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Sample records for ablation zone dimensions

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

    NASA Astrophysics Data System (ADS)

    Wu, Po-hung; Brace, Chris L.

    2016-08-01

    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 was

  2. Interactive Volumetry Of Liver Ablation Zones

    NASA Astrophysics Data System (ADS)

    Egger, Jan; Busse, Harald; Brandmaier, Philipp; Seider, Daniel; Gawlitza, Matthias; Strocka, Steffen; Voglreiter, Philip; Dokter, Mark; Hofmann, Michael; Kainz, Bernhard; Hann, Alexander; Chen, Xiaojun; Alhonnoro, Tuomas; Pollari, Mika; Schmalstieg, Dieter; Moche, Michael

    2015-10-01

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive technique that destroys cancer cells by heat. The heat results from focusing energy in the radiofrequency spectrum through a needle. Amongst others, this can enable the treatment of patients who are not eligible for an open surgery. However, the possibility of recurrent liver cancer due to incomplete ablation of the tumor makes post-interventional monitoring via regular follow-up scans mandatory. These scans have to be carefully inspected for any conspicuousness. Within this study, the RF ablation zones from twelve post-interventional CT acquisitions have been segmented semi-automatically to support the visual inspection. An interactive, graph-based contouring approach, which prefers spherically shaped regions, has been applied. For the quantitative and qualitative analysis of the algorithm’s results, manual slice-by-slice segmentations produced by clinical experts have been used as the gold standard (which have also been compared among each other). As evaluation metric for the statistical validation, the Dice Similarity Coefficient (DSC) has been calculated. The results show that the proposed tool provides lesion segmentation with sufficient accuracy much faster than manual segmentation. The visual feedback and interactivity make the proposed tool well suitable for the clinical workflow.

  3. Interactive Volumetry Of Liver Ablation Zones

    PubMed Central

    Egger, Jan; Busse, Harald; Brandmaier, Philipp; Seider, Daniel; Gawlitza, Matthias; Strocka, Steffen; Voglreiter, Philip; Dokter, Mark; Hofmann, Michael; Kainz, Bernhard; Hann, Alexander; Chen, Xiaojun; Alhonnoro, Tuomas; Pollari, Mika; Schmalstieg, Dieter; Moche, Michael

    2015-01-01

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive technique that destroys cancer cells by heat. The heat results from focusing energy in the radiofrequency spectrum through a needle. Amongst others, this can enable the treatment of patients who are not eligible for an open surgery. However, the possibility of recurrent liver cancer due to incomplete ablation of the tumor makes post-interventional monitoring via regular follow-up scans mandatory. These scans have to be carefully inspected for any conspicuousness. Within this study, the RF ablation zones from twelve post-interventional CT acquisitions have been segmented semi-automatically to support the visual inspection. An interactive, graph-based contouring approach, which prefers spherically shaped regions, has been applied. For the quantitative and qualitative analysis of the algorithm’s results, manual slice-by-slice segmentations produced by clinical experts have been used as the gold standard (which have also been compared among each other). As evaluation metric for the statistical validation, the Dice Similarity Coefficient (DSC) has been calculated. The results show that the proposed tool provides lesion segmentation with sufficient accuracy much faster than manual segmentation. The visual feedback and interactivity make the proposed tool well suitable for the clinical workflow. PMID:26482818

  4. Perivascular parenchymal extension of the ablation zone following liver microwave ablation.

    PubMed

    Singh, Saurabh; Siriwardana, Pulathis Nilantha; Johnston, Edward William; Bandula, Steven; Davidson, Brian Ritchie; Illing, Rowland Oliver

    2016-03-31

    A 69-year-old man who presented with abdominal discomfort was, on examination, found to have a palpable abdominal mass. Contrast-enhanced CT showed a mass arising from the inferior vena cava, which biopsy confirmed to be a leiomyosarcoma. One month after chemoradiotherapy, CT demonstrated a new 15 mm solitary central right liver metastasis. Microwave ablation (MWA) of the metastasis was performed using an Acculis Sulis V system (Angiodynamics, USA) at a power of 140 Watts for 4 min, with no immediate complications. After 1 month, MRI with gadolinium was performed to assess the liver ablation zone. The MRI demonstrated thrombosis of a right inferior hepatic vein branch leading to the ablation zone and extension of the ablation zone 1 cm into the tissue around the thrombosed vessel.

  5. Microwave ablation at 10.0 GHz achieves comparable ablation zones to 1.9 GHz in ex vivo bovine liver.

    PubMed

    Luyen, Hung; Gao, Fuqiang; Hagness, Susan C; Behdad, Nader

    2014-06-01

    We demonstrate the feasibility of using high-frequency microwaves for tissue ablation by comparing the performance of a 10 GHz microwave ablation system with that of a 1.9 GHz system. Two sets of floating sleeve dipole antennas operating at these frequencies were designed and fabricated for use in ex vivo experiments with bovine livers. Combined electromagnetic and transient thermal simulations were conducted to analyze the performance of these antennas. Subsequently, a total of 16 ablation experiments (eight at 1.9 GHz and eight at 10.0 GHz) were conducted at a power level of 42 W for either 5 or 10 min. In all cases, the 1.9 and 10 GHz experiments resulted in comparable ablation zone dimensions. Temperature monitoring probes revealed faster heating rates in the immediate vicinity of the 10.0 GHz antenna compared to the 1.9 GHz antenna, along with a slightly delayed onset of heating farther from the 10 GHz antenna, suggesting that heat conduction plays a greater role at higher microwave frequencies in achieving a comparably sized ablation zone. The results obtained from these experiments agree very well with the combined electromagnetic/thermal simulation results. These simulations and experiments show that using lower frequency microwaves does not offer any significant advantages, in terms of the achievable ablation zones, over using higher frequency microwaves. Indeed, it is demonstrated that high-frequency microwave antennas may be used to create reasonably large ablation zones. Higher frequencies offer the advantage of smaller antenna size, which is expected to lead to less invasive interstitial devices and may possibly lead to the development of more compact multielement arrays with heating properties not available from single-element antennas.

  6. Microfabrication of Fresnel zone plates by laser induced solid ablation

    NASA Astrophysics Data System (ADS)

    Rodrigues, Vanessa R. M.; Thomas, John; Santhosh, Chidangil; Ramachandran, Hema; Mathur, Deepak

    2016-07-01

    A novel and simple single-step method of inscribing optical elements on metal-coated transparent substrates is demonstrated. Laser induced solid ablation (LISA) demands very low laser energies (nJ), as can be amply provided by a femtosecond laser oscillator. Here, LISA is used to write Fresnel zone plates on indium and tungsten coated glass. With up to 100 zones, remarkable agreement is obtained between measured and expected values of the focal length. LISA has enabled attainment of focal spot sizes that are 38% smaller than what would be obtained using conventional lenses of the same numerical aperture. The simplicity with which a high degree of automation can readily be achieved using LISA makes this cost-effective method amenable to a wide variety of applications related to microfabrication of optical elements.

  7. Three-dimension finite-element analyses of multiple electrodes bipolar RF global endometrial ablation

    NASA Astrophysics Data System (ADS)

    Hu, Tao; Panhao, Tang; Xiao, Jiahua

    2015-03-01

    Radio-frequency ablation (RFA) is a minimally invasive surgical procedure to thermally ablate the targeted diseased tissue. There have been many finite-element method (FEM) studies of cardiac and hepatic RFA, but hardly find any FEM study on endometrial ablation for abnormal uterine bleeding. In this paper, a FEM model was generated to analyze the temperature distribution of bipolar RF global endometrial ablation with three pairs of bipolar electrodes placed at the perimeter of the uterine cavity. COMSOL was utilized to calculate the RF electric fields and temperature fields by numerically solving the bioheat equation in the triangle uterine cavity range. The 55°C isothermal surfaces show the shape of the ablation dimensions (depth and width), which reasonably matched the experimental results.

  8. A methodology to analyze treatment zone geometry and variability of percutaneous thermal ablation

    NASA Astrophysics Data System (ADS)

    Keshava, Krishna N.; Kimia, Benjamin B.; Cook, Madeleine; Dupuy, Damian E.; Collins, Scott A.; Merck, Derek

    2015-03-01

    A major challenge for image guided tumor ablation is the high treatment variability due to heterogeneous tissue characteristics and thermal sinks. In this work, we present a methodology to analyze the geometry of the treatment zones and treatment zone variability. Our first contribution is an applicator centric co-ordinate system which enables us to compare treatment zones and vendor specifications across patients. Our second contribution is the analysis of the shape of the ablation zone using applicator centric longitudinal 2D cross sections. We present initial results of applying this methodology to analyze the geometry and variability in synthetic examples like ellipsoid, sphere and real microwave ablation zones in lung and liver.

  9. Heat-affected zone of metals ablated with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Hirayama, Yoichi; Obara, Minoru

    2003-07-01

    The melted area is found on the surface ablated by nanosecond and picosecond laser pulses. However, the heat effect is little on the ablated surface in the case of femtosecond laser due to non-thermal ablation process. Heat-affected zone of metallic bulk crystal ablated with femtosecond Ti:sapphire laser pulses is experimentally studied. As a result of XRD (X-ray diffraction) measurements, the XRD peak signal of the area ablated with Ti:sapphire laser becomes smaller than that of the crystalline metal sample. While the crystallinity of the metal sample is crystalline before the laser ablation, the crystallinity in the ablated area is partially changed into the amorphous form. Because the residual pulse energy that is not used for the ablation process remains, leading to the formation of thin layer of melt phase. The melt layer is abruptly cooled down not to be re-crystallized, but to transform into the amorphous form. It is evident that the area ablated with femtosecond laser is changed into the amorphous metal. Additionally XRD measurements and AR+ etching are performed alternately to measure the thickness of the amorphous layer. In the case of iron, the thickness is measured to be 1 μm approximately, therefore heat-affected zone is quite small.

  10. Molecular dynamics simulation of heat-affected zone of copper metal ablated with femtosecond laser

    NASA Astrophysics Data System (ADS)

    Hirayama, Yoichi; Obara, Minoru

    2005-03-01

    Femtosecond laser ablation of materials with high thermal conductivity is of paramount importance, because the chemical composition and properties of the area ablated with femtosecond laser are kept unchanged. The material processing by femtosecond laser can well control the heat-affected zone, compared to nanosecond laser ablation. We report on the heat-affected zone of crystalline copper (Cu) by use of femtosecond laser experimentally and theoretically. Laser ablation of Cu is investigated theoretically by two temperature model and molecular dynamics (MD) simulation. The MD simulation takes into account of electron temperature and thermal diffusion length calculated by two temperature model. The dependence of lattice temperature on time and depth is calculated by the MD simulation and two temperature model. The heat-affected zone estimated from the temperature is mainly studied and calculated to be 3 nm at 0.02 J/cm2 which is below the threshold fluence of 0.137 J/cm2. In addition, the thickness of heat-affected zone of copper crystal ablated with femtosecond Ti:sapphire laser is experimentally studied. As a result of X-ray diffraction (XRD) of the ablated surface, the surface crystallinity is partially changed into disordered structure from crystal form. The residual energy left in the metal, which is not used for ablation, will induce liquid phase, leading to the amorphous phase of the metal during resolidification. The thickness of heat-affected zone depends on laser fluence and is experimentally measured to be less than 1 μm at higher laser fluences than the ablation threshold.

  11. Analysis of laser ablation dynamics of CFRP in order to reduce heat affected zone

    NASA Astrophysics Data System (ADS)

    Sato, Yuji; Tsukamoto, Masahiro; Nariyama, Tatsuya; Nakai, Kazuki; Matsuoka, Fumihiro; Takahashi, Kenjiro; Masuno, Shinichiro; Ohkubo, Tomomasa; Nakano, Hitoshi

    2014-03-01

    A carbon fiber reinforced plastic [CFRP], which has high strength, light weight and weather resistance, is attractive material applied for automobile, aircraft and so on. The laser processing of CFRP is one of suitable way to machining tool. However, thermal affected zone was formed at the exposure part, since the heat conduction property of the matrix is different from that of carbon fiber. In this paper, we demonstrated that the CFRP plates were cut with UV nanosecond laser to reduce the heat affected zone. The ablation plume and ablation mass were investigated by laser microscope and ultra-high speed camera. Furthermore, the ablation model was constructed by energy balance, and it was confirmed that the ablation rate was 0.028 μg/ pulse in good agreement with the calculation value of 0.03 μg/ pulse.

  12. Modeling bimodal vessel effects on radio and microwave frequency ablation zones.

    PubMed

    Brannan, Joseph D; Ladtkow, Casey M

    2009-01-01

    A bench liver model is presented that separates the thermal and electrical effects of large blood vessels within radio and microwave frequency ablation boundaries. The model includes a cylindrical tissue environment with a 5 mm vessel placed parallel to and 15 mm way from either a Covidien Energy-based Devices Evident MW Ablation Percutaneous Antenna or a CoolTip RF Ablation Single Electrode Kit. An array of fiber optic thermal probes is used to monitor radial temperature profile on the vessel and non-vessel sides of the ablation zone. Circulating blood exhibits higher electrical conductivity than surrounding liver tissue and provides a significant means for transport of thermal energy. Data from the thermal probes indicate key performance differentiators between MW and RF ablation modalities when they are used next to large blood vessels clarifying the difference between thermal and electrical energy sink. The results suggest RFA is susceptible to both the thermal and electrical energy sink effects of large vasculature while MWA is only susceptible to thermal sink. Ablation zone boundaries were distorted on both the vessel and non-vessel sides with RFA whereas with MWA only the vessel side is affected.

  13. Radiofrequency Ablation of Lung Tumors: Imaging Features of the Postablation Zone

    PubMed Central

    Eradat, Jilbert; Gutierrez, Antonio J.; Lee, Christopher; Fishbein, Michael C.; Suh, Robert D.

    2012-01-01

    Radiofrequency ablation (RFA) is used to treat pulmonary malignancies. Although preliminary results are suggestive of a survival benefit, local progression rates are appreciable. Because a patient can undergo repeat treatment if recurrence is detected early, reliable post-RFA imaging follow-up is critical. The purpose of this article is to describe (a) an algorithm for post-RFA imaging surveillance; (b) the computed tomographic (CT) appearance, size, enhancement, and positron emission tomographic (PET) metabolic activity of the ablation zone; and (c) CT, PET, and dual-modality imaging with PET and CT (PET/CT) features suggestive of partial ablation or tumor recurrence and progression. CT is routinely used for post-RFA follow-up. PET and PET/CT have emerged as auxiliary follow-up techniques. CT with nodule densitometry may be used to supplement standard CT. Post-RFA follow-up was divided into three phases: early (immediately after to 1 week after RFA), intermediate (>1 week to 2 months), and late (>2 months). CT and PET imaging features suggestive of residual or recurrent disease include (a) increasing contrast material uptake in the ablation zone (>180 seconds on dynamic images), nodular enhancement measuring more than 10 mm, any central enhancement greater than 15 HU, and enhancement greater than baseline anytime after ablation; (b) growth of the RFA zone after 3 months (compared with baseline) and definitely after 6 months, peripheral nodular growth and change from ground-glass opacity to solid opacity, regional or distant lymph node enlargement, and new intrathoracic or extrathoracic disease; and (c) increased metabolic activity beyond 2 months, residual activity centrally or at the ablated tumor, and development of nodular activity. © RSNA, 2012 PMID:22786987

  14. Sustained Growth of the Ex Vivo Ablation Zones' Critical Short Axis Using Gas-cooled Radiofrequency Applicators

    SciTech Connect

    Rempp, Hansjoerg; Scharpf, Marcus; Voigtlaender, Matthias; Schraml, Christina; Schmidt, Diethard; Fend, Falko; Claussen, Claus D.; Enderle, Markus D.; Pereira, Philippe L.; Clasen, Stephan

    2011-02-15

    Purpose: To evaluate the ablation zones created with a gas-cooled bipolar radiofrequency applicator performed on ex vivo bovine liver tissue. Materials and Methods: A total of 320 ablations with an internally gas-cooled bipolar radiofrequency applicator were performed on fresh ex vivo bovine liver tissue, varying the ablation time (5, 10, 15, and 20 min), power (20, 30, 40, and 50 W), and gas pressure of the CO{sub 2} used for cooling (585, 600, 615, 630, 645 psi), leading to a total of 80 different parameter combinations. Size and shape of the white coagulation zone were assessed. Results: The largest complete ablation zone was achieved after 20 min of implementing 50 W and 645 psi, resulting in a short axis of mean 46 {+-} 1 mm and a long axis of 56 {+-} 2 mm (mean {+-} standard deviation). Short-axis diameters increased between 5 and 20 min of ablation time at 585 psi (increase of the short axis was 45% at 30 W, 29% at 40 W, and 39% at 50 W). This increase was larger at 645 psi (113% at 30 W, 67% at 40 W, and 70% at 50 W). Macroscopic assessment and NADH (nicotinamide adenine dinucleotide) staining revealed incompletely ablated tissue along the needle track in 18 parameter combinations including low-power settings (20 and 30 W) and different cooling levels and ablation times. Conclusion: Gas-cooled radiofrequency applicators increase the short-axis diameter of coagulation in an ex vivo setting if appropriate parameters are selected.

  15. “Edgeboost”: A Novel Technique to Extend the Ablation Zone Lateral to a Two-Probe Bipolar Radiofrequency Device

    SciTech Connect

    Huo, Ya Ruth Pillai, Krishna Akhter, Javed Morris, David L.

    2016-01-15

    BackgroundThe dual-electrode bipolar-RFA (B-RFA) is increasingly used to ablate large liver tumours (3–7 cm). However, the challenging aspect of B-RFA is the placement of the two electrodes around the tumour. Realignment often requires the electrodes to be extracted and reinserted.AimThe aim of this study is to examine “Edgeboost”, a novel technique to increase the lateral ablation dimension without requiring any realignment of the electrodes.Methods and MaterialsAn egg-white model and an ex vivo calf liver model were used compare the standard bipolar mode ablation to Edgeboost-1 (reaching full impedance in bipolar mode initially, then cycling in unipolar mode between left and right probes) and Edgeboost-2 (similar to Edgeboost-1 but not reaching full impedance initially in bipolar mode in order to minimize charring and, thus, to increase total ablation time).ResultsA significantly larger outer lateral ablation dimension to the probe was achieved with Edgeboost-1 compared to the standard method in the liver model (1.14 cm, SD: 0.16 vs. 0.44 cm, SD: 0.24, p = 0.04). Edgeboost-2 achieved the largest outer lateral ablation dimension of 1.75 cm (SD: 0.35). A similar association was seen in the egg model. Edgeboost-2 almost doubled the mass ablated with standard bipolar alone (mass ratio: 1:1.94 in egg white and 1:1.84 in liver).ConclusionThis study demonstrates that the novel “Edgeboost” technique can increase the outer lateral ablation dimension without requiring the two inserted electrodes to be reinserted. This would be beneficial for interventionists who use the dual B-RFA.

  16. Measurements of the conduction-zone length and mass ablation rate in cryogenic direct-drive implosions on OMEGA

    SciTech Connect

    Michel, D. T.; Davis, A. K.; Goncharov, V. N.; Sangster, T. C.; Hu, S. X.; Igumenshchev, I. V.; Meyerhofer, D. D.; Seka, W.; Froula, D. H.

    2015-04-14

    Measurements of the conduction-zone length (110 ± 20 μm at t = 2.8 ns), the averaged mass ablation rate of the deuterated plastic (7.95 ± 0.3 μg/ns), shell trajectory, and laser absorption are made in direct-drive cryogenic implosions and are used to quantify the electron thermal transport through the conduction zone. Hydrodynamic simulations that use nonlocal thermal transport and cross-beam energy transfer models reproduce these experimental observables. Hydrodynamic simulations that use a time-dependent flux-limited model reproduce the measured shell trajectory and the laser absorption but underestimate the mass ablation rate by ~10% and the length of the conduction zone by nearly a factor of 2.

  17. Measurements of the Conduction-Zone Length and Mass Ablation Rate in Cryogenic Direct-Drive Implosions on OMEGA

    NASA Astrophysics Data System (ADS)

    Michel, D. T.; Davis, A. K.; Goncharov, V. N.; Sangster, T. C.; Hu, S. X.; Igumenshchev, I. V.; Meyerhofer, D. D.; Seka, W.; Froula, D. H.

    2015-04-01

    Measurements of the conduction-zone length (110 ±20 μ m at t =2.8 ns ), the averaged mass ablation rate of the deuterated plastic (7.95 ±0.3 μ g /ns ), shell trajectory, and laser absorption are made in direct-drive cryogenic implosions and are used to quantify the electron thermal transport through the conduction zone. Hydrodynamic simulations that use nonlocal thermal transport and cross-beam energy transfer models reproduce these experimental observables. Hydrodynamic simulations that use a time-dependent flux-limited model reproduce the measured shell trajectory and the laser absorption but underestimate the mass ablation rate by ˜10 % and the length of the conduction zone by nearly a factor of 2.

  18. Recurrent Polymorphic Ventricular Tachycardia Treated by Ablation of Purkinje Arborization within an Infarct Border-Zone

    PubMed Central

    Park, Kyoung-Min; Nam, Gi-Byoung; Choi, Kee-Joon; Kim, You-Ho

    2011-01-01

    A 70-year-old patient with 3-vessel coronary artery disease and a left ventricular aneurysm underwent coronary artery bypass grafting, together with a surgical anterior ventricular endocardial restoration (SAVER) procedure. Four days later, he suddenly developed recurrent sustained and nonsustained polymorphic ventricular tachycardia, preceded by monomorphic ventricular premature contractions, and did not respond to any antiarrhythmic drug, including lidocaine, esmolol, or amiodarone. Repeated electrical cardioversion procedures were performed (28 in total). Mapping was performed to target the earliest site of activation in the left ventricle during the ventricular premature contractions, a site where the premature beats were preceded by Purkinje potentials. That site was located along a scar border-zone. Ablation at that site resulted in the disappearance of the monomorphic ventricular premature contractions and in the complete suppression of the electrical storm. These findings appear to indicate that the area in which the Purkinje potentials were recorded along the scar border-zone played an important role in the mechanism of the polymorphic ventricular tachycardia after myocardial infarction. PMID:21720476

  19. Changes in ice geometry and supraglacial hydrology, Sermeq Avannarleq ablation zone, West Greenland

    NASA Astrophysics Data System (ADS)

    McLamb, W. S.; Colgan, W.; Phillips, T. P.; Abdalati, W.; Steffen, K.; Motyka, R. J.; Rajaram, H.

    2010-12-01

    Our study quantifies changes in ice geometry and surface hydrology within a ~30 by 50 km study area in the ablation zone of the Sermeq (Glacier) Avannarleq over the period 1985 to 2009. To investigate changes in surface hydrology, we compare a 1985 supraglacial topography map created by the Grønlands Geologiske Undersøgelse (GGU) accompanied by the panchromatic orthomosaic from which it was generated, and a 2009 panchromatic WorldView-1image of the same region. A 1985 digital elevation model (DEM) was created by manually digitizing the GGU map contour lines and performing a spline interpolation of these values into a 100 m spatial resolution DEM. Differencing the 1985 DEM from a 2009 ASTER DEM yields a mean thinning rate of 1.23 ± 1.29 m/a in the ablation zone and a mean thickening rate of 0.09 ± 1.29 m/a in the accumulation zone. Analysis of secondary DEM attributes suggests a significant increase (p < 0.05, t = 115.8, df = 128605) in mean surface slope from 2.12° in 1985 (σ 1.91°) to 2.68° in 2009 (σ 1.88°). From manual delineations of the ice sheet margin in both the 2009 WorldView-1 imagery and the 1985 GGU map, we calculate a mean rate of marginal recession (of predominately land terminating ice) of 9.4 ± 1.3 m/a. We quantify the distribution of supraglacial rivers in the southern 1/3 of our study area by classifying the regions that contain surface water (i.e. rivers) and those which do not. The classification algorithm is based on fuzzy set theory and user defined parameters to “defuzzify” unclear membership regions based on surrounding pixel values and density. Preliminary results of the river comparison between 1985 orthomosaic and 2009 WorldView-1 image suggest that the river system has been substantially reorganized in some areas, presumably due to increased crevassing and surface melt. In other areas, the locations of major river channels are persistent over the study time period, resulting in geographic variability of perennial stream

  20. Endometrial ablation

    MedlinePlus

    Hysteroscopy-endometrial ablation; Laser thermal ablation; Endometrial ablation-radiofrequency; Endometrial ablation-thermal balloon ablation; Rollerball ablation; Hydrothermal ablation; Novasure ablation

  1. FLIP: A method for adaptively zoned, particle-in-cell calculations of fluid in two dimensions

    SciTech Connect

    Brackbill, J.U.; Ruppel, H.M.

    1986-08-01

    A method is presented for calculating fluid flow in two dimensions using a full particle-in-cell representation on an adaptively zoned grid. The method has many interesting properties, among them an almost total absence of numerical dissipation and the ability to represent large variations in the data. The method is described using a standard formalism and its properties are illustrated by supersonic flow over a step and the interaction of a shock with a thin foil.

  2. Helicopter-based Photography for use in SfM over the West Greenland Ablation Zone

    NASA Astrophysics Data System (ADS)

    Mote, T. L.; Tedesco, M.; Astuti, I.; Cotten, D.; Jordan, T.; Rennermalm, A. K.

    2015-12-01

    Results of low-elevation high-resolution aerial photography from a helicopter are reported for a supraglacial watershed in West Greenland. Data were collected at the end of July 2015 over a supraglacial watershed terminating in the Kangerlussuaq region of Greenland and following the Utrecht University K-Transect of meteorological stations. The aerial photography reported here were complementary observations used to support hyperspectral measurements of albedo, discussed in the Greenland Ice sheet hydrology session of this AGU Fall meeting. A compact digital camera was installed inside a pod mounted on the side of the helicopter together with gyroscopes and accelerometers that were used to estimate the relative orientation. Continuous video was collected on 19 and 21 July flights, and frames extracted from the videos are used to create a series of aerial photos. Individual geo-located aerial photos were also taken on a 24 July flight. We demonstrate that by maintaining a constant flight elevation and a near constant ground speed, a helicopter with a mounted camera can produce 3-D structure of the ablation zone of the ice sheet at unprecedented spatial resolution of the order of 5 - 10 cm. By setting the intervalometer on the camera to 2 seconds, the images obtained provide sufficient overlap (>60%) for digital image alignment, even at a flight elevation of ~170m. As a result, very accurate point matching between photographs can be achieved and an extremely dense RGB encoded point cloud can be extracted. Overlapping images provide a series of stereopairs that can be used to create point cloud data consisting of 3 position and 3 color variables, X, Y, Z, R, G, and B. This point cloud is then used to create orthophotos or large scale digital elevation models, thus accurately displaying ice structure. The geo-referenced images provide a ground spatial resolution of approximately 6 cm, permitting analysis of detailed features, such as cryoconite holes, evolving small

  3. Evaluation of the energy transfer in the char zone during ablation. Part 2: In-depth response of ablative composites, volume 1. Ph.D. Thesis, 1975. Final Report

    NASA Technical Reports Server (NTRS)

    Pike, R. W.; Delvalle, E. G.

    1974-01-01

    The decomposition of ablative composites is described along with the transport phenomena of pyrolysis gases which result from the decomposition of these plastics as they flow through the porous char of char-forming ablators. The pyrolysis products are those formed by the thermal degradation of nylon-phenolic resin and silicone elastomer composites. Emphasis is placed on the nature and extent of chemical reactions of the pyrolysis products and the char, along with the energy absorbed by the combined pyrolysis and char zone. Chemical reactions with thermodynamically consistent kinetic data are determined in order to develop a realistic analysis for predicting the thermal performance of ablative heat shields.

  4. Impact of monsoonal rainfall on specific mass balance in ablation zone of Chhota Shigri Glacier in 2008, Himachal Pradesh, India

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Ramanathan, A.; Linda, A.; Wagnon, P.; Arnod, Y.; Jose, P. G.; Chevallier, P.

    2009-04-01

    The Mass Balance of the Chhota Shigri glacier (32.2°N, 77.5°E; 15.7 km2, 4050 to 6263m a.m.s.l., 9 km long) located in Lahaul and Spiti valley, Himachal Pradesh, India has been monitored from 2002 to 2008 using glaciological method. In 2008, an additional field survey during 3- 10th August was undertaken to understand the impact of monsoonal rainfall on specific mass balance at various points on the ablation zone of this glacier that is alternatively influenced by the Indian monsoon and the mid-latitude westerlies. Specific Annual Mass Balance is negative (0.93 mweq), Equilibrium Line Altitude (ELA) is 5120m and Accumulation Area Ratio (AAR) is 38% in the 2007-08 hydrological year. In 2008 data obtained from nearest Weather station at Keylong show that the monsoon hit the Spiti valley in the middle of June (15 days earlier than normal date ) .The results reveal that 70% of total specific mass balance occurred by the first week of August indicating that most of the melting occurred in the first half of ablation season, dominated by monsoonal rainfall. The rainfall may accelerate ablation rate by supplying ( heat ) energy even it is very low and exposing bare dirty ice thereby decreasing albedo. In part A of the glacier, the mean vertical gradient of ablation up to August 08 is 0.67 m w.e. 100 m-1 between 4350 and 4850 m a.s.l., (area free of debris) and for part B, it is 0.41 m w.e. 100 m-1 between 4600m a.s.l. and 5000m a.s.l. From August 08 up to 1st week of October, mean vertical gradient of the ablation for part A is 0.54m w.e. 100 m-1 and it is 0.61 m w.e. 100 m-1 in part B for the same altitude ranges. Below 4350m a.s.l. the whole glacier is covered by debris and the melting rate is significantly reduced. Overall, ablation rate is influenced by rainfall, incoming solar radiation and debris cover.

  5. The Annual Glaciohydrology Cycle in the Ablation Zone of the Greenland Ice Sheet: Part 1. Hydrology Model

    NASA Technical Reports Server (NTRS)

    Colgan, William; Rajaram, Harihar; Anderson, Robert; Steffen. Konrad; Phillips, Thomas; Zwally, H. Jay; Abdalati, Waleed

    2012-01-01

    We apply a novel one-dimensional glacier hydrology model that calculates hydraulic head to the tidewater-terminating Sermeq Avannarleq flowline of the Greenland ice sheet. Within a plausible parameter space, the model achieves a quasi-steady-state annual cycle in which hydraulic head oscillates close to flotation throughout the ablation zone. Flotation is briefly achieved during the summer melt season along a approx.17 km stretch of the approx.50 km of flowline within the ablation zone. Beneath the majority of the flowline, subglacial conduit storage closes (i.e. obtains minimum radius) during the winter and opens (i.e. obtains maximum radius) during the summer. Along certain stretches of the flowline, the model predicts that subglacial conduit storage remains open throughout the year. A calculated mean glacier water residence time of approx.2.2 years implies that significant amounts of water are stored in the glacier throughout the year. We interpret this residence time as being indicative of the timescale over which the glacier hydrologic system is capable of adjusting to external surface meltwater forcings. Based on in situ ice velocity observations, we suggest that the summer speed-up event generally corresponds to conditions of increasing hydraulic head during inefficient subglacial drainage. Conversely, the slowdown during fall generally corresponds to conditions of decreasing hydraulic head during efficient subglacial drainage.

  6. Radiofrequency Ablation of Liver Metastases-Software-Assisted Evaluation of the Ablation Zone in MDCT: Tumor-Free Follow-Up Versus Local Recurrent Disease

    SciTech Connect

    Keil, Sebastian Bruners, Philipp; Schiffl, Katharina; Sedlmair, Martin; Muehlenbruch, Georg; Guenther, Rolf W.; Das, Marco; Mahnken, Andreas H.

    2010-04-15

    The purpose of this study was to investigate differences in change of size and CT value between local recurrences and tumor-free areas after CT-guided radiofrequency ablation (RFA) of hepatic metastases during follow-up by means of dedicated software for automatic evaluation of hepatic lesions. Thirty-two patients with 54 liver metastases from breast or colorectal cancer underwent triphasic contrast-enhanced multidetector-row computed tomography (MDCT) to evaluate hepatic metastatic spread and localization before CT-guided RFA and for follow-up after intervention. Sixteen of these patients (65.1 {+-} 10.3 years) with 30 metastases stayed tumor-free (group 1), while the other group (n = 16 with 24 metastases; 62.0 {+-} 13.8 years) suffered from local recurrent disease (group 2). Applying an automated software tool (SyngoCT Oncology; Siemens Healthcare, Forchheim, Germany), size parameters (volume, RECIST, WHO) and attenuation were measured within the lesions before, 1 day after, and 28 days after RFA treatment. The natural logarithm (ln) of the quotient of the volume 1 day versus 28 days after RFA treament was computed: lnQ1//28/0{sub volume}. Analogously, ln ratios of RECIST, WHO, and attenuation were computed and statistically evaluated by repeated-measures ANOVA. One lesion in group 2 was excluded from further evaluation due to automated missegmentation. Statistically significant differences between the two groups were observed with respect to initial volume, RECIST, and WHO (p < 0.05). Furthermore, ln ratios corresponding to volume, RECIST, and WHO differed significantly between the two groups. Attenuation evaluations showed no significant differences, but there was a trend toward attenuation assessment for the parameter lnQ28/0{sub attenuation} (p = 0.0527), showing higher values for group 1 (-0.4 {+-} 0.3) compared to group 2 (-0.2 {+-} 0.2). In conclusion, hepatic metastases and their zone of coagulation necrosis after RFA differed significantly between tumor

  7. Radiofrequency ablation of liver metastases-software-assisted evaluation of the ablation zone in MDCT: tumor-free follow-up versus local recurrent disease.

    PubMed

    Keil, Sebastian; Bruners, Philipp; Schiffl, Katharina; Sedlmair, Martin; Mühlenbruch, Georg; Günther, Rolf W; Das, Marco; Mahnken, Andreas H

    2010-04-01

    The purpose of this study was to investigate differences in change of size and CT value between local recurrences and tumor-free areas after CT-guided radiofrequency ablation (RFA) of hepatic metastases during follow-up by means of dedicated software for automatic evaluation of hepatic lesions. Thirty-two patients with 54 liver metastases from breast or colorectal cancer underwent triphasic contrast-enhanced multidetector-row computed tomography (MDCT) to evaluate hepatic metastatic spread and localization before CT-guided RFA and for follow-up after intervention. Sixteen of these patients (65.1 + or - 10.3 years) with 30 metastases stayed tumor-free (group 1), while the other group (n = 16 with 24 metastases; 62.0 + or - 13.8 years) suffered from local recurrent disease (group 2). Applying an automated software tool (SyngoCT Oncology; Siemens Healthcare, Forchheim, Germany), size parameters (volume, RECIST, WHO) and attenuation were measured within the lesions before, 1 day after, and 28 days after RFA treatment. The natural logarithm (ln) of the quotient of the volume 1 day versus 28 days after RFA treament was computed: lnQ1//28/0(volume). Analogously, ln ratios of RECIST, WHO, and attenuation were computed and statistically evaluated by repeated-measures ANOVA. One lesion in group 2 was excluded from further evaluation due to automated missegmentation. Statistically significant differences between the two groups were observed with respect to initial volume, RECIST, and WHO (p < 0.05). Furthermore, ln ratios corresponding to volume, RECIST, and WHO differed significantly between the two groups. Attenuation evaluations showed no significant differences, but there was a trend toward attenuation assessment for the parameter lnQ28/0(attenuation) (p = 0.0527), showing higher values for group 1 (-0.4 + or - 0.3) compared to group 2 (-0.2 + or - 0.2). In conclusion, hepatic metastases and their zone of coagulation necrosis after RFA differed significantly between tumor

  8. Model of oscillatory zoning in two dimensions: simulation and mode analysis.

    PubMed

    Mues, Tanja; Heuer, Andreas; Burger, Martin; Lubashevsky, Ihor

    2010-05-01

    Oscillatory zoning (OZ) occurs in all major classes of minerals and also in a wide range of geological environments. It is caused by self-organization and describes fluctuations of the spatial chemical composition profile of the crystal. We present here a two-dimensional model of OZ based on our previous one-dimensional (1D) analysis and investigate whether the results of the 1D stability analysis remain valid. With the additional second dimension we were able to study the origin of the spatially homogeneous layer formation by linear stability analysis. Numerical solutions of the model are presented and the results of a Fourier analysis delivers a detailed understanding of the crystal growth behavior as well as the limits of the model. Effects beyond linear stability analysis are important to finally understand the final structure formation.

  9. Large and rapid melt-induced velocity changes in the ablation zone of the Greenland Ice Sheet.

    PubMed

    van de Wal, R S W; Boot, W; van den Broeke, M R; Smeets, C J P P; Reijmer, C H; Donker, J J A; Oerlemans, J

    2008-07-04

    Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years. The positive-feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades.

  10. Local recurrence of small cell lung cancer following radiofrequency ablation is induced by HIF-1α expression in the transition zone

    PubMed Central

    WAN, JUN; WU, WEI; ZHANG, RENQUAN

    2016-01-01

    Local recurrence of lung cancer following radiofrequency ablation (RFA) treatment is common. The aims of the present study were to assess how RFA treatment affects the growth of small cell lung cancer (SCLC) micrometastases in the transition zone (TZ) surrounding the ablated region and in the reference zones (RZs) of the ablated or unablated lobes and to identify the molecular mechanism(s) of lung cancer recurrence following RFA treatment. After lung micrometastases of human SCLCs had formed, RFA treatment was applied to the right upper lobe (RUL) of the lung in nude mice. Hypoxia inducible factor (HIF)-1α expression, proliferation and angiogenesis potential both in the TZ and RZ were evaluated over time. Separately, at day 1, 7 and 14 following RFA treatment, the growth of micrometastases showed an ~2-fold increase in the TZ compared to the RZ of the unablated lobe, as the right lower lobe (RLL) and the growth of micrometastases in the RZ of the RUL was also induced by RFA. In addition, accelerated tumor growth in the TZ was induced by HIF-1α, but was not associated with tissue angiogenesis potential. We concluded that local recurrences of SCLCs caused by overproliferation of micrometastases following RFA treatment were driven by HIF-1α, although angiogenesis was not the driving force in the TZ. PMID:26750332

  11. Measurements of the Conduction-Zone Length and Mass Ablation Rate to Study the Hydrodynamic Coupling in Cryogenic Direct-Drive Implosions on OMEGA

    NASA Astrophysics Data System (ADS)

    Michel, D. T.; Davis, A. K.; Goncharov, V. N.; Regan, S. P.; Sangster, T. C.; Epstein, R.; Hu, S. X.; Igumenshchev, I. V.; Meyerhofer, D. D.; Seka, W.; Froula, D. H.

    2015-11-01

    The ablation-front trajectory and the averaged mass ablation rate is measured in direct-drive cryogenic target implosions on the OMEGA Laser System by imaging the soft x rays emitted by the coronal plasma. The length of the conduction zone is determined by coupling x-ray and scattered-light measurements. These measurements are compared to hydrodynamic simulations to study the modeling of the hydrodynamic coupling for various beam and target radii. Reducing the beam focal-spot radius relative to the target radius is a method that is being studied to reduce cross-beam energy transfer and increase the hydrodynamic efficiency. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  12. Thermal Ablation of Lung Tissue: In Vivo Experimental Comparison of Microwave and Radiofrequency

    SciTech Connect

    Crocetti, Laura Bozzi, Elena; Faviana, Pinuccia; Cioni, Dania; Della Pina, Clotilde; Sbrana, Alberto; Fontanini, Gabriella; Lencioni, Riccardo

    2010-08-15

    This study was designed to compare feasibility, safety, and effectiveness of microwave (MW) ablation versus radiofrequency (RF) ablation of lung tissue in a rabbit model. Twenty New Zealand White rabbits were submitted to MW (n = 10, group A) or RF ablation (n = 10, group B). The procedures were performed with a prototype MW ablation device with a 1.6-cm radiating section antenna (Valleylab MW Ablation System) and with a 2-cm exposed-tip RF electrode (Cool-tip RF Ablation System). At immediate computed tomography increase in density, maximum diameters (D1-D3) of ablation zones were measured and ablation volume was calculated. Histopathologic assessment was performed 3 and 7 days after the procedure. Technical success was achieved in nine of 10 rabbits in each group. One death occurred in group B. Complications included pneumothorax (group A, n = 4; group B, n = 4), abscess (group A, n = 1; group B, n = 1), and thoracic wall burn (group A, n = 4). No significant differences were demonstrated in attenuation increase (P = 0.73), dimensions (P = 0.28, 0.86, 0.06, respectively, comparing D1-D3) and volume (P = 0.17). At histopathology, ablation zones were similar, with septal necrosis, edema, hemorrhage, and peripheral lymphocytic infiltrate. Complete thrombosis of more than 90% of vessels up to 2 mm in diameter was depicted at the periphery of the ablation zone in group A specimens. In group B specimens, complete thrombosis was depicted in 20% of vessels. Feasibility and safety of MW and RF ablation are similar in a lung rabbit model. MW ablation produces a greater damage to peripheral small vessels inducing thrombosis.

  13. Evaluation of fatigue process zone dimensions in notched specimens by two-step phase shifting interferometry technique

    NASA Astrophysics Data System (ADS)

    Muravsky, Leonid I.; Picart, Pascal; Kmet', Arkady B.; Voronyak, Taras I.; Ostash, Orest P.; Stasyshyn, Ihor V.

    2016-10-01

    A method for evaluation of fatigue process zone (FPZ) dimensions near a notch root in metal and alloy specimens by using a two-step phase shifting interferometry (TS PSI) technique is proposed. In comparison with other destructive and nondestructive methods evaluating the FPZ dimensions, it possesses higher accuracy and performance. The method uses a criterion for the FPZ dimensions definition based on an assumption that the surface roughness of notched specimens after cyclic loading reaches its maximum values at the FPZ boundary. To realize this method, first, a phase map (PM) of a total surface relief near a notch root is retrieved; second, roughness and waviness PMs are extracted from the retrieved total surface relief PM by using the TS PSI; and finally, a surface roughness parameter Ra spatial distribution is calculated according to the offered criterion and the FPZ size d* is defined. The FPZ size was measured for specimens made of low-carbon steel and aluminum alloys 2024-T6 and 7075-T3. Obtained experimental results have shown that the proposed criterion allows defining the FPZ size for notched specimens made of metals and alloys possessing high, moderate, and low plasticity.

  14. Modelling of transient river - aquifer exchange using pressure head and heat measurements: the hyporheic zone's dimension

    NASA Astrophysics Data System (ADS)

    Nuetzmann, Gunnar; Christian, Levers; Jörg, Lewandowski

    2010-05-01

    Water exchange processes in the floodplain of a lowland groundwater-surface water system are studied on the basis of a study site near Freienbrink, NE Germany. The surface water boundaries of this site are formed by an oxbow and the current bed of the river Spree, section Müggelspree. Surface and ground water levels and water temperatures were collected in 12 piezometers and 2 recording stage gauges of a 300 m long transect throughout a one-year-period. Due to water level fluctuations alternation of infiltration and exfiltration occurred. However, most of the time groundwater flux is directed into the river Spree and, river water infiltration events into the aquifer are usually short and of minor importance. Due to clogging of the oxbow bed with a mud layer of different thickness the hydraulic contact between the oxbow and the adjacent aquifer is heterogeneously distributed and partially marginal. These features are modelled quantitatively using SUTRA in order to simulate coupled ground water flow and heat transport. A two-dimensional vertical modelling approach along the piezometer transect is developed to study exchange processes close to the surface water bodies more in detail in order to quantify the hyporheic fluxes of both river sections and to identify the directions and quantities of mass and heat fluxes. With the results the following questions will be answered: (1) It is possible to identify and to quantify the hydraulic processes (in- and exfiltration) between both river sections and the aquifer? (2) How fast does the exchange between the surface water and the aquifer occur? (3) Is there a hyporheic zone between the river sections and the aquifer, where groundwater and surface water are mixed, and how much water and heat will be transferred through this zones?

  15. CT imaging during microwave ablation: Analysis of spatial and temporal tissue contraction

    SciTech Connect

    Liu, Dong; Brace, Christopher L.

    2014-11-01

    Purpose: To analyze the spatial distribution and temporal development of liver tissue contraction during high-temperature ablation by using intraprocedural computed tomography (CT) imaging. Methods: A total of 46 aluminum fiducial markers were positioned in a 60 × 45 mm grid, in a single plane, around a microwave ablation antenna in each of six ex vivo bovine liver samples. Ablations were performed for 10 min at 100 W. CT data of the liver sample were acquired every 30 s during ablation. Fiducial motion between acquisitions was tracked in postprocessing and used to calculate measures of tissue contraction and contraction rates. The spatial distribution and temporal evolution of contraction were analyzed. Results: Fiducial displacement indicated that the zone measured postablation was 8.2 ± 1.8 mm (∼20%) smaller in the radial direction and 7.1 ± 1.0 mm (∼10%) shorter in the longitudinal direction than the preablation tissue dimension. Therefore, the total ablation volume was reduced from its preablation value by approximately 45%. Very little longitudinal contraction was noted in the distal portion of the ablation zone. Central tissues contracted more than 60%, which was near an estimated limit of ∼70% based on initial water content. More peripheral tissues contracted only 15% in any direction. Contraction rates peaked during the first 60 s of heating with a roughly exponential decay over time. Conclusions: Ablation zones measured posttreatment are significantly smaller than the pretreatment tissue dimensions. Tissue contraction is spatially dependent, with the greatest effect occurring in the central ablation zone. Contraction rate peaks early and decays over time.

  16. Controlled reshaping of the front surface of the cornea through its full-area ablation outside of the optical zone with a Gaussian ArF excimer laser beam

    NASA Astrophysics Data System (ADS)

    Semchishen, A. V.; Semchishen, V. A.

    2014-01-01

    We studied in vitro the response of the topography of the cornea to its full-area laser ablation (the laser beam spot diameter is commensurable with the size of the interface) outside of the central zone with an excimer laser having a Gaussian fluence distribution across the beam. Subject to investigation were the topographically controlled surface changes of the anterior cornea in 60 porcine eyes with a 5 ± 1.25-diopter artificially induced astigmatism, the changes being caused by laser ablation of the stromal collagen in two 3.5-mm-dia. circular areas along the weaker astigmatism axis. Experimental relationships are presented between the actual astigmatism correction and the expected correction for the intact optical zones 1, 2, 3, and 4 mm in diameter. The data for each zone were approximated by the least-squares method with the function d = a + bx. The coefficient b is given with the root-mean-square error. The statistical processing of the data yielded the following results: d = (0.14 ± 0.037)x for the 1-mm-dia. optical zone, (1.10 ± 0.036)x for the 2-mm-dia. optical zone, (1.04 ± 0.020)x for the 3-mm-dia. optical zone, and (0.55 ± 0.04)x for the 4-mm-dia. optical zone. Full astigmatism correction was achieved with ablation effected outside of the 3-mm-dia. optical zone. The surface changes of the cornea are shown to be due not only to the removal of the corneal tissue, but also to the biomechanical topographic response of the cornea to its strain caused by the formation of a dense pseudomembrane in the ablation area.

  17. Infrared laser bone ablation

    SciTech Connect

    Nuss, R.C.; Fabian, R.L.; Sarkar, R.; Puliafito, C.A.

    1988-01-01

    The bone ablation characteristics of five infrared lasers, including three pulsed lasers (Nd:YAG, lambda = 1064 micron; Hol:YSGG, lambda = 2.10 micron; and Erb:YAG, lambda = 2.94 micron) and two continuous-wave lasers (Nd:YAG, lambda = 1.064 micron; and CO/sub 2/, lambda = 10.6 micron), were studied. All laser ablations were performed in vitro, using moist, freshly dissected calvarium of guinea pig skulls. Quantitative etch rates of the three pulsed lasers were calculated. Light microscopy of histologic sections of ablated bone revealed a zone of tissue damage of 10 to 15 micron adjacent to the lesion edge in the case of the pulsed Nd:YAG and the Erb:YAG lasers, from 20 to 90 micron zone of tissue damage for bone ablated by the Hol:YSGG laser, and 60 to 135 micron zone of tissue damage in the case of the two continuous-wave lasers. Possible mechanisms of bone ablation and tissue damage are discussed.

  18. No-Touch Radiofrequency Ablation: A Comparison of Switching Bipolar and Switching Monopolar Ablation in Ex Vivo Bovine Liver

    PubMed Central

    Chang, Won; Lee, Sang Min; Han, Joon Koo

    2017-01-01

    Objective To evaluate the feasibility, efficiency, and safety of no-touch switching bipolar (SB) and switching monopolar (SM) radiofrequency ablation (RFA) using ex vivo bovine livers. Materials and Methods A pork loin cube was inserted as a tumor mimicker in the bovine liver block; RFA was performed using the no-touch technique in the SM (group A1; 10 minutes, n = 10, group A2; 15 minutes, n = 10) and SB (group B; 10 minutes, n = 10) modes. The groups were compared based on the creation of confluent necrosis with sufficient safety margins, the dimensions, and distance between the electrode and ablation zone margin (DEM). To evaluate safety, small bowel loops were placed above the liver surface and 30 additional ablations were performed in the same groups. Results Confluent necroses with sufficient safety margins were created in all specimens. SM RFA created significantly larger volumes of ablation compared to SB RFA (all p < 0.001). The DEM of group B was significantly lower than those of groups A1 and A2 (all p < 0.001). Although thermal injury to the small bowel was noted in 90%, 100%, and 30% of the cases in groups A1, A2, and B, respectively, full depth injury was noted only in 60% of group A2 cases. Conclusion The no-touch RFA technique is feasible in both the SB and SM modes; however, SB RFA appears to be more advantageous compared to SM RFA in the creation of an ablation zone while avoiding the unnecessary creation of an adjacent parenchymal ablation zone or adjacent small bowel injuries. PMID:28246508

  19. Modeling and Validation of Microwave Ablations with Internal Vaporization

    PubMed Central

    Chiang, Jason; Birla, Sohan; Bedoya, Mariajose; Jones, David; Subbiah, Jeyam; Brace, Christopher L.

    2014-01-01

    Numerical simulation is increasingly being utilized for computer-aided design of treatment devices, analysis of ablation growth, and clinical treatment planning. Simulation models to date have incorporated electromagnetic wave propagation and heat conduction, but not other relevant physics such as water vaporization and mass transfer. Such physical changes are particularly noteworthy during the intense heat generation associated with microwave heating. In this work, a numerical model was created that integrates microwave heating with water vapor generation and transport by using porous media assumptions in the tissue domain. The heating physics of the water vapor model was validated through temperature measurements taken at locations 5, 10 and 20 mm away from the heating zone of the microwave antenna in homogenized ex vivo bovine liver setup. Cross-sectional area of water vapor transport was validated through intra-procedural computed tomography (CT) during microwave ablations in homogenized ex vivo bovine liver. Iso-density contours from CT images were compared to vapor concentration contours from the numerical model at intermittent time points using the Jaccard Index. In general, there was an improving correlation in ablation size dimensions as the ablation procedure proceeded, with a Jaccard Index of 0.27, 0.49, 0.61, 0.67 and 0.69 at 1, 2, 3, 4, and 5 minutes. This study demonstrates the feasibility and validity of incorporating water vapor concentration into thermal ablation simulations and validating such models experimentally. PMID:25330481

  20. Numerical design of RF ablation applicator for hepatic cancer treatment

    NASA Astrophysics Data System (ADS)

    Rakhmadi, Aditya; Basari

    2017-02-01

    Currently, cancer has become one of health problems that is difficult to be overcomed. This disease is not only difficult to be cured, but also to be detected and may cause death. For this reason, RF ablation treatment method is proposed to cure cancer. RF ablation therapy is a method in which an applicator is inserted into the body to kill cancer cells by heating the cells. The cancer cells are exposed to the temperature more than 60°C in short duration (few second to few minutes) so thus cell destruction occurs locally. For the sake of the successful treatment, a minimally invasive method is selected in order for perfect local temperature distribution in cancer cells can be achieved. In this paper, a coax-fed dipole-type applicator with interstitial irradiation technique is proposed aimed at RF ablation into hepatic cells. Numerical simulation is performed to obtain a suitable geometric dimension at operating frequency around 2.45 GHz, in order to localize the ablation area. The proposed applicator is inserted into a simple phantom representing an adult human body model in which normal and cancerous liver cells. The simulated results show that the proposed applicator is able to operate at center frequency of 2.355 GHz with blood droplet-type ablation zone and the temperature around the cancer cell by 60°C can be achieved.

  1. Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation

    PubMed Central

    Prakash, Punit; Salgaonkar, Vasant A.; Clif Burdette, E.; Diederich, Chris J.

    2012-01-01

    Purpose: To evaluate multiple applicator implant configurations of interstitial ultrasound devices for large volume ablation of liver tumors. Methods: A 3D bioacoustic-thermal model using the finite element method was implemented to assess multiple applicator implant configurations for thermal ablation with interstitial ultrasound energy. Interstitial applicators consist of linear arrays of up to four 10 mm-long tubular ultrasound transducers, each under separate and dynamic power control, enclosed within a water-cooled delivery catheter (2.4 mm OD). The authors considered parallel implants with two and three applicators (clustered configuration), spaced 2–3 cm apart, to simulate open surgical placement. In addition, the authors considered two applicator implants with applicators converging and diverging at angles of ∼20°, 30°, and 45° to simulate percutaneous placement. Heating experiments (10–15 min) were performed and compared against simulations employing the same experimental parameters. To estimate the performance of parallel, multiple applicator configurations in an in vivo setting, simulations were performed taking into account a range of blood perfusion levels (0, 5, 12, and 15 kg m−3 s−1) that may occur in tumors of varying vascularity. The impact of tailoring the power supplied to individual transducer elements along the length of applicators is explored for applicators inserted in non-parallel (converging and diverging) configurations. Thermal dose (t43 > 240 min) and temperature thresholds (T > 52 °C) were used to define the ablation zones, with dynamic changes to tissue acoustic and thermal properties incorporated within the model. Results: Experiments in ex vivo bovine liver yielded ablation zones ranging between 4.0–5.6 cm × 3.2–4.9 cm, in cross section. Ablation zone dimensions predicted by simulations with similar parameters to the experiments were in close agreement (within 5 mm). Simulations of in vivo heating showed that 15

  2. Catheter ablation.

    PubMed

    Fromer, M; Shenasa, M

    1991-02-01

    Catheter ablation is gaining increasing interest for the therapy of symptomatic, sustained arrhythmias of various origins. The scope of this review is to give an overview of the biophysical aspects and major characteristics of some of the most widely used energy sources in catheter ablation, e.g., the discharge of conventional defibrillators, modified defibrillators, laser light, and radiofrequency current application. Results from animal studies are considered to explain the basic mechanisms of catheter ablation. The recent achievements with the use of radiofrequency current to modify or ablate cardiac conduction properties are outlined in more detail.

  3. Rates of burial and exhumation of lawsonite blueschist/eclogite in subduction zones from in situ UV laser ablation 40Ar/39Ar phengite geochronology

    NASA Astrophysics Data System (ADS)

    Fornash, K.; Cosca, M. A.; Whitney, D. L.; Teyssier, C. P.

    2014-12-01

    Lawsonite eclogites and blueschists are accessible records of processes that occur at depth in subducting slabs and can therefore provide information about the chemical and physical evolution of subduction zones. In composite blueschist-eclogite terranes, blueschists may have formed (1) by prograde metamorphism (pre-eclogite), (2) at the same P-T conditions as eclogite-facies metamorphism as a result of differences in bulk composition, H2O content, or oxidation state, or (3) from retrogression of eclogite, e.g. during exhumation. Field and petrologic observations of lawsonite eclogite and blueschist in the Sivrihisar Massif, Turkey, suggest that some blueschist formed from eclogite during exhumation in the subduction channel, whereas results from thermobarometry suggest that some blueschist formed at the same P-T conditions as eclogite. To test the age, petrologic, and tectonic relationship of coexisting eclogite and blueschist, we applied in situ UV laser ablation 40Ar/39Ar phengite geochronology to eclogite- and blueschist-facies rocks representing different structural positions and displaying different phengite textures and coexisting mineral assemblages. Phengite from fresh lawsonite eclogite yield an age of 93 ± 2 Ma and have the narrowest spread in ages (<12 Ma) of any rock type analyzed. Retrogressed (epidote) eclogite yields a mean weighted age of 82 ± 2 Ma. In contrast to the tightly constrained ages obtained in eclogite pods, blueschists and blueschist-facies quartzite exhibit discrete age populations ranging from 82 Ma to 110 Ma. Deformed phengite clusters from lawsonite garnet blueschist record age populations at 82 Ma and 92 Ma. Phengite from lawsonite-garnet veins and glaucophane-rich margins of eclogite pods also record 92 Ma. Omphacite-bearing lawsonite blueschist and a blueschist-facies quartzite from the same structural position contain age populations at 97 Ma and 110 Ma. These results document a sequence of events from prograde blueschist

  4. Microwave Ablation Compared with Radiofrequency Ablation for Breast Tissue in an Ex Vivo Bovine Udder Model

    SciTech Connect

    Tanaka, Toshihiro; Westphal, Saskia; Isfort, Peter; Braunschweig, Till; Penzkofer, Tobias Bruners, Philipp; Kichikawa, Kimihiko; Schmitz-Rode, Thomas Mahnken, Andreas H.

    2012-08-15

    Purpose: To compare the effectiveness of microwave (MW) ablation with radiofrequency (RF) ablation for treating breast tissue in a nonperfused ex vivo model of healthy bovine udder tissue. Materials and Methods: MW ablations were performed at power outputs of 25W, 35W, and 45W using a 915-MHz frequency generator and a 2-cm active tip antenna. RF ablations were performed with a bipolar RF system with 2- and 3-cm active tip electrodes. Tissue temperatures were continuously monitored during ablation. Results: The mean short-axis diameters of the coagulation zones were 1.34 {+-} 0.14, 1.45 {+-} 0.13, and 1.74 {+-} 0.11 cm for MW ablation at outputs of 25W, 35W, and 45W. For RF ablation, the corresponding values were 1.16 {+-} 0.09 and 1.26 {+-} 0.14 cm with electrodes having 2- and 3-cm active tips, respectively. The mean coagulation volumes were 2.27 {+-} 0.65, 2.85 {+-} 0.72, and 4.45 {+-} 0.47 cm{sup 3} for MW ablation at outputs of 25W, 35W, and 45W and 1.18 {+-} 0.30 and 2.29 {+-} 0.55 cm{sup 3} got RF ablation with 2- and 3-cm electrodes, respectively. MW ablations at 35W and 45W achieved significantly longer short-axis diameters than RF ablations (P < 0.05). The highest tissue temperature was achieved with MW ablation at 45W (P < 0.05). On histological examination, the extent of the ablation zone in MW ablations was less affected by tissue heterogeneity than that in RF ablations. Conclusion: MW ablation appears to be advantageous with respect to the volume of ablation and the shape of the margin of necrosis compared with RF ablation in an ex vivo bovine udder.

  5. Thermal ablation.

    PubMed

    Webb, Heather; Lubner, Meghan G; Hinshaw, J Louis

    2011-04-01

    Image-guided tumor ablation refers to a group of treatment modalities that have emerged during the past 2 decades as important tools in the treatment of a wide range of tumors throughout the body. Although most widely recognized in the treatment of hepatic and renal malignancies, the role of thermal ablation has expanded to include lesions of the lung, breast, prostate, bone, as well as other organs and its clinical applications continue to increase. In the following article, we discuss the major thermal ablation modalities, their respective strengths and weaknesses, potential complications and how to avoid them, as well as possible future applications.

  6. Catheter Ablation

    MedlinePlus

    ... you during the procedure. Machines will measure your heart’s activity. All types of ablation require cardiac catheterization to place flexible tubes, or catheters, inside your heart to make the scars. Your doctor will clean ...

  7. Energy balance in the ablation zone during the summer season at the Gran Campo Nevado Ice Cap in the Southern Andes

    NASA Astrophysics Data System (ADS)

    Schneider, Christoph; Kilian, Rolf; Glaser, Michael

    2007-10-01

    The energy balance and ablation of Glaciar Lengua were investigated during the austral summer of 1999/2000. Glaciar Lengua is located in Patagonia, in the southernmost Andes of Chile (53°S), within an extremely maritime climate. The aim of this study was to gain insight into current energy fluxes at this location and to evaluate how the energy fluxes depend on meteorological variables. From February to April 2000 an automated weather station was operated on Glaciar Lengua. Ablation was measured repeatedly at stakes during the same period. The point energy balance was calculated using the bulk approach formulation. The effective roughness length was adjusted in order to calibrate the model to the measured ablation. It was revealed that sensible heat transfer is the major contribution to the energy balance adding 54% of the energy available for melt. Net radiation contributes only 35% to the overall energy balance. Minor contributors are the latent heat flux (7%) and the heat flux by precipitation (4%). The net radiation shows little variance from day to day. Cross-correlations of the daily mean values of the energy fluxes derived from the energy balance model and meteorological variables reveal that air temperature and wind speed are the key factors controlling the summer energy balance in the ablation area. Melt derived from a multiple regression model based on these two variables correlates with computed melt with a correlation coefficient of 0.92. From the measured ablation, a summer-time degree-day factor of 7.6 mm·°C - 1 was derived for the ablation area.

  8. [Ablative and fractional lasers].

    PubMed

    Beylot, C; Grognard, C; Michaud, T

    2009-10-01

    The use of pulsed or scanning Carbon Dioxide, and pulsed Erbium-YAG lasers allows the programmable and reproducible photocoagulation of thin layers of the epidermis and superficial dermis. Thermal damage depends on the type of laser and is greater with CO(2) lasers. The degree of neocollagenesis is proportional to the thermal damage and is better with CO(2) lasers. Their main indication is the correction of photoaged facial skin but they can also be used for corrective dermatology, e.g. for scars and genodermatosis. Results are highly satisfactory but the technique is invasive and the patient experiences a social hindrance of around two weeks. Fractionated techniques treat 25% of the defective skin area at each session in noncontiguous microzones; four sessions are therefore necessary to treat the entire cutaneous surface. The treatment is given under topical anesthesia and is much less invasive, particularly with nonablative fractional laser treatment in which photothermolysis does not penetrate below the epidermis and/or the effects are slight, with no or very little social isolation. However, the results are much less satisfactory than the results of ablative laser and there is no firming effect. Other zones than the face can be treated. With the fractional CO(2) and Erbium ablative lasers, which have multiplied over the past 2 years, the much wider impacts cause perforation of the epidermis and there is a zone of ablation by laser photovaporization, with a zone of thermal damage below. The results are better in correcting photoaging of the face, without, however, achieving the efficacy of ablative lasers, which remain the reference technique. However, the effects are not insignificant, requiring at least 5 days of social isolation.

  9. Features and dimensions of the Hayward Fault Zone in the Strawberry and Blackberry Creek Area, Berkeley, California

    SciTech Connect

    Williams, P.L.

    1995-03-01

    This report presents an examination of the geometry of the Hayward fault adjacent to the Lawrence Berkeley Laboratory and University of California campuses in central Berkeley. The fault crosses inside the eastern border of the UC campus. Most subtle geomorphic (landform) expressions of the fault have been removed by development and by the natural processes of landsliding and erosion. Some clear expressions of the fault remain however, and these are key to mapping the main trace through the campus area. In addition, original geomorphic evidence of the fault`s location was recovered from large scale mapping of the site dating from 1873 to 1897. Before construction obscured and removed natural landforms, the fault was expressed by a linear, northwest-tending zone of fault-related geomorphic features. There existed well-defined and subtle stream offsets and beheaded channels, fault scarps, and a prominent ``shutter ridge``. To improve our confidence in fault locations interpreted from landforms, we referred to clear fault exposures revealed in trenching, revealed during the construction of the Foothill Housing Complex, and revealed along the length of the Lawson Adit mining tunnel. Also utilized were the locations of offset cultural features. At several locations across the study area, distress features in buildings and streets have been used to precisely locate the fault. Recent published mapping of the fault (Lienkaemper, 1992) was principally used for reference to evidence of the fault`s location to the northwest and southeast of Lawrence Berkeley Laboratory.

  10. Probabilistic finite element analysis of radiofrequency liver ablation using the unscented transform

    PubMed Central

    dos Santos, Icaro; Haemmerich, Dieter; Schutt, David; da Rocha, Adson Ferreira; Menezes, Leonardo Rax

    2009-01-01

    The main limitation of radiofrequency (RF) ablation numerical simulations reported in the literature is their failure to provide statistical results based on the statistical variability of tissue thermal–electrical parameters. This work developed an efficient probabilistic approach to hepatic RF ablation in order to statistically evaluate the effect of four thermal–electrical properties of liver tissue on the uncertainty of the ablation zone dimensions: thermal conductivity, specific heat, blood perfusion and electrical conductivity. A deterministic thermal–electrical finite element model of a monopolar electrode inserted in the liver was coupled with the unscented transform method in order to obtain coagulation zone confidence intervals, probability and cumulative density functions. The coagulation zone volume, diameter and length were 10.96 cm3, 2.17 cm and 4.08 cm, respectively (P < 0.01). Furthermore, a probabilistic sensitivity analysis showed that perfusion and thermal conductivity account for >95% of the variability in coagulation zone volume, diameter and length. PMID:19124948

  11. Understanding Resilience Dimensions and Adaptive Strategies to the Impact of Recurrent Droughts in Borana Zone, Oromia Region, Ethiopia: A Grounded Theory Approach.

    PubMed

    Birhanu, Zewdie; Ambelu, Argaw; Berhanu, Negalign; Tesfaye, Abraraw; Woldemichael, Kifle

    2017-01-26

    Recurrent shocks and stresses are increasingly deteriorating pastoralist communities' resilience capacities in many aspects. A context specific resilience framework is essential to strengthen pastoralist community's resilience capacity towards the impact of recurrent drought. Hence, the present study was aimed to develop a context specific and data driven resilience building framework towards impacts of recurrent droughts in the case of Borana pastoralists in Ethiopia. Qualitative grounded theory approach was employed to guide the study process. The data were collected through focus group discussions and in-depth interviews in two drought affected districts of Borana Zone during October 2013. The analysis was assisted by ATLAS. ti 7.1.4. The analysis provided a context specific resilience building conceptual tool, which consists of, closely interconnected, eight dimensions operating at multiple capacities and levels: environment (underlying vulnerability factor); livestock, infrastructures/social services, and wealth (immediate causes and effects); community network/social capital, as well as governance, peace and security (support and enabling factors oriented), psychosocial, and human capital (as eventual outcomes and impacts). The resilience capacities of these pastoralist communities have been eroded, leaving them without sufficient and effective adaptive strategies. The emergent resilience framework can serve as a useful guidance to design context-specific interventions that makes the people and the system resilient to the impacts of recurrent droughts.

  12. Understanding Resilience Dimensions and Adaptive Strategies to the Impact of Recurrent Droughts in Borana Zone, Oromia Region, Ethiopia: A Grounded Theory Approach

    PubMed Central

    Birhanu, Zewdie; Ambelu, Argaw; Berhanu, Negalign; Tesfaye, Abraraw; Woldemichael, Kifle

    2017-01-01

    Recurrent shocks and stresses are increasingly deteriorating pastoralist communities’ resilience capacities in many aspects. A context specific resilience framework is essential to strengthen pastoralist community’s resilience capacity towards the impact of recurrent drought. Hence, the present study was aimed to develop a context specific and data driven resilience building framework towards impacts of recurrent droughts in the case of Borana pastoralists in Ethiopia. Qualitative grounded theory approach was employed to guide the study process. The data were collected through focus group discussions and in-depth interviews in two drought affected districts of Borana Zone during October 2013. The analysis was assisted by ATLAS. ti 7.1.4. The analysis provided a context specific resilience building conceptual tool, which consists of, closely interconnected, eight dimensions operating at multiple capacities and levels: environment (underlying vulnerability factor); livestock, infrastructures/social services, and wealth (immediate causes and effects); community network/social capital, as well as governance, peace and security (support and enabling factors oriented), psychosocial, and human capital (as eventual outcomes and impacts). The resilience capacities of these pastoralist communities have been eroded, leaving them without sufficient and effective adaptive strategies. The emergent resilience framework can serve as a useful guidance to design context-specific interventions that makes the people and the system resilient to the impacts of recurrent droughts. PMID:28134771

  13. Pellet ablation and ablation model development

    SciTech Connect

    Houlberg, W.A.

    1989-01-01

    A broad survey of pellet ablation is given, based primarily on information presented at this meeting. The implications of various experimental observations for ablation theory are derived from qualitative arguments of the physics involved. The major elements of a more complete ablation theory are then outlined in terms of these observations. This is followed by a few suggestions on improving the connections between theory and experimental results through examination of ablation data. Although this is a rather aggressive undertaking for such a brief (and undoubtedly incomplete) assessment, some of the discussion may help us advance the understanding of pellet ablation. 17 refs.

  14. Surgical Ablation of Atrial Fibrillation.

    PubMed

    Ramlawi, Basel; Abu Saleh, Walid K

    2015-01-01

    The Cox-maze procedure for the restoration of normal sinus rhythm, initially developed by Dr. James Cox, underwent several iterations over the years. The main concept consists of creating a series of transmural lesions in the right and left atria that disrupt re-entrant circuits responsible for propagating the abnormal atrial fibrillation rhythm. The left atrial appendage is excluded as a component of the Maze procedure. For the first three iterations of the Cox- maze procedure, these lesions were performed using a surgical cut-and-sew approach that ensured transmurality. The Cox-Maze IV is the most currently accepted iteration. It achieves the same lesion set of the Cox- maze III but uses alternative energy sources to create the transmural lesions, potentially in a minimally invasive approach on the beating heart. High-frequency ultrasound, microwave, and laser energy have all been used with varying success in the past. Today, bipolar radiofrequency heat or cryotherapy cooling are the most accepted sources for creating linear lesions with consistent safety and transmurality. The robust and reliable nature of these energy delivery methods has yielded a success rate reaching 90% freedom from atrial fibrillation at 12 months. Such approaches offer a significant long-term advantage over catheter-based ablation, especially in patients having longstanding, persistent atrial fibrillation with characteristics such as dilated left atrial dimensions, poor ejection fraction, and failed catheter ablation. Based on these improved results, there currently is significant interest in developing a hybrid ablation strategy that incorporates the superior transmural robust lesions of surgical ablation, the reliable stroke prevention potential of epicardial left atrial appendage exclusion, and sophisticated mapping and confirmatory catheter-based ablation technology. Such a minimally invasive hybrid strategy for ablation may lead to the development of multidisciplinary "Afib teams" to

  15. The Emprint™ Ablation System with Thermosphere™ Technology: One of the Newer Next-Generation Microwave Ablation Technologies

    PubMed Central

    Alonzo, Marc; Bos, Aaron; Bennett, Shelby; Ferral, Hector

    2015-01-01

    Microwave ablation is a recent development in the field of tumor ablation that uses electromagnetic waves to establish a microwave near-field with direct tissue heating. Some of the limitations of the earlier generation devices had been unpredictable size and shape of the ablation zones with changes in the surrounding tissue environment as well as differences across various different tissue types. The Emprint Ablation System with Thermosphere Technology (Covidien, Boulder, CO) is the most recent generation ablation system that attempts to produce predictable large spherical zones of ablation despite varying tissue environments across different tissue types such as liver, lung, and bone to name a few. This article will discuss these recent device developments as well as review some basic microwave characteristics. PMID:26622094

  16. Radiofrequency Ablation of Liver Tumors

    MedlinePlus

    ... Site Index A-Z Radiofrequency Ablation (RFA) of Liver Tumors Radiofrequency ablation (RFA) is a treatment that ... of Liver Tumors? What is Radiofrequency Ablation of Liver Tumors? Radiofrequency ablation, sometimes referred to as RFA, ...

  17. Microwave Tissue Ablation: Biophysics, Technology and Applications

    PubMed Central

    2010-01-01

    Microwave ablation is an emerging treatment option for many cancers, cardiac arrhythmias and other medical conditions. During treatment, microwaves are applied directly to tissues to produce rapid temperature elevations sufficient to produce immediate coagulative necrosis. The engineering design criteria for each application differ, with individual consideration for factors such as desired ablation zone size, treatment duration, and procedural invasiveness. Recent technological developments in applicator cooling, power control and system optimization for specific applications promise to increase the utilization of microwave ablation in the future. This article will review the basic biophysics of microwave tissue heating, provide an overview of the design and operation of current equipment, and outline areas for future research for microwave ablation. PMID:21175404

  18. Ablative skin resurfacing.

    PubMed

    Chwalek, Jennifer; Goldberg, David J

    2011-01-01

    Ablative skin resurfacing has remained the gold standard for treating photodamage and acne scars since the development of the first CO(2) lasers. CO(2) and Er:YAG lasers emit infrared light, which targets water resulting in tissue contraction and collagen formation. The first ablative laser systems created significant thermal damage resulting in unacceptably high rates of scarring and prolonged healing. Newer devices, such as high-energy pulsed lasers and fractional ablative lasers, are capable of achieving significant improvements with fewer side effects and shorter recovery times. While ablative resurfacing has become safer, careful patient selection is still important to avoid post-treatment scarring, dyspigmentation, and infections. Clinicians utilizing ablative devices need to be aware of possible side effects in order to maximize results and patient satisfaction. This chapter reviews the background of ablative lasers including the types of ablative lasers, mechanism of action, indications for ablative resurfacing, and possible side effects.

  19. Sphere-Enhanced Microwave Ablation (sMWA) Versus Bland Microwave Ablation (bMWA): Technical Parameters, Specific CT 3D Rendering and Histopathology

    SciTech Connect

    Gockner, T. L.; Zelzer, S.; Mokry, T. Gnutzmann, D. Bellemann, N.; Mogler, C.; Beierfuß, A. Köllensperger, E. Germann, G.; Radeleff, B. A. Stampfl, U. Kauczor, H. U.; Pereira, P. L.; Sommer, C. M.

    2015-04-15

    PurposeThis study was designed to compare technical parameters during ablation as well as CT 3D rendering and histopathology of the ablation zone between sphere-enhanced microwave ablation (sMWA) and bland microwave ablation (bMWA).MethodsIn six sheep-livers, 18 microwave ablations were performed with identical system presets (power output: 80 W, ablation time: 120 s). In three sheep, transarterial embolisation (TAE) was performed immediately before microwave ablation using spheres (diameter: 40 ± 10 μm) (sMWA). In the other three sheep, microwave ablation was performed without spheres embolisation (bMWA). Contrast-enhanced CT, sacrifice, and liver harvest followed immediately after microwave ablation. Study goals included technical parameters during ablation (resulting power output, ablation time), geometry of the ablation zone applying specific CT 3D rendering with a software prototype (short axis of the ablation zone, volume of the largest aligned ablation sphere within the ablation zone), and histopathology (hematoxylin-eosin, Masson Goldner and TUNEL).ResultsResulting power output/ablation times were 78.7 ± 1.0 W/120 ± 0.0 s for bMWA and 78.4 ± 1.0 W/120 ± 0.0 s for sMWA (n.s., respectively). Short axis/volume were 23.7 ± 3.7 mm/7.0 ± 2.4 cm{sup 3} for bMWA and 29.1 ± 3.4 mm/11.5 ± 3.9 cm{sup 3} for sMWA (P < 0.01, respectively). Histopathology confirmed the signs of coagulation necrosis as well as early and irreversible cell death for bMWA and sMWA. For sMWA, spheres were detected within, at the rim, and outside of the ablation zone without conspicuous features.ConclusionsSpecific CT 3D rendering identifies a larger ablation zone for sMWA compared with bMWA. The histopathological signs and the detectable amount of cell death are comparable for both groups. When comparing sMWA with bMWA, TAE has no effect on the technical parameters during ablation.

  20. Pulsed HF laser ablation of dentin

    NASA Astrophysics Data System (ADS)

    Papagiakoumou, Eirini I.; Papadopoulos, Dimitris N.; Makropoulou, Mersini I.; Khabbaz, Maruan G.; Serafetinides, Alexander A.

    2005-03-01

    The interaction of a TEA (Transversally Excited Atmospheric pressure) corona preionized oscillator double amplifier HF (hydrogen fluoride) laser beam with dentin tissue is reported. Pulses of 39 ns in the wavelength range of 2.65-3.35 μm and output energies in the range of 10-45 mJ, in a predominantly TEM00 beam were used to interact with dentin tissue. Ablation experiments were conducted with the laser beam directly focused on the tissue. Several samples of freshly extracted human teeth were used, cut longitudinally in facets of about 1mm thick and stored in phosphate buffered saline after being cleaned from the soft tissue remains. The experimental data (ablation thresholds, ablation rates) are discussed with respect to the ablation mechanism(s). Adequate tissue removal was observed and the ablation behavior was, in the greates part of the available fluences, almost linear. From the microscopic examination of teh samples, in a scanning electron microscope (SEM), the irradiated surfaces displayed oval craters (reflecting the laser beam shape) with absence of any melting or carbonization zone. It is suggested that the specific laser removes hard tissue by a combined photothermal and plasma mediated ablation mechanism, leaving a surface free from thermal damage and with a well-shaped crater.

  1. 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.

  2. Printable Nanophotonic Devices via Holographic Laser Ablation.

    PubMed

    Zhao, Qiancheng; Yetisen, Ali K; Sabouri, Aydin; Yun, Seok Hyun; Butt, Haider

    2015-09-22

    Holography plays a significant role in applications such as data storage, light trapping, security, and biosensors. However, conventional fabrication methods remain time-consuming, costly, and complex, limiting the fabrication of holograms and their extensive use. Here, we demonstrate a single-pulse laser ablation technique to write parallel surface gratings and Fresnel zone plates. We utilized a 6 ns high-energy green laser pulse to form interference patterns to record a surface grating with 820 nm periodicity and asymmetric zone plate holograms on 4.5 nm gold-coated substrates. The holographic recording process was completed within seconds. The optical characteristics of the interference patterns have been computationally modeled, and well-ordered polychromatic diffraction was observed from the fabricated holograms. The zone plate showed a significant diffraction angle of 32° from the normal incident for the focal point. The nanosecond laser interference ablation for rapid hologram fabrication holds great potential in a vast range of optical devices.

  3. Thermal tumor ablation in clinical use.

    PubMed

    Brace, C

    2011-01-01

    Although a surgical procedure is performed by visual inspection with histopathological assessment of the excised tumor and margins, percutaneous and noninvasive thermal ablation is performed strictly with the aid of imaging. Applicator guidance into the target zone, treatment monitoring and verification, and clinical follow-up rely on effective imaging. Detailed discussion of imaging is beyond the scope of this article, but the influence of imaging on the choice of thermal ablation or procedural approach will be discussed as needed. More information on imaging for interventional therapies can be found in other articles in this issue of IEEE Pulse.

  4. Pulmonary ablation: a primer.

    PubMed

    Roberton, Benjamin J; Liu, David; Power, Mark; Wan, John M C; Stuart, Sam; Klass, Darren; Yee, John

    2014-05-01

    Percutaneous image-guided thermal ablation is safe and efficacious in achieving local control and improving outcome in the treatment of both early stage non-small-cell lung cancer and pulmonary metastatic disease, in which surgical treatment is precluded by comorbidity, poor cardiorespiratory reserve, or unfavorable disease distribution. Radiofrequency ablation is the most established technology, but new thermal ablation technologies such as microwave ablation and cryoablation may offer some advantages. The use of advanced techniques, such as induced pneumothorax and the popsicle stick technique, or combining thermal ablation with radiotherapy, widens the treatment options available to the multidisciplinary team. The intent of this article is to provide the reader with a practical knowledge base of pulmonary ablation by concentrating on indications, techniques, and follow-up.

  5. Renal Ablation Update

    PubMed Central

    Khiatani, Vishal; Dixon, Robert G.

    2014-01-01

    Thermal ablative technologies have evolved considerably in the recent past and are now an important component of current clinical guidelines for the treatment of small renal masses. Both radiofrequency ablation and cryoablation have intermediate-term oncologic control that rivals surgical options, with favorable complication profiles. Studies comparing cryoablation and radiofrequency ablation show no significant difference in oncologic control or complication profile between the two modalities. Early data from small series with microwave ablation have shown similar promising results. Newer technologies including irreversible electroporation and high-intensity–focused ultrasound have theoretical advantages, but will require further research before becoming a routine part of the ablation armamentarium. The purpose of this review article is to discuss the current ablative technologies available, briefly review their mechanisms of action, discuss technical aspects of each, and provide current data supporting their use. PMID:25049445

  6. Radiofrequency Ablation of Cancer

    SciTech Connect

    Friedman, Marc; Mikityansky, Igor; Kam, Anthony; Libutti, Steven K.; Walther, McClellan M.; Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J.

    2004-09-15

    Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized.

  7. Lung Ablation: Whats New?

    PubMed

    Xiong, Lillian; Dupuy, Damian E

    2016-07-01

    Lung cancer had an estimated incidence of 221,200 in 2015, making up 13% of all cancer diagnoses. Tumor ablation is an important treatment option for nonsurgical lung cancer and pulmonary metastatic patients. Radiofrequency ablation has been used for over a decade with newer modalities, microwave ablation, cryoablation, and irreversible electroporation presenting as additional and possibly improved treatment options for patients. This minimally invasive therapy is best for small primary lesions or favorably located metastatic tumors. These technologies can offer palliation and sometimes cure of thoracic malignancies. This article discusses the current available technologies and techniques available for tumor ablation.

  8. Stellar Ablation of Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Moore, Thomas E.; Horwitz, J. L.

    2007-01-01

    We review observations and theories of the solar ablation of planetary atmospheres, focusing on the terrestrial case where a large magnetosphere holds off the solar wind, so that there is little direct atmospheric impact, but also couples the solar wind electromagnetically to the auroral zones. We consider the photothermal escape flows known as the polar wind or refilling flows, the enhanced mass flux escape flows that result from localized solar wind energy dissipation in the auroral zones, and the resultant enhanced neutral atom escape flows. We term these latter two escape flows the "auroral wind." We review observations and theories of the heating and acceleration of auroral winds, including energy inputs from precipitating particles, electromagnetic energy flux at magnetohydrodynamic and plasma wave frequencies, and acceleration by parallel electric fields and by convection pickup processes also known as "centrifugal acceleration." We consider also the global circulation of ionospheric plasmas within the magnetosphere, their participation in magnetospheric disturbances as absorbers of momentum and energy, and their ultimate loss from the magnetosphere into the downstream solar wind, loading reconnection processes that occur at high altitudes near the magnetospheric boundaries. We consider the role of planetary magnetization and the accumulating evidence of stellar ablation of extrasolar planetary atmospheres. Finally, we suggest and discuss future needs for both the theory and observation of the planetary ionospheres and their role in solar wind interactions, to achieve the generality required for a predictive science of the coupling of stellar and planetary atmospheres over the full range of possible conditions.

  9. Ablative Thermal Protection System Fundamentals

    NASA Technical Reports Server (NTRS)

    Beck, Robin A. S.

    2013-01-01

    This is the presentation for a short course on the fundamentals of ablative thermal protection systems. It covers the definition of ablation, description of ablative materials, how they work, how to analyze them and how to model them.

  10. Catheter ablation of fascicular ventricular tachycardia.

    PubMed

    Ramprakash, B; Jaishankar, S; Rao, Hygriv B; Narasimhan, C

    2008-08-01

    Fascicular ventricular tachycardia (VT) is an idiopathic VT with right bundle branch block morphology and left-axis deviation occuring predominantly in young males. Fascicular tachycardia has been classified into three subtypes namely, left posterior fascicular VT, left anterior fascicular VT and upper septal fascicular VT. The mechanism of this tachycardia is believed to be localized reentry close to the fascicle of the left bundle branch. The reentrant circuit is composed of a verapamil sensitive zone, activated antegradely during tachycardia and the fast conduction Purkinje fibers activated retrogradely during tachycardia recorded as the pre Purkinje and the Purkinje potentials respectively. Catheter ablation is the preferred choice of therapy in patients with fascicular VT. Ablation is carried out during tachycardia, using conventional mapping techniques in majority of the patients, while three dimensional mapping and sinus rhythm ablation is reserved for patients with nonmappable tachycardia.

  11. Sprayable lightweight ablative coating

    NASA Technical Reports Server (NTRS)

    Simpson, William G. (Inventor); Sharpe, Max H. (Inventor); Hill, William E. (Inventor)

    1991-01-01

    An improved lightweight, ablative coating is disclosed that may be spray applied and cured without the development of appreciable shrinkage cracks. The ablative mixture consists essentially of phenolic microballoons, hollow glass spheres, glass fibers, ground cork, a flexibilized resin binder, and an activated colloidal clay.

  12. Pulsed Tm:YAG laser ablation of knee joint tissues

    NASA Astrophysics Data System (ADS)

    Shi, Wei-Qiang; Vari, Sandor G.; Duffy, J. T.; Miller, J. M.; Weiss, Andrew B.; Fishbein, Michael C.; Grundfest, Warren S.

    1992-06-01

    We investigated the effect of a free-running 2.01 micron pulsed Tm:YAG laser on bovine knee joint tissues. Ablation rates of fresh fibrocartilage, hyaline cartilage, and bone were measured in saline as a function of laser fluence (160 - 640 J/cm2) and fiber core size (400 and 600 microns). All tissues could be effectively ablated and the ablation rate increased linearly with the increasing fluence. Use of fibers of different core sizes, while maintaining constant energy fluence, did not result in significant difference in ablation rate. Histology analyses of the ablated tissue samples reveal average Tm:YAG radiation induced thermal damage (denatunalization) zones ranging between 130 and 540 microns, depending on the laser parameters and the tissue type.

  13. Histological evaluation of vertical laser channels from ablative fractional resurfacing: an ex vivo pig skin model.

    PubMed

    Skovbølling Haak, Christina; Illes, Monica; Paasch, Uwe; Hædersdal, Merete

    2011-07-01

    Ablative fractional resurfacing (AFR) represents a new treatment potential for various skin conditions and new laser devices are being introduced. It is important to gain information about the impact of laser settings on the dimensions of the created laser channels for obtaining a safe and efficient treatment outcome. The aim of this study was to establish a standard model to document the histological tissue damage profiles after AFR and to test a new laser device at diverse settings. Ex vivo abdominal pig skin was treated with a MedArt 620, prototype fractional carbon dioxide (CO(2)) laser (Medart, Hvidovre, Denmark) delivering single microbeams (MB) with a spot size of 165 μm. By using a constant pulse duration of 2 ms, intensities of 1-18 W, single and 2-4 stacked pulses, energies were delivered in a range from 2-144 mJ/MB. Histological evaluations included 3-4 high-quality histological measurements for each laser setting (n = 28). AFR created cone-shaped laser channels. Ablation depths varied from reaching the superficial dermis (2 mJ, median 41 μm) to approaching the subcutaneous fat (144 mJ, median 1,943 μm) and correlated to the applied energy levels in an approximate linear relation (r(2) = 0.84, p < 0.001). The dermal ablation width increased slightly within the energy range of 4-144 mJ (median 163 μm). The thickness of the coagulation zone reached a plateau around 65 μm at energies levels above 16 mJ. The calculated volumes of ablated tissue increased with increasing energies. We suggest this ex vivo pig skin model to characterize AFR laser channels histologically.

  14. Healing responses following cryothermic and hyperthermic tissue ablation

    NASA Astrophysics Data System (ADS)

    Godwin, Braden L.; Coad, James E.

    2009-02-01

    Minimally invasive, thermally ablative, interventional technologies have been changing the practice of medicine since before the turn of the 20th century. More recently, cryothermic and hyperthermic therapies have expanded in terms of their spectrum of thermal generators, modes for controlling and monitoring the treatment zone and both benign and malignant medical applications. The final tissue, and hence clinical outcome, of a thermal ablation is determined by the summation of direct primary (thermal) and secondary (apoptosis, ischemia, free radical, inflammation, wound healing, etc.) injury followed by possible cellular regeneration and scar formation. The initial thermal lesion can be broadly divided into two major zones of cellular death: 1) the complete ablation zone closer to the thermal source and 2) the peripheral transition zone with a decreasing gradient of cell death. While not applicable to cryotherapy, hyperthermic complete ablation zones are subdivided into two zones: 1) thermal or heat fixation and 2) coagulative necrosis. It is important to clearly differentiate these tissue zones because of their substantially different healing responses. Therefore, the development of clinically successful thermal therapies requires an understanding of tissue healing responses. The healing responses can be affected by a number of additional factors such as the tissue's anatomy, organ specific healing differences, blood supply, protein vs. lipid content, and other factors. Thus, effective biomedical instrument development requires both an understanding of thermal cell injury/death and the body's subsequent healing responses. This paper provides a general overview of the healing pathways that follow thermal tissue treatment.

  15. Finite-element analysis and in vitro experiments of placement configurations using triple antennas in microwave hepatic ablation.

    PubMed

    Phasukkit, Pattarapong; Tungjitkusolmun, Supan; Sangworasil, Manas

    2009-11-01

    This study presents analyses of triple-antenna configurations and designs for microwave (MW) hepatic ablation using 3-D finite-element (FE) analyses verified by in vitro experiments. Treatment of hepatic cancer often requires removal or destruction of large volume lesions. Using multiple antennas offers a potential solution for creating ablation zones with larger dimensions, as well as varied geometrical shapes. We performed both 3-D FE analyses and in vitro experiments using three identical open-tip MW antennas simultaneously, placing them in three types of configurations-"linear array," "triangular," and "T-shaped" arrangements. We compared coagulation volumes created, as well as temperature distribution characteristics, from the three-antenna arrangements after power delivery of 50 W for 60 s. We also performed additional tests using nonidentical antennas (open tip, slot, and slot with insulating jacket) for the three configurations. The results illustrate that arranging antennas in the "T-shaped" pattern destroyed more unwanted tissues than those found when using "linear array" and "triangular" arrangements, with maximum coagulation width and depth of 46 and 81 mm, respectively, and coagulation volume of 30.7 cm(3) . In addition, using nonidentical triple antennas caused variations in coagulation zone characteristics, and thus, the technique could be applied to treatment situations where nonsymmetric coagulation zones are required.

  16. Tumor Ablation and Nanotechnology

    PubMed Central

    Manthe, Rachel L.; Foy, Susan P.; Krishnamurthy, Nishanth; Sharma, Blanka; Labhasetwar, Vinod

    2010-01-01

    Next to surgical resection, tumor ablation is a commonly used intervention in the treatment of solid tumors. Tumor ablation methods include thermal therapies, photodynamic therapy, and reactive oxygen species (ROS) producing agents. Thermal therapies induce tumor cell death via thermal energy and include radiofrequency, microwave, high intensity focused ultrasound, and cryoablation. Photodynamic therapy and ROS producing agents cause increased oxidative stress in tumor cells leading to apoptosis. While these therapies are safe and viable alternatives when resection of malignancies is not feasible, they do have associated limitations that prevent their widespread use in clinical applications. To improve the efficacy of these treatments, nanoparticles are being studied in combination with nonsurgical ablation regimens. In addition to better thermal effect on tumor ablation, nanoparticles can deliver anticancer therapeutics that show synergistic anti-tumor effect in the presence of heat and can also be imaged to achieve precision in therapy. Understanding the molecular mechanism of nanoparticle-mediated tumor ablation could further help engineer nanoparticles of appropriate composition and properties to synergize the ablation effect. This review aims to explore the various types of nonsurgical tumor ablation methods currently used in cancer treatment and potential improvements by nanotechnology applications. PMID:20866097

  17. Thermal ablation for hepatocellular carcinoma.

    PubMed

    Head, Hayden W; Dodd, Gerald D

    2004-11-01

    Thermal ablation, as a form of minimally invasive therapy for hepatocellular carcinoma (HCC), has become an important treatment modality. Because of the limitations of surgery, the techniques of thermal ablation have become standard therapies for HCC in some situations. This article reviews 4 thermal ablation techniques-radiofrequency (RF) ablation, microwave ablation, laser ablation, and cryoablation. Each of these techniques may have a role in treating HCC, and the mechanisms, equipment, patient selection, results, and complications of each are considered. Furthermore, combined therapies consisting of thermal ablation and adjuvant chemotherapy also show promise for enhancing these techniques. Important areas of research into thermal ablation remain, including improving the ability of ablation to treat larger tumors, determining the indications for each thermal ablation modality, optimizing image guidance, and obtaining good outcome data on the efficacy of these techniques.

  18. Experiments on ocular tissue ablation at 5.3 and 6.0 {mu}m with the Los Alamos advanced FEL

    SciTech Connect

    Nguyen, D.C.; Ren, Q.; Hill, R.

    1995-12-31

    We investigated the ablation characteristics of a picosecond free-electron laser and compared its ablation effects on ocular tissues at 5.3 {mu}m and 6.0 {mu}m. The Advanced FEL at Los Alamos, operating in the wavelength range 4-6 {mu}m, was used for this study. The 10-{mu}s macropulse consisted of {approximately}1000 micropulses, each approximately 15 ps in length and separated from one another by 9.2 ns. The FEL beam was passed through a series of attenuator and focused to a 200-{mu}m spot in the sample with a 150-mm f.l. CaF{sub 2} lens. The energy in each macropulse ranged from 5 to 120 mJ. Five transplantable corneal-scleral buttons preserved in corneal storage media were used for this study. The tissue sample was positioned at the focused FEL beam for the ablation, and then fixed for histologic study. Corneal cuts made at 6.0 {mu}m revealed a well-defined ablation boundary. The measured lateral zone of the tissue damage was 11 {+-} 2 {mu}m. The integrity of the adjacent tissue was well maintained. By contrast, the ablation boundary of the corneal cuts made at 5.3 {mu}m appeared to be very disruptive. The collagen fiber near the ablation was thermally denatured and lost its organized structure. The lateral dimension of such effect extended out to 220 {mu}m beyond the intended cut into the surrounding tissues. We concluded that a short-pulsed laser operating at 6 {mu}m may be a potentially effective tool for cutting ocular tissues.

  19. Monitoring radiofrequency ablation using real-time ultrasound Nakagami imaging combined with frequency and temporal compounding techniques.

    PubMed

    Zhou, Zhuhuang; Wu, Shuicai; Wang, Chiao-Yin; Ma, Hsiang-Yang; Lin, Chung-Chih; Tsui, Po-Hsiang

    2015-01-01

    Gas bubbles induced during the radiofrequency ablation (RFA) of tissues can affect the detection of ablation zones (necrosis zone or thermal lesion) during ultrasound elastography. To resolve this problem, our previous study proposed ultrasound Nakagami imaging for detecting thermal-induced bubble formation to evaluate ablation zones. To prepare for future applications, this study (i) created a novel algorithmic scheme based on the frequency and temporal compounding of Nakagami imaging for enhanced ablation zone visualization, (ii) integrated the proposed algorithm into a clinical scanner to develop a real-time Nakagami imaging system for monitoring RFA, and (iii) investigated the applicability of Nakagami imaging to various types of tissues. The performance of the real-time Nakagami imaging system in visualizing RFA-induced ablation zones was validated by measuring porcine liver (n = 18) and muscle tissues (n = 6). The experimental results showed that the proposed algorithm can operate on a standard clinical ultrasound scanner to monitor RFA in real time. The Nakagami imaging system effectively monitors RFA-induced ablation zones in liver tissues. However, because tissue properties differ, the system cannot visualize ablation zones in muscle fibers. In the future, real-time Nakagami imaging should be focused on the RFA of the liver and is suggested as an alternative monitoring tool when advanced elastography is unavailable or substantial bubbles exist in the ablation zone.

  20. Monitoring Radiofrequency Ablation Using Real-Time Ultrasound Nakagami Imaging Combined with Frequency and Temporal Compounding Techniques

    PubMed Central

    Zhou, Zhuhuang; Wu, Shuicai; Wang, Chiao-Yin; Ma, Hsiang-Yang; Lin, Chung-Chih; Tsui, Po-Hsiang

    2015-01-01

    Gas bubbles induced during the radiofrequency ablation (RFA) of tissues can affect the detection of ablation zones (necrosis zone or thermal lesion) during ultrasound elastography. To resolve this problem, our previous study proposed ultrasound Nakagami imaging for detecting thermal-induced bubble formation to evaluate ablation zones. To prepare for future applications, this study (i) created a novel algorithmic scheme based on the frequency and temporal compounding of Nakagami imaging for enhanced ablation zone visualization, (ii) integrated the proposed algorithm into a clinical scanner to develop a real-time Nakagami imaging system for monitoring RFA, and (iii) investigated the applicability of Nakagami imaging to various types of tissues. The performance of the real-time Nakagami imaging system in visualizing RFA-induced ablation zones was validated by measuring porcine liver (n = 18) and muscle tissues (n = 6). The experimental results showed that the proposed algorithm can operate on a standard clinical ultrasound scanner to monitor RFA in real time. The Nakagami imaging system effectively monitors RFA-induced ablation zones in liver tissues. However, because tissue properties differ, the system cannot visualize ablation zones in muscle fibers. In the future, real-time Nakagami imaging should be focused on the RFA of the liver and is suggested as an alternative monitoring tool when advanced elastography is unavailable or substantial bubbles exist in the ablation zone. PMID:25658424

  1. 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.

  2. 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.

  3. Endometrial Ablation for Menorrhagia

    PubMed Central

    Sanders, Barry H.

    1992-01-01

    Endometrial ablation is a relatively new treatment for patients with persistent menorrhagia. The procedure can be performed by either laser photocoagulation or electrocoagulation; both have a very low risk of complication. Generally, less than 24 hours of hospitalization is required and return to normal activities, including work, is almost immediate. Endometrial ablation is likely to become a mainstay of treatment for menorrhagia as the technology and training become more readily available. PMID:21229128

  4. Multiple-antenna microwave ablation: analysis of non-parallel antenna implants

    NASA Astrophysics Data System (ADS)

    Mukherjee, Souvick; Curto, Sergio; Albin, Nathan; Natarajan, Bala; Prakash, Punit

    2015-03-01

    Microwave ablation is a minimally invasive modality increasingly being used for thermal treatment of cancer in various organs. During ablation procedures, treatment planning is typically restricted to vendor specifications of expected ablation zone volumes based on experiments in unperfused ex vivo tissues, presuming parallel insertion of antennas. However, parallel antenna implants are not always clinically possible due to the restricted control of flexible antennas and presence of intervening organs. This paper aims to quantify the effect of non-parallel antenna implants on the ablation volume. 3D electromagnetic-bioheat transfer models were implemented to analyze ablation zone profiles created by dual antenna arrays. Parallel and non-parallel implants spaced 10-25 mm with antenna tips deviated to create converging or diverging configurations were analyzed. Volumetric Dice Similarity Coefficients (DSC) were calculated to compare ablation zone volumes for parallel and non-parallel configuration. Antenna tip displacements of 3 mm/antenna yielded an average DSC of 0.78. Tip displacements of 5 mm/antenna yielded a DSC of 0.78 and 0.64 for 15 mm and 20 mm antenna spacing, respectively. For ablation with dipole antennas as the frequency of operation decreases from 2.45 GHz to 915 MHz the similarity between the ablation zones for parallel and angled cases increased significantly. In conclusion, ablation volumes with non-parallel antenna implants may differ significantly from the parallel configuration. Patient-specific treatment planning tools may provide more accurate predictions of 3D-ablation volumes based on imaging data of actual implanted antenna configurations. Methods to compare ablation zone volumes incorporating uncertainty in antenna positions and experimental results to validate the numerical modelling are also presented.

  5. CT thermometry for cone-beam CT guided ablation

    NASA Astrophysics Data System (ADS)

    DeStefano, Zachary; Abi-Jaoudeh, Nadine; Li, Ming; Wood, Bradford J.; Summers, Ronald M.; Yao, Jianhua

    2016-03-01

    Monitoring temperature during a cone-beam CT (CBCT) guided ablation procedure is important for prevention of over-treatment and under-treatment. In order to accomplish ideal temperature monitoring, a thermometry map must be generated. Previously, this was attempted using CBCT scans of a pig shoulder undergoing ablation.1 We are extending this work by using CBCT scans of real patients and incorporating more processing steps. We register the scans before comparing them due to the movement and deformation of organs. We then automatically locate the needle tip and the ablation zone. We employ a robust change metric due to image noise and artifacts. This change metric takes windows around each pixel and uses an equation inspired by Time Delay Analysis to calculate the error between windows with the assumption that there is an ideal spatial offset. Once the change map is generated, we correlate change data with measured temperature data at the key points in the region. This allows us to transform our change map into a thermal map. This thermal map is then able to provide an estimate as to the size and temperature of the ablation zone. We evaluated our procedure on a data set of 12 patients who had a total of 24 ablation procedures performed. We were able to generate reasonable thermal maps with varying degrees of accuracy. The average error ranged from 2.7 to 16.2 degrees Celsius. In addition to providing estimates of the size of the ablation zone for surgical guidance, 3D visualizations of the ablation zone and needle are also produced.

  6. Fascicular ventricular tachycardia: experience with radiofrequency ablation.

    PubMed

    Magalhaes, Sónia; Gonçalves, Helena; Primo, João; Sá, Ana Paula; Silva, Paula; Rosas, Rui; Gama, Vasco

    2006-05-01

    Fascicular ventricular tachycardia (VT), the commonest form of idiopathic left VT, occurs more frequently in young males without structural heart disease and usually presents as paroxysmal palpitations. It is subdivided into two more common subtypes, posterior and anterior. A macro-reentrant circuit involving a considerable and variable extent of the left interventricular septum is presumed to be the underlying arrhythmogenic mechanism. A slow conduction zone with particular sensitivity to verapamil participates in the circuit and it seems that diastolic potentials (DP) represent the electrical activity in or near this zone. The fascicles of the left bundle appear to constitute part of the retrograde pathway and Purkinje potentials (PP) are assumed to represent their activation. In the present retrospective study, the authors review twelve cases of fascicular VT (ten posterior and two anterior) evaluated in the electrophysiology laboratory. Although initial induction was obtained in all patients, reproducibility was poor as a consequence of frequent contact inhibition during endocardial mapping of the left ventricle and this meant that ablation was not possible in two cases. Two cases of associated atrioventricular nodal reentrant tachycardia (AVNRT) and a case of associated atrioventricular reentrant tachycardia by a right posterior accessory pathway were documented, which suggest a correlated anatomic substrate. After ablation of the slow nodal pathway in one of the AVNRTs, fascicular VT was no longer inducible. Ablation of the fascicular VT was attempted in nine patients, at the tachycardia exit site (characterized by an early ventricular electrogram fused with a Purkinje potential) in two patients with anterior fascicular VT and in five patients with the posterior subtype, and near the slow conduction pathway (site with simultaneous recording of DP and PP) in the other two patients. The initial success rate with a single procedure was 78%, two of the ablations

  7. Extra Dimensions

    SciTech Connect

    Hewett, J.

    2004-10-05

    The large separation between the weak scale {approx} 10{sup 3} GeV and the traditional scale of gravity--the Planck scale with M{sub PI} {approx} 10{sup 19} GeV--is one of the most puzzling aspects of nature. The origin of this large ratio, as well as its stability under radiative corrections, demands explanation. This is known as the hierarchy problem. One theoretical means of solving this problem is to introduce Supersymmetry. Alternatively one may hope to address the hierarchy by exploiting the geometry of space time. Specifically, recent theories involve the idea that the 3-spatial dimensions in which we live could be a 3-spatial-dimensional ''membrane'' embedded in a much larger extra dimensional space, and that the hierarchy is generated by the geometry of the additional dimensions. Such ideas have led to extra dimensional theories which have verifiable consequences at the TeV scale. Our knowledge of the weak and strong forces extends down to scales of {approx} (100 GeV){sup -1} (or of order 10{sup -15} mm). On the other hand, we have almost no knowledge of gravity at distances less than roughly a millimeter, as direct tests of the gravitational force at the smallest distances are based on torsion-balance experiments, which are mechanically limited. It is thus conceivable that gravity may behave quite differently from the 3-dimensional Newtonian theory at small distances. This leads to the possibility that matter and non-gravitational forces are confined to our 3-dimensional subspace, whereas gravity may propagate throughout a higher dimensional volume. In this case, the gauge forces are trapped within our 3-dimensional space, unaware of the extra dimensions, and maintain their usual behavior. Gravity, on the other hand, would no longer follow the inverse-square force law at distances smaller than the size of the extra dimensions, as the gravitational equivalent of Gauss' Law mandates that the gravitational field spreads out into the full spatial volume

  8. Highspeed laser ablation cutting of metal

    NASA Astrophysics Data System (ADS)

    Ullmann, F.; Loeschner, U.; Hartwig, L.; Szczepanski, D.; Schille, J.; Gronau, S.; Knebel, T.; Drechsel, J.; Ebert, R.; Exner, H.

    2013-02-01

    In laser ablation cutting, irradiation of high-intense laser beams causes ejection of molten and evaporated material out of the cutting zone as a result of high pressure gradients, induced by expanding plasma plumes. This paper investigates highspeed laser ablation cutting of industrial grade metal sheets using high-brilliant continuous wave fiber lasers with output powers up to 5 kW. The laser beam was deflected with scan speeds up to 2700 m/min utilizing both a fast galvanometer scan system and a polygon scan system. By sharp laser beam focusing using different objectives with focal lengths ranging between 160 mm and 500 mm, small laser spot diameters between 16.5 μm and 60 μm were obtained, respectively. As a result high peak intensities between 3*108 W/cm² and 2.5*109 W/cm² were irradiated on the sample surface, and cutting kerfs with a maximum depth of 1.4 mm have been produced. In this study the impact of the processing parameters laser power, laser spot diameter, cutting speed, and number of scans on both the achievable cutting depth and the cutting edge quality was investigated. The ablation depths, the heights of the cutting burr, as well as the removed material volumes were evaluated by means of optical microscope images and cross section photographs. Finally highspeed laser ablation cutting was studied using an intensified ultra highspeed camera in order to get useful insights into the cutting process.

  9. A new system of microwave ablation at 2450 MHz: preliminary experience.

    PubMed

    Ierardi, Anna Maria; Mangano, Alberto; Floridi, Chiara; Dionigi, Gianlorenzo; Biondi, Antonio; Duka, Ejona; Lucchina, Natalie; Lianos, Georgios D; Carrafiello, Gianpaolo

    2015-03-01

    The aim of this study was to assess the feasibility of the application of the new system (Emprint Microwave Ablation System, Covidien Boulder, CO, USA) and to identify its advantages. In particular the attention was focused to the spherical ablation zone obtained and its usefulness in terms of effectiveness. The new system is composed of: a 2450 MHz generator that delivers a maximum power of 100 W, a fiberglass antenna and a pump for internally cooled antenna. Ten liver nodules (8 hepatocellular carcinomas and 2 metastasis) were percutaneously treated (mean diameter 24.9 mm, range 16-35 mm). Technical success, ablation duration time, overall procedure time and safety were registered. To define the shape of the ablation zone, multiplanar reformatting (MPR) was performed. Roundness index transverse was calculated: a value near 1 represents a more spherical ablation zone shape, and a value distant from 1 implies an oval configuration. Technical success was 100%. Mean ablation time was of 3.85 min (range 3-5 min), mean overall procedure time was 30.5 min (range 25-40 min). No major complications were recorded. Roundness index transverse presented a mean value of 0.94, meaning that a spherical shape of ablation zone was achieved. One of the most promising innovations of the new microwave technology is the spherical shape of the ablation volume that could be related with an improving of the effectiveness and safety.

  10. Analysis of ablation debris from natural and artificial iron meteorites

    NASA Technical Reports Server (NTRS)

    Blanchard, M. B.; Davis, A. S.

    1977-01-01

    Artificial ablation studies were performed on iron and nickel-iron samples using an arc-heated plasma of ionized air. Experiment conditions simulated a meteoroid traveling about 12 km/sec at an altitude of 70 km. The artificially produced fusion crusts and ablation debris show features very similar to natural fusion crusts of the iron meteorites Boguslavka, Norfork, and N'Kandhla and to magnetic spherules recovered from Mn nodules. X-ray diffraction, electron microprobe, optical, and scanning electron microscope analyses reveal that important mineralogical, elemental, and textural changes occur during ablation. Some metal is melted and ablated. The outer margin of the melted rind is oxidized and recrystallizes as a discontinuous crust of magnetite and wustite. Adjacent to the oxidized metallic ablation zone is an unoxidized metallic ablation zone in which structures such as Widmannstatten bands are obliterated as the metal is transformed to unequilibrated alpha 2 nickel-iron. Volatile elements are vaporized and less volatile elements undergo fractionation.

  11. Monopole antennas for microwave catheter ablation

    SciTech Connect

    Labonte, S.; Blais, A.; Legault, S.R.; Ali, H.O.; Roy, L.

    1996-10-01

    The authors study the characteristics of various monopole antennas for microwave catheter ablation of the endocardium. The investigation is done with a computer model based on the finite-element method in the frequency domain. Three monopole geometries are considered: open-tip, dielectric-tip, and metal-tip. Calculations are made for the magnetic field, the reflection coefficient and the power deposition pattern of the antennas immersed in normal saline. The theoretical results are compared with measurements performed on prototypes and good agreement is obtained. The antenna characteristics suggest that the metal-tip monopole best fulfills the requirements of catheter ablation. The computer model is then used to compare metal-tip monopoles of different dimensions and to determine design trade-offs.

  12. Dimension stone

    USGS Publications Warehouse

    Dolley, T.P.

    2003-01-01

    Dimension stone can be defined as natural rock material quarried to obtain blocks or slabs that meet specifications as to size (width, length and thickness) and shape for architectural or engineering purposes. Color, grain texture and pattern, and surface finish of the stone are also normal requirements. Other important selection criteria are durability (based on mineral composition, hardness and past performance), strength and the ability of the stone to take a polish.

  13. Method for evaluation of predictive models of microwave ablation via post-procedural clinical imaging

    NASA Astrophysics Data System (ADS)

    Collins, Jarrod A.; Brown, Daniel; Kingham, T. Peter; Jarnagin, William R.; Miga, Michael I.; Clements, Logan W.

    2015-03-01

    Development of a clinically accurate predictive model of microwave ablation (MWA) procedures would represent a significant advancement and facilitate an implementation of patient-specific treatment planning to achieve optimal probe placement and ablation outcomes. While studies have been performed to evaluate predictive models of MWA, the ability to quantify the performance of predictive models via clinical data has been limited to comparing geometric measurements of the predicted and actual ablation zones. The accuracy of placement, as determined by the degree of spatial overlap between ablation zones, has not been achieved. In order to overcome this limitation, a method of evaluation is proposed where the actual location of the MWA antenna is tracked and recorded during the procedure via a surgical navigation system. Predictive models of the MWA are then computed using the known position of the antenna within the preoperative image space. Two different predictive MWA models were used for the preliminary evaluation of the proposed method: (1) a geometric model based on the labeling associated with the ablation antenna and (2) a 3-D finite element method based computational model of MWA using COMSOL. Given the follow-up tomographic images that are acquired at approximately 30 days after the procedure, a 3-D surface model of the necrotic zone was generated to represent the true ablation zone. A quantification of the overlap between the predicted ablation zones and the true ablation zone was performed after a rigid registration was computed between the pre- and post-procedural tomograms. While both model show significant overlap with the true ablation zone, these preliminary results suggest a slightly higher degree of overlap with the geometric model.

  14. Rat liver regeneration following ablation with irreversible electroporation

    PubMed Central

    Bruinsma, Bote G.; Jaramillo, Maria; Yarmush, Martin L.

    2016-01-01

    During the past decade, irreversible electroporation (IRE) ablation has emerged as a promising tool for the treatment of multiple diseases including hepatic cancer. However, the mechanisms behind the tissue regeneration following IRE ablation have not been investigated. Our results indicate that IRE treatment immediately kills the cells at the treatment site preserving the extracellular architecture, in effect causing in vivo decellularization. Over the course of 4 weeks, progenitor cell differentiation, through YAP and notch pathways, together with hepatocyte expansion led to almost complete regeneration of the ablated liver leading to the formation of hepatocyte like cells at the ablated zone. We did not observe significant scarring or tumor formation at the regenerated areas 6 months post IRE. Our study suggests a new model to study the regeneration of liver when the naïve extracellular matrix is decellularized in vivo with completely preserved extracellular architecture. PMID:26819842

  15. Rat liver regeneration following ablation with irreversible electroporation.

    PubMed

    Golberg, Alexander; Bruinsma, Bote G; Jaramillo, Maria; Yarmush, Martin L; Uygun, Basak E

    2016-01-01

    During the past decade, irreversible electroporation (IRE) ablation has emerged as a promising tool for the treatment of multiple diseases including hepatic cancer. However, the mechanisms behind the tissue regeneration following IRE ablation have not been investigated. Our results indicate that IRE treatment immediately kills the cells at the treatment site preserving the extracellular architecture, in effect causing in vivo decellularization. Over the course of 4 weeks, progenitor cell differentiation, through YAP and notch pathways, together with hepatocyte expansion led to almost complete regeneration of the ablated liver leading to the formation of hepatocyte like cells at the ablated zone. We did not observe significant scarring or tumor formation at the regenerated areas 6 months post IRE. Our study suggests a new model to study the regeneration of liver when the naïve extracellular matrix is decellularized in vivo with completely preserved extracellular architecture.

  16. Artificial meteor ablation studies. [for identification of cosmic dust particles

    NASA Technical Reports Server (NTRS)

    Blanchard, M. B.

    1973-01-01

    Artificial meteor ablation was performed on natural minerals, composed predominately of magnetite and hematite, using an arc heated plasma stream of air. Analysis of the ablated debris indicated most was composed of two or more minerals. The more volatile elements were depleted and the relative abundance of Fe increased as a result of both volatile depletion and a reduction in its oxidation state. Hematite was converted to magnetite in the ablation zone, and quartz and apatite minerals were converted to an Fe-rich glass consisting of varying amounts of Si, P, Cl, and Ca, depending upon the accessory minerals available at the time of melting. Artificially created ablation products from iron oxides exhibited unique properties depending on the composition of the original material and the environmental conditions of formation. In addition to the accepted elemental criteria, these properties were morphologic characteristics, textural parameters, and the existence of metastable minerals.

  17. Tissue healing response following hyperthermic vapor ablation in the porcine longissimus muscle

    NASA Astrophysics Data System (ADS)

    Grantham, John T.; Grisez, Brian T.; Famoso, Justin; Hoey, Michael; Dixon, Chris; Coad, James E.

    2015-03-01

    As the use of hyperthermic ablation technologies has increased, so too has the need to understand their effects on tissue and their healing responses. This study was designed to characterize tissue injury and healing following hyperthermic vapor ablation in the in vivo porcine longissimus muscle model. The individual ablations were performed using the NxThera Vapor Delivery System (NxThera Inc., Minneapolis, MN). To assess the vapor ablation's evolution, the swine were euthanized post-treatment on Day 0, Day 3, Day 7, Day 14, Day 28, Day 45 and Day 90. Triphenyltetrazolium chloride viability staining (TTC staining) was used to macroscopically assess the extent of each vapor ablation within the tissue. The ablation associated healing responses were then histologically evaluated for acute inflammation, chronic inflammation, foreign body reaction and fibrosis. Two zones of tissue injury were initially identified in the ablations: 1) a central zone of complete coagulative necrosis and 2) an outer "transition zone" of viable and non-viable cells. The ablations initially increased in size from Day 0 to Day 7 and then progressively decreased in size though Day 45. The initial Day 3 healing changes originated in the transition zone with minimal acute and chronic inflammation. As time progressed, granulation tissue began to form by Day 7 and peaked around Day 14. Collagen formation, deposition and remodeling began in the adjacent healthy tissue by Day 28, replaced the ablation site by Day 45 and reorganized by Day 90. In conclusion, this vapor ablation technology provided a non-desiccating form of hyperthermic ablation that resulted in coagulative necrosis without a central thermally/heat-fixed tissue component, followed a classical wound healing pathway, and healed with minimal associated inflammation.

  18. Shuttle subscale ablative nozzle tests

    NASA Technical Reports Server (NTRS)

    Powers, L. B.; Bailey, R. L.

    1980-01-01

    Recent subscale nozzle tests have identified new and promising carbon phenolic nozzle ablatives which utilize staple rayon, PAN, and pitch based carbon cloth. A 4-inch throat diameter submerged test nozzle designed for the 48-inch Jet Propulsion Laboratory char motor was used to evaluate five different designs incorporating 20 candidate ablatives. Test results indicate that several pitch and PAN-based carbon phenolic ablatives can provide erosion and char performance equivalent or superior to the present continuous rayon-based SRM ablative.

  19. 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.

  20. Percutaneous ablation of adrenal tumors.

    PubMed

    Venkatesan, Aradhana M; Locklin, Julia; Dupuy, Damian E; Wood, Bradford J

    2010-06-01

    Adrenal tumors comprise a broad spectrum of benign and malignant neoplasms and include functional adrenal adenomas, pheochromocytomas, primary adrenocortical carcinoma, and adrenal metastases. Percutaneous ablative approaches that have been described and used in the treatment of adrenal tumors include percutaneous radiofrequency ablation, cryoablation, microwave ablation, and chemical ablation. Local tumor ablation in the adrenal gland presents unique challenges, secondary to the adrenal gland's unique anatomic and physiological features. The results of clinical series employing percutaneous ablative techniques in the treatment of adrenal tumors are reviewed in this article. Clinical and technical considerations unique to ablation in the adrenal gland are presented, including approaches commonly used in our practices, and risks and potential complications are discussed.

  1. Ablation of skeletal metastases: current status.

    PubMed

    Kurup, A Nicholas; Callstrom, Matthew R

    2010-08-01

    Image-guided percutaneous ablation of bone metastases is an effective, minimally invasive alternative to conventional therapies in the palliation of pain from metastatic disease. Ablative technologies applied in the treatment of skeletal metastases include radiofrequency ablation, cryoablation, microwave ablation, laser ablation, ethanol ablation, and, most recently, focused ultrasound. These ablative methods may be performed in combination with percutaneous cementoplasty to provide support and stabilization for metastases in weight-bearing bones at risk for pathologic fracture.

  2. Local ablative treatments for hepatocellular carcinoma: An updated review

    PubMed Central

    Facciorusso, Antonio; Serviddio, Gaetano; Muscatiello, Nicola

    2016-01-01

    Ablative treatments currently represent the first-line option for the treatment of early stage unresectable hepatocellular carcinoma (HCC). Furthermore, they are effective as bridging/downstaging therapies before orthotopic liver transplantation. Contraindications based on size, number, and location of nodules are quite variable in literature and strictly dependent on local expertise. Among ablative therapies, radiofrequency ablation (RFA) has gained a pivotal role due to its efficacy, with a reported 5-year survival rate of 40%-70%, and safety. Although survival outcomes are similar to percutaneous ethanol injection, the lower local recurrence rate stands for a wider application of RFA in hepato-oncology. Moreover, RFA seems to be even more cost-effective than liver resection for very early HCC (single nodule ≤ 2 cm) and in the presence of two or three nodules ≤ 3 cm. There is increasing evidence that combining RFA to transarterial chemoembolization may increase the therapeutic benefit in larger HCCs without increasing the major complication rate, but more robust prospective data is still needed to validate these pivotal findings. Among other thermal treatments, microwave ablation (MWA) uses high frequency electromagnetic energy to induce tissue death via coagulation necrosis. In comparison to RFA, MWA has several theoretical advantages such as a broader zone of active heating, higher temperatures within the targeted area in a shorter treatment time and the lack of heat-sink effect. The safety concerns raised on the risks of this procedure, due to the broader and less predictable necrosis areas, have been recently overcome. However, whether MWA ability to generate a larger ablation zone will translate into a survival gain remains unknown. Other treatments, such as high-intensity focused ultrasound ablation, laser ablation, and cryoablation, are less investigated but showed promising results in early HCC patients and could be a valuable therapeutic option in

  3. Cryosurgery and needle ablation of renal lesions.

    PubMed

    Johnson, D B; Nakada, S Y

    2001-05-01

    Laparoscopic renal cryoablation is a minimally invasive alternative for treating renal tumors utilizing narrow probes cooled with a compressed gas such as argon or carbon dioxide. At this time, cryotherapy has shown the most promise as an alternative to partial nephrectomy as a nephron-sparing treatment for renal tumors. Radiofrequency ablation employs needle electrodes placed percutaneously directly into renal lesions to deliver energy, creating high temperatures leading to cell death. High-intensity focused ultrasound is a noninvasive technique in which focused ultrasound energy is applied to cause cell death within the focal zone. Microwave thermotherapy uses small applicators to deliver microwave energy to tissues, resulting in the generation of heat. Although RF, HIFU, and microwave thermotherapy show promise as energy sources for tumor ablation, they are in the early stages of development. Little is known about their acute and chronic histologic effects and long-term efficacy as a treatment for malignant disease. Further work is needed to develop cryosurgery and needle ablation in order to delineate what role these techniques will ultimately play in the management of RCC.

  4. Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes

    NASA Astrophysics Data System (ADS)

    Mosquera, Samuel Arba; Verma, Shwetabh

    2015-07-01

    The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C±1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8°C±0.8 (p=3.3E-53 to baseline), whereas the average was 9.0°C±1.5 for all no local frequency ablations (p=1.8E-35 to baseline, 1.6E-16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r2=0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r2=0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures.

  5. Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes.

    PubMed

    Arba Mosquera, Samuel; Verma, Shwetabh

    2015-07-01

    The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C±1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8°C±0.8 (p=3.3E-53 to baseline), whereas the average was 9.0°C±1.5 for all no local frequency ablations (p=1.8E-35 to baseline, 1.6E-16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r 2 =0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r 2 =0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures.

  6. In situ Diagnostics During Carbon Nanotube Production by Laser Ablation

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram

    1999-01-01

    The preliminary results of spectral analysis of the reaction zone during the carbon nanotube production by laser ablation method indicate synergetic dependence on dual laser setup. The emission spectra recorded from different regions of the laser ablated plume at different delay times from the laser pulses are used to map the temperatures of C2 and C3. These are compared with Laser Induced Fluorescence (LIF) spectra also obtained during production to model the growth mechanism of carbon nanotubes. Experiments conducted to correlate the spectral features with nanotube yields as a function of different production parameters will be discussed.

  7. OCDR guided laser ablation device

    DOEpatents

    Dasilva, Luiz B.; Colston, Jr., Bill W.; James, Dale L.

    2002-01-01

    A guided laser ablation device. The device includes a mulitmode laser ablation fiber that is surrounded by one or more single mode optical fibers that are used to image in the vicinity of the laser ablation area to prevent tissue damage. The laser ablation device is combined with an optical coherence domain reflectometry (OCDR) unit and with a control unit which initializes the OCDR unit and a high power laser of the ablation device. Data from the OCDR unit is analyzed by the control unit and used to control the high power laser. The OCDR images up to about 3 mm ahead of the ablation surface to enable a user to see sensitive tissue such as a nerve or artery before damaging it by the laser.

  8. Catheter Ablation for Ventricular Arrhythmias

    PubMed Central

    Nof, Eyal; Stevenson, William G; John, Roy M

    2013-01-01

    Catheter ablation has emerged as an important and effective treatment option for many recurrent ventricular arrhythmias. The approach to ablation and the risks and outcomes are largely determined by the nature of the severity and type of underlying heart disease. In patients with structural heart disease, catheter ablation can effectively reduce ventricular tachycardia (VT) episodes and implantable cardioverter defibrillator (ICD) shocks. For VT and symptomatic premature ventricular beats that occur in the absence of structural heart disease, catheter ablation is often effective as the sole therapy. Advances in catheter technology, imaging and mapping techniques have improved success rates for ablation. This review discusses current approaches to mapping and ablation for ventricular arrhythmias. PMID:26835040

  9. CT Mapping of the Distribution of Saline During Radiofrequency Ablation with Perfusion Electrodes

    SciTech Connect

    Gillams, A.R. Lees, W.R.

    2005-05-15

    Purpose. During radiofrequency (RF) ablation, adjunctive saline increases the size of the ablation zone and therefore electrodes that simultaneously deliver current and saline have been developed, but the addition of saline also results in an irregular ablation zone. Our aim was to study the distribution of saline during RF ablation. Methods. Four patients were treated: 3 with liver metastases and 1 with hepatocellular carcinoma (HCC). Two different perfusion electrodes were used: a high-perfusion-rate, straight electrode (Berchtold, Germany) and a low-perfusion-rate, expandable electrode (RITA Medical Systems, USA). The saline perfusate was doped with non-ionic contrast medium to render it visible on CT and the electrical conductivity was measured. CT scans were obtained of each electrode position prior to ablation and repeated after ablation. Contrast-enhanced CT was performed 18-24 hr later to demonstrate the ablation zone. All treatments were carried out according to the manufacturer's recommended protocol. Results. The addition of a small quantity of non-ionic contrast did not alter the electrical conductivity of the saline. Contrast-doped saline extravasated beyond the tumor in all 3 patients with metastases but was limited in the patient with HCC. In some areas where saline had extravasated there was reduced enhancement on contrast-enhanced CT consistent with tissue ablation. One patient treated with the high-perfusion-rate system sustained a jejunal perforation requiring surgery. Conclusion. Saline can extravasate beyond the tumor and with the high-perfusion-rate system this resulted in an undesirable extension of the ablation zone and a complication.

  10. Radiofrequency Ablation for Liver Cancer.

    PubMed

    Jacobs, Amy

    2015-01-01

    Interventional ablative technologies aided by imaging techniques such as ultrasonography, computed tomography, and magnetic resonance imaging have been crucial in managing patients with primary liver cancer and liver metastases over the past 20 years. Several ablative technologies have been used to treat liver cancer; however, radiofrequency ablation (RFA) has emerged as the most common ablative therapy for hepatic lesions, both in the United States and globally. RFA is the treatment of choice for patients who cannot have surgical resection of the liver. This article focuses on the role of imaging in RFA treatment of primary and metastatic hepatic lesions.

  11. Role of debris cover to control specific ablation of adjoining Batal and Sutri Dhaka glaciers in Chandra Basin (Himachal Pradesh) during peak ablation season

    NASA Astrophysics Data System (ADS)

    Sharma, Parmanand; Patel, Lavkush K.; Ravindra, Rasik; Singh, Ajit; K, Mahalinganathan; Thamban, Meloth

    2016-04-01

    As part of the on-going annual mass balance measurements on Batal and Sutri Dhaka glaciers, observations were made during peak ablation (August-September) season in 2013 to understand the response of debris covered and clean-ice (debris free) glacier surface to melting processes. Though, both the Batal and Sutri Dhaka glaciers have almost similar geographical disposition, Batal shows extensive debris cover (90% of the ablation area), while the latter is free from debris (only 5% of the ablation area). The thickness of debris in Batal glacier is inversely proportional to altitude, whereas Sutri Dhaka mostly experienced debris-free zone except snout area. Observation revealed that the vertical gradient of ablation rate in ablation area is contrastingly opposite in these two glaciers, reflecting significant control of debris thickness and their distribution over glacier surface on the ablation rates. While different thickness (2-100 cm) of debris have attenuated melting rates up to 70% of total melting, debris cover of <2 cm thickness has accelerated melting up to 10% of the total melting. Estimated melt ratio reveals that about 90% of the ablation area has experienced inhibited melting in Batal glacier, whereas only less than 5% ablation area of Sutri Dhaka has undergone inhibited melting. Comparison of topographical maps of 1962 with successive satellite images of the area demonstrates a terminus retreat of 373 ± 33.5 m and 579 ± 33.5 m for Batal and Sutri Dhaka glaciers for the period 1962-2013, respectively.

  12. Radiofrequency (electrosurgical) ablation of articular cartilage: a study in sheep.

    PubMed

    Turner, A S; Tippett, J W; Powers, B E; Dewell, R D; Mallinckrodt, C H

    1998-09-01

    The objective of this study was to examine the effect of a bipolar ablation probe on experimentally roughened articular cartilage and compare it with the traditional mechanical shaving technique using the knee joint of sheep. Twenty-eight skeletally mature ewes were divided randomly into two groups: one group was treated with a rotating shaving device and another group was treated using the bipolar ablation probe (Bipolar Arthroscopic Probe; Electroscope, Inc, Boulder, CO). Animals were killed at 0, 6, 12, and 24 weeks, and histological sections of the experimental limbs were compared with sections of the opposite limb using a modified Mankin scale. The following variables were used to determine scores: surface (0-6), cells (0-4), hypocellularity (0-3), matrix staining (transitional zone [0-4], radiate zone [0-4], and focal empty lacunae or hypereosinophilic cells (0-3). Differences in scores for all response variables were calculated as treated limb minus sham limb. Response variables were formed: score >0 recoded as 1 (favorable response treated better than sham), score of 0 recoded as 2 (neutral response no differences), and score <0 recoded as 3 (unfavorable response treated worse than sham). Bipolar ablative probe-treated limbs had 14.29% favorable responses and 35.71% favorable or neutral responses, whereas shave-treated limbs had 0% favorable and only 7.14% favorable or neutral responses. For all variables, bipolar ablative probe-treated limbs had more favorable responses. The less severe histological change in the bipolar ablative probe-treated joints compared with the shave-treated joints suggests that bipolar ablation of articular cartilage may be a better treatment for chondromalacia than the usual shaving methods of debridement. Further, there were no pathological changes in the subchondral bone.

  13. High temperature ablative foam

    NASA Technical Reports Server (NTRS)

    Liu, Matthew T. (Inventor)

    1992-01-01

    An ablative foam composition is formed of approximately 150 to 250 parts by weight polymeric isocyanate having an isocyanate functionality of 2.6 to 3.2; approximately 15 to 30 parts by weight reactive flame retardant having a hydroxyl number range from 200-260; approximately 10 to 40 parts by weight non-reactive flame retardant; approximately 10 to 40 parts by weight nonhydrolyzable silicone copolymer having a hydroxyl number range from 75-205; and approximately 3 to 16 parts by weight amine initiated polyether resin having an isocyanate functionality greater than or equal to 3.0 and a hydroxyl number range from 400-800.

  14. Matricectomy and nail ablation.

    PubMed

    Baran, Robert; Haneke, Eckart

    2002-11-01

    Matricectomy refers to the complete extirpation of the nail matrix, resulting in permanent nail loss. Usually however, matricectomy is only partial, restricted to one or both lateral horns of the matrix. Nail ablation is the definitive removal of the entire nail organ. The most important common denominator in the successful matricectomy is the total removal or destruction of the matrix tissue. Matricectomy may be indicated for the management of onychauxis, onychogryphosis, congenital nail dystrophies, and chronic painful nail, such as recalcitrant ingrown toenail or split within the medial or lateral one-third of the nail.

  15. Laser ablation in analytical chemistry.

    PubMed

    Russo, Richard E; Mao, Xianglei; Gonzalez, Jhanis J; Zorba, Vassilia; Yoo, Jong

    2013-07-02

    In 2002, we wrote an Analytical Chemistry feature article describing the Physics of Laser Ablation in Microchemical Analysis. In line with the theme of the 2002 article, this manuscript discusses current issues in fundamental research, applications based on detecting photons at the ablation site (LIBS and LAMIS) and by collecting particles for excitation in a secondary source (ICP), and directions for the technology.

  16. In situ iron isotope ratio determination using UV-femtosecond laser ablation with application to hydrothermal ore formation processes

    NASA Astrophysics Data System (ADS)

    Horn, Ingo; von Blanckenburg, Friedhelm; Schoenberg, Ronny; Steinhoefel, Grit; Markl, Gregor

    2006-07-01

    The feasibility of in situ stable Fe isotope ratio measurements using UV-femtosecond laser ablation connected to a multiple-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) has been investigated. Different types of matrices, independently determined by solution MC-ICP-MS after chromatographic separation of Fe, have been analysed by laser ablation using the isotopically certified iron reference material IRMM-014 as the bracketing standard. The samples have been pure iron metal (JM Puratronic), Fe-meteorites (North Chile, Glenormiston and Toluca), the meteorite phases kamacite and taenite in Toluca and Fe-sulphides. Furthermore, Fe isotope ratios from hydrothermal hematite, siderite and goethite from an old mining area in the Schwarzwald, Germany, and of magnetite from the metamorphic Biwabik iron formation have been determined. The results show that a precision of better than 0.1‰ (2 sigma) can be achieved with laser ablation and that all the results obtained agree with those determined by solution ICP to better than 0.1‰. This precision and accuracy is achievable in both raster and spot ablation mode. A matrix-matched bracketing standard is not required , and all these materials can be measured accurately against a metal standard. The hydrothermal minerals show significant Fe isotope zonations. In some samples the range of δ56Fe in a single aggregate encompasses the entire spectrum of ratios found by bulk solution analyses in multiple samples distributed over the whole mining district. For example, isotopic zonations found in secondary fibrous hematites show a continuous change in the δ56Fe values from -0.5‰ in the core to -1.8‰ in the rim. Primary hydrothermal siderite shows the reverse pattern with lighter values in the core than in the rim. While the siderite is thought to record primary fluid histories, the hematite pattern is interpreted as a reworked isotopic signature generated by oxic dissolution of primary zoned siderite and

  17. Simulation of Pellet Ablation

    NASA Astrophysics Data System (ADS)

    Parks, P. B.; Ishizaki, Ryuichi

    2000-10-01

    In order to clarify the structure of the ablation flow, 2D simulation is carried out with a fluid code solving temporal evolution of MHD equations. The code includes electrostatic sheath effect at the cloud interface.(P.B. Parks et al.), Plasma Phys. Contr. Fusion 38, 571 (1996). An Eulerian cylindrical coordinate system (r,z) is used with z in a spherical pellet. The code uses the Cubic-Interpolated Psudoparticle (CIP) method(H. Takewaki and T. Yabe, J. Comput. Phys. 70), 355 (1987). that divides the fluid equations into non-advection and advection phases. The most essential element of the CIP method is in calculation of the advection phase. In this phase, a cubic interpolated spatial profile is shifted in space according to the total derivative equations, similarly to a particle scheme. Since the profile is interpolated by using the value and the spatial derivative value at each grid point, there is no numerical oscillation in space, that often appears in conventional spline interpolation. A free boundary condition is used in the code. The possibility of a stationary shock will also be shown in the presentation because the supersonic ablation flow across the magnetic field is impeded.

  18. Planning Irreversible Electroporation in the Porcine Kidney: Are Numerical Simulations Reliable for Predicting Empiric Ablation Outcomes?

    SciTech Connect

    Wimmer, Thomas Srimathveeravalli, Govindarajan; Gutta, Narendra; Ezell, Paula C.; Monette, Sebastien; Maybody, Majid; Erinjery, Joseph P.; Durack, Jeremy C.; Coleman, Jonathan A.; Solomon, Stephen B.

    2015-02-15

    PurposeNumerical simulations are used for treatment planning in clinical applications of irreversible electroporation (IRE) to determine ablation size and shape. To assess the reliability of simulations for treatment planning, we compared simulation results with empiric outcomes of renal IRE using computed tomography (CT) and histology in an animal model.MethodsThe ablation size and shape for six different IRE parameter sets (70–90 pulses, 2,000–2,700 V, 70–100 µs) for monopolar and bipolar electrodes was simulated using a numerical model. Employing these treatment parameters, 35 CT-guided IRE ablations were created in both kidneys of six pigs and followed up with CT immediately and after 24 h. Histopathology was analyzed from postablation day 1.ResultsAblation zones on CT measured 81 ± 18 % (day 0, p ≤ 0.05) and 115 ± 18 % (day 1, p ≤ 0.09) of the simulated size for monopolar electrodes, and 190 ± 33 % (day 0, p ≤ 0.001) and 234 ± 12 % (day 1, p ≤ 0.0001) for bipolar electrodes. Histopathology indicated smaller ablation zones than simulated (71 ± 41 %, p ≤ 0.047) and measured on CT (47 ± 16 %, p ≤ 0.005) with complete ablation of kidney parenchyma within the central zone and incomplete ablation in the periphery.ConclusionBoth numerical simulations for planning renal IRE and CT measurements may overestimate the size of ablation compared to histology, and ablation effects may be incomplete in the periphery.

  19. Thermal response and ablation characteristics of light weight ceramic ablators

    NASA Technical Reports Server (NTRS)

    Tran, Huy K.; Rasky, Daniel J.; Esfahani, Lili

    1993-01-01

    An account is given of the thermal performance and ablation characteristics of the NASA-Ames Lightweight Ceramic Ablators (LCAs) in supersonic, high-enthalpy convective environments, which use low density ceramic or carbon fiber matrices as substrates for main structural support, with organic resin fillers. LCA densities are in the 0.224-1.282 g/cu cm range. In-depth temperature data have been obtained to determine thermal penetration depths and conductivity. The addition of SiC and PPMA is noted to significantly improve the ablation performance of LCAs with silica substrates. Carbon-based LCAs are the most mass-efficient at high flux levels.

  20. Considering Angle Selection When Using Ultrasound Electrode Displacement Elastography to Evaluate Radiofrequency Ablation of Tissues

    PubMed Central

    Li, Qiang; Chen, Pin-Yu; Wang, Chiao-Yin; Liu, Hao-Li; Teng, Jianfu

    2014-01-01

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive treatment to thermally destroy tumors. Ultrasound-based electrode-displacement elastography is an emerging technique for evaluating the region of RFA-induced lesions. The angle between the imaging probe and the RFA electrode can influence electrode-displacement elastography when visualizing the ablation zone. We explored the angle effect on electrode-displacement elastography to measure the ablation zone. Phantoms embedded with meatballs were fabricated and then ablated using an RFA system to simulate RFA-induced lesions. For each phantom, a commercial ultrasound scanner with a 7.5 MHz linear probe was used to acquire raw image data at different angles, ranging from 30° to 90° at increments of 10°, to construct electrode-displacement images and facilitate comparisons with tissue section images. The results revealed that the ablation regions detected using electrode-displacement elastography were highly correlated with those from tissue section images when the angle was between 30° and 60°. However, the boundaries of lesions were difficult to distinguish, when the angle was larger than 60°. The experimental findings suggest that angle selection should be considered to achieve reliable electrode-displacement elastography to describe ablation zones. PMID:24971347

  1. Formation of tribological structures by laser ablation

    NASA Astrophysics Data System (ADS)

    Schilling, Niels; Paschke, Mike; Hendow, Sami T.; Klotzbach, Udo

    2012-03-01

    Many technical applications can benefit from the use of tribological structures in minimizing abrasive material wear and energy consumption without the integration of additional materials in a working assembly. Especially in lubricated friction systems, the tribological character can be significantly improved through the addition of oriented and repetitive microstructure. In this study, experimental tests are discussed for a small range of structure dimensions to verify the effect of optimizing the tribological contact performance. A nanosecond pulsed fiber laser is used to create various test structures with different sizes and form. The quality of the fabricated surface pattern, particularly form correctness, feathering and material modification effects of the ablated area is characterized and optimized. The influence of pulse duration, pulse energy and pulse delay using normal pulsing is presented and compared to various burst modes.

  2. Ex Vivo Experiment of Saline-Enhanced Hepatic Bipolar Radiofrequency Ablation with a Perfused Needle Electrode: Comparison with Conventional Monopolar and Simultaneous Monopolar Modes

    SciTech Connect

    Lee, Jeong Min Kim, Se Hyung; Han, Joon Koo; Sohn, Kyu Li; Choi, Byung Ihn

    2005-04-15

    The purpose of this study was to validate the saline-enhanced bipolar radiofrequency ablation (RFA) technique using a perfused electrode to increase RF-created coagulation necrosis, to compare that technique with monopolar RFAs and to find appropriate concentrations and volumes of perfused NaCl solution for the bipolar RFA. A total of 90 ablations were performed in explanted bovine livers. In the initial experiments to determine appropriate conditions for bipolar RFA, we created five thermal ablation zones in each condition, with instillations of varied concentrations (0.9-36%) or injection rates (30 mL/hr-120 mL/hr) of NaCl solution. After placement of one or two 16-gauge open-perfused electrodes into bovine livers, the NaCl solution was instilled into the tissue through the electrode. In the second part of the study, 10 ablation zones were created using one or two perfused electrodes for each of five groups under different conditions: a conventional monopolar mode with 0.9% NaCl solution (group A) or with 6% NaCl solution (group B), a simultaneous monopolar mode with 6% NaCl solution (group C) and a bipolar mode with 6% NaCl solution (groups D and E). RF was applied to each electrode for 20 min in groups A, B, C, and E, or for 10 min in group D. During RFA, we measured the tissue temperature 15 mm from the electrode. The temperature changes during the RFA and the dimensions of the ablation zones were compared among the groups. Bipolar RFA created larger short-axis diameters of coagulation necrosis with 6% NaCl solution (35.8 {+-} 15 mm) than with 0.9% NaCl solution (17 {+-} 9.7 mm) (P < 0.05). However, concentrations of NaCl solution above 6% did not further increase the extent of coagulation necrosis. In addition, bipolar RFA with 6% NaCl solution instillation at a rate of 1.0 mL/min (37.9 {+-} 5.4 mm) or 2.0 mL/min (35.6 {+-} 9.3 mm) produced larger diameters at the mid-point between the electrodes of the ablated lesion than did 0.5 mL/min (25.8 {+-} 9.3 mm) (P

  3. Irreversible electroporation ablation area enhanced by synergistic high- and low-voltage pulses

    PubMed Central

    2017-01-01

    Irreversible electroporation (IRE) produced by a pulsed electric field can ablate tissue. In this study, we achieved an enhancement in ablation area by using a combination of short high-voltage pulses (HVPs) to create a large electroporated area and long low-voltage pulses (LVPs) to ablate the electroporated area. The experiments were conducted in potato tuber slices. Slices were ablated with an array of four pairs of parallel steel electrodes using one of the following four electric pulse protocols: HVP, LVP, synergistic HVP+LVP (SHLVP) or LVP+HVP. Our results showed that the SHLVPs more effectively necrotized tissue than either the HVPs or LVPs, even when the SHLVP dose was the same as or lower than the HVP or LVP doses. The HVP and LVP order mattered and only HVPs+LVPs (SHLVPs) treatments increased the size of the ablation zone because the HVPs created a large electroporated area that was more susceptible to the subsequent LVPs. Real-time temperature change monitoring confirmed that the tissue was non-thermally ablated by the electric pulses. Theoretical calculations of the synergistic effects of the SHLVPs on tissue ablation were performed. Our proposed SHLVP protocol provides options for tissue ablation and may be applied to optimize the current clinical IRE protocols. PMID:28253331

  4. [New techniques of tumor ablation (microwaves, electroporation)].

    PubMed

    de Baere, T

    2011-09-01

    Since the introduction of radiofrequency tumor ablation of liver tumors in the late 1990s, local destructive therapies have been applied to lung, renal and bone lesions. In addition, new techniques have been introduced to compensate for the limitations of radiofrequency ablation, namely the reduced rate of complete ablation for tumors larger than 3 cm and tumors near vessels larger than 3 mm. Microwave ablation is currently evolving rapidly. While it is a technique based on thermal ablation similar to radiofrequency ablation, there are significant differences between both techniques. Electroporation, of interest because of the non-thermal nature of the ablation process, also is under evaluation.

  5. Ablative heat shield design for space shuttle

    NASA Technical Reports Server (NTRS)

    Seiferth, R. W.

    1973-01-01

    Ablator heat shield configuration optimization studies were conducted for the orbiter. Ablator and reusable surface insulation (RSI) trajectories for design studies were shaped to take advantage of the low conductance of ceramic RSI and high temperature capability of ablators. Comparative weights were established for the RSI system and for direct bond and mechanically attached ablator systems. Ablator system costs were determined for fabrication, installation and refurbishment. Cost penalties were assigned for payload weight penalties, if any. The direct bond ablator is lowest in weight and cost. A mechanically attached ablator using a magnesium subpanel is highly competitive for both weight and cost.

  6. Magnetic and robotic navigation for catheter ablation: "joystick ablation".

    PubMed

    Ernst, Sabine

    2008-10-01

    Catheter ablation has become the treatment of choice to cure various arrhythmias in the last decades. The newest advancement of this general concept is made on the navigation ability using remote-controlled ablation catheters. This review summarizes the concept of the two currently available systems, followed by a critical review of the published clinical reports for each system, respectively. Despite the limited amount of data, an attempt to compare the two systems is made.

  7. 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.

  8. Increasing power versus duration for radiofrequency ablation with a high superfusate flow: implications for pulmonary vein ablation?

    PubMed

    Guy, Duncan J R; Boyd, Anita; Thomas, Stuart P; Ross, David L

    2003-06-01

    Radiofrequency (RF) ablation of pulmonary veins (PVs) is a new treatment for atrial fibrillation. Low energy ablation is usually used for this procedure. The effect of superfusate flow on lesion formation in this setting has not been studied previously. We examined lesion dimensions and intramural temperatures with varying powers and duration of RF application in this high flow environment. Ablation of fresh bovine hearts was performed with a 4-mm tip RF catheter in temperature control mode, target temperature 50 degrees C. At power levels of 20 W, 30 W, 40 W, and 50 W, effects of PV flow (no flow or 1 L/min) and 60- and 120-second durations were tested. Tissue temperatures were recorded at depths of 1, 4, 7, and 10 mm. Without flow, no lesions were created. The lowest power setting for lesion creation was 30 W at 60 seconds and 20 W at 120 seconds. Increasing power from 30 W to 50 W for 60 seconds increased lesion depth 0.7 mm (SE 0.3), P = 0.03 and 2.5 mm (SE 0.6), P = 0.003, at 120 seconds. Increasing RF application duration from 60 to 120 seconds increased depth for 30 W by 0.9 mm (SE 0.5), P = NS, 40 W 1.7 mm (SE 0.4), P = 0.002, and 50 W 2.6 mm (SE 0.5), P < 0.001. Power of 50 W for 60 seconds and >30 W for 120 seconds created lesions deeper than the wall thickness of a PV. Flow is necessary for creation of lesions with low power, low tip temperature RF ablation. When a resistant site to ablation is encountered, increasing duration of ablation is best for increasing lesion depth. Higher power has the potential to create lesions deeper than the PV wall and may increase the risk of complications.

  9. Real-time calibration of temperature estimates during radiofrequency ablation.

    PubMed

    Varghese, T; Daniels, M J

    2004-07-01

    Radiofrequency ablation is an interstitial focal ablative therapy that can be used in a percutaneous fashion and permits in situ destruction of hepatic tumors. Recurrence rates after rf therapy are as high as 34-55%, due to difficulties in accurately identifying the zone of necrosis (thermal lesion) because of the low intrinsic acoustic contrast between normal and ablated liver tissue. Our goal is to provide real-time ultrasonic tracking of temperature changes over the large range of temperatures traditionally used (40-100 degrees C) in rfablation procedures using an external ultrasound transducer. Temperature estimates are obtained using a cross-correlation algorithm applied to rf ultrasound echo signal data acquired at discrete intervals during heating. Apparent tissue displacement estimates obtained at these discrete time-intervals are accumulated to obtain a cumulative displacement map, whose gradient provides after appropriate scaling provides a temperature map at the specified elapsed ablation duration. Temperature maps are used to display the initial temperature rise and to continuously update a thermal map of the treated region. In this paper, we develop calibration curves that relate the echo shift due to the change in the speed of sound and thermal expansion to the corresponding temperature increase on in-vitro tissue specimens. These calibration curves can then be utilized for the real time calibration and analysis of temperature estimates obtained from the rf echo signals during ablation. Temperature maps obtained using the calibration curve compare favorably to temperature estimates observed using the invasive thermosensor readings on the ablation electrode and previous results that utilized a linear calibration factor.

  10. In Vivo Evaluation of Lung Microwave Ablation in a Porcine Tumor Mimic Model

    SciTech Connect

    Planche, Olivier; Teriitehau, Christophe; Boudabous, Sana; Robinson, Joey Marie; Rao, Pramod; Deschamps, Frederic; Farouil, Geoffroy; Baere, Thierry de

    2013-02-15

    To evaluate the microwave ablation of created tumor mimics in the lung of a large animal model (pigs), with examination of the ablative synergy of multiple antennas. Fifty-six tumor-mimic models of various sizes were created in 15 pigs by using barium-enriched minced collected thigh muscle injected into the lung of the same animal. Tumors were ablated under fluoroscopic guidance by single-antenna and multiple-antenna microwaves. Thirty-five tumor models were treated in 11 pigs with a single antenna at 75 W for 15 min, with 15 measuring 20 mm in diameter, 10 measuring 30 mm, and 10 measuring 40 mm. Mean circularity of the single-antenna ablation zones measured 0.64 {+-} 0.12, with a diameter of 35.7 {+-} 8.7 mm along the axis of the antenna and 32.7 {+-} 12.8 mm perpendicular to the feeding point. Multiple-antenna delivery of 75 W for 15 min caused intraprocedural death of 2 animals; modified protocol to 60 W for 10 min resulted in an ablation zone with a diameter of 43.0 {+-} 7.7 along the axis of the antenna and 54.8 {+-} 8.5 mm perpendicular to the feeding point; circularity was 0.70 {+-} 0.10. A single microwave antenna can create ablation zones large enough to cover lung tumor mimic models of {<=}4 cm with no heat sink effect from vessels of {<=}6 mm. Synergic use of 3 antennas allows ablation of larger volumes than single-antenna or radiofrequency ablation, but great caution must be taken when 3 antennas are used simultaneously in the lung in clinical practice.

  11. Evaluation of a Thermoprotective Gel for Hydrodissection During Percutaneous Microwave Ablation: In Vivo Results

    SciTech Connect

    Moreland, Anna J. Lubner, Meghan G. Ziemlewicz, Timothy J. Kitchin, Douglas R. Hinshaw, J. Louis Johnson, Alexander D. Lee, Fred T. Brace, Christopher L.

    2015-06-15

    PurposeTo evaluate whether thermoreversible poloxamer 407 15.4 % in water (P407) can protect non-target tissues adjacent to microwave (MW) ablation zones in a porcine model.Materials and MethodsMW ablation antennas were placed percutaneously into peripheral liver, spleen, or kidney (target tissues) under US and CT guidance in five swine such that the expected ablation zones would extend into adjacent diaphragm, body wall, or bowel (non-target tissues). For experimental ablations, P407 (a hydrogel that transitions from liquid at room temperature to semi-solid at body temperature) was injected into the potential space between target and non-target tissues, and the presence of a gel barrier was verified on CT. No barrier was used for controls. MW ablation was performed at 65 W for 5 min. Thermal damage to target and non-target tissues was evaluated at dissection.ResultsAntennas were placed 7 ± 3 mm from the organ surface for both control and gel-protected ablations (p = 0.95). The volume of gel deployed was 49 ± 27 mL, resulting in a barrier thickness of 0.8 ± 0.5 cm. Ablations extended into non-target tissues in 12/14 control ablations (mean surface area = 3.8 cm{sup 2}) but only 4/14 gel-protected ablations (mean surface area = 0.2 cm{sup 2}; p = 0.0005). The gel barrier remained stable at the injection site throughout power delivery.ConclusionWhen used as a hydrodissection material, P407 protected non-targeted tissues and was successfully maintained at the injection site for the duration of power application. Continued investigations to aid clinical translation appear warranted.

  12. Infrared laser ablation sample transfer for MALDI imaging.

    PubMed

    Park, Sung-Gun; Murray, Kermit K

    2012-04-03

    An infrared laser was used to ablate material from tissue sections under ambient conditions for direct collection on a matrix assisted laser desorption ionization (MALDI) target. A 10 μm thick tissue sample was placed on a microscope slide and was mounted tissue-side down between 70 and 450 μm from a second microscope slide. The two slides were mounted on a translation stage, and the tissue was scanned in two dimensions under a focused mid-infrared (IR) laser beam to transfer material to the target slide via ablation. After the material was transferred to the target slide, it was analyzed using MALDI imaging using a tandem time-of-flight mass spectrometer. Images were obtained from peptide standards for initial optimization of the system and from mouse brain tissue sections using deposition either onto a matrix precoated target or with matrix addition after sample transfer and compared with those from standard MALDI mass spectrometry imaging. The spatial resolution of the transferred material is approximately 400 μm. Laser ablation sample transfer provides several new capabilities not possible with conventional MALDI imaging including (1) ambient sampling for MALDI imaging, (2) area to spot concentration of ablated material, (3) collection of material for multiple imaging analyses, and (4) direct collection onto nanostructure assisted laser desorption ionization (NALDI) targets without blotting or ultrathin sections.

  13. Safety Zones

    EPA Pesticide Factsheets

    These are established primarily to reduce the accidental spread of hazardous substances by workers or equipment from contaminated areas to clean areas. They include the exclusion (hot) zone, contamination reduction (warm) zone, and support (cold) zone.

  14. Ablation dynamics in laser sclerotomy ab externo

    NASA Astrophysics Data System (ADS)

    Brinkmann, Ralf; Droege, Gerit; Mohrenstecher, Dirk; Scheu, M.; Birngruber, Reginald

    1996-01-01

    Laser sclerostomy ab externo with flashlamp excited mid-IR laser systems emitting in the 2-3 micrometer spectral range is in phase II clinical trials. Although acutely high success rates were achieved, the restenosis rate after several months is about 40%. Laser pulses of several hundreds of microseconds, known to induce thermo-mechanical explosive evaporation were used for this procedure. We investigated the ablation dynamics in tissue and the cavitation bubble dynamics in water by means of an Er:YAG laser system to estimate the extent of mechanical damage zones in the sclera and in the anterior chamber, which may contribute to the clinical failure. We found substantial mechanical tissue deformation during the ablation process caused by the cavitation effects. Stress waves up to several bar generated by explosive evaporization were measured. The fast mechanical stretching and collapsing of the scleral tissue induced by cavitation resulted in tissue dissection as could be proved by flash photography and histology. The observed high restenosis might be a result of a subsequent enhanced wound healing process. Early fistula occlusions due to iris adherences, observed in about 20% of the clinical cases may be attributed to intraocular trauma induced by vapor bubble expansion through the anterior chamber after scleral perforation. An automatic feedback system minimizing adverse effects by steering and terminating the laser process during scleral fistulization is demonstrated. Moreover, a new approach in laser sclerostomy ab externo is presented using a cw-IR laser diode system emitting at the 1.94 micrometer mid-IR water absorption peak. This system was used in vitro and showed smaller damage zones compared to the pulsed laser radiation.

  15. Focal Hydrothermal Ablation: Preliminary Investigation of a New Concept

    SciTech Connect

    Roy, Sumit

    2013-08-01

    PurposeTo determine whether focal tissue ablation is possible with interstitial instillation of steam.MethodsFresh swine livers were used. Through a 20 gauge needle, steam was instilled every 5 s, 3 (n = 5), 6 (n = 5), 9 (n = 5), or 12 (n = 5 + 5) times in a liver lobe. The ablated zones were sectioned parallel (n = 20) or perpendicular (n = 5) to the needle track. The longitudinal long and short axis diameters, or transverse long and short axis diameters of areas with discoloration on macroscopic examination, were measured. The experiment was repeated in vivo on a pig. Steam instillation was performed once every 5 s for 5 min in the liver (n = 3) and in muscle (n = 4), and temperature changes at three neighboring sites were monitored. Long and short axis diameters of the discolored areas were measured.ResultsA well-defined area of discoloration was invariably present at the site of steam instillation. The median longitudinal long axis diameter were 2.0, 2.5, 2.5, and 3.5 cm for 3, 6, 9, and 12 steam instillations in vitro, while median short axis diameters were 1.0, 1.5, 1.5, and 1.5 cm, respectively. Six attempts at ablation in vivo could be successfully completed. The long axis diameters of the ablated zones in the liver were 7.0 and 8.0 cm, while in muscle it ranged from 5.5 to 7.0 cm.ConclusionInstillation of steam in the liver in vitro and in vivo, and in muscle in vivo rapidly leads to circumscribed zones of coagulation necrosis.

  16. Computed Tomography-Guided Radiofrequency Ablation Following Transcatheter Arterial Embolization in Treatment of Large Hepatic Hemangiomas

    PubMed Central

    Ji, Jiansong; Gao, Jun; Zhao, Lizhen; Tu, Jianfei; Song, Jingjing; Sun, Wenbing

    2016-01-01

    Abstract The aim of the study was to evaluate the feasibility, safety, and efficacy of computed tomography (CT)-guided radiofrequency (RF) ablation combined with transcatheter arterial embolization (TAE) to treat large (≥10 cm) hepatic hemangiomas. We retrospectively reviewed our sequential experience with 15 large hepatic hemangiomas in 15 patients. The mean diameter of the 15 hemangiomas was 13.0 ± 2.2 cm (10.0–16.0 cm). RF ablation combined with TAE treatment was performed successfully in all patients. The mean diameter of the hemangiomas decreased from 13.0 ± 2.2 to 7.1 ± 2.0 cm (P < 0.001) after TAE treatment. Out of 15 hepatic hemangiomas, 14 (93.3%) showed no enhancement on CT or MRI indicating complete ablation after RF treatment. The mean diameter of the ablation zone decreased to 6.1 ± 2.0 cm 1 month after ablation and further decreased to 4.9 ± 1.6 cm 6 months after ablation. There were 6 complications related to the ablation in 4 patients. According to the Dindo–Clavien classification, all the complications were minor (Grade I). RF ablation combined with TAE is a safe and effective treatment for large hepatic hemangiomas. TAE can improve the disruption of lesion blood supply and reduce lesion size to facilitate subsequent RF ablation and reduce the risk of ablation-related complications. PMID:27082617

  17. Computed Tomography-Guided Radiofrequency Ablation Following Transcatheter Arterial Embolization in Treatment of Large Hepatic Hemangiomas.

    PubMed

    Ji, Jiansong; Gao, Jun; Zhao, Lizhen; Tu, Jianfei; Song, Jingjing; Sun, Wenbing

    2016-04-01

    The aim of the study was to evaluate the feasibility, safety, and efficacy of computed tomography (CT)-guided radiofrequency (RF) ablation combined with transcatheter arterial embolization (TAE) to treat large (≥10 cm) hepatic hemangiomas. We retrospectively reviewed our sequential experience with 15 large hepatic hemangiomas in 15 patients. The mean diameter of the 15 hemangiomas was 13.0 ± 2.2 cm (10.0-16.0 cm). RF ablation combined with TAE treatment was performed successfully in all patients. The mean diameter of the hemangiomas decreased from 13.0 ± 2.2 to 7.1 ± 2.0 cm (P < 0.001) after TAE treatment. Out of 15 hepatic hemangiomas, 14 (93.3%) showed no enhancement on CT or MRI indicating complete ablation after RF treatment. The mean diameter of the ablation zone decreased to 6.1 ± 2.0 cm 1 month after ablation and further decreased to 4.9 ± 1.6 cm 6 months after ablation. There were 6 complications related to the ablation in 4 patients. According to the Dindo-Clavien classification, all the complications were minor (Grade I). RF ablation combined with TAE is a safe and effective treatment for large hepatic hemangiomas. TAE can improve the disruption of lesion blood supply and reduce lesion size to facilitate subsequent RF ablation and reduce the risk of ablation-related complications.

  18. A mathematical framework for minimally invasive tumor ablation therapies.

    PubMed

    Hall, Sheldon K; Ooi, Ean Hin; Payne, Stephen J

    2014-01-01

    Minimally invasive tumor ablations (MITAs) are an increasingly important tool in the treatment of solid tumors across multiple organs. The problems experienced in modeling different types of MITAs are very similar, but the development of mathematical models is mostly performed in isolation according to modality. Fundamental research into the modeling of specific types of MITAs is indeed required, but to choose the optimal treatment for an individual the primary clinical requirement is to have reliable predictions for a range of MITAs. In this review of the mathematical modeling of MITAs 4 modalities are considered: radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation. The similarities in the mathematical modeling of these treatments are highlighted, and the analysis of the models within a general framework is discussed. This will aid in developing a deeper understanding of the sensitivity of MITA models to physiological parameters and the impact of uncertainty on predictions of the ablation zone. Through robust validation and analysis of the models it will be possible to choose the best model for a given application. This is important because many different models exist with no objective comparison of their performance. The collection of relevant in vivo experimental data is also critical to parameterize such models accurately. This approach will be necessary to translate the field into clinical practice.

  19. Silver nano-entities through ultrafast double ablation in aqueous media for surface enhanced Raman scattering and photonics applications

    NASA Astrophysics Data System (ADS)

    Krishna Podagatlapalli, G.; Hamad, Syed; Tewari, Surya P.; Sreedhar, S.; Prasad, Muvva D.; Venugopal Rao, S.

    2013-02-01

    We have fabricated stable silver nanoparticles (NPs) and nanostructures (NSs) effectively through double ablation of bulk silver substrate immersed in double distilled water using ˜2 ps laser pulses. The effects of multiple/double/single ablation on silver substrates via surface morphology studies along with average size distribution of Ag NPs were investigated. Prepared Ag NPs in solution exhibited yellow color with an absorption peak near 410 nm, assigned to localized surface Plasmon resonance of nano-sized silver. Depending on the ablation parameters average sizes observed were ˜13 nm/˜17 nm in multiple/double ablation case and ˜7 nm in single ablation case. High resolution transmission electron microscope studies highlighted that most of the Ag NPs were spherical and polycrystalline in nature. Surface morphology of the substrates was characterized by field emission scanning electron microscope and atomic force microscope. A different scenario was observed in the double ablation case compared to single/multiple ablation case. Double ablation resulted in dome like NSs on the substrate with dimensions of few hundreds of nanometers while single ablation did not. Nonlinear optical (NLO) properties of Ag NPs were investigated using Z-scan technique with ˜2 ps pulses and corresponding NLO coefficients were obtained. Surface enhanced Raman scattering (SERS) studies on multiple/double ablated Ag substrates with adsorbed Rhodamine 6G molecules were carried out using excitation wavelengths of 532 nm, 785 nm, and three orders of enhancement in Raman signal intensity was observed. Furthermore, influence of laser fluence on the fabrication of SERS active Ag substrates with double ablation was also investigated. In this case, Raman spectra of adsorbed Research Department eXplosive (RDX) molecules on ablated surfaces were recorded for 532 nm and 785 nm excitation. Enhancements up to 460 were observed from substrates fabricated at fluences of 12 J/cm2, 16 J/cm2 with

  20. Imaging Features of Radiofrequency Ablation with Heat-Deployed Liposomal Doxorubicin in Hepatic Tumors

    SciTech Connect

    Hong, Cheng William Chow, Lucy; Turkbey, Evrim B.; Lencioni, Riccardo; Libutti, Steven K.; Wood, Bradford J.

    2016-03-15

    IntroductionThe imaging features of unresectable hepatic malignancies in patients who underwent radiofrequency ablation (RFA) in combination with lyso-thermosensitive liposomal doxorubicin (LTLD) were determined.Materials and MethodsA phase I dose escalation study combining RFA with LTLD was performed with peri- and post- procedural CT and MRI. Imaging features were analyzed and measured in terms of ablative zone size and surrounding penumbra size. The dynamic imaging appearance was described qualitatively immediately following the procedure and at 1-month follow-up. The control group receiving liver RFA without LTLD was compared to the study group in terms of imaging features and post-ablative zone size dynamics at follow-up.ResultsPost-treatment scans of hepatic lesions treated with RFA and LTLD have distinctive imaging characteristics when compared to those treated with RFA alone. The addition of LTLD resulted in a regular or smooth enhancing rim on T1W MRI which often correlated with increased attenuation on CT. The LTLD-treated ablation zones were stable or enlarged at follow-up four weeks later in 69 % of study subjects as opposed to conventional RFA where the ablation zone underwent involution compared to imaging acquired immediately after the procedure.ConclusionThe imaging features following RFA with LTLD were different from those after standard RFA and can mimic residual or recurrent tumor. Knowledge of the subtle findings between the two groups can help avoid misinterpretation and proper identification of treatment failure in this setting. Increased size of the LTLD-treated ablation zone after RFA suggests the ongoing drug-induced biological effects.

  1. Pilot Study to Assess Safety and Clinical Outcomes of Irreversible Electroporation for Partial Gland Ablation in Men with Prostate Cancer

    PubMed Central

    Murray, Katie S.; Ehdaie, Behfar; Musser, John; Mashni, Joseph; Srimathveeravalli, Govindarajan; Durack, Jeremy C.; Solomon, Stephen B.; Coleman, Jonathan A.

    2016-01-01

    Purpose Partial prostate gland ablation is a strategy to manage localized prostate cancer. Irreversible electroporation can ablate localized soft tissues. We sought to describe 30- and 90-day complications and intermediate-term functional outcomes in men undergoing prostate gland ablation using irreversible electroporation. Materials and Methods We reviewed the charts of 25 patients with prostate cancer who underwent prostate gland ablation using irreversible electroporation as a primary procedure and who were followed for at least 6 months. Results Median follow-up was 10.9 months. Grade 3 complications occurred in 2 patients including epididymitis (1) and urinary tract infection (1). Fourteen patients experienced grade ≤ 2 complications, mainly transient urinary symptoms, hematuria, and urinary tract infections. Of 25 patients, 4 (16%) had cancer in the zone of ablation on routine follow-up biopsy at 6 months. Of those with normal urinary function at baseline, 88% and 94% reported normal urinary function at 6 and 12 months after prostate gland ablation, respectively. By 12 months, only 1 patient with normal erectile function at baseline reported new difficulty with potency and only 2 patients (8%) required a pad for urinary incontinence. Conclusions Prostate gland ablation with irreversible electroporation is feasible and safe in selected men with localized prostate cancer. Intermediate-term urinary and erectile function outcomes appear reasonable. Irreversible electroporation is effective in ablation of tumor-bearing prostate tissue, as a majority of men had no evidence of residual cancer on biopsy 6 months after prostate gland ablation. PMID:27113966

  2. Comparative study on laser tissue ablation between PV and HPS lasers

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Jebens, David; Mitchell, Gerald; Koullick, Ed

    2008-02-01

    Laser therapy for obstructive benign prostatic hyperplasia (BPH) has gained broad adoption due to effective tissue removal, immediate hemostasis, and minor complications. The aim of this study is to quantitatively compare ablation characteristics of PV (Photoselective Vaporization) and the newly introduced HPS (High Performance System) 532 nm lasers. Bovine prostatic tissues were ablated in vitro, using a custom-made scanning system. Laser-induced volume produced by two lasers was quantified as a function of applied power, fiber working distance (WD), and treatment speed. Given the same power of 80 W and speed of 4 mm/s, HPS created up to 50 % higher tissue ablation volume than PV did. PV induced a rapid decrease of ablation volume when WD increased from 0.5 mm to 3 mm while HPS yielded almost constant tissue removal up to 3 mm for both 80 W and 120 W. As the treatment speed increased, both lasers reached saturation in tissue ablation volume. Lastly, both PV and HPS lasers exhibited approximately 1 mm thick heat affected zone (HAZ) in this study although HPS created twice deeper ablation channels with a depth of up to 4 mm. Due to a smaller beam size and a higher output power, HPS maximized tissue ablation rate with minimal thermal effects to the adjacent tissue. Furthermore, more collimated beam characteristics provides more spatial flexibility and may even help to decrease the rate of fiber degradation associated with thermal damage from debris reattachment to the tip.

  3. Percutaneous tumor ablation tools: microwave, radiofrequency, or cryoablation--what should you use and why?

    PubMed

    Hinshaw, J Louis; Lubner, Meghan G; Ziemlewicz, Timothy J; Lee, Fred T; Brace, Christopher L

    2014-01-01

    Image-guided thermal ablation is an evolving and growing treatment option for patients with malignant disease of multiple organ systems. Treatment indications have been expanding to include benign tumors as well. Specifically, the most prevalent indications to date have been in the liver (primary and metastatic disease, as well as benign tumors such as hemangiomas and adenomas), kidney (primarily renal cell carcinoma, but also benign tumors such as angiomyolipomas and oncocytomas), lung (primary and metastatic disease), and soft tissue and/or bone (primarily metastatic disease and osteoid osteomas). Each organ system has different underlying tissue characteristics, which can have profound effects on the resulting thermal changes and ablation zone. Understanding these issues is important for optimizing clinical results. In addition, thermal ablation technology has evolved rapidly during the past several decades, with substantial technical and procedural improvements that can help improve clinical outcomes and safety profiles. Staying up to date on these developments is challenging but critical because the physical properties underlying the different ablation modalities and the appropriate use of adjuncts will have a tremendous effect on treatment results. Ultimately, combining an understanding of the physical properties of the ablation modalities with an understanding of the thermal kinetics in tissue and using the most appropriate ablation modality for each patient are key to optimizing clinical outcomes. Suggested algorithms are described that will help physicians choose among the various ablation modalities for individual patients.

  4. An optimal sliding choke antenna for hepatic microwave ablation.

    PubMed

    Prakash, Punit; Converse, Mark C; Webster, John G; Mahvi, David M

    2009-10-01

    Microwave ablation (MWA) is a minimally invasive technique increasingly used for thermal therapy of liver tumors. Effective MWA requires efficient interstitial antennas that destroy tumors and a margin of healthy tissue, in situ, while minimizing damage to the rest of the organ. Previously, we presented a method for optimizing MWA antenna designs by coupling finite element method models of antennas with a real-coded, multiobjective genetic algorithm. We utilized this procedure to optimize the design of a minimally invasive choke antenna that can be used to create near-spherical ablation zones of adjustable size (radius 1-2 cm) by adjusting treatment durations and a sliding structure of the antenna. Computational results were validated with experiments in ex vivo bovine liver. The optimization procedure yielded antennas with reflection coefficients below -30 dB, which were capable of creating spherical ablation zones up to 2 cm in radius using 100 W input power at 2.45 GHz with treatment durations under 2 min.

  5. Doing without dimensions

    NASA Astrophysics Data System (ADS)

    Spurgin, C. B.

    1986-03-01

    The author discusses the concept of dimensions of a physical quantity, and the relationship between derived units (expressed in terms of their base units) and the dimensions of the derived quantities. He calls for the replacement of 'dimensions' by base units in the GCE A-level syllabus and provides some recommendations to GCE examining boards.

  6. Dimension of chaotic attractors

    SciTech Connect

    Farmer, J.D.; Ott, E.; Yorke, J.A.

    1982-09-01

    Dimension is perhaps the most basic property of an attractor. In this paper we discuss a variety of different definitions of dimension, compute their values for a typical example, and review previous work on the dimension of chaotic attractors. The relevant definitions of dimension are of two general types, those that depend only on metric properties, and those that depend on probabilistic properties (that is, they depend on the frequency with which a typical trajectory visits different regions of the attractor). Both our example and the previous work that we review support the conclusion that all of the probabilistic dimensions take on the same value, which we call the dimension of the natural measure, and all of the metric dimensions take on a common value, which we call the fractal dimension. Furthermore, the dimension of the natural measure is typically equal to the Lyapunov dimension, which is defined in terms of Lyapunov numbers, and thus is usually far easier to calculate than any other definition. Because it is computable and more physically relevant, we feel that the dimension of the natural measure is more important than the fractal dimension.

  7. 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.

  8. Laser ablation studies of concrete

    SciTech Connect

    Savina, M.; Xu, Z.; Wang, Y.; Reed, C.; Pellin, M.

    1999-10-20

    Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. The authors present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied using cement and high density concrete as targets. Ablation efficiency and material removal rates were determined as functions of irradiance and pulse overlap. Doped samples were also ablated to determine the efficiency with which surface contaminants were removed and captured in the effluent. The results show that the cement phase of the material melts and vaporizes, but the aggregate portion (sand and rock) fragments. The effluent consists of both micron-size aerosol particles and chunks of fragmented aggregate material. Laser-induced optical emission spectroscopy was used to analyze the surface during ablation. Analysis of the effluent showed that contaminants such as cesium and strontium were strongly segregated into different regions of the particle size distribution of the aerosol.

  9. Fragmentation and ablation during entry

    SciTech Connect

    Canavan, G.H.

    1997-09-01

    This note discusses objects that both fragment and ablate during entry, using the results of previous reports to describe the velocity, pressure, and fragmentation of entering objects. It shows that the mechanisms used there to describe the breakup of non-ablating objects during deceleration remain valid for most ablating objects. It treats coupled fragmentation and ablation during entry, building on earlier models that separately discuss the entry of objects that are hard, whose high heat of ablation permits little erosion, and those who are strong whose strength prevents fragmentation, which are discussed in ``Radiation from Hard Objects,`` ``Deceleration and Radiation of Strong, Hard, Asteroids During Atmospheric Impact,`` and ``Meteor Signature Interpretation.`` This note provides a more detailed treatment of the further breakup and separation of fragments during descent. It replaces the constraint on mass per unit area used earlier to determine the altitude and magnitude of peak power radiation with a detailed analytic solution of deceleration. Model predictions are shown to be in agreement with the key features of numerical calculations of deceleration. The model equations are solved for the altitudes of maximum radiation, which agree with numerical integrations. The model is inverted analytically to infer object size and speed from measurements of peak power and altitude to provide a complete model for the approximate inversion of meteor data.

  10. Thermal ablation of lung tumors.

    PubMed

    McTaggart, Ryan A; Dupuy, Damian E

    2007-06-01

    Thermal ablation can be applied to treat any thoracic malignancy: primary lung cancers, recurrent primary lung cancers, metastatic disease, chest wall masses, and painful, bony metastases. Since the first reported use of thermal ablation for lung cancer in 2000 there has been an explosive use of the procedure, and by 2010 the number of procedures to treat thoracic malignancy is expected to exceed 150,000 per year. Presently, thermal ablation is best used for patients with early-stage lung cancers in patients who are not surgical candidates, patients with small and favorably located pulmonary metastases, and patients in whom palliation of tumor-related symptoms is the goal. Radiofrequency ablation, microwave ablation, and cryoablation are novel treatment modalities for lung cancer and can safely accomplish tumor destruction and even complete eradication of tumor in patients who are not candidates for surgical resection. In this article, we discuss technical considerations for each modality and the periprocedure and postprocedure management of patients with this disease.

  11. Transrectal Array Configurations Optimized For Prostate HIFU Ablation

    SciTech Connect

    Anand, Ajay; Raju, Balasundar I.; Sethuraman, Shriram; Sokka, Shunmugavelu

    2009-04-14

    The objectives of this study were to evaluate and compare steering and ablation rates from several types of transrectal arrays operated at different frequencies for whole prostate ablation. Three-dimensional acoustic and thermal modeling (Rayleigh-Sommerfield and Penne's BHTE) were performed. Treatment volumes up to 70cc and anterior-posterior distances up to 6 cm were considered. The maximum transducer dimensions were constrained to 5 cm (along rectum) and 2.5 cm (elevation), and the channel count was limited to 256. Planar array configurations for truncated-annular, 1/1.5D, and 2D random arrays were evaluated at 1, 2, and 4 MHz for capability to treat the entire prostate. The acoustic intensity at the surface was fixed at 10 W/cm{sup 2}. The maximum temperature was restricted to 80 deg. C. The volumetric ablation rate was computed to compare the treatment times amongst different configurations. The 1.5D Planar array at 1 MHz ablated the whole prostate in the shortest amount of time while maintaining adequate steering. The higher frequency arrays required smaller elevation apertures for a fixed channel count to maintain a single focal spot at the desired location. Consequently, these arrays resulted in slower heating rates with increased near-field heating. The 1 MHz 1.5D array would also be advantageous compared to single-element transducers since only one mechanical degree of motion is required. This study demonstrates the selection of an optimal array geometry and frequency for transrectal HIFU, resulting in faster ablation rates and reduced treatment times.

  12. Transrectal Array Configurations Optimized For Prostate HIFU Ablation

    NASA Astrophysics Data System (ADS)

    Anand, Ajay; Raju, Balasundar I.; Sethuraman, Shriram; Sokka, Shunmugavelu

    2009-04-01

    The objectives of this study were to evaluate and compare steering and ablation rates from several types of transrectal arrays operated at different frequencies for whole prostate ablation. Three-dimensional acoustic and thermal modeling (Rayleigh-Sommerfield and Penne's BHTE) were performed. Treatment volumes up to 70cc and anterior-posterior distances up to 6 cm were considered. The maximum transducer dimensions were constrained to 5 cm (along rectum) and 2.5 cm (elevation), and the channel count was limited to 256. Planar array configurations for truncated-annular, 1/1.5D, and 2D random arrays were evaluated at 1, 2, and 4 MHz for capability to treat the entire prostate. The acoustic intensity at the surface was fixed at 10 W/cm2. The maximum temperature was restricted to 80° C. The volumetric ablation rate was computed to compare the treatment times amongst different configurations. The 1.5D Planar array at 1 MHz ablated the whole prostate in the shortest amount of time while maintaining adequate steering. The higher frequency arrays required smaller elevation apertures for a fixed channel count to maintain a single focal spot at the desired location. Consequently, these arrays resulted in slower heating rates with increased near-field heating. The 1 MHz 1.5D array would also be advantageous compared to single-element transducers since only one mechanical degree of motion is required. This study demonstrates the selection of an optimal array geometry and frequency for transrectal HIFU, resulting in faster ablation rates and reduced treatment times.

  13. Sequential activation of ground pads reduces skin heating during radiofrequency tumor ablation: in vivo porcine results.

    PubMed

    Schutt, David J; Swindle, M Michael; Helke, Kristi L; Bastarrika, Gorka; Schwarz, Florian; Haemmerich, Dieter

    2010-03-01

    Skin burns below ground pads during monopolar RF ablation are increasingly prevalent, thereby hindering the development of higher power RF generators capable of creating larger tumor ablation zones in combination with multiple or new applicators. Our goal was to evaluate reduction in skin temperatures via additional ground pads in an in vivo porcine model. Three ground pads placed on the animal's abdomen were activated either simultaneously or sequentially, where activation timing was adjusted to equilibrate skin temperature below each pad. Thirteen RF ablations (n = 4 simultaneous at 300 W, n = 5 sequential at 300 W, and n = 4 sequential at 375 W) were performed for 12 min via two internally cooled cluster electrodes placed in the gluteus maximus of domestic swine. Temperature rise at each pad and burn degree as determined via histology were compared. Ablation zone size was determined via T2-weighted MRI. Maximum temperature rise was significantly higher with simultaneous activation than with either of the sequential activation group (21.4 degrees C versus 8.1 degrees C or 9.6 degrees C, p < 0.01). Ablation zone diameters during simultaneous (300 W) and sequential activations (300 and 375 W) were and 6.9 +/- 0.3, 5.6 +/- 0.3, and 7.5 +/- 0.6 cm, respectively. Sequential activation of multiple ground pads results in significantly lower skin temperatures and less severe burns, as measured by histological examination.

  14. Theoretical Modeling for Hepatic Microwave Ablation

    PubMed Central

    Prakash, Punit

    2010-01-01

    Thermal tissue ablation is an interventional procedure increasingly being used for treatment of diverse medical conditions. Microwave ablation is emerging as an attractive modality for thermal therapy of large soft tissue targets in short periods of time, making it particularly suitable for ablation of hepatic and other tumors. Theoretical models of the ablation process are a powerful tool for predicting the temperature profile in tissue and resultant tissue damage created by ablation devices. These models play an important role in the design and optimization of devices for microwave tissue ablation. Furthermore, they are a useful tool for exploring and planning treatment delivery strategies. This review describes the status of theoretical models developed for microwave tissue ablation. It also reviews current challenges, research trends and progress towards development of accurate models for high temperature microwave tissue ablation. PMID:20309393

  15. Image-guided ablation of adrenal lesions.

    PubMed

    Yamakado, Koichiro

    2014-06-01

    Although laparoscopic adrenalectomy has remained the standard of care for the treatment for adrenal tumors, percutaneous image-guided ablation therapy, such as chemical ablation, radiofrequency ablation, cryoablation, and microwave ablation, has been shown to be clinically useful in many nonsurgical candidates. Ablation therapy has been used to treat both functioning adenomas and malignant tumors, including primary adrenal carcinoma and metastasis. For patients with functioning adenomas, biochemical and symptomatic improvement is achieved in 96 to 100% after ablation; for patients with malignant adrenal neoplasms, however, the survival benefit from ablation therapy remains unclear, though good initial results have been reported. This article outlines the current role of ablation therapy for adrenal lesions, as well as identifying some of the technical considerations for this procedure.

  16. Microwave ablation at 915 MHz vs 2.45 GHz: A theoretical and experimental investigation

    SciTech Connect

    Curto, Sergio; Taj-Eldin, Mohammed; Fairchild, Dillon; Prakash, Punit

    2015-11-15

    Purpose: The relationship between microwave ablation system operating frequency and ablation performance is not currently well understood. The objective of this study was to comparatively assess the differences in microwave ablation at 915 MHz and 2.45 GHz. Methods: Analytical expressions for electromagnetic radiation from point sources were used to compare power deposition at the two frequencies of interest. A 3D electromagnetic-thermal bioheat transfer solver was implemented with the finite element method to characterize power deposition and thermal ablation with asymmetrical insulated dipole antennas (single-antenna and dual-antenna synchronous arrays). Simulation results were validated against experiments in ex vivo tissue. Results: Theoretical, computational, and experimental results indicated greater power deposition and larger diameter ablation zones when using a single insulated microwave antenna at 2.45 GHz; experimentally, 32 ± 4.1 mm and 36.3 ± 1.0 mm for 5 and 10 min, respectively, at 2.45 GHz, compared to 24 ± 1.7 mm and 29.5 ± 0.6 mm at 915 MHz, with 30 W forward power at the antenna input port. In experiments, faster heating was observed at locations 5 mm (0.91 vs 0.49 °C/s) and 10 mm (0.28 vs 0.15 °C/s) from the antenna operating at 2.45 GHz. Larger ablation zones were observed with dual-antenna arrays at 2.45 GHz; however, the differences were less pronounced than for single antennas. Conclusions: Single- and dual-antenna arrays systems operating at 2.45 GHz yield larger ablation zone due to greater power deposition in proximity to the antenna, as well as greater role of thermal conduction.

  17. Hepatic ablation with multiple interstitial ultrasound applicators: initial ex vivo and computational studies

    NASA Astrophysics Data System (ADS)

    Prakash, Punit; Salgaonkar, Vasant A.; Burdette, E. Clif; Diederich, Chris J.

    2011-03-01

    Radiofrequency (RF) ablation has emerged as an effective method for treating liver tumors under 3 cm in diameter. Multiple applicator devices and techniques - using RF, microwave and other modalities - are under development for thermal ablation of large and irregularly-shaped liver tumors. Interstitial ultrasound (IUS) applicators, comprised of linear arrays of independently powered tubular transducers, enable 3D control of the spatial power deposition profile and simultaneous ablation with multiple applicators. We evaluated IUS applicator configurations (parallel, converging and diverging implants) suitable for percutaneous and laparascopic placement with experiments in ex vivo bovine tissue and computational models. Ex vivo ablation zones measured 4.6+/-0.5 x 4.2+/-0.5 × 3.3+/-0.5 cm3 and 5.6+/-0.5 × 4.9+/-0.5 x 2.8+/-0.3 cm3 using three parallel applicators spaced 2 and 3 cm apart, respectively, and 4.0+/-0.3 × 3.2+/-0.4 × 2.9+/-0.2 cm3 using two parallel applicators spaced 2 cm apart. Computational models indicate in vivo ablation zones up to 4.5 × 4.4 × 5.5 cm3 and 5.7 × 4.8 × 5.2 cm3, using three applicators spaced 2 and 3 cm apart, respectively. Converging and diverging implant patterns can also be employed for conformal ablation of irregularly-shaped tumor margins by tailoring power levels along each device. Simultaneously powered interstitial ultrasound devices can create tailored ablation zones comparable to currently available RF devices and similarly sized microwave antennas.

  18. 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

  19. An MRI guided system for prostate laser ablation with treatment planning and multi-planar temperature monitoring

    NASA Astrophysics Data System (ADS)

    Xu, Sheng; Agarwal, Harsh; Bernardo, Marcelino; Seifabadi, Reza; Turkbey, Baris; Partanen, Ari; Negussie, Ayele; Glossop, Neil; Choyke, Peter; Pinto, Peter; Wood, Bradford J.

    2016-03-01

    Prostate cancer is often over treated with standard treatment options which impact the patients' quality of life. Laser ablation has emerged as a new approach to treat prostate cancer while sparing the healthy tissue around the tumor. Since laser ablation has a small treatment zone with high temperature, it is necessary to use accurate image guidance and treatment planning to enable full ablation of the tumor. Intraoperative temperature monitoring is also desirable to protect critical structures from being damaged in laser ablation. In response to these problems, we developed a navigation platform and integrated it with a clinical MRI scanner and a side firing laser ablation device. The system allows imaging, image guidance, treatment planning and temperature monitoring to be carried out on the same platform. Temperature sensing phantoms were developed to demonstrate the concept of iterative treatment planning and intraoperative temperature monitoring. Retrospective patient studies were also conducted to show the clinical feasibility of the system.

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

    PubMed Central

    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. PMID:28382173

  1. 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.

  2. 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.

  3. Transhemangioma Ablation of Hepatocellular Carcinoma

    SciTech Connect

    Pua, Uei

    2012-12-15

    Radiofrequency ablation (RFA) is a well-established treatment modality in the treatment of early hepatocellular carcinoma (HCC) [1]. Safe trajectory of the RFA probe is crucial in decreasing collateral tissue damage and unwarranted probe transgression. As a percutaneous technique, however, the trajectory of the needle is sometimes constrained by the available imaging plane. The presence of a hemangioma beside an HCC is uncommon but poses the question of safety related to probe transgression. We hereby describe a case of transhemangioma ablation of a dome HCC.

  4. Damage in materials following ablation by ultrashort laser pulses: A molecular-dynamics study

    SciTech Connect

    Bouilly, Delphine; Perez, Danny; Lewis, Laurent J.

    2007-11-01

    The formation of craters following femtosecond- and picosecond-pulse laser ablation in the thermal regime is studied using a generic two-dimensional numerical model based on molecular-dynamics simulations and the Lennard-Jones potential. Femtosecond pulses are found to produce very clean craters through a combination of etching of the walls and the formation of a very thin heat affected zone. Our simulations also indicate that dislocations are emitted continuously during all of the ablation process (i.e., for hundreds of ps). For picosecond pulses, we observe much thicker heat affected zones which result from melting and recrystallization following the absorption of the light. In this case also, continuous emission of dislocations--though fewer in number--takes place throughout the ablation process.

  5. Airborne Hyperspectral Imaging of Supraglacial Lakes in Greenland's Ablation Zone

    NASA Astrophysics Data System (ADS)

    Adler, J.; Behar, A. E.; Jacobson, N. T.

    2010-12-01

    In 2010 an airborne instrument was assembled to image supraglacial lakes near the Jakobshavn Isbrae of the Greenland Ice Sheet. The instrument was designed to fly on a helicopter, and consists of a hyperspectral imager, a GPS/inertial measurement unit (GPS/IMU), and a data-logging computer. A series of narrow visible optical channels ~13nm wide, such as found in a hyperspectral imager, are theorized to be useful in determining the depths of supraglacial lakes using techniques based on the Beer-Lambert-Bouguer Law. During June, several supraglacial lakes were selected for study each day, based upon MODIS imagery taken during the previous week. Flying over a given lake, several track lines were flown to image both shallow and deep sections of the lake, imaging the full range of depth for future algorithm development. The telescoping instrument mount was constructed to allow the sensor package to be deployed from a helicopter in-flight, with an unobstructed downward-facing field of view. The GPS/IMU records the pointing orientation, altitude, and geographical coordinates of the imager to the data-logger, in order to allow post-flight geo-referencing of the raw hyperspectral imagery. With this geo-referenced spectrum data, a depth map for a given lake can be calculated through reference to a water absorptivity model. This risk-reduction expedition to fly a helicopter-borne hyperspectral imager over the supraglacial lakes of Greenland was a success. The instrument mount for the imager worked as designed, and no vibration issues were encountered. As a result, we have confidence in the instrument platform's performance during future surveys of Greenland's supraglacial lakes. The hyperspectral imager, data acquisition computer, and geo-referencing services are provided by Resonon, Inc. of Bozeman, MT, and the GPS/IMU is manufactured by Cloudcap Technology of Hood River, OR.

  6. Lung Tumor Radiofrequency Ablation: Where Do We Stand?

    SciTech Connect

    Baere, Thierry de

    2011-04-15

    Today, radiofrequency ablation (RFA) of primary and metastatic lung tumor is increasingly used. Because RFA is most often used with curative intent, preablation workup must be a preoperative workup. General anesthesia provides higher feasibility than conscious sedation. The electrode positioning must be performed under computed tomography for sake of accuracy. The delivery of RFA must be adapted to tumor location, with different impedances used when treating tumors with or without pleural contact. The estimated rate of incomplete local treatment at 18 months was 7% (95% confidence interval, 3-14) per tumor, with incomplete treatment depicted at 4 months (n = 1), 6 months (n = 2), 9 months (n = 2), and 12 months (n = 2). Overall survival and lung disease-free survival at 18 months were, respectively, 71 and 34%. Size is a key point for tumor selection because large size is predictive of incomplete local treatment and poor survival. The ratio of ablation volume relative to tumor volume is predictive of complete ablation. Follow-up computed tomography that relies on the size of the ablation zone demonstrates the presence of incomplete ablation. Positron emission tomography might be an interesting option. Chest tube placement for pneumothorax is reported in 8 to 12%. Alveolar hemorrhage and postprocedure hemoptysis occurred in approximately 10% of procedures and rarely required specific treatment. Death was mostly related to single-lung patients and hilar tumors. No modification of forced expiratory volume in the first second between pre- and post-RFA at 2 months was found. RFA in the lung provides a high local efficacy rate. The use of RFA as a palliative tool in combination with chemotherapy remains to be explored.

  7. Fractional ablative laser skin resurfacing: a review.

    PubMed

    Tajirian, Ani L; Tarijian, Ani L; Goldberg, David J

    2011-12-01

    Ablative laser technology has been in use for many years now. The large side effect profile however has limited its use. Fractional ablative technology is a newer development which combines a lesser side effect profile along with similar efficacy. In this paper we review fractional ablative laser skin resurfacing.

  8. 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.

  9. 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.

  10. Investigation of interstitial ultrasound ablation of spinal and paraspinal tumors: A patient-specific and parametric simulation study

    NASA Astrophysics Data System (ADS)

    Scott, Serena J.; Salgaonkar, Vasant; Prakash, Punit; Burdette, E. Clif; Diederich, Chris J.

    2017-03-01

    Preferential acoustic absorption and heating of bone can significantly impact interstitial ultrasound ablation of tumors within or bordering the spine. Furthermore, intervening cortical bone may provide acoustic and thermal insulation that can protect sensitive structures nearby, such as the spinal cord. The objectives of this study are firstly, to apply parametric and patient-specific models to theoretically assess the feasibility of interstitial ultrasound ablation of tumors within and near the spine, and secondly, to identify potential energy delivery strategies, safety criteria, advantages, and disadvantages of interstitial ultrasound in this setting. Transient biothermal models using previously validated approximations for power deposition within bone from interstitial sources were employed. Multilayered axisymmetric models were used to perform a parametric assessment of the impact of tumor dimensions, attenuation (dependent on residual bone content), perfusion, and maximum temperature thresholds on necessary treatment parameters and on treatment effectiveness. 3D patient-specific finite element models were generated based on segmented CT scans for nine representative patient cases selected to bracket a range of clinical interest, with tumors in or near the vertebrae, sacrum, and ilium. Tumors were 10-27 mm in diameter, 10-43 mm long, and 0-14 mm from the spinal canal. Paraspinal tumors, osteolytic vertebral tumors, and a mixed osteolytic/osteoblastic iliac bone tumor were considered. 7 MHz (1.5 mm OD) and 3.0 MHz (3.2 mm OD) applicators with an array of 1-4 tubular transducers (0.5 -1.5 cm long, 150-360° sector angles), were applied in various implant configurations. Variable thicknesses of bone insulating critical anatomy from the tumor and insulation of the spinal cord with injected carbon dioxide were also investigated for definition of safety margins and possible protection of critical structures. 6-44 mm diameter osteolytic tumors surrounded by bone and

  11. Esophageal papilloma: Flexible endoscopic ablation by radiofrequency

    PubMed Central

    del Genio, Gianmattia; del Genio, Federica; Schettino, Pietro; Limongelli, Paolo; Tolone, Salvatore; Brusciano, Luigi; Avellino, Manuela; Vitiello, Chiara; Docimo, Giovanni; Pezzullo, Angelo; Docimo, Ludovico

    2015-01-01

    Squamous papilloma of the esophagus is a rare benign lesion of the esophagus. Radiofrequency ablation is an established endoscopic technique for the eradication of Barrett esophagus. No cases of endoscopic ablation of esophageal papilloma by radiofrequency ablation (RFA) have been reported. We report a case of esophageal papilloma successfully treated with a single session of radiofrequency ablation. Endoscopic ablation of the lesion was achieved by radiofrequency using a new catheter inserted through the working channel of endoscope. The esophageal ablated tissue was removed by a specifically designed cup. Complete ablation was confirmed at 3 mo by endoscopy with biopsies. This case supports feasibility and safety of as a new potential indication for BarrxTM RFA in patients with esophageal papilloma. PMID:25789102

  12. Percutaneous ablation of benign bone tumors.

    PubMed

    Welch, Brian T; Welch, Timothy J

    2011-09-01

    Percutaneous image-guided ablation has become a standard of practice and one of the primary modalities for treatment of benign bone tumors. Ablation is most commonly used to treat osteoid osteomas but may also be used in the treatment of chondroblastomas, osteoblastomas, and giant cell tumors. Percutaneous image-guided ablation of benign bone tumors carries a high success rate (>90% in case series) and results in decreased morbidity, mortality, and expense compared with traditional surgical methods. The ablation technique most often applied to benign bone lesions is radiofrequency ablation. Because the ablation technique has been extensively applied to osteoid osteomas and because of the uncommon nature of other benign bone tumors, we will primarily focus this discussion on the percutaneous ablation of osteoid osteomas.

  13. Synergistic Combination of Electrolysis and Electroporation for Tissue Ablation

    PubMed Central

    Mikus, Paul; Klein, Nina; Rubinsky, Liel; Rubinsky, Boris

    2016-01-01

    Electrolysis, electrochemotherapy with reversible electroporation, nanosecond pulsed electric fields and irreversible electroporation are valuable non-thermal electricity based tissue ablation technologies. This paper reports results from the first large animal study of a new non-thermal tissue ablation technology that employs “Synergistic electrolysis and electroporation” (SEE). The goal of this pre-clinical study is to expand on earlier studies with small animals and use the pig liver to establish SEE treatment parameters of clinical utility. We examined two SEE methods. One of the methods employs multiple electrochemotherapy-type reversible electroporation magnitude pulses, designed in such a way that the charge delivered during the electroporation pulses generates the electrolytic products. The second SEE method combines the delivery of a small number of electrochemotherapy magnitude electroporation pulses with a low voltage electrolysis generating DC current in three different ways. We show that both methods can produce lesion with dimensions of clinical utility, without the need to inject drugs as in electrochemotherapy, faster than with conventional electrolysis and with lower electric fields than irreversible electroporation and nanosecond pulsed ablation. PMID:26866693

  14. Synergistic Combination of Electrolysis and Electroporation for Tissue Ablation.

    PubMed

    Stehling, Michael K; Guenther, Enric; Mikus, Paul; Klein, Nina; Rubinsky, Liel; Rubinsky, Boris

    2016-01-01

    Electrolysis, electrochemotherapy with reversible electroporation, nanosecond pulsed electric fields and irreversible electroporation are valuable non-thermal electricity based tissue ablation technologies. This paper reports results from the first large animal study of a new non-thermal tissue ablation technology that employs "Synergistic electrolysis and electroporation" (SEE). The goal of this pre-clinical study is to expand on earlier studies with small animals and use the pig liver to establish SEE treatment parameters of clinical utility. We examined two SEE methods. One of the methods employs multiple electrochemotherapy-type reversible electroporation magnitude pulses, designed in such a way that the charge delivered during the electroporation pulses generates the electrolytic products. The second SEE method combines the delivery of a small number of electrochemotherapy magnitude electroporation pulses with a low voltage electrolysis generating DC current in three different ways. We show that both methods can produce lesion with dimensions of clinical utility, without the need to inject drugs as in electrochemotherapy, faster than with conventional electrolysis and with lower electric fields than irreversible electroporation and nanosecond pulsed ablation.

  15. Planar laser-driven ablation model for nonlocalized absorption

    SciTech Connect

    Dahmani, F.; Kerdja, T. )

    1991-05-01

    A model for planar laser-driven ablation is presented. Nonlocalized inverse bremsstrahlung absorption of laser energy at a density {ital n}{sub 1}{lt}{ital n}{sub {ital c}} is assumed. A steady-state solution in the conduction zone is joined to a rarefaction wave in the underdense plasma. The calculations relate all steady-state fluid quantities to only the material, absorbed intensity, and laser wavelength. The theory agrees well with results from a computer hydrodynamics code MEDUSA (Comput. Phys. Commun. {bold 7}, 271 (1974)) and experiments.

  16. Dimensions of Educational Need.

    ERIC Educational Resources Information Center

    Johns, Roe L., Ed.; And Others

    Roe L. Johns and J. Alan Thomas survey the problem of educational need; and Kern Alexander considers the implications of the dimensions of educational need for school financing. Dimensions of need in the following areas are defined: early childhood and basic elementary and secondary education, by William P. McLure; educational programs for…

  17. The Qualitative Dimension.

    ERIC Educational Resources Information Center

    Lodge-Peters, Dianne S.

    The qualitative dimension of educational research methodology is explored, and the literature of qualitative methodology is reviewed so researchers may (1) understand more fully the qualitative dimension as it, in turn, fits within the parameters of educational research as a whole, and (2) have more informed access to the sometimes daunting array…

  18. Navigating between the Dimensions

    ERIC Educational Resources Information Center

    Fleron, Julian F.; Ecke, Volker

    2011-01-01

    Generations have been inspired by Edwin A. Abbott's profound tour of the dimensions in his novella "Flatland: A Romance of Many Dimensions" (1884). This well-known satire is the story of a flat land inhabited by geometric shapes trying to navigate the subtleties of their geometric, social, and political positions. In this article, the authors…

  19. Reconfigurable tapered coaxial slot antenna for hepatic microwave ablation.

    PubMed

    Malhotra, Neeru; Marwaha, Anupma; Kumar, Ajay

    2016-01-01

    Microwave ablation is rapidly being rediscovered and developed for treating many cancers of liver, lung, kidney and bone, as well as arrhythmias and other medical conditions. The microwaves ablate tissue by heating it to cytotoxic temperatures. The microwave antenna design suffers the challenges of effective coupling and penetration into body tissues, uncontrolled power deposition due to applicator construction limitations affecting uniform heating of target region, and narrowband operation leading to mismatch for many patients and detrimental heating. To meet out the requirements of wideband operation and localized lesion reconfigurable linearly tapered slot interstitial wideband antenna has been proposed for working in the 1.38 GHz to 4.31 GHz frequency band. The performance of the antenna is evaluated by using FEM-based HFSS software. The slot height and taper height are reconfigured for parametric analysis achieving maximum impedance matching and spherical ablation zone without requiring any additional adjustable structures. The tapering of the slot in coaxial antenna generates current distribution at the edges of the slot for maximizing specific absorption rate.

  20. Characterization of tracked radiofrequency ablation in phantom

    SciTech Connect

    Chen, Chun-Cheng R.; Miga, Michael I.; Galloway, Robert L.

    2007-10-15

    In radiofrequency ablation (RFA), successful therapy requires accurate, image-guided placement of the ablation device in a location selected by a predictive treatment plan. Current planning methods rely on geometric models of ablations that are not sensitive to underlying physical processes in RFA. Implementing plans based on computational models of RFA with image-guided techniques, however, has not been well characterized. To study the use of computational models of RFA in planning needle placement, this work compared ablations performed with an optically tracked RFA device with corresponding models of the ablations. The calibration of the tracked device allowed the positions of distal features of the device, particularly the tips of the needle electrodes, to be determined to within 1.4{+-}0.6 mm of uncertainty. Ablations were then performed using the tracked device in a phantom system based on an agarose-albumin mixture. Images of the sliced phantom obtained from the ablation experiments were then compared with the predictions of a bioheat transfer model of RFA, which used the positional data of the tracked device obtained during ablation. The model was demonstrated to predict 90% of imaged pixels classified as being ablated. The discrepancies between model predictions and observations were analyzed and attributed to needle tracking inaccuracy as well as to uncertainties in model parameters. The results suggest the feasibility of using finite element modeling to plan ablations with predictable outcomes when implemented using tracked RFA.

  1. Dual-energy CT after radiofrequency ablation of liver, kidney, and lung lesions: a review of features.

    PubMed

    Vandenbroucke, Frederik; Van Hedent, Steven; Van Gompel, Gert; Buls, Nico; Craggs, Gordon; Vandemeulebroucke, Jef; Ros, Pablo R; de Mey, Johan

    2015-06-01

    Early detection of residual tumour and local tumour progression (LTP) after radiofrequency (RF) ablation is crucial in the decision whether or not to re-ablate. In general, standard contrast-enhanced computed tomography (CT) is used to evaluate the technique effectiveness; however, it is difficult to differentiate post-treatment changes from residual tumour. Dual-energy CT (DECT) is a relatively new technique that enables more specific tissue characterisation of iodine-enhanced structures because of the isolation of iodine in the imaging data. Necrotic post-ablation zones can be depicted as avascular regions by DECT on greyscale- and colour-coded iodine images. Synthesised monochromatic images from dual-energy CT with spectral analysis can be used to select the optimal keV to achieve the highest contrast-to-noise ratio between tissues. This facilitates outlining the interface between the ablation zone and surrounding tissue. Post-processing of DECT data can lead to an improved characterisation and delineation of benign post-ablation changes from LTP. Radiologists need to be familiar with typical post-ablation image interpretations when using DECT techniques. Here, we review the spectrum of changes after RF ablation of liver, kidney, and lung lesions using single-source DECT imaging, with the emphasis on the additional information obtained and pitfalls encountered with this relatively new technique. Teaching Points •Technical success of RF ablation means complete destruction of the tumour. •Assessment of residual tumour on contrast-enhanced CT is hindered by post-ablative changes. •DECT improves material differentiation and may improve focal lesion characterisation. •Iodine maps delineate the treated area from the surrounding parenchyma well.

  2. Priority Education Zones in Mauritius

    ERIC Educational Resources Information Center

    Kumar, Mahadeo Santosh; Gurrib, Mahomed Aniff

    2008-01-01

    This article discusses the Priority Education Zones project (ZEP) in Mauritius. The original and innovative dimensions of the project are described, together with the difficulties encountered during the setting-up of the ZEP schools. The article covers five main issues: the status of the ZEP project; the minimal conditions for success; the…

  3. Optimization of Direct Current-Enhanced Radiofrequency Ablation: An Ex Vivo Study

    SciTech Connect

    Tanaka, Toshihiro Isfort, Peter; Bruners, Philipp; Penzkofer, Tobias; Kichikawa, Kimihiko; Schmitz-Rode, Thomas; Mahnken, Andreas H.

    2010-10-15

    The purpose of this study was to investigate the optimal setting for radiofrequency (RF) ablation combined with direct electrical current (DC) ablation in ex vivo bovine liver. An electrical circuit combining a commercially available RF ablation system with DC was developed. The negative electrode of a rectifier that provides DC was connected to a 3-cm multitined expandable RF probe. A 100-mH inductor was used to prevent electrical leakage from the RF generator. DC was applied for 15 min and followed by RF ablation in freshly excised bovine livers. Electric current was measured by an ammeter. Coagulation volume, ablation duration, and mean amperage were assessed for various DC voltages (no DC, 2.2, 4.5, and 9.0 V) and different RF ablation protocols (stepwise increase from 40 to 80 W, 40 W fixed, and 80 W fixed). Results were compared using Kruskal-Wallis and Mann-Whitney U test. Applying DC with 4.5 or 9.0 V, in combination with 40 W fixed or a stepwise increase of RF energy, resulted in significantly increased zone of ablation size compared with 2.2 V or no DC (P = 0.009). At 4.5 V DC, the stepwise increase of RF energy resulted in the same necrosis size as a 40 W fixed protocol (26.6 {+-} 3.9 vs. 26.5 {+-} 4.0 ml), but ablation duration was significantly decreased (296 {+-} 85 s vs. 423 {+-} 104 s; P = 0.028). Mean amperage was significantly lower at 4.5 V compared with 9.0 V (P = 0.028). Combining a stepwise increase of RF energy with a DC voltage of 4.5 V is most appropriate to increase coagulation volume and to minimize procedure time.

  4. Artificial meteor ablation studies: Olivine

    NASA Technical Reports Server (NTRS)

    Blanchard, M. B.; Cunningham, G. G.

    1973-01-01

    Artificial meteor ablation was performed on a Mg-rich olivine sample using an arc-heated plasma of ionized air. Experimental conditions simulated a meteor traveling about 12 km/sec at an altitude of 70 km. The mineral content of the original olivine sample was 98% olivine (including traces of olivine alteration products) and 2% chromite. Forsterite content of the original olivine was Fo-89. After ablation, the forsterite content had increased to Fo-94 in the recrystallized olivine. In addition, lamella-like intergrowths of magnetite were prevalent constituents. Wherever magnetite occurred, there was an increase in Mg and a corresponding decrease in Fe for the recrystallized olivine. The Allende fusion crust consisted of a recrystallized olivine, which was more Mg-rich and Fe-deficient than the original meteorite's olivine, and abundant magnetite grains. Although troilite and pentlandite were the common opaque mineral constituents in this meteorite, magnetite was the principal opaque mineral found in the fusion crust.

  5. Laser Ablation for Medical Applications

    NASA Astrophysics Data System (ADS)

    Hayashi, Ken-Ichi

    Medical applications of laser are measurement, laser surgery, in-situ monitoring, and processing of medical devices. In this paper, author briefly reviews the trends of medical applications, describes some new applications, and then discuss about the future trends and problems of medical applications. At present, the domestic market of laser equipment for medical applications is nearly 1/10 of that for industrial applications, which has registered significant growth continuously. Laser surgery as a minimum invasive surgery under arthroscope is expected to decrease the pain of patients. Precise processing such as cutting and welding is suitable for manufacturing medical devices. Pulsed laser deposition has been successfully applied to the thin film coating. The corneal refractive surgery by ArF excimer laser has been widely accepted for its highly safe operation. Laser ablation for retinal implant in the visual prosthesis is one of the promising applications of laser ablation in medicine. New applications with femtosecond laser are expected in the near future.

  6. Percutaneous ablation of pancreatic cancer

    PubMed Central

    D’Onofrio, Mirko; Ciaravino, Valentina; De Robertis, Riccardo; Barbi, Emilio; Salvia, Roberto; Girelli, Roberto; Paiella, Salvatore; Gasparini, Camilla; Cardobi, Nicolò; Bassi, Claudio

    2016-01-01

    Pancreatic ductal adenocarcinoma is a highly aggressive tumor with an overall 5-year survival rate of less than 5%. Prognosis and treatment depend on whether the tumor is resectable or not, which mostly depends on how quickly the diagnosis is made. Chemotherapy and radiotherapy can be both used in cases of non-resectable pancreatic cancer. In cases of pancreatic neoplasm that is locally advanced, non-resectable, but non-metastatic, it is possible to apply percutaneous treatments that are able to induce tumor cytoreduction. The aim of this article will be to describe the multiple currently available treatment techniques (radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation), their results, and their possible complications, with the aid of a literature review. PMID:27956791

  7. Laser Ablation Molecular Isotopic Spectrometry

    NASA Astrophysics Data System (ADS)

    Russo, Richard E.; Bol'shakov, Alexander A.; Mao, Xianglei; McKay, Christopher P.; Perry, Dale L.; Sorkhabi, Osman

    2011-02-01

    A new method of performing optical isotopic analysis of condensed samples in ambient air and at ambient pressure has been developed: Laser Ablation Molecular Isotopic Spectrometry (LAMIS). The technique uses radiative transitions from molecular species either directly vaporized from a sample or formed by associative mechanisms of atoms or ions in a laser ablation plume. This method is an advanced modification of a known atomic emission technique called laser-induced breakdown spectroscopy (LIBS). The new method — LAMIS — can determine not only chemical composition but also isotopic ratios of elements in the sample. Isotopic measurements are enabled by significantly larger isotopic shifts found in molecular spectra relative to atomic spectra. Analysis can be performed from a distance and in real time. No sample preparation or pre-treatment is required. Detection of the isotopes of hydrogen, boron, carbon, and oxygen are discussed to illustrate the technique.

  8. Percutaneous ablation of pancreatic cancer.

    PubMed

    D'Onofrio, Mirko; Ciaravino, Valentina; De Robertis, Riccardo; Barbi, Emilio; Salvia, Roberto; Girelli, Roberto; Paiella, Salvatore; Gasparini, Camilla; Cardobi, Nicolò; Bassi, Claudio

    2016-11-28

    Pancreatic ductal adenocarcinoma is a highly aggressive tumor with an overall 5-year survival rate of less than 5%. Prognosis and treatment depend on whether the tumor is resectable or not, which mostly depends on how quickly the diagnosis is made. Chemotherapy and radiotherapy can be both used in cases of non-resectable pancreatic cancer. In cases of pancreatic neoplasm that is locally advanced, non-resectable, but non-metastatic, it is possible to apply percutaneous treatments that are able to induce tumor cytoreduction. The aim of this article will be to describe the multiple currently available treatment techniques (radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation), their results, and their possible complications, with the aid of a literature review.

  9. Observation, Simulation, and Evaluation of Snow Dynamics in the Transitional Snow Zone

    NASA Astrophysics Data System (ADS)

    Wayand, Nicholas E.

    The frequent mid-winter accumulation and ablation cycles of snowpack within the rain-snow transitional zone play an important role for the maritime basins along the western U.S. mountain ranges. Representation of transitional snowpack within hydrological models has remained a challenge, largely because surface and meteorological conditions frequently remain near the freezing point, which allows large errors in modeled accumulation or ablation to result from small forcing or structural errors. This research aims to improve model representation of accumulation and ablation processes by utilizing new observations within the transitional snow zone combined with novel methods of model evaluation. (Abstract shortened by ProQuest.).

  10. Nanometer-scale ablation using focused, coherent extreme ultraviolet/soft x-ray light

    SciTech Connect

    Menoni, Carmen S; Rocca, Jorge J; Vaschenko, Georgiy; Bloom, Scott; Anderson, Erik H; Chao, Weilun; Hemberg, Oscar

    2011-04-26

    Ablation of holes having diameters as small as 82 nm and having clean walls was obtained in a poly(methyl methacrylate) on a silicon substrate by focusing pulses from a Ne-like Ar, 46.9 nm wavelength, capillary-discharge laser using a freestanding Fresnel zone plate diffracting into third order is described. Spectroscopic analysis of light from the ablation has also been performed. These results demonstrate the use of focused coherent EUV/SXR light for the direct nanoscale patterning of materials.

  11. Three-dimensional single-mode nonlinear ablative Rayleigh-Taylor instability

    SciTech Connect

    Yan, R.; Aluie, H.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.

    2016-02-15

    The nonlinear evolution of the single-mode ablative Rayleigh-Taylor instability is studied in three dimensions. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the three-dimensional (3D) terminal bubble velocity greatly exceeds both the two-dimensional (2D) value and the classical 3D bubble velocity. Unlike in 2D, the 3D short-wavelength bubble velocity does not saturate. The growing 3D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes to the ablated plasma filling the bubble volume.

  12. Three-dimensional single-mode nonlinear ablative Rayleigh-Taylor instability

    SciTech Connect

    Yan, R.; Betti, R.; Sanz, J.; Aluie, H.; Liu, B.; Frank, A.

    2016-02-02

    The nonlinear evolution of the single-mode ablative Rayleigh-Taylor instability is studied in three dimensions. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the three-dimensional (3D) terminal bubble velocity greatly exceeds both the two-dimensional (2D) value and the classical 3D bubble velocity. Unlike in 2D, the 3D short-wavelength bubble velocity does not saturate. The growing 3D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. As a result, the vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes to the ablated plasma filling the bubble volume.

  13. The TriBeam system: Femtosecond laser ablation in situ SEM

    SciTech Connect

    Echlin, McLean P.; Straw, Marcus; Randolph, Steven; Filevich, Jorge; Pollock, Tresa M.

    2015-02-15

    Femtosecond laser ablation offers the unique ability to remove material at rates that are orders of magnitude faster than existing ion beam technologies with little or no associated damage. By combining ultrafast lasers with state-of-the-art electron microscopy equipment, we have developed a TriBeam system capable of targeted, in-situ tomography providing chemical, structural, and topographical information in three dimensions of near mm{sup 3} sized volumes. The origins, development, physics, current uses, and future potential for the TriBeam system are described in this tutorial review. - Graphical abstract: Display Omitted - Highlights: • An emerging tool, the TriBeam, for in situ femtosecond (fs) laser ablation is presented. • Fs laser ablation aided tomography at the mm{sup 3}-scale is demonstrated. • Fs laser induced deposition of Pt is demonstrated at sub-diffraction limit resolution. • Fs laser surface structuring is reviewed as well as micromachining applications.

  14. The dimensions of indexing.

    PubMed

    Wilbur, W John; Kim, Won

    2003-01-01

    Indexing of documents is an important strategy intended to make the literature more readily available to the user. Here we describe several dimensions of indexing that are important if indexing is to be optimal. These dimensions are coverage, predictability, and transparency. MeSH terms and text words are compared in MEDLINE in regard to these dimensions. Part of our analysis consists in applying AdaBoost with decisions trees as the weak learners to estimate how reliably index terms are being assigned and how complex the criteria are by which they are being assigned. Our conclusions are that MeSH terms are more predictable and more transparent than text words.

  15. Microwave Ablation Compared to Radiofrequency Ablation for Hepatic Lesions: A Meta-Analysis.

    PubMed

    Huo, Ya Ruth; Eslick, Guy D

    2015-08-01

    To evaluate the efficacy and safety of microwave (MW) ablation compared with radiofrequency (RF) ablation for hepatic lesions by using meta-analytic techniques. Overall, 16 studies involving 2,062 patients were included. MW ablation was found to have significantly better 6-year overall survival than RF ablation (odds ratio, 1.64, 95% confidence interval, 1.15-2.35), but this was based on a few articles (n = 3 of 16). MW ablation and RF ablation had similar 1-5-year overall survival, disease-free survival, local recurrence rate, and adverse events. Based on similar safety and efficacy outcomes, either MW ablation or RF ablation may be used for effective local hepatic therapy.

  16. Tumor Thermal Ablation Enhancement by Micromaterials.

    PubMed

    Zhao, Fan; Su, Hongying; Han, Xiangjun; Bao, Han; Qi, Ji

    2016-01-07

    Thermal ablation is a minimally invasive therapeutic technique that has shown remarkable potential in treating un resectable tumors. However, clinical applications have stalled, due to safety ambiguities, slow heat induction, lengthy ablation times, and post-therapeutic monitoring issues. To further improve treatment efficacy, an assortment of micro materials (eg, nano particulates of gold, silica, or iron oxide and single-walled carbon nanotubes) are under study as thermal ablative adjuncts.In recent years, the micro material domain has become especially interesting.In vivo and in vitro animal studies have validated the use of microspheres as embolic agents in liver tumors, in advance of radiofrequency ablation. Microcapsules and micro bubbles serving as ultrasound contrast and ablation sensibilizers are strong prospects for clinical applications. This review was conducted to explore benefits of the three aforementioned micro scale technologies, in conjunction with tumor thermal ablation.

  17. Percutaneous thermal ablation of primary lung cancer.

    PubMed

    de Baere, T; Tselikas, L; Catena, V; Buy, X; Deschamps, F; Palussière, J

    2016-10-01

    Percutaneous ablation of small-size non-small-cell lung cancer (NSCLC) has demonstrated feasibility and safety in nonsurgical candidates. Radiofrequency ablation (RFA), the most commonly used technique, has an 80-90% reported rate of complete ablation, with the best results obtained in tumors less than 2-3cm in diameter. The highest one-, three-, and five-year overall survival rates reported in NSCLC following RFA are 97.7%, 72.9%, and 55.7% respectively. Tumor size, tumor stage, and underlying comorbidities are the main predictors of survival. Other ablation techniques such as microwave or cryoablation may help overcome the limitations of RFA in the future, particularly for large tumors or those close to large vessels. Stereotactic ablative radiotherapy (SABR) has its own complications and carries the risk of fiducial placement requiring multiple lung punctures. SABR has also demonstrated significant efficacy in treating small-size lung tumors and should be compared to percutaneous ablation.

  18. Image-guided ablation for hepatocellular carcinoma.

    PubMed

    Lencioni, Riccardo; Crocetti, Laura

    2013-01-01

    Image-guided ablation is accepted as the best therapeutic choice for patients with early-stage hepatocellular carcinoma (HCC) when surgical options-including resection and transplantation-are precluded. The term image-guided tumor ablation is defined as the direct application of chemical substances or sources of energy to a focal tumor in an attempt to achieve eradication or substantial tumor destruction. Over the past 25 years, several methods for local tumor destruction have been developed and clinically tested. Radiofrequency ablation (RFA) has shown superior anticancer effect and greater survival benefit with respect to the seminal percutaneous technique, ethanol injection, in meta-analyses of randomized controlled trials, and is currently established as the standard ablative modality. Nevertheless, novel thermal and nonthermal techniques for tumor ablation-including microwave ablation and irreversible electroporation-seem to have potential to improve the efficacy of RFA and are currently undergoing clinical investigation.

  19. Polyhedra and Higher Dimensions.

    ERIC Educational Resources Information Center

    Scott, Paul

    1988-01-01

    Describes the definition and characteristics of a regular polyhedron, tessellation, and pseudopolyhedra with diagrams. Discusses the nature of simplex, hypercube, and cross-polytope in the fourth dimension and beyond. (YP)

  20. Dimensions of Aesthetic Perception.

    ERIC Educational Resources Information Center

    Biaggio, Mary Kay; Supplee, Katherine A.

    1983-01-01

    Examines the validity of three dimensions of aesthetic perception: hedonic value, arousal, and uncertainty. Hedonic interest and arousal factors were found to differ from factors previously reported, while the uncertainty factor paralleled that previously reported. (Author/RH)

  1. Rokhlin Dimension for Flows

    NASA Astrophysics Data System (ADS)

    Hirshberg, Ilan; Szabó, Gábor; Winter, Wilhelm; Wu, Jianchao

    2016-10-01

    We introduce a notion of Rokhlin dimension for one parameter automorphism groups of {C^*} -algebras. This generalizes Kishimoto's Rokhlin property for flows, and is analogous to the notion of Rokhlin dimension for actions of the integers and other discrete groups introduced by the authors and Zacharias in previous papers. We show that finite nuclear dimension and absorption of a strongly self-absorbing {C^*} -algebra are preserved under forming crossed products by flows with finite Rokhlin dimension, and that these crossed products are stable. Furthermore, we show that a flow on a commutative {C^*} -algebra arising from a free topological flow has finite Rokhlin dimension, whenever the spectrum is a locally compact metrizable space with finite covering dimension. For flows that are both free and minimal, this has strong consequences for the associated crossed product {C^{*}} -algebras: Those containing a non-zero projection are classified by the Elliott invariant (for compact manifolds this consists of topological {K} -theory together with the space of invariant probability measures and a natural pairing given by the Ruelle-Sullivan map).

  2. Plasma-mediated ablation of biofilm contamination

    NASA Astrophysics Data System (ADS)

    Guo, Zhixiong; Wang, Xiaoliang; Huang, Huan

    2010-12-01

    Ultra-short pulsed laser removal of thin biofilm contamination on different substrates has been conducted via the use of plasma-mediated ablation. The biofilms were formed using sheep whole blood. The ablation was generated using a 1.2 ps ultra-short pulsed laser with wavelength centered at 1552 nm. The blood contamination was transformed into plasma and collected with a vacuum system. The single line ablation features have been measured. The ablation thresholds of blood contamination and bare substrates were determined. It is found that the ablation threshold of the blood contamination is lower than those of the beneath substrates including the glass slide, PDMS, and human dermal tissues. The ablation effects of different laser parameters (pulse overlap rate and pulse energy) were studied and ablation efficiency was measured. Proper ablation parameters were found to efficiently remove contamination with maximum efficiency and without damage to the substrate surface for the current laser system. Complete removal of blood contaminant from the glass substrate surface and freeze-dried dermis tissue surface was demonstrated by the USP laser ablation with repeated area scanning. No obvious thermal damage was found in the decontaminated glass and tissue samples.

  3. Percutaneous ablation of hepatocellular carcinoma: current status.

    PubMed

    McWilliams, Justin P; Yamamoto, Shota; Raman, Steven S; Loh, Christopher T; Lee, Edward W; Liu, David M; Kee, Stephen T

    2010-08-01

    Hepatocellular carcinoma (HCC) is an increasingly common disease with dismal long-term survival. Percutaneous ablation has gained popularity as a minimally invasive, potentially curative therapy for HCC in nonoperative candidates. The seminal technique of percutaneous ethanol injection has been largely supplanted by newer modalities, including radiofrequency ablation, microwave ablation, cryoablation, and high-intensity focused ultrasound ablation. A review of these modalities, including technical success, survival rates, and complications, will be presented, as well as considerations for treatment planning and follow-up.

  4. Ablation of liver metastases: current status.

    PubMed

    Flanders, Vincent L; Gervais, Debra A

    2010-08-01

    Local ablative therapy for the treatment of metastatic disease to the liver has been evaluated most extensively in colorectal cancer with 5-year survival rates up to 55% after RF ablation. Recent findings suggest selected patients with other malignant processes may benefit as well, but conclusive evidence is limited. This article reviews the available literature regarding the use of radiofrequency ablation, microwave ablation, and cryoablation in the treatment of metastatic disease to the liver. The published results of each of these modalities in the treatment of metastatic disease to the liver are promising, and outcomes continue to be evaluated.

  5. Development of a Laser Ablation ICPMS Rutile Standard

    NASA Astrophysics Data System (ADS)

    Lytle, M. L.; Kohn, M. J.

    2015-12-01

    Rutile is a common accessory mineral in igneous and high-grade metamorphic rocks and igneous, with many applications in geosciences. Rutile geochemistry, especially the high field strength elements (i.e., Nb and Ta), monitors many geological processes including subduction-zone metamorphism, while Zr provides temperature information in buffering assemblages. Rutile can also be used for U-Pb geochronology, but typically low U concentrations can make age dating difficult. Many applications of rutile now rely on laser ablation ICPMS (LA-ICPMS) analysis, a major disadvantage of this technique is the lack of reliable rutile standards. Here, we present laser ablation data of several rutile megacrysts from around the world, illustrating typical geochemical characteristics of potential standards. Whole-grain transects and depth profiles were collected on several rutiles, including Graves Mountain, Kragerø, Madagascar, Mozambique, Quebec, and Diamantina. Most transects, particularly across Graves Mountain and Diamantina, show dramatic zoning in Zr (up to 100 ppm), U (up to 10 ppm), and Nb (up to 1000 ppm). Rutile grains from Mozambique and Kragerø show little variation in concentration in Zr, U, and Nb. However, U concentrations generally range from 1ppm (Graves Mountain) to 45ppm (Kragero). Depth profiles (30-80s analysis; 15-40 μm) showed a combination of slight surface contamination plus minor to significant near-rim zoning. Some samples, such as Mozambique, show minor concentration changes in Zr, Nb, and Ta over the outer 10 μm but are otherwise unzoned, whereas U concentrations decrease for 25 μm then are constant. Kragero shows depth zoning throughout for Zr, Ta, and U but Nb is unzoned. Some rutile megacrysts show promise as standards (e.g. Mozambique and Kragero), but must be prepared to eliminate crystal surfaces. Other megacrysts would have to be subsampled within specific crystals to isolate chemical homogeneous domains.

  6. Myocardial tissue ablation by single high-energy laser pulses for ELR and TMR

    NASA Astrophysics Data System (ADS)

    Theisen, Dirk; Brinkmann, Ralf; Stubbe, Hans-Martin; Birngruber, Reginald

    1999-02-01

    The objective of this study is to compare the ablation sites induced by two different laser and application systems for myocardial laser revascularization. One system used was an 800 W CO2 laser, which is clinically established for transmyocardial laser revascularization (TMR). The second system was a self-designed Holmium laser emitting single high energy pulses for the minimal invasive approach of endocardial laser revascularization (ELR), whereby the laser light is transmitted via optical fiber into the left ventricle to ablate the myocardial channels from the inside. The laser energy was applied to Polyacrylamide (PAA) as transparent tissue phantom and in water as blood phantom. The ablation dynamics were investigated by high speed flash photography recording a picture series of a single event. Reperfused ex- vivo porcine hearts were treated to quantify differences in the thermal-mechanical damage ranges by polarization light microscopy. Ablation dynamics in water revealed oscillatory changes of the axial length of the steam bubbles between 3 mm and 12 mm during the CO2 laser pulse. For the Holmium laser pulse a maximal axial and lateral length of 5 mm was observed. The lateral dimensions of the bubbles were maximal 1 mm with the CO2- and 3.5 mm with the Holmium laser system. In PAA bubbles also collapse during the laser pulse which affects the size of the ablated channels. Using 12 J Holmium laser pulses for ablation of PAA, channel depths around 7 mm were found. Single Holmium laser pulses demonstrate ablations comparable in size and thermal- mechanical collateral damage to those achieved with the standard CO2 laser. The results are very encouraging for single pulse ELR and demonstrate the potential of a catheter based minimal invasive procedure for laser heart reperfusion.

  7. Seeing the Invisible: Revealing Atrial Ablation Lesions Using Hyperspectral Imaging Approach

    PubMed Central

    Muselimyan, Narine; Swift, Luther M.; Asfour, Huda; Chahbazian, Tigran; Mazhari, Ramesh; Mercader, Marco A.; Sarvazyan, Narine A.

    2016-01-01

    Background Currently, there are limited means for high-resolution monitoring of tissue injury during radiofrequency ablation procedures. Objective To develop the next generation of visualization catheters that can reveal irreversible atrial muscle damage caused by ablation and identify viability gaps between the lesions. Methods Radiofrequency lesions were placed on the endocardial surfaces of excised human and bovine atria and left ventricles of blood perfused rat hearts. Tissue was illuminated with 365nm light and a series of images were acquired from individual spectral bands within 420-720nm range. By extracting spectral profiles of individual pixels and spectral unmixing, the relative contribution of ablated and unablated spectra to each pixel was then displayed. Results of spectral unmixing were compared to lesion pathology. Results RF ablation caused significant changes in the tissue autofluorescence profile. The magnitude of these spectral changes in human left atrium was relatively small (< 10% of peak fluorescence value), yet highly significant. Spectral unmixing of hyperspectral datasets enabled high spatial resolution, in-situ delineation of radiofrequency lesion boundaries without the need for exogenous markers. Lesion dimensions derived from hyperspectral imaging approach strongly correlated with histological outcomes. Presence of blood within the myocardium decreased the amplitude of the autofluorescence spectra while having minimal effect on their overall shapes. As a result, the ability of hyperspectral imaging to delineate ablation lesions in vivo was not affected. Conclusions Hyperspectral imaging greatly increases the contrast between ablated and unablated tissue enabling visualization of viability gaps at clinically relevant locations. Data supports the possibility for developing percutaneous hyperspectral catheters for high-resolution ablation guidance. PMID:27930718

  8. Laser ablation of GaAs in liquid: the role of laser pulse duration

    NASA Astrophysics Data System (ADS)

    De Bonis, Angela; Galasso, Agostino; Santagata, Antonio; Teghil, Roberto

    2016-01-01

    The synthesis of gallium arsenide (GaAs) nanoparticles has attracted wide scientific and technological interest due to the possibility of tuning the GaAs NP (nanoparticle) band gap across the visible spectrum and their consequent use in optoelectronic devices. In recent years, laser ablation in liquid (LAL) has been widely used for the preparation of colloidal solutions of semiconducting and metallic nanoparticles, thanks to its flexibility. With the aim of highlighting the key role played by laser pulse duration on the ablation mechanism and on the properties of the obtained materials, laser ablation of a gallium arsenide target in acetone was performed using laser sources operating in two different temporal regimes: Nd:glass laser (λ   =  527 nm, pulse duration of 250 fs and frequency repetition rate of 10 Hz) and Nd:YAG laser (λ   =  532 nm, pulse duration of 7 ns and frequency repetition rate of 10 Hz). The ablation process was studied following the dynamics of the laser induced shock waves (SWs) and cavitation bubbles (CBs) by fast shadowgraphy, showing that CB dimension and lifetime is related to the laser pulse length. A characterization of the obtained materials by TEM (transmission electron microscopy) and microRaman spectroscopy have shown that quite spherical gallium oxide/GaAs nanoparticles can be obtained by nanosecond laser ablation. On the other hand, pure polycrystalline GaAs nanoparticles can be produced by using an ultrashort laser source.

  9. Production of microscale particles from fish bone by gas flow assisted laser ablation

    NASA Astrophysics Data System (ADS)

    Boutinguiza, M.; Lusquiños, F.; Comesaña, R.; Riveiro, A.; Quintero, F.; Pou, J.

    2007-12-01

    Recycled wastes from fish and seafood can constitute a source of precursor material for different applications in the biomedical field such as bone fillers or precursor material for bioceramic coatings to improve the osteointegration of metallic implants. In this work, fish bones have been used directly as target in a laser ablation system. A pulsed Nd:YAG laser was used to ablate the fish bone material and a transverse air flow was used to extract the ablated material out of the interaction zone. The particles collected at a filter were in the micro and nanoscale range. The morphology as well as the composition of the obtained particles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). The results reveal that the composition of the analyzed particles is similar to that of the inorganic part of the fish bone.

  10. Are the stratospheric dust particles meteor ablation debris or interplanetary dust?

    NASA Technical Reports Server (NTRS)

    Blanchard, M. B.; Kyte, F. T.

    1978-01-01

    Natural and laboratory created fusion crusts and debris from artificial meteor samples were used to develop criteria for recognizing meteor ablation debris in a collection of 5 to 50 micron particles from the stratosphere. These laboratory studies indicate that meteor ablation debris from nickel-iron meteoroids produce spherules containing taenite, wuestite, magnetite, and hematite. These same studies also indicate that ablation debris from chondritic meteoroids produce spheres and fragmentary debris. The spheres may be either silicate rich, containing zoned olivine, magnetite, and glass, or sulfide rich, containing iron oxides (e.g., magnetite, wuestite) and iron sulfides (e.g., pyrrhotite, pentlandite). The fragmentary debris may be either fine-grained aggregates of olivine, magnetite, pyroxene, and occasionally pyrrhotite (derived from the meteorite matrix) or individual olivine and pyroxene grains (derived from meteorite inclusions).

  11. Vehicle type affects filling of fractional laser-ablated channels imaged by optical coherence tomography.

    PubMed

    Olesen, Uffe Høgh; Mogensen, Mette; Haedersdal, Merete

    2017-04-01

    Ablative fractional laser (AFXL) is an emerging method that enhances topical drug delivery. Penetrating the skin in microscopic, vertical channels, termed microscopic treatment zones (MTZs), the fractional technique circumvents the skin barrier and allows increased uptake of topically applied drugs. This study aims to elucidate the impact of vehicle type on the filling of MTZs from application of liquid, gel, and cream vehicles. Ex vivo pig skin was exposed to 10,600 nm fractional CO2 laser at 5% density, 120 μm beam diameter, and fluences of 40 and 80 mJ/microbeam (mJ/mb). Six repetitions were performed for each of six interventions (2 fluences and 3 vehicle types, n = 36). MTZ dimensions and filling by vehicle type were evaluated by optical coherence tomography, using blue tissue dye as a contrast-enhancing agent. Outcome measure was degree of MTZ filling assessed as percentages of empty, partially filled, and completely filled MTZs (108-127 MTZs/intervention analyzed) and evaluated statistically using Kruskal-Wallis and Dunn's tests. MTZs reached mid-dermal levels of 225 μm (40 mJ/mb) and 375 μm (80 mJ/mb) penetration depths (p < 0.0001). Filling of MTZs depended on type of applied vehicle. At 80 mJ/mb, liquid (67% completely filled, p < 0.01) and gel (60%, p < 0.05) formulations filled MTZs significantly better than cream formulation (31%). At 40 mJ/mb, liquid and gel formulations filled 90% (p < 0.05) and 77% (p > 0.05) of MTZs completely versus 55% for cream formulation. Thus, filling was overall greater for more superficial MTZs. In conclusion, vehicle type affects filling of MTZs, which may be of importance for AFXL-assisted drug delivery.

  12. Laser Navigation for Radiofrequency Ablation

    SciTech Connect

    Varro, Zoltan; Locklin, Julia K. Wood, Bradford J.

    2004-09-15

    A 45-year-old male with renal cell carcinoma secondary to von-Hippel Lindau (VHL) disease presented for radiofrequency ablation (RFA) of kidney tumors. Due to his prior history of several partial nephrectomies and limited renal reserve, RFA was chosen because of its relatively nephron-sparing nature. A laser guidance device was used to help guide probe placement in an attempt to reduce procedure time and improve targeting accuracy. The device was successful at guiding needle placement, as both tumors were located with a single pass. Follow-up CT scan confirmed accurate needle placement, showing an area of coagulation necrosis covering the previously seen tumor.

  13. Perceptual dimensions differentiate emotions.

    PubMed

    Cavanaugh, Lisa A; MacInnis, Deborah J; Weiss, Allen M

    2015-08-26

    Individuals often describe objects in their world in terms of perceptual dimensions that span a variety of modalities; the visual (e.g., brightness: dark-bright), the auditory (e.g., loudness: quiet-loud), the gustatory (e.g., taste: sour-sweet), the tactile (e.g., hardness: soft vs. hard) and the kinaesthetic (e.g., speed: slow-fast). We ask whether individuals use perceptual dimensions to differentiate emotions from one another. Participants in two studies (one where respondents reported on abstract emotion concepts and a second where they reported on specific emotion episodes) rated the extent to which features anchoring 29 perceptual dimensions (e.g., temperature, texture and taste) are associated with 8 emotions (anger, fear, sadness, guilt, contentment, gratitude, pride and excitement). Results revealed that in both studies perceptual dimensions differentiate positive from negative emotions and high arousal from low arousal emotions. They also differentiate among emotions that are similar in arousal and valence (e.g., high arousal negative emotions such as anger and fear). Specific features that anchor particular perceptual dimensions (e.g., hot vs. cold) are also differentially associated with emotions.

  14. Minimization of thermomechanical side effects in IR ablation by use of Q-switched double pulses

    NASA Astrophysics Data System (ADS)

    Vogel, Alfred; Schmidt, Peter; Flucke, Barbara

    2001-07-01

    Holmium laser pulses (λ= 2.1 m) are often used for medical laser applications inside the human body, because they can be transmitted through low-OH quartz fibers, and they are relatively well absorbed in water and biological tissues. However, large thermal damage zones were observed after application of free-running holmium laser pulses for arthroscopic surgery. The aim of our study is to reduce thermal damage without introducing additional mechanical damage and without impairing the hemostatic action of the laser radiation. For that purpose we use double pulses from a custom-made acousto-optically Q- switched thulium laser (λ = 2.0 μm) that can emit pulses with energies of up to 150 mJ. The penetration depth of the thulium laser radiation (170 μm) as well as the thermal damage zone are only half as large as that of the holmium laser. The use of Q-switched pulses creates stress confinement conditions leading to a more efficient ablation than with free running pulses. For a given ablation depth, the residual heat deposited in the tissue is therefore smaller than with free running pulses and, hence, also the thermal damage zone. This reduction of thermal damage is possible even though the free-running pulses already fulfil the condition for thermal confinement. The thermal damage zone was only 100 μm for the Q-switched thulium pulses but 200 μm for the free-running pulses. The degree of thermal damage was, in addition, much more severe for the free-running pulses. Q-switched pulses lead to an explosive ablation of the target material. In a liquid environment, this gives rise to the formation of cavitation effects, we release a pre-pulse with small energy (40 mJ) before each ablation pulse of up to 150 mJ. The pre-pulse produces a small cavity that is then filled by the ablation products of the main pulse. The ablation pulse is emitted about 100 μs after the pre-pulse when the bubble is maximally expanded. This way, no additional cavitation effects are induced

  15. Possible role for cryoballoon ablation of right atrial appendage tachycardia when conventional ablation fails.

    PubMed

    Amasyali, Basri; Kilic, Ayhan

    2015-06-01

    Focal atrial tachycardia arising from the right atrial appendage usually responds well to radiofrequency ablation; however, successful ablation in this anatomic region can be challenging. Surgical excision of the right atrial appendage has sometimes been necessary to eliminate the tachycardia and prevent or reverse the resultant cardiomyopathy. We report the case of a 48-year-old man who had right atrial appendage tachycardia resistant to multiple attempts at ablation with use of conventional radiofrequency energy guided by means of a 3-dimensional mapping system. The condition led to cardiomyopathy in 3 months. The arrhythmia was successfully ablated with use of a 28-mm cryoballoon catheter that had originally been developed for catheter ablation of paroxysmal atrial fibrillation. To our knowledge, this is the first report of cryoballoon ablation without isolation of the right atrial appendage. It might also be an alternative to epicardial ablation or surgery when refractory atrial tachycardia originates from the right atrial appendage.

  16. Local Ablation for Hepatocellular Carcinoma in Taiwan

    PubMed Central

    Lin, Shi-Ming

    2013-01-01

    Hepatocellular carcinoma (HCC) is the second commonest cancer in Taiwan. The national surveillance program can detect HCC in its early stages, and various curative modalities (including surgical resection, orthotopic liver transplantation, and local ablation) are employed for the treatment of small HCC. Local ablation therapies are currently advocated for early-stage HCC that is unresectable because of co-morbidities, the need to preserve liver function, or refusal of resection. Among the various local ablation therapies, the most commonly used modalities include percutaneous ethanol injection and radiofrequency ablation (RFA); percutaneous acetic acid injection and microwave ablation are used less often. RFA is more commonly employed than other local ablative modalities in Taiwan because the technique is highly effective, minimally invasive, and requires fewer sessions. RFA is therefore advocated in Taiwan as the first-line curative therapy for unresectable HCC or even for resectable HCC. However, current RFA procedures are less effective against tumors that are in high-risk or difficult-to-ablate locations, are poorly visualized on ultrasonography (US), or are large. Recent advancements in RFA in Taiwan can resolve these issues by the creation of artificial ascites or pleural effusion, application of real-time virtual US assistance, use of combination therapy before RFA, or use of switching RF controllers with multiple electrodes. This review article provides updates on the clinical outcomes and advances in local ablative modalities (mostly RFA) for HCC in Taiwan. PMID:24159599

  17. Testing and evaluation of light ablation decontamination

    SciTech Connect

    Demmer, R.L.; Ferguson, R.L.

    1994-10-01

    This report details the testing and evaluation of light ablation decontamination. It details WINCO contracted research and application of light ablation efforts by Ames Laboratory. Tests were conducted with SIMCON (simulated contamination) coupons and REALCON (actual radioactive metal coupons) under controlled conditions to compare cleaning effectiveness, speed and application to plant process type equipment.

  18. Effective temperatures of polymer laser ablation

    NASA Astrophysics Data System (ADS)

    Furzikov, Nickolay P.

    1991-09-01

    Effective temperatures of laser ablation of certain polymers are extracted from experimental dependences of ablation depths on laser fluences. Dependence of these temperatures on laser pulse durations is established. Comparison with the known thermodestruction data shows that the effective temperature corresponds to transient thermodestruction proceeding by the statistically most probable way.

  19. Ablative therapies for small renal tumours.

    PubMed

    Castro, Arturo; Jenkins, Lawrence C; Salas, Nelson; Lorber, Gideon; Leveillee, Raymond J

    2013-05-01

    Improvements in imaging technology have resulted in an increase in detection of small renal masses (SRMs). Minimally invasive ablation modalities, including cryoablation, radiofrequencey ablation, microwave ablation and irreversible electroporation, are currently being used to treat SRMs in select groups of patients. Cryoablation and radiofrequency ablation have been extensively studied. Presently, cryoablation is gaining popularity because the resulting ice ball can be visualized easily using ultrasonography. Tumour size and location are strong predictors of outcome of radiofrequency ablation. One of the main benefits of microwave ablation is that microwaves can propagate through all types of tissue, including desiccated and charred tissue, as well as water vapour, which might be formed during the ablation. Irreversible electroporation has been shown in animal studies to affect only the cell membrane of undesirable target tissues and to spare adjacent structures; however, clinical studies that depict the efficacy and safety of this treatment modality in humans are still sparse. As more experience is gained in the future, ablation modalities might be utilized in all patients with tumours <4 cm in diameter, rather than just as an alternative treatment for high-risk surgical patients.

  20. Precisely shaped acoustic ablation of tumors utilizing steerable needle and 3D ultrasound image guidance

    NASA Astrophysics Data System (ADS)

    Boctor, Emad M.; Stolka, Philipp; Kang, Hyun-Jae; Clarke, Clyde; Rucker, Caleb; Croom, Jordon; Burdette, E. Clif; Webster, Robert J., III

    2010-02-01

    Many recent studies have demonstrated the efficacy of interstitial ablative approaches for the treatment of hepatic tumors. Despite these promising results, current systems remain highly dependent on operator skill, and cannot treat many tumors because there is little control of the size and shape of the zone of necrosis, and no control over ablator trajectory within tissue once insertion has taken place. Additionally, tissue deformation and target motion make it extremely difficult to place the ablator device precisely into the target. Irregularly shaped target volumes typically require multiple insertions and several overlapping (thermal) lesions, which are even more challenging to accomplish in a precise, predictable, and timely manner without causing excessive damage to surrounding normal tissues. In answer to these problems, we have developed a steerable acoustic ablator called the ACUSITT with the ability of directional energy delivery to precisely shape the applied thermal dose . In this paper, we address image guidance for this device, proposing an innovative method for accurate tracking and tool registration with spatially-registered intra-operative three-dimensional US volumes, without relying on an external tracking device. This method is applied to guid-ance of the flexible, snake-like, lightweight, and inexpensive ACUSITT to facilitate precise placement of its ablator tip within the liver, with ablation monitoring via strain imaging. Recent advancements in interstitial high-power ultrasound applicators enable controllable and penetrating heating patterns which can be dynamically altered. This paper summarizes the design and development of the first synergistic system that integrates a novel steerable interstitial acoustic ablation device with a novel trackerless 3DUS guidance strategy.

  1. Lung Radiofrequency Ablation: In Vivo Experimental Study with Low-Perfusion-Rate Multitined Electrodes

    SciTech Connect

    Crocetti, Laura Lencioni, Riccardo; Bozzi, Elena; Sbrana, Alberto; Bartolozzi, Carlo

    2008-05-15

    The purpose of this study was to investigate the feasibility and safety of lung radiofrequency (RF) ablation by using low-perfusion-rate, expandable, multitined electrodes in an in vivo animal model. Ten New Zealand White rabbits underwent RF ablation using low-perfusion-rate, expandable, multitined electrodes (Starburst Talon; RITA Medical Systems, Mountain View, CA) and a 200-W RF generator. The electrode was positioned under fluoroscopy guidance and a single percutaneous RF ablation was performed. Saline perfusate was doped with nonionic iodinated contrast agent to render it visible on computed tomography (CT). The pump infused the saline doped with contrast agent into the lateral tines at a rate of 0.1ml/min. The planned ablation was of 3 min, with the hooks deployed to 2 cm at a target temperature of 105{sup o}C. An immediate posttreatment CT scan documented the distribution of the doped saline and the presence of immediate complications. The animals were monitored for delayed complications and sacrificed within 72 h (n = 4), 2 weeks (n = 3), or 4 weeks (n = 3). Assessment of ablation zone and adjacent structures was done at autopsy. Major complications consisted of pneumothorax requiring drainage (n = 2) and skin burn (n = 1). Immediately after the procedure the area of ablation was depicted at CT as a round, well-demarcated area, homogeneously opacified by iodinated contrast medium (mean size, 2.3 {+-} 0.8 cm). The presence of a sharply demarcated area of coagulation necrosis (mean size, 2.1 {+-} 0.4 cm) without severe damage to adjacent structures was confirmed at autopsy. In one case, euthanized at 4 weeks, in whom pneumothorax and pleural effusion were depicted, pleural fibrinous adhesions were demonstrated at autopsy. In conclusion, lung RF ablation performed in an in vivo animal model using low-perfusion-rate, expandable, multitined electrodes is feasible and safe. No severe damage to adjacent structures was demonstrated.

  2. Reduction of picosecond laser ablation threshold and damage via nanosecond pre-pulse for removal of dielectric layers on silicon solar cells

    NASA Astrophysics Data System (ADS)

    Brand, A. A.; Meyer, F.; Nekarda, J.-F.; Preu, R.

    2014-10-01

    Laser microstructuring of thin dielectric layers on sensitive electronic devices, such as crystalline silicon solar cells, requires a careful design of the laser ablation process. For instance, degradation of the substrate's crystallinity can vastly decrease minority carrier lifetime and consequently impair the efficiency of such devices. Short-pulse laser ablation seems well suited for clean and spatially confined structuring because of the small heat-affected zone in the remaining substrate material [Dube and Gonsiorawski in Conference record of the twenty first IEEE photovoltaic specialists conference, 624-628 1990]. The short-time regimes, however, generate steep temperature gradients that can lead to amorphization of the remaining silicon surface. By `heating' the substrate via a non-ablative laser pulse in the nanosecond regime before the actual ablation pulse occurs we are able to prevent amorphization of the surface of the silicon solar cell substrate, while lowering the ablation thresholds of a SiNx layer on crystalline silicon wafers.

  3. Selective Attention to Perceptual Dimensions and Switching between Dimensions

    ERIC Educational Resources Information Center

    Meiran, Nachshon; Dimov, Eduard; Ganel, Tzvi

    2013-01-01

    In the present experiments, the question being addressed was whether switching attention between perceptual dimensions and selective attention to dimensions are processes that compete over a common resource? Attention to perceptual dimensions is usually studied by requiring participants to ignore a never-relevant dimension. Selection failure…

  4. Feasibility of ablative fractional laser-assisted drug delivery with optical coherence tomography

    PubMed Central

    Yang, Chih-Hsun; Tsai, Meng-Tsan; Shen, Su-Chin; Ng, Chau Yee; Jung, Shih-Ming

    2014-01-01

    Fractional resurfacing creates hundreds of microscopic wounds in the skin without injuring surrounding tissue. This technique allows rapid wound healing owing to small injury regions, and has been proven as an effective method for repairing photodamaged skin. Recently, ablative fractional laser (AFL) treatment has been demonstrated to facilitate topical drug delivery into skin. However, induced fractional photothermolysis depends on several parameters, such as incident angle, exposure energy, and spot size of the fractional laser. In this study, we used fractional CO2 laser to induce microscopic ablation array on the nail for facilitating drug delivery through the nail. To ensure proper energy delivery without damaging tissue structures beneath the nail plate, optical coherence tomography (OCT) was implemented for quantitative evaluation of induced microscopic ablation zone (MAZ). Moreover, to further study the feasibility of drug delivery, normal saline was dripped on the exposure area of fingernail and the speckle variance in OCT signal was used to observe water diffusion through the ablative channels into the nail plate. In conclusion, this study establishes OCT as an effective tool for the investigation of fractional photothermolysis and water/drug delivery through microscopic ablation channels after nail fractional laser treatment. PMID:25426321

  5. Efficacy and predictability of soft tissue ablation using a prototype Raman-shifted alexandrite laser.

    PubMed

    Kozub, John A; Shen, Jin-H; Joos, Karen M; Prasad, Ratna; Hutson, M Shane

    2015-10-01

    Previous research showed that mid-infrared free-electron lasers could reproducibly ablate soft tissue with little collateral damage. The potential for surgical applications motivated searches for alternative tabletop lasers providing thermally confined pulses in the 6- to-7-µm wavelength range with sufficient pulse energy, stability, and reliability. Here, we evaluate a prototype Raman-shifted alexandrite laser. We measure ablation thresholds, etch rates, and collateral damage in gelatin and cornea as a function of laser wavelength (6.09, 6.27, or 6.43 µm), pulse energy (up to 3 mJ/pulse), and spot diameter (100 to 600 µm). We find modest wavelength dependence for ablation thresholds and collateral damage, with the lowest thresholds and least damage for 6.09 µm. We find a strong spot-size dependence for all metrics. When the beam is tightly focused (~100-µm diameter), ablation requires more energy, is highly variable and less efficient, and can yield large zones of mechanical damage (for pulse energies>1 mJ). When the beam is softly focused (~300-µm diameter), ablation proceeded at surgically relevant etch rates, with reasonable reproducibility (5% to 12% within a single sample), and little collateral damage. With improvements in pulse-energy stability, this prototype laser may have significant potential for soft-tissue surgical applications.

  6. Efficacy and predictability of soft tissue ablation using a prototype Raman-shifted alexandrite laser

    NASA Astrophysics Data System (ADS)

    Kozub, John A.; Shen, Jin-H.; Joos, Karen M.; Prasad, Ratna; Shane Hutson, M.

    2015-10-01

    Previous research showed that mid-infrared free-electron lasers could reproducibly ablate soft tissue with little collateral damage. The potential for surgical applications motivated searches for alternative tabletop lasers providing thermally confined pulses in the 6- to-7-μm wavelength range with sufficient pulse energy, stability, and reliability. Here, we evaluate a prototype Raman-shifted alexandrite laser. We measure ablation thresholds, etch rates, and collateral damage in gelatin and cornea as a function of laser wavelength (6.09, 6.27, or 6.43 μm), pulse energy (up to 3 mJ/pulse), and spot diameter (100 to 600 μm). We find modest wavelength dependence for ablation thresholds and collateral damage, with the lowest thresholds and least damage for 6.09 μm. We find a strong spot-size dependence for all metrics. When the beam is tightly focused (˜100-μm diameter), ablation requires more energy, is highly variable and less efficient, and can yield large zones of mechanical damage (for pulse energies >1 mJ). When the beam is softly focused (˜300-μm diameter), ablation proceeded at surgically relevant etch rates, with reasonable reproducibility (5% to 12% within a single sample), and little collateral damage. With improvements in pulse-energy stability, this prototype laser may have significant potential for soft-tissue surgical applications.

  7. Efficacy and predictability of soft tissue ablation using a prototype Raman-shifted alexandrite laser

    PubMed Central

    Kozub, John A.; Shen, Jin-H.; Joos, Karen M.; Prasad, Ratna; Shane Hutson, M.

    2015-01-01

    Abstract. Previous research showed that mid-infrared free-electron lasers could reproducibly ablate soft tissue with little collateral damage. The potential for surgical applications motivated searches for alternative tabletop lasers providing thermally confined pulses in the 6- to-7-μm wavelength range with sufficient pulse energy, stability, and reliability. Here, we evaluate a prototype Raman-shifted alexandrite laser. We measure ablation thresholds, etch rates, and collateral damage in gelatin and cornea as a function of laser wavelength (6.09, 6.27, or 6.43  μm), pulse energy (up to 3  mJ/pulse), and spot diameter (100 to 600  μm). We find modest wavelength dependence for ablation thresholds and collateral damage, with the lowest thresholds and least damage for 6.09  μm. We find a strong spot-size dependence for all metrics. When the beam is tightly focused (∼100-μm diameter), ablation requires more energy, is highly variable and less efficient, and can yield large zones of mechanical damage (for pulse energies >1  mJ). When the beam is softly focused (∼300-μm diameter), ablation proceeded at surgically relevant etch rates, with reasonable reproducibility (5% to 12% within a single sample), and little collateral damage. With improvements in pulse-energy stability, this prototype laser may have significant potential for soft-tissue surgical applications. PMID:26456553

  8. Lung Cancer Ablation: Technologies and Techniques

    PubMed Central

    Alexander, Erica S.; Dupuy, Damian E.

    2013-01-01

    The incidence of lung cancers in 2012 is estimated to reach 226,160 new cases, with only a third of patients suitable surgical candidates. Tumor ablation has emerged as an important and efficacious treatment option for nonsurgical lung cancer patients. This localized minimally invasive therapy is best suited for small oligonodular lesions or favorably located metastatic tumors. Radiofrequency ablation has been in use for over a decade, and newer modalities including microwave ablation, cryoablation, and irreversible electroporation have emerged as additional treatment options for patients. Ablation therapies can offer patients and clinicians a repeatable and effective therapy for palliation and, in some cases, cure of thoracic malignancies. This article discusses the available technologies and techniques available for tumor ablation of thoracic malignancies including patient selection, basic aspects of procedure technique, imaging follow-up, treatment outcomes, and comparisons between various therapies. PMID:24436530

  9. Lung cancer ablation: technologies and techniques.

    PubMed

    Alexander, Erica S; Dupuy, Damian E

    2013-06-01

    The incidence of lung cancers in 2012 is estimated to reach 226,160 new cases, with only a third of patients suitable surgical candidates. Tumor ablation has emerged as an important and efficacious treatment option for nonsurgical lung cancer patients. This localized minimally invasive therapy is best suited for small oligonodular lesions or favorably located metastatic tumors. Radiofrequency ablation has been in use for over a decade, and newer modalities including microwave ablation, cryoablation, and irreversible electroporation have emerged as additional treatment options for patients. Ablation therapies can offer patients and clinicians a repeatable and effective therapy for palliation and, in some cases, cure of thoracic malignancies. This article discusses the available technologies and techniques available for tumor ablation of thoracic malignancies including patient selection, basic aspects of procedure technique, imaging follow-up, treatment outcomes, and comparisons between various therapies.

  10. Femtosecond ablation of ultrahard materials

    NASA Astrophysics Data System (ADS)

    Dumitru, G.; Romano, V.; Weber, H. P.; Sentis, M.; Marine, W.

    Several ultrahard materials and coatings of definite interest for tribological applications were tested with respect to their response when irradiated with fs laser pulses. Results on cemented tungsten carbide and on titanium carbonitride are reported for the first time and compared with outcomes of investigations on diamond and titanium nitride. The experiments were carried out in air, in a regime of 5-8 J/cm2 fluences, using the beam of a commercial Ti:sapphire laser. The changes induced in the surface morphology were analysed with a Nomarski optical microscope, and with SEM and AFM techniques. From the experimental data and from the calculated incident energy density distributions, the damage and ablation threshold values were determined. As expected, the diamond showed the highest threshold, while the cemented tungsten carbide exhibited typical values for metallic surfaces. The ablation rates determined (under the above-mentioned experimental conditions) were in the range 0.1-0.2 μm per pulse for all the materials investigated.

  11. Ablative shielding for hypervelocity projectiles

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A. (Inventor)

    1993-01-01

    A hypervelocity projectile shield which includes a hollow semi-flexible housing fabricated from a plastic like, or otherwise transparent membrane which is filled with a fluid (gas or liquid) is presented. The housing has a inlet valve, similar to that on a tire or basketball, to introduce an ablating fluid into the housing. The housing is attached by a Velcro mount or double-sided adhesive tape to the outside surface of a structure to be protected. The housings are arrayed in a side-by-side relationship for complete coverage of the surface to be protected. In use, when a hypervelocity projectile penetrates the outer wall of a housing it is broken up and then the projectile is ablated as it travels through the fluid, much like a meteorite 'burns up' as it enters the earth's atmosphere, and the housing is deflated. The deflated housing can be easily spotted for replacement, even from a distance. Replacement is then accomplished by simply pulling a deflated housing off the structure and installing a new housing.

  12. Tumor Ablation with Irreversible Electroporation

    PubMed Central

    Al-Sakere, Bassim; André, Franck; Bernat, Claire; Connault, Elisabeth; Opolon, Paule; Davalos, Rafael V.; Rubinsky, Boris; Mir, Lluis M.

    2007-01-01

    We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop during the application of the pulses were used to design an efficient treatment protocol with minimal heating of the tissue. Tumor regression was confirmed by histological studies which also revealed that it occurred as a direct result of irreversible cell membrane permeabilization. Parametric studies show that the successful outcome of the procedure is related to the applied electric field strength, the total pulse duration as well as the temporal mode of delivery of the pulses. Our best results were obtained using plate electrodes to deliver across the tumor 80 pulses of 100 µs at 0.3 Hz with an electrical field magnitude of 2500 V/cm. These conditions induced complete regression in 12 out of 13 treated tumors, (92%), in the absence of tissue heating. Irreversible electroporation is thus a new effective modality for non-thermal tumor ablation. PMID:17989772

  13. Simple model for ablative stabilization

    NASA Astrophysics Data System (ADS)

    Mikaelian, Karnig O.

    1992-11-01

    We present a simple analytic model for ablative stablization of the Rayleigh-Taylor instability. In this model the effect of ablation is to move the peak of the perturbations to the location of peak pressure. This mechanism enhances the density-gradient stabilization, which is effective at short wavelengths, and it also enhances the stabilization of long-wavelength perturbations due to finite shell thickness. We consider the following density profile: exponential blowoff plasma with a density gradient β, followed by a constant-density shell of thickness δt. For perturbations of arbitrary wave number k, we present an explicit expression for the growth rate γ as a function of k, β, and δt. We find that ``thick'' shells defined by β δt>=1 have γ2>=0 for any k, while ``thin'' shells defined by β δt<1 can have γ2<0 for small k, reflecting stability by proximity to the back side of the shell. We also present lasnex simulations that are in good agreement with our analytic formulas.

  14. Influence of the embryonic preplate on the organization of the cerebral cortex: a targeted ablation model.

    PubMed

    Xie, Y; Skinner, E; Landry, C; Handley, V; Schonmann, V; Jacobs, E; Fisher, R; Campagnoni, A

    2002-10-15

    Transgenic mice were generated to permit the targeted ablation of cortical preplate cells at the time they are born. In these mice, the 1.3 kb golli promoter of the myelin basic protein gene was used to drive the herpes simplex virus thymidine kinase (TK) transgene in cortical preplate cells. Heterozygous transgenic pairs were bred, and pregnant dams were treated with ganciclovir at embryonic days 11-12 to ablate preplate cells at the time the preplate was forming. This paradigm exposed control (TK-) and experimental (TK+) littermates to exactly the same conditions. Embryological ablation of preplate cells led to an early disruption of the radial glial framework and subplate structure in the developing cortex and dramatically altered the cellular lamination and connectivity of the cortical plate. The disturbed radial glial network contributed to an impaired radial migration of neurons into the cortical plate from the ventricular zone. The cortical plate became dyslaminated, and there was a substantial reduction in short- and long-range cortical projections within the cortex and to subcortical regions. Cell death within the cortical plate and the proliferative zones was substantially increased in the ablated animals. After birth, a cortical lesion developed, which became exacerbated with the secondary onset of hydrocephaly in the second postnatal week. The results underscore the critical importance of the preplate in cortex formation, mediated through its guidance of the formation of radial glial scaffolding, subsequent neuronal migration into the incipient cortical plate, and the final arrangement of its vertical organization and cellular connectivity.

  15. Effects of repeated use and resterilization on structural and functional integrity of microwave ablation antennas.

    PubMed

    Finck, Cyrielle A; Zur Linden, Alex R; Singh, Ameet; Foster, Robert A; Nykamp, Stephanie G; Sears, William C

    2017-04-01

    OBJECTIVE To determine effects of repeated use and resterilization on structural and functional integrity of microwave ablation (MWA) antennas. SAMPLE 17 cooled-shaft MWA antennas (3 groups of 5 antennas/group and 2 control antennas). PROCEDURES 1, 2, and 3 ablations in the livers of bovine cadavers were performed at the maximum recommended settings. Antennas were cleaned and sterilized in hydrogen peroxide plasma, and the process was repeated (reprocessing cycle; n = 6). Control antennas were only sterilized (6 times). Aerobic and anaerobic bacterial cultures were performed, and antennas were microscopically assessed for damage. RESULTS 6 cycles were completed. Thirteen of 15 MWA antennas remained functional for up to 4 cycles, 10 were functional after 5 cycles, and only 7 were functional after 6 cycles. Progressive tearing of the silicone coating of the antennas was observed, with a negative effect of the number of cycles for silicone tearing. Size of the ablation zone decreased mildly over time after cycles 5 and 6; however, this was not considered clinically relevant. No significant changes in the shape of ablation zones were detected. All cultures yielded negative results, except for an isolated case, which was considered a contaminant. CONCLUSIONS AND CLINICAL RELEVANCE Structural and functional integrity of the microwave antennas remained acceptable during repeated use and reprocessing for up to 4 cycles. However, there was a decrease in functional integrity at cycles 5 and 6. We suggest that these microwave antennas be subjected to > 3 reprocessing cycles. Antennas should be carefully examined before reuse.

  16. Moving between Dimensions

    ERIC Educational Resources Information Center

    Stephenson, Paul

    2012-01-01

    The first word of this item is "imagine". This instruction has the potential to signal a journey through a world of geometry that might leave you spellbound. On the other hand, it could be the start of a roller-coaster ride through three dimensions that will tax both your imagination, and your powers of visualisation. It is likely that you will…

  17. Physics in One Dimension

    ERIC Educational Resources Information Center

    Bertel, Erminald

    2013-01-01

    Due to progress in nanotechnology high-quality quantum wires can nowadays be fabricated. The behavior of particles in one dimension differs significantly from that in three-dimensional (3D) systems, yet the physics of such low-dimensional systems is generally not very well represented in standard undergraduate or graduate curricula. For instance,…

  18. Big Mysteries: Extra Dimensions

    SciTech Connect

    Lincoln, Don

    2014-06-10

    The weakness of gravity compared to the other subatomic forces is a real mystery. While nobody knows the answer, one credible solution is that gravity has access to more spatial dimensions than the other three known forces. In this video, Fermilab's Dr. Don Lincoln describes this idea, with the help of some very urbane characters.

  19. Dimensions of Nonverbal Communication.

    ERIC Educational Resources Information Center

    Overmier, Mary; And Others

    After a brief description of the dimensions of nonverbal communication, this booklet presents 21 activities that deal with nonverbal communication. Activities in the booklet involve body movements (kinesics), facial expressions, eye movements, perception and use of space (proxemics), haptics (touch), paralinguistics (vocal elements that accompany…

  20. Constructing gravitational dimensions

    NASA Astrophysics Data System (ADS)

    Schwartz, Matthew

    2003-07-01

    It would be extremely useful to know whether a particular low energy effective theory might have come from a compactification of a higher dimensional space. Here, this problem is approached from the ground up by considering theories with multiple interacting massive gravitons. It is actually very difficult to construct discrete gravitational dimensions which have a local continuum limit. In fact, any model with only nearest neighbor interactions is doomed. If we could find a non-linear extension for the Fierz-Pauli Lagrangian for a graviton of mass mg, which does not break down until the scale Λ2=(mgMPl), this could be used to construct a large class of models whose continuum limit is local in the extra dimension. But this is shown to be impossible: a theory with a single graviton must break down by Λ3=(m2gMPl)1/3. Next, we look at how the discretization prescribed by the truncation of the Kaluza-Klein tower of an honest extra dimension raises the scale of strong coupling. It dictates an intricate set of interactions among various fields which conspire to soften the strongest scattering amplitudes and allow for a local continuum limit, at least at the tree level. A number of candidate symmetries associated with locality in the discretized dimension are also discussed.

  1. Big Mysteries: Extra Dimensions

    ScienceCinema

    Lincoln, Don

    2016-07-12

    The weakness of gravity compared to the other subatomic forces is a real mystery. While nobody knows the answer, one credible solution is that gravity has access to more spatial dimensions than the other three known forces. In this video, Fermilab's Dr. Don Lincoln describes this idea, with the help of some very urbane characters.

  2. Extra Dimensions of Space

    ERIC Educational Resources Information Center

    Lincoln, Don

    2013-01-01

    They say that there is no such thing as a stupid question. In a pedagogically pure sense, that's probably true. But some questions do seem to flirt dangerously close to being really quite ridiculous. One such question might well be, "How many dimensions of space are there?" I mean, it's pretty obvious that there are three:…

  3. Pulsed infrared laser ablation and clinical applications

    NASA Astrophysics Data System (ADS)

    Chan, Kin Foong

    Sufficient light energy deposited in tissue can result in ablation and excessive thermal and mechanical damage to adjacent tissues. The goals of this research are to investigate the mechanisms of pulsed infrared laser ablation of tissue, to optimize laser parameters for minimizing unnecessary damage to healthy tissue, and to explore the potential of using pulsed infrared lasers for clinical applications, especially laser lithotripsy. A dual-channel optical low coherence reflectometer was implemented to measure the expansion and collapse velocities of a Q-switched Ho:YAG (λ = 2.12 μm) laser-induced cavitation in water. Cavitation wall velocities up to 11 m/s were measured with this technique, and the results were in fair agreement with those calculated from fast-flash photographic images. The dependence of ablation threshold fluence on calculus absorption was examined. Preliminary results indicated that the product of optical absorption and ablation threshold fluence, which is the heat of ablation, remained constant for a given urinary calculus type and laser pulse duration. An extended study examined the influence of optical absorption on pulsed infrared laser ablation. An analytical photothermal ablation model was applied and compared to experimental ablation results using an infrared free-electron laser at selected wavelengths between 2.12 μm and 6.45 μm Results were in good agreement with the model, and the ablation depths of urinary calculi were highly dependent upon the calculus optical absorption as well as light attenuation within the intrapulse ablation plume. An efficient wavelength for ablation corresponded to the wavelength of the Er:YAG laser (λ = 2.94 μm) suggested this laser should be examined for laser lithotripsy. Schlieren flash photography, acoustic transient measurements with a piezoelectric polyvinylidene-fluoride needle-hydrophone, mass loss measurements, and chemical analyses were employed to study the ablation mechanisms of the free

  4. Carbon nanocrystals produced by pulsed laser ablation of carbon

    NASA Astrophysics Data System (ADS)

    Mangione, A.; Torrisi, L.; Picciotto, A.; Caridi, F.; Margarone, D.; Fazio, E.; La Mantia, A.; di Marco, G.

    2005-10-01

    Plasma laser ablation experiments were performed irradiating glassy-carbon targets placed in vacuum through a pulsed Nd:YAG laser operating at the second harmonic (532 nm), 9 ns pulse width and 10(9) W/cm(2) density power. Thin films of ablated carbon were deposited on silicon oxide substrates placed at different distances and angles with respect to the target. The analysis of the deposited material was carried out by using surface profiler, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and Raman spectroscopy. Results show the evidence of carbon nanocrystals and nanostructures with dimension of the order of 100 nm deposited on the substrates together with a large amount of amorphous phase. The spectroscopic investigations and the SEM images indicate the formation of nanodiamond seeds as a nucleation process induced on the substrate surface. Nanostructures were investigated as a function of the laser intensity and angle distribution. Experimental results were compared with the literature data coming from nanodiamonds growth with different techniques. Experiments performed at Instituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) of Catania (Italy) and data analysis conducted at Dipartimento di Fisica and DFMTA of the Universita of Messina (Italy), CNR-ITIS of Messina and ST-Microelectronics of Catania will be presented and discussed.

  5. Pulmonary Vein Remodeling Following Atrial Fibrillation Ablation: Implications For The Radiographic Diagnosis Of Pulmonary Vein Stenosis.

    PubMed

    Merchant Md, Faisal M; Levy Bs, Mathew R; Iravanian Md, Shahriar; Weragoda Md, Ramal M; Clermont Md, Edward C; Kelli Md, Heval M; Eisner PhD, Robert L; Vadnais Md, David; El-Chami Md, Mikhael F; Leon Md, Angel R; Delurgio Md, David B

    2016-01-01

    Background: Pulmonary vein (PV) reverse remodeling has been recognized following atrial fibrillation (AF) ablation. However, the extent of physiologic reverse remodeling after AF ablation and the potential impact of reverse remodeling on the radiographic diagnosis of PV stenosis have not been well characterized. Methods: From January 2004 to February 2014, 186 patients underwent paired cardiac magnetic resonance imaging (MRI) to delineate PV orifice dimensions before and after (mean 109 ± 61 days) an initial AF ablation. Results: Negative remodeling of the PV orifice cross sectional area occurred in 67.8% of veins with a mean reduction in area of 21.0 ± 14.1%, and positive remodeling was seen in the remaining PVs with an increase in area of 22.1 ± 23.4% compared to baseline. No PVs demonstrated a reduction in cross-sectional area of > 75% (maximum reduction observed was 58%). Negative remodeling of the PV long axis dimension was observed in 55.2% of veins with a mean reduction of 14.6 ± 9.2% compared to pre-ablation and positive remodeling was observed in 25.3% of PVs with a mean increase in diameter of 14.7 ± 12.6%. Only 1 PV demonstrated a reduction in orifice diameter of > 50%. There were no clinically evident or suspected cases of PV stenosis in this cohort. Conclusions: Negative remodeling of the PV orifice area was noted in the majority of PVs following AF ablation. However, in almost all cases, the extent of negative remodeling was well below commonly used thresholds for the radiographic diagnosis of PV stenosis.

  6. On the Ablation Models of Fuel Pellets

    SciTech Connect

    Rozhansky, V.A.; Senichenkov, I.Yu.

    2005-12-15

    The neutral gas shielding model and neutral-gas-plasma shielding model are analyzed qualitatively. The main physical processes that govern the formation of the shielding gas cloud and, consequently, the ablation rate are considered. For the neutral gas shielding model, simple formulas relating the ablation rate and cloud parameters to the parameters of the pellet and the background plasma are presented. The estimates of the efficiency of neutral gas shielding and plasma shielding are compared. It is shown that the main portion of the energy flux of the background electrons is released in the plasma cloud. Formulas for the ablation rate and plasma parameters are derived in the neutral-gas-plasma shielding model. The question is discussed as to why the neutral gas shielding model describes well the ablation rate of the pellet material, although it does not take into account the ionization effects and the effects associated with the interaction of ionized particles with the magnetic field. The reason is that the ablation rate depends weakly on the energy flux of hot electrons; as a result, the attenuation of this flux by the electrostatic shielding and plasma shielding has little effect on the ablation rate. This justifies the use of the neutral gas shielding model to estimate the ablation rate (to within a factor of about 2) over a wide range of parameters of the pellet and the background plasma.

  7. [Indications for catheter ablation of ventricular tachycardia].

    PubMed

    Deneke, T; Israel, C W; Krug, J; Nentwich, K; Müller, P; Mügge, A; Schade, A

    2013-09-01

    Ventricular tachyarrhythmias (VT) can cause sudden cardiac death. This can be prevented by an implantable cardioverter-defibrillator (ICD) but approximately 25% of patients with an ICD develop electrical storm (≥ 3 VTs within 24 hours) during the course of 4-5 years. This is a life-threatening event even in the presence of an ICD, particularly if incessant VT is present, and may significantly deteriorate the patient's psychological state if multiple shocks are discharged. Catheter ablation of VT has developed into a standard procedure in many specialized electrophysiology centers. Patients with hemodynamically stable and unstable VT are amendable to substrate-based ablation strategies. Catheter ablation can be performed as emergency procedure in patients with electrical storm as well as electively in patients with monomorphic VT stored in ICD memory. In patients with ischemic or non-ischemic cardiomyopathy, VT ablation is complementary to ICD implantation and can reduce the number of ventricular arrhythmia episodes and shocks and should be performed early. In patients with electrical storm, catheter ablation can acutely achieve rhythm stabilization and may improve prognosis in the long term. Further indications for catheter ablation exist in patients with idiopathic VT where catheter ablation represents a curative therapy, and in patients with symptomatic or asymptomatic frequent premature ventricular beats which may improve prognosis in patients with heart failure and cardiac resynchronization therapy.

  8. Analysis of infrared laser tissue ablation

    NASA Astrophysics Data System (ADS)

    McKenzie, Gordon P.; Timmerman, Brenda H.; Bryanston-Cross, Peter J.

    2005-04-01

    The mechanisms involved in infrared laser tissue ablation are studied using a free electron laser (FELIX) in order to clarify whether the increased ablation efficiency reported in literature for certain infrared wavelengths is due to a wavelength effect or to the specific pulse structure of the lasers that are generally used in these studies. Investigations are presented of ablation of vitreous from pigs" eyes using several techniques including protein gel electrophoresis and ablation plume visualization. The ablation effects of three different infrared wavelengths are compared: 3 mm, which is currently in clinical surgical use, and the wavelengths associated with the amide I and amide II bands, i.e. 6.2 mm and 6.45mm, respectively. The results suggest a different ablation mechanism to be in operation for each studied wavelength, thus indicating that the generally reported increased ablation efficiency in the 6-6.5 micron range is due to the wavelength rather than the typical free electron laser pulse structure.

  9. Thermal therapy, Part III: ablation techniques.

    PubMed

    Habash, Riadh W Y; Bansal, Rajeev; Krewski, Daniel; Alhafid, Hafid T

    2007-01-01

    Ablative treatments are gaining increasing attention as an alternative to standard surgical therapies, especially for patients with contraindication or those who refuse open surgery. Thermal ablation is used in clinical applications mainly for treating heart arrhythmias, benign prostate hyperplasia, and nonoperable liver tumors; there is also increasing application to other organ sites, including the kidney, lung, and brain. Potential benefits of thermal ablation include reduced morbidity and mortality in comparison with standard surgical resection and the ability to treat nonsurgical patients. The purpose of this review is to outline and discuss the engineering principles and biological responses by which thermal ablation techniques can provide elevation of temperature in organs within the human body. Because of the individual problems associated with each type of treatment, a wide range of ablation techniques have evolved including cryoablation as well as ultrasound, radiofrequency (RF), microwave, and laser ablation. Aspects of each ablation technique, including mechanisms of action, equipment required, selection of eligible patients, treatment techniques, and patient outcomes are presented, along with a discussion of limitations of the techniques and future research directions.

  10. Thermal protection system ablation sensor

    NASA Technical Reports Server (NTRS)

    Gorbunov, Sergey (Inventor); Martinez, Edward R. (Inventor); Scott, James B. (Inventor); Oishi, Tomomi (Inventor); Fu, Johnny (Inventor); Mach, Joseph G. (Inventor); Santos, Jose B. (Inventor)

    2011-01-01

    An isotherm sensor tracks space vehicle temperatures by a thermal protection system (TPS) material during vehicle re-entry as a function of time, and surface recession through calibration, calculation, analysis and exposed surface modeling. Sensor design includes: two resistive conductors, wound around a tube, with a first end of each conductor connected to a constant current source, and second ends electrically insulated from each other by a selected material that becomes an electrically conductive char at higher temperatures to thereby complete an electrical circuit. The sensor conductors become shorter as ablation proceeds and reduced resistance in the completed electrical circuit (proportional to conductor length) is continually monitored, using measured end-to-end voltage change or current in the circuit. Thermocouple and/or piezoelectric measurements provide consistency checks on local temperatures.

  11. Radiofrequency Ablation: A Nursing Perspective

    PubMed Central

    Locklin, Julia K.; Wood, Bradford J.

    2008-01-01

    Radiofrequency ablation (RFA) has emerged as a safe and predictable technology for treating certain patients with cancer who otherwise have few treatment options. Nurses need to be familiar with all phases of the RFA procedure to create an optimal environment for patients. This article offers a brief review of the RFA procedure and nurses' responsibilities in caring for these patients. Before RFA, nurses should focus on patient education and aggressive hydration. During the procedure, nurses can prevent injury by placing grounding pads appropriately, monitoring vital signs, and medicating patients as needed. After RFA, nurses should assess the skin puncture site, provide adequate pain relief, and, again, hydrate patients. Nurses who care appropriately for RFA recipients may help to improve patient outcomes and make an otherwise frightening procedure more comfortable. PMID:15973845

  12. Ablation of idiopathic ventricular tachycardia.

    PubMed

    Schreiber, Doreen; Kottkamp, Hans

    2010-09-01

    Idiopathic ventricular arrhythmias occur in patients without structural heart disease. They can arise from a variety of specific areas within both ventricles and in the supravalvular regions of the great arteries. Two main groups need to be differentiated: arrhythmias from the outflow tract (OT) region and idiopathic left ventricular, so-called fascicular, tachycardias (ILVTs). OT tachycardia typically originates in the right ventricular OT, but may also occur in the left ventricular OT, particularly in the sinuses of Valsalva or the anterior epicardium or the great cardiac vein. Activation mapping or pace mapping for the OT regions and mapping of diastolic potentials in ILVTs are the mapping techniques that are typically used. The ablation of idiopathic ventricular arrhythmias is highly successful, associated with only rare complications. Newly recognized entities of idiopathic ventricular tachycardias are those originating in the papillary muscles and in the atrioventricular annular regions.

  13. Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

    PubMed

    Huang, Yize; Jivraj, Jamil; Zhou, Jiaqi; Ramjist, Joel; Wong, Ronnie; Gu, Xijia; Yang, Victor X D

    2016-07-25

    A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 106 W/cm2 and the maximum pulsed peak power density is 2.16 × 107 W/cm2. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

  14. Laser-Ablation (U-Th)/He Geochronology

    NASA Astrophysics Data System (ADS)

    Hodges, K.; Boyce, J.

    2003-12-01

    Over the past decade, ultraviolet laser microprobes have revolutionized the field of 40Ar/39Ar geochronology. They provide unprecedented information about Ar isotopic zoning in natural crystals, permit high-resolution characterization of Ar diffusion profiles produced during laboratory experiments, and enable targeted dating of multiple generations of minerals in thin section. We have modified the analytical protocols used for 40Ar/39Ar laser microanalysis for use in (U-Th)/He geochronologic studies. Part of the success of the 40Ar/39Ar laser microprobe stems from fact that measurements of Ar isotopic ratios alone are sufficient for the calculation of a date. In contrast, the (U-Th)/He method requires separate analysis of U+Th and 4He. Our method employs two separate laser microprobes for this process. A target mineral grain is placed in an ultrahigh vacuum chamber fitted with a window of appropriate composition to transmit ultraviolet radiation. A focused ArF (193 nm) excimer laser is used to ablate tapered cylindrical pits on the surface of the target. The liberated material is scrubbed with a series of getters in a fashion similar to that used for 40Ar/39Ar geochronology, and the 4He abundance is determined using a quadrupole mass spectrometer with well-calibrated sensitivity. A key requirement for calculation of the 4He abundance in the target is a precise knowledge of the volume of the ablation pit. This is the principal reason why we employ the ArF excimer for 4He analysis rather than a less-expensive frequency-multiplied Nd-YAG laser; the excimer creates tapered cylindrical pits with extremely reproducible and easily characterized geometry. After 4He analysis, U and Th are measured on the same sample surface using the more familiar technique of laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Our early experiments have been done using a frequency-quintupled Nd-YAG microprobe (213nm), While the need to analyze U+Th and He in separate

  15. Ablative skin resurfacing with a novel microablative CO2 laser.

    PubMed

    Gotkin, Robert H; Sarnoff, Deborah S; Cannarozzo, Giovanni; Sadick, Neil S; Alexiades-Armenakas, Macrene

    2009-02-01

    Carbon dioxide (CO2) laser skin resurfacing has been a mainstay of facial rejuvenation since its introduction in the mid 1990s. Recently, a new generation of fractional or microablative CO2 lasers has been introduced to the marketplace. According to the concept of fractional photothermolysis, these lasers ablate only a fraction of the epidermal and dermal architecture in the treatment area. An array of microscopic thermal wounds is created that ablates the epidermis and dermis within very tiny zones; adjacent to these areas, the epidermis and dermis are spared. This microablative process of laser skin resurfacing has proven safe and effective not only for facial rejuvenation, but elsewhere on the body as well. It is capable of improving wrinkles, acne scars, and other types of atrophic scars and benign pigmented lesions associated with elastotic, sun-damaged skin. Because of the areas of spared epidermis and dermis inherent in a procedure that employs fractional photothermolysis, healing is more rapid compared to fully ablative CO2 laser skin resurfacing and downtime is proportionately reduced. A series of 32 consecutive patients underwent a single laser resurfacing procedure with the a new microablative CO2 laser. All patients were followed for a minimum of 6 months and were asked to complete patient satisfaction questionnaires; a 6 month postoperative photographic evaluation by an independent physician, not involved in the treatment, was also performed. Both sets of data were graded and reported on a quartile scale. Results demonstrated greater than 50% improvement in almost all patients with those undergoing treatment for wrinkles, epidermal pigment or solar elastosis deriving the greatest change for the better (>75%).

  16. Nanosecond laser ablation of gold nanoparticle films

    SciTech Connect

    Ko, Seung H.; Choi, Yeonho; Hwang, David J.; Grigoropoulos, Costas P.; Chung, Jaewon; Poulikakos, Dimos

    2006-10-02

    Ablation of self-assembled monolayer protected gold nanoparticle films on polyimide was explored using a nanosecond laser. When the nanoparticle film was ablated and subsequently thermally sintered to a continuous film, the elevated rim structure by the expulsion of molten pool could be avoided and the ablation threshold fluence was reduced to a value at least ten times lower than the reported threshold for the gold film. This could be explained by the unusual properties of nanoparticle film such as low melting temperature, weak bonding between nanoparticles, efficient laser energy deposition, and reduced heat loss. Finally, submicron lines were demonstrated.

  17. IR laser ablation of dental enamel

    NASA Astrophysics Data System (ADS)

    Fried, Daniel

    2000-03-01

    An overview of the basic mechanisms of IR laser ablation of dental enamel is presented. Enamel is a highly structured tissue consisting of an heterogeneous distribution of water, mineral, protein and lipid. Absorption bands of water and carbonated hydroxyapatite can be selectively targeted from 2.7 to 11-micrometer via several laser wavelengths. Mechanistic differences in the nature of ablation and the varying surface morphology produced can be explained by the microstructure of the tissue. Suggested criteria for the choice of the optimum laser parameters for clinical use, the influence of plasma shielding and the role of exogenous water on the mechanism of ablation are discussed.

  18. Diamond Ablators for Inertial Confinement Fusion

    SciTech Connect

    Biener, J; Mirkarimi, P B; Tringe, J W; Baker, S L; Wang, Y M; Kucheyev, S O; Teslich, N E; Wu, K J; Hamza, A V; Wild, C; Woerner, E; Koidl, P; Bruehne, K; Fecht, H

    2005-06-21

    Diamond has a unique combination of physical properties for the inertial confinement fusion ablator application, such as appropriate optical properties, high atomic density, high yield strength, and high thermal conductivity. Here, we present a feasible concept to fabricate diamond ablator shells. The fabrication of diamond capsules is a multi-step process, which involves diamond chemical vapor deposition on silicon mandrels followed by polishing, microfabrication of holes, and removing of the silicon mandrel by an etch process. We also discuss the pros and cons of coarse-grained optical quality and nanocrystalline chemical vapor deposition diamond films for the ablator application.

  19. Radiofrequency Ablation of Persistent Atrial Fibrillation

    PubMed Central

    Hussein, Ayman A.; Saliba, Walid I.; Barakat, Amr; Bassiouny, Mohammed; Chamsi-Pasha, Mohammed; Al-Bawardy, Rasha; Hakim, Ali; Tarakji, Khaldoun; Baranowski, Bryan; Cantillon, Daniel; Dresing, Thomas; Tchou, Patrick; Martin, David O.; Varma, Niraj; Bhargava, Mandeep; Callahan, Thomas; Niebauer, Mark; Kanj, Mohamed; Chung, Mina; Natale, Andrea; Lindsay, Bruce D.; Wazni, Oussama M.

    2017-01-01

    Background Various ablation strategies of persistent atrial fibrillation (PersAF) have had disappointing outcomes, despite concerted clinical and research efforts, which could reflect progressive atrial fibrillation–related atrial remodeling. Methods and Results Two-year outcomes were assessed in 1241 consecutive patients undergoing first-time ablation of PersAF (2005–2012). The time intervals between the first diagnosis of PersAF and the ablation procedures were determined. Patients had echocardiograms and measures of B-type natriuretic peptide and C-reactive protein before the procedures. The median diagnosis-to-ablation time was 3 years (25th–75th percentiles 1–6.5). With longer diagnosis-to-ablation time (based on quartiles), there was a significant increase in recurrence rates in addition to an increase in B-type natriuretic peptide levels (P=0.01), C-reactive protein levels (P<0.0001), and left atrial size (P=0.03). The arrhythmia recurrence rates over 2 years were 33.6%, 52.6%, 57.1%, and 54.6% in the first, second, third, and fourth quartiles, respectively (Pcategorical<0.0001). In Cox Proportional Hazard analyses, B-type natriuretic peptide levels, C-reactive protein levels, and left atrial size were associated with arrhythmia recurrence. The diagnosis-to-ablation time had the strongest association with the ablation outcomes which persisted in multivariable Cox analyzes (hazard ratio for recurrence per +1Log diagnosis-to-ablation time 1.27, 95% confidence interval 1.14–1.43; P<0.0001; hazard ratio fourth versus first quartile 2.44, 95% confidence interval 1.68–3.65; Pcategorical<0.0001). Conclusions In patients with PersAF undergoing ablation, the time interval between the first diagnosis of PersAF and the catheter ablation procedure had a strong association with the ablation outcomes, such as shorter diagnosis-to-ablation times were associated with better outcomes and in direct association with markers of atrial remodeling. PMID:26763227

  20. Ablation of pulmonary malignancy: current status.

    PubMed

    Pua, Bradley B; Thornton, Raymond H; Solomon, Stephen B

    2010-08-01

    Since the first reported use of radiofrequency ablation of the lung in 2000, the field of image-guided lung ablation has received a considerable amount of attention. Survival studies have demonstrated the potential utility of thermal ablation in the treatment of patients with early-stage primary and limited secondary pulmonary tumors with promising results. Diagnostic imaging studies have advanced the understanding of the expected immediate postablation appearance of treated lesions, leading the way for early detection of local tumor progression. These survival studies and the expected imaging follow-up of these patients are reviewed herein.

  1. Cultural dimensions of learning

    NASA Astrophysics Data System (ADS)

    Eyford, Glen A.

    1990-06-01

    How, what, when and where we learn is frequently discussed, as are content versus process, or right brain versus left brain learning. What is usually missing is the cultural dimension. This is not an easy concept to define, but various aspects can be identified. The World Decade for Cultural Development emphasizes the need for a counterbalance to a quantitative, economic approach. In the last century poets also warned against brutalizing materialism, and Sorokin and others have described culture more recently in terms of cohesive basic values expressed through aesthetics and institutions. Bloom's taxonomy incorporates the category of affective learning, which internalizes values. If cultural learning goes beyond knowledge acquisition, perhaps the surest way of understanding the cultural dimension of learning is to examine the aesthetic experience. This can use myths, metaphors and symbols, and to teach and learn by using these can help to unlock the human potential for vision and creativity.

  2. Dimensions of Intelligent Systems

    DTIC Science & Technology

    2002-08-01

    strategies - the intelligent parts of a cognitive model. This was necessary to achieve effective time performance - conventional AI techniques were too slow...Dimensions of Intelligent Systems Dr. Gary Berg-Cross Knowledge Strategies Division, SLAG, Inc. Potomac, Maryland 20854, USA 1. Abstract As...NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SLAG, Inc,Knowledge Strategies Division,Potomac,MD,20854 8

  3. Introduction to Extra Dimensions

    SciTech Connect

    Rizzo, Thomas G.

    2010-07-12

    Extra dimensions provide a very useful tool in addressing a number of the fundamental problems faced by the Standard Model. The following provides a very basic introduction to this very broad subject area as given at the VIII School of the Gravitational and Mathematical Physics Division of the Mexican Physical Society in December 2009. Some prospects for extra dimensional searches at the 7 TeV LHC with {approx}1 fb{sup -1} of integrated luminosity are provided.

  4. Introduction to Extra Dimensions

    SciTech Connect

    Rizzo, Thomas G.; /SLAC

    2010-04-29

    Extra dimensions provide a very useful tool in addressing a number of the fundamental problems faced by the Standard Model. The following provides a very basic introduction to this very broad subject area as given at the VIII School of the Gravitational and Mathematical Physics Division of the Mexican Physical Society in December 2009. Some prospects for extra dimensional searches at the 7 TeV LHC with {approx}1 fb{sup -1} of integrated luminosity are provided.

  5. Infinitely Large New Dimensions

    SciTech Connect

    Arkani-Hamed, Nima; Dimopoulos, Savas; Dvali, Gia; Kaloper, Nemanja

    1999-07-29

    We construct intersecting brane configurations in Anti-de-Sitter space localizing gravity to the intersection region, with any number n of extra dimensions. This allows us to construct two kinds of theories with infinitely large new dimensions, TeV scale quantum gravity and sub-millimeter deviations from Newton's Law. The effective 4D Planck scale M{sub Pl} is determined in terms of the fundamental Planck scale M{sub *} and the AdS radius of curvature L via the familiar relation M{sub Pl}{sup 2} {approx} M{sub *}{sup 2+n} L{sup n}; L acts as an effective radius of compactification for gravity on the intersection. Taking M{sub *} {approx} TeV and L {approx} sub-mm reproduces the phenomenology of theories with large extra dimensions. Alternately, taking M{sub *} {approx} L{sup -1} {approx} M{sub Pl}, and placing our 3-brane a distance {approx} 100M{sub Pl}{sup -1} away from the intersection gives us a theory with an exponential determination of the Weak/Planck hierarchy.

  6. Use of a circular mapping and ablation catheter for ablation of atypical right ventricular outflow tract arrhythmia.

    PubMed

    Katritsis, Demosthenes G; Giazitzoglou, Eleftherios; Paxinos, George

    2010-02-01

    A new technique for ablation of persistent ectopic activity with atypical electrocardiographic characteristics at the vicinity of the right ventricular outflow tract is described. A new circular mapping and ablation catheter initially designed for pulmonary vein ablation was used. Abolition of ectopic activity was achieved with minimal fluoroscopy and ablation times.

  7. Influence of an Angular Hatching Exposure Strategy on the Surface Roughness During Picosecond Laser Ablation of Hard Materials

    NASA Astrophysics Data System (ADS)

    Daniel, Christian; Manderla, Jannik; Hallmann, Sina; Emmelmann, Claus

    Innovative chip breakers for cutting tools made of very hard materials require laser ablation and demand a high quality regarding the manufactured surface. When processing materials such as polycrystalline cubic boron-nitride or tungsten carbide the surface roughness by laser ablation reaches Sa = 1,0-2,9 μm compared to Sa = 0,42 μm achieved by grinding. Therefore in the presented research the influence of the hatching exposure strategy on surface roughness during picosecond laser ablation of tungsten carbide is examined. The areal, layerwise ablation process is separated into its elements which are represented by intersection zones between single and multiple laser vectors. Thus two mechanisms of roughness formation are identified and described by model functions. Further the mechanisms are transferred to areal ablation in which surface roughness decreases due to improved hatching angles compared to a commonly used one of φ= 0°/90°. With this approach the roughness is reduced by approximately factor 2,0-3,5 to Sa = 0,82 μm. In conclusion guidelines are derived which present favorable settings for high quality laser ablation processes.

  8. Laser ablation of a Cu-Al-Ni combinatorial thin film library: analysis of crater morphology and geometry

    NASA Astrophysics Data System (ADS)

    Rebegea, Simina Aurelia; Thomas, Keith; Chawla, Vipin; Michler, Johann; Kong, Ming Chu

    2016-12-01

    The conventional approach to studying laser-workpiece interaction in the ablation regime is to vary beam parameters used on a specimen of uniform chemical composition. The current work instead utilises a pulsed laser beam of constant parameters to ablate a ternary alloy thin film where the chemical composition of the sample varies continuously; this will enhance the understanding of pulsed laser ablation by means of a combinatorial approach. The analysis of the studied workpiece (a Cu-Al-Ni thin film deposited by magnetron sputtering) revealed the presence of both compositional and morphological gradients. Variation in the surface morphology was correlated with aluminium content. Single-pulse laser ablation (Nd:YAG, 1064 nm, 30 ns, 4.54 J/cm2) of the surface resulted in different crater features, geometry and volume. Two characteristic regions separated by a transition zone were identified based on the craters' geometrical and morphological characteristics. The ablated volume increases with the atomic percentage of aluminium up to a threshold value of roughly 30 at.% after which the ablation volume slowly declines. This phenomenon may be attributed to plasma absorption and heat dissipation in the thin film.

  9. 1.5T MRI-guided trans-perineal laser ablation of locally recurrent prostate adenocarcinoma

    NASA Astrophysics Data System (ADS)

    McPhail, E. Frederick; Mynderse, Lance A.; Callstrom, Matthew R.; Gorny, Krzysztof R.; McNichols, Roger J.; Atwell, Thomas D.; Gettman, Matthew T.; Amrami, Kimberly K.; Kawashima, Akira; Woodrum, David A.

    2010-02-01

    Introduction: Biochemical recurrence of prostate cancer after definitive therapy with radical prostatectomy (RP) is known to occur between 25-30%. We present the first known case of 1.5T MRI guided ablation using laser interstitial thermal therapy (LITT) for locally recurrent prostate cancer following RP. Methods: The patient elected to undergo MRI-guided LITT of the biopsy proven cancer recurrence using an FDAapproved MRI compatible, 980nm, 15-watt laser system with MR thermometry. Under T2-weighted MR(1.5T Siemens) imaging, guidance and targeting of the lesions with trans-perineal placement of laser applicators. Multiple cycles of laser energy were used to ablate the tumor. A MRI-compatible urethral cooling catheter was placed to prevent urethral thermal damage. Results: Intra-procedural temperature mapping allowed continuous monitoring of the ablation zone and permitted ablation control until tumor coverage was achieved. Additionally, the protective cooling effects of the urethral cooling catheter could also be seen with the temperature mapping. Post-ablation gadolinium and T2 weighted MR imaging demonstrated an ablation defect encompassing the recurrent tumor with no residual hyper-enhancing nodules. Three month follow-up shows no residual or recurrent tumor seen on MR imaging. Conclusion: This represents the first known, successful, MRI-guided, LITT procedures at 1.5T for locally recurrent prostate adenocarcinoma following RP.

  10. Laser ablation in analytical chemistry - A review

    SciTech Connect

    Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

    2001-10-10

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

  11. Nanoscale ablation through optically trapped microspheres

    NASA Astrophysics Data System (ADS)

    Fardel, Romain; McLeod, Euan; Tsai, Yu-Cheng; Arnold, Craig B.

    2010-10-01

    The ability to directly create patterns with size scales below 100 nm is important for many applications where the production or repair of high resolution and density features is needed. Laser-based direct-write methods have the benefit of being able to quickly and easily modify and create structures on existing devices, but ablation can negatively impact the overall technique. In this paper we show that self-positioning of near-field objectives through the optical trap assisted nanopatterning (OTAN) method allows for ablation without harming the objective elements. Small microbeads are positioned in close proximity to a substrate where ablation is initiated. Upon ablation, these beads are temporarily displaced from the trap but rapidly return to the initial position. We analyze the range of fluence values for which this process occurs and find that there exists a critical threshold beyond which the beads are permanently ejected.

  12. Physical processes of laser tissue ablation

    NASA Astrophysics Data System (ADS)

    Furzikov, Nickolay P.

    1991-05-01

    The revised ablation model applicable to homogeneous tissues is presented. It is based on the thermal mechanism and involves the instability of the laserinduced evaporation (thermodestruction) front the growth of the surface ripple structure the interference of the laser wave and of the surface wave arising by diffraction on the ripples Beer''s law violation the pulsed thermodestruction of the organic structural component the tissue water boiling and gas dynamic expansion of the resulting products into the surrounding medium which is followed by the shock wave formation. The UV and IR ablation schemes were implemented and compared to the corneal ablation experiments. The initial ablation pressure and temperature are given restored from the timeofflight measurements of the supersonic expansion of the product. 1.

  13. Evolving Ablative Therapies for Hepatic Malignancy

    PubMed Central

    Hochwald, Steven N.

    2014-01-01

    The liver is a common site for both primary and secondary malignancy. Hepatic resection and transplantation are the two treatment modalities that have been shown to achieve complete cure, but only 10 to 20% of patients are candidates for these treatments. For the remaining patients, tumor ablation has emerged as the most promising alternative modality. In addition to providing local control and improving survival outcomes, tumor ablation also helps to down stage patients for potential curative treatments, both alone as well as in combination with other treatments. While tumor ablation can be achieved in multiple ways, the introduction of newer ablative techniques has shifted the focus from palliation to potentially curative treatment. Because the long-term safety and survival benefits are not substantive at present, it is important that we strive to evaluate the results from these studies using appropriate comparative outcome methodologies. PMID:24877069

  14. Thermal Ablation Modeling for Silicate Materials

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq

    2016-01-01

    A general 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 the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric 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. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

  15. Pharmacological Tests in Atrial Fibrillation Ablation

    PubMed Central

    Gourraud, Jean-Baptiste; Andrade, Jason G; Macle, Laurent

    2016-01-01

    The invasive management of atrial fibrillation (AF) has been considerably changed by the identification of major sites of AF initiation and/or maintenance within the pulmonary vein antra. Percutaneous catheter ablation of these targets has become the standard of care for sustained maintenance of sinus rhythm. Long-term failure of ablation is related to an inability to create a durable transmural lesion or to identify all of the non-pulmonary vein arrhythmia triggers. Pharmacological challenges during catheter ablation have been suggested to improve outcomes in both paroxysmal and persistent AF. Herein we review the mechanism and evidence for the use of pharmacological adjuncts during the catheter ablation of AF. PMID:28116081

  16. Indications and options for endometrial ablation.

    PubMed

    2008-11-01

    Endometrial ablation is an effective therapeutic option for the management of menorrhagia in properly selected patients. Hysteroscopic and non-hysteroscopic techniques offer similar rates of symptom relief and patient satisfaction.

  17. Percutaneous ablation of malignant thoracic tumors.

    PubMed

    Ghaye, B

    2013-01-01

    Lung cancer is the leading cause of death related to cancer. Fifteen to thirty percent of patients with a localized lung cancer are actually inoperable as they present with poor general condition, limited cardiopulmonary function, or a too high surgical risk. Therefore, minimally invasive treatments are needed and percutaneous ablation seems an attractive option. Thermal ablation can be performed by delivering heat (radiofrequency, microwave, laser) or cold (cryotherapy) through a needle inserted into the tumor under CT guidance. The ideal lesion is less than 2 or 3 cm in diameter. Success of percutaneous thermal ablation appears to be close to those of surgery for localized lung cancer. Nevertheless studies are still needed to definitely assess the role of ablation compared to other emerging techniques, as stereotactic radiotherapy as well as potential synergy with other treatments.

  18. Flexible Ablators: Applications and Arcjet Testing

    NASA Technical Reports Server (NTRS)

    Arnold, James O.; Venkatapathy, Ethiraj; Beck, Robin A S.; Mcguire, Kathy; Prabhu, Dinesh K.; Gorbunov, Sergey

    2011-01-01

    Flexible ablators were conceived in 2009 to meet the technology pull for large, human Mars Exploration Class, 23 m diameter hypersonic inflatable aerodynamic decelerators. As described elsewhere, they have been recently undergoing initial technical readiness (TRL) advancement by NASA. The performance limits of flexible ablators in terms of maximum heat rates, pressure and shear remain to be defined. Further, it is hoped that this emerging technology will vastly expand the capability of future NASA missions involving atmospheric entry systems. This paper considers four topics of relevance to flexible ablators: (1) Their potential applications to near/far term human and robotic missions (2) Brief consideration of the balance between heat shield diameter, flexible ablator performance limits, entry vehicle controllability and aft-body shear layer impingement of interest to designers of very large entry vehicles, (3) The approach for developing bonding processes of flexible ablators for use on rigid entry bodies and (4) Design of large arcjet test articles that will enable the testing of flexible ablators in flight-like, combined environments (heat flux, pressure, shear and structural tensile loading). Based on a review of thermal protection system performance requirements for future entry vehicles, it is concluded that flexible ablators have broad applications to conventional, rigid entry body systems and are enabling to large deployable (both inflatable and mechanical) heat shields. Because of the game-changing nature of flexible ablators, it appears that NASA's Office of the Chief Technologist (OCT) will fund a focused, 3-year TRL advancement of the new materials capable of performance in heat fluxes in the range of 200-600 W/sq. cm. This support will enable the manufacture and use of the large-scale arcjet test designs that will be a key element of this OCT funded activity.

  19. Resonant laser ablation: mechanisms and applications

    SciTech Connect

    Anderson, J.E.; Allen, T.M.; Garrett, A.W.; Gill, C.G.; Hemberger, P.H.; Kelly, P.B.; Nogar, N.S.

    1996-10-01

    We report on aspects of resonant laser ablation (RLA) behavior for a number of sample types: metals, alloys, thin films, zeolites and soil. The versatility of RLA is demonstrated, with results on a variety of samples and in several mass spectrometers. In addition, the application to depth profiling of thin films is described; absolute removal rates and detection limits are also displayed. A discussion of possible mechanisms for low-power ablation is presented.

  20. Percutaneous ablation of colorectal lung metastases

    PubMed Central

    Solomon, Stephen B.

    2015-01-01

    Lung metastasectomy can prolong survival in patients with metastatic colorectal carcinoma. Thermal ablation offers a potential solution with similar reported survival outcomes. It has minimal effect on pulmonary function, or quality of life, can be repeated, and may be considered more acceptable to patients because of the associated shorter hospital stay and recovery. This review describes the indications, technique, reported outcomes, complications and radiologic appearances after thermal ablation of colorectal lung metastases. PMID:26697202

  1. Preparation of GaN Nanostructures by Laser Ablation of ga Metal

    NASA Astrophysics Data System (ADS)

    El Nadi, Lotfia; Omar, Magdy M.; Mehena, Galila A.; Moniem, Hussien M. A.

    2011-06-01

    In the present study, GaN nanodots (0D) and nanowires (1D) nanostructures were prepared on stainless steal substrates applying laser ablation technique. The target of Ga metal mixed with NaNO2 was introduced in a central bore of a graphite rod of a confined geometry set up. The laser beam was normally focused onto the central bore and the ablated plume of Ga metal was deposited on stainless steal substrate lying below the graphite rod in an atmosphere of slow flow of nitrogen gas with or without ammonia vapor. The pulsed N2 laser beam having a wavelength of 337± 2 nm, pulse duration 15±1 ns and energy per pulse of 15±1 m J, could be focused on the central bore by a cylindrical quartz lens to a spot of dimensions 500 × 700 μm2 t providing target irradiance of 0.2-0.3 GW/cm2 per pulse. The ablated plum was collected after several thousand laser shots. The morphology and structure of the formed nanostructures were investigated by Scanning electron microscope and Energy Dispersive X-Ray Spectroscopy. The growth mechanism is most likely by Solid-Liquid-Vapor phase during the laser ablation processes. The role of the carbon, the NaNO2 and the flowing gas on the growth of Nanostructures of GaN are discussed.

  2. Conformal Bulk Ablation And Therapy Monitoring Using Intracorporeal Image-Treat Ultrasound Arrays

    NASA Astrophysics Data System (ADS)

    Makin, I. R.; Faidi, W.; Mast, T. D.; Runk, M.; Slayton, M.; Barthe, P.

    2005-03-01

    For thermal treatment of soft tissue, an alternative to HIFU is bulk ablation using unfocused or weakly focused intense ultrasound fields. This approach offers faster ablation of large tissue volumes and can be performed in minimally invasive (e.g., laparoscopic or percutaneous) procedures. Here, methods for image-guided ablation of large tissue volumes using compact dual-modality (image and treat) ultrasound arrays are reported including tissue modification caused by the thermal therapy. The dual-modality arrays developed have 16-64 elements spanning apertures of 2-8 mm in elevation and 24-48 mm in azimuth. These devices can provide both therapeutically significant power (e.g. source intensity > 80 W/cm2 at 3.1 MHz) and broad bandwidth (e.g. 50% with a center frequency of 3.5 MHz) for imaging. Imaging challenges associated with limited probe dimensions and channel count are met using signal processing techniques that improve definition and contrast, allowing high-quality B-scan images and useful monitoring information to be obtained during therapy planning and treatment. Using linear and rotational scanning methods, large tissue volumes (20-60 cc) can be treated. The approach can be applied for ablation of other soft tissue pathologies, e.g., kidney, heart, uterus, brain, GI tract, etc.

  3. Three-Dimensional Single-Mode Nonlinear Ablative Rayleigh-Taylor Instability

    NASA Astrophysics Data System (ADS)

    Yan, R.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.

    2015-11-01

    The nonlinear evolution of the ablative Rayleigh-Taylor (ART) instability is studied in three dimensions for conditions relevant to inertial confinement fusion targets. The simulations are performed using our newly developed code ART3D and an astrophysical code AstroBEAR. The laser ablation can suppress the growth of the short-wavelength modes in the linear phase but may enhance their growth in the nonlinear phase because of the vortex-acceleration mechanism. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the bubble velocity grows faster than predicted in the classical 3-D theory. When compared to 2-D results, 3-D short-wavelength bubbles grow faster and do not reach saturation. The unbounded 3-D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes into the ablated plasma filling the bubble volume. A density plateau is observed inside a nonlinear ART bubble and the plateau density is higher for shorter-wavelength modes. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  4. Modeling Initial Stage of Ablation Material Pyrolysis: Graphitic Precursor Formation and Interfacial Effects

    NASA Technical Reports Server (NTRS)

    Desai, Tapan G.; Lawson, John W.; Keblinski, Pawel

    2010-01-01

    Reactive molecular dynamics simulations are used to study initial stage of pyrolysis of ablation materials and their composites with carbon nanotubes and carbon fibers. The products formed during pyrolysis are characterized and water is found as the primary product in all cases. The water formation mechanisms are analyzed and the value of the activation energy for water formation is estimated. A detailed study on graphitic precursor formation reveals the presence of two temperature zones. In the lower temperature zone (less than 2000 K) polymerization occurs resulting in formation of large, stable graphitic precursors, and in the high temperature zone (greater than 2000 K) polymer scission results in formation of short polymer chains/molecules. Simulations performed in the high temperature zone on the phenolic resin composites (with carbon nanotubes and carbon fibers) shows that the presence of interfaces had no substantial effect on the chain scission rate or the activation energy value for water formation.

  5. Laser Ablated Carbon Nanodots for Light Emission.

    PubMed

    Reyes, Delfino; Camacho, Marco; Camacho, Miguel; Mayorga, Miguel; Weathers, Duncan; Salamo, Greg; Wang, Zhiming; Neogi, Arup

    2016-12-01

    The synthesis of fluorescent carbon dots-like nanostructures (CNDs) obtained through the laser ablation of a carbon solid target in liquid environment is reported. The ablation process was induced in acetone with laser pulses of 1064, 532, and 355 nm under different irradiation times. Close-spherical amorphous CNDs with sizes between 5 and 20 nm, whose abundance strongly depends on the ablation parameters were investigated using electron microscopy and was confirmed using absorption and emission spectroscopies. The π- π* electronic transition at 3.76 eV dominates the absorption for all the CNDs species synthesized under different irradiation conditions. The light emission is most efficient due to excitation at 3.54 eV with the photoluminescence intensity centered at 3.23 eV. The light emission from the CNDs is most efficient due to ablation at 355 nm. The emission wavelength of the CNDs can be tuned from the near-UV to the green wavelength region by controlling the ablation time and modifying the ablation and excitation laser wavelength.

  6. SonoKnife: Feasibility of a line-focused ultrasound device for thermal ablation therapy

    PubMed Central

    Chen, Duo; Xia, Rongmin; Chen, Xin; Shafirstein, Gal; Corry, Peter M.; Griffin, Robert J.; Penagaricano, Jose A.; Tulunay-Ugur, Ozlem E.; Moros, Eduardo G.

    2011-01-01

    Purpose: To evaluate the feasibility of line-focused ultrasound for thermal ablation of superficially located tumors. Methods: A SonoKnife is a cylindrical-section ultrasound transducer designed to radiate from its concave surface. This geometry generates a line-focus or acoustic edge. The motivation for this approach was the noninvasive thermal ablation of advanced head and neck tumors and positive neck nodes in reasonable treatment times. Line-focusing may offer advantages over the common point-focusing of spherically curved radiators such as faster coverage of a target volume by scanning of the acoustic edge. In this paper, The authors report studies using numerical models and phantom and ex vivo experiments using a SonoKnife prototype. Results: Acoustic edges were generated by cylindrical-section single-element ultrasound transducers numerically, and by the prototype experimentally. Numerically, simulations were performed to characterize the acoustic edge for basic design parameters: transducer dimensions, line-focus depth, frequency, and coupling thickness. The dimensions of the acoustic edge as a function of these parameters were determined. In addition, a step-scanning simulation produced a large thermal lesion in a reasonable treatment time. Experimentally, pressure distributions measured in degassed water agreed well with acoustic simulations, and sonication experiments in gel phantoms and ex vivo porcine liver samples produced lesions similar to those predicted with acoustic and thermal models. Conclusions: Results support the feasibility of noninvasive thermal ablation with a SonoKnife. PMID:21859038

  7. Time-resolved photoluminescence for evaluating laser-induced damage during dielectric stack ablation in silicon solar cells

    NASA Astrophysics Data System (ADS)

    Parola, Stéphanie; Blanc-Pélissier, Danièle; Barbos, Corina; Le Coz, Marine; Poulain, Gilles; Lemiti, Mustapha

    2016-06-01

    Selective laser ablation of dielectric layers on crystalline silicon wafers was investigated for solar cell fabrication. Laser processing was performed on Al2O3, and bi-layers Al2O3/SiNX:H with a nanosecond UV laser at various energy densities ranging from 0.4 to 2 J cm-2. Ablation threshold was correlated to the simulated temperature at the interface between the dielectric coatings and the silicon substrate. Laser-induced damage to the silicon substrate was evaluated by time-resolved photoluminescence. The minority carrier lifetime deduced from time-resolved photoluminescence was related to the depth of the heat affected zone in the substrate.

  8. Photoreduced silver nanoparticles grown on femtosecond laser ablated, D-shaped fiber probe for surface-enhanced Raman scattering.

    PubMed

    Yin, Zhen; Geng, Youfu; Xie, Qingli; Hong, Xueming; Tan, Xiaoling; Chen, Yuzhi; Wang, Lele; Wang, Wenjia; Li, Xuejin

    2016-07-10

    Surface-enhanced Raman scattering (SERS) probes are made by facile photochemical deposition of silver nanoparticles on a femtosecond (fs) laser ablated, D-shaped fiber. The structure and surface morphology of the probe are investigated by scanning electron microscopy. High-quality SERS signals are detected using Rhodamine 6G molecules via an in situ sensing mode. Experimental results show that the SERS signals increase with the increase of the length of fs laser ablated, D-shaped zone. Our D-shaped fiber SERS probe shows a feasible method for a large active area, high performance, and real-time and remote measurement of SERS signals in biochemical analysis.

  9. Bond percolation in higher dimensions

    NASA Astrophysics Data System (ADS)

    Corwin, Eric I.; Stinchcombe, Robin; Thorpe, M. F.

    2013-07-01

    We collect results for bond percolation on various lattices from two to fourteen dimensions that, in the limit of large dimension d or number of neighbors z, smoothly approach a randomly diluted Erdős-Rényi graph. We include results on bond-diluted hypersphere packs in up to nine dimensions, which show the mean coordination, excess kurtosis, and skewness evolving smoothly with dimension towards the Erdős-Rényi limit.

  10. Flying in Two Dimensions

    NASA Astrophysics Data System (ADS)

    Prakash, Manu; Bardon, Thibaut

    2012-11-01

    It has long been proposed that insect flight might have evolved on a fluid interface. Surface of a pond provides an ecological niche which is exploited by a large number of species capable of locomotion on a fluid interface. Here we describe the discovery of constrained flight in two dimensions as a novel mode of locomotion used by water lily beetles (genus Galerucella). Because water lily beetles are also capable of three-dimensional free flight, this novel two-dimensional locomotion provides us with a unique model system to explore both the transition between two and three dimensional flight and the associated energetics. Here we present a comparative analysis of this transition in terms of wing stroke angles associated with two and three dimensional flight, as well as modeling surface tension forces on both the horizontal and vertical axes. Special attention is paid to the dynamics and energetics of flight in two-dimensions, focusing on the interaction of the wing strokes with the fluid interface and the capillary-gravity wave drag associated with two-dimensional propulsion. Current Address: Ecole Polytechnique, France.

  11. Dust ablation in Pluto's atmosphere

    NASA Astrophysics Data System (ADS)

    Horanyi, Mihaly; Poppe, Andrew; Sternovsky, Zoltan

    2016-04-01

    Based on measurements by dust detectors onboard the Pioneer 10/11 and New Horizons spacecraft the total production rate of dust particles born in the Edgeworth Kuiper Belt (EKB) has been be estimated to be on the order of 5 ṡ 103 kg/s in the approximate size range of 1 - 10 μm. Dust particles are produced by collisions between EKB objects and their bombardment by both interplanetary and interstellar dust particles. Dust particles of EKB origin, in general, migrate towards the Sun due to Poynting-Robertson drag but their distributions are further sculpted by mean-motion resonances as they first approach the orbit of Neptune and later the other planets, as well as mutual collisions. Subsequently, Jupiter will eject the vast majority of them before they reach the inner solar system. The expected mass influx into Pluto atmosphere is on the order of 200 kg/day, and the arrival speed of the incoming particles is on the order of 3 - 4 km/s. We have followed the ablation history as function of speed and size of dust particles in Pluto's atmosphere, and found that volatile rich particles can fully sublimate due to drag heating and deposit their mass in narrow layers. This deposition might promote the formation of the haze layers observed by the New Horizons spacecraft. This talk will explore the constraints on the composition of the dust particles by comparing the altitude of the deposition layers to the observed haze layers.

  12. Radiofrequency Ablation Beyond the Liver

    PubMed Central

    Neeman, Ziv; Wood, Bradford J.

    2008-01-01

    Radiofrequency ablation (RFA) has begun to show promise for extrahepatic indications. Although much of the reported work on image-guided RFA of liver neoplasms is quite promising, it is even earlier in the evaluation and validation process for extrahepatic RFA, with few short-term and no long-term studies reported. Although there are much more data for liver RFA with almost 3,000 cases reported in the literature, there are a number of ongoing investigations of RFA for tumors in the kidney, lung, bone, breast, bone, and adrenal gland. Debulking and pain control with RFA present palliative options becoming increasingly popular weapons in the interventionalist's oncology arsenal. Metastatic disease with a wide variety of primary histologies in a myriad of locations may be treated with RFA after a careful consideration of the risk-to-benefit ratio balance. The RFA technique can be slightly different outside the liver. Specifically, differing dielectric tissue characteristics may markedly alter the RFA treatment. Each different RFA system has a unique risk and advantage profile. Extrahepatic indications and contraindications will be suggested. Treatment tips and the unique complications and considerations will be introduced for some of the more common extrahepatic locations. PMID:12524646

  13. Plans and status of the Beryllium ablator campaign on NIF

    NASA Astrophysics Data System (ADS)

    Kline, J. L.; Yi, S. A.; Simakov, A. N.; Wilson, D. C.; Olson, R. E.; Krasheninnikova, N. S.; Kyrala, G. A.; Perry, T. S.; Batha, S. H.; Dewald, E. L.; Edwards, M. J.; MacKinnon, A. J.; Meezan, N. B.

    2014-10-01

    Beryllium has long been known to have excellent properties for indirectly driven ICF implosions including enhanced ablation pressure, implosion velocity, and mass ablation rate. The high ablation velocity leads to stabilization of ablative hydrodynamic instabilities and higher ablation pressures. Recent ``high foot'' experiments have shown ablative Rayleigh-Taylor to be a leading cause of degraded performance for ICF implosions. While Beryllium ablators have these advantages, there are also risks associated with Beryllium target designs. A campaign is underway to design and to test these advantages for comparison with other ablator options and determine which provides the best path forward for ICF. Experiments using Beryllium ablators are expected to start in the late summer of 2014. This presentation will discuss the status of the experiments and layout the plans/goals for the campaign. This work is supported by the US DOE.

  14. Percutaneous Microwave Ablation of Renal Angiomyolipomas

    SciTech Connect

    Cristescu, Mircea; Abel, E. Jason; Wells, Shane Ziemlewicz, Timothy J.; Hedican, Sean P.; Lubner, Megan G. Hinshaw, J. Louis Brace, Christopher L. Lee, Fred T.

    2016-03-15

    PurposeTo evaluate the safety and efficacy of US-guided percutaneous microwave (MW) ablation in the treatment of renal angiomyolipoma (AML).Materials and MethodsFrom January 2011 to April 2014, seven patients (5 females and 2 males; mean age 51.4) with 11 renal AMLs (9 sporadic type and 2 tuberous sclerosis associated) with a mean size of 3.4 ± 0.7 cm (range 2.4–4.9 cm) were treated with high-powered, gas-cooled percutaneous MW ablation under US guidance. Tumoral diameter, volume, and CT/MR enhancement were measured on pre-treatment, immediate post-ablation, and delayed post-ablation imaging. Clinical symptoms and creatinine were assessed on follow-up visits.ResultsAll ablations were technically successful and no major complications were encountered. Mean ablation parameters were ablation power of 65 W (range 60–70 W), using 456 mL of hydrodissection fluid per patient, over 4.7 min (range 3–8 min). Immediate post-ablation imaging demonstrated mean tumor diameter and volume decreases of 1.8 % (3.4–3.3 cm) and 1.7 % (27.5–26.3 cm{sup 3}), respectively. Delayed imaging follow-up obtained at a mean interval of 23.1 months (median 17.6; range 9–47) demonstrated mean tumor diameter and volume decreases of 29 % (3.4–2.4 cm) and 47 % (27.5–12.1 cm{sup 3}), respectively. Tumoral enhancement decreased on immediate post-procedure and delayed imaging by CT/MR parameters, indicating decreased tumor vascularity. No patients required additional intervention and no patients experienced spontaneous bleeding post-ablation.ConclusionOur early experience with high-powered, gas-cooled percutaneous MW ablation demonstrates it to be a safe and effective modality to devascularize and decrease the size of renal AMLs.

  15. A systematic review of surgical ablation versus catheter ablation for atrial fibrillation

    PubMed Central

    Kearney, Katherine; Stephenson, Rowan; Phan, Kevin; Chan, Wei Yen; Huang, Min Yin

    2014-01-01

    Background Atrial fibrillation (AF) is an increasingly prevalent condition in the ageing population, with significantly associated morbidity and mortality. Surgical and catheter ablative strategies both aim to reduce mortality and morbidity through freedom from AF. This review consolidates all currently available comparative data to evaluate these two interventions. Methods A systematic search was conducted across MEDLINE, PubMed, Embase, Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews from January 2000 until August 2013. All studies were critically appraised and only those directly comparing surgical and catheter ablation were included. Results Seven studies were deemed suitable for analysis according to the inclusion criteria. Freedom from AF was significantly higher in the surgical ablation group versus the catheter ablation group at 6-month, 12-month and study endpoint follow-up periods. Subgroup analysis demonstrated similar trends, with higher freedom from AF in the surgical ablation group for paroxysmal AF patients. The incidence of pacemaker implantation was higher, while no difference in stroke or cardiac tamponade was demonstrated for the surgical versus catheter ablation groups. Conclusions Current evidence suggests that epicardial ablative strategies are associated with higher freedom from AF, higher pacemaker implantation rates and comparable neurological complications and cardiac tamponade incidence to catheter ablative treatment. Other complications and risks were poorly reported, which warrants further randomized controlled trials (RCTs) of adequate power and follow-up duration. PMID:24516794

  16. Irreversible Electroporation for the Ablation of Renal Cell Carcinoma: A Prospective, Human, In Vivo Study Protocol (IDEAL Phase 2b)

    PubMed Central

    van Lienden, Krijn P; Wagstaff, Peter GK; Scheltema, Matthijs JV; de Bruin, Daniel M; Zondervan, Patricia J; van Delden, Otto M; van Leeuwen, Ton G; de la Rosette, Jean JMCH; Laguna, M Pilar

    2017-01-01

    Background Irreversible electroporation (IRE) is an emerging technique delivering electrical pulses to ablate tissue, with the theoretical advantage to overcome the main shortcomings of conventional thermal ablation. Recent short-term research showed that IRE for the ablation of renal masses is a safe and feasible treatment option. In an ablate and resect design, histopathological analysis 4 weeks after radical nephrectomy demonstrated that IRE-targeted renal tumors were completely covered by ablation zone. In order to develop a validated long-term IRE follow-up study, it is essential to obtain clinical confirmation of the efficacy of this novel technology. Additionally, follow-up after IRE ablation obliges verification of a suitable imaging modality. Objective The objectives of this study are the clinical efficacy and safety of IRE ablation of renal masses and to evaluate the use of cross-sectional imaging modalities in the follow-up after IRE in renal tumors. This study conforms to the recommendations of the IDEAL Collaboration and can be categorized as a phase 2B exploration trial. Methods In this prospective clinical trial, IRE will be performed in 20 patients aged 18 years and older presenting with a solid enhancing small renal mass (SRM) (≤4 cm) who are candidates for ablation. Magnetic resonance imaging (MRI) and contrast-enhanced ultrasound (CEUS) will be performed at 1 day pre-IRE, and 1 week post-IRE. Computed tomography (CT), CEUS, and MRI will be performed at 3 months, 6 months, and 12 months post-IRE. Results Presently, recruitment of patients has started and the first inclusions are completed. Preliminary results and outcomes are expected in 2018. Conclusions To establish the position of IRE ablation for treating renal tumors, a structured stepwise assessment in clinical practice is required. This study will offer fundamental knowledge on the clinical efficacy of IRE ablation for SRMs, potentially positioning IRE as ablative modality for renal

  17. Online monitoring of nanoparticles formed during nanosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Nováková, Hana; Holá, Markéta; Vojtíšek-Lom, Michal; Ondráček, Jakub; Kanický, Viktor

    2016-11-01

    The particle size distribution of dry aerosol originating from laser ablation of glass material was monitored simultaneously with Laser Ablation - Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis and two aerosol spectrometers - Fast Mobility Particle Sizer (FMPS) and Aerodynamic Particle Sizer (APS). The unique combination of LA-ICP-MS and FMPS offers the possibility of measuring the particle size distribution every 1 s of the ablation process in the size range of 5.6-560 nm. APS extends the information about particle concentration in the size range 0.54-17 μm. Online monitoring of the dry aerosol was performed for two ablation modes (spot and line with a duration of 80 s) with a 193 nm excimer laser system, using the glass reference material NIST 610 as a sample. Different sizes of laser spot for spot ablation and different scan speeds for line ablation were tested. It was found that the FMPS device is capable of detecting changes in particle size distribution at the first pulses of spot laser ablation and is suitable for laser ablation control simultaneously with LA-ICP-MS analysis. The studied parameters of laser ablation have an influence on the resulting particle size distribution. The line mode of laser ablation produces larger particles during the whole ablation process, while spot ablation produces larger particles only at the beginning, during the ablation of the intact layer of the ablated material. Moreover, spot ablation produces more primary nano-particles (in ultrafine mode size range < 100 nm) than line ablation. This effect is most probably caused by a reduced amount of large particles released from the spot ablation crater. The larger particles scavenge the ultrafine particles during the line ablation mode.

  18. Aneurysm-related ischemic ventricular tachycardia: safety and efficacy of catheter ablation

    PubMed Central

    Guo, Jin-Rui; Zheng, Li-Hui; Wu, Ling-Min; Ding, Li-Gang; Yao, Yan

    2017-01-01

    Abstract Left ventricular aneurysm (LVA) postmyocardial infarction (MI) might be an arrhythmogenic substrate. We examined the safety and efficacy of catheter ablation of LVA-related ventricular tachycardia (VT). Thirty-three consecutive patients who underwent primary catheter ablation of ischemic VT were divided into LVA group (11 patients, mean age 61.9 years, 10 men) and none LVA group. Acute procedural outcomes, complications, and long-term outcomes were assessed. In LVA group, average number of induced VTs were 3.2 ± 2.6 (range 1–7), clinical VTs were located in the ventricular septum scar zone in 4 (36.4%) patients, acute success was achieved in 7 (63.6%) patients, partial success in 3 (27.3%) and failure in 1 patient, while none LVA group showing a statistically similar distribution of acute procedural outcomes (P = 0.52). There were no major or life-threatening complications. VT-free survival rate at median 19 (1–44) months follow-up was numerically but not significantly lower in LVA versus none LVA group (48.5% vs 62.8%, log-rank P = 0.40). Catheter ablation of ischemic VT in the presence of LVA appears feasible and effective, with about one-third of cases having septal ablation targets. Further studies are warranted. PMID:28353573

  19. In vitro assessment of fiber sweeping angle during Q-switched 532-nm laser tissue ablation

    NASA Astrophysics Data System (ADS)

    Rajabhandharaks, Danop; Kang, Hyun Wook; Ko, Woo Jin; Stinson, Douglas; Choi, Benjamin

    2011-03-01

    Photoselective vaporization of the prostate (PVP) has been widely used to treat benign prostatic hyperplasia (BPH). It is well regarded as a safe and minimally invasive procedure and an alternative to the gold standard transurethral resection of the prostate (TURP). Despite of its greatness, as well aware of, the operative procedure time during the PVP is still prolonged. Such attempts have been tried out in order to shorten the operative time and increase its efficacy. However, scientific study to investigate techniques used during the PVP is still lacking. The objective of this study is to investigate how sweeping angle might affect the PVP performance. Porcine kidneys acquired from a local grocery store were used (N=140). A Q-switched 532-nm GreenLight XPSTM (American Medical Systems, Inc., MN, USA), together with 750- μm core MoXyTM fiber, was set to have power levels of 120 W and 180 W. Treatment speed and sweeping speed were fixed at 2 mm/s and 0.5 sweep/s, respectively. Sweeping angles were varied from 0 (no sweeping motion) to 120 degree. Ablation rate, depth, and coagulation zone were measured and quantified. Tissue ablation rate was peaked at 15 and 30 degree for both 120- and 180-W power levels and dramatically decreased beyond 60 degree. At 180 W, ablation rate increased 20% at 30 degree compared to 0 degree. This study demonstrated that ablation rate could be maximized and was contingent upon sweeping angle.

  20. Contact pulsed Nd:YAG ablation of human dentin: ablation rates and tissue effects

    NASA Astrophysics Data System (ADS)

    Harris, David M.; Yessik, Michael J.

    1994-09-01

    Dentin from freshly extracted human teeth was exposed to flashlamp pumped Nd:YAG pulses (100 microsecond(s) duration, 50 - 200 mJ/pulse) delivered through a flat cut fiberoptic in contact with the dentin surface. Ablation depth and volume were measured optically and confirmed with electron microscope morphometrics. Ablation depth increased with force applied at the fiber tip up to 5 - 10 g. Above this ablation depths were insensitive to applied force. Craters made in dental stone were deeper and narrower than those made in normal dentin. Ablation depths per pulse and volumes per pulse decrease as the number of pulses increase. This is more prominent for 200 mJ pulses. At 60 mJ the ablation depths are the same from 10 to 100 Hz repetition rates, although qualitative changes (collateral damage) are greater at higher repetition rates. A progressive increase in collateral damage is seen from the 1st through the 200th pulse.

  1. Radioiodine Remnant Ablation: A Critical Review

    PubMed Central

    Bal, Chandra Sekhar; Padhy, Ajit Kumar

    2015-01-01

    Radioiodine remnant ablation (RRA) is considered a safe and effective method for eliminating residual thyroid tissue, as well as microscopic disease if at all present in thyroid bed following thyroidectomy. The rationale of RRA is that in the absence of thyroid tissue, serum thyroglobulin (Tg) measurement can be used as an excellent tumor marker. Other considerations are like the presence of significant remnant thyroid tissue makes detection and treatment of nodal or distant metastases difficult. Rarely, microscopic disease in the thyroid bed if not ablated, in the future, could be a source of anaplastic transformation. On the other hand, microscopic tumor emboli in distant sites could be the cause of distant metastasis too. The ablation of remnant tissue would in all probability eliminate these theoretical risks. It may be noted that all these are unproven contentious issues except postablation serum Tg estimation that could be a good tumor marker for detecting early biochemical recurrence in long-term follow-up strategy. Radioactive iodine is administered as a form of “adjuvant therapy” for remnant ablation. There have been several reports with regard to the administered dose for remnant ablation. The first report of a prospective randomized clinical trial was published from India by a prospective randomized study conducted at the All India Institute of Medical Sciences, New Delhi in the year 1996. The study reported that increasing the empirical 131I initial dose to more than 50 mCi results in plateauing of the dose-response curve and thus, conventional high-dose remnant ablation needs critical evaluation. Recently, two important studies were published: One from French group and the other from UK on a similar line. Interestingly, all three studies conducted in three different geographical regions of the world showed exactly similar conclusion. The new era of low-dose remnant ablation has taken a firm scientific footing across the continents. PMID:26420983

  2. Photoacoustic characterization of radiofrequency ablation lesions

    NASA Astrophysics Data System (ADS)

    Bouchard, Richard; Dana, Nicholas; Di Biase, Luigi; Natale, Andrea; Emelianov, Stanislav

    2012-02-01

    Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh (i.e., never frozen) porcine hearts was harvested within 24 hours of the animals' sacrifice. A THERMOCOOLR Ablation System (Biosense Webster, Inc.) operating at 40 W for 30-60 s was used to induce lesions through the endocardial and epicardial walls of the cardiac samples. Following lesion creation, the ablated tissue samples were placed in 25 °C saline to allow for multi-wavelength PA imaging. Samples were imaged with a VevoR 2100 ultrasound system (VisualSonics, Inc.) using a modified 20-MHz array that could provide laser irradiation to the sample from a pulsed tunable laser (Newport Corp.) to allow for co-registered photoacoustic-ultrasound (PAUS) imaging. PA imaging was conducted from 750-1064 nm, with a surface fluence of approximately 15 mJ/cm2 maintained during imaging. In this preliminary study with PA imaging, the ablated region could be well visualized on the surface of the sample, with contrasts of 6-10 dB achieved at 750 nm. Although imaging penetration depth is a concern, PA imaging shows promise in being able to reliably visualize RF ablation lesions.

  3. Catheter Ablation of Fascicular Ventricular Tachycardia

    PubMed Central

    Liu, Yaowu; Fang, Zhen; Yang, Bing; Kojodjojo, Pipin; Chen, Hongwu; Ju, Weizhu; Cao, Kejiang; Chen, Minglong

    2015-01-01

    Background— Fascicular ventricular tachycardia (FVT) is a common form of sustained idiopathic left ventricular tachycardia with an Asian preponderance. This study aimed to prospectively investigate long-term clinical outcomes of patients undergoing ablation of FVT and identify predictors of arrhythmia recurrence. Methods and Results— Consecutive patients undergoing FVT ablation at a single tertiary center were enrolled. Activation mapping was performed to identify the earliest presystolic Purkinje potential during FVT that was targeted by radiofrequency ablation. Follow-up with clinic visits, ECG, and Holter monitoring was performed at least every 6 months. A total of 120 consecutive patients (mean age, 29.3±12.7 years; 82% men; all patients with normal ejection fraction) were enrolled. FVT involved left posterior fascicle and left anterior fascicle in 118 and 2 subjects, respectively. VT was noninducible in 3 patients, and ablation was acutely successful in 117 patients. With a median follow-up of 55.7 months, VT of a similar ECG morphology recurred in 17 patients, and repeat procedure confirmed FVT recurrence involving the same fascicle. Shorter VT cycle length was the only significant predictor of FVT recurrence (P=0.03). Six other patients developed new-onset upper septal FVT that was successfully ablated. Conclusions— Ablation of FVT guided by activation mapping is associated with a single procedural success rate without the use of antiarrhythmic drugs of 80.3%. Arrhythmia recurrences after an initially successful ablation were caused by recurrent FVT involving the same fascicle in two thirds of patients or new onset of upper septal FVT in the remainder. PMID:26386017

  4. Acoustic emissions during 3.1 MHz ultrasound bulk ablation in vitro.

    PubMed

    Mast, T Douglas; Salgaonkar, Vasant A; Karunakaran, Chandrapriya; Besse, John A; Datta, Saurabh; Holland, Christy K

    2008-09-01

    Acoustic emissions associated with cavitation and other bubble activity have previously been observed during ultrasound (US) ablation experiments. Because detectable bubble activity may be related to temperature, tissue state and sonication characteristics, these acoustic emissions are potentially useful for monitoring and control of US ablation. To investigate these relationships, US ablation experiments were performed with simultaneous measurements of acoustic emissions, tissue echogenicity and tissue temperature on fresh bovine liver. Ex vivo tissue was exposed to 0.9-3.3-s bursts of unfocused, continuous-wave, 3.10-MHz US from a miniaturized 32-element array, which performed B-scan imaging with the same piezoelectric elements during brief quiescent periods. Exposures used pressure amplitudes of 0.8-1.4 MPa for exposure times of 6-20 min, sufficient to achieve significant thermal coagulation in all cases. Acoustic emissions received by a 1-MHz, unfocused passive cavitation detector, beamformed A-line signals acquired by the array, and tissue temperature detected by a needle thermocouple were sampled 0.3-1.1 times per second. Tissue echogenicity was quantified by the backscattered echo energy from a fixed region-of-interest within the treated zone. Acoustic emission levels were quantified from the spectra of signals measured by the passive cavitation detector, including subharmonic signal components at 1.55 MHz, broadband signal components within the band 0.3-1.1 MHz and low-frequency components within the band 10-30 kHz. Tissue ablation rates, defined as the thermally ablated volumes per unit time, were assessed by quantitative analysis of digitally imaged, macroscopic tissue sections. Correlation analysis was performed among the averaged and time-dependent acoustic emissions in each band considered, B-mode tissue echogenicity, tissue temperature and ablation rate. Ablation rate correlated significantly with broadband and low-frequency emissions, but was

  5. FRACTAL DIMENSION OF GALAXY ISOPHOTES

    SciTech Connect

    Thanki, Sandip; Rhee, George; Lepp, Stephen E-mail: grhee@physics.unlv.edu

    2009-09-15

    In this paper we investigate the use of the fractal dimension of galaxy isophotes in galaxy classification. We have applied two different methods for determining fractal dimensions to the isophotes of elliptical and spiral galaxies derived from CCD images. We conclude that fractal dimension alone is not a reliable tool but that combined with other parameters in a neural net algorithm the fractal dimension could be of use. In particular, we have used three parameters to segregate the ellipticals and lenticulars from the spiral galaxies in our sample. These three parameters are the correlation fractal dimension D {sub corr}, the difference between the correlation fractal dimension and the capacity fractal dimension D {sub corr} - D {sub cap}, and, thirdly, the B - V color of the galaxy.

  6. Subsurface ablation of atherosclerotic plaque using ultrafast laser pulses

    PubMed Central

    Lanvin, Thomas; Conkey, Donald B.; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-01-01

    We perform subsurface ablation of atherosclerotic plaque using ultrafast pulses. Excised mouse aortas containing atherosclerotic plaque were ablated with ultrafast near-infrared (NIR) laser pulses. Optical coherence tomography (OCT) was used to observe the ablation result, while the physical damage was inspected in histological sections. We characterize the effects of incident pulse energy on surface damage, ablation hole size, and filament propagation. We find that it is possible to ablate plaque just below the surface without causing surface damage, which motivates further investigation of ultrafast ablation for subsurface atherosclerotic plaque removal. PMID:26203381

  7. Subsurface ablation of atherosclerotic plaque using ultrafast laser pulses.

    PubMed

    Lanvin, Thomas; Conkey, Donald B; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-07-01

    We perform subsurface ablation of atherosclerotic plaque using ultrafast pulses. Excised mouse aortas containing atherosclerotic plaque were ablated with ultrafast near-infrared (NIR) laser pulses. Optical coherence tomography (OCT) was used to observe the ablation result, while the physical damage was inspected in histological sections. We characterize the effects of incident pulse energy on surface damage, ablation hole size, and filament propagation. We find that it is possible to ablate plaque just below the surface without causing surface damage, which motivates further investigation of ultrafast ablation for subsurface atherosclerotic plaque removal.

  8. New tumor ablation techniques for cancer treatment (microwave, electroporation).

    PubMed

    de Baere, T; Deschamps, F

    2014-01-01

    Since the introduction of radiofrequency ablation (RFA) for the treatment of liver tumors at the end of the 1990s, indications for local ablation techniques have been extended to other organs, in particular, the lungs, kidneys and bones. These techniques have also been improved, in particular to try and overcome the limitations of radiofrequency techniques, especially the significant decrease in complete ablation rates for tumors larger than 3cm and tumors that are contiguous to vessels larger than 3mm. Microwave ablation is a rapidly developing thermal ablation technique similar to RFA but with numerous differences. Electroporation, a non-thermal ablation technique with other possibilities, is in earlier stages of clinical development.

  9. Health-related quality of life in different clinical subgroups with typical AFL who have undergone cavo-tricuspid isthmus ablation

    PubMed Central

    2012-01-01

    Background To evaluate changes in health-related quality of life (HRQOL) in different sub-groups of a cohort of patients with typical atrial flutter (AFL) treated with cavotricuspid isthmus (CTI) radiofrequency catheter ablation. Methods 95 consecutive patients due to undergo CTI ablation were enrolled in a study involving their completion of two SF-36 HRQOL questionnaires, before ablation and at one-year follow-up. Results 88 of the initial 95 patients finished the study. Regardless of whether patients experienced atrial fibrillation (AF) during follow-up, a statistically significant improvement in HRQOL was observed, compared with pre-ablation scores and in all dimensions except Bodily Pain. However, patients without AF during follow-up had significantly higher absolute HRQOL scores in most dimensions. No differences were seen in most HRQOL dimensions, with respect to AFL type (paroxysmal, persistent) or duration, whether AFL was first-episode or recurrent, Class I-III drug dependent, sex, or presence of structural heart disease or tachycardiomyopathy. Patients with persistent AFL showed the greatest improvement in HRQOL when they also had a ventricular cycle length ≤500 ms. The combination of recurrent AFL, ventricular cycle length ≤500 ms and structural heart disease led to a significantly greater improvement in physical HRQOL dimensions than did first-episode AFL, no structural heart disease and ventricular cycle >500 ms. The only independent factor associated with a greater improvement was structural cardiopathy. Conclusions CTI-ablation treatment leads to a significant improvement in HRQOL in patients with typical AFL. Patients with AF during follow-up show a significantly lower HRQOL at one-year post-ablation. The only independent risk factor found to be associated with a greater improvement in the physical summary component was structural cardiopathy. PMID:22866671

  10. Action languages: Dimensions, effects

    NASA Technical Reports Server (NTRS)

    Hayes, Daniel G.; Streeter, Gordon

    1989-01-01

    Dimensions of action languages are discussed for communication between humans and machines, and the message handling capabilities of object oriented programming systems are examined. Design of action languages is seen to be very contextual. Economical and effective design will depend on features of situations, the tasks intended to be accomplished, and the nature of the devices themselves. Current object oriented systems turn out to have fairly simple and straightforward message handling facilities, which in themselves do little to buffer action or even in some cases to handle competing messages. Even so, it is possible to program a certain amount of discretion about how they react to messages. Such thoughtfulness and perhaps relative autonomy of program modules seems prerequisite to future systems to handle complex interactions in changing situations.

  11. Approximate model for laser ablation of carbon

    NASA Astrophysics Data System (ADS)

    Shusser, Michael

    2010-08-01

    The paper presents an approximate kinetic theory model of ablation of carbon by a nanosecond laser pulse. The model approximates the process as sublimation and combines conduction heat transfer in the target with the gas dynamics of the ablated plume which are coupled through the boundary conditions at the interface. The ablated mass flux and the temperature of the ablating material are obtained from the assumption that the ablation rate is restricted by the kinetic theory limitation on the maximum mass flux that can be attained in a phase-change process. To account for non-uniform distribution of the laser intensity while keeping the calculation simple the quasi-one-dimensional approximation is used in both gas and solid phases. The results are compared with the predictions of the exact axisymmetric model that uses the conservation relations at the interface derived from the momentum solution of the Boltzmann equation for arbitrary strong evaporation. It is seen that the simpler approximate model provides good accuracy.

  12. Design Calculations for NIF Convergent Ablator Experiments

    NASA Astrophysics Data System (ADS)

    Olson, R. E.; Callahan, D. A.; Hicks, D. G.; Landen, O. L.; Langer, S. H.; Meezan, N. B.; Spears, B. K.; Widmann, K.; Kline, J. L.; Wilson, D. C.; Petrasso, R. D.; Leeper, R. J.

    2010-11-01

    Design calculations for NIF convergent ablator experiments will be described. The convergent ablator experiments measure the implosion trajectory, velocity, and ablation rate of an x-ray driven capsule and are a important component of the U. S. National Ignition Campaign at NIF. The design calculations are post-processed to provide simulations of the key diagnostics -- 1) Dante measurements of hohlraum x-ray flux and spectrum, 2) streaked radiographs of the imploding ablator shell, 3) wedge range filter measurements of D-He3 proton output spectra, and 4) GXD measurements of the imploded core. The simulated diagnostics will be compared to the experimental measurements to provide an assessment of the accuracy of the design code predictions of hohlraum radiation temperature, capsule ablation rate, implosion velocity, shock flash areal density, and x-ray bang time. Post-shot versions of the design calculations are used to enhance the understanding of the experimental measurements and will assist in choosing parameters for subsequent shots and the path towards optimal ignition capsule tuning. *SNL, LLNL, and LANL are operated under US DOE contracts DE-AC04-94AL85000. DE-AC52-07NA27344, and DE-AC04-94AL85000.

  13. Fracture in Phenolic Impregnated Carbon Ablator

    NASA Technical Reports Server (NTRS)

    Agrawal, Parul; Chavez-Garcia, Jose; Pham, John

    2013-01-01

    This paper describes the development of a novel technique to understand the failure mechanisms inside thermal protection materials. The focus of this research is on the class of materials known as phenolic impregnated carbon ablators. It has successfully flown on the Stardust spacecraft and is the thermal protection system material chosen for the Mars Science Laboratory and SpaceX Dragon spacecraft. Although it has good thermal properties, structurally, it is a weak material. To understand failure mechanisms in carbon ablators, fracture tests were performed on FiberForm(Registered TradeMark) (precursor), virgin, and charred ablator materials. Several samples of these materials were tested to investigate failure mechanisms at a microstructural scale. Stress-strain data were obtained simultaneously to estimate the tensile strength and toughness. It was observed that cracks initiated and grew in the FiberForm when a critical stress limit was reached such that the carbon fibers separated from the binder. However, both for virgin and charred carbon ablators, crack initiation and growth occurred in the matrix (phenolic) phase. Both virgin and charred carbon ablators showed greater strength values compared with FiberForm samples, confirming that the presence of the porous matrix helps in absorbing the fracture energy.

  14. Test of Thermal Transport Models through Dynamic Overpressure Stabilization of Ablation-Front Perturbation Growth in Laser-Driven CH Foils

    SciTech Connect

    Gotchev, O.V.; Goncharov, V.N.; Knauer, J.P.; Boehly, T.R.; Collins, T.J.B.; Epstein, R.; Jaanimagi, P.A.; Meyerhofer, D.D.

    2006-03-24

    Heat-flow-induced dynamic overpressure at the perturbed ablation front of an ICF target can stabilize the ablative Richtmyer/Meshkov-like instability and mitigate the subsequent ablative Rayleigh/Taylor (RT) instability. A series of experiments was performed on the OMEGA laser to quantify the dynamic overpressure stabilization during the shock transit. Analysis of the experimental data using hydrocode simulations shows that the observed oscillatory evolution of the ablation-front perturbations depends on Dc, the size of the thermal conduction zone, and the fluid velocity in the blowoff region Vbl that are sensitive to the thermal transport model used. We show that the simulations match the experiment well when the time dependence of the heat-flux inhibition is taken into account using a recently developed nonlocal heat transport model.

  15. Dental ablation with 1064 nm, 500 ps, Diode pumped solid state laser: A preliminary study

    PubMed Central

    Fornaini, Carlo; Cucinotta, Annamaria; Merigo, Elisabetta; Vescovi, Paolo; Selleri, Stefano

    2013-01-01

    Background: The Er:YAG laser in conservative dentistry is. good alternative to conventional instruments. Though several studies show the advantages of these devices, some drawbacks and unsolved problems are still present, such as the cost of the device and the large dimensions of the equipment. Purpose: In the present study, the effectiveness of dental surface ablation with a picosecond infrared diode-pumped solid-state (DPSS) laser was investigated. In vitro tests on extracted human teeth were carried out, with assessment of the ablation quality in the tooth and thermal increase inside the pulp chamber. Materials and Methods: A solid-state picosecond laser was used for the experiments. The samples were exposed to laser energy at 1064 nm at a frequency of 30 kHz and a 500 ps pulse width. The target teeth were cooled during exposures. The internal temperature of the pulp chamber was monitored with. thermocouple. Results: Optical microscope images showed effective ablation with the absence of carbonisation and micro-cracks. The cooling maintained the temperature rise in the pulp chamber below the permitted 5.5°C. Discussion: The main problem with the use of lasers in dentistry when teeth are the target is the heat generated in the pulp chamber of the target teeth. With lasers operating in the femtosecond mode, a better management of the internal temperature is possible, but is offset by the high cost of such devices. With the ps domain system used in the present study together with cooling using chilled water, effective and clean ablation could be achieved with a controlled thermal effect in the pulp chamber. Conclusions: In this preliminary study with a picosecond domain DPSS laser using water cooling for the target, effective hard tissue ablation was achieved keeping the thermal increase in the pulp within the permitted range. The results suggest that this system could be used in clinical practice with appropriate modifications. PMID:24204093

  16. Knowledge-based flow field zoning

    NASA Technical Reports Server (NTRS)

    Andrews, Alison E.

    1988-01-01

    Automation flow field zoning in two dimensions is an important step towards easing the three-dimensional grid generation bottleneck in computational fluid dynamics. A knowledge based approach works well, but certain aspects of flow field zoning make the use of such an approach challenging. A knowledge based flow field zoner, called EZGrid, was implemented and tested on representative two-dimensional aerodynamic configurations. Results are shown which illustrate the way in which EZGrid incorporates the effects of physics, shape description, position, and user bias in a flow field zoning.

  17. The Stereo-Electroencephalography: The Epileptogenic Zone.

    PubMed

    Gonzalez-Martinez, Jorge A

    2016-12-01

    The stereo-electroencephalography (SEEG) methodology and technique was developed almost 60 years ago in Europe and it has proven its efficacy and safety over the last 55 years. The main advantage of the SEEG method is the possibility to study the epileptogenic neuronal network in its dynamic and tri-dimensional aspect, with an optimal time and space correlation with the clinical semiology. In this manuscript, the technical and methodological aspects of the SEEG will be discussed focusing on the planning of SEEG implantations, technical nuances, conceptualization of the epileptogenic zone, and the different methods of SEEG-guided surgical resections and ablations.

  18. Heat sink effect on tumor ablation characteristics as observed in monopolar radiofrequency, bipolar radiofrequency, and microwave, using ex vivo calf liver model.

    PubMed

    Pillai, Krishna; Akhter, Javid; Chua, Terence C; Shehata, Mena; Alzahrani, Nayef; Al-Alem, Issan; Morris, David L

    2015-03-01

    Thermal ablation of liver tumors near large blood vessels is affected by the cooling effect of blood flow, leading to incomplete ablation. Hence, we conducted a comparative investigation of heat sink effect in monopolar (MP) and bipolar (BP) radiofrequency ablation (RFA), and microwave (MW) ablation devices.With a perfused calf liver, the ablative performances (volume, mass, density, dimensions), with and without heat sink, were measured. Heat sink was present when the ablative tip of the probes were 8.0 mm close to a major hepatic vein and absent when >30 mm away. Temperatures (T1 and T2) on either side of the hepatic vein near the tip of the probes, heating probe temperature (T3), outlet perfusate temperature (T4), and ablation time were monitored.With or without heat sink, BP radiofrequency ablated a larger volume and mass, compared with MP RFA or MW ablation, with latter device producing the highest density of tissue ablated. MW ablation produced an ellipsoidal shape while radiofrequency devices produced spheres.Percentage heat sink effect in Bipolar radiofrequency : Mono-polar radiofrequency : Microwave was (Volume) 33:41:22; (mass) 23:56:34; (density) 9.0:26:18; and (relative elipscity) 5.8:12.9:1.3, indicating that BP and MW devices were less affected.Percentage heat sink effect on time (minutes) to reach maximum temperature (W) = 13.28:9.2:29.8; time at maximum temperature (X) is 87:66:16.66; temperature difference (Y) between the thermal probes (T3) and the temperature (T1 + T2)/2 on either side of the hepatic vessel was 100:87:20; and temperature difference between the (T1 + T2)/2 and temperature of outlet circulating solution (T4), Z was 20.33:30.23:37.5.MW and BP radiofrequencies were less affected by heat sink while MP RFA was the most affected. With a single ablation, BP radiofrequency ablated a larger volume and mass regardless of heat sink.

  19. Effect of variable heat transfer coefficient on tissue temperature next to a large vessel during radiofrequency tumor ablation

    PubMed Central

    dos Santos, Icaro; Haemmerich, Dieter; Pinheiro, Cleber da Silva; da Rocha, Adson Ferreira

    2008-01-01

    Background One of the current shortcomings of radiofrequency (RF) tumor ablation is its limited performance in regions close to large blood vessels, resulting in high recurrence rates at these locations. Computer models have been used to determine tissue temperatures during tumor ablation procedures. To simulate large vessels, either constant wall temperature or constant convective heat transfer coefficient (h) have been assumed at the vessel surface to simulate convection. However, the actual distribution of the temperature on the vessel wall is non-uniform and time-varying, and this feature makes the convective coefficient variable. Methods This paper presents a realistic time-varying model in which h is a function of the temperature distribution at the vessel wall. The finite-element method (FEM) was employed in order to model RF hepatic ablation. Two geometrical configurations were investigated. The RF electrode was placed at distances of 1 and 5 mm from a large vessel (10 mm diameter). Results When the ablation procedure takes longer than 1–2 min, the attained coagulation zone obtained with both time-varying h and constant h does not differ significantly. However, for short duration ablation (5–10 s) and when the electrode is 1 mm away from the vessel, the use of constant h can lead to errors as high as 20% in the estimation of the coagulation zone. Conclusion For tumor ablation procedures typically lasting at least 5 min, this study shows that modeling the heat sink effect of large vessels by applying constant h as a boundary condition will yield precise results while reducing computational complexity. However, for other thermal therapies with shorter treatment using a time-varying h may be necessary. PMID:18620566

  20. FED. Zoning for TRUMP Heat Transfer Code

    SciTech Connect

    Elrod, D.

    1987-10-23

    FED reduces the effort required to obtain the necessary geometric input for problems which are to be solved using the heat-transfer code, TRUMP. TRUMP calculates transient and steady-state temperature distributions in multidimensional systems. FED can properly zone any body of revolution in one, two, or three dimensions.

  1. Body Buffer Zone and Proxemics in Blocking.

    ERIC Educational Resources Information Center

    Stockwell, John C.; Bahs, Clarence W.

    This paper investigates the effect of personal body buffer zones on compositional arrangements staged by novice directors. Relationships between directors' concepts of personal space and their projection of its dimensions into staging are studied through the use of a variety of proximity measures--distance, area angles of approach, and physical…

  2. The Dimension of Information

    NASA Astrophysics Data System (ADS)

    Preuss, Lucien

    2008-11-01

    To implement Jaynes' vision [1] of applications of Shannon's ideas outside Communication Theory proper, the dimension of information must be clarified, mainly because general applications provide no ready-made set of discrete, mutually exclusive and exhaustive "events" which could play a rôle similar to that of the alphabet which communication theory implicitely supposes known from the outset. For instance, a doctor's "alphabet" may be said to consist of readily distinguishable bundles of symptoms, cures, etc., each of which he considers specific enough to describe an illness of interest. Setting up an appropriate alphabet requires learning, in the same way as a child painfully learns to read letters, and a quantitative assessment of this task depends crucially on the dimension of information. Information is an extensive property, as explicited by the standard equation I = N.H for the amount of information delivered by a succession of N events. All other things remaining equal, doubling the length of a message doubles the amount of information. But by definition, Shannon's uncertainty H on the right-hand side of the equation is a rate, i.e. an intensive property, as illustrated by the fact that the simultaneous throw of two true and identical dice removes less than twice the uncertainty removed by the throw of a single die, as is well-known to poker-players. If the above equation is to be dimensionally consistent, N can not be a pure number, but must have an extensive dimension of its own. The obvious question "which?" was swept under the rug by von Neumann's famous quip [3], which advised to call H an entropy, thereby suggesting improperly that H by itself-without the factor N-is an extensive property like physical entropy. But H only evaluates an amount of information when multiplied by N, which measures an amount of order akin to the chronological order without which any message becomes garbage. In analogy with the decomposition E S.T of energy E into the pair

  3. Microwave ablation versus laser ablation in occluding lateral veins in goats.

    PubMed

    Wang, Xu-hong; Wang, Xiao-ping; Su, Wen-juan; Yuan, Yuan

    2016-02-01

    Increasing number of endovenous techniques are available for the treatment of saphenous vein reflux and endovenous laser ablation (EVLA) is a frequently used method. A newly developed alternative, based on thermal therapy, is endovenous microwave ablation (EMA). This study evaluated the effect of the two procedures, in terms of coagulation and histological changes, in occluding lateral veins in goats. Twelve animals were randomized into two group, with 6 treated with EMA (EMA group), and the rest 6 with EVLA (EVLA group). Results of coagulation, including coagulation, fibrinolysis and platelet activation, were assessed at three or four different time points: before, immediately after, 24 h (and 48 h) after ablation. The diameter change, a measure of efficacy, was ultrasonographically measured before and 1 month after the ablation. Histological changes were grossly and microscopically evaluated immediately, 1 and 3 month(s) after the ablation. The length of the ablated vein and preoperative average diameter were comparable between the two groups. In both EMA and EVLA groups, several coagulation parameters, fibrinolysis and platelet activation parameters only underwent slight changes. Ultrasound imaging displayed that the diameter reduction of the veins treated by EMA was significantly larger than by EVLA, in consistent with the results of macroscopic examination. Microscopic examination revealed necrosis and thickening of the vein wall, and occlusion of the lumen within 3 months after ablation in both EMA and EVLA groups. It is concluded that EMA is a minimally invasive therapy, which appears to be safe and effective for treatment of lateral veins in goats.

  4. Effects of material composition on the ablation performance of low density elastomeric ablators

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.; Kabana, W. P.

    1973-01-01

    The ablation performance of materials composed of various concentrations of nylon, hollow silica spheres, hollow phenolic spheres, and four elastomeric resins was determined. Both blunt-body and flat-panel specimens were used, the cold-wall heating-rate ranges being 0.11 to 0.8 MW/sq m, respectively. The corresponding surface pressure ranges for these tests were 0.017 to 0.037 atmosphere and 0.004 to 0.005 atmosphere. Some of the results show that (1) the addition of nylon significantly improved the ablation performance, but the nylon was not compatible with one resin system; (2) panel and blunt-body specimen data do not show the same effect of phenolic sphere content on ablation effectiveness; and (3) there appears to be an optimum concentration of hollow silica spheres for good ablation performance. The composition of an efficient, nonproprietary ablator for lifting body application is identified and the ablation performance of this ablator is compared with the performance of three commercially available materials.

  5. Evaluation of corneal ablation by an optical parametric oscillator (OPO) at 2.94 μm and an Er:YAG laser and comparison to ablation by a 193-nm excimer laser

    NASA Astrophysics Data System (ADS)

    Telfair, William B.; Hoffman, Hanna J.; Nordquist, Robert E.; Eiferman, Richard A.

    1998-06-01

    Purpose: This study first evaluated the corneal ablation characteristics of (1) an Nd:YAG pumped OPO (Optical Parametric Oscillator) at 2.94 microns and (2) a short pulse Er:YAG laser. Secondly, it compared the histopathology and surface quality of these ablations with (3) a 193 nm excimer laser. Finally, the healing characteristics over 4 months of cat eyes treated with the OPO were evaluated. Methods: Custom designed Nd:YAG/OPO and Er:YAG lasers were integrated with a new scanning delivery system to perform PRK myopic correction procedures. After initial ablation studies to determine ablation thresholds and rates, human cadaver eyes and in-vivo cat eyes were treated with (1) a 6.0 mm Dia, 30 micron deep PTK ablation and (2) a 6.0 mm Dia, -5.0 Diopter PRK ablation. Cadaver eyes were also treated with a 5.0 mm Dia, -5.0 Diopter LASIK ablation. Finally, cats were treated with the OPO in a 4 month healing study. Results: Ablation thresholds below 100 mJ/cm2 and ablation rates comparable to the excimer were demonstrated for both infrared systems. Light Microscopy (LM) showed no thermal damage for low fluence treatments, but noticeable thermal damage at higher fluences. SEM and TEM revealed morphologically similar surfaces for low fluence OPO and excimer samples with a smooth base and no evidence of collagen shrinkage. The Er:YAG and higher fluence OPO treated samples revealed more damage along with visible collagen coagulation and shrinkage in some cases. Healing was remarkably unremarkable. All eyes had a mild healing response with no stromal haze and showed topographic flattening. LM demonstrated nothing except a moderate increase in keratocyte activity in the upper third of the stroma. TEM confirmed this along with irregular basement membranes. Conclusions: A non- thermal ablation process called photospallation is demonstrated for the first time using short pulse infrared lasers yielding damage zones comparable to the excimer and healing which is also comparable to

  6. 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).

  7. Deep Dive Topic: Choosing between ablators

    SciTech Connect

    Hurricane, O. A.; Thomas, C.; Olson, R.

    2015-07-14

    Recent data on implosions using identical hohlraums and very similar laser drives underscores the conundrum of making a clear choice of one ablator over another. Table I shows a comparison of Be and CH in a nominal length, gold, 575 μm-diameter, 1.6 mg/cc He gas-fill hohlraum while Table II shows a comparison of undoped HDC and CH in a +700 length, gold, 575 μm diameter, 1.6 mg/cc He gas fill hohlraum. As can be seen in the tables, the net integrated fusion performance of these ablators is the same to within error bars. In the case of the undoped HDC and CH ablators, the hot spot shapes of the implosions were nearly indistinguishable for the experiments listed in Table II.

  8. Numerical Modeling of Ablation Heat Transfer

    NASA Technical Reports Server (NTRS)

    Ewing, Mark E.; Laker, Travis S.; Walker, David T.

    2013-01-01

    A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.

  9. Optically thick ablation fronts. [in interstellar medium

    NASA Technical Reports Server (NTRS)

    Konigl, A.

    1984-01-01

    The physical characteristics of optically thick ablation fronts such as interstellar clouds are analyzed. Attention is given to cold clumps in both planar and spherical geometries and modifications caused by accelerations in a gravitational field or by evaporation of the clumps when encountered hot gas. The effects of ablation on the appearance of the Rayleigh-Taylor instability are examined in both linear and nonlinear regimes. The results of the calculations are applied to the astrophysical phenomena of cold clumps immersed in a supersonic flow, optically thick jets, and ablation in stellar envelopes. Evaporation in an optically thick front is projected to be orders of magnitude larger than evaporation in electron-conduction fronts in optically thin conditions. The optically thick processes could then be useful for modeling flows from, e.g., newly formed stars and active galactic nuclei.

  10. Laser ablated hard coating for microtools

    DOEpatents

    McLean, W. II; Balooch, M.; Siekhaus, W.J.

    1998-05-05

    Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10--20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode. 12 figs.

  11. Specific Impulse Definition for Ablative Laser Propulsion

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Gregory, Don A.

    2004-01-01

    The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

  12. Caries-selective ablation: the second threshold

    NASA Astrophysics Data System (ADS)

    Hennig, Thomas; Rechmann, Peter; Jeitner, Peter; Kaufmann, Raimund

    1993-07-01

    The aim of the study was to describe the appropriate fluence necessary for the effective removal of dental decay by ablation processes without or with at least minimal removal of healthy dentin. The experiments were conducted at two wavelengths [355 nm (frequency tripled, Q-switched Nd:YAG-laser) and 377 nm (frequency doubled, gain-switched Alexandrite-laser)] found to be close to the maximum of preferential absorption of carious dentin over healthy dentin. Optoacoustic techniques were applied to determine the ablation thresholds of healthy and carious dentin. The ablation efficiencies at characteristic fluences were determined using non-tactile microtopography. During all experiments a fiber optic delivery system was engaged.

  13. 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.

  14. Laser ablated hard coating for microtools

    DOEpatents

    McLean, II, William; Balooch, Mehdi; Siekhaus, Wigbert J.

    1998-05-05

    Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

  15. Effects of endocardial microwave energy ablation

    PubMed Central

    Climent, Vicente; Hurlé, Aquilino; Ho, Siew Yen; Sánchez-Quintana, Damián

    2005-01-01

    Until recently the treatment of atrial fibrillation (AF) consisted primarily of palliation, mostly in the form of pharmacological intervention. However because of recent advances in nonpharmacologic therapies, the current expectation of patients and referring physicians is that AF will be cured, rather than palliated. In recent years there has been a rapid expansion in the availability and variety of energy sources and devices for ablation. One of these energies, microwave, has been applied clinically only in the last few years, and may be a promising technique that is potentially capable of treating a wide range of ventricular and supraventricular arrhythmias. The purpose of this study was to review microwave energy ablation in surgical treatment of AF with special interest in histology and ultrastructure of lesions produced by this endocardial ablation procedure. PMID:16943871

  16. Laser Thermal Ablation of Thyroid Benign Nodules

    PubMed Central

    Shahrzad, Mohammad Karim

    2015-01-01

    Thermal ablation therapies for benign thyroid nodules have been introduced in recent years to avoid the complications of traditional methods such as surgery. Despite the little complications and the reportedly acceptable efficacy of thermal ablation methods, quite few medical centers have sought the potential benefits of employing them. This paper provides an introduction to the literature, principles and advances of Percutaneous Laser Ablation therapy of thyroid benign nodules, as well as a discussion on its efficacy, complications and future. Several clinical research papers evaluating the thermal effect of laser on the alleviation of thyroid nodules have been reviewed to illuminate the important points. The results of this research can help researchers to advance the approach and medical centers to decide on investing in these novel therapies. PMID:26705459

  17. Thermal Response Simulation of Ultra Light Weight Phenolic Carbon Ablator by the Use of the Ablation Analysis Code

    NASA Astrophysics Data System (ADS)

    Kato, Sumio; Okuyama, Keiichi; Gibo, Kenta; Miyagi, Takuma; Suzuki, Toshiyuki; Fujita, Kazuhisa; Sakai, Takeharu; Nishio, Seiji; Watanabe, Akihiro

    A space vehicle which undergoes the atmospheric re-entry or a planetary entry needs the heat shield system to protect inner equipments against severe aerodynamic heating environments. Charring ablator is usually used for the heat shield system. In order to design the heat shield system, it is necessary to predict the thermal behavior under aerodynamic heating by ablation analysis. A computer code for charring ablation and thermal response analysis is newly developed for simulation of one-dimensional transient thermal behavior of charring ablation materials. The mathematical model for the charring ablation including basic equation and computational method of ablation analysis is briefly described. A new ultra light weight phenolic carbon ablator called LATS (Lightweight Ablator series for Transfer vehicle) was recently developed. Arc-heated tests of the LATS ablator were carried out and measured results of the temperature response and surface mass loss are compared with the simulation results of the ablation analysis program. The agreement between the results of simulation and measurement is found to be good. It is also found that the mathematical model used in the ablation code can be applied to the ablation analysis of the low density LATS ablator.

  18. Depth Profiling of Polymer Composites by Ultrafast Laser Ablation

    NASA Astrophysics Data System (ADS)

    Young, Christopher; Clayton, Clive; Longtin, Jon

    2009-03-01

    Past work has shown femtosecond laser ablation to be an athermal process at low fluences in polymer systems. The ablation rate in this low fluence regime is very low, allowing for micro-scale removal of material. We have taken advantage of this fact to perform shallow depth profiling ablation on carbon fiber reinforced polymer (CFRP) composites. Neat composite and resin samples were studied to establish reference ablation profiles. These profiles and the effects of the heterogeneous distribution of carbon fibers were observed through confocal laser profilometry and optical and scanning electron microscopy. Weathered materials that have been subjected to accelerated tests in artificial sunlight or water conditions were ablated to determine the correlation between exposure and change in ablation characteristics. Preliminary Raman and micro-ATR analysis performed before and after ablation shows no chemical changes indicative of thermal effects. The low-volume-ablation property was utilized in an attempt to expose the sizing-matrix interphase for analysis.

  19. Scientific Visualization of Extra Dimensions

    NASA Astrophysics Data System (ADS)

    Black, Don V.

    2010-10-01

    In the 21st Century, many theoretical physicists claim that higher dimensions may indeed exist. Arkani-Hamed, Dimopoulos, & Dvali (ADD) and Randall-Sundrum (RS), in addition to Kaluza-Klein (KK) and M-string theorists, have introduced reasonable explanations for the existence of heretofore ``invisible'' higher dimensions. Whether or not these extra dimensions actually exist is irrelevant to their contributions to the visionary conceptualization associated with novel and improved mathematical and physical analysis. Envisioning extra dimensions beyond the three of common experience is a daunting challenge for three dimensional observers. Intuition relies on experience gained in a three dimensional environment. Gaining experience with virtual four dimensional objects and virtual three manifolds in four-space on a personal computer may provide the basis for an intuitive grasp of four dimensions. This presentation is a video ``outtake'' of the author's research into ``Visualizing Extra Spatial Dimensions'' at the University of California at Irvine.

  20. Thermal ablation of liver metastases from colorectal cancer: radiofrequency, microwave and laser ablation therapies.

    PubMed

    Vogl, Thomas J; Farshid, Parviz; Naguib, Nagy N N; Darvishi, Abbas; Bazrafshan, Babak; Mbalisike, Emmanuel; Burkhard, Thorsten; Zangos, Stephan

    2014-07-01

    Surgery is currently considered the treatment of choice for patients with colorectal cancer liver metastases (CRLM) when resectable. The majority of these patients can also benefit from systemic chemotherapy. Recently, local or regional therapies such as thermal ablations have been used with acceptable outcomes. We searched the medical literature to identify studies and reviews relevant to radiofrequency (RF) ablation, microwave (MW) ablation and laser-induced thermotherapy (LITT) in terms of local progression, survival indexes and major complications in patients with CRLM. Reviewed literature showed a local progression rate between 2.8 and 29.7 % of RF-ablated liver lesions at 12-49 months follow-up, 2.7-12.5 % of MW ablated lesions at 5-19 months follow-up and 5.2 % of lesions treated with LITT at 6-month follow-up. Major complications were observed in 4-33 % of patients treated with RF ablation, 0-19 % of patients treated with MW ablation and 0.1-3.5 % of lesions treated with LITT. Although not significantly different, the mean of 1-, 3- and 5-year survival rates for RF-, MW- and laser ablated lesions was (92.6, 44.7, 31.1 %), (79, 38.6, 21 %) and (94.2, 61.5, 29.2 %), respectively. The median survival in these methods was 33.2, 29.5 and 33.7 months, respectively. Thermal ablation may be an appropriate alternative in patients with CRLM who have inoperable liver lesions or have operable lesions as an adjunct to resection. However, further competitive evaluation should clarify the efficacy and priority of these therapies in patients with colorectal cancer liver metastases.

  1. EUS-Guided Ethanol Ablation of Insulinomas

    PubMed Central

    Qin, Shan-yu; Lu, Xiu-ping; Jiang, Hai-xing

    2014-01-01

    Abstract Surgical resection is a standard treatment for insulinomas; however, it is associated with a high risk of complications and limited to specific suitable candidates. In recent years, endoscopic ultrasound (EUS)-guided ethanol ablation of insulinomas has emerged as a new therapeutic option, especially for elderly patients and candidates unfit for surgery. We aimed to evaluate the feasibility and safety of this technique for insulinomas. Four patients diagnosed with insulinomas based on EUS–fine-needle aspiration and immunohistochemistry results underwent EUS-guided 95% ethanol ablation. A comprehensive literature review was performed to understand the current status of the feasibility, safety, and effects of EUS-guided ethanol ablation of insulinomas. EUS-guided ethanol ablation of insulinomas was successfully completed in all the 4 patients. There were no perioperative or postoperative complications. The patients were discharged at 3 days after the procedure. No recurrence of hypoglycemia or tumors was noted during follow-up (range, 3–6 months). Literature review showed 8 patients with insulinomas who underwent EUS-guided ethanol ablation. All the procedures were successful, with no need for further surgical treatment. Among these reviewed cases, 6 patients had no post-procedural complications, while other 2 patients showed a mild increase in the serum levels of lipase and/or pancreatic enzymes within 48 h post-procedure; furthermore, 1 of these 2 patients presented at a later date with medically controllable hematoma and ulceration. During follow-up, 6 patients remained asymptomatic and normoglycemic, while the 2 patients who presented post-procedural complications developed occasional mild confusion. EUS-guided ethanol ablation of insulinomas is an effective and safe modality, with an acceptable level of post-procedural complications. However, the long-term effects of this new therapeutic option need to be validated in a large randomized controlled

  2. Self-regulation of ice flow varies across the ablation area in south-west Greenland

    NASA Astrophysics Data System (ADS)

    van de Wal, R. S. W.; Smeets, C. J. P. P.; Boot, W.; Stoffelen, M.; van Kampen, R.; Doyle, S. H.; Wilhelms, F.; van den Broeke, M. R.; Reijmer, C. H.; Oerlemans, J.; Hubbard, A.

    2015-04-01

    The concept of a positive feedback between ice flow and enhanced melt rates in a warmer climate fuelled the debate regarding the temporal and spatial controls on seasonal ice acceleration. Here we combine melt, basal water pressure and ice velocity data. Using 20 years of data covering the whole ablation area, we show that there is not a strong positive correlation between annual ice velocities and melt rates. Annual velocities even slightly decreased with increasing melt. Results also indicate that melt variations are most important for velocity variations in the upper ablation zone up to the equilibrium line altitude. During the extreme melt in 2012, a large velocity response near the equilibrium line was observed, highlighting the possibility of meltwater to have an impact even high on the ice sheet. This may lead to an increase of the annual ice velocity in the region above S9 and requires further monitoring.

  3. Self-regulation of ice flow varies across the ablation area in South-West Greenland

    NASA Astrophysics Data System (ADS)

    van de Wal, R. S. W.; Smeets, C. J. P. P.; Boot, W.; Stoffelen, M.; van Kampen, R.; Doyle, S.; Wilhelms, F.; van den Broeke, M. R.; Reijmer, C. H.; Oerlemans, J.; Hubbard, A.

    2014-09-01

    The concept of a positive feedback between ice flow and enhanced melt rates in a warmer climate fuelled the debate regarding the temporal and spatial controls on seasonal ice acceleration. Here we combine melt, basal water pressure, and ice velocity data. We show using twenty years of data covering the whole ablation area that there is no strong feedback between annual ice velocities and melt rates. Annual velocities even slightly decreased with increasing melt. Results also indicate that melt variations are most important for velocity variations in the upper ablation zone up to the equilibrium line altitude. During the extreme melt in 2012 a large velocity response near the equilibrium line was observed, highlighting the possibility of rapidly changing bed conditions in this part of the ice sheet that may lead to a doubling of the annual ice velocity.

  4. Johannes Kepler and Extra Dimensions

    NASA Astrophysics Data System (ADS)

    Hendry, Archibald W.

    2004-02-01

    How many dimensions are there? The answer used to be four — three spatial and one time dimension. Maybe it still is, though nowadays we hear that the answer may be more, perhaps many more. Many of our students have heard about this on television or read about it. They want to know more. Why do physicists think we need more than three spatial dimensions? What's the point of it all?

  5. Determination of cytotoxic thermal dose during HIFU ablation

    NASA Astrophysics Data System (ADS)

    Nandlall, Sacha D.; Bazán-Peregrino, Miriam; Mo, Steven; Coussios, Constantin-C.

    2012-10-01

    Thermal dose has been proposed for various hyperthermic cancer treatment modalities as a measure of heat-induced cell and tissue damage. However, many of the models that are currently used for calculating thermal dose have not been validated or suitably adapted for the elevated temperatures and rates of heating encountered during ablation by High-Intensity Focused Ultrasound (HIFU). This work quantifies the performance of the widely employed Cumulative Equivalent Minutes at 43°C (CEM43) thermal dose metric under HIFU-relevant heating. A total of 36 agar phantoms were embedded with different human cancer cell lines (PC3, 22RV1, or ZR75.1) as well as calcein AM and propidium iodide assays. The phantoms were cast in sterile molds with internal dimensions of 7 cm × 7 cm × 2 mm. Using a water bath, 12 of the phantoms were treated with mild hyperthermia (43-46°C for up to 60 minutes), while another 12 were subjected to HIFU-relevant temperature profiles (60-80°C peak temperature, 2-3°C/s peak heating rate). In each of the remaining 12 phantoms, 8 HIFU exposures were carried out in a 37°C water tank (1.067 MHz, 95% duty cycle, 3-6 MPa peak rarefaction pressure, 2-20 s exposure duration). Cavitation emissions were monitored passively with a detector transducer that was confocally and co-axially aligned with the HIFU source. Cell death was quantified by measuring the locally averaged fluorescence intensity of the assays relative to unheated and severely heat-shocked phantoms. The results show that the CEM43 dose required to achieve the same level of heat-induced cell death varies considerably across cell lines, and that inertial cavitation can cause significant mechanical damage at ablation-relevant intensities even when no significant thermal dose is delivered (CEM43 < 5 s). These findings demonstrate the need for improved models of cell death at ablation-relevant temperatures.

  6. Revisiting the interplay between ablation, collisional, and radiative processes during ns-laser ablation

    NASA Astrophysics Data System (ADS)

    Autrique, D.; Gornushkin, I.; Alexiades, V.; Chen, Z.; Bogaerts, A.; Rethfeld, B.

    2013-10-01

    A study of ns-laser ablation is presented, which focuses on the transient behavior of the physical processes that act in and above a copper sample. A dimensionless multiphase collisional radiative model describes the interplay between the ablation, collisional, and radiative mechanisms. Calculations are done for a 6 ns-Nd:YAG laser pulse operating at 532 nm and fluences up to 15 J/cm2. Temporal intensity profiles as well as transmissivities are in good agreement with experimental results. It is found that volumetric ablation mechanisms and photo-processes both play an essential role in the onset of ns-laser induced breakdown.

  7. 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.

  8. Physics in one dimension

    NASA Astrophysics Data System (ADS)

    van Houselt, A.; Schäfer, J.; Zandvliet, H. J. W.; Claessen, R.

    2013-01-01

    With modern microelectronics moving towards smaller and smaller length scales on the (sub-) nm scale, quantum effects (apart from band structure and band gaps) have begun to play an increasingly important role. This especially concerns dimensional confinement to 2D (high electron mobility transistors and integer/fractional quantum Hall effect physics, graphene and topological insulators) and 1D (with electrical connections eventually reaching the quantum limit). Recent developments in the above-mentioned areas have revealed that the properties of electron systems become increasingly exotic as one progresses from the 3D case into lower dimensions. As compared to 2D electron systems, much less experimental progress has been achieved in the field of 1D electron systems. The main reason for the lack of experimental results in this field is related to the difficulty of realizing 1D electron systems. Atom chains created in quantum mechanical break junction set-ups are too short to exhibit the typically 1D signatures. As an alternative, atomic chains can be produced on crystal surfaces, either via assembling them one-by-one using a scanning tunnelling microscope or via self-assembly. The drawback of the latter systems is that the atomic chains are not truly 1D since they are coupled to the underlying crystal and sometimes even to the neighbouring chains. In retrospect, this coupling turns out to be an absolute necessity in the experiment since true 1D systems are disordered at any non-zero temperature [1]. The coupling to the crystal and/or neighbouring chains shifts the phase transition, for example, a Peierls instability, to a non-zero temperature and thus allows experiments to be performed in the ordered state. Here, we want to emphasize that the electronic properties of the 1D electron system are fundamentally different from its 2D and 3D counterparts. The Fermi liquid theory, which is applicable to 2D and 3D electron systems, breaks down spectacularly in the 1D case

  9. Nonminimal universal extra dimensions

    SciTech Connect

    Flacke, Thomas; Menon, A.; Phalen, Daniel J.

    2009-03-01

    In this paper, we investigate the phenomenological implications of boundary localized terms (BLTs) in the model of universal extra dimensions (UED). In particular, we study the electroweak Kaluza-Klein mass spectrum resulting from BLTs and their effect on electroweak symmetry breaking via the five-dimensional Higgs mechanism. We find that the addition of BLTs to massive five-dimensional fields induces a nontrivial extra-dimensional profile for the zero and nonzero Kaluza-Klein (KK) modes. Hence BLTs generically lead to a modification of standard model parameters and are therefore experimentally constrained, even at tree level. We study standard model constraints on three representative nonminimal UED models in detail and find that the constraints on BLTs are weak. On the contrary, nonzero BLTs have a major impact on the spectrum and couplings of nonzero KK modes. For example, there are regions of parameter space where the lightest Kaluza-Klein particle is either the Kaluza-Klein Higgs boson or the first KK mode of the W{sup 3}.

  10. Ablation of carbide materials with femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Sentis, Marc; Marine, Wladimir

    2003-01-01

    The response of cemented tungsten carbide and of titanium carbonitride was investigated with respect to damage and ablation properties, under interaction with ultrashort laser pulses. These carbide materials present high microhardness and are of significant interest for tribological applications. The experiments were carried out in air with a commercial Ti:sapphire laser at energy densities on the target up to 6.5 J/cm 2. The irradiated target surfaces were analyzed with optical, SEM and AFM techniques and the damage and ablation threshold values were determined using the measured spot diameters and the calculated incident energy density distributions.

  11. High throughput solar cell ablation system

    SciTech Connect

    Harley, Gabriel; Pass, Thomas; Cousins, Peter John; Viatella, John

    2014-10-14

    A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

  12. General Model for Multicomponent Ablation Thermochemistry

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Marschall, Jochen; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    A previous paper (AIAA 94-2042) presented equations and numerical procedures for modeling the thermochemical ablation and pyrolysis of thermal protection materials which contain multiple surface species. This work describes modifications and enhancements to the Multicomponent Ablation Thermochemistry (MAT) theory and code for application to the general case which includes surface area constraints, rate limited surface reactions, and non-thermochemical mass loss (failure). Detailed results and comparisons with data are presented for the Shuttle Orbiter reinforced carbon-carbon oxidation protection system which contains a mixture of sodium silicate (Na2SiO3), silica (SiO2), silicon carbide (SiC), and carbon (C).

  13. Testing of Advanced Conformal Ablative TPS

    NASA Technical Reports Server (NTRS)

    Gasch, Matthew; Agrawal, Parul; Beck, Robin

    2013-01-01

    In support of the CA250 project, this paper details the results of a test campaign that was conducted at the Ames Arcjet Facility, wherein several novel low density thermal protection (TPS) materials were evaluated in an entry like environment. The motivation for these tests was to investigate whether novel conformal ablative TPS materials can perform under high heat flux and shear environment as a viable alternative to rigid ablators like PICA or Avcoat for missions like MSL and beyond. A conformable TPS over a rigid aeroshell has the potential to solve a number of challenges faced by traditional rigid TPS materials (such as tiled Phenolic Impregnated Carbon Ablator (PICA) system on MSL, and honeycomb-based Avcoat on the Orion Multi Purpose Crew Vehicle (MPCV)). The compliant (high strain to failure) nature of the conformable ablative materials will allow better integration of the TPS with the underlying aeroshell structure and enable monolithic-like configuration and larger segments to be used in fabrication.A novel SPRITE1 architecture, developed by the researchers at NASA Ames was used for arcjet testing. This small probe like configuration with 450 spherecone, enabled us to test the materials in a combination of high heat flux, pressure and shear environment. The heat flux near the nose were in the range of 500-1000 W/sq cm whereas in the flank section of the test article the magnitudes were about 50 of the nose, 250-500W/sq cm range. There were two candidate conformable materials under consideration for this test series. Both test materials are low density (0.28 g/cu cm) similar to Phenolic Impregnated Carbon Ablator (PICA) or Silicone Impregnated Refractory Ceramic Ablator (SIRCA) and are comprised of: A flexible carbon substrate (Carbon felt) infiltrated with an ablative resin system: phenolic (Conformal-PICA) or silicone (Conformal-SICA). The test demonstrated a successful performance of both the conformable ablators for heat flux conditions between 50

  14. 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.

  15. High throughput solar cell ablation system

    DOEpatents

    Harley, Gabriel; Pass, Thomas; Cousins, Peter John; Viatella, John

    2012-09-11

    A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

  16. Thermal dimension of quantum spacetime

    NASA Astrophysics Data System (ADS)

    Amelino-Camelia, Giovanni; Brighenti, Francesco; Gubitosi, Giulia; Santos, Grasiele

    2017-04-01

    Recent results suggest that a crucial crossroad for quantum gravity is the characterization of the effective dimension of spacetime at short distances, where quantum properties of spacetime become significant. This is relevant in particular for various scenarios of "dynamical dimensional reduction" which have been discussed in the literature. We are here concerned with the fact that the related research effort has been based mostly on analyses of the "spectral dimension", which involves an unphysical Euclideanization of spacetime and is highly sensitive to the off-shell properties of a theory. As here shown, different formulations of the same physical theory can have wildly different spectral dimension. We propose that dynamical dimensional reduction should be described in terms of the "thermal dimension" which we here introduce, a notion that only depends on the physical content of the theory. We analyze a few models with dynamical reduction both of the spectral dimension and of our thermal dimension, finding in particular some cases where thermal and spectral dimension agree, but also some cases where the spectral dimension has puzzling properties while the thermal dimension gives a different and meaningful picture.

  17. Exterior dimension of fat fractals

    NASA Technical Reports Server (NTRS)

    Grebogi, C.; Mcdonald, S. W.; Ott, E.; Yorke, J. A.

    1985-01-01

    Geometric scaling properties of fat fractal sets (fractals with finite volume) are discussed and characterized via the introduction of a new dimension-like quantity which is called the exterior dimension. In addition, it is shown that the exterior dimension is related to the 'uncertainty exponent' previously used in studies of fractal basin boundaries, and it is shown how this connection can be exploited to determine the exterior dimension. Three illustrative applications are described, two in nonlinear dynamics and one dealing with blood flow in the body. Possible relevance to porous materials and ballistic driven aggregation is also noted.

  18. Photothermal ablation of liver tissue with 1940-nm thulium fiber laser: an ex vivo study on lamb liver

    NASA Astrophysics Data System (ADS)

    Alagha, Heba Z.; Gülsoy, Murat

    2016-01-01

    The purpose of this study was to investigate the ablation efficiency of 1940-nm thulium fiber laser on liver tissue, while utilizing a real-time measurement system to monitor the temperature rise in adjacent tissues. Thulium fiber laser was delivered to lamb liver tissue samples via 400-μm bare tip fiber in contact mode. Eight different laser parameter combinations [power, continuous-wave (cw)/pulsed-modulated (pm) mode, and exposure time] were used. Exposure times were chosen to give the same total applied energy of 4 J for comparative purposes. Following laser irradiations, tissues were processed and stained with hematoxylin and eosin for macroscopic evaluation of ablation areas and total altered areas, and ablation efficiencies were calculated. Temperature of the nearby tissue at a distance of 1 mm from the fiber was measured, and rate of temperature change was calculated. A strong correlation between the rate of temperature change and ablation area was noted. Thermal effects increased with increasing power for both modes. The continuous-wave mode yielded higher ablation efficiencies than the pulse-modulated mode. Histological evaluation revealed a narrow vacuolization zone and negligible carbonization for higher-power values.

  19. Evaluation of the effective corneal ablation in refractive surgery by two 3D topographic surface matching methods

    NASA Astrophysics Data System (ADS)

    Bueeler, M.; Donitzky, Ch.; Mrochen, M.

    2006-02-01

    The effectiveness of the corneal ablation process in refractive surgery is mostly evaluated by indirect measures of vision or optical quality such as post-operative refraction or wavefront aberrometry. Yet, the effective amount of corneal tissue removed in the treatment can only be determined by correctly overlapping a pre- and a post-operative topography measurement. However such an overlap is not trivial due to the discrepancy in the centration axes used in the measurement and the treatment, as well as due to the shift of ocular axes through the treatment or tilt between the two surfaces. We therefore present two methods for overlapping pre- and post-operative topographies for the purpose of extracting an effective corneal ablation profile. Method one uses a 3-dimensional profile matching algorithm and cross-correlation analysis on surface rings outside the optical zone of the topographies. Method two employs a surface normal matching routine to align the two surfaces along their common ablation axis. The profile matching method implies the problem that it requires measurement data outside of the optical zone which was found to be uncertain with placido-disk-based topographers. Method number two is more simple and implies the advantage of using measurement data within the optical zone. For regular profiles the extracted ablation profiles showed a very good match with the planned ones. Surprisingly, even for highly irregular profiles of topography-guided laser treatments the method delivered reasonable overlaps when being compared to the planned profiles. Analysis of the effective tissue removal yields valuable information on the quality of the ablation process.

  20. Distributed modeling of ablation (1996–2011) and climate sensitivity on the glaciers of Taylor Valley, Antarctica

    SciTech Connect

    Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.

    2016-02-24

    Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than over smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K–1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.

  1. Sequential activation of a segmented ground pad reduces skin heating during radiofrequency tumor ablation: optimization via computational models.

    PubMed

    Schutt, David J; Haemmerich, Dieter

    2008-07-01

    Radiofrequency (RF) ablation has become an accepted treatment modality for unresectable tumors. The need for larger ablation zones has resulted in increased RF generator power. Skin burns due to ground pad heating are increasingly limiting further increases in generator power, and thus, ablation zone size. We investigated a method for reducing ground pad heating in which a commercial ground pad is segmented into multiple ground electrodes, with sequential activation of ground electrode subsets. We created finite-element method computer models of a commercial ground pad (14 x 23 cm) and compared normal operation of a standard pad to sequential activation of a segmented pad (two to five separate ground electrode segments). A constant current of 1 A was applied for 12 min in all simulations. Time periods during sequential activation simulations were adjusted to keep the leading edge temperatures at each ground electrode equal. The maximum temperature using standard activation of the commercial pad was 41.7 degrees C. For sequential activation of a segmented pad, the maximum temperature ranged from 39.3 degrees C (five segments) to 40.9 degrees C (two segments). Sequential activation of a segmented ground pad resulted in lower tissue temperatures. This method may reduce the incidence of ground pad burns and enable the use of higher power generators during RF tumor ablation.

  2. Distributed modeling of ablation (1996–2011) and climate sensitivity on the glaciers of Taylor Valley, Antarctica

    DOE PAGES

    Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.

    2016-02-24

    Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than overmore » smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K–1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less

  3. Sequential Activation of a Segmented Ground Pad Reduces Skin Heating During Radiofrequency Tumor Ablation: Optimization via Computational Models

    PubMed Central

    Schutt, David J.; Haemmerich, Dieter

    2009-01-01

    Radiofrequency (RF) ablation has become an accepted treatment modality for unresectable tumors. The need for larger ablation zones has resulted in increased RF generator power. Skin burns due to ground pad heating are increasingly limiting further increases in generator power, and thus, ablation zone size. We investigated a method for reducing ground pad heating in which a commercial ground pad is segmented into multiple ground electrodes, with sequential activation of ground electrode subsets. We created finite-element method computer models of a commercial ground pad (14 × 23 cm) and compared normal operation of a standard pad to sequential activation of a segmented pad (two to five separate ground electrode segments). A constant current of 1 A was applied for 12 min in all simulations. Time periods during sequential activation simulations were adjusted to keep the leading edge temperatures at each ground electrode equal. The maximum temperature using standard activation of the commercial pad was 41.7 °C. For sequential activation of a segmented pad, the maximum temperature ranged from 39.3 °C (five segments) to 40.9 °C (two segments). Sequential activation of a segmented ground pad resulted in lower tissue temperatures. This method may reduce the incidence of ground pad burns and enable the use of higher power generators during RF tumor ablation. PMID:18595807

  4. Experimental measurement of ablation effects in plasma armature railguns

    SciTech Connect

    Parker, J.V.; Parsons, W.M.

    1986-01-01

    Experimental evidence supporting the importance of ablation in plasma armature railguns is presented. Experiments conducted using the HYVAX and MIDI-2 railguns are described. Several indirect effects of ablation are identified from the experimental results. An improved ablation model of plasma armature dynamics is proposed which incorporates the restrike process.

  5. Ablation techniques for primary and metastatic liver tumors

    PubMed Central

    Ryan, Michael J; Willatt, Jonathon; Majdalany, Bill S; Kielar, Ania Z; Chong, Suzanne; Ruma, Julie A; Pandya, Amit

    2016-01-01

    Ablative treatment methods have emerged as safe and effective therapies for patients with primary and secondary liver tumors who are not surgical candidates at the time of diagnosis. This article reviews the current literature and describes the techniques, complications and results for radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation. PMID:26839642

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

    PubMed Central

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

    2017-01-01

    AIM To assess the insulating effect of a poloxamer 407 (P407)-based gel during microwave ablation of liver adjacent to the diaphragm. METHODS 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. RESULTS 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). CONCLUSION 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.

  7. First Brillouin Polytope and Band Structure of Diamond Lattice in Four Dimensions

    NASA Astrophysics Data System (ADS)

    Kato, Yuichi; Yamanaka, Masanori

    2017-03-01

    We study the diamond lattice in four dimensions — a descendant of the three-dimensional diamond lattice. As a four-dimensional polytope, we determine the first Brillouin zone and draw the band structure of the corresponding tight-binding model on two-dimensional paper in the usual manner. In the polyhedral decomposition, we find the zone boundary of the first Brillouin zone in four dimensions to be the omnitruncated 5-cell, which comprises ten truncated octahedra glued to 20 hexagonal prisms. We find Dirac line nodes inside the hexagonal prisms.

  8. Mixing materials within zone boundaries using shape overlays

    SciTech Connect

    Grandy, J.

    1997-04-22

    Shape overlays provide a means of statically imposing a physical region containing specified material properties onto a zoned mesh. In the most general case, material interface boundaries are unrelated to mesh zone boundaries, causing zones to contain a mixture of materials, and the mesh itself is not uniform in physical space. We develop and apply an algorithm for shape overlays on nonorthogonal, nonuniform meshes in two dimensions. Examples of shape generation in a multiblock uid dynamics code are shown.

  9. Dimensions of temperament: an analysis.

    PubMed

    Lorr, M; Stefic, E C

    1976-01-01

    The TDOT recast into a single stimulus format was administered to 150 college Ss. A factor analysis of the items followed by an analysis of item clusters that define each factor indicated the presence of 14 dimensions. Of the 10 bipolar scales of the TDOT, 3 were confirmed as independent dimensions, and 5 were confirmed in part or split into unipolar factors.

  10. Mathematics Teachers' Criteria of Dimension

    ERIC Educational Resources Information Center

    Ural, Alattin

    2014-01-01

    The aim of the study is to determine mathematics teachers' decisions about dimensions of the geometric figures, criteria of dimension and consistency of decision-criteria. The research is a qualitative research and the model applied in the study is descriptive method on the basis of general scanning model. 15 mathematics teachers attended the…

  11. Dimensioning, Tolerancing, and Machine Finishes.

    ERIC Educational Resources Information Center

    Adams, George C.

    Intended for use with the vocational education student interested in technical drawing, this guide provides answers to questions relating to dimensioning and tolerancing machine drawings. It also gives examples of standard dimensioning practices, tolerancing applications, and finish applications. The problems and examples presented are based on…

  12. String universality in ten dimensions.

    PubMed

    Adams, Allan; Taylor, Washington; Dewolfe, Oliver

    2010-08-13

    We show that the N=1 supergravity theories in ten dimensions with gauge groups U(1){496} and E{8}×U(1){248} are not consistent quantum theories. Cancellation of anomalies cannot be made compatible with supersymmetry and Abelian gauge invariance. Thus, in ten dimensions all supersymmetric theories of gravity without known inconsistencies are realized in string theory.

  13. The Dimensions of Maltreatment: Introduction

    ERIC Educational Resources Information Center

    English, Diana J.; Bangdiwala, Shrikant I.; Runyan, Desmond K.

    2005-01-01

    This special issue includes an introduction and seven papers exploring dimensions of maltreatment including type, severity, chronicity, and substantiation status of referrals to CPS, utilizing a subsample of the LONGSCAN studies. Each paper examines one of the dimensions of maltreatment from various perspectives to determine if different…

  14. UV laser ablation patterns in intraocular lenses

    NASA Astrophysics Data System (ADS)

    Lagiou, D. P.; Evangelatos, Ch.; Apostolopoulos, A.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

    2013-03-01

    The aim of this work is to investigate the effect of UV solid state laser radiation on intraocular lens (IOL) polymer surfaces as an alternative method to conventional surface shaping techniques for IOLs customization. Laser ablation experiments were performed on PMMA plates and commercially available hydrophobic and hydrophilic acrylic IOLs with the 5th harmonic of a Q-switched Nd:YAG laser (λ=213 nm). Circular arrays of holes were drilled on the polymer surface, covering the centre and the peripheries of the IOL. The morphology of the ablated IOL surface was examined with a conventional optical microscope (Leitz GMBH Wetzlar) and with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements of ablation rates were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variationsF in surface height. Laser interaction with IOLs depends on optical and mechanical material properties, in addition to laser radiation parameters. The exact ablation mechanism is discussed. Some polymer materials, depending on their properties, are more susceptible to the photothermal mechanism than the photochemical one or vice versa. In summary, every IOL polymer exhibits specific attributes in its interaction with the 5th harmonic of Nd:YAG laser.

  15. Organized Atrial Tachycardias after Atrial Fibrillation Ablation

    PubMed Central

    Castrejón-Castrejón, Sergio; Ortega, Marta; Pérez-Silva, Armando; Doiny, David; Estrada, Alejandro; Filgueiras, David; López-Sendón, José L.; Merino, José L.

    2011-01-01

    The efficacy of catheter-based ablation techniques to treat atrial fibrillation is limited not only by recurrences of this arrhythmia but also, and not less importantly, by new-onset organized atrial tachycardias. The incidence of such tachycardias depends on the type and duration of the baseline atrial fibrillation and specially on the ablation technique which was used during the index procedure. It has been repeatedly reported that the more extensive the left atrial surface ablated, the higher the incidence of organized atrial tachycardias. The exact origin of the pathologic substrate of these trachycardias is not fully understood and may result from the interaction between preexistent regions with abnormal electrical properties and the new ones resultant from radiofrequency delivery. From a clinical point of view these atrial tachycardias tend to remit after a variable time but in some cases are responsible for significant symptoms. A precise knowledge of the most frequent types of these arrhythmias, of their mechanisms and components is necessary for a thorough electrophysiologic characterization if a new ablation procedure is required. PMID:21941669

  16. Outpatient laser tonsillar ablation under local anaesthetic.

    PubMed

    Andrews, Peter J; Latif, Abdul

    2004-11-01

    Outpatient laser ablation of the palatine tonsils under local anaesthetic is an alternative technique to capsular tonsillectomy for recurrent tonsillitis under general anaesthetic. Laser tonsillotomy ablates up to 70% of the tonsillar tissue and is performed when patients choose not to have a conventional tonsillectomy, or are unfit for a general anaesthetic. The technique described here is an adaptation of Krespis' laser-assisted serial tonsillectomy (LAST) whereby only one sitting is required. Krespis' technique effectively eliminates recurrent tonsillitis in 96% of the cases over a 4-year follow-up period and represents the only substantial study looking at treating recurrent tonsillitis with outpatient laser ablation. This study is a retrospective postal survey of 19 patients who underwent laser tonsillar ablation under local anaesthetic for recurrent chronic tonsillitis from 1997 to 2001 and was performed in liaison with the clinical audit department at Basildon Hospital. We had a response rate of 74% and an admission rate of 0%, which compares favourably with day case tonsillectomy surgery. Of the patients, 75% did not experience further episodes of tonsillitis 12 months after the procedure and 77% of the patients were glad they had the operation. Although this technique does not completely eliminate tonsillitis, it offers an alternative for those patients who prefer a procedure that is done quickly in an outpatient setting without the additional problems of general anaesthesia, overnight hospital admission and long waiting lists.

  17. Intumescent-ablator coatings using endothermic fillers

    NASA Technical Reports Server (NTRS)

    Sawko, P. M.; Riccitiello, S. R. (Inventor)

    1978-01-01

    An intumescent-ablator coating composition which contains the ammonium salt of 1,4-nitroaniline-2-sulfonic acid or 4,4 dinitrosul fanilide, a polymeric binder system and about 5 to 30% weight of an endothermic filler is reported. The filler has a decomposition temperature about or within the exothermic region of the intumescent agent.

  18. Microwave ablation devices for interventional oncology.

    PubMed

    Ward, Robert C; Healey, Terrance T; Dupuy, Damian E

    2013-03-01

    Microwave ablation is one of the several options in the ablation armamentarium for the treatment of malignancy, offering several potential benefits when compared with other ablation, radiation, surgical and medical treatment modalities. The basic microwave system consists of the generator, power distribution system and antennas. Often under image (computed tomography or ultrasound) guidance, a needle-like antenna is inserted percutaneously into the tumor, where local microwave electromagnetic radiation is emitted from the probe's active tip, producing frictional tissue heating, capable of causing cell death by coagulation necrosis. Half of the microwave ablation systems use a 915 MHz generator and the other half use a 2450 MHz generator. To date, there are no completed clinical trials comparing microwave devices head-to-head. Prospective comparisons of microwave technology with other treatment alternatives, as well as head-to-head comparison with each microwave device, is needed if this promising field will garner more widespread support and use in the oncology community.

  19. Ablation Resistant Zirconium and Hafnium Ceramics

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

    1998-01-01

    High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

  20. Laboratory Micrometeroid/Dust Ablation Studies

    NASA Astrophysics Data System (ADS)

    Thomas, E.; Horanyi, M.; Janches, D.; Munsat, T. L.; Plane, J. M. C.; Simolka, J.; Sternovsky, Z.

    2014-12-01

    Each day, somewhere between 5-270 tonnes of meteoric material ablates in Earth's upper atmosphere. Thisenormous range is significant because the Interplanetary Dust Particle (IDP) input has implications in ourunderstanding of meteor transport in the atmosphere, the formation of layers of metal atoms and ions,nucleation of noctilucent clouds, effects on stratospheric aerosols and O3 chemistry, and dust evolution inour solar system. As the dust ablates, it produces light, as well as a plasma trail of ionized atmosphericatoms and electrons. These meteor signatures are detected by photographic means, or by radar, but thereremain uncertainties in the luminous efficiency and ionization coefficient of meteors - two parameters thatare essential to evaluate densities, masses, height distributions and fluxes. Precise measurements of theseparameters would allow for not only an understanding of the layers of metal atoms and ions and meteoricsmoke particles in the mesosphere and lower thermosphere, but also would allow for the Earth's atmosphereto be used as a dust detector to detect and characterize the dust environment in our solar system. This work discusses the preliminary results of the new dust ablation facility at the 3 MV hypervelocity dust accelerator at the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) at the University of Colorado, which aims to characterize the ionization coefficient and luminous efficiency of ablating micrometeroids.

  1. Combining Electrolysis and Electroporation for Tissue Ablation.

    PubMed

    Phillips, Mary; Rubinsky, Liel; Meir, Arie; Raju, Narayan; Rubinsky, Boris

    2015-08-01

    Electrolytic ablation is a method that operates by delivering low magnitude direct current to the target region over long periods of time, generating electrolytic products that destroy cells. This study was designed to explore the hypothesis stating that electrolytic ablation can be made more effective when the electrolysis-producing electric charges are delivered using electric pulses with field strength typical in reversible electroporation protocols. (For brevity we will refer to tissue ablation protocols that combine electroporation and electrolysis as E(2).) The mechanistic explanation of this hypothesis is related to the idea that products of electrolysis generated by E(2) protocols can gain access to the interior of the cell through the electroporation permeabilized cell membrane and therefore cause more effective cell death than from the exterior of an intact cell. The goal of this study is to provide a first-order examination of this hypothesis by comparing the charge dosage required to cause a comparable level of damage to a rat liver, in vivo, when using either conventional electrolysis or E(2) approaches. Our results show that E(2) protocols produce tissue damage that is consistent with electrolytic ablation. Furthermore, E(2) protocols cause damage comparable to that produced by conventional electrolytic protocols while delivering orders of magnitude less charge to the target tissue over much shorter periods of time.

  2. Atmospheric Profile Imprint in Firewall Ablation Coefficient

    NASA Technical Reports Server (NTRS)

    Ceplecha, Z.; Pecina, P.

    1984-01-01

    A general formula which expresses the distance along the meteoric fireball trajectory 1 as a function of t is discussed. Differential equations which include the motion and ablation of a single nonfragmenting meteor body are presented. The importance of the atmospheric density profile in the meteor formula is emphasized.

  3. Microwave tumors ablation: principles, clinical applications and review of preliminary experiences.

    PubMed

    Carrafiello, Gianpaolo; Laganà, Domenico; Mangini, Monica; Fontana, Federico; Dionigi, Gianlorenzo; Boni, Luigi; Rovera, Francesca; Cuffari, Salvatore; Fugazzola, Carlo

    2008-01-01

    Local ablative techniques have been developed to enable local control of unresectable tumors. Ablation has been performed with several modalities including ethanol ablation, laser ablation, cryoablation, and radiofrequency ablation. Microwave technology is a new thermal ablation technique for different types of tumors, providing all the benefits of radiofrequency and substantial advantages. Microwave ablation has been applied to liver, lung, kidney and more rarely to bone, pancreas and adrenal glands. Preliminary works show that microwave ablation may be a viable alternative to other ablation techniques in selected patients. However further studies are necessary to confirm short- and long-term effectiveness of the methods and to compare it with other ablative techniques, especially RF.

  4. Thermochemical Ablation Analysis of the Orion Heatshield

    NASA Technical Reports Server (NTRS)

    Sixel, William

    2015-01-01

    The Orion Multi-Purpose Crew Vehicle will one day carry astronauts to the Moon and beyond, and Orion's heatshield is a critical component in ensuring their safe return to Earth. The Orion heatshield is the structural component responsible for absorbing the intense heating environment caused by re-entry to Earth's atmosphere. The heatshield is primarily composed of Avcoat, an ablative material that is consumed during the re-entry process. Ablation is primarily characterized by two processes: pyrolysis and recession. The decomposition of in-depth virgin material is known as pyrolysis. Recession occurs when the exposed surface of the heatshield reacts with the surrounding flow. The Orion heatshield design was changed from an individually filled Avcoat honeycomb to a molded block Avcoat design. The molded block Avcoat heatshield relies on an adhesive bond to keep it attached to the capsule. In some locations on the heatshield, the integrity of the adhesive bond cannot be verified. For these locations, a mechanical retention device was proposed. Avcoat ablation was modelled in CHAR and the in-depth virgin material temperatures were used in a Thermal Desktop model of the mechanical retention device. The retention device was analyzed and shown to cause a large increase in the maximum bondline temperature. In order to study the impact of individual ablation modelling parameters on the heatshield sizing process, a Monte Carlo simulation of the sizing process was proposed. The simulation will give the sensitivity of the ablation model to each of its input parameters. As part of the Monte Carlo simulation, statistical uncertainties on material properties were required for Avcoat. Several properties were difficult to acquire uncertainties for: the pyrolysis gas enthalpy, non-dimensional mass loss rate (B´c), and Arrhenius equation parameters. Variability in the elemental composition of Avcoat was used as the basis for determining the statistical uncertainty in pyrolysis gas

  5. Aluminum X-ray mass-ablation rate measurements

    DOE PAGES

    Kline, John L.; Hager, Jonathan D.

    2016-10-15

    Measurements of the mass ablation rate of aluminum (Al) have been completed at the Omega Laser Facility. Measurements of the mass-ablation rate show Al is higher than plastic (CH), comparable to high density carbon (HDC), and lower than beryllium. The mass-ablation rate is consistent with predictions using a 1D Lagrangian code, Helios. Lastly, the results suggest Al capsules have a reasonable ablation pressure even with a higher albedo than beryllium or carbon ablators warranting further investigation into the viability of Al capsules for ignition should be pursued.

  6. Plume collimation for laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A.

    2016-06-07

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  7. Plume collimation for laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  8. Contemporary Status of Percutaneous Ablation for the Small Renal Mass.

    PubMed

    Shin, Benjamin J; Chick, Jeffrey Forris Beecham; Stavropoulos, S William

    2016-03-01

    Renal cell carcinoma is the tenth most common malignancy in the USA, with upwards of 61,000 new cases and resulting in more than 14,000 deaths annually. Although partial nephrectomy remains the standard treatment, image-guided nephron-sparing ablative techniques including cryoablation, radiofrequency ablation, and microwave ablation have emerged as treatment options in certain patient populations. Ablative therapies have high technical successes, low tumor recurrence rates, and preserve renal parenchymal volume. The purpose of this article is to provide an update on ablation therapies for small renal masses.

  9. Burn, freeze, or photo-ablate?: comparative symptom profile in Barrett's dysplasia patients undergoing endoscopic ablation

    NASA Astrophysics Data System (ADS)

    Gill, Kanwar Rupinder S.; Gross, Seth A.; Greenwald, Bruce D.; Hemminger, Lois L.; Wolfsen, Herbert C.

    2009-06-01

    Background: There are few data available comparing endoscopic ablation methods for Barrett's esophagus with high-grade dysplasia (BE-HGD). Objective: To determine differences in symptoms and complications associated with endoscopic ablation. Design: Prospective observational study. Setting: Two tertiary care centers in USA. Patients: Consecutive patients with BE-HGD Interventions: In this pilot study, symptoms profile data were collected for BE-HGD patients among 3 endoscopic ablation methods: porfimer sodium photodynamic therapy, radiofrequency ablation and low-pressure liquid nitrogen spray cryotherapy. Main Outcome Measurements: Symptom profiles and complications from the procedures were assessed 1-8 weeks after treatment. Results: Ten BE-HGD patients were treated with each ablation modality (30 patients total; 25 men, median age: 69 years (range 53-81). All procedures were performed in the clinic setting and none required subsequent hospitalization. The most common symptoms among all therapies were chest pain, dysphagia and odynophagia. More patients (n=8) in the porfimer sodium photodynamic therapy group reported weight loss compared to radio-frequency ablactation (n=2) and cryotherapy (n=0). Four patients in the porfimer sodium photodynamic therapy group developed phototoxicity requiring medical treatment. Strictures, each requiring a single dilation, were found in radiofrequency ablactation (n=1) and porfimer sodium photodynamic therapy (n=2) patients. Limitations: Small sample size, non-randomized study. Conclusions: These three endoscopic therapies are associated with different types and severity of post-ablation symptoms and complications.

  10. Femtosecond laser ablation of CuxZr1-x bulk metallic glasses: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Marinier, Sébastien; Lewis, Laurent J.

    2015-11-01

    Molecular-dynamics simulations combined with a two-temperature model are used to study laser ablation in CuxZr1-x (x =0.33 ,0.50 ,0.67 ) metallic glasses as well as crystalline CuZr2 in the C11b (MoSi2) structure. Ablation thresholds are found to be 430 ±10 ,450 ±10 ,510 ±10 , and 470 ±10 J/m 2 for a-Cu2Zr , a-CuZr, a-CuZr2, and c-CuZr2, respectively. The larger threshold in amorphous CuZr2 results from a weaker electron-phonon coupling and thus longer electron-ion equilibration time. We observe that the velocity of the pressure waves in the amorphous samples is not affected by the fluence, in contrast to the crystal; this is due to differences in the behavior of the shear modulus with increasing pressure. The heat-affected zone in the different systems is characterized in terms of the melting depth as well as inelastic deformations. The melting depth is found to be smaller in the crystal than in the amorphous targets because of its higher melting temperature. The inelastic deformations are investigated in terms of the von Mises shear strain invariant ηMises; the homogeneous nucleation of shear transformation zones is observed in the glass as reported in previous theoretical and experimental studies. The coalescence of the shear transformation zones is also found at higher fluence.

  11. Ablation of bone and polymethylmethacrylate by an XeCl (308 nm) excimer laser

    SciTech Connect

    Yow, L.; Nelson, J.S.; Berns, M.W.

    1989-01-01

    One of the main problems in orthopaedics is the surgical removal of hard substances, such as bone and polymethylmethacrylate (PMMA). Such materials are often very difficult to remove without mechanical trauma to the remaining tissue. This study investigated the feasibility of the ultraviolet 308 nm excimer laser in the ablation of these materials. The beam was delivered through a 1 mm-diameter fiber optic at 40 Hz with energy densities at the target surface of 20-80 J/cm2 per pulse. The goal of the study was to establish the ideal dosimetry for removing bone and PMMA with minimum trauma to the adjacent tissue. Histology revealed that the 308 nm laser effectively removed bone leaving a thermal damage zone of only 2-3 microns in the remaining tissue. Increasing the energy per pulse gave correspondingly larger and deeper cuts with increasing zones of thermal damage. The excimer laser was also effective in the ablation of PMMA, creating craters in the substrate with a thermal damage zone of 10-40 microns. The debris from both substrates was evaluated.

  12. Direct Pulmonary Vein Ablation with Stenosis Prevention Therapy

    PubMed Central

    DeSimone, Christopher V.; Holmes, David R.; Ebrille, Elisa; Syed, Faisal F.; Ladewig, Dorothy J.; Mikell, Susan B.; Powers, Joanne; Suddendorf, Scott H.; Gilles, Emily J.; Danielsen, Andrew J.; Hodge, David O.; Kapa, Suraj; Asirvatham, Samuel J.

    2015-01-01

    Introduction The dominant location of electrical triggers for initiating atrial fibrillation (AF) originates from the muscle sleeves inside pulmonary veins (PVs). Currently, radiofrequency ablation (RFA) is performed outside of the PVs to isolate, rather than directly ablate these tissues, due to the risk of intraluminal PV stenosis. Methods In 4 chronic canine experiments, we performed direct PV muscle sleeve RFA ± post-ablation drug-coated balloon (DCB) treatment with paclitaxel/everolimus. Of the 4 PVs, 2 PVs were ablated and treated with DCB, 1 PV was ablated without DCB treatment (positive control), and 1 PV was left as a negative control. Local electrograms were assessed in PVs for near-field signals and were targeted for ablation. After 12-14 weeks survival, PVs were interrogated for absence of near-field PV potentials, and each PV was assessed for stenosis. Results All canines survived the study period without cardiorespiratory complications, and remained ambulatory. In all canines, PVs that were ablated and treated with DCB remained without any significant intraluminal stenosis. In contrast, PVs that were ablated and not treated with DCB showed near or complete intraluminal stenosis. At terminal study, PV potentials remained undetectable. A blinded, histologic analysis demonstrated that ablated PVs without DCB treatment had extensive thrombus, fibrin, mineralization, and elastin disruption. Conclusion Our chronic canine data suggest that direct PV tissue ablation without subsequent stenosis is feasible with the use of post-ablation DCBs. PMID:26075706

  13. Electromagnetic measurement and modeling techniques for microwave ablation probes.

    PubMed

    Brannan, Joseph D

    2009-01-01

    Broadband scattering parameter measurement of a commercially available microwave ablation probe over the course of a 10 minute 45 Watt ablation cycle within ex-vivo bovine liver tissue is performed. Measurement results are compared to finite difference time domain simulation of the probe in non-ablated and fully ablated tissue geometries. Measurement and simulation results agree well from 0-3 GHz demonstrating the accuracy of a multi-compartmental ablation geometry modeling technique. The electromagnetic modeling technique presented in this paper introduces a useful design tool for optimizing microwave ablation probes without the need for multi-physics simulation packages. The relevance of tissue complex permittivity change with temperature to microwave ablation probe performance is discussed.

  14. Current status of thermal ablation treatments for lung malignancies.

    PubMed

    Dupuy, Damian E; Shulman, Maria

    2010-09-01

    About 75% of lung cancer patients are not surgical candidates, either due to advanced disease or medical comorbidities. Furthermore, conventional treatments that can be offered to these patients are beneficial only to a small percentage of them. Thermal ablation is a minimally invasive treatment that is commonly used in this group of patients, and which has shown promising results. Currently, the most widely used ablation techniques in the treatment of lung malignancies are radiofrequency ablation (RFA), microwave ablation, and cryoablation. Although the most studied technique is RFA, recent studies with microwave ablation and cryoablation have shown some advantages over RFA. This article reviews the application of thermal ablation in the thorax, including patient selection, basic aspects of procedure technique, imaging follow-up, treatment outcomes, and comparison of ablation techniques.

  15. Superselective Particle Embolization Enhances Efficacy of Radiofrequency Ablation: Effects of Particle Size and Sequence of Action

    SciTech Connect

    Tanaka, Toshihiro; Isfort, Peter; Braunschweig, Till Westphal, Saskia; Woitok, Anna; Penzkofer, Tobias Bruners, Philipp; Kichikawa, Kimihiko; Schmitz-Rode, Thomas Mahnken, Andreas H.

    2013-06-15

    Purpose. To evaluate the effects of particle size and course of action of superselective bland transcatheter arterial embolization (TAE) on the efficacy of radiofrequency ablation (RFA). Methods. Twenty pigs were divided into five groups: group 1a, 40-{mu}m bland TAE before RFA; group 1b, 40-{mu}m bland TAE after RFA; group 2a, 250-{mu}m bland TAE before RFA; group 2b, 250-{mu}m bland TAE after RFA and group 3, RFA alone. A total of 40 treatments were performed with a combined CT and angiography system. The sizes of the treated zones were measured from contrast-enhanced CTs on days 1 and 28. Animals were humanely killed, and the treated zones were examined pathologically. Results. There were no complications during procedures and follow-up. The short-axis diameter of the ablation zone in group 1a (mean {+-} standard deviation, 3.19 {+-} 0.39 cm) was significantly larger than in group 1b (2.44 {+-} 0.52 cm; P = 0.021), group 2a (2.51 {+-} 0.32 cm; P = 0.048), group 2b (2.19 {+-} 0.44 cm; P = 0.02), and group 3 (1.91 {+-} 0.55 cm; P < 0.001). The greatest volume of ablation was achieved by performing embolization with 40-{mu}m particles before RFA (group 1a; 20.97 {+-} 9.65 cm{sup 3}). At histology, 40-{mu}m microspheres were observed to occlude smaller and more distal arteries than 250-{mu}m microspheres. Conclusion. Bland TAE is more effective before RFA than postablation embolization. The use of very small 40-{mu}m microspheres enhances the efficacy of RFA more than the use of larger particles.

  16. Infusion of hypertonic saline into the lung parenchyma during radiofrequency ablation of the lungs with multitined expandable electrodes: results using a porcine model.

    PubMed

    Iishi, Tatsuhiko; Hiraki, Takao; Mimura, Hidefumi; Gobara, Hideo; Kurose, Taichi; Fujiwara, Hiroyasu; Sakurai, Jun; Yanai, Hiroyuki; Yoshino, Tadashi; Kanazawa, Susumu

    2009-06-01

    The present study was performed to clarify the effect of hypertonic saline infusion into the lung parenchyma on radiofrequency ablation (RFA) of the lungs. A total of 20 ablation zones were created in 3 pigs. The ablation zones were divided into 3 groups. Group 1 (n=6) consisted of ablation zones created by applying smaller radiofrequency (RF) power without saline infusion; group 2 (n=5) zones were created by applying greater RF power without saline infusion;and group 3 (n=9) zones were created by applying greater RF power with saline infusion. The techniques of saline infusion included administration of hypertonic saline 1 ml before RFA, followed by continuous administration at a rate of 1 ml/min during the first 2 min after the initiation of RFA. The ablation parameters and coagulation necrosis volumes were compared among the groups. Group 3 had a tendency toward smaller mean impedance than group 1 (p=0.059) and group 2 (p=0.053). Group 3 showed significantly longer RF application time than group 2 (p=0.004) and significantly greater maximum RF power than group 1 (p=0.001) and group 2 (p=0.004). Group 3 showed significantly larger coagulation necrosis volume (mean, 1,421mm3) than group 2 (mean, 858 mm3, p=0.039) and had a tendency toward larger necrosis volume than group 1 (mean, 878 mm3, p=0.077). Although this small study had limited statistical power, hypertonic saline infusion during RFA appeared to enlarge coagulation necrosis of the lung parenchyma.

  17. Preparation of oriented silicon carbide films by laser ablation of ceramic silicon carbide targets

    NASA Astrophysics Data System (ADS)

    Rimai, L.; Ager, R.; Logothetis, E. M.; Weber, W. H.; Hangas, J.

    1991-10-01

    Stoichiometric films of SiC, 60-150 nm thick, were deposited on 001-line and 111-line Si wafers by laser ablation of ceramic stoichiometric SiC targets. Films grown at substrate temperatures above 1050 C show orientation epitaxial to the Si substrate along the film normal. Depending on the deposition conditions, the oriented crystalline dimension along this direction ranges from 20 nm up to the film thickness. The crystallite dimensions in the film plane range from 20 to 70 nm. Raman spectra indicate that the films often contain material other than crystalline SiC. Some of that is in the form of small (3-5 nm) graphitic inclusions.

  18. [Using 3.0 T MR to dynamically observe ablated lung tumors after percutaneous cryotherapy therapy].

    PubMed

    Li, J; Qu, J R; Zhang, H K; Xiao, J C; Jiang, L N; Zhao, Y; Li, H L

    2016-09-20

    Objective: To initially explore MRI features and its changing trends including of lung tumors after Argon-Helium cryoablation therapy, and enhance the recognition of MR findings of lung tumors postcryoablation. Methods: Twenty-three cases of patients with twenty six nodules of pulmonary malignance who received Argon-Helium cryoablation therapy in Henan Cancer Hospital from July 2014 to January 2016 were enrolled.All patients underwent unenhanced and dynamic contrast-enhanced MRI scans at pre-and 1-day, 1-week, 1-, 3-, 6-, 12-month postcryoablation. Two radiologists independently reviewed MRI images, signal intensity in the ablated zone on T1WI and T2WI were assessed by a 5-point scale.The changing trends of size and signal intensity with time were showed by time-maximum diameter and time-score curve.Time-signal intensity curves based on dynamic enhanced sequence were also performed. Results: Typical MRI findings includes: heterogeneous signal intensity on both T1WI and T2WI at 1-day postcryoablation(26/26, 100%). Hyper-intense on T1WI(22/26, 84.6%) and T2WI(17/26, 65.4%) with a hypo-intense rim at 1-week postcryoablation.Decreasing signal intensity on T1WI(17/26, 65.4%) and increasing signal intensity on T2WI(22/26, 84.6%) at 1-month.Signal intensity declined to the level of muscle on both T1WI(18/26, 69.2%) and T2WI(19/26, 73.1%) at 3-month, nineteen ablated zone turned into patchy shape(19/26, 73.1%). The maximum diameter was largest at 1-day and gradually shrunk with time. The mean score value toped at 1-week and gradually decreased. A straight line type without definite enhancement was found from 1-day to 1-month postcryoablation, an inflow curve with a mild delayed enhancement was seen from 3- to 12- month. Totally 4 recurrence (4/26, 15.4%) all occurred at 3-month and were lack of a complete hypo-intense rim at 1-week postcryoablation. Conclusion: MRI findings of lung tumors postcryoablation are characteristic, a complete hypo-intense rim at 1-week is helpful

  19. Focused ion beam imaging of laser ablation sub-surface effects on layered materials

    NASA Astrophysics Data System (ADS)

    Téllez, Helena; Vadillo, José M.; Chater, Richard J.; Laserna, J. Javier; McPhail, David S.

    2008-12-01

    The focussed ion beam (FIB) represents a useful and versatile tool to allow visualization of sub-surface features related to the thermal effects of laser-target interaction with high spatial resolution. The possibility of performing a contamination-free milling process on specific sample locations provides significant advantage over conventional metallurgical procedures involving cutting and polishing. In particular, the direct visualization of the thermal features occurring at fluences below the phase explosion allows a deeper understanding of the extension of the laser heat-affected zone, the sub-surface alloying processes and additional features related to the photo-thermal mechanism of laser ablation.

  20. Numerical study and optimization of interstitial antennas for microwave ablation therapy

    NASA Astrophysics Data System (ADS)

    Komarov, Vyacheslav V.

    2014-10-01

    Electromagnetic and thermal characteristics of coaxial monopole antennas of 2.45 GHz and 24.125 GHz for microwave ablation of malignant tumors are investigated. Microwave heating processes in an interaction domain (biological tissue) are described by the coupled electromagnetic and heat transfer problem, which was solved numerically in the present study. Proposed applicators provide reducing of reflected power and localized distribution of temperature in the near-field zone. Different mathematical models are used to optimize the antennas sizes and simulate heating patterns.

  1. Radiative ablation of disks around massive stars

    NASA Astrophysics Data System (ADS)

    Kee, Nathaniel Dylan

    Hot, massive stars (spectral types O and B) have extreme luminosities (10. 4 -10. 6 L?) that drive strong stellar winds through UV line-scattering.Some massive stars also have disks, formed by either decretion from the star (as in the rapidly rotating "Classical Be stars"), or accretion during the star's formation. This dissertation examines the role of stellar radiation in driving (ablating) material away from these circumstellar disks. A key result is that the observed month to year decay of Classical Be disks can be explained by line-driven ablation without, as previously done, appealing to anomalously strong viscous diffusion. Moreover, the higher luminosity of O stars leads to ablation of optically thin disks on dynamical timescales of order a day, providing a natural explanation for the lack of observed Oe stars. In addition to the destruction of Be disks, this dissertation also introduces a model for their formation by coupling observationally inferred non-radial pulsation modes and rapid stellar rotation to launch material into orbiting Keplerian disks of Be-like densities. In contrast to such Be decretion disks, star-forming accretion disks are much denser and so are generally optically thick to continuum processes. To circumvent the computational challenges associated with radiation hydrodynamics through optically thick media, we develop an approximate method for treating continuum absorption in the limit of geometrically thin disks. The comparison of ablation with and without continuum absorption shows that accounting for disk optical thickness leads to less than a 50% reduction in ablation rate, implying that ablation rate depends mainly on stellar properties like luminosity. Finally, we discuss the role of "thin-shell mixing" in reducing X-rays from colliding wind binaries. Laminar, adiabatic shocks produce well understood X-ray emission, but the emission from radiatively cooled shocks is more complex due to thin-shell instabilities. The parameter

  2. Temperature profiles of 980- and 1,470-nm endovenous laser ablation, endovenous radiofrequency ablation and endovenous steam ablation.

    PubMed

    Malskat, W S J; Stokbroekx, M A L; van der Geld, C W M; Nijsten, T E C; van den Bos, R R

    2014-03-01

    Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures.

  3. Near-critical phase explosion promoting breakdown plasma ignition during laser ablation of graphite.

    PubMed

    Ionin, A A; Kudryashov, S I; Seleznev, L V

    2010-07-01

    Removal rate, air shock, and ablative recoil pressure parameters were measured as a function of laser intensity I(peak) during nanosecond laser ablation of graphite. Surface vaporization of molten graphite at low intensities I(peak)<0.15 GW/cm(2) was observed to transform into its near-critical phase explosion (intense homogeneous boiling) at the threshold intensity I(PE)≈0.15 GW/cm(2) in the form of a drastic, correlated rise of removal rate, air shock, and ablative recoil pressure magnitudes. Just above this threshold (I(peak)≥0.25 GW/cm(2)), the explosive mass removal ended up with saturation of the removal rate, much slower increase of the air and recoil pressure magnitudes, and appearance of a visible surface plasma spark. In this regime, the measured far-field air shock pressure amplitude exhibits a sublinear dependence on laser intensity (∝I(peak)(4/9)), while the source plasma shock pressure demonstrates a sublinear trend (∝I(peak)(3/4)), both indicating the subcritical character of the plasma. Against expectations, in this regime the plasma recoil pressure increases versus I(peak) superlinearly (∝I(peak)(1.1)), rather than sublinearly (∝I(peak)(3/4)), with the mentioned difference related to the intensity-dependent initial spatial plasma dimensions within the laser waist on the graphite surface and to the plasma formation time during the heating laser pulse (overall, the pressure source effect). The strict coincidence of the phase explosion, providing high (kbar) hydrodynamic pressures of ablation products, and the ignition of ablative laser plasma in the carbon plume may indicate the ablative pressure-dependent character of the underlying optical breakdown at the high plume pressures, initiating the plasma formation. The experimental data evidence that the spatiotemporal extension of the plasma in the laser plume and ambient air during the heating laser pulse is supported by fast lateral electron and radiative heat conduction (laser

  4. The Dimensions of Creative Prose

    ERIC Educational Resources Information Center

    Miller, Melvin H.

    1975-01-01

    The thesis in this paper centered around the meaning of "effective" speaking and "effective" writing. The dimensions of effective prose are analyzed as one method of determining what is involved. (Author/RK)

  5. Fourier dimension of random images

    NASA Astrophysics Data System (ADS)

    Ekström, Fredrik

    2016-10-01

    Given a compact set of real numbers, a random C^{m + α}-diffeomorphism is constructed such that the image of any measure concentrated on the set and satisfying a certain condition involving a real number s, almost surely has Fourier dimension greater than or equal to s / (m + α). This is used to show that every Borel subset of the real numbers of Hausdorff dimension s is C^{m + α}-equivalent to a set of Fourier dimension greater than or equal to s / (m + α ). In particular every Borel set is diffeomorphic to a Salem set, and the Fourier dimension is not invariant under Cm-diffeomorphisms for any m.

  6. Radiation reaction in various dimensions

    NASA Astrophysics Data System (ADS)

    Gal'Tsov, Dmitri V.

    2002-07-01

    We discuss the radiation reaction problem for an electric charge moving in flat space-time of arbitrary dimensions. It is shown that four is the unique dimension where a local differential equation exists accounting for the radiation reaction and admitting a consistent mass renormalization (the Lorentz-Dirac equation). In odd dimensions Huygens's principle does not hold, and, as a result, the radiation reaction force depends on the whole past history of a charge (radiative tail). We show that the divergence in the tail integral can be removed by the mass renormalization only in the 2+1 theory. In even dimensions higher than four, divergences cannot be removed by the mass renormalization.

  7. The absorption and radiation of a tungsten plasma plume during nanosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Moscicki, T.; Hoffman, J.; Chrzanowska, J.

    2015-10-01

    In this paper, the effect of absorption of the laser beam and subsequent radiation on the dynamics of a tungsten plasma plume during pulsed laser ablation is analyzed. Different laser wavelengths are taken into consideration. The absorption and emission coefficients of tungsten plasma in a pressure range of 0.1-100 MPa and temperature up to 70 000 K are presented. The shielding effects due to the absorption and radiation of plasma may have an impact on the course of ablation. The numerical model that describes the tungsten target heating and the formation of the plasma and its expansion were made for 355 nm and 1064 nm wavelengths of a Nd:YAG laser. The laser beam with a Gaussian profile was focused to a spot size of 0.055 mm2 with a power density of 1 × 109 W/cm2 (10 ns full width half maximum pulse duration). The plasma expands into air at ambient pressure of 1 mPa. The use of the shorter wavelength causes faster heating of the target, thus the higher ablation rate. The consequences of a higher ablation rate are slower expansion and smaller dimensions of the plasma plume. The higher plasma temperature in the case of 1064 nm is due to the lower density and lower plasma radiation. In the initial phase of propagation of the plasma plume, when both the temperature and pressure are very high, the dominant radiation is emission due to photo-recombination. However, for a 1064 nm laser wavelength after 100 ns of plasma expansion, the radiation of the spectral lines is up to 46.5% of the total plasma radiation and should not be neglected.

  8. The absorption and radiation of a tungsten plasma plume during nanosecond laser ablation

    SciTech Connect

    Moscicki, T. Hoffman, J.; Chrzanowska, J.

    2015-10-15

    In this paper, the effect of absorption of the laser beam and subsequent radiation on the dynamics of a tungsten plasma plume during pulsed laser ablation is analyzed. Different laser wavelengths are taken into consideration. The absorption and emission coefficients of tungsten plasma in a pressure range of 0.1–100 MPa and temperature up to 70 000 K are presented. The shielding effects due to the absorption and radiation of plasma may have an impact on the course of ablation. The numerical model that describes the tungsten target heating and the formation of the plasma and its expansion were made for 355 nm and 1064 nm wavelengths of a Nd:YAG laser. The laser beam with a Gaussian profile was focused to a spot size of 0.055 mm{sup 2} with a power density of 1 × 10{sup 9 }W/cm{sup 2} (10 ns full width half maximum pulse duration). The plasma expands into air at ambient pressure of 1 mPa. The use of the shorter wavelength causes faster heating of the target, thus the higher ablation rate. The consequences of a higher ablation rate are slower expansion and smaller dimensions of the plasma plume. The higher plasma temperature in the case of 1064 nm is due to the lower density and lower plasma radiation. In the initial phase of propagation of the plasma plume, when both the temperature and pressure are very high, the dominant radiation is emission due to photo-recombination. However, for a 1064 nm laser wavelength after 100 ns of plasma expansion, the radiation of the spectral lines is up to 46.5% of the total plasma radiation and should not be neglected.

  9. Atrial conduction delay predicts atrial fibrillation in paroxysmal supraventricular tachycardia patients after radiofrequency catheter ablation.

    PubMed

    Xu, Zhen-Xing; Zhong, Jing-Quan; Zhang, Wei; Yue, Xin; Rong, Bing; Zhu, Qing; Zheng, Zhaotong; Zhang, Yun

    2014-06-01

    This study aimed to assess whether intra- and inter-atrial conduction delay could predict atrial fibrillation (AF) for paroxysmal supraventricular tachycardia (PSVT) patients after successful treatment by radiofrequency catheter ablation (RFCA). Echocardiography examination was performed on 524 consecutive PSVT patients (15 patients were excluded). Left atrial dimension, right atrial diameter and intra- and inter-atrial conduction delay were measured before ablation. Patients were divided into group A (n = 32): occurrence of AF after the ablation and group B (n = 477): remained in sinus rhythm during follow-up. Receiver operating characteristic (ROC) curve analysis was performed to estimate the predictive value of intra- and inter-atrial conduction delay. Both intra- and inter-atrial conduction delay were higher in group A than in group B (4.79 ± 0.30 msec vs. 4.56 ± 0.32 msec; 21.98 ± 1.32 msec vs. 20.01 ± 1.33; p < 0.05). Binary logistic regression analysis showed that intra- and inter-atrial conduction were significant influential factors for the occurrence of AF (odds ratio [OR] = 13.577, 95% confidence interval [CI], 3.469-48.914; OR = 2.569, 95% CI, 1.909-3.459, p < 0.05). The ROC cure analysis revealed that intra-atrial conduction delay ≥ 4.45 msec and inter-atrial conduction delay ≥ 20.65 were the most optimal cut-off value for predicting AF in PSVT patients after RFCA. In conclusion, this is the first study to show that the intra- and inter-atrial conduction delay could effectively predict AF in post-ablation PSVT patients.

  10. Phenomenology of universal extra dimensions

    SciTech Connect

    Kong, Kyoungchul; Matchev, Konstantin T.; /Florida U.

    2006-10-01

    In this proceeding, the phenomenology of Universal Extra Dimensions (UED), in which all the Standard Model fields propagate, is explored. We focus on models with one universal extra dimension, compactified on an S{sub 1}/Z{sub 2} orbifold. We revisit calculations of Kaluza-Klein (KK) dark matter without an assumption of the KK mass degeneracy including all possible coannihilations. We then contrast the experimental signatures of low energy supersymmetry and UED.

  11. Timbre Dimensions for Musical Control

    NASA Astrophysics Data System (ADS)

    Giese, Gregory Roy

    This dissertation addresses the folowing question: Given the technologies to develop and implement any kind of sound generating and controlling device, what will the instrument designer, the composer, and the performer need to know in order to more fully utilize the dimensions of timbre in music and musical performance? This question is approached from the standpoint of music theory. Definitions of timbre and a few examples of related physical and perceptual research are reviewed. Included is a discussion of the essential elements of musical control and of intelligent organization of sound in music. This discussion raises more questions than can be answered simply. It is an attempt to unravel the nature of sound clues and sound qualities as they convey sound identities and musical gesture. A theoretical simplification of sound dimensions for musical use is proposed. Sounds which can be sustained indefinitely consist of steady-state acoustical dimensions. These dimensions rely upon the perceptual phenomenon of simultaneous fusion (synance). Sounds which can not be sustained indefinitely consist of transitions. Transitions may cause successive fusion (sonance). The discussion of steady-state and transition dimensions includes a review of a few informal experiments. This work reveals problems that will influence the musical use of timbre dimensions. It also leads to a theory for the organization and control of timbre dimensions in music. Among the timbre dimensions discussed are: spectral envelope, harmonic content, brightness, phase, inharmonicity, aperiodicity, and temporal transitions. Questions are raised regarding the perception of harmonic content. The effect of register on perception of tones consisting of from two to nine partials is explored and discussed. The size of interval between partials determines a unique quality. This is most apparent with tones consisting of only two or three partials (dions or trions).

  12. The Sirens of Eleven Dimensions

    NASA Astrophysics Data System (ADS)

    Ramond, Pierre

    While most theorists are tied to the mast of four dimensions, some have found it irresistible to speculate about eleven dimensions, the domain of M-theory. We outline a program which starts from the light-cone description of supergravity, and tracks its divergences to suggest the existence of an infinite component theory which in the lightcone relies on the coset F4/SO(9), long known to be linked to the Exceptional Jordan Algebra

  13. The mechanism of lesion formation by focused ultrasound ablation catheter for treatment of atrial fibrillation

    NASA Astrophysics Data System (ADS)

    Sinelnikov, Y. D.; Fjield, T.; Sapozhnikov, O. A.

    2009-10-01

    The application of therapeutic ultrasound for the treatment of atrial fibrillation (AF) is investigated. The results of theoretical and experimental investigation of ultrasound ablation catheter are presented. The major components of the catheter are the high power cylindrical piezoelectric element and parabolic balloon reflector. Thermal elevation in the ostia of pulmonary veins is achieved by focusing the ultrasound beam in shape of a torus that transverses the myocardial tissue. High intensity ultrasound heating in the focal zone results in a lesion surrounding the pulmonary veins that creates an electrical conduction blocks and relief from AF symptoms. The success of the ablation procedure largely depends on the correct choice of reflector geometry and ultrasonic power. We present a theoretical model of the catheter’s acoustic field and bioheat transfer modeling of cardiac lesions. The application of an empirically derived relation between lesion formation and acoustic power is shown to correlate with the experimental data. Developed control methods combine the knowledge of theoretical acoustics and the thermal lesion formation simulations with experiment and thereby establish dosimetry that contributes to a safe and effective ultrasound ablation procedure.

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

    PubMed Central

    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. PMID:23820168

  15. A two-dimensional time domain near zone to far zone transformation

    NASA Technical Reports Server (NTRS)

    Luebbers, Raymond J.; Ryan, Deirdre; Beggs, John H.; Kunz, Karl S.

    1991-01-01

    A time domain transformation useful for extrapolating three dimensional near zone finite difference time domain (FDTD) results to the far zone was presented. Here, the corresponding two dimensional transform is outlined. While the three dimensional transformation produced a physically observable far zone time domain field, this is not convenient to do directly in two dimensions, since a convolution would be required. However, a representative two dimensional far zone time domain result can be obtained directly. This result can then be transformed to the frequency domain using a Fast Fourier Transform, corrected with a simple multiplicative factor, and used, for example, to calculate the complex wideband scattering width of a target. If an actual time domain far zone result is required, it can be obtained by inverse Fourier transform of the final frequency domain result.

  16. Ablation of steel using picosecond laser pulses in burst mode

    NASA Astrophysics Data System (ADS)

    Lickschat, Peter; Demba, Alexander; Weissmantel, Steffen

    2017-02-01

    Results obtained in picosecond laser processing of steel applying the burst mode are presented. Using the burst mode, pulse trains, i.e., bursts, consisting of a number of picosecond pulses with an inter-pulse delay of 12.5 ns and 10 ps pulse duration are applied for material processing. Small cavities with sizes in the range of the laser beam diameter made by single-burst ablation are compared to quadratic cavities of 0.5 × 0.5 mm² produced by multiburst ablation and simultaneous scanning of the laser beam across the steel sample surface. The ablated volume per pulse within the burst was calculated either from the ablated volume per burst or from the ablation depth of the quadratic cavities. With the second to fourth pulses in the bursts, a reduction of the ablated volume per pulse in comparison with the first pulse in the bursts (i.e., to the use of single pulses) was found for both single- and multiburst ablation, which is assumed to be due to plasma shielding. By contrast, the ablated volume per pulse within the bursts increases for the fifth to eighth pulses. Heat accumulation effect and the influence of the heated plasma can be assumed to be the reason for these higher ablation rates. SEM micrographs also show that there is a higher melt ejection out of the laser processed area. This is indicated by the formation of bulges about the ablated area.

  17. Automated planning of ablation targets in atrial fibrillation treatment

    NASA Astrophysics Data System (ADS)

    Keustermans, Johannes; De Buck, Stijn; Heidbüchel, Hein; Suetens, Paul

    2011-03-01

    Catheter based radio-frequency ablation is used as an invasive treatment of atrial fibrillation. This procedure is often guided by the use of 3D anatomical models obtained from CT, MRI or rotational angiography. During the intervention the operator accurately guides the catheter to prespecified target ablation lines. The planning stage, however, can be time consuming and operator dependent which is suboptimal both from a cost and health perspective. Therefore, we present a novel statistical model-based algorithm for locating ablation targets from 3D rotational angiography images. Based on a training data set of 20 patients, consisting of 3D rotational angiography images with 30 manually indicated ablation points, a statistical local appearance and shape model is built. The local appearance model is based on local image descriptors to capture the intensity patterns around each ablation point. The local shape model is constructed by embedding the ablation points in an undirected graph and imposing that each ablation point only interacts with its neighbors. Identifying the ablation points on a new 3D rotational angiography image is performed by proposing a set of possible candidate locations for each ablation point, as such, converting the problem into a labeling problem. The algorithm is validated using a leave-one-out-approach on the training data set, by computing the distance between the ablation lines obtained by the algorithm and the manually identified ablation points. The distance error is equal to 3.8+/-2.9 mm. As ablation lesion size is around 5-7 mm, automated planning of ablation targets by the presented approach is sufficiently accurate.

  18. Rapid cell-patterning and microfluidic chip fabrication by crack-free CO2 laser ablation on glass

    NASA Astrophysics Data System (ADS)

    Yen, Meng-Hua; Cheng, Ji-Yen; Wei, Cheng-Wey; Chuang, Yung-Chuan; Young, Tai-Horng

    2006-07-01

    This paper uses a widely available CO2 laser scriber (λ = 10.6 µm) to perform the direct-writing ablation of quartz, borofloat and pyrex substrates for the development of microfluidic chips and cell chips. The surface quality of the ablated microchannels and the presence of debris and distortion are examined by scanning electron microscopy, atomic force microscopy and surface profile measurement techniques. The developed laser ablation system provides a versatile and economic approach for the fabrication of glass microfluidic chips with crack-free structures. In the laser writing process, the desired microfluidic patterns are designed using commercial computer software and are then transferred to the laser scriber to ablate the trenches. This process eliminates the requirement for corrosive chemicals and photomasks, and hence the overall microchip development time is limited to less than 24 h. Additionally, since the laser writing process is not limited by the dimensions of a photomask, the microchannels can be written over a large substrate area. The machining capability and versatility of the laser writing system are demonstrated through its application to the fabrication of a borofloat microfluidic chip and the writing of a series of asymmetric trenches in a microwell array. It is shown that the minimum attainable trench width is 95 µm and that the maximum trench depth is 225 µm. The system provides an economic and powerful means of rapid glass microfluidic chip development. A rapid cell-patterning method based on this method is also demonstrated.

  19. Enhancing ablation efficiency in micro structuring using a deformable mirror for beam shaping of ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Smarra, M.; Dickmann, K.

    2016-03-01

    Using ultra-short laser pulses for the generation of microstructures results in a high flexible tool for free form geometries in the micro range. Increasing laser power and repetition rates increase as well the demand of high flexible and efficient process strategies. To increase the ablation efficiency the optimal fluency can be determined, which is a material specific value. By varying the beam shape, the ablation efficiency can be enhanced. In this study a deformable mirror was used to vary the beam shape. This mirror is built by combining a piezo-electric ceramic and a mirror substrate. The ceramic is divided into several segments, which can be controlled independently. This results in a high flexible deformable mirror which influences the beam shape and can be used to vary the spot size or generate line geometries. The ablation efficiency and roughness of small generated cavities were analyzed in this study as well as the dimensions of the cavity. This can be used to optimize process strategies to combine high volume ablation and fine detail generation.

  20. Radiofrequency thermal ablation of hepatocellular carcinoma.

    PubMed

    Allgaier, H P; Galandi, D; Zuber, I; Blum, H E

    2001-01-01

    Hepatocellular carcinoma (HCC) is one of the major malignancies worldwide. Due to advanced or decompensated liver cirrhosis, comorbidity and multicentricity of the tumor lesions, 70-80% of HCC patients are inoperable at the time of diagnosis. Radiofrequency thermal ablation (RFTA) is a new minimally invasive and sage technique for the nonsurgical treatment of HCCs. Similar to other ablation techniques, the treatment strategy depends on several factors, including the patient's clinical status, the stage of liver cirrhosis and of the HCC. RFTA can be performed percutaneously, laparoscopically or after laparotomy. Advanced RFTA equipment, refined techniques of modifying tumor tissue response to RFTA, and combined treatment strategies should lead to better response rates even in larger HCCs.

  1. 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.

  2. Wire ablation scaling in Z pinches

    NASA Astrophysics Data System (ADS)

    Yu, Edmund; Sinars, Daniel; Mehlhorn, Tom; Oliver, Bryan

    2004-11-01

    We investigate the physical processes involved in wire ablation in Z pinches, using a combination of simple 1D steady-state analytic theory (similar in approach to that described in [1]) and simulations of the Z pinch under constant current drive conditions (using the radiation-MHD code ALEGRA-MHD). Of particular interest is the dependence of mass ablation rate on wire mass and drive current. We benchmark our scaling trends against simulations of a recently conducted series of experiments on Sandia National Laboratories' Z accelerator (Albuquerque, NM), in which only the mass of the wire array was varied. [1] V.V. Aleksandrov et al., Plasma Phys. Reports 27, 89 (2001) *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockhead Martin Company for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  3. Laser ablation of gall bladder stones

    NASA Astrophysics Data System (ADS)

    Marafi, M.; Makdisi, Y.; Bhatia, K. S.; Abdulah, A. H.; Kokaj, Y.; Mathew, K.; Quinn, F.; Qabazard, A.

    1999-06-01

    Study of laser interaction with calculi is presented. A system of Nd-Yag and Ho-Yag pulsed lasers were used to produce fluorescence and plasma signals at the stone surface surrounded by saline and bile fluids. Fourth harmonic from Nd-Yag laser was transmitted to the samples by graded UV optical fibres. Gall bladder stones of various compositions were subjected to the high power Ho-Yag laser. Temporal transients and spectral evolution of plasma and fluorescence signals were monitored by a streak camera. A profile of acoustic pressures generated by shock waves was recorded with sensitive hydrophones placed in the surrounding fluids. Ablation threshold, cavitation process and fluorescence dependence on the laser parameters were studied in detail. Potential of stone identification by fluorescence and possible hydrodynamic model for ablation of biological samples is discussed.

  4. Nozzle designs with pitch precursor ablatives

    NASA Technical Reports Server (NTRS)

    Blevins, H. R.; Bedard, R. J.

    1976-01-01

    Recent developments in carbon phenolic ablatives for solid rocket motor nozzles have yielded a pitch precursor carbon fiber offering significant raw material availability and cost saving advantages as compared to conventional rayon precursor material. This paper discusses the results of an experimental program conducted to assess the thermal performance and characterize the thermal properties of pitch precursor carbon phenolic ablatives. The end result of this program is the complete thermal characterization of pitch fabric, pitch mat, hybrid pitch/rayon fabric and pitch mat molding compound. With these properties determined an analytic capability now exists for predicting the thermal performance of these materials in rocket nozzle liner applications. Further planned efforts to verify material performance and analytical prediction procedures through actual rocket motor firings are also discussed.

  5. Ablation of neoplasia by direct current.

    PubMed

    Taylor, T V; Engler, P; Pullan, B R; Holt, S

    1994-08-01

    The application of low-voltage direct electrical current (DEC) has been studied in animals and humans for the ablation of anal condylomata, oesophageal cancer and Kaposi's sarcoma. Twenty milliamps of DEC passed through multiple 6 cm x 1 cm, flat-plate longitudinal electrodes into the squamous mucosa of the oesophagus of healthy dogs for periods ranging from 10 min to 2 h resulted in denudation and necrosis of the oesophageal mucosa at the site of application of the current. In humans, the application of DEC to two patients with benign anal condyloma acuminata, three patients with inoperable obstructing oesophageal cancer and one patient with disseminated Kaposi sarcoma resulted in striking necrosis of tumour tissue that was confirmed by macroscopic and microscopic studies. These initial findings imply promising therapeutic potential for the use of DEC as a simple, effective, safe, low-cost alternative for ablation of neoplasia.

  6. Palliative Radiofrequency Ablation for Recurrent Prostate Cancer

    SciTech Connect

    Jindal, Gaurav; Friedman, Marc; Locklin, Julia Wood, Bradford J.

    2006-06-15

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive local therapy for cancer. Its efficacy is now becoming well documented in many different organs, including liver, kidney, and lung. The goal of RFA is typically complete eradication of a tumor in lieu of an invasive surgical procedure. However, RFA can also play an important role in the palliative care of cancer patients. Tumors which are surgically unresectable and incompatible for complete ablation present the opportunity for RFA to be used in a new paradigm. Cancer pain runs the gamut from minor discomfort relieved with mild pain medication to unrelenting suffering for the patient, poorly controlled by conventional means. RFA is a tool which can potentially palliate intractable cancer pain. We present here a case in which RFA provided pain relief in a patient with metastatic prostate cancer with pain uncontrolled by conventional methods.

  7. Particle analysis using laser ablation mass spectroscopy

    DOEpatents

    Parker, Eric P.; Rosenthal, Stephen E.; Trahan, Michael W.; Wagner, John S.

    2003-09-09

    The present invention provides a method of quickly identifying bioaerosols by class, even if the subject bioaerosol has not been previously encountered. The method begins by collecting laser ablation mass spectra from known particles. The spectra are correlated with the known particles, including the species of particle and the classification (e.g., bacteria). The spectra can then be used to train a neural network, for example using genetic algorithm-based training, to recognize each spectra and to recognize characteristics of the classifications. The spectra can also be used in a multivariate patch algorithm. Laser ablation mass specta from unknown particles can be presented as inputs to the trained neural net for identification as to classification. The description below first describes suitable intelligent algorithms and multivariate patch algorithms, then presents an example of the present invention including results.

  8. [Atrial fibrillation ablation: application of nurse methodology].

    PubMed

    Ramos-González-Serna, Amelia; Mateos-García, M Dolores

    2011-01-01

    Ablation of pulmonary veins for treatment of atrial fibrillation involves applying radiofrequency energy wave by a catheter that causes a circumferential lesion to achieve electrical isolation and voltage drop in the interior. It is mainly applied when there is resistance to treatment and recurrence of symptoms affecting the quality of life of patients. The nurse is an important part of the multidisciplinary team who care for patients who undergo this procedure. The provision of comprehensive nursing care should include nursing procedures prior to, during, and after treatment to ensure the careful and systematic quality required. The aims of this article are: to provide specialised knowledge on the procedure of atrial fibrillation ablation, to describe the preparation of the electrophysiology laboratory, analyse nursing care and develop a standardized care plan for patients on whom this procedure is performed using the NANDA (North American Nursing Association) taxonomy and NIC (Nursing Intervention Classification).

  9. Pulmonary radiofrequency ablation (Part 1): current state.

    PubMed

    Plasencia Martínez, J M

    2015-01-01

    The risks involved in surgical treatment and conventional radiotherapy in patients with early lung cancer or lung metastases often make these treatments difficult to justify. However, on the other hand, it is also unacceptable to allow these lesions to evolve freely because, left untreated, these neoplasms will usually lead to the death of the patient. In recent years, alternative local therapies have been developed, such as pulmonary radiofrequency ablation, which has proven to increase survival with a minimal risk of complications. There are common recommendations for these treatments, and although the specific indications for using one technique or another have yet to be established, there are clearly defined situations that will determine the outcome of the treatment. It is important to know these situations, because appropriate patient selection is essential for therapeutic success. This article aims to describe the characteristics and constraints of pulmonary radiofrequency ablation and to outline its role in thoracic oncology in light of the current evidence.

  10. Steady State Pyrolysis and Ablation Investigation

    DTIC Science & Technology

    2008-03-31

    and cracking of pyrolysable materials), black box models are used, based on wind tunnel and plasma jet experiments. In particular, interactions between...outgassing species coming from the in-depth decomposition of the organic resin (in the case of pyrolysable materials), carbon species coming from...multiplicity of physical phenomena involved and their potential non-linearities. Pyrolyse and ablation are efficient processes for aerothermal heat

  11. A Review of Laser Ablation Propulsion

    NASA Astrophysics Data System (ADS)

    Phipps, Claude; Bohn, Willy; Lippert, Thomas; Sasoh, Akihiro; Schall, Wolfgang; Sinko, John

    2010-10-01

    Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Sänger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing "Lightcraft" and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important rôle in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

  12. Stability analysis of unsteady ablation fronts

    NASA Astrophysics Data System (ADS)

    Betti, R.; McCrory, R. L.; Verdon, C. P.

    1993-08-01

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  13. Stability analysis of unsteady ablation fronts

    SciTech Connect

    Betti, R.; McCrory, R.L.; Verdon, C.P. )

    1993-11-08

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  14. Stability analysis of unsteady ablation fronts

    NASA Astrophysics Data System (ADS)

    Betti, R.; McCrory, R. L.; Verdon, C. P.

    1993-11-01

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code orchid.

  15. Stability analysis of unsteady ablation fronts

    SciTech Connect

    Betti, R.; McCrory, R.L.; Verdon, C.P.

    1993-08-01

    The linear stability analysis of unsteady ablation fronts, is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  16. A Review of Laser Ablation Propulsion

    SciTech Connect

    Phipps, Claude; Bohn, Willy; Lippert, Thomas; Sasoh, Akihiro; Schall, Wolfgang; Sinko, John

    2010-10-08

    Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Saenger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing 'Lightcraft' and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important role in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser that is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.

  17. Liver tumor ablation: percutaneous and open approaches.

    PubMed

    Padma, Srikanth; Martinie, John B; Iannitti, David A

    2009-12-15

    The global incidence of liver cancer is greater than a million cases a year. Surgical resection where applicable is still the standard of care for these patients. Various liver-directed regional therapies have been developed in an effort to treat the vast majority of unresectable liver tumors. This article reviews the principles behind various ablation therapies currently available for malignant liver tumors and their outcomes.

  18. Anatomical Ablation Strategy for Noninducible Fascicular Tachycardia.

    PubMed

    Talib, Ahmed Karim; Nogami, Akihiko

    2016-03-01

    The presence of structural heart disease does not exclude fascicular ventricular tachycardia (VT), especially if the VT is verapamil sensitive. An empirical anatomic approach is effective when fascicular VT is noninducible or if diastolic Purkinje potential (P1) cannot be recorded during VT mapping. Pace mapping at the successful ablation site is usually not effective because selective pacing of P1 is difficult and there is an antidromic activation of the proximal P1 potential.

  19. Design Calculations For NIF Convergent Ablator Experiments

    SciTech Connect

    Olson, R E; Hicks, D G; Meezan, N B; Callahan, D A; Landen, O L; Jones, O S; Langer, S H; Kline, J L; Wilson, D C; Rinderknecht, H; Zylstra, A; Petrasso, R D

    2011-10-25

    The NIF convergent ablation tuning effort is underway. In the early experiments, we have discovered that the design code simulations over-predict the capsule implosion velocity and shock flash rhor, but under-predict the hohlraum x-ray flux measurements. The apparent inconsistency between the x-ray flux and radiography data implies that there are important unexplained aspects of the hohlraum and/or capsule behavior.

  20. Exploring the potential of Multiphoton Laser Ablation Lithography (MP-LAL) as a reliable technique for sub-50nm patterning

    NASA Astrophysics Data System (ADS)

    Manouras, Theodoros; Angelakos, Evangelos; Vamvakaki, Maria; Argitis, Panagiotis

    2016-03-01

    In this work, direct-write, high-resolution multiphoton photolithography using doped random methacrylic co-polymer thin films is demonstrated, using a continuous wave ultraviolet (UV) 375 nm diode laser source. The random copolymers are specifically designed for enhancing resolution and addressing issues arising from laser ablation processes, such as the berm-formation around the created holes in the film, which can be accessed by tuning the polymeric material properties including Tg, surface adhesion etc. The methacrylic copolymer is composed of monomers, each of them especially selected to improve individual properties. The material formulations comprise perylene molecules absorbing at the exposure wavelength where the polymeric matrix is transparent. It was found that if the radiation intensity exceeds a certain threshold, the perylene molecules transfer the absorbed light energy to the acrylate polymer matrix leading to polymer degradation and ablation of the exposed areas. The non-linear nature of the light absorption and energy transfer processes resulted in the creation of holes with critical dimensions well below the used wavelength reaching the sub 50 nm domain. Arrays of holes having various dimensions were fabricated in the laser ablation experiments using a directwrite laser system developed specifically for the purposes of this project.

  1. Calcified lesion modeling for excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Scott, Holly A.; Archuleta, Andrew; Splinter, Robert

    2009-06-01

    Objective: Develop a representative calcium target model to evaluate penetration of calcified plaque lesions during atherectomy procedures using 308 nm Excimer laser ablation. Materials and Methods: An in-vitro model representing human calcified plaque was analyzed using Plaster-of-Paris and cement based composite materials as well as a fibrinogen model. The materials were tested for mechanical consistency. The most likely candidate(s) resulting from initial mechanical and chemical screening was submitted for ablation testing. The penetration rate of specific multi-fiber catheter designs and a single fiber probe was obtained and compared to that in human cadaver calcified plaque. The effects of lasing parameters and catheter tip design on penetration speed in a representative calcified model were verified against the results in human cadaver specimens. Results: In Plaster of Paris, the best penetration was obtained using the single fiber tip configuration operating at 100 Fluence, 120 Hz. Calcified human lesions are twice as hard, twice as elastic as and much more complex than Plaster of Paris. Penetration of human calcified specimens was highly inconsistent and varied significantly from specimen to specimen and within individual specimens. Conclusions: Although Plaster of Paris demonstrated predictable increases in penetration with higher energy density and repetition rate, it can not be considered a totally representative laser ablation model for calcified lesions. This is in part due to the more heterogeneous nature and higher density composition of cadaver intravascular human calcified occlusions. Further testing will require a more representative model of human calcified lesions.

  2. Transurethral radio frequency ablation of the prostate

    NASA Astrophysics Data System (ADS)

    Kabalin, John N.

    1996-05-01

    Since 1993, radiofrequency ablation of the prostate has been studied as a potential treatment for symptomatic bladder outlet obstruction due to benign prostatic hyperplasia. Two transurethral radiofrequency delivery systems have been developed to the point of undergoing initial human clinical trials. The TUNATM system involves focal interstitial radiofrequency energy application, while the TURAPYTM system involves a circumferential application of radiofrequency energy to the prostatic urethra via a simple delivery catheter. Experimental studies in animal models and human prostate tissue have demonstrated the nature of radiofrequency induced tissue heating and thermal injury. Observed thermal effects are relatively focused, with steep temperature gradients occurring over a few millimeters from the radiofrequency emission source. This allows precise and focused tissue treatment with little or no danger of injury to surrounding structures. Early human clinical experience in the treatment of benign prostatic hyperplasia has demonstrated efficacy in the relief of voiding symptoms and safety and minimal morbidity associated with this technology. The existing operative approaches are relatively simple. Ongoing development of more versatile delivery systems for radiofrequency ablation of the prostate is expected. Results from larger clinical trials with longer term followup will eventually allow adequate assessment of the role of radiofrequency ablation in the surgical management of benign prostatic hyperplasia.

  3. Thermal Convection on an Ablating Target

    NASA Astrophysics Data System (ADS)

    Mehmedagic, Igbal; Thangam, Siva

    2015-11-01

    Modeling and analysis of thermal convection of a metallic targets subject to radiative flux is of relevance to various manufacturing processes as well as for the development of protective shields. The present work involves the computational modeling of metallic targets subject to high heat fluxes that are both steady and pulsed. Modeling of the ablation and associated fluid dynamics when metallic surfaces are exposed to high intensity pulsed laser fluence at normal atmospheric conditions is considered. The incident energy from the laser is partly absorbed and partly reflected by the surface during ablation and subsequent vaporization of the convecting melt also participates in the radiative exchange. The energy distribution during the process between the bulk and vapor phase strongly depends on optical and thermodynamic properties of the irradiated material, radiation wavelength, and laser pulse intensity and duration. Computational findings based on effective representation and prediction of the heat transfer, melting and vaporization of the targeting material as well as plume formation and expansion are presented and discussed in the context of various ablation mechanisms, variable thermo-physical and optical properties, plume expansion and surface geometry. Funded in part by U. S. Army ARDEC, Picatinny Arsenal, NJ.

  4. Status of the Ablative Laser Propulsion Studies

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Lin, Jun; Cohen, Tinothy; Pakhomov, Andrew V.; Thompson, M. Shane

    2004-01-01

    We present a short review of our laser-propulsion research as well as some of the current results of the Ablative Laser Propulsion (ALP) studies currently underway at the University of Alabama in Huntsville. It has been shown that direct surface ablation of a solid material produces high specific impulse (Isp) at relatively high energy conversion efficiency (20 - 40%). We detail measurements of specific impulse, thrust and coupling coefficients for elemental target materials both with single and with double pulse laser shots. We also present measurements taken using three independent methods for determination of Isp. The three methods produce consistent values from ion time-of-flight technique, impulse measurements and imaging of the expansion front of plasma plume. We present a demonstration of our ALP lightcraft, a small free-flying micro-vehicle that is propelled by ablation. For ALP lightcraft we use a subscale thin shell of nickel replicated over a diamond turned mandrel that produces a highly polished self-focusing, truncated at the focus parabolic mirror. The mass of the lightcraft is 54 mg and it is driven by 100-ps wide, 35-mJ laser pulses at 532 nm wavelength. This is an ongoing research. We also present the latest work on laserdriven micro-thrusters and detail some the near term goals of our program.

  5. Microwave soft tissue ablation (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Clegg, Peter J.; Cronin, Nigel J.

    2005-04-01

    Microsulis, in conjunction with the University of Bath have developed a set of novel microwave applicators for the ablation of soft tissues. These interstitial applicators have been designed for use in open surgical, laparoscopic and percutaneous settings and range in diameter from 2.4 to 7 mm. A 20 mm diameter flat faced interface applicator was developed as an adjunct to the open surgical interstitial applicator and has been applied to the treatment of surface breaking lesions in hepatobiliary surgery. Taken as a complete tool set the applicators are capable of treating a wide range of conditions in a safe and efficacious manner. The modality employs a radiated electromagnetic field at the allocated medical frequency of 2.45 GHz and powers between 30 and 150 Watts. Computer simulations, bench testing, safety and efficacy testing, ex-vivo and in-vivo work plus clinical trials have demonstrated that these systems are capable of generating large volumes of ablation in short times with favourable ablation geometries. Clinical studies have shown very low complication rates with minimal local recurrence. It is considered that this modality offers major advantages over currently marketed products. The technique is considered to be particularly safe as it is quick and there is no passage of current obviating the requirement for grounding pads. Since the microwave field operates primarily on water and all soft tissues with the exception of fat are made up of approximately 70% water the heating pattern is highly predictable making repeatability a key factor for this modality.

  6. [Ablation of idiopathic fascicular ventricular tachycardia].

    PubMed

    Gellér, László; Szilágyi, Szabolcs; Solymossy, Katalin; Srej, Marianna; Zima, Endre; Tahin, Tamás; Merkely, Béla

    2009-08-02

    Idiopathic fascicular ventricular tachycardia is an important and not very rare cardiac arrhythmia with specific electrocardiographic features and therapeutic options. Ventricular tachycardia is characterized by relatively narrow QRS complex and right bundle branch block pattern. The QRS axis depends on which fascicle is involved in the re-entry. Left axis deviation is noted with left posterior fascicular tachycardia and right axis deviation with left anterior fascicular tachycardia. A left septal fascicular tachycardia with normal QRS axis is also possible. Idiopathic fascicular tachycardia is usually seen in individuals without structural heart disease. Response to verapamil is an important feature of fascicular tachycardia. In some cases intravenous adenosine may also terminate the arrhythmia. During electrophysiology study, presystolic or diastolic potentials precede the QRS, presumed to originate from the Purkinje fibers. The potentials can be recorded during sinus rhythm and ventricular tachycardia in many patients with fascicular tachycardia. This potential (so-called Purkinje potential) has been used as a guide to catheter ablation. Correct diagnosis of fascicular tachycardia is very important because catheter ablation is very effective in the treatment of this type of ventricular tachycardia. In this review, we describe three patients with idiopathic ventricular tachycardia and their successful catheter ablation, and summarize the actual knowledge of the diagnosis and management of this special ventricular tachycardia.

  7. Enhanced Tissue Ablation Efficiency with a Mid-Infrared Nonlinear Frequency Conversion Laser System and Tissue Interaction Monitoring Using Optical Coherence Tomography

    PubMed Central

    Kim, Bongkyun; Kim, Dae Yu

    2016-01-01

    We report development of optical parametric oscillator (OPO)-based mid-infrared laser system that utilizes a periodically poled nonlinear crystal pumped by a near-infrared (NIR) laser. We obtained a mid-infrared average output of 8 W at an injection current of 20 A from a quasi-phase-matched OPO using an external cavity configuration. Laser tissue ablation efficiency is substantially affected by several parameters, including an optical fluence rate, wavelength of the laser source, and the optical properties of target tissue. Dimensions of wavelength and radiant exposure dependent tissue ablation are quantified using Fourier domain optical coherence tomography and the ablation efficiency was compared to a non-converted NIR laser system. PMID:27128916

  8. An extended multi-zone combustion model for PCI simulation

    NASA Astrophysics Data System (ADS)

    Kodavasal, Janardhan; Keum, SeungHwan; Babajimopoulos, Aristotelis

    2011-12-01

    Novel combustion modes are becoming an important area of research with emission regulations more stringent than ever before, and with fuel economy being assigned greater importance every day. Homogeneous Charge Compression Ignition (HCCI) and Premixed Compression Ignition (PCI) modes in particular promise better fuel economy and lower emissions in internal combustion engines. Multi-zone combustion models have been popular in modelling HCCI combustion. In this work, an improved multi-zone model is suggested for PCI combustion modelling. A new zoning scheme is suggested based on incorporating the internal energy of formation into an earlier conventional HCCI multi-zone approach, which considers a two-dimensional reaction space defined by equivalence ratio and temperature. It is shown that the added dimension improves zoning by creating more representative zones, and thus reducing errors compared to the conventional zoning approach, when applied to PCI simulation.

  9. Femtosecond laser ablation of cemented carbides: properties and tribological applications

    NASA Astrophysics Data System (ADS)

    Dumitru, G.; Romano, V.; Weber, H. P.; Gerbig, Y.; Haefke, H.; Bruneau, S.; Hermann, J.; Sentis, M.

    Laser ablation with fs laser pulses was performed in air on cobalt cemented tungsten carbide by means of a Ti : sapphire laser (800 nm, 100 fs). Small and moderate fluences (2, 5, 10 J/cm2) and up to 5×104 pulses per irradiated spot were used to drill holes with aspect ratios up to 10. Cross-section cuts from laser-irradiated samples were produced and they were analysed with optical microscopy and SEM. EDX analyses were carried out on selected zones. Quasi-cylindrical holes were found for 2 J/cm2, whereas for 5 and 10 J/cm2 irregular shapes (lobes, bottoms wider than hole entrances) were found to occur after a given number of incident pulses. Layers with modified structure were evidenced at pore walls. SEM revealed a denser structure, while EDX analyses showed uniform and almost similar contents of W, C, and Co in these layers. As a direct application, patterning of coated WC-Co was carried out with 2 J/cm2 and 100 pulses per pore. The resulted surfaces were tribologically tested and these tests revealed an improved friction and wear behaviour.

  10. Repair after nephron ablation reveals limitations of neonatal neonephrogenesis

    PubMed Central

    Tögel, Florian; Freedman, Benjamin S.; Iatrino, Rossella; Grinstein, Mor; Bonventre, Joseph V.

    2017-01-01

    The neonatal mouse kidney retains nephron progenitor cells in a nephrogenic zone for 3 days after birth. We evaluated whether de novo nephrogenesis can be induced postnatally beyond 3 days. Given the long-term implications of nephron number for kidney health, it would be useful to enhance nephrogenesis in the neonate. We induced nephron reduction by cryoinjury with or without contralateral nephrectomy during the neonatal period or after 1 week of age. There was no detectable compensatory de novo nephrogenesis, as determined by glomerular counting and lineage tracing. Contralateral nephrectomy resulted in additional adaptive healing, with little or no fibrosis, but did not also stimulate de novo nephrogenesis. In contrast, injury initiated at 1 week of age led to healing with fibrosis. Thus, despite the presence of progenitor cells and ongoing nephron maturation in the newborn mouse kidney, de novo nephrogenesis is not inducible by acute nephron reduction. This indicates that additional nephron progenitors cannot be recruited after birth despite partial renal ablation providing a reparative stimulus and suggests that nephron number in the mouse is predetermined at birth. PMID:28138555

  11. A study of ablation effects for an axisymmetric electromagnetic accelerator

    SciTech Connect

    Ikuta, K. . Inst. of Plasma Physics)

    1989-01-01

    In order to give the additional forward thrust to the projectile other than the electromagnetic force, the axial symmetric launcher called ablation mass driver (AMD) has been proposed using sequential z pinches in a cylindrical electrode array. The additional driving force originates from the reaction of ablating hot gas from the ablator on the rear of the projectile, since the Joule heating by the high electric current for electromagnetic acceleration is not negligiblly small. The ablated gas becomes plasma which propagates along the field-null line of z pinch, giving the forward thrust to the projectile. A proto type AMD has been built at Texas Tech University in order to see the capabilities of AMD as a launcher, although a study on the effect of ablation will remain as a future work. This paper describes a device of accelerating water blob for the study of ablation effect during acceleration together with the experimental results.

  12. Modeling CO{sub 2} Laser Ablative Impulse with Polymers

    SciTech Connect

    Sinko, John E.; Phipps, Claude R.; Sasoh, Akihiro

    2010-10-08

    Laser ablation vaporization models have usually ignored the spatial dependence of the laser beam. Here, we consider effects from modeling using a Gaussian beam for both photochemical and photothermal conditions. The modeling results are compared to experimental and literature data for CO{sub 2} laser ablation of the polymer polyoxymethylene under vacuum, and discussed in terms of the ablated mass areal density and momentum coupling coefficient. Extending the scope of discussion, laser ablative impulse generation research has lacked a cohesive strategy for linking the vaporization and plasma regimes. Existing models, mostly formulated for ultraviolet laser systems or metal targets, appear to be inappropriate or impractical for applications requiring CO{sub 2} laser ablation of polymers. A recently proposed method for linking the vaporization and plasma regimes for analytical modeling is addressed here along with the implications of its use. Key control parameters are considered, along with the major propulsion parameters needed for laser ablation propulsion modeling.

  13. Influence of the Liquid on Femtosecond Laser Ablation of Iron

    NASA Astrophysics Data System (ADS)

    Kanitz, A.; Hoppius, J. S.; Gurevich, E. L.; Ostendorf, A.

    Ultrashort pulse laser ablation has become a very important industrial method for highly precise material removal ranging from sensitive thin film processing to drilling and cutting of metals. Over the last decade, a new method to produce pure nanoparticles emerged from this technique: Pulsed Laser Ablation in Liquids (PLAL). By this method, the ablation of material by a laser beam is used to generate a metal vapor within the liquid in order to obtain nanoparticles from its recondensation process. It is well known that the liquid significantly alters the ablation properties of the substrate, in our case iron. For example, the ablation rate and crater morphology differ depending on the used liquid. We present our studies on the efficiency and quality of ablated grooves in water, methanol, acetone, ethanol and toluene. The produced grooves are investigated by means of white-light interferometry, EDX and SEM.

  14. Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold

    SciTech Connect

    Upadhyay, Arun K.; Inogamov, Nail A.; Rethfeld, Baerbel; Urbassek, Herbert M.

    2008-07-15

    Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T{sub c}/T{sub tr} of critical to triple-point temperature differs by more than a factor of 4--the values of the ablation threshold energy E{sub abl} normalized to the cohesion energy, {epsilon}{sub abl}=E{sub abl}/E{sub coh}, are surprisingly universal: all are near 0.3 with {+-}30% scattering. The difference in the ratio T{sub c}/T{sub tr} means that for metals the melting threshold {epsilon}{sub m} is low, {epsilon}{sub m}<{epsilon}{sub abl}, while for LJ it is high, {epsilon}{sub m}>{epsilon}{sub abl}. This thermodynamical consideration gives a simple explanation for the difference between metals and LJ. It explains why despite the universality in {epsilon}{sub abl}, metals thermomechanically ablate always from the liquid state. This is opposite to LJ materials, which (near threshold) ablate from the solid state. Furthermore, we find that immediately below the ablation threshold, the formation of large voids (cavitation) in the irradiated material leads to a strong temporary expansion on a very slow time scale. This feature is easily distinguished from the acoustic oscillations governing the material response at smaller intensities, on the one hand, and the ablation occurring at larger intensities, on the other hand. This finding allows us to explain the puzzle of huge surface excursions found in experiments at near-threshold laser irradiation.

  15. Fractal dimension of alumina aggregates grown in two dimensions

    NASA Technical Reports Server (NTRS)

    Larosa, Judith L.; Cawley, James D.

    1992-01-01

    The concepts of fractal geometry are applied to the analysis of 0.4-micron alumina constrained to agglomerate in two dimensions. Particles were trapped at the bottom surface of a drop of a dilute suspension, and the agglomeration process was directly observed, using an inverted optical microscope. Photographs were digitized and analyzed, using three distinct approaches. The results indicate that the agglomerates are fractal, having a dimension of approximately 1.5, which agrees well with the predictions of the diffusion-limited cluster-cluster aggregation model.

  16. Percutaneous ablation therapies of inoperable pancreatic cancer: a systematic review

    PubMed Central

    Ierardi, Anna Maria; Lucchina, Natalie; Bacuzzi, Alessandro; Marco, De Chiara; Bracchi, Elena; Cocozza, Eugenio; Dionigi, Gianlorenzo; Tsetis, Dimitrios; Floridi, Chiara; Carrafiello, Gianpaolo

    2015-01-01

    Initial studies about ablation therapies of the pancreas were associated with significant morbidity and mortality, which limited widespread adoption. Development of techniques with high quality imaging used as guidance improve outcomes reducing complications. Moreover, only few experiences of percutaneous pancreatic ablations are reported. They are performed by very skilled operators in highly specialized centers. This review presents the current status of percutaneous local ablative therapies in the treatment of advanced pancreatic cancer. PMID:26424487

  17. Steerable sheath technology in the ablation of atrial fibrillation.

    PubMed

    Joseph, Jubin; Wong, Kelvin C K; Ginks, Matthew R; Bashir, Yaver; Betts, Timothy R; Rajappan, Kim

    2013-12-01

    Steerable sheaths have been shown to reduce procedure time in the catheter ablation of atrial fibrillation (AF), where catheter positioning and stability is typically challenging. This review critically addresses and highlights the recent developments in design of sheaths used to manipulate the ablation catheter and how these developments may impact on the ablation procedure itself, in particular the likelihood of first-time success. Patents relating to steerable sheaths are reviewed and discussed to gauge potential future developments in this area.

  18. Dimension of fractal basin boundaries

    SciTech Connect

    Park, B.S.

    1988-01-01

    In many dynamical systems, multiple attractors coexist for certain parameter ranges. The set of initial conditions that asymptotically approach each attractor is its basin of attraction. These basins can be intertwined on arbitrary small scales. Basin boundary can be either smooth or fractal. Dynamical systems that have fractal basin boundary show final state sensitivity of the initial conditions. A measure of this sensitivity (uncertainty exponent {alpha}) is related to the dimension of the basin boundary d = D - {alpha}, where D is the dimension of the phase space and d is the dimension of the basin boundary. At metamorphosis values of the parameter, there might happen a conversion from smooth to fractal basin boundary (smooth-fractal metamorphosis) or a conversion from fractal to another fractal basin boundary characteristically different from the previous fractal one (fractal-fractal metamorphosis). The dimension changes continuously with the parameter except at the metamorphosis values where the dimension of the basin boundary jumps discontinuously. We chose the Henon map and the forced damped pendulum to investigate this. Scaling of the basin volumes near the metamorphosis values of the parameter is also being studied for the Henon map. Observations are explained analytically by using low dimensional model map.

  19. Providing plastic zone extrusion

    DOEpatents

    Manchiraju, Venkata Kiran; Feng, Zhili; David, Stan A.; Yu, Zhenzhen

    2017-04-11

    Plastic zone extrusion may be provided. First, a compressor may generate frictional heat in stock to place the stock in a plastic zone of the stock. Then, a conveyer may receive the stock in its plastic zone from the compressor and transport the stock in its plastic zone from the compressor. Next, a die may receive the stock in its plastic zone from the conveyer and extrude the stock to form a wire.

  20. Modelling of Indirect Laser-induced Thin-film Ablation of Epoxy for Local Exposing of Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Emonts, Michael; Fischer, Kai; Schmitt, Stefan; Schares, Richard Ludwig

    Laser radiation is used as enabling technology for intrinsic joining of high-strength CFRP laminates and fiber-reinforced thermoplastic injection moulding compounds by exposure of surface-near carbon fibers. Short-pulsed NIR laser sources represent an acceptable compromise with respect to ablation performance, remote process capability by use of compact 3D scanner and the capability for closed-loop process control. However, using such a laser source means also minimizing heat-affected zones (HAZ). Based on literature research about laser ablation of thin metal films, heat flow at CFRP and thermo-mechanical behavior in FRP by pyrolysis, an analytical model was generated for thin-film ablation of cured epoxy resins at the surface of CFRP laminates by lift-off of resin chips. A comparison between simulation and experimental results confirms the capability of the model to predict the exposure area and the HAZ with deviations below 15%. Threshold fluences for the HAZ (>1 J/cm2) and the resin ablation (>3 J/cm2) have been confirmed.

  1. Comparative study of CO2- and Er:YAG laser ablation of multiple cutaneous neurofibromas in von Recklinghausen's disease.

    PubMed

    Kriechbaumer, Lukas K; Susani, Martin; Kircher, Susanne G; Distelmaier, Klaus; Happak, Wolfgang

    2014-05-01

    With a prevalence of 1 in 3,000 births, neurofibromatosis type 1 (NF1) is one of the most common genetic disorders and is characterized by an uninhibited expansion of neural tissue. Occasionally, severe deformities occur, but frequently considerable cosmetic disfigurement is caused by the development of hundreds of benign cutaneous neurofibromas. The objective of this study was to evaluate the erbium:yttrium-aluminium-garnet (Er:YAG) laser as a therapeutic option for the removal of multiple cutaneous neurofibromas. In this prospective, comparative, in vivo study, 15,580 neurofibromas (44 operations on 21 patients) were removed via electrosurgery, CO2- or Er:YAG laser ablation. In 12 adjacent test areas, we compared the zone of thermal necrosis, the postoperative pain, the time to reepithelialization, the duration of postoperative erythema and the cosmetic outcome of these surgical methods. When compared to electrosurgery and CO2 laser ablation, the Er:YAG laser ablation outperformed the other methods of tumor removal. Rapid healing by second intention as well as the minimal discomfort and scar formation following Er:YAG laser ablation were noted. After 36 months of follow-up, permanent dyspigmentation was rare and hypertrophic scarring was not observed. Er:YAG laser vaporization of multiple cutaneous neurofibromas is a simple and rapid procedure that results in significantly better cosmetic results than CO2 laser treatment or electrosurgery.

  2. Unintended Thermal Injuries from Radiofrequency Ablation: Organ Protection with an Angioplasty Balloon Catheter in an Animal Model

    PubMed Central

    Knuttinen, Martha-Grace; Van Ha, Thuong G.; Reilly, Christopher; Montag, Anthony; Straus, Christopher

    2014-01-01

    Objectives: The aim of this study was to investigate a novel approach of using a balloon catheter as a protective device to separate liver from the diaphragm or nearby bowel during radiofrequency ablation (RFA) of hepatic dome tumors in an animal model. Materials and Methods: All experimental procedures were approved by animal Institutional Review Board. Using a 3 cm RF needle electrode, 70 hepatic ablation zones were created using ultrasound in 7 pigs. 50 lesions were created using balloon interposition between liver and diaphragm; 20 lesions were created using the balloon device interposed posteriorly between liver and bowel. Additional 21 control lesions were performed. Animals were sacrificed immediately; diaphragm and bowel were then visually inspected and sectioned. Diaphragmatic and bowel injury was then classified according to the depth of thickness. Results: Control lesions caused full thickness injury, either to diaphragm or bowel. During ablation of lesions with balloon interposition, there was significantly less diaphragmatic injury, P < 0.001 and less bowel injury, P < 0.01. Conclusion: Using balloon interposition as a protective device has advantages over previous saline infusion or CO2 insufflation, providing a safe way to expand percutaneous RFA of liver tumors located on the undersurface of the diaphragm. In addition, this method may be used in protection of other organs adjacent to areas being ablated. PMID:24678433

  3. Effects of laser ablation on cemented tungsten carbide surface quality

    NASA Astrophysics Data System (ADS)

    Tan, J. L.; Butler, D. L.; Sim, L. M.; Jarfors, A. E. W.

    2010-11-01

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable.

  4. Osteoid Osteoma: Experience with Laser- and Radiofrequency-Induced Ablation

    SciTech Connect

    Gebauer, Bernhard Tunn, Per-Ulf; Gaffke, Gunnar; Melcher, Ingo; Felix, Roland; Stroszczynski, Christian

    2006-04-15

    The purpose of this study was to analyze the clinical outcome of osteoid osteoma treated by thermal ablation after drill opening. A total of 17 patients and 20 procedures were included. All patients had typical clinical features (age, pain) and a typical radiograph showing a nidus. In 5 cases, additional histological specimens were acquired. After drill opening of the osteoid osteoma nidus, 12 thermal ablations were induced by laser interstitial thermal therapy (LITT) (9F Power-Laser-Set; Somatex, Germany) and 8 ablations by radiofrequency ablation (RFA) (RITA; StarBurst, USA). Initial clinical success with pain relief has been achieved in all patients after the first ablation. Three patients had an osteoid osteoma recurrence after 3, 9, and 10 months and were successfully re-treated by thermal ablation. No major complication and one minor complication (sensible defect) were recorded. Thermal ablation is a safe and minimally invasive therapy option for osteoid osteoma. Although the groups are too small for a comparative analysis, we determined no difference between laser- and radiofrequency-induced ablation in clinical outcome after ablation.

  5. Recent Advances in Tumor Ablation for Hepatocellular Carcinoma.

    PubMed

    Kang, Tae Wook; Rhim, Hyunchul

    2015-09-01

    Image-guided tumor ablation for early stage hepatocellular carcinoma (HCC) is an accepted non-surgical treatment that provides excellent local tumor control and favorable survival benefit. This review summarizes the recent advances in tumor ablation for HCC. Diagnostic imaging and molecular biology of HCC has recently undergone marked improvements. Second-generation ultrasonography (US) contrast agents, new computed tomography (CT) techniques, and liver-specific contrast agents for magnetic resonance imaging (MRI) have enabled the early detection of smaller and inconspicuous HCC lesions. Various imaging-guidance tools that incorporate imaging-fusion between real-time US and CT/MRI, that are now common for percutaneous tumor ablation, have increased operator confidence in the accurate targeting of technically difficult tumors. In addition to radiofrequency ablation (RFA), various therapeutic modalities including microwave ablation, irreversible electroporation, and high-intensity focused ultrasound ablation have attracted attention as alternative energy sources for effective locoregional treatment of HCC. In addition, combined treatment with RFA and chemoembolization or molecular agents may be able to overcome the limitation of advanced or large tumors. Finally, understanding of the biological mechanisms and advances in therapy associated with tumor ablation will be important for successful tumor control. All these advances in tumor ablation for HCC will result in significant improvement in the prognosis of HCC patients. In this review, we primarily focus on recent advances in molecular tumor biology, diagnosis, imaging-guidance tools, and therapeutic modalities, and refer to the current status and future perspectives for tumor ablation for HCC.

  6. Nanochemical effects in femtosecond laser ablation of metals

    SciTech Connect

    Vorobyev, A. Y.; Guo, Chunlei

    2013-02-18

    We study chemical energy released from the oxidation of aluminum in multipulse femtosecond laser ablation in air and oxygen. Our study shows that the released chemical energy amounts to about 13% of the incident laser energy, and about 50% of the ablated material is oxidized. The ablated material mass per laser pulse is measured to be on the nanogram scale. Our study indicates that femtosecond laser ablation is capable of inducing nanochemical reactions since the femtosecond laser pulse can controllably produce nanoparticles, clusters, and atoms from a solid target.

  7. Streaked radiography measurements of convergent ablator performance (invited)

    SciTech Connect

    Hicks, D. G.; Spears, B. K.; Braun, D. G.; Olson, R. E.; Sorce, C. M.; Celliers, P. M.; Collins, G. W.; Landen, O. L.

    2010-10-15

    The velocity and remaining ablator mass of an imploding capsule are critical metrics for assessing the progress toward ignition of an inertially confined fusion experiment. These and other ablator rocket parameters have been measured using a single streaked x-ray radiograph. A regularization technique has been used to determine the ablator density profile {rho}(r) at each time step; moments of {rho}(r) then provide the areal density, average radius, and mass of the unablated, or remaining, ablator material, with the velocity determined from the time derivative of the average radius. The technique has been implemented on experiments at the OMEGA laser facility.

  8. Image-guided ablative therapies for lung cancer.

    PubMed

    Sharma, Amita; Abtin, Fereidoun; Shepard, Jo-Anne O

    2012-09-01

    Lung cancer is the commonest cause of death in adults. Although the treatment of choice is surgical resection with lobectomy, many patients are nonsurgical candidates because of medical comorbidities. Patients may also have recurrent disease after resection or radiotherapy and some patients refuse surgical options. Image-guided ablation has been recently introduced as a safe, alternative treatment of localized disease in carefully selected patients. This article discusses the principles, technique, and follow-up of the 3 main ablative therapies currently used in the lung, radiofrequency ablation, microwave ablation, and percutaneous cryotherapy.

  9. Numerical nonwavefront-guided algorithm for expansion or recentration of the optical zone

    NASA Astrophysics Data System (ADS)

    Arba Mosquera, Samuel; Verma, Shwetabh

    2014-08-01

    Complications may arise due to the decentered ablations during refractive surgery, resulting from human or mechanical errors. Decentration may cause over-/under-corrections, with patients complaining about seeing glares and halos after the procedure. Customized wavefront-guided treatments are often used to design retreatment procedures. However, due to the limitations of wavefront sensors in precisely measuring very large aberrations, some extreme cases may suffer when retreated with wavefront-guided treatments. We propose a simple and inexpensive numerical (nonwavefront-guided) algorithm to recenter the optical zone (OZ) and to correct the refractive error with minimal tissue removal. Due to its tissue-saving capabilities, this method can benefit patients with critical residual corneal thickness. Based on the reconstruction of ablation achieved in the first surgical procedure, we calculate a target ablation (by manipulating the achieved OZ) with adequate centration and an OZ sufficient enough to envelope the achieved ablation. The net ablation map for the retreatment procedure is calculated from the achieved and target ablations and is suitable to expand, recenter, and modulate the lower-order refractive components in a retreatment procedure. The results of our simulations suggest minimal tissue removal with OZ centration and expansion. Enlarging the OZ implies correcting spherical aberrations, whereas inducing centration implies correcting coma. This method shows the potential to improve visual outcomes in extreme cases of retreatment, possibly serving as an uncomplicated and inexpensive alternative to wavefront-guided retreatments.

  10. Temporal Trends in the Histology of the Rabbit Kidney after Cavitational Tissue Ablation

    NASA Astrophysics Data System (ADS)

    Hall, Timothy L.; Kieran, Kathleen; Fowlkes, J. Brian; Cain, Charles A.; Roberts, William W.

    2007-05-01

    Tissue can be mechanically ablated through inertial cavitation generated by high intensity pulsed ultrasound. The ablation appears acutely as a fine slurry with absent cellular structure. Long-term effects and the evolution of histologic changes in disrupted tissue remain poorly understood. This study aimed to characterize the 0-60 day histology of cavitational ablation in a rabbit model. 29 New Zealand White rabbits were anesthetized and exposed to high intensity pulses of ultrasound (60000 pulses, 20 usec duration, 750 kHz, 1 kHz PRF, 18 MPa peak rarefactional pressure, lower pole, left kidney). Kidneys were harvested immediately from five rabbits. The others were recovered and the kidneys were harvested 1, 2, 7, 20, or 60 days after treatment. Grossly, kidneys from 0-2 days displayed subcapsular bruising near the exposure site and some hemorrhage in the adjacent perirenal fat; microscopically, a disrupted, acellular zone measuring 3-5 mm by 5-10 mm accompanied by local infiltration of neutrophils (acute inflammation) was seen. Kidneys harvested after 7 days displayed tubular dilatation adjacent to the targeted area and collagen deposition consistent with scar formation. Decreased collagen deposition, decreased size of the disrupted zone, and regeneration of the tubular basal cell layer of dilated tubules was evident by day 20. Kidneys harvested at 20 and 60 days had contour defects near the exposure site with an apparent volume loss. Cavitation causes orderly and predictable histologic changes. Local renal damage induced during histotripsy may be partially reversible. Further research is needed to identify the clinical correlates of the observed histologic findings.

  11. INTERACTION OF LASER RADIATION WITH MATTER: Production of copper and brass nanoparticles upon laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Kazakevich, Pavel V.; Voronov, Valerii V.; Simakin, Aleksandr V.; Shafeev, Georgii A.

    2004-10-01

    The production of nanoparticles upon ablation of copper and brass by pulsed radiation from Nd:YAG and copper lasers in water, ethanol, and acetone is studied. The nanoparticles were investigated by the methods of X-ray diffractometry, optical spectroscopy, and transmission electron microscopy. The produced copper and brass nanoparticles were shown to exhibit a plasmon resonance lying in the visible spectral range near 580 and 510 nm. The brass nanoparticles produced by ablation in ethanol have a shell approximately 10-nm thick for an average dimension of 20-30 nm. A chemical modification of ethanol was observed, which manifested itself in the appearance of intense UV absorption bands. Upon laser irradiation of brass nanoparticles in a liquid their absorption spectrum gradually transformed into the spectrum of copper nanoparticles.

  12. Collider searches for extra dimensions

    SciTech Connect

    Landsberg, Greg; /Brown U.

    2004-12-01

    Searches for extra spatial dimensions remain among the most popular new directions in our quest for physics beyond the Standard Model. High-energy collider experiments of the current decade should be able to find an ultimate answer to the question of their existence in a variety of models. Until the start of the LHC in a few years, the Tevatron will remain the key player in this quest. In this paper, we review the most recent results from the Tevatron on searches for large, TeV{sup -1}-size, and Randall-Sundrum extra spatial dimensions, which have reached a new level of sensitivity and currently probe the parameter space beyond the existing constraints. While no evidence for the existence of extra dimensions has been found so far, an exciting discovery might be just steps away.

  13. Correlated Electrons in Reduced Dimensions

    SciTech Connect

    Bonesteel, Nicholas E

    2015-01-31

    This report summarizes the work accomplished under the support of US DOE grant # DE-FG02-97ER45639, "Correlated Electrons in Reduced Dimensions." The underlying hypothesis of the research supported by this grant has been that studying the unique behavior of correlated electrons in reduced dimensions can lead to new ways of understanding how matter can order and how it can potentially be used. The systems under study have included i) fractional quantum Hall matter, which is realized when electrons are confined to two-dimensions and placed in a strong magnetic field at low temperature, ii) one-dimensional chains of spins and exotic quasiparticle excitations of topologically ordered matter, and iii) electrons confined in effectively ``zero-dimensional" semiconductor quantum dots.

  14. Image Segmentation via Fractal Dimension

    DTIC Science & Technology

    1987-12-01

    statistical expectation K = a proportionality constant H = the Hurst exponent , in interval [0,1] (14:249) Eq (4) is a mathematical generalization of...ease, negatively correlated (24:16). The Hurst exponent is directly related to the fractal diment.ion of the process being modelled by the relation (24...24) DzE.I -H (5) where D = the fractal dimension E m the Euclidean dimension H = the Hurst exponent The effect of N1 on a typical trace can be seen

  15. CT-guided Bipolar and Multipolar Radiofrequency Ablation (RF Ablation) of Renal Cell Carcinoma: Specific Technical Aspects and Clinical Results

    SciTech Connect

    Sommer, C. M.; Lemm, G.; Hohenstein, E.; Bellemann, N.; Stampfl, U.; Goezen, A. S.; Rassweiler, J.; Kauczor, H. U.; Radeleff, B. A.; Pereira, P. L.

    2013-06-15

    Purpose. This study was designed to evaluate the clinical efficacy of CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma (RCC) and to analyze specific technical aspects between both technologies. Methods. We included 22 consecutive patients (3 women; age 74.2 {+-} 8.6 years) after 28 CT-guided bipolar or multipolar RF ablations of 28 RCCs (diameter 2.5 {+-} 0.8 cm). Procedures were performed with a commercially available RF system (Celon AG Olympus, Berlin, Germany). Technical aspects of RF ablation procedures (ablation mode [bipolar or multipolar], number of applicators and ablation cycles, overall ablation time and deployed energy, and technical success rate) were analyzed. Clinical results (local recurrence-free survival and local tumor control rate, renal function [glomerular filtration rate (GFR)]) and complication rates were evaluated. Results. Bipolar RF ablation was performed in 12 procedures and multipolar RF ablation in 16 procedures (2 applicators in 14 procedures and 3 applicators in 2 procedures). One ablation cycle was performed in 15 procedures and two ablation cycles in 13 procedures. Overall ablation time and deployed energy were 35.0 {+-} 13.6 min and 43.7 {+-} 17.9 kJ. Technical success rate was 100 %. Major and minor complication rates were 4 and 14 %. At an imaging follow-up of 15.2 {+-} 8.8 months, local recurrence-free survival was 14.4 {+-} 8.8 months and local tumor control rate was 93 %. GFR did not deteriorate after RF ablation (50.8 {+-} 16.6 ml/min/1.73 m{sup 2} before RF ablation vs. 47.2 {+-} 11.9 ml/min/1.73 m{sup 2} after RF ablation; not significant). Conclusions. CT-guided bipolar and multipolar RF ablation of RCC has a high rate of clinical success and low complication rates. At short-term follow-up, clinical efficacy is high without deterioration of the renal function.

  16. Staged hybrid ablation for persistent and longstanding persistent atrial fibrillation effectively restores sinus rhythm in long-term observation

    PubMed Central

    Filipiak, Krzysztof; Kowalski, Oskar; Buchta, Piotr; Niklewski, Tomasz; Nadziakiewicz, Pawel; Koba, Rafał; Gąsior, Mariusz; Kalarus, Zbigniew; Zembala, Marian

    2016-01-01

    Introduction Hybrid ablation (HABL) of atrial fibrillation combining endoscopic, minimally invasive, closed chest epicardial ablation with endocardial CARTO-guided accuracy was introduced to overcome the limitations of current therapeutic options for patients with persistent (PSAF) and longstanding persistent atrial fibrillation (LSPAF). The purpose of this study was to evaluate the procedural safety and feasibility as well as effectiveness of HABL in patients with PSAF and LSPAF 1 year after the procedure. Material and methods The study is a single-center, prospective clinical registry. From 07/2009 to 12.2014, 90 patients with PSAF (n = 39) and LSPAF (n = 51), at the mean age of 54.8 ±9.8, in mean EHRA class 2.6, underwent HABL. 64.4% of patients had a history of prior cardioversion or catheter ablation. Thirteen patients had LVEF less than 35%. Mean AF duration was 4.5 ±3.7 years. Patients were scheduled for 3-, 6- and 12-month follow-up with 7-day Holter monitoring. Results At 6 months after the procedure 78% (54/69) of patients were in SR. At 12 months after the procedure 86% (59/69) were in SR and 62.3% (43/69) in SR and off class I/III antiarrhythmic drugs (AADs). Only 1% (1/69) of patients required a repeat ablation for atrial flutter. A significant decrease in LA dimension and an increase in LVEF were noted. Conclusions A combination of epicardial and endocardial RF ablation should be considered as a treatment option for patients with persistent and long-standing persistent atrial fibrillation as it is safe and effective in restoring sinus rhythm. PMID:28144262

  17. Mechanism study of skin tissue ablation by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fang, Qiyin

    Understanding the fundamental mechanisms in laser tissue ablation is essential to improve clinical laser applications by reducing collateral damage and laser pulse energy requirement. The motive of this dissertation is to study skin tissue ablation by nanosecond laser pulses in a wide spectral region from near-infrared to ultraviolet for a clear understanding of the mechanism that can be used to improve future design of the pulsed lasers for dermatology and plastic surgery. Multiple laser and optical configurations have been constructed to generate 9 to 12ns laser pulses with similar profiles at 1064. 532, 266 and 213nm for this study of skin tissue ablation. Through measurements of ablation depth as a function cf laser pulse energy, the 589nm spectral line in the secondary radiation from ablated skin tissue samples was identified as the signature of the occurrence of ablation. Subsequently, this spectral signature has been used to investigate the probabilistic process of the ablation near the threshold at the four wavelengths. Measurements of the ablation probability were conducted as a function of the electrical field strength of the laser pulse and the ablation thresholds in a wide spectral range from 1064nm to 213nm were determined. Histology analysis and an optical transmission method were applied in assessing of the ablation depth per pulse to study the ablation process at irradiance levels higher than threshold. Because more than 70% of the wet weight of the skin tissue is water, optical breakdown and backscattering in water was also investigated along with a nonlinear refraction index measurement using a z-scan technique. Preliminary studies on ablation of a gelatin based tissue phantom are also reported. The current theoretical models describing ablation of soft tissue ablation by short laser pulses were critically reviewed. Since none of the existing models was found capable of explaining the experimental results, a new plasma-mediated model was developed

  18. Resin-Impregnated Carbon Ablator: A New Ablative Material for Hyperbolic Entry Speeds

    NASA Technical Reports Server (NTRS)

    Esper, Jaime; Lengowski, Michael

    2012-01-01

    Ablative materials are required to protect a space vehicle from the extreme temperatures encountered during the most demanding (hyperbolic) atmospheric entry velocities, either for probes launched toward other celestial bodies, or coming back to Earth from deep space missions. To that effect, the resin-impregnated carbon ablator (RICA) is a high-temperature carbon/phenolic ablative thermal protection system (TPS) material designed to use modern and commercially viable components in its manufacture. Heritage carbon/phenolic ablators intended for this use rely on materials that are no longer in production (i.e., Galileo, Pioneer Venus); hence the development of alternatives such as RICA is necessary for future NASA planetary entry and Earth re-entry missions. RICA s capabilities were initially measured in air for Earth re-entry applications, where it was exposed to a heat flux of 14 MW/sq m for 22 seconds. Methane tests were also carried out for potential application in Saturn s moon Titan, with a nominal heat flux of 1.4 MW/sq m for up to 478 seconds. Three slightly different material formulations were manufactured and subsequently tested at the Plasma Wind Tunnel of the University of Stuttgart in Germany (PWK1) in the summer and fall of 2010. The TPS integrity was well preserved in most cases, and results show great promise.

  19. Similarities and differences in ablative and non-ablative iron oxide nanoparticle hyperthermia cancer treatment

    NASA Astrophysics Data System (ADS)

    Petryk, Alicia A.; Misra, Adwiteeya; Kastner, Elliot J.; Mazur, Courtney M.; Petryk, James D.; Hoopes, P. Jack

    2015-03-01

    The use of hyperthermia to treat cancer is well studied and has utilized numerous delivery techniques, including microwaves, radio frequency, focused ultrasound, induction heating, infrared radiation, warmed perfusion liquids (combined with chemotherapy), and recently, metallic nanoparticles (NP) activated by near infrared radiation (NIR) and alternating magnetic field (AMF) based platforms. It has been demonstrated by many research groups that ablative temperatures and cytotoxicity can be produced with locally NP-based hyperthermia. Such ablative NP techniques have demonstrated the potential for success. Much attention has also been given to the fact that NP may be administered systemically, resulting in a broader cancer therapy approach, a lower level of tumor NP content and a different type of NP cancer therapy (most likely in the adjuvant setting). To use NP based hyperthermia successfully as a cancer treatment, the technique and its goal must be understood and utilized in the appropriate clinical context. The parameters include, but are not limited to, NP access to the tumor (large vs. small quantity), cancer cell-specific targeting, drug carrying capacity, potential as an ionizing radiation sensitizer, and the material properties (magnetic characteristics, size and charge). In addition to their potential for cytotoxicity, the material properties of the NP must also be optimized for imaging, detection and direction. In this paper we will discuss the differences between, and potential applications for, ablative and non-ablative magnetic nanoparticle hyperthermia.

  20. Alterations in Ultrasound Scattering Following Thermal Ablation in ex vivo Bovine Liver.

    PubMed

    Rubert, Nicholas; Varghese, Tomy

    2014-09-06

    Thermal ablation is a minimally invasive cancer treatment which has been rapidly gaining clinical acceptance. It is well known that thermal ablation increases the acoustic attenuation and shear modulus of tissue. In this work, we examine changes to the spatial distribution of scatterers in liver tissue following thermal ablation. Acoustic scatterers within liver tissue have frequently been modeled as pseudo-periodic. The positions of pseudo-periodic scatterers have been Gamma distributed along the beam dimension, and these scatterers are characterized by their mean scatterer spacing (MSS). Prior work have demonstrated significant changes in MSS due to diffuse liver disease, such as steatosis progressing to cirrhosis. However, relatively few results have been reported regarding changes in MSS following thermal ablation. In this study, we estimated MSS in ex vivo bovine liver by detecting local maxima in spectral coherence functions calculated using Thomson's multi-taper method. We examined a large number of uncorrelated regions of interest recorded from five normal bovine livers (~300 images from each animal). We also examined a large number of ROI's from five bovine livers following thermal coagulation. All bovine livers were obtained from a commercial meat production facility immediately following animal sacrifice and imaged within 12 hours. Thermal coagulation was induced by heating liver in saline water baths at 80° C for 45 minutes. For normal, unheated liver an MSS of approximately 1.5 mm was estimated. Following thermal ablation, an MSS of approximately 0.5 mm in thermally coagulated tissue was obtained. Frequently, studies estimating MSS in liver tissue provide an MSS estimate regardless of the state of tissue. Authors rarely present what their MSS estimation algorithm would produce if it were applied to tissue which is better modeled as a collection of uniformly, randomly distributed scatterers lacking periodicity. In this study, we found that thermal

  1. The Visuospatial Dimension of Writing

    ERIC Educational Resources Information Center

    Olive, Thierry; Passerault, Jean-Michel

    2012-01-01

    The authors suggest that writing should be conceived of not only as a verbal activity but also as a visuospatial activity, in which writers process and construct visuospatial mental representations. After briefly describing research on visuospatial cognition, they look at how cognitive researchers have investigated the visuospatial dimension of…

  2. The Feeling Dimension in Reading.

    ERIC Educational Resources Information Center

    Ediger, Marlow

    The feeling dimension of students cannot be ignored in teaching and learning situations. Feelings are there and must not be ignored. Reading stresses word recognition, comprehension of subject matter at diverse levels of complexity, and application of what has been learned. A major ingredient so frequently left out is student appreciation of the…

  3. Heat conduction in three dimensions

    NASA Technical Reports Server (NTRS)

    Danza, T. M.; Fesler, L. W.; Mongan, R. D.

    1980-01-01

    Multidimensional heat conduction program computes transient temperature history and steady state temperatures of complex body geometries in three dimensions. Emphasis is placed on type of problems associated with Space Shuttle thermal protection system, but program could be used in thermal analysis of most three dimensional systems.

  4. The European Dimension in Education.

    ERIC Educational Resources Information Center

    Council of Europe, Strasbourg (France). Directorate of Education, Culture and Sport, Documentation Section.

    This paper addresses concerns about a European dimension in education that has been created by the enlargement of the European Union (EU) (the inclusion of Austria, Finland, and Sweden) and the gradual transformations of institutions into a future federal state. Sections of the paper include: (1) "Introduction"; (2) "Defining the…

  5. Warping the universal extra dimensions

    SciTech Connect

    McDonald, Kristian L.

    2009-07-15

    We develop the necessary ingredients for the construction of realistic models with warped universal extra dimensions. Our investigations are based on the seven-dimensional (7D) spacetime AdS{sub 5}xT{sup 2}/Z{sub 2} and we derive the Kaluza-Klein (KK) spectra for gravitons, bulk vectors, and the TeV brane localized Higgs boson. We show that, starting with a massive 7D fermion, one may obtain a single chiral massless mode whose profile is readily localized towards the Planck or TeV brane. This allows one to place the standard model fermions in the bulk and construct models of flavor as in Randall-Sundrum models. Our solution also admits the familiar KK parity of models with universal extra dimensions so that the lightest odd KK state is stable and may be a dark matter candidate. As an additional feature the AdS{sub 5} warping ensures that the excited modes on the torus, including the dark matter candidate, appear at TeV energies (as is usually assumed in models with universal extra dimensions) even though the Planck scale sets the dimensions for the torus.

  6. Interpretation and the Aesthetic Dimension

    ERIC Educational Resources Information Center

    Mortensen, Charles O.

    1976-01-01

    The author, utilizing a synthesis of philosophic comments on aesthetics, provides a discourse on the aesthetic dimension and offers examples of how interpreters can nurture the innate sense of beauty in man. Poetic forms, such as haiku, are used to relate the aesthetic relationship between man and the environment. (BT)

  7. Cosmology with dynamical extra dimensions

    NASA Astrophysics Data System (ADS)

    Erickson, Joel K.

    Nearly every attempt to unify the fundamental forces incorporates the idea of compact extra dimensions. The notion was introduced by Kaluza and Klein in the 1920s and is an essential part of contemporary string theory and M-theory. In most treatments the extra dimensions are static. We consider the consequences of extra dimensions with time-varying radii. The radii are modeled by light scalar fields. These may have unusual properties which produce observable effects, such as non-canonical kinetic energies, couplings to matter and radiation, and non-minimal coupling to gravity. Extra dimensions may be responsible for dark energy in the late universe. The simplest model of dark energy is characterized by its equation of state. We show that constraints placed on realistic models by the universality of free fall, variation of fundamental constants and metric tests of gravity are often stricter than bounds on the equation of state. Testing the equivalence principle maybe an effective way of distinguishing some quintessence models from a cosmological constant. In certain dark energy models the speed of sound is much less than the speed of light. We calculate how this affects the cosmic microwave background and show that the speed of sound may be measurable, provided dark energy is sufficiently dense at decoupling. This is another possible signature of quintessence. Dynamical extra dimensions may have consequences for the early universe. In the cyclic model, the universe is described in terms of a series of contractions and expansions of an extra dimension. The big bang is preceded by a big crunch and quantum fluctuations of the scalar field produce structure in universe. We consider how the fluctuations evolve and build over many cycles and show that there are no observable instabilities or adverse effects. In the cyclic model extra dimensions act as both dark energy and as an agent to cause contraction and a big crunch. Previous theorems suggested that contraction

  8. Compactified Vacuum in Ten Dimensions.

    NASA Astrophysics Data System (ADS)

    Wurmser, Daniel

    1987-09-01

    Since the 1920's, theories which unify gravity with the other fundamental forces have called for more than the four observed dimensions of space-time. According to such a theory, the vacuum consists of flat four-dimensional space-time described by the Minkowski metric M ^4 and a "compactified" space B. The dimensions of B are small, and the space can only be observed at distance scales smaller than the present experimental limit. These theories have had serious difficulties. The equations of gravity severely restrict the possible choices for the space B. The allowed spaces are complicated and difficult to study. The vacuum is furthermore unstable in the sense that a small perturbation causes the compactified dimensions to expand indefinitely. There is an addition a semi-classical argument which implies that the compactified vacuum be annihilated by virtual black holes. It follows that a universe with compactified extra dimensions could not have survived to the present. These results were derived by applying the equations of general relativity to spaces of more than four dimensions. The form of these equations was assumed to be unchanged by an increase in the number of dimensions. Recently, it has been proposed that gravity in more than four dimensions may involve terms of higher order in the curvature as well as the linear terms present in ordinary general relativity. I illustrate the effect of such terms by considering the example B = S^6 where S ^6 is the six-dimensional sphere. Only when the extra terms are included is this choice of the compactified space allowed. I explore the effect of a small perturbation on such a vacuum. The ten-dimensional spherically symmetric potential is examined, and I determine conditions under which the formation of virtual black holes is forbidden. The example M^4 times S^6 is still plagued by the semi -classical instability, but this result does not hold in general. The requirement that virtual black holes be forbidden provides a

  9. Radiofrequency ablation for benign thyroid nodules.

    PubMed

    Bernardi, S; Stacul, F; Zecchin, M; Dobrinja, C; Zanconati, F; Fabris, B

    2016-09-01

    Benign thyroid nodules are an extremely common occurrence. Radiofrequency ablation (RFA) is gaining ground as an effective technique for their treatment, in case they become symptomatic. Here we review what are the current indications to RFA, its outcomes in terms of efficacy, tolerability, and cost, and also how it compares to the other conventional and experimental treatment modalities for benign thyroid nodules. Moreover, we will also address the issue of treating with this technique patients with cardiac pacemakers (PM) or implantable cardioverter-defibrillators (ICD), as it is a rather frequent occurrence that has never been addressed in detail in the literature.

  10. Dopant Distribution in NIF Beryllium Ablator Capsules

    NASA Astrophysics Data System (ADS)

    Huang, H.; Xu, H. W.; Youngblood, K. P.; Wall, D. R.; Stephens, R. B.; Moreno, K. A.; Nikroo, A.; Salmonson, J. D.; Haan, S. W.; Wu, K. J.; Wang, Y. M.; Hamza, A. V.

    2012-10-01

    Good implosion performance requires capsule ablator material with spherically uniform x-ray opacity, which is controlled by one of several dopants (Cu, Si, Al, etc.) in the Be shell. During production, the dopant concentration is radially stepped. However, the various Be-dopant interactions result in vastly different dopant distribution patterns, some quite inhomogeneous. We have characterized these structures and established the phenomenological basis and the magnitudes of the inhomogeneity both in spatial length scales and in atomic percent. We will discuss the case of inhomogeneous Cu diffusion in detail, followed by discussions of other dopants and the estimate of the impact of these structures on target implosion.

  11. Dynamical modeling of laser ablation processes

    SciTech Connect

    Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

    1995-09-01

    Several physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume; plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms; gas dynamic, hydrodynamic, and collisional descriptions of plume transport; and molecular dynamics models of the interaction of plume particles with the deposition substrate. The complexity of the phenomena involved in the laser ablation process is matched by the diversity of the modeling task, which combines materials science, atomic physics, and plasma physics.

  12. Inertial effects in laser-driven ablation

    SciTech Connect

    Harrach, R.J.; Szeoke, A.; Howard, W.M.

    1983-07-15

    The gasdynamic partial differential equations (PDE's) governing the motion of an ablatively accelerated target (rocket) contain an inertial force term that arises from acceleration of the reference frame in which the PDE's are written. We give a simple, intuitive description of this effect, and estimate its magnitude and parametric dependences by means of approximate analytical formulas inferred from our computer hydrocode calculations. Often this inertial term is negligible, but for problems in the areas of laser fusion and laser equation of state studies we find that it can substantially reduce the attainable hydrodynamic efficiency of acceleration and implosion.

  13. Excimer laser ablation of the cornea

    NASA Astrophysics Data System (ADS)

    Pettit, George H.; Ediger, Marwood N.; Weiblinger, Richard P.

    1995-03-01

    Pulsed ultraviolet laser ablation is being extensively investigated clinically to reshape the optical surface of the eye and correct vision defects. Current knowledge of the laser/tissue interaction and the present state of the clinical evaluation are reviewed. In addition, the principal findings of internal Food and Drug Administration research are described in some detail, including a risk assessment of the laser-induced-fluorescence and measurement of the nonlinear optical properties of cornea during the intense UV irradiation. Finally, a survey is presented of the alternative laser technologies being explored for this ophthalmic application.

  14. Sprayable low density ablator and application process

    NASA Technical Reports Server (NTRS)

    Sharpe, M. H.; Hill, W. E.; Simpson, W. G.; Carter, J. M.; Brown, E. L.; King, H. M.; Schuerer, P. H.; Webb, D. D. (Inventor)

    1978-01-01

    A sprayable, low density ablative composition is described consisting esentially of: (1) 100 parts by weight of a mixture of 25-65% by weight of phenolic microballoons, 0-20% by weight of glass microballoons, 4-10% by weight of glass fibers, 25-45% by weight of an epoxy-modified polyurethane resin, 2-4% by weight of a bentonite dispersing aid, and 1-2% by weight of an alcohol activator for the bentonite; (2) 1-10 parts by weight of an aromatic amine curing agent; and (3) 200-400 parts by weight of a solvent.

  15. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2015-07-21

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  16. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2014-07-22

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline materiat layer; and forming conductive contacts in the plurality of contact holes.

  17. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David; Cousins, Peter

    2012-12-04

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  18. Antibacterial effects of laser ablated Ni nanoparticles

    NASA Astrophysics Data System (ADS)

    Shamaila, S.; Wali, H.; Sharif, R.; Nazir, J.; Zafar, N.; Rafique, M. S.

    2013-10-01

    The interaction of nickel nanoparticles with Escherichia coli (E. coli) bacteria has been studied. The nickel nanoparticles have been fabricated by continuous wave laser ablation of nickel target and their properties are studied using different characterization techniques. The antibacterial activity of nickel nanoparticles was checked against E. coli bacteria. Escherichia coli were cultured in nutrients broth and different concentrations of nickel nanoparticles were added to bacterial culture solution to investigate the interaction of nickel nanoparticles with bacteria and to check toxicity of the nickel nanoparticles against E. coli. The fabricated Ni nanoparticles have exhibited considerable antimicrobial activity against E. coli.

  19. A simulation study to compare the phase-shift angle radiofrequency ablation mode with bipolar and unipolar modes in creating linear lesions for atrial fibrillation ablation.

    PubMed

    Yan, Shengjie; Wu, Xiaomei; Wang, Weiqi

    2016-05-01

    Purpose In pulmonary veins (PVs) isolation (PVI), radiofrequency (RF) energy is often used to create a linear lesion for blocking the accessory conduction pathways around PVs. By using transient finite element analysis, this study compared the effectiveness of phase-shift mode (PsM) ablation with bipolar mode (BiM) and unipolar mode (UiM) in creating a continuous lesion and lesion depth in a 5-mm thick atrial wall. Materials and methods Computer models were developed to study the temperature distributions and lesion dimensions in atrial walls created through PsM, BiM, and UiM. Four phase-shift angles - 45°, 90°, 135°, and 180° - were considered in PsM ablation (hereafter, PsM-45°, PsM-90°, PsM-135°, and PsM-180°, respectively). Results At 60 s/30 V peak value of RF voltage, UiM and PsM-45° did not create an effective lesion, whereas BiM created a lesion of maximum depth and width approximately 1.01 and 1.62 mm, respectively. PsM-135° and PsM-180° not only created transmural lesions in 5-mm thick atrial walls but also created continuous lesions between electrodes spaced 4 mm apart; similarly, PsM-90° created a continuous lesion with a maximum depth and width of nearly 4.09 and 6.12 mm. Conclusions Compared with UiM and BiM, PsM-90°, PsM-135° and PsM-180° created continuous and larger lesions in a single ablation procedure and at 60 s/30 V peak value of RF voltage. Therefore, the proposed PsM ablation method is suitable for PVI and linear isolation at the left atrial roof for treating atrial fibrillation.

  20. Rail gun performance and plasma characteristics due to wall ablation

    NASA Technical Reports Server (NTRS)

    Ray, P. K.

    1986-01-01

    The experiment of Bauer, et al. (1982) is analyzed by considering wall ablation and viscous drag in the plasma. Plasma characteristics are evaluated through a simple fluid-mechanical analysis considering only wall ablation. By equating the energy dissipated in the plasma with the radiation heat loss, the average properties of the plasma are determined as a function of time.