of the healing process. This preliminary study, even if performed on a small number of volunteers, confirmed a definite advantage of the tested semipermeable film-forming formula (SC) over a more conventional postoperative skin care regime (V+). Clinical results could be explained by a better uniformity of distribution of SC over the micro-irregularities induced by ablative fractional CO 2 laser resurfacing. Its thin, semipermeable film might, in fact, act as an efficient, perfectly biocompatible, full contact, temporary skin barrier, able to protect extremely delicate healing surfaces from potential environmental irritations. © 2017 European Academy of Dermatology and Venereology.

Eiffel Tower Plume

NASA Image and Video Library

2015-08-19

This still image from an animation from NASA GSFC Solar Dynamics Observatory shows a single plume of plasma, many times taller than the diameter of Earth, spewing streams of particles for over two days Aug. 17-19, 2015 before breaking apart. At times, its shape resembled the Eiffel Tower. Other lesser plumes and streams of particles can be seen dancing above the solar surface as well. The action was observed in a wavelength of extreme ultraviolet light. http://photojournal.jpl.nasa.gov/catalog/PIA19875

Method for selective thermal ablation

NASA Technical Reports Server (NTRS)

Ngo, Phong (Inventor); Arndt, G. Dickey (Inventor); Raffoul, George W. (Inventor); Carl, James (Inventor)

2003-01-01

A method, simulation, and apparatus are provided that are highly suitable for treatment of benign prostatic hyperplasia (BPH). A catheter is disclosed that includes a small diameter disk loaded monopole antenna surrounded by fusion material having a high heat of fusion and a melting point preferably at or near body temperature. Microwaves from the antenna heat prostatic tissue to promote necrosing of the prostatic tissue that relieves the pressure of the prostatic tissue against the urethra as the body reabsorbs the necrosed or dead tissue. The fusion material keeps the urethra cool by means of the heat of fusion of the fusion material. This prevents damage to the urethra while the prostatic tissue is necrosed. A computer simulation is provided that can be used to predict the resulting temperature profile produced in the prostatic tissue. By changing the various control features of the catheter and method of applying microwave energy a temperature profile can be predicted and produced that is similar to the temperature profile desired for the particular patient.

Method for Selective Thermal Ablation

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Carl, James (Inventor); Ngo, Phong (Inventor); Raffoul, George W. (Inventor)

2003-01-01

A method, simulation, and apparatus are provided that are highly suitable for treatment of benign prostatic hyperplasia (BPH). A catheter is disclosed that includes a small diameter disk loaded monopole antenna surrounded by fusion material having a high heat of fusion and a melting point preferably at or near body temperature. Microwaves from the antenna heat prostatic tissue to promote necrosing of the prostatic tissue that relieves the pressure of the prostatic tissue against the urethra as the body reabsorbs the necrosed or dead tissue. The fusion material keeps the urethra cool by means of the heat of fusion of the fusion material. This prevents damage to the urethra while the prostatic tissue is necrosed. A computer simulation is provided that can be used to predict the resulting temperature profile produced in the prostatic tissue. By changing the various control features of the catheter and method of applying microwave energy a temperature profile can be predicted and produced that is similar to the temperature profile desired for the particular patient.

Mt Agung (Bali) Eruption Plumes

Atmospheric Science Data Center

2018-05-23

article title:  Mt Agung (Bali) Eruption Plumes     View larger image ... 2017 (left) and calculated plume heights (right)   Volcanic eruptions can generate a significant amount of atmospheric aerosols ...

Active Volcanic Plumes on Io

NASA Image and Video Library

1998-03-26

This color image, acquired during NASA Galileo ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon, erupting over a caldera volcanic depression named Pillan Patera.

Microwave ablation of hepatocellular carcinoma

PubMed Central

Poggi, Guido; Tosoratti, Nevio; Montagna, Benedetta; Picchi, Chiara

2015-01-01

Although surgical resection is still the optimal treatment option for early-stage hepatocellular carcinoma (HCC) in patients with well compensated cirrhosis, thermal ablation techniques provide a valid non-surgical treatment alternative, thanks to their minimal invasiveness, excellent tolerability and safety profile, proven efficacy in local disease control, virtually unlimited repeatability and cost-effectiveness. Different energy sources are currently employed in clinics as physical agents for percutaneous or intra-surgical thermal ablation of HCC nodules. Among them, radiofrequency (RF) currents are the most used, while microwave ablations (MWA) are becoming increasingly popular. Starting from the 90s’, RF ablation (RFA) rapidly became the standard of care in ablation, especially in the treatment of small HCC nodules; however, RFA exhibits substantial performance limitations in the treatment of large lesions and/or tumors located near major heat sinks. MWA, first introduced in the Far Eastern clinical practice in the 80s’, showing promising results but also severe limitations in the controllability of the emitted field and in the high amount of power employed for the ablation of large tumors, resulting in a poor coagulative performance and a relatively high complication rate, nowadays shows better results both in terms of treatment controllability and of overall coagulative performance, thanks to the improvement of technology. In this review we provide an extensive and detailed overview of the key physical and technical aspects of MWA and of the currently available systems, and we want to discuss the most relevant published data on MWA treatments of HCC nodules in regard to clinical results and to the type and rate of complications, both in absolute terms and in comparison with RFA. PMID:26557950

Benign thyroid nodule unresponsive to radiofrequency ablation treated with laser ablation: a case report.

PubMed

Oddo, Silvia; Balestra, Margherita; Vera, Lara; Giusti, Massimo

2018-05-11

Radiofrequency ablation and laser ablation are safe and effective techniques for reducing thyroid nodule volume, neck symptoms, and cosmetic complaints. Therapeutic success is defined as a nodule reduction > 50% between 6 and 12 months after the procedure, but a percentage of nodules inexplicably do not respond to thermal ablation. We describe the case of a young Caucasian woman with a solid benign thyroid nodule who refused surgery and who had undergone radiofrequency ablation in 2013. The nodule did not respond in terms of either volume reduction or improvement in neck symptoms. After 2 years, given the patient's continued refusal of thyroidectomy, we proposed laser ablation. The nodule displayed a significant volume reduction (- 50% from radiofrequency ablation baseline volume, - 57% from laser ablation baseline), and the patient reported a significant improvement in neck symptoms (from 6/10 to 1/10 on a visual analogue scale). We conjecture that some benign thyroid nodules may be intrinsically resistant to necrosis when one specific ablation technique is used, but may respond to another technique. To the best of our knowledge, this is the first description of the effect of performing a different percutaneous ablation technique in a nodule that does not respond to radiofrequency ablation.

Laser ablation for the synthesis of carbon nanotubes

NASA Technical Reports Server (NTRS)

Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

2010-01-01

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of side pumped, preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

NASA Technical Reports Server (NTRS)

Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

2012-01-01

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

DOEpatents

Holloway, Brian C; Eklund, Peter C; Smith, Michael W; Jordan, Kevin C; Shinn, Michelle

2012-11-27

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation for the synthesis of carbon nanotubes

DOEpatents

Holloway, Brian C.; Eklund, Peter C.; Smith, Michael W.; Jordan, Kevin C.; Shinn, Michelle

2010-04-06

Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

Laser ablation in an ambient gas: Modelling and experiment

NASA Astrophysics Data System (ADS)

Moscicki, Tomasz; Hoffman, Jacek; Szymanski, Zygmunt

2018-02-01

The laser ablation of graphite in ambient argon is studied both experimentally and theoretically in conditions corresponding to the initial conditions of carbon nanotube synthesis by the laser vaporization method. The results of the experiment show that the maximum plasma temperature of 24 000 K is reached 25 ns after the beginning of the laser pulse and decreases to about 4000-4500 K after 10 μs. The maximum electron density of 8 × 1025 m-3 is reached 15 ns from the beginning of the laser pulse. The hydrodynamic model applied shows comparable plasma temperatures and electron densities. The model also replicates well a shock wave and plume confinement—intrinsic features of supersonic flow of the ablated plume in an ambient gas. The results show that the theoretical model can be used to simulate nanosecond laser ablation in an ambient gas from the beginning of the process up to several microseconds.

Femtosecond laser ablation of enamel

NASA Astrophysics Data System (ADS)

Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

2016-06-01

The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

Enceladus' Water Vapour Plumes

NASA Technical Reports Server (NTRS)

Hansen, Candice J.; Esposito, L.; Colwell, J.; Hendrix, A.; Matson, Dennis; Parkinson, C.; Pryor, W.; Shemansky, D.; Stewart, I.; Tew, J.;

COLD WEATHER PLUME STUDY

EPA Science Inventory

While many studies of power plant plume transport and transformation have been performed during the summer, few studies of these processes during the winter have been carried out. Accordingly, the U.S. Environmental Protection Agency and the Electric Power Research Institute join...

Improving operational plume forecasts

NASA Astrophysics Data System (ADS)

Balcerak, Ernie

2012-04-01

Forecasting how plumes of particles, such as radioactive particles from a nuclear disaster, will be transported and dispersed in the atmosphere is an important but computationally challenging task. During the Fukushima nuclear disaster in Japan, operational plume forecasts were produced each day, but as the emissions continued, previous emissions were not included in the simulations used for forecasts because it became impractical to rerun the simulations each day from the beginning of the accident. Draxler and Rolph examine whether it is possible to improve plume simulation speed and flexibility as conditions and input data change. The authors use a method known as a transfer coefficient matrix approach that allows them to simulate many radionuclides using only a few generic species for the computation. Their simulations work faster by dividing the computation into separate independent segments in such a way that the most computationally time consuming pieces of the calculation need to be done only once. This makes it possible to provide real-time operational plume forecasts by continuously updating the previous simulations as new data become available. They tested their method using data from the Fukushima incident to show that it performed well. (Journal of Geophysical Research-Atmospheres, doi:10.1029/2011JD017205, 2012)

Evaluation of Visible Plumes.

ERIC Educational Resources Information Center

Brennan, Thomas

Developed for presentation at the 12th Conference on Methods in Air Pollution and Industrial Hygiene Studies, University of Southern California, April, 1971, this outline discusses plumes with contaminants that are visible to the naked eye. Information covers: (1) history of air pollution control regulations, (2) need for methods of evaluating…

PLUME and research sotware

NASA Astrophysics Data System (ADS)

Baudin, Veronique; Gomez-Diaz, Teresa

2013-04-01

The PLUME open platform (https://www.projet-plume.org) has as first goal to share competences and to value the knowledge of software experts within the French higher education and research communities. The project proposes in its platform the access to more than 380 index cards describing useful and economic software for this community, with open access to everybody. The second goal of PLUME focuses on to improve the visibility of software produced by research laboratories within the higher education and research communities. The "development-ESR" index cards briefly describe the main features of the software, including references to research publications associated to it. The platform counts more than 300 cards describing research software, where 89 cards have an English version. In this talk we describe the theme classification and the taxonomy of the index cards and the evolution with new themes added to the project. We will also focus on the organisation of PLUME as an open project and its interests in the promotion of free/open source software from and for research, contributing to the creation of a community of shared knowledge.

Plume Impingement Analysis for the European Service Module Propulsion System

NASA Technical Reports Server (NTRS)

Yim, John Tamin; Sibe, Fabien; Ierardo, Nicola

2014-01-01

Plume impingement analyses were performed for the European Service Module (ESM) propulsion system Orbital Maneuvering System engine (OMS-E), auxiliary engines, and reaction control system (RCS) engines. The heat flux from plume impingement on the solar arrays and other surfaces are evaluated. This information is used to provide inputs for the ESM thermal analyses and help determine the optimal configuration for the RCS engines.

Enceladus Plume Movie

NASA Image and Video Library

2005-12-06

Jets of icy particles burst from Saturn’s moon Enceladus in this brief movie sequence of four images taken on Nov. 27, 2005. The sensational discovery of active eruptions on a third outer solar system body (Io and Triton are the others) is surely one of the great highlights of the Cassini mission. Imaging scientists, as reported in the journal Science on March 10, 2006, believe that the jets are geysers erupting from pressurized subsurface reservoirs of liquid water above 273 degrees Kelvin (0 degrees Celsius). Images taken in January 2005 appeared to show the plume emanating from the fractured south polar region of Enceladus, but the visible plume was only slightly brighter than the background noise in the image, because the lighting geometry was not suitable to reveal the true details of the feature. This potential sighting, in addition to the detection of the icy particles in the plume by other Cassini instruments, prompted imaging scientists to target Enceladus again with exposures designed to confirm the validity of the earlier plume sighting. The new views show individual jets, or plume sources, that contribute to the plume with much greater visibility than the earlier images. The full plume towers over the 505-kilometer-wide (314-mile) moon and is at least as tall as the moon's diameter. The four 10-second exposures were taken over the course of about 36 minutes at approximately 12 minute intervals. Enceladus rotates about 7.5 degrees in longitude over the course of the frames, and most of the observed changes in the appearances of the jets is likely attributable to changes in the viewing geometry. However, some of the changes may be due to actual variation in the flow from the jets on a time scale of tens of minutes. Additionally, the shift of the sources seen here should provide information about their location in front of and behind the visible limb (edge) of Enceladus. These images were obtained using the Cassini spacecraft narrow-angle camera at

Combined treatment of tyrosine kinase inhibitor labeled gold nanorod encapsulated albumin with laser thermal ablation in a renal cell carcinoma model

USDA-ARS?s Scientific Manuscript database

This manuscript served to characterize and evaluate Human Serum Albumin-encapsulated Nanoparticles (NPs) for drug delivery of a tyrosine kinase inhibitor combined with induction of photothermal ablation (PTA) combination therapy of Renal Cell Carcinoma (RCC). RCC is the most common type of kidney c...

Photodynamic therapy with Photofrin followed by thermal ablation for elimination of dysplasia and early cancer in Barrett's esophagus: follow-up in 100 patients

NASA Astrophysics Data System (ADS)

Panjehpour, Masoud; Overholt, Bergein F.; Haydek, John M.

1998-05-01

Photodynamic therapy (PDT) using Photofrin and 630 nm laser light was used to treat 100 Barrett's esophagus patients with dysplasia and early cancer. Twelve patients had superficial esophageal cancers (T1-T2, NO, MO). Laser light was delivered to the esophageal mucosa by cylindrical diffuser inserted through the endoscope or via a 3, 5 or 7 cm windowed esophageal centering balloons. Nd:YAG laser ablation was used on small residual islands of Barrett's mucosa during long term follow-up after PDT. Patients were maintained on omeprazole and were followed for 6 - 84 months following photodynamic therapy. Photodynamic therapy produced destruction of normal, dysplastic and malignant mucosa in treated areas. Approximately 75 - 80% of treated Barrett's mucosa healed as normal squamous epithelium in all patients. Complete elimination of Barrett's epithelium was found in 43 patients. Nd:YAG laser was required to ablate small residual areas of Barrett's mucosa in 35 of these patients. Dysplasia was eliminated in 77 patients. Ten of the 12 malignancies were ablated with no recurrence being found during follow-up. Healing was associated with esophageal strictures in 34% but after using the 5 and 7 cm balloons, the incidence of strictures decreased to 18%. All strictures were treated successfully by dilation. In summary, PDT alone or combined with Nd:YAG laser ablation, in conjunction with long-term acid inhibition provides an effective endoscopic treatment to eliminate dysplasia and superficial cancer in Barrett's patients, and reduce the amount of or eliminate Barrett's mucosa completely.

Femtosecond laser ablation of the stapes

NASA Astrophysics Data System (ADS)

McCaughey, Ryan G.; Sun, Hui; Rothholtz, Vanessa S.; Juhasz, Tibor; Wong, Brian J. F.

2009-03-01

A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations.

Effects of Laser Wavelength on Ablator Testing

NASA Technical Reports Server (NTRS)

White, Susan M.

2014-01-01

Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

Plasma ignition thresholds in UV laser ablation plumes

NASA Astrophysics Data System (ADS)

Clarke, P.; Dyer, P. E.; Key, P. H.; Snelling, H. V.

Ultraviolet (UV) laser thresholds for plasma ignition on solid targets predicted from electron-neutral collisional heating are generally much higher than those observed experimentally. This inconsistency was reconciled by Rosen, et al. [2], who showed that excited-state photoionization played a key role in long-pulse UV laser breakdown. Here we develop a related model but with emphasis on pulses of 10 ns duration. Experimental results are also reported for titanium, copper, silicon, and ferulic acid targets in vacuum, irradiated with combinations of the XeF, KrF, and ArF lasers for comparison with predictions.

Emerging needle ablation technology in urology.

PubMed

Leveillee, Raymond J; Pease, Karli; Salas, Nelson

2014-01-01

Thermal ablation of urologic tumors in the form of freezing (cryoablation) and heating (radiofrequency ablation) have been utilized successfully to treat and ablate soft tissue tumors for over 15 years. Multiple studies have demonstrated efficacy nearing that of extirpative surgery for certain urologic conditions. There are technical limitations to their speed and safety profile because of the physical limits of thermal diffusion. Recently, there has been a desire to investigate other forms of energy in an effort to circumvent the limitations of cryoblation and radiofrequency ablation. This review will focus on three relatively new energy applications as they pertain to tissue ablation: microwave, irreversible electroporation, and water vapor. High-intensity-focused ultrasound nor interstitial lasers are discussed, as there have been no recently published updates. Needle and probe-based ablative treatments will continue to play an important role. As three-dimensional imaging workstations move from the advanced radiologic interventional suite to the operating room, surgeons will likely still play a pivotal role in the +-application of these probe ablative devices. It is essential that the surgeon understands the fundamentals of these devices in order to optimize their application.

Formation and dynamics of plasma bullets in a non-thermal plasma jet: influence of the high-voltage parameters on the plume characteristics

NASA Astrophysics Data System (ADS)

Jarrige, Julien; Laroussi, Mounir; Karakas, Erdinc

2010-12-01

Non-thermal plasma jets in open air are composed of ionization waves commonly known as 'plasma bullets' propagating at high velocities. We present in this paper an experimental study of plasma bullets produced in a dielectric barrier discharge linear-field reactor fed with helium and driven by microsecond high-voltage pulses. Two discharges were produced between electrodes for every pulse (at the rising and falling edge), but only one bullet was generated. Fast intensified charge coupled device camera imaging showed that bullet velocity and diameter increase with applied voltage. Spatially resolved optical emission spectroscopy measurements provided evidence of the hollow structure of the jet and its contraction. It was shown that the pulse amplitude significantly enhances electron energy and production of active species. The plasma bullet appeared to behave like a surface discharge in the tube, and like a positive streamer in air. A kinetics mechanism based on electron impact, Penning effect and charge transfer reactions is proposed to explain the propagation of the ionization front and temporal behavior of the radiative species.

Eiffel Tower Plume

NASA Image and Video Library

2015-08-31

A single plume of plasma, many times taller than the diameter of Earth, rose up from the Sun, twisted and spun around, all the while spewing streams of particles for over two days (Aug. 17-19, 2015) before breaking apart. At times, its shape resembled the Eiffel Tower. Other lesser plumes and streams of particles can be seen dancing above the solar surface as well. The action was observed in a wavelength of extreme ultraviolet light. Credit: NASA/Goddard/SDO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Nanotechnology combined therapy: tyrosine kinase-bound gold nanorod and laser thermal ablation produce a synergistic higher treatment response of renal cell carcinoma in a murine model.

PubMed

Liu, James; Abshire, Caleb; Carry, Connor; Sholl, Andrew B; Mandava, Sree Harsha; Datta, Amrita; Ranjan, Manish; Callaghan, Cameron; Peralta, Donna V; Williams, Kristen S; Lai, Weil R; Abdel-Mageed, Asim B; Tarr, Matthew; Lee, Benjamin R

2017-02-01

To investigate tyrosine kinase inhibitors (TKI) and gold nanorods (AuNRs) paired with photothermal ablation in a human metastatic clear cell renal cell carcinoma (RCC) mouse model. Nanoparticles have been successful as a platform for targeted drug delivery in the treatment of urological cancers. Likewise, the use of nanoparticles in photothermal tumour ablation, although early in its development, has provided promising results. Our previous in vitro studies of nanoparticles loaded with both TKI and AuNRs and activated with photothermal ablation have shown significant synergistic cell kill greater than each individual arm alone. This study is a translation of our initial findings to an in vivo model. Immunologically naïve nude mice (athymic nude-Foxn1 nu ) were injected subcutaneously bilaterally in both flanks (n = 36) with 2.5 × 10 6 cells of a human metastatic renal cell carcinoma cell line (RCC 786-O). Subcutaneous xenograft tumours developed into 1-cm palpable nodules. AuNRs encapsulated in human serum albumin protein (HSA) nanoparticles were synthesised with or without a TKI and injected directly into the tumour nodule. Irradiation was administered with an 808-nm light-emitting diode laser for 6 min. Mice were humanely killed 14 days after irradiation; tumours were excised, formalin fixed, paraffin embedded, and evaluated for size and the percentage of necrosis by a genitourinary pathologist. The untreated contralateral flank tumours were used as controls. In mice that did not receive irradiation, TKI alone yielded 4.2% tumour necrosis on the injected side and administration of HSA-AuNR-TKI alone yielded 11.1% necrosis. In the laser-ablation models, laser ablation alone yielded 62% necrosis and when paired with HSA-AuNR there was 63.4% necrosis. The combination of laser irradiation and HSA-AuNR-TKI had cell kill rate of 100%. In the absence of laser irradiation, TKI treatment alone or when delivered via nanoparticles produced moderate necrosis. Irradiation

Response of mantle transition zone thickness to plume buoyancy flux

NASA Astrophysics Data System (ADS)

Das Sharma, S.; Ramesh, D. S.; Li, X.; Yuan, X.; Sreenivas, B.; Kind, R.

2010-01-01

The debate concerning thermal plumes in the Earth's mantle, their geophysical detection and depth characterization remains contentious. Available geophysical, petrological and geochemical evidence is at variance regarding the very existence of mantle plumes. Utilizing P-to-S converted seismic waves (P receiver functions) from the 410 and 660 km discontinuities, we investigate disposition of these boundaries beneath a number of prominent hotspot regions. The thickness of the mantle transition zone (MTZ), measured as P660s-P410s differential times (tMTZ), is determined. Our analyses suggest that the MTZ thickness beneath some hotspots correlates with the plume strength. The relationship between tMTZ, in response to the thermal perturbation, and the strength of plumes, as buoyancy flux B, follows a power law. This B-tMTZ behavior provides unprecedented insights into the relation of buoyancy flux and excess temperature at 410-660 km depth below hotspots. We find that the strongest hotspots, which are located in the Pacific, are indeed plumes originating at the MTZ or deeper. According to the detected power law, even the strongest plumes may not shrink the transition zone by significantly more than ~40 km (corresponding to a maximum of 300-400° excess temperature).

On possible plume-guided seismic waves

USGS Publications Warehouse

Julian, B.R.; Evans, J.R.

2010-01-01

Hypothetical thermal plumes in the Earth's mantle are expected to have low seismic-wave speeds and thus would support the propagation of guided elastic waves analogous to fault-zone guided seismic waves, fiber-optic waves, and acoustic waves in the oceanic SOund Fixing And Ranging channel. Plume-guided waves would be insensitive to geometric complexities in the wave guide, and their dispersion would make them distinctive on seismograms and would provide information about wave-guide structure that would complement seismic tomography. Detecting such waves would constitute strong evidence of a new kind for the existence of plumes. A cylindrical channel embedded in an infinite medium supports two classes of axially symmetric elastic-wave modes, torsional and longitudinal-radial. Torsional modes have rectilinear particle motion tangent to the cylinder surface. Longitudinal-radial modes have elliptical particle motion in planes that include the cylinder axis, with retrograde motion near the axis. The direction of elliptical particle motion reverses with distance from the axis: once for the fundamental mode, twice for the first overtone, and so on. Each mode exists only above its cut-off frequency, where the phase and group speeds equal the shear-wave speed in the infinite medium. At high frequencies, both speeds approach the shear-wave speed in the channel. All modes have minima in their group speeds, which produce Airy phases on seismograms. For shear wave-speed contrasts of a few percent, thought to be realistic for thermal plumes in the Earth, the largest signals are inversely dispersed and have dominant frequencies of about 0.1-1 Hz and durations of 15-30 sec. There are at least two possible sources of observable plume waves: (1) the intersection of mantle plumes with high-amplitude core-phase caustics in the deep mantle; and (2) ScS-like reflection at the core-mantle boundary of downward-propagating guided waves. The widespread recent deployment of broadband

Performance of Conformable Ablators in Aerothermal Environments

NASA Technical Reports Server (NTRS)

Thornton, J.; Fan, W.; Skokova, K.; Stackpoole, M.; Beck, R.; Chavez-Garcia, J.

2012-01-01

Conformable Phenolic Impregnated Carbon Ablator, a cousin of Phenolic Impregnated Carbon Ablator (PICA), was developed at NASA Ames Research Center as a lightweight thermal protection system under the Fundamental Aeronautics Program. PICA is made using a brittle carbon substrate, which has a very low strain to failure. Conformable PICA is made using a flexible carbon substrate, a felt in this case. The flexible felt significantly increases the strain to failure of the ablator. PICA is limited by its thermal mechanical properties. Future NASA missions will require heatshields that are more fracture resistant than PICA and, as a result, NASA Ames is working to improve PICAs performance by developing conformable PICA to meet these needs. Research efforts include tailoring the chemistry of conformable PICA with varying amounts of additives to enhance mechanical properties and testing them in aerothermal environments. This poster shows the performance of conformable PICA variants in arc jets tests. Some mechanical and thermal properties will also be presented.

Is the 'Fast Halo' around Hawaii as imaged in the PLUME experiment direct evidence for buoyant plume-fed asthenosphere?

NASA Astrophysics Data System (ADS)

Morgan, J. P.; Shi, C.; Hasenclever, J.

2010-12-01

An intriguing spatial pattern of variations in shear-wave arrival times has been mapped in the PLUME ocean bottom experiment (Wolfe et al., 2009) around Hawaii. The pattern consists of a halo of fast travel times surrounding a disk of slow arrivals from waves traveling up though the plume. We think it is directly sensing the pattern of dynamic uplift of the base of a buoyant asthenosphere - the buoyancy of the plume conduit lifting a 'rim' of the cooler, denser mantle that the plume rises through. The PLUME analysis inverted for lateral shear velocity variations beneath the lithosphere, after removing the assumed 1-D model velocity structure IASP91. They found that a slow plume-conduit extends to at least 1200 km below the Hawaiian hotspot. In this inversion the slow plume conduit is — quite surprisingly - surrounded by a fast wavespeed halo. A fast halo is impossible to explain as a thermal halo around the plume; this should lead to a slow wavespeed halo, not a fast one. Plume-related shearwave anisotropy also cannot simply explain this pattern — simple vertical strain around the plume conduit would result in an anisotropic slow shear-wavespeed halo, not a fast one. (Note the PLUME experiment’s uniform ‘fast-halo’ structure from 50-400km is likely to have strong vertical streaking in the seismic image; Pacific Plate-driven shear across a low-viscosity asthenosphere would be expected to disrupt and distort any cold sheet of vertical downwelling structure between 50-400km depths so that it would no longer be vertical as it is in the 2009 PLUME image with its extremely poor vertical depth control.) If the asthenosphere is plume-fed, hence more buoyant than underlying mantle, then there can be a simple explanation for this pattern. The anomaly would be due to faster traveltimes resulting from dynamic relief at the asthenosphere-mesosphere interface; uplift of the denser mesosphere by the buoyancy of the rising plume increases the distance a wave travels

[Clinical effect of ultrasound-guided injection of biodegradable poly(lactic-co-glycolic acid)-Fe3O4 in situ implant for magnetic thermal ablation in treatment of nude mice with human liver cancer SMMC-7721 cells].

PubMed

Liang, B; Zuo, G Q; Zheng, Y Y; He, S; Zuo, D Y

2016-12-20

-solid phase inversion could be monitored by ultrasound and CT. The detachment and incrustation of the tumor started at 2 days after treatment, the wound started to heal 15 days later, and the tumor tissue disappeared completely. Conclusion: Ultrasound-guided injection of biodegradable Fe 3 O 4 -PLGA in situ implant combined with magnetic thermal ablation can effectively treat human liver cancer SMMC-7721 cells in nude mice.

Mantle plumes and continental tectonics.

PubMed

Hill, R I; Campbell, I H; Davies, G F; Griffiths, R W

1992-04-10

Mantle plumes and plate tectonics, the result of two distinct modes of convection within the Earth, operate largely independently. Although plumes are secondary in terms of heat transport, they have probably played an important role in continental geology. A new plume starts with a large spherical head that can cause uplift and flood basalt volcanism, and may be responsible for regional-scale metamorphism or crustal melting and varying amounts of crustal extension. Plume heads are followed by narrow tails that give rise to the familiar hot-spot tracks. The cumulative effect of processes associated with tail volcanism may also significantly affect continental crust.

Preparation of TlBa2Ca2Cu3O9±δ high Tc thin films by laser ablation in combination with thermal evaporation of thallium oxide

NASA Astrophysics Data System (ADS)

Piehler, A.; Löw, R.; Betz, J.; Schönberger, R.; Renk, K. F.

1993-11-01

TlBa2Ca2Cu3O9±δ high Tc thin films were prepared on MgO <100> surfaces by a combination of laser ablation from a stoichiometric Ba2Ca2Cu3Ox target and the thermal evaporation of thallium oxide. X-ray diffraction measurements showed that the films consisted of predominantly c axis oriented TlBa2Ca2Cu3O9±δ, and scanning electron microscopy revealed that the surfaces had a flat, platelike morphology. The ac inductive measurements indicated that the onset of superconductivity occurred at 117 K with a transition width (10%-90%) of ˜3 K. Zero resistivity was reached at 120 K. The critical current density was ˜3×104 A/cm2 at 110 K.

The planet beyond the plume hypothesis

NASA Astrophysics Data System (ADS)

Smith, Alan D.; Lewis, Charles

1999-12-01

but not counterflow, though convergent margin geometry may still induce propagating fractures which set up melting anomalies. Lateral migration of asthenospheric domains allows the sources of Pacific intraplate volcanism to be traced back to continental mantle eroded during the breakup of Gondwana and the amalgamation of Asia in the Paleozoic. Intraplate volcanism in the South Pacific therefore has a common Gondwanan origin to intraplate volcanism in the South Atlantic and Indian Oceans, hence the DUPAL anomaly is entirely of shallow origin. Such domains constitute a second order geochemical heterogeneity superimposed on a streaky/marble-cake structure arising from remixing of subducted crust with the convecting mantle. During the Proterozoic and Phanerozoic, remixing of slabs has buffered the evolution of the depleted mantle to a rate of 2.2 ɛNd units Ga -1, with fractionation of Lu from Hf in the sediment component imparting the large range in 176Hf/ 177Hf relative to 143Nd/ 144Nd observed in MORB. Only the high ɛNd values of some Archean komatiites are compatible with derivation from unbuffered mantle. The existence of a very depleted reservoir is attributed to stabilisation of a large early continental crust through either obduction tectonics or slab melting regimes which reduced the efficiency of crustal recycling back into the mantle. Generation of komatiite is therefore a consequence of mantle composition, and is permitted in ocean ridge environments and/or under hydrous melting conditions. Correspondingly, as intraplate volcanism depends on survival of volatile-bearing sources, its appearance in the Middle Proterozoic corresponds to the time in the Earth's thermal evolution at which minerals such as phlogopite and amphibole could survive in off-ridge environments in the shallow asthenosphere. The geodynamic evolution of the Earth was thus determined at convergent margins, not by plumes and hotspots, with the decline in thermal regime causing both a reduction

Study of Mn laser ablation in methane atmosphere

NASA Astrophysics Data System (ADS)

Krstulović, N.; Labazan, I.; Milošević, S.

2006-02-01

Laser ablation of Mn target in vacuum and in the presence of CH4 was studied under 308 nm laser irradiation. Time-resolved emission using gated detection and scanning monochromator and absorption using the cavity ring-down spectroscopy were used to study vaporized plume. In the CH4 atmosphere we observed transitions identified as C2 and MnH bands, while these spectral features were not detected in emission spectra. This is a clear evidence of importance in combining both spectroscopic techniques in laser vaporized plume study.

Why the SL9 Plumes Were All About the Same Height

NASA Technical Reports Server (NTRS)

Zahnle, K.; MacLow, M.-M.; Cuzzi, Jeffery N. (Technical Monitor)

1995-01-01

Several of the SL9 ejecta plumes were observed by the HST to reach approximately the same height, about 3000 km above the jovian cloud tops. The duration of the infrared events, which were produced by the plume falling back on the atmosphere, measures time aloft and hence provides a second, more sensitive measure of plume height; the light curves indicate that the largest impacts produced modestly higher plumes. Evidently these plumes were launched with about the same vertical velocity, roughly 10-13 kilometers per second. As the impactors themselves were not all the same, nor the impacts equally luminous, nor the plumes equally opaque, the similar plume heights has been seen as a puzzle needing explanation. A second, closely related matter that needs to addressed quantitatively is the popular contention that a big plume requires a big impact. This view is misleading at best, yet plume heights can be used to constrain impact parameters. Dimensional analysis indicates that plume height goes as z alpha v (sup 2) (sub ej) alpha E/pH (sup 2), where v (sub ej) is the ejection velocity, E the explosion energy, and p and H the ambient pressure and scale height at termination. Using a semi-analytic model for the deceleration, disintegration, and destruction of intruding bodies by an ever-vigilant atmosphere, we find that the ratio E/pH(sup 2) is roughly constant for fragments with diameters of order 100 m to 1000 m. Constancy of v(sub ej) is in part due to the greater role of radiative ablation on the flight of smaller objects. We conclude that similar plume heights is a direct consequence of smaller impactors exploding at higher altitudes, in such a way that the different explosions were geometrically similar.