Requirements and prototype for supporting the planning of patient specific thermal ablation interventions

International Nuclear Information System (INIS)

Schramm, W.

2010-01-01

Background Thermal ablation is the process of destroying pathological tissue by either high temperatures of approximately 105 o C as achieved in radiofrequency ablation or low temperatures of approximately - 40 o C as used in cryotherapy. Ablations are widely used in clinical practice and provide a safe and generally well tolerated minimal invasive treatment if surgery is not an option. Thermal ablations are usually performed under image guidance, either by ultrasound, CT or MR. Even though ablations are widely used, very little textbook knowledge is available. Because of the treatment complexity there is a need for a well defined process which can be followed by an experienced radiologist as well as an inexperienced one. There is also a need for a planning platform which is capable of supporting the physician in planning the intervention on the basis of the patient's anatomy. For additional benefit this platform should also provide the means for estimating the final coagulation zone by simulations based on the patient's anatomy. The most widely used method to simulate the extend of a coagulation zone is by the usage of finite element analysis (FEA). FEA uses a defined geometry with the physical properties of the tissue and the ablation modality to create a model which can then be solved to make estimations about the extend of the final coagulation zone. Method and Results To deal with the problem of ablation knowledge being only available in distributed form, a workflow was abstracted and translated into diagrams. These workflow diagrams visualize the required steps and decisions when performing thermal ablations. The workflow is split into a planning, applicator placement, ablation and result evaluation phase. The information gained from this knowledge is then used to define the requirements for a platform which is capable of helping the physician when performing the ablation. In the next step I examined the possibility to increase an ablation's coagulation zone

Analysis of the ballooning deformation of an internally pressurized thin-wall tube during fast thermal transients

International Nuclear Information System (INIS)

Lin, E.I.H.

1977-01-01

A large-strain time-dependent thermoplastic analysis has been developed for the ballooning deformation of a thin-wall tube subjected to internal pressure, axial loading, and fast thermal transients. This deformation initiates with the onset of plastic instability in the material, the onset being determined by a plastic-instability criterion for strain-rate sensitive materials. The interaction among the local ballooning geometry, the state of stress, and the plastic flow process was considered, and integration of the flow equations yields the local curvature and the states of stress and strain in the vicinity of the maximum ballooning site. The effects of axial constraint and heating rate were also discussed. The analysis was applied to a LWR Zircaloy cladding subjected to a constant heating rate and a range of internal pressures. The results agree very well with experimental strain-time data obtained from tube-burst tests. In most cases, the time of rupture was accurately predicted despite the lack of complete material-property data

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

Science.gov (United States)

Bay, Erwin; Douplik, Alexandre; Razansky, Daniel

2014-05-01

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

Exploiting Microwave Imaging Methods for Real-Time Monitoring of Thermal Ablation

Directory of Open Access Journals (Sweden)

Rosa Scapaticci

2017-01-01

Full Text Available Microwave thermal ablation is a cancer treatment that exploits local heating caused by a microwave electromagnetic field to induce coagulative necrosis of tumor cells. Recently, such a technique has significantly progressed in the clinical practice. However, its effectiveness would dramatically improve if paired with a noninvasive system for the real-time monitoring of the evolving dimension and shape of the thermally ablated area. In this respect, microwave imaging can be a potential candidate to monitor the overall treatment evolution in a noninvasive way, as it takes direct advantage from the dependence of the electromagnetic properties of biological tissues from temperature. This paper explores such a possibility by presenting a proof of concept validation based on accurate simulated imaging experiments, run with respect to a scenario that mimics an ex vivo experimental setup. In particular, two model-based inversion algorithms are exploited to tackle the imaging task. These methods provide independent results in real-time and their integration improves the quality of the overall tracking of the variations occurring in the target and surrounding regions.

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

Science.gov (United States)

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

2008-03-01

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

Tumour eradication using synchronous thermal ablation and Hsp90 chemotherapy with protein engineered triblock biopolymer-geldanamycin conjugates.

Science.gov (United States)

Chen, Yizhe; Youn, Pilju; Pysher, Theodore J; Scaife, Courtney L; Furgeson, Darin Y

2014-12-01

Hepatocellular carcinoma (HCC) suffers high tumour recurrence rate after thermal ablation. Heat shock protein 90 (Hsp90) induced post-ablation is critical for tumour survival and progression. A combination therapy of thermal ablation and polymer conjugated Hsp90 chemotherapy was designed and evaluated for complete tumour eradication of HCC. A thermo-responsive, elastin-like polypeptide (ELP)-based tri-block biopolymer was developed and conjugated with a potent Hsp90 inhibitor, geldanamycin (GA). The anti-cancer efficacy of conjugates was evaluated in HCC cell cultures with and without hyperthermia (43 °C). The conjugates were also administered twice weekly in a murine HCC model as a single treatment or in combination with single electrocautery as the ablation method. ELP-GA conjugates displayed enhanced cytotoxicity in vitro and effective heat shock inhibition under hyperthermia. The conjugates alone significantly slowed the tumour growth without systemic toxicity. Four doses of thermo-responsive ELP-GA conjugates with concomitant simple electrocautery accomplished significant Hsp90 inhibition and sustained tumour suppression. Hsp90 inhibition plays a key role in preventing the recurrence of HCC, and the combination of ablation with targeted therapy holds great potential to improve prognosis and survival of HCC patients.

Development of a high-field MR-guided HIFU setup for thermal and mechanical ablation methods in small animals

NARCIS (Netherlands)

Hoogenboom, M.; Amerongen, M.J. van; Eikelenboom, D.C.; Wassink, M.; Brok, M.H. den; Hulsbergen-van de Kaa, C.A.; Dumont, E.; Adema, G.J.; Heerschap, A.; Futterer, J.J.

2015-01-01

BACKGROUND: Thermal and mechanical high intensity focused ultrasound (HIFU) ablation techniques are in development for non-invasive treatment of cancer. However, knowledge of in vivo histopathologic and immunologic reactions after HIFU ablation is still limited. This study aims to create a setup for

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

Science.gov (United States)

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

2016-01-01

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

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

Science.gov (United States)

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

2017-02-01

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

Near-real-time feedback control system for liver thermal ablations based on self-referenced temperature imaging

International Nuclear Information System (INIS)

Keserci, Bilgin M.; Kokuryo, Daisuke; Suzuki, Kyohei; Kumamoto, Etsuko; Okada, Atsuya; Khankan, Azzam A.; Kuroda, Kagayaki

2006-01-01

Our challenge was to design and implement a dedicated temperature imaging feedback control system to guide and assist in a thermal liver ablation procedure in a double-donut 0.5T open MR scanner. This system has near-real-time feedback capability based on a newly developed 'self-referenced' temperature imaging method using 'moving-slab' and complex-field-fitting techniques. Two phantom validation studies and one ex vivo experiment were performed to compare the newly developed self-referenced method with the conventional subtraction method and evaluate the ability of the feedback control system in the same MR scanner. The near-real-time feedback system was achieved by integrating the following primary functions: (1) imaging of the moving organ temperature; (2) on-line needle tip tracking; (3) automatic turn-on/off the heating devices; (4) a Windows operating system-based novel user-interfaces. In the first part of the validation studies, microwave heating was applied in an agar phantom using a fast spoiled gradient recalled echo in a steady state sequence. In the second part of the validation and ex vivo study, target visualization, treatment planning and monitoring, and temperature and thermal dose visualization with the graphical user interface of the thermal ablation software were demonstrated. Furthermore, MR imaging with the 'self-referenced' temperature imaging method has the ability to localize the hot spot in the heated region and measure temperature elevation during the experiment. In conclusion, we have demonstrated an interactively controllable feedback control system that offers a new method for the guidance of liver thermal ablation procedures, as well as improving the ability to assist ablation procedures in an open MR scanner

Hot air balloon engine

Energy Technology Data Exchange (ETDEWEB)

Edmonds, Ian [Solartran Pty Ltd, 12 Lentara Street, Kenmore, Brisbane 4069 (Australia)

2009-04-15

This paper describes a solar powered reciprocating engine based on the use of a tethered hot air balloon fuelled by hot air from a glazed collector. The basic theory of the balloon engine is derived and used to predict the performance of engines in the 10 kW to 1 MW range. The engine can operate over several thousand metres altitude with thermal efficiencies higher than 5%. The engine thermal efficiency compares favorably with the efficiency of other engines, such as solar updraft towers, that also utilize the atmospheric temperature gradient but are limited by technical constraints to operate over a much lower altitude range. The increased efficiency allows the use of smaller area glazed collectors. Preliminary cost estimates suggest a lower $/W installation cost than equivalent power output tower engines. (author)

Immediate balloon deflation for prevention of persistent phrenic nerve palsy during pulmonary vein isolation by balloon cryoablation.

Science.gov (United States)

Ghosh, Justin; Sepahpour, Ali; Chan, Kim H; Singarayar, Suresh; McGuire, Mark A

2013-05-01

Persistent phrenic nerve palsy is the most frequent complication of cryoballoon ablation for atrial fibrillation and can be disabling. To describe a technique-immediate balloon deflation (IBD)-for the prevention of persistent phrenic nerve palsy, provide data for its use, and describe in vitro simulations performed to investigate the effect of IBD on the atrium and pulmonary vein. Cryoballoon procedures for atrial fibrillation were analyzed retrospectively (n = 130). IBD was performed in patients developing phrenic nerve dysfunction (n = 22). In vitro simulations were performed by using phantoms. No adverse events occurred, and all patients recovered normal phrenic nerve function before leaving the procedure room. No patient developed persistent phrenic nerve palsy. The mean cryoablation time to onset of phrenic nerve dysfunction was 144 ± 64 seconds. Transient phrenic nerve dysfunction was seen more frequently with the 23-mm balloon than with the 28-mm balloon (11 of 39 cases vs 11 of 81 cases; P = .036). Balloon rewarming was faster following IBD. The time to return to 0 and 20° C was shorter in the IBD group (6.7 vs 8.9 seconds; P = .007 and 16.7 vs 37.6 seconds; Pphrenic nerve palsy. Simulations suggest that IBD is unlikely to damage the atrium or pulmonary vein. Copyright © 2013 Heart Rhythm Society. All rights reserved.

Osteoid Osteoma: Experience with Laser- and Radiofrequency-Induced Ablation

International Nuclear Information System (INIS)

Gebauer, Bernhard; Tunn, Per-Ulf; Gaffke, Gunnar; Melcher, Ingo; Felix, Roland; Stroszczynski, Christian

2006-01-01

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

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

Science.gov (United States)

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

2017-12-01

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

Laser ablation in CdZnTe crystal due to thermal self-focusing: Secondary phase hydrodynamic expansion

Energy Technology Data Exchange (ETDEWEB)

Medvid’, A., E-mail: mychko@latnet.lv [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia); Mychko, A.; Dauksta, E. [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia); Kosyak, V. [Sumy State University, 2, Rymskogo-Korsakova St., 40007 Sumy (Ukraine); Grase, L. [Riga Technical University, 3 Paula Valdena Str., LV-1048 Riga (Latvia)

2016-06-30

Highlights: • We found two laser induced threshold intensity for CdZnTe crystal. • The laser beam self-focusing lead to increase of intensity of laser radiation at exit surface. • Laser ablation is a result of Te inclusion hydrodynamic expansion. - Abstract: The present paper deals with the laser ablation in CdZnTe crystal irradiated by pulsed infrared laser. Two values of threshold intensities of the laser ablation were determined, namely of about 8.5 and 6.2 MW/cm{sup 2} for the incident and the rear surfaces, correspondingly. Lower intensity of the laser ablation for the rear surface is explained by thermal self-focusing of the laser beam in the CdZnTe crystal due to heating of Te inclusions with a following hydrodynamic expansion.

Intrauterin graviditet efter Cavatermbehandling

DEFF Research Database (Denmark)

Shokouh-Amiri, Ali; Kjaergaard, Niels

2009-01-01

A case of intrauterine pregnancy occurring after successful balloon thermal endometrial ablation is described. Although rare, pregnancy after endometrial ablation is possible, and use of a supplemental contraceptive method should be planned. In case of pregnancy after endometrial ablation...

Ballooning of CANDU pressure tube in local thermal transients

International Nuclear Information System (INIS)

Mihalache, Maria; Ionescu, Viorel

2008-01-01

In certain LOCA scenarios for the CANDU fuel channel, the ballooning of the pressure tube and contact with the calandria tube can occur. After the contact moment, a radial heat transfer from cooling fluid to moderator takes place through the contact area. If the temperature of channel walls increases, the contact area is drying and the heat transfer becomes inefficiently. In INR-Pitesti the DELOCA code was developed to simulate the mechanical behaviour of pressure tube during pre-contact transition, and mechanical and thermal behaviour of pressure tube and calandria tube after occurrence of the contact between the two tubes. The code contains few models: thermal creep of Zr-2.5%Nb alloy, the heat transfer by conduction through the cylindrical walls, channel failure criteria and calculus of heat transfer at the calandria tube - moderator interface. This code evaluates the contact and channel failure moments. This paper gives a DELOCA code description and the fuel channel behaviour analysis, in transient temperature conditions of the pressure tube, using the materials properties, time and temperature dependencies of these properties as obtained in the different laboratories of the world and in the INR - Pitesti in the last years. DELOCA computer code simulated the fuel channel response to the constant heating rates of inside pressure tube surface. The paper presents contact temperature and time dependencies on the heating rate, and the appropriate fitting functions. (authors)

MRI Reconstructions of Human Phrenic Nerve Anatomy and Computational Modeling of Cryoballoon Ablative Therapy.

Science.gov (United States)

Goff, Ryan P; Spencer, Julianne H; Iaizzo, Paul A

2016-04-01

The primary goal of this computational modeling study was to better quantify the relative distance of the phrenic nerves to areas where cryoballoon ablations may be applied within the left atria. Phrenic nerve injury can be a significant complication of applied ablative therapies for treatment of drug refractory atrial fibrillation. To date, published reports suggest that such injuries may occur more frequently in cryoballoon ablations than in radiofrequency therapies. Ten human heart-lung blocs were prepared in an end-diastolic state, scanned with MRI, and analyzed using Mimics software as a means to make anatomical measurements. Next, generated computer models of ArticFront cryoballoons (23, 28 mm) were mated with reconstructed pulmonary vein ostias to determine relative distances between the phrenic nerves and projected balloon placements, simulating pulmonary vein isolation. The effects of deep seating balloons were also investigated. Interestingly, the relative anatomical differences in placement of 23 and 28 mm cryoballoons were quite small, e.g., the determined difference between mid spline distance to the phrenic nerves between the two cryoballoon sizes was only 1.7 ± 1.2 mm. Furthermore, the right phrenic nerves were commonly closer to the pulmonary veins than the left, and surprisingly tips of balloons were further from the nerves, yet balloon size choice did not significantly alter calculated distance to the nerves. Such computational modeling is considered as a useful tool for both clinicians and device designers to better understand these associated anatomies that, in turn, may lead to optimization of therapeutic treatments.

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

Science.gov (United States)

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

1994-01-01

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

Analysis of the ballooning deformation of an internally pressurized thin-wall tube during fast thermal transients

International Nuclear Information System (INIS)

Lin, E.I.H.

1977-01-01

A large-strain, time-dependent thermoplastic analysis of ballooning deformation was developed. The true (or lagorithmic) strains, the Von Mises yield criterion and Prandtl-Reuss flow rules were used. The constitutive equation was expressed in terms of the temperature, effective stress, strain and strain rate. Material isotropy was assumed as a first approximation; note that at high temperatures even zircaloy tends to lose a substantial amount of its low-temperature anisotropy. The axisymmetry of ballooning was also assumed, which has actually been verified by numerous experiments to be accurate throughout the course of ballooning, except in the final stage when rupture is imminent. The thin-shell approximation was made, which proved to be adequate for the standard fuel claddings and which was advantageous in that the averaged state of stress was rendered determinate. The analysis led to a set of non-linear ordinary differential equations, which was then integrated by a fifth-order Runge-Kutta routine. The general formulation allows for a direct interpretation of the experimentally-observed effects of the heating rate and cladding axial constraints on the ballooning behavior. Its implications on the flow-blockage and cladding-rupture evaluations were discussed. The analysis was applied to zircaloy claddings subjected to simulated thermal transient conditions. Most of the required material properties were taken from the existing uniaxial tensile test data. Analyses were performed at a uniform heating rate of 115 0 C/sec with internal pressures ranging from 100 to 1200 psi. Satisfactory agreement was obtained between the predictions and the diametral strain-time data available from tube-burst tests

Characterisation of tissue shrinkage during microwave thermal ablation.

Science.gov (United States)

Farina, Laura; Weiss, Noam; Nissenbaum, Yitzhak; Cavagnaro, Marta; Lopresto, Vanni; Pinto, Rosanna; Tosoratti, Nevio; Amabile, Claudio; Cassarino, Simone; Goldberg, S Nahum

2014-11-01

The aim of this study was to characterise changes in tissue volume during image-guided microwave ablation in order to arrive at a more precise determination of the true ablation zone. The effect of power (20-80 W) and time (1-10 min) on microwave-induced tissue contraction was experimentally evaluated in various-sized cubes of ex vivo liver (10-40 mm ± 2 mm) and muscle (20 and 40 mm ± 2 mm) embedded in agar phantoms (N = 119). Post-ablation linear and volumetric dimensions of the tissue cubes were measured and compared with pre-ablation dimensions. Subsequently, the process of tissue contraction was investigated dynamically during the ablation procedure through real-time X-ray CT scanning. Overall, substantial shrinkage of 52-74% of initial tissue volume was noted. The shrinkage was non-uniform over time and space, with observed asymmetry favouring the radial (23-43 % range) over the longitudinal (21-29%) direction. Algorithmic relationships for the shrinkage as a function of time were demonstrated. Furthermore, the smallest cubes showed more substantial and faster contraction (28-40% after 1 min), with more considerable volumetric shrinkage (>10%) in muscle than in liver tissue. Additionally, CT imaging demonstrated initial expansion of the tissue volume, lasting in some cases up to 3 min during the microwave ablation procedure, prior to the contraction phenomenon. In addition to an asymmetric substantial shrinkage of the ablated tissue volume, an initial expansion phenomenon occurs during MW ablation. Thus, complex modifications of the tissue close to a radiating antenna will likely need to be taken into account for future methods of real-time ablation monitoring.

Percutaneous tumor ablation in medical radiology

Energy Technology Data Exchange (ETDEWEB)

Vogl, T.J.; Mack, M.G. [University Hospital Frankfurt Univ. (Germany). Inst. for Diagnostic and Interventional Radiology; Helmberger, T.K. [Klinikum Bogenhausen, Academic Teaching Hospital of the Technical Univ. Munich (Germany). Dept. for Diagnostic and Interventional Radiology and Nuclear Medicine; Reiser, M.F. (eds.) [University Hospitals - Grosshadern and Innenstadt Munich Univ. (Germany). Dept. of Clinical Radiology

2008-07-01

Thermal ablation has become an integral part of oncology, especially in the field of interventional oncology. This very comprehensive book encompasses the different technologies employed in thermal ablation, its indications and the results achieved in various clinical conditions. The first part of the book clearly explains the basics of thermal ablative techniques such as laser-induced thermotherapy, radiofrequency ablation, microwave ablation, cryotherapy, and localized tumor therapy. The latest developments in the application of minimally invasive therapies in localized neoplastic disease are demonstrated. In the main part of the book, techniques of guiding the applicators to the target structures by use of different imaging tools such as ultrasound, computed tomography and magnetic resonance imaging are discussed. The results are presented for a variety of clinical indications, including liver and lung tumors and metastases and some rather rare conditions involving the kidney, the head and neck, the prostate, and soft tissue structures. A large number of acknowledged experts have contributed to the book, which benefits from a lucid structure and excellent images. (orig.)

Percutaneous tumor ablation in medical radiology

International Nuclear Information System (INIS)

Vogl, T.J.; Mack, M.G.; Helmberger, T.K.; Reiser, M.F.

2008-01-01

Thermal ablation has become an integral part of oncology, especially in the field of interventional oncology. This very comprehensive book encompasses the different technologies employed in thermal ablation, its indications and the results achieved in various clinical conditions. The first part of the book clearly explains the basics of thermal ablative techniques such as laser-induced thermotherapy, radiofrequency ablation, microwave ablation, cryotherapy, and localized tumor therapy. The latest developments in the application of minimally invasive therapies in localized neoplastic disease are demonstrated. In the main part of the book, techniques of guiding the applicators to the target structures by use of different imaging tools such as ultrasound, computed tomography and magnetic resonance imaging are discussed. The results are presented for a variety of clinical indications, including liver and lung tumors and metastases and some rather rare conditions involving the kidney, the head and neck, the prostate, and soft tissue structures. A large number of acknowledged experts have contributed to the book, which benefits from a lucid structure and excellent images. (orig.)

The ablated volume and the thermal field distribution in swine vertebral body created by multi-polar radiofrequency ablation: an experiment in vitro

International Nuclear Information System (INIS)

Peng Zhaohong; Zhao Wei; Shen Jin; Hu Jihong; Li Zhaopeng; Wang Tao

2009-01-01

Objective: To observe the extent of bone coagulation and the thermal field distribution created in ablating the swine vertebral bodies in vitro with multi-polar radiofrequency and to discuss the correlation between the electrode position in the vertebral body and the safety of the spinal cord as well as the soft tissue injury around the vertebral body. Methods: Thirty fresh adult porcine vertebrae were randomly and equally divided into two groups. The depth of the electrode needle was 10 mm or 20 mm.When the ablation process reached to a stable state, the temperature at the scheduled spots was estimated. Twenty minutes after ablation, the vertebral body was cut along the electrode needle plane and also along the plane perpendicular to the electrode needle to observe the extent of bone coagulation. Results: The temperature at the scheduled spots reached to a stable state in 3.5 minutes. The more close to the electrode the spot was, the more quickly the temperature rose. No soft tissue injury around the vertebral body was observed in both groups and no spinal cord injury occurred when the electrode needle was 10 mm or 20 mm deep in the vertebral body. Conclusion: In treating vertebral metastases, the radiofrequency ablation is safe and reliable if the posterior wall of the vertebral body remains intact. (authors)

Analysis of current diffusive ballooning mode in tokamaks

International Nuclear Information System (INIS)

Uchida, M.; Fukuyama, A.; Itoh, S.-I.; Yagi, M.

1999-12-01

The effect of finite gyroradius on the current diffusive ballooning mode is examined. Starting from the reduced MHD equations including turbulent transports, coupling with drift motion and finite gyroradius effect of ions, we derive a ballooning mode equation with complex transport coefficients. The eigenfrequency, saturation level and thermal diffusivity are evaluated numerically from the marginal stability condition. Preliminary results of their parameter dependence is presented. (author)

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

Science.gov (United States)

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

2009-05-01

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

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

Science.gov (United States)

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

2018-03-01

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

Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

Energy Technology Data Exchange (ETDEWEB)

Baek, Jung Hwan; Lee, Jeong Hyun [University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of); Valcavi, Roberto [Endocrinology Division and Thyroid Disease Center, Arcispedale Santa Maria Nuova, Reggio Emilia (Italy); Pacella, Claudio M. [Diagnostic Imaging and Interventional Radiology Department, Ospedale Regina Apostolorum, Albano Laziale-Rome (IT); Rhim, Hyun Chul [Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Na, Dong Kyu [Human Medical Imaging and Intervention Center, Seoul (Korea, Republic of)

2011-10-15

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

Postoperative Biliary Leak Treated with Chemical Bile Duct Ablation Using Absolute Ethanol: A Report of Two Cases.

Science.gov (United States)

Sasaki, Maho; Hori, Tomohide; Furuyama, Hiroaki; Machimoto, Takafumi; Hata, Toshiyuki; Kadokawa, Yoshio; Ito, Tatsuo; Kato, Shigeru; Yasukawa, Daiki; Aisu, Yuki; Kimura, Yusuke; Takamatsu, Yuichi; Kitano, Taku; Yoshimura, Tsunehiro

2017-08-08

BACKGROUND Postoperative bile duct leak following hepatobiliary and pancreatic surgery can be intractable, and the postoperative course can be prolonged. However, if the site of the leak is in the distal bile duct in the main biliary tract, the therapeutic options may be limited. Injection of absolute ethanol into the bile duct requires correct identification of the bile duct, and balloon occlusion is useful to avoid damage to the surrounding tissues, even in cases with non-communicating biliary fistula and bile leak. CASE REPORT Two cases of non-communicating biliary fistula and bile leak are presented; one case following pancreaticoduodenectomy (Whipple's procedure), and one case following laparoscopic cholecystectomy. Both cases were successfully managed by chemical bile duct ablation with absolute ethanol. In the first case, the biliary leak occurred from a fistula of the right posterior biliary tract following pancreaticoduodenectomy. Cannulation of the leaking bile duct and balloon occlusion were achieved via a percutaneous route, and seven ablation sessions using absolute ethanol were required. In the second case, perforation of the bile duct branch draining hepatic segment V occurred following laparoscopic cholecystectomy. Cannulation of the bile duct and balloon occlusion were achieved via a transhepatic route, and seven ablation sessions using absolute ethanol were required. CONCLUSIONS Chemical ablation of the bile duct using absolute ethanol is an effective treatment for biliary leak following hepatobiliary and pancreatic surgery, even in cases with non-communicating biliary fistula. Identification of the bile duct leak is required before ethanol injection to avoid damage to the surrounding tissues.

Fracture in Phenolic Impregnated Carbon Ablator

Science.gov (United States)

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.

Moldable cork ablation material

Science.gov (United States)

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.

Effects of pressure rise on cw laser ablation of tissue

Science.gov (United States)

LeCarpentier, Gerald L.; Motamedi, Massoud; Welch, Ashley J.

1991-06-01

The objectives of this research were to identify mechanisms responsible for the initiation of continuous wave (cw) laser ablation of tissue and investigate the role of pressure in the ablation process. Porcine aorta samples were irradiated in a chamber pressurized from 1 X 10-4 to 12 atmospheres absolute pressure. Acrylic and Zn-Se windows in the experimental pressure chamber allowed video and infrared cameras to simultaneously record mechanical and thermal events associated with cw argon laser ablation of these samples. Video and thermal images of tissue slabs documented the explosive nature of cw laser ablation of soft biological media and revealed similar ablation threshold temperatures and ablation onset times under different environmental pressures; however, more violent initiation explosions with decreasing environmental pressures were observed. These results suggest that ablation initiates with thermal alterations in the mechanical strength of the tissue and proceeds with an explosion induced by the presence superheated liquid within the tissue.

Wind-Driven Montgolfiere Balloons for Mars

Science.gov (United States)

Jones, Jack A.; Fairbrother, Debora; Lemieux, Aimee; Lachenmeier, Tim; Zubrin, Robert

2005-01-01

Solar Montgolfiere balloons, or solar-heated hot air balloons have been evaluated by use on Mars for about 5 years. In the past, JPL has developed thermal models that have been confirmed, as well as developed altitude control systems to allow the balloons to float over the landscape or carry ground sampling instrumentation. Pioneer Astronautics has developed and tested a landing system for Montgolfieres. JPL, together with GSSL. have successfully deployed small Montgolfieres (<15-m diameter) in the earth's stratosphere, where conditions are similar to a Mars deployment. Two larger Montgolfieres failed, however, and a series of larger scale Montgolfieres is now planned using stronger, more uniform polyethylene bilaminate, combined with stress-reducing ripstitch and reduced parachute deceleration velocities. This program, which is presently under way, is a joint effort between JPL, WFF, and GSSL, and is planned for completion in three years.

A thermal model for nanosecond pulsed laser ablation of aluminum

Directory of Open Access Journals (Sweden)

Yu Zhang

2017-07-01

Full Text Available In order to simulate the nanosecond pulsed laser ablation of aluminum, a novel model was presented for the target ablation and plume expansion. The simulation of the target ablation was based on one-dimensional heat conduction, taking into account temperature dependent material properties, phase transition, dielectric transition and phase explosion. While the simulation of the plume expansion was based on one-dimensional gas-dynamical equation, taking into account ionization, plume absorption and shielding. By coupling the calculations of the target ablation and plume expansion, the characteristics of the target and plume were obtained. And the calculated results were in good agreement with the experimental data, in terms of ablation threshold and depth within the fluence range of the tested laser. Subsequently, investigations were carried out to analyze the mechanisms of nanosecond pulsed laser ablation. The calculated results showed that the maximum surface temperature remained at about 90% of the critical temperature (0.9Tc due to phase explosion. Moreover, the plume shielding has significant effects on the laser ablation, and the plume shielding proportion increase as the laser fluence increasing. The ambient pressure belows 100 Pa is more suitable for laser ablation, which can obtained larger ablation depth.

Actual role of radiofrequency ablation of liver metastases

Energy Technology Data Exchange (ETDEWEB)

Pereira, Philippe L. [Eberhard-Karls-University of Tuebingen, Department of Diagnostic Radiology, Tuebingen (Germany)

2007-08-15

The liver is, second only to lymph nodes, the most common site for metastatic disease irrespective of the primary tumour. More than 50% of all patients with malignant diseases will develop liver metastases with a significant morbidity and mortality. Although the surgical resection leads to an improved survival in patients with colorectal metastases, only approximately 20% of patients are eligible for surgery. Thermal ablation and especially radiofrequency ablation emerge as an important additional therapy modality for the treatment of liver metastases. RF ablation shows a benefit in life expectancy and may lead in a selected patient group to cure. Percutaneous RF ablation appears safer (versus cryotherapy), easier (versus laser), and more effective (versus ethanol instillation and transarterial chemoembolisation) compared with other minimally invasive procedures. RF ablation can be performed by a percutaneous, laparoscopical or laparotomic approach, and may be potentially combined with chemotherapy and surgery. At present ideal candidates have tumours with a maximum diameter less than 3.5 cm. An untreatable primary tumour or a systemic disease represents contraindications for performing local therapies. Permanent technical improvements of thermal ablation devices and a better integration of thermal ablation in the overall patient care may lead to prognosis improvement in patients with liver metastases. (orig.)

Actual role of radiofrequency ablation of liver metastases

International Nuclear Information System (INIS)

Pereira, Philippe L.

2007-01-01

The liver is, second only to lymph nodes, the most common site for metastatic disease irrespective of the primary tumour. More than 50% of all patients with malignant diseases will develop liver metastases with a significant morbidity and mortality. Although the surgical resection leads to an improved survival in patients with colorectal metastases, only approximately 20% of patients are eligible for surgery. Thermal ablation and especially radiofrequency ablation emerge as an important additional therapy modality for the treatment of liver metastases. RF ablation shows a benefit in life expectancy and may lead in a selected patient group to cure. Percutaneous RF ablation appears safer (versus cryotherapy), easier (versus laser), and more effective (versus ethanol instillation and transarterial chemoembolisation) compared with other minimally invasive procedures. RF ablation can be performed by a percutaneous, laparoscopical or laparotomic approach, and may be potentially combined with chemotherapy and surgery. At present ideal candidates have tumours with a maximum diameter less than 3.5 cm. An untreatable primary tumour or a systemic disease represents contraindications for performing local therapies. Permanent technical improvements of thermal ablation devices and a better integration of thermal ablation in the overall patient care may lead to prognosis improvement in patients with liver metastases. (orig.)

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

Science.gov (United States)

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

2017-02-01

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

Ablative skin resurfacing.

Science.gov (United States)

Agrawal, Nidhi; Smith, Greg; Heffelfinger, Ryan

2014-02-01

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

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

Science.gov (United States)

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

2018-02-01

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

Epicardial phrenic nerve displacement during catheter ablation of atrial and ventricular arrhythmias: procedural experience and outcomes.

Science.gov (United States)

Kumar, Saurabh; Barbhaiya, Chirag R; Baldinger, Samuel H; Koplan, Bruce A; Maytin, Melanie; Epstein, Laurence M; John, Roy M; Michaud, Gregory F; Tedrow, Usha B; Stevenson, William G

2015-08-01

Arrhythmia origin in close proximity to the phrenic nerve (PN) can hinder successful catheter ablation. We describe our approach with epicardial PN displacement in such instances. PN displacement via percutaneous pericardial access was attempted in 13 patients (age 49±16 years, 9 females) with either atrial tachycardia (6 patients) or atrial fibrillation triggered from a superior vena cava focus (1 patient) adjacent to the right PN or epicardial ventricular tachycardia origin adjacent to the left PN (6 patients). An epicardially placed steerable sheath/4 mm-catheter combination (5 patients) or a vascular or an esophageal balloon (8 patients) was ultimately successful. Balloon placement was often difficult requiring manipulation via a steerable sheath. In 2 ventricular tachycardia cases, absence of PN capture was achieved only once the balloon was directly over the ablation catheter. In 3 atrial tachycardia patients, PN displacement was not possible with a balloon; however, a steerable sheath/catheter combination was ultimately successful. PN displacement allowed acute abolishment of all targeted arrhythmias. No PN injury occurred acutely or in follow up. Two patients developed acute complications (pleuro-pericardial fistula 1 and pericardial bleeding 1). Survival free of target arrhythmia was achieved in all atrial tachycardia patients; however, a nontargeted ventricular tachycardia recurred in 1 patient at a median of 13 months' follow up. Arrhythmias originating in close proximity to the PN can be targeted successfully with PN displacement with an epicardially placed steerable sheath/catheter combination, or balloon, but this strategy can be difficult to implement. Better tools for phrenic nerve protection are desirable. © 2015 American Heart Association, Inc.

A framework for continuous target tracking during MR-guided high intensity focused ultrasound thermal ablations in the abdomen

NARCIS (Netherlands)

Zachiu, Cornel; Denis de Senneville, Baudouin; Dmitriev, Ivan D.; Moonen, Chrit T.W.; Ries, Mario

2017-01-01

Background: During lengthy magnetic resonance-guided high intensity focused ultrasound (MRg-HIFU) thermal ablations in abdominal organs, the therapeutic work-flow is frequently hampered by various types of physiological motion occurring at different time-scales. If left un-addressed this can lead to

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

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Scott M Thompson

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

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

Science.gov (United States)

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

2006-01-01

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

Influence of wavelength and pulse duration on peripheral thermal and mechanical damage to dentin and alveolar bone during IR laser ablation

Science.gov (United States)

Lee, C.; Ragadio, Jerome N.; Fried, Daniel

2000-03-01

The objective of this study was to measure the peripheral thermal damage produced during the laser ablation of alveolar bone and dentin for clinically relevant IR laser systems. Previous studies have demonstrated that a char layer produced around the laser incision site can inhibit the wound healing process. Moreover, in the case of dentin, a char layer is unsightly and is difficult to bond to with restorative materials. Thermal damage was assessed using polarized light microscopy for laser pulse widths from 500 ns to 300 microseconds at 2.94 micrometer and 9.6 micrometer. Water- cooling was not employed to alleviate thermal damage during the laser irradiation. At 9.6 micrometer, minimal thermal damage was observed for pulse widths on the order of the thermal relaxation time of the deposited laser energy in the tissue, 3 - 4 microseconds, and peripheral thermal damage increased with increasing pulse duration. At 2.94 micrometer, thermal damage was minimal for the Q-switched (500 ns) laser system. This study shows that 9.6 micrometer CO2 laser pulses with pulse widths of 5 - 10 microseconds are well suited for the efficient ablation of dentin and bone with minimal peripheral damage. This work was supported by NIH/NIDCR R29DE12091.

Hydrodynamic instabilities in an ablation front

International Nuclear Information System (INIS)

Piriz, A R; Portugues, R F

2004-01-01

The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved

Hydrodynamic instabilities in an ablation front

Energy Technology Data Exchange (ETDEWEB)

Piriz, A R; Portugues, R F [E.T.S.I. Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)

2004-06-01

The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved.

Fiber-Optic Temperature and Pressure Sensors Applied to Radiofrequency Thermal Ablation in Liver Phantom: Methodology and Experimental Measurements

Directory of Open Access Journals (Sweden)

Daniele Tosi

2015-01-01

Full Text Available Radiofrequency thermal ablation (RFA is a procedure aimed at interventional cancer care and is applied to the treatment of small- and midsize tumors in lung, kidney, liver, and other tissues. RFA generates a selective high-temperature field in the tissue; temperature values and their persistency are directly related to the mortality rate of tumor cells. Temperature measurement in up to 3–5 points, using electrical thermocouples, belongs to the present clinical practice of RFA and is the foundation of a physical model of the ablation process. Fiber-optic sensors allow extending the detection of biophysical parameters to a vast plurality of sensing points, using miniature and noninvasive technologies that do not alter the RFA pattern. This work addresses the methodology for optical measurement of temperature distribution and pressure using four different fiber-optic technologies: fiber Bragg gratings (FBGs, linearly chirped FBGs (LCFBGs, Rayleigh scattering-based distributed temperature system (DTS, and extrinsic Fabry-Perot interferometry (EFPI. For each instrument, methodology for ex vivo sensing, as well as experimental results, is reported, leading to the application of fiber-optic technologies in vivo. The possibility of using a fiber-optic sensor network, in conjunction with a suitable ablation device, can enable smart ablation procedure whereas ablation parameters are dynamically changed.

Benign thyroid nodule unresponsive to radiofrequency ablation treated with laser ablation: a case report.

Science.gov (United States)

Oddo, Silvia; Balestra, Margherita; Vera, Lara; Giusti, Massimo

2018-05-11

Radiofrequency ablation and laser ablation are safe and effective techniques for reducing thyroid nodule volume, neck symptoms, and cosmetic complaints. Therapeutic success is defined as a nodule reduction > 50% between 6 and 12 months after the procedure, but a percentage of nodules inexplicably do not respond to thermal ablation. We describe the case of a young Caucasian woman with a solid benign thyroid nodule who refused surgery and who had undergone radiofrequency ablation in 2013. The nodule did not respond in terms of either volume reduction or improvement in neck symptoms. After 2 years, given the patient's continued refusal of thyroidectomy, we proposed laser ablation. The nodule displayed a significant volume reduction (- 50% from radiofrequency ablation baseline volume, - 57% from laser ablation baseline), and the patient reported a significant improvement in neck symptoms (from 6/10 to 1/10 on a visual analogue scale). We conjecture that some benign thyroid nodules may be intrinsically resistant to necrosis when one specific ablation technique is used, but may respond to another technique. To the best of our knowledge, this is the first description of the effect of performing a different percutaneous ablation technique in a nodule that does not respond to radiofrequency ablation.

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

Science.gov (United States)

2009-04-01

11. Khokhlova, V.A., et al., Effects of nonlinear propagation, cavitation , and boiling in lesion formation by high intensity focused ultrasound in...intensity focused ultrasound (HIFU) has been developed as an emerging non-invasive strategy for cancer treatment by thermal ablation of tumor tissue. The...Concepts, Seattle, WA) operating at its fundamental frequency (1.1 MHz) or its third harmonics (3.3 MHz). The ultrasound imaging system was a 5/7

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

Science.gov (United States)

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

2010-02-01

A mechanically scanned CO2 laser operated at high laser pulse repetition rates can be used to rapidly and precisely remove dental decay. This study aims to determine whether these laser systems can safely ablate enamel and dentin without excessive heat accumulation and peripheral thermal damage. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. Samples were derived from noncarious extracted molars. Pulpal temperatures were recorded using microthermocouples situated at the pulp chamber roof of samples (n=12), which were occlusally ablated using a rapid-scanning, water-cooled 300 Hz CO2 laser over a two minute time course. The mechanical strength of facially ablated dentin (n=10) was determined via four-point bend test and compared to control samples (n=10) prepared with 320 grit wet sand paper to simulate conventional preparations. Composite-to-enamel bond strength was measured via single-plane shear test for ablated/non-etched (n=10) and ablated/acid-etched (n=8) samples and compared to control samples (n=9) prepared by 320 grit wet sanding. Thermocouple measurements indicated that the temperature remained below ambient temperature at 19.0°C (s.d.=0.9) if water-cooling was used. There was no discoloration of either dentin and enamel, the treated surfaces were uniformly ablated and there were no cracks observable on the laser treated surfaces. Fourpoint bend tests yielded mean mechanical strengths of 18.2 N (s.d.=4.6) for ablated dentin and 18.1 N (s.d.=2.7) for control (p>0.05). Shear tests yielded mean bond strengths of 31.2 MPa (s.d.=2.5, penamel without excessive heat accumulation and with minimal thermal damage. It is not clear whether the small (16%) but statistically significant reduction in the shear bond strength to enamel is clinically significant since the mean shear bond strength exceeded 30 MPa.

Chemothermal Therapy for Localized Heating and Ablation of Tumor

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Zhong-Shan Deng

2013-01-01

Full Text Available Chemothermal therapy is a new hyperthermia treatment on tumor using heat released from exothermic chemical reaction between the injected reactants and the diseased tissues. With the highly minimally invasive feature and localized heating performance, this method is expected to overcome the ubiquitous shortcomings encountered by many existing hyperthermia approaches in ablating irregular tumor. This review provides a relatively comprehensive review on the latest advancements and state of the art in chemothermal therapy. The basic principles and features of two typical chemothermal ablation strategies (acid-base neutralization-reaction-enabled thermal ablation and alkali-metal-enabled thermal/chemical ablation are illustrated. The prospects and possible challenges facing chemothermal ablation are analyzed. The chemothermal therapy is expected to open many clinical possibilities for precise tumor treatment in a minimally invasive way.

Microwave ablation of renal tumors: state of the art and development trends.

Science.gov (United States)

Floridi, Chiara; De Bernardi, Irene; Fontana, Federico; Muollo, Alessandra; Ierardi, Anna Maria; Agostini, Andrea; Fonio, Paolo; Squillaci, Ettore; Brunese, Luca; Fugazzola, Carlo; Carrafiello, Gianpaolo

2014-07-01

In the last decades an increased incidence of new renal tumor cases has been for clinically localized, small tumors elderly patients, with medical comorbidities whom the risk of surgical complications may pose a greater risk of death than that due to the tumor itself. In these patients, unsuitable for surgical approach, thermal ablation represents a valid alternative to traditional surgery. Thermal ablation is a less invasive, less morbid treatment option thanks to reduced blood loss, lower incidence of complications during the procedure and a less long convalescence. At present, the most widely used thermal ablative techniques are cryoablation, radiofrequency ablation and microwave ablation (MWA). MWA offers many benefits of other ablation techniques and offers several other advantages: higher intratumoral temperatures, larger tumor ablation volumes, faster ablation times, the ability to use multiple applicators simultaneously, optimal heating of cystic masses and tumors close to the vessels and less procedural pain. This review aims to provide the reader with an overview about the state of the art of microwave ablation for renal tumors and to cast a glance on the new development trends of this technique.

Endoluminal ultrasound applicators for MR-guided thermal ablation of pancreatic tumors: Preliminary design and evaluation in a porcine pancreas model

International Nuclear Information System (INIS)

Adams, Matthew S.; Diederich, Chris J.; Salgaonkar, Vasant A.; Jones, Peter D.; Plata-Camargo, Juan; Sommer, Graham; Pauly, Kim Butts; Pascal-Tenorio, Aurea; Bouley, Donna M.; Chen, Hsin-Yu

2016-01-01

Purpose: Endoluminal ultrasound may serve as a minimally invasive option for delivering thermal ablation to pancreatic tumors adjacent to the stomach or duodenum. The objective of this study was to explore the basic feasibility of this treatment strategy through the design, characterization, and evaluation of proof-of-concept endoluminal ultrasound applicators capable of placement in the gastrointestinal (GI) lumen for volumetric pancreas ablation under MR guidance. Methods: Two variants of the endoluminal applicator, each containing a distinct array of two independently powered transducers (10 × 10 mm 3.2 MHz planar; or 8 × 10 × 20 mm radius of curvature 3.3 MHz curvilinear geometries) at the distal end of a meter long flexible catheter assembly, were designed and fabricated. Transducers and circulatory water flow for acoustic coupling and luminal cooling were contained by a low-profile polyester balloon covering the transducer assembly fixture. Each applicator incorporated miniature spiral MR coils and mechanical features (guiding tips and hinges) to facilitate tracking and insertion through the GI tract under MRI guidance. Acoustic characterization of each device was performed using radiation force balance and hydrophone measurements. Device delivery into the upper GI tract, adjacent to the pancreas, and heating characteristics for treatment of pancreatic tissue were evaluated in MR-guided ex vivo and in vivo porcine experiments. MR guidance was utilized for anatomical target identification, tracking/positioning of the applicator, and MR temperature imaging (MRTI) for PRF-based multislice thermometry, implemented in the real-time RTHawk software environment. Results: Force balance and hydrophone measurements indicated efficiencies of 48.8% and 47.8% and −3 dB intensity beam-widths of 3.2 and 1.2 mm for the planar and curvilinear transducers, respectively. Ex vivo studies on whole-porcine carcasses revealed capabilities of producing ablative temperature rise

Endoluminal ultrasound applicators for MR-guided thermal ablation of pancreatic tumors: Preliminary design and evaluation in a porcine pancreas model

Energy Technology Data Exchange (ETDEWEB)

Adams, Matthew S., E-mail: matt.adams@ucsf.edu; Diederich, Chris J. [Thermal Therapy Research Group, University of California, San Francisco, 2340 Sutter Street, S341, San Francisco, California 94115 and The UC Berkeley - UCSF Graduate Program in Bioengineering, University of California, Berkeley, and University of California, San Francisco, California 94115 (United States); Salgaonkar, Vasant A.; Jones, Peter D. [Thermal Therapy Research Group, University of California, San Francisco, 2340 Sutter Street, S341, San Francisco, California 94115 (United States); Plata-Camargo, Juan; Sommer, Graham; Pauly, Kim Butts [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Pascal-Tenorio, Aurea; Bouley, Donna M. [Department of Comparative Medicine, Stanford University, Stanford, California 94305 (United States); Chen, Hsin-Yu [The UC Berkeley - UCSF Graduate Program in Bioengineering, University of California, Berkeley, and University of California, San Francisco, California 94115 (United States)

2016-07-15

Purpose: Endoluminal ultrasound may serve as a minimally invasive option for delivering thermal ablation to pancreatic tumors adjacent to the stomach or duodenum. The objective of this study was to explore the basic feasibility of this treatment strategy through the design, characterization, and evaluation of proof-of-concept endoluminal ultrasound applicators capable of placement in the gastrointestinal (GI) lumen for volumetric pancreas ablation under MR guidance. Methods: Two variants of the endoluminal applicator, each containing a distinct array of two independently powered transducers (10 × 10 mm 3.2 MHz planar; or 8 × 10 × 20 mm radius of curvature 3.3 MHz curvilinear geometries) at the distal end of a meter long flexible catheter assembly, were designed and fabricated. Transducers and circulatory water flow for acoustic coupling and luminal cooling were contained by a low-profile polyester balloon covering the transducer assembly fixture. Each applicator incorporated miniature spiral MR coils and mechanical features (guiding tips and hinges) to facilitate tracking and insertion through the GI tract under MRI guidance. Acoustic characterization of each device was performed using radiation force balance and hydrophone measurements. Device delivery into the upper GI tract, adjacent to the pancreas, and heating characteristics for treatment of pancreatic tissue were evaluated in MR-guided ex vivo and in vivo porcine experiments. MR guidance was utilized for anatomical target identification, tracking/positioning of the applicator, and MR temperature imaging (MRTI) for PRF-based multislice thermometry, implemented in the real-time RTHawk software environment. Results: Force balance and hydrophone measurements indicated efficiencies of 48.8% and 47.8% and −3 dB intensity beam-widths of 3.2 and 1.2 mm for the planar and curvilinear transducers, respectively. Ex vivo studies on whole-porcine carcasses revealed capabilities of producing ablative temperature rise

Radiofrequency thermal ablation of a metastatic lung nodule

Energy Technology Data Exchange (ETDEWEB)

Highland, Adrian M. [Department of Clinical Radiology, Hull Royal Infirmary, Anlaby Road, Hull, HU3 2JZ (United Kingdom); Mack, Paul [Diana Princess of Wales Hospital, Scartho Road, Grimsby, DN33 2BA (United Kingdom); Breen, David J. [Department of Radiology, Southampton University Hospitals, Tremona Road, Southampton, SO16 6YD (United Kingdom)

2002-07-01

Pulmonary metastases are a common finding in patients with colonic adenocarcinoma. We report the treatment of a metastatic lung nodule with radiofrequency (RF) ablation under CT guidance. This case illustrates the use of RF ablation in a patient in whom surgical resection was no longer possible and where chemotherapy was unlikely to produce benefit. This technique may offer a viable method of cytoreduction when other treatments have not succeeded. (orig.)

Radiofrequency thermal ablation of a metastatic lung nodule

International Nuclear Information System (INIS)

Highland, Adrian M.; Mack, Paul; Breen, David J.

2002-01-01

Pulmonary metastases are a common finding in patients with colonic adenocarcinoma. We report the treatment of a metastatic lung nodule with radiofrequency (RF) ablation under CT guidance. This case illustrates the use of RF ablation in a patient in whom surgical resection was no longer possible and where chemotherapy was unlikely to produce benefit. This technique may offer a viable method of cytoreduction when other treatments have not succeeded. (orig.)

The UK MT-3 ballooning test in the Battelle NRU loop

International Nuclear Information System (INIS)

Gibson, I.H.; Coddington, P.; Healey, T.; Mann, C.A.

1982-04-01

The ballooning response of PWR fuel rods under postulated LOCA conditions has been the subject of intensive investigations. The UK MT-3 ballooning test was a co-operative international exercise which was technically very successful. This report describes the pre-test planning and calculations carried out in the UK and then describes in some detail the thermal hydraulic and clad deformation results. (U.K.)

Enhanced Radiofrequency Ablation With Magnetically Directed Metallic Nanoparticles.

Science.gov (United States)

Nguyen, Duy T; Tzou, Wendy S; Zheng, Lijun; Barham, Waseem; Schuller, Joseph L; Shillinglaw, Benjamin; Quaife, Robert A; Sauer, William H

2016-05-01

Remote heating of metal located near a radiofrequency ablation source has been previously demonstrated. Therefore, ablation of cardiac tissue treated with metallic nanoparticles may improve local radiofrequency heating and lead to larger ablation lesions. We sought to evaluate the effect of magnetic nanoparticles on tissue sensitivity to radiofrequency energy. Ablation was performed using an ablation catheter positioned with 10 g of force over prepared ex vivo specimens. Tissue temperatures were measured and lesion volumes were acquired. An in vivo porcine thigh model was used to study systemically delivered magnetically guided iron oxide (FeO) nanoparticles during radiofrequency application. Magnetic resonance imaging and histological staining of ablated tissue were subsequently performed as a part of ablation lesion analysis. Ablation of ex vivo myocardial tissue treated with metallic nanoparticles resulted in significantly larger lesions with greater impedance changes and evidence of increased thermal conductivity within the tissue. Magnet-guided localization of FeO nanoparticles within porcine thigh preps was demonstrated by magnetic resonance imaging and iron staining. Irrigated ablation in the regions with greater FeO, after FeO infusion and magnetic guidance, created larger lesions without a greater incidence of steam pops. Metal nanoparticle infiltration resulted in significantly larger ablation lesions with altered electric and thermal conductivity. In vivo magnetic guidance of FeO nanoparticles allowed for facilitated radiofrequency ablation without direct infiltration into the targeted tissue. Further research is needed to assess the clinical applicability of this ablation strategy using metallic nanoparticles for the treatment of cardiac arrhythmias. © 2016 American Heart Association, Inc.

New concepts for interplanetary balloons and blimps, particularly for Titan

Science.gov (United States)

Nott, J.

This paper proposes novel approaches for balloons for planets Titan BALLUTE A balloon or blimp arriving at a planet or moon with an atmosphere might inflate falling under a parachute or after landing Neither is ideal In both cases the envelope must include qualities needed for inflation as well as those for flight A ballute BALLoon parachUTE could be used thus a ballute is like a hot air balloon with a large mouth Initially it fills by ram pressure descending through an atmosphere As proposed it would then be heated by solid propellant It would stop descending and float level with hot air lift It is now a perfect location for inflation without wind or movement through the atmosphere and away from the uncertainties of the surface A ballute could be used over several bodies in the solar system BALLOONS FOR LOW TEMPERATURES Flight in very low temperatures is also discussed Conditions are so different that it is useful to examine basic factors These apply for any planet with low temperature and weather calm enough for balloons or blimps First for terrestrial hot air balloons thermal radiation is usually the dominant way heat is lost But radiation rises with the 4th power of absolute temperature At Titan radiation will be one or two orders of magnitude smaller Also the dense atmosphere allows small balloons small temperature differences So convection is small It appears a hot air balloon can easily be heated by a radioactive source likely carried to make electricity Pinholes are not important in such a balloon

Image-Guided Spinal Ablation: A Review

Energy Technology Data Exchange (ETDEWEB)

Tsoumakidou, Georgia, E-mail: gtsoumakidou@yahoo.com; Koch, Guillaume, E-mail: guillaume.koch@chru-strasbourg.fr; Caudrelier, Jean, E-mail: jean.caudrelier@chru-strasbourg.fr; Garnon, Julien, E-mail: julien.garnon@chru-strasbourg.fr; Cazzato, Roberto Luigi, E-mail: roberto-luigi.cazzato@chru-strasbourg.fr; Edalat, Faramarz, E-mail: faramarz.edalat@gmail.com; Gangi, Afshin, E-mail: gangi@unistra.fr [Strasbourg University Hospital (France)

2016-09-15

The image-guided thermal ablation procedures can be used to treat a variety of benign and malignant spinal tumours. Small size osteoid osteoma can be treated with laser or radiofrequency. Larger tumours (osteoblastoma, aneurysmal bone cyst and metastasis) can be addressed with radiofrequency or cryoablation. Results on the literature of spinal microwave ablation are scarce, and thus it should be used with caution. A distinct advantage of cryoablation is the ability to monitor the ice-ball by intermittent CT or MRI. The different thermal insulation, temperature and electrophysiological monitoring techniques should be applied. Cautious pre-procedural planning and intermittent intra-procedural monitoring of the ablation zone can help reduce neural complications. Tumour histology, patient clinical-functional status and life-expectancy should define the most efficient and least disabling treatment option.

Computational modeling of ultra-short-pulse ablation of enamel

Energy Technology Data Exchange (ETDEWEB)

London, R.A.; Bailey, D.S.; Young, D.A. [and others

1996-02-29

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 sec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

CT thermometry for cone-beam CT guided ablation

Science.gov (United States)

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.

Nonlinear Analysis of Two-phase Circumferential Motion in the Ablation Circumstance

Science.gov (United States)

Xiao-liang, Xu; Hai-ming, Huang; Zi-mao, Zhang

2010-05-01

In aerospace craft reentry and solid rocket propellant nozzle, thermal chemistry ablation is a complex process coupling with convection, heat transfer, mass transfer and chemical reaction. Based on discrete vortex method (DVM), thermal chemical ablation model and particle kinetic model, a computational module dealing with the two-phase circumferential motion in ablation circumstance is designed, the ablation velocity and circumferential field can be thus calculated. The calculated nonlinear time series are analyzed in chaotic identification method: relative chaotic characters such as correlation dimension and the maximum Lyapunov exponent are calculated, fractal dimension of vortex bulbs and particles distributions are also obtained, thus the nonlinear ablation process can be judged as a spatiotemporal chaotic process.

Non-thermal effects on femtosecond laser ablation of polymers extracted from the oscillation of time-resolved reflectivity

Energy Technology Data Exchange (ETDEWEB)

Kumada, Takayuki, E-mail: kumada.takayuki@jaea.go.jp; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Nishikino, Masaharu; Yokoyama, Atsushi [Kansai Photon Science Institute, Japan Atomic Energy Agency, Umemidai, Kizugawa, Kyoto 619-0215 (Japan)

2015-06-01

The dynamics of femtosecond laser ablation of transparent polymers were examined using time-resolved reflectivity. When these polymers were irradiated by a pump pulse with fluence above the ablation threshold of 0.8–2.0 J/cm{sup 2}, we observed the oscillation of the reflectivity caused by the interference between the reflected probe pulses from the sample surface and the thin layer due to the non-thermal photomechanical effects of spallation. As the fluence of the pump pulse increased, the separation velocity of the thin layer increased from 6 km/s to the asymptotic value of 11 km/s. It is suggested that the velocities are determined by shock-wave velocities of the photo-excited layer.

Tumor lysis syndrome following endoscopic radiofrequency interstitial thermal ablation of colorectal liver metastases.

LENUS (Irish Health Repository)

Barry, B D

2012-02-03

Radiofrequency interstitial thermal ablation (RITA) provides a palliative option for patients suffering from metastatic liver disease. This procedure can be performed using a laparoscopic approach with laparoscopic ultrasound used to position the RITA probe. We describe a case of laparoscopic RITA performed for colorectal liver metastasis that was complicated by tumor lysis syndrome (TLS) following treatment. We consider RITA to be a safe procedure, as supported by the literature, but where intracorporal tumor lysis is the treatment goal we believe that the systemic release of tumor products can overwhelm the excretory capacity; therefore, TLS is an inevitable consequence in some patients.

Fiber-optic combined FPI/FBG sensors for monitoring of radiofrequency thermal ablation of liver tumors: ex vivo experiments.

Science.gov (United States)

Tosi, Daniele; Macchi, Edoardo Gino; Braschi, Giovanni; Cigada, Alfredo; Gallati, Mario; Rossi, Sandro; Poeggel, Sven; Leen, Gabriel; Lewis, Elfed

2014-04-01

We present a biocompatible, all-glass, 0.2 mm diameter, fiber-optic probe that combines an extrinsic Fabry-Perot interferometry and a proximal fiber Bragg grating sensor; the probe enables dual pressure and temperature measurement on an active 4 mm length, with 40 Pa and 0.2°C nominal accuracy. The sensing system has been applied to monitor online the radiofrequency thermal ablation of tumors in liver tissue. Preliminary experiments have been performed in a reference chamber with uniform heating; further experiments have been carried out on ex vivo porcine liver, which allowed the measurement of a steep temperature gradient and monitoring of the local pressure increase during the ablation procedure.

An experimental study on hepatic ablation using an expandable radio-frequency needle electrode

International Nuclear Information System (INIS)

Choi, Dong Il; Lim, Hyo Keun; Park, Jong Min; Kang, Bo Kyung; Woo, Ji Young; Jang, Hyun Jung; Kim, Seung Hoon; Lee, Won Jae; Park, Cheol Keun; Heo, Jin Seok

1999-01-01

The purpose of this study was to determine the factors influencing on the size of thermal lesions after ablation using an expendable radio-frequency needle electrode in porcine liver. Ablation procedures involved the use of a monopolar radio-frequency generator and 15-G needle electrodes with four and seven retractable hooks (RITA Medical System, Mountain View, Cal., U.S.A.). The ablation protocol in fresh porcine liver comprised of combinations of varying hook deployment, highest set temperature, and ablation time. Following ablation, the maximum diameter of all thermal lesions was measured on a longitudinal section of the specimen. Ten representive lesions were examined by an experienced pathologist. At 3-cm hook deployment of the needle electrode with four lateral hooks, the size of spherical thermal lesions increased substantially with increases in the highest set temperature and ablation time until 11 minutes. After 11 minutes lesion size remained similar, with a maximum diameter of 3.3 cm. At 2-cm hook deployment, sizes decreased to about 2/3 of those at 3 cm , and at 1-cm hook deployment lesions were oblong. At 3-cm hook deployment of a needle electrode with seven hooks, the size of thermal lesions increased with increasing ablation time until 14 minutes, and the maximum diameter was 4.1 cm. Microscopic examination showed a wide zone of degeneration and focal coagulation necrosis. The size of thermal lesions produced by the use of an expandable radio-frequency needle electrode were predictable, varying according to degree of hook deployment, highest set temperature, and ablation time

Phrenic Nerve Injury After Catheter Ablation of Atrial Fibrillation

Directory of Open Access Journals (Sweden)

Jacques Clementy

2007-01-01

Full Text Available Phrenic Nerve Injury (PNI has been well studied by cardiac surgeons. More recently it has been recognized as a potential complication of catheter ablation with a prevalence of 0.11 to 0.48 % after atrial fibrillation (AF ablation. This review will focus on PNI after AF ablation. Anatomical studies have shown a close relationship between the right phrenic nerve and it's proximity to the superior vena cava (SVC, and the antero-inferior part of the right superior pulmonary vein (RSPV. In addition, the proximity of the left phrenic nerve to the left atrial appendage has been well established. Independent of the type of ablation catheter (4mm, 8 mm, irrigated tip, balloon or energy source used (radiofrequency (RF, ultrasound, cryothermia, and laser; the risk of PNI exists during ablation at the critical areas listed above. Although up to thirty-one percent of patients with PNI after AF ablation remain asymptomatic, dyspnea remain the cardinal symptom and is present in all symptomatic patients. Despite the theoretical risk for significant adverse effect on functional status and quality of life, short-term outcomes from published studies appear favorable with 81% of patients with PNI having a complete recovery after 7 ± 7 months.Conclusion: Existing studies have described PNI as an uncommon but avoidable complication in patients undergoing pulmonary vein isolation for AF. Prior to ablation at the SVC, antero-inferior RSPV ostium or the left atrial appendage, pacing should be performed before energy delivery. If phrenic nerve capture is documented, energy delivery should be avoided at this site. Electrophysiologist's vigilance as well as pacing prior to ablation at high risk sites in close proximity to the phrenic nerve are the currently available tools to avoid the complication of PNI.

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

Science.gov (United States)

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

2015-01-01

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

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

Science.gov (United States)

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

2008-11-01

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

Ablation of musculoskeletal metastases: pain palliation, fracture risk reduction, and oligometastatic disease.

Science.gov (United States)

Kurup, Anil Nicholas; Callstrom, Matthew R

2013-12-01

Thermal ablation is an effective, minimally invasive alternative to conventional therapies in the palliation of painful musculoskeletal metastases and an emerging approach to obtain local tumor control in the setting of limited metastatic disease. Various thermal ablation technologies have been applied to bone and soft tissue tumors and may be used in combination with percutaneous cement instillation for skeletal lesions with or at risk for pathologic fracture. This article reviews current practices of percutaneous ablation of musculoskeletal metastases with an emphasis on radiofrequency ablation and cryoablation of painful skeletal metastases. © 2013 Elsevier Inc. All rights reserved.

Low Cost Variable Conductance Heat Pipe for Balloon Payload, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — While continuously increasing in complexity, the payloads of terrestrial high altitude balloons need a thermal management system to reject their waste heat and to...

Ablation of liver metastases by radiofrequency

International Nuclear Information System (INIS)

Baere, T. de

2012-01-01

Radiofrequency is a thermal ablative technique that is most often used percuteanously under image guidance. Thermal damage is obtained through frictional heating of a high frequency current. The maximal volume of destruction obtained in one radiofrequency delivery is around 4 cm and consequently, best indication for treatment are tumours below 3 cm. When compared, radiofrequency and surgical removal for tumours below 25 mm in diameter demonstrated a rate of incomplete resection/ablation of 6% and 7.3% respectively. Median survival after the first radiofrequency of a liver metastasis of CRC is reported to be 24 to 52 months with a 5 years overall survival of 18 to 44%. The median overall survival increases from 22 to 48 months depending on the use of radiofrequency ablation as rescue treatment after failure of others, or as a first line treatment. For patients with a single tumour, less than 4 cm, the survival rates at 1, 3, and 5 years are respectively 97%, 84% and 40%, with a median survival of 50 months. Follow-up imaging requires to use contrast-enhanced CT or MRI, looking for local recurrences evidenced by local foci of enhancement at the periphery of the ablation zone. (author)

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

Science.gov (United States)

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

2017-09-01

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

GHOST balloons around Antarctica

Science.gov (United States)

Stearns, Charles R.

1988-01-01

The GHOST balloon position as a function of time data shows that the atmospheric circulation around the Antarctic Continent at the 100 mb and 200 mb levels is complex. The GHOST balloons supposedly follow the horizontal trajectory of the air at the balloon level. The position of GHOST balloon 98Q for a three month period in 1968 is shown. The balloon moved to within 2 deg of the South Pole on 1 October 1968 and then by 9 December 1968 was 35 deg from the South Pole and close to its position on 1 September 1968. The balloon generally moved from west to east but on two occasions moved in the opposite direction for a few days. The latitude of GHOST balloons 98Q and 149Z which was at 200 mb is given. Both balloons tended to get closer to the South Pole in September and October. Other GHOST balloons at the same pressure and time period may not indicate similar behavior.

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

International Nuclear Information System (INIS)

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

2010-01-01

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.

Prognostic factors for long-term outcome after percutaneous thermal ablation for hepatocellular carcinoma: a survival analysis of 137 consecutive patients

Energy Technology Data Exchange (ETDEWEB)

Xu, H.-X. [Department of Medical Ultrasonics, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Lu, M.-D. [Department of Hepatobiliary Surgery, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Xie, X.-Y. [Department of Medical Ultrasonics, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Yin, X.-Y. [Department of Hepatobiliary Surgery, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Kuang, M. [Department of Hepatobiliary Surgery, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Chen, J.-W. [Department of Hepatobiliary Surgery, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Xu, Z.-F. [Department of Medical Ultrasonics, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China); Liu, G.-J. [Department of Medical Ultrasonics, First Affiliated Hospital, Sun Yat-Sen University, Guangzhou (China)

2005-09-01

AIM: To identify prognostic factors for long-term outcome for patients with hepatocellular carcinoma (HCC) after percutaneous microwave or radiofrequency ablation. MATERIALS AND METHODS: In total, 137 consecutive patients with HCC underwent microwave or radiofrequency ablation with curative intent; 16 possible prognostic factors were evaluated for their association with overall survival (OS) and disease-free survival (DFS) using univariate and multivariate analysis. RESULTS: The median OS and DFS were 27.0 months and 8.2 months, respectively. OS rates for all patients at 1, 2, 3, 4 and 5 years were 73.9%, 52.1%, 42.8%, 26.2% and 20.1%, respectively. DFS rates at 1, 2, 3 and 4 years were 38.1%, 21.9%, 18.8%, and 14.1%, respectively. Pretreatment serum alpha-fetoprotein (AFP) >200 ng/ml, pretreatment serum albumin {<=}35 g/dl, liver function Child's class C and incomplete ablation were found to be significant predictors for OS by univariate analysis. Using multivariate analysis, incomplete ablation was identified to be the most significant independent predictor for OS. Other independent predictors for OS were serum albumin level, serum AFP level and Child-Pugh classification. Recurrence after hepatectomy and prothrombin time >14 s were identified to be significant predictors for DFS by univariate analysis, and the former was the only independent predictor for DFS by multivariate analysis. CONCLUSION: Prognosis for patients with HCC after thermal ablation with curative intent was determined by treatment response to ablation, pretreatment serum AFP, and liver function reserve. Tumour response to treatment was the most predictive factor for long-term survival and was related to tumour size, thus careful selection of patients for ablation therapy is recommended.

Prognostic factors for long-term outcome after percutaneous thermal ablation for hepatocellular carcinoma: a survival analysis of 137 consecutive patients

International Nuclear Information System (INIS)

Xu, H.-X.; Lu, M.-D.; Xie, X.-Y.; Yin, X.-Y.; Kuang, M.; Chen, J.-W.; Xu, Z.-F.; Liu, G.-J.

2005-01-01

AIM: To identify prognostic factors for long-term outcome for patients with hepatocellular carcinoma (HCC) after percutaneous microwave or radiofrequency ablation. MATERIALS AND METHODS: In total, 137 consecutive patients with HCC underwent microwave or radiofrequency ablation with curative intent; 16 possible prognostic factors were evaluated for their association with overall survival (OS) and disease-free survival (DFS) using univariate and multivariate analysis. RESULTS: The median OS and DFS were 27.0 months and 8.2 months, respectively. OS rates for all patients at 1, 2, 3, 4 and 5 years were 73.9%, 52.1%, 42.8%, 26.2% and 20.1%, respectively. DFS rates at 1, 2, 3 and 4 years were 38.1%, 21.9%, 18.8%, and 14.1%, respectively. Pretreatment serum alpha-fetoprotein (AFP) >200 ng/ml, pretreatment serum albumin ≤35 g/dl, liver function Child's class C and incomplete ablation were found to be significant predictors for OS by univariate analysis. Using multivariate analysis, incomplete ablation was identified to be the most significant independent predictor for OS. Other independent predictors for OS were serum albumin level, serum AFP level and Child-Pugh classification. Recurrence after hepatectomy and prothrombin time >14 s were identified to be significant predictors for DFS by univariate analysis, and the former was the only independent predictor for DFS by multivariate analysis. CONCLUSION: Prognosis for patients with HCC after thermal ablation with curative intent was determined by treatment response to ablation, pretreatment serum AFP, and liver function reserve. Tumour response to treatment was the most predictive factor for long-term survival and was related to tumour size, thus careful selection of patients for ablation therapy is recommended

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

Science.gov (United States)

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

2008-05-01

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

Hydrodynamic model for ultra-short pulse ablation of hard dental tissue

Energy Technology Data Exchange (ETDEWEB)

London, R.A.; Bailey, D.S.; Young, D.A.; Alley, W.E.; Feit, M.D.; Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Neev, J. [Beckman Laser Inst., Irvine, CA (United States)

1996-02-29

A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 fsec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

Sprayable Phase Change Coating Thermal Protection Material

Science.gov (United States)

Richardson, Rod W.; Hayes, Paul W.; Kaul, Raj

2005-01-01

NASA has expressed a need for reusable, environmentally friendly, phase change coating that is capable of withstanding the heat loads that have historically required an ablative thermal insulation. The Space Shuttle Program currently relies on ablative materials for thermal protection. The problem with an ablative insulation is that, by design, the material ablates away, in fulfilling its function of cooling the underlying substrate, thus preventing the insulation from being reused from flight to flight. The present generation of environmentally friendly, sprayable, ablative thermal insulation (MCC-l); currently use on the Space Shuttle SRBs, is very close to being a reusable insulation system. In actual flight conditions, as confirmed by the post-flight inspections of the SRBs, very little of the material ablates. Multi-flight thermal insulation use has not been qualified for the Space Shuttle. The gap that would have to be overcome in order to implement a reusable Phase Change Coating (PCC) is not unmanageable. PCC could be applied robotically with a spray process utilizing phase change material as filler to yield material of even higher strength and reliability as compared to MCC-1. The PCC filled coatings have also demonstrated potential as cryogenic thermal coatings. In experimental thermal tests, a thin application of PCC has provided the same thermal protection as a much thicker and heavier application of a traditional ablative thermal insulation. In addition, tests have shown that the structural integrity of the coating has been maintained and phase change performance after several aero-thermal cycles was not affected. Experimental tests have also shown that, unlike traditional ablative thermal insulations, PCC would not require an environmental seal coat, which has historically been required to prevent moisture absorption by the thermal insulation, prevent environmental degradation, and to improve the optical and aerodynamic properties. In order to reduce

Magnetic Thermal Ablation Using Ferrofluids: Influence of Administration Mode on Biological Effect in Different Porcine Tissues

International Nuclear Information System (INIS)

Bruners, Philipp; Hodenius, Michael; Baumann, Martin; Oversohl, Jessica; Guenther, Rolf W.; Schmitz-Rode, Thomas; Mahnken, Andreas H.

2008-01-01

The purpose of this study was to compare the effects of magnetic thermal ablation in different porcine tissues using either a singular injection or a continuous infusion of superparamagnetic iron oxide nanoparticles. In the first setting samples of three ferrofluids containing different amounts of iron (1:171, 2:192, and 3:214 mg/ml) were singularly interstitially injected into specimens of porcine liver, kidney, and muscle (n = 5). Then the specimens were exposed to an alternating magnetic field (2.86 kA/m, 190 kHz) generated by a circular coil for 5 min. In the second experimental setup ferrofluid samples were continuously interstitially infused into the tissue specimens during the exposure to the magnetic field. To measure the temperature increase two fiber-optic temperature probes with a fixed distance of 0.5 cm were inserted into the specimens along the puncture tract of the injection needle and the temperature was measured every 15 s. Finally, the specimens were dissected, the diameters of the created thermal lesions were measured, and the volumes were calculated and compared. Compared to continuous infusion, a single injection of ferrofluids resulted in smaller coagulation volumes in all tissues. Significant differences regarding coagulation volume were found in kidney and muscle specimens. The continuous infusion technique led to more elliptically shaped coagulation volumes due to larger diameters along the puncture tract. Our data show the feasibility of magnetic thermal ablation using either a single interstitial injection or continuous infusion for therapy of lesions in muscle, kidney, and liver. Continuous infusion of ferrofluids results in larger zones of necrosis compared to a single injection technique.

A study of photothermal laser ablation of various polymers on microsecond time scales.

Science.gov (United States)

Kappes, Ralf S; Schönfeld, Friedhelm; Li, Chen; Golriz, Ali A; Nagel, Matthias; Lippert, Thomas; Butt, Hans-Jürgen; Gutmann, Jochen S

2014-01-01

To analyze the photothermal ablation of polymers, we designed a temperature measurement setup based on spectral pyrometry. The setup allows to acquire 2D temperature distributions with 1 μm size and 1 μs time resolution and therefore the determination of the center temperature of a laser heating process. Finite element simulations were used to verify and understand the heat conversion and heat flow in the process. With this setup, the photothermal ablation of polystyrene, poly(α-methylstyrene), a polyimide and a triazene polymer was investigated. The thermal stability, the glass transition temperature Tg and the viscosity above Tg were governing the ablation process. Thermal decomposition for the applied laser pulse of about 10 μs started at temperatures similar to the start of decomposition in thermogravimetry. Furthermore, for polystyrene and poly(α-methylstyrene), both with a Tg in the range between room and decomposition temperature, ablation already occurred at temperatures well below the decomposition temperature, only at 30-40 K above Tg. The mechanism was photomechanical, i.e. a stress due to the thermal expansion of the polymer was responsible for ablation. Low molecular weight polymers showed differences in photomechanical ablation, corresponding to their lower Tg and lower viscosity above the glass transition. However, the difference in ablated volume was only significant at higher temperatures in the temperature regime for thermal decomposition at quasi-equilibrium time scales.

Percutaneous radiofrequency thermal ablation of lung VX2 tumors in a rabbit model: evaluation with helical CT findings for the complete and partal ablation

Energy Technology Data Exchange (ETDEWEB)

Jin, Gong Yong; Han, Young Min; Lim, Yeong Su; Jang, Kyu Yun; Lee, Sang Yong; Chung, Gyung Ho [School of Medicine, Chonbuk National Univ., Chonju (Korea, Republic of)

2004-05-01

To evaluate the radiologic findings for complete and partial ablation after percutaneous CT-guided transthoracic radiofrequency ablation (RFA) of lung VX2 tumor implanted in rabbits. Thirteen rabbits with successfully implanted lung VX2 were used. Three rabbits as controls did not receive RFA while the other ten rabbits underwent RFA; 5 complete and 5 partial. RFA was performed using an internally cooled, 17-gauge electrode (Radionics, Burlington, MA) with a 1-cm active tip under CT guidance. Postprocedural CT was performed within 3 days, and we analyzed the ablated size, enhancement pattern, shape, margin, and complications of the complete and partial ablation groups. Rabbits were sacrificed after postprocedural CT with an overdose of ketamine, and pathologic findings of the ablated groups were compared with those of the control group. The size of the ablated lesions and the enhancement pattern differed between the completely and partially ablated groups on chest CT. The size of the ablated lesions was increased by 47.1% in the completely ablated group and by 2.1% in the partially ablated group. In the completely ablated group, VX2 tumor showed absolutely no enhancement, whereas only ablated pulmonary parenchyma outside VX2 showed mild enhancement on enhanced CT. In the partial ablated group, a part of VX2 became strongly enhanced on enhanced CT. On microscopic examination, the completely ablated group demonstrated that a viable tumor cell was not visible. In the partially ablated group, however, a viable tumor cell within the surrounding fibrous capsule on the peripheral area of the VX2 was observed. The important CT findings for evaluation of complete and partial RFA are the ablated size and enhancement pattern of the ablated lesion.

Electroporation ablation: A new energy modality for ablation of arrhythmogenic cardiac substrate

NARCIS (Netherlands)

van Driel, VJHM

2016-01-01

At the very end of the Direct Current (DC) era, low-energy DC ablation was demonstrated to cause myocardial lesions by non-thermal irreversible electroporation (IRE) (permanent formation of pores in the cell membrane, leading to cell death), without arcing and/or barotrauma. To eliminate rather

Models of electron conductivity which lead to ablation stabilization of fluid instabilities in laser-driven implosions

International Nuclear Information System (INIS)

Lindl, J.D.; Mead, W.C.

1975-01-01

LASNEX calculations with a modified electron conductivity show the existence of a firepolishing stabilization effect. By modifying the thermal conductivity so that K α T/sup n//rho/sup m/, one is able to construct a situation in which the electrons deposit their energy in a thin layer at the ablation surface and closely match the zero order solutions assumed earlier. The firepolishing effect appears to require that a significant fraction of the total pressure be due to the ablation process itself rather than the thermal pressure in the corona gas. It also requires KL approximately 1 where L is the scale height for decay of thermal perturbations generated at the ablation surface. For classical electron conductivity, because the thermal flux depends linearly on the grams/cm 2 necessary to stop the electrons, (1/rho) nabla rho approximately (1/T) nabla T near the ablation surface so that the pressure is nearly constant across the ablation surface. Hence there is no ablation pressure as such and no firepolishing effect for electron-driven implosions

Energy from solar balloons

Energy Technology Data Exchange (ETDEWEB)

Grena, Roberto [C. R. Casaccia, via Anguillarese 301, 00123 Roma (Italy)

2010-04-15

Solar balloons are hot air balloons in which the air is heated directly by the sun, by means of a black absorber. The lift force of a tethered solar balloon can be used to produce energy by activating a generator during the ascending motion of the balloon. The hot air is then discharged when the balloon reaches a predefined maximum height. A preliminary study is presented, along with an efficiency estimation and some considerations on possible realistic configurations. (author)

Phrenic nerve paralysis during cryoballoon ablation for atrial fibrillation: a comparison between the first- and second-generation balloon

NARCIS (Netherlands)

Casado-Arroyo, R.; Chierchia, G.B.; Conte, G.; Levinstein, M.; Sieira, J.; Rodriguez-Manero, M.; Giovanni, G.; Baltogiannis, Y.; Wauters, K.; Asmundis, C. de; Sarkozy, A.; Brugada, P.

2013-01-01

BACKGROUND: Phrenic nerve palsy (PNP) is the most frequently observed complication during cryoballoon ablation (CB; Arctic Front, Medtronic, MN) occurring in roughly 7%-9% of the cases. The new second-generation cryoballoon ablation Arctic Front Advance (CB-A) (Arctic Front) has recently been

Effect of Non-Equilibrium Surface Thermochemistry in Simulation of Carbon Based Ablators

Science.gov (United States)

Chen, Yih-Kanq; Gokcen, Tahir

2012-01-01

This study demonstrates that coupling of a material thermal response code and a flow solver using non-equilibrium gas/surface interaction model provides time-accurate solutions for the multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and AblatioN Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas mass conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between the material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of nonequilibrium gas/surface interaction chemistry between air and the carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

Blood pressure normalization post-jugular venous balloon angioplasty.

Science.gov (United States)

Sternberg, Zohara; Grewal, Prabhjot; Cen, Steven; DeBarge-Igoe, Frances; Yu, Jinhee; Arata, Michael

2015-05-01

This study is the first in a series investigating the relationship between autonomic nervous system dysfunction and chronic cerebrospinal venous insufficiency in multiple sclerosis patients. We screened patients for the combined presence of the narrowing of the internal jugular veins and symptoms of autonomic nervous system dysfunction (fatigue, cognitive dysfunction, sleeping disorders, headache, thermal intolerance, bowel/bladder dysfunction) and determined systolic and diastolic blood pressure responses to balloon angioplasty. The criteria for eligibility for balloon angioplasty intervention included ≥ 50% narrowing in one or both internal jugular veins, as determined by the magnetic resonance venography, and ≥ 3 clinical symptoms of autonomic nervous system dysfunction. Blood pressure was measured at baseline and post-balloon angioplasty. Among patients who were screened, 91% were identified as having internal jugular veins narrowing (with obstructing lesions) combined with the presence of three or more symptoms of autonomic nervous system dysfunction. Balloon angioplasty reduced the average systolic and diastolic blood pressure. However, blood pressure categorization showed a biphasic response to balloon angioplasty. The procedure increased blood pressure in multiple sclerosis patients who presented with baseline blood pressure within lower limits of normal ranges (systolic ≤ 105 mmHg, diastolic ≤ 70 mmHg) but decreased blood pressure in patients with baseline blood pressure above normal ranges (systolic ≥ 130 mmHg, diastolic ≥ 80 mmHg). In addition, gender differences in baseline blood pressure subcategories were observed. The coexistence of internal jugular veins narrowing and symptoms of autonomic nervous system dysfunction suggests that the two phenomena may be related. Balloon angioplasty corrects blood pressure deviation in multiple sclerosis patients undergoing internal jugular vein dilation. Further studies should investigate the

Pre-test prediction and post-test analysis of PWR fuel rod ballooning in the MT-3 in-pile LOCA simulation experiment in the NRU reactor

International Nuclear Information System (INIS)

Donaldson, A.T.; Horwood, R.A.; Healey, T.

1983-01-01

The USNRC and the UKAEA have jointly funded a series of in-pile LOCA simulation experiments in the Canadian NRU reactor in order to secure further information on the thermal hydraulic and clad deformation response of PWR fuel rod bundles. Test MT-3 in the series was performed using reflood rate and rod internal pressure conditions specified by the UK nuclear industry. The parameters were selected to ensure the development of a near-isothermal clad temperature history during which zircaloy was required to balloon and rupture near the alpha-alpha/beta phase transition. Specification of the reflood rate conditions was assisted by the performance of a precursor test on an unpressurised rod bundle and by complementary application of appropriate thermal hydraulic analyses. Identification of the rod internal pressure needed to cause ballooning and rupture was achieved using a creep deformation model, BALLOON, in conjunction with the clad thermal history defined by the prior thermal hydraulic test. This paper presents the basis of the BALLOON analysis and describes its application in calculating the fill gas pressure for rods MT-3, their axial ballooning profile and the clad temperature at peak radial strain elevations. (author)

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

Science.gov (United States)

Nguyen, Daniel; Chang, Kwang; Hedayatollahnajafi, Saba; Staninec, Michal; Chan, Kenneth; Lee, Robert; Fried, Daniel

2011-07-01

CO2 lasers can be operated at high laser pulse repetition rates for the rapid and precise removal of dental decay. Excessive heat accumulation and peripheral thermal damage is a concern when using high pulse repetition rates. Peripheral thermal damage can adversely impact the mechanical strength of the irradiated tissue, particularly for dentin, and reduce the adhesion characteristics of the modified surfaces. The interpulpal temperature rise was recorded using microthermocouples situated at the roof of the pulp chamber on teeth that were occlusally ablated using a rapidly-scanned CO2 laser operating at 9.3 μm with a pulse duration of 10 to 15 μs and repetition rate of 300 Hz over a 2 min time course. The adhesion strength of laser treated enamel and dentin surfaces was measured for various laser scanning parameters with and without post-ablation acid etching using the single-plane shear test. The mechanical strength of laser-ablated dentin surfaces were determined via the four-point bend test and compared to control samples prepared with 320 grit wet sand paper to simulate conventional preparations. Thermocouple measurements indicated that the temperature remained below ambient temperature if water-cooling was used. There was no discoloration of either dentin or enamel laser treated surfaces, the surfaces were uniformly ablated, and there were no cracks visible. Four-point bend tests yielded mean mechanical strengths of 18.2 N (s.d. = 4.6) for ablated dentin and 18.1 N (s.d. = 2.7) for control (p > 0.05). Shear tests yielded mean bond strengths approaching 30 MPa for both enamel and dentin under certain irradiation conditions. These values were slightly lower than nonirradiated acid-etched control samples. Additional studies are needed to determine if the slightly lower bond strength than the acid-etched control samples is clinically significant. These measurements demonstrate that enamel and dentin surfaces can be rapidly ablated by CO2 lasers with minimal

Modelling of pulsed electron beam induced graphite ablation: Sublimation versus melting

Science.gov (United States)

Ali, Muddassir; Henda, Redhouane

2017-12-01

Pulsed electron beam ablation (PEBA) has recently emerged as a very promising technique for the deposition of thin films with superior properties. Interaction of the pulsed electron beam with the target material is a complex process, which consists of heating, phase transition, and erosion of a small portion from the target surface. Ablation can be significantly affected by the nature of thermal phenomena taking place at the target surface, with subsequent bearing on the properties, stoichiometry and structure of deposited thin films. A two stage, one-dimensional heat conduction model is presented to describe two different thermal phenomena accounting for interaction of a graphite target with a polyenergetic electron beam. In the first instance, the thermal phenomena are comprised of heating, melting and vaporization of the target surface, while in the second instance the thermal phenomena are described in terms of heating and sublimation of the graphite surface. In this work, the electron beam delivers intense electron pulses of ∼100 ns with energies up to 16 keV and an electric current of ∼400 A to a graphite target. The temperature distribution, surface recession velocity, ablated mass per unit area, and ablation depth for the graphite target are numerically simulated by the finite element method for each case. Based on calculation findings and available experimental data, ablation appears to occur mainly in the regime of melting and vaporization from the surface.

Numerical simulation of anisotropic preheating ablative Rayleigh-Taylor instability

International Nuclear Information System (INIS)

Wang Lifeng; Ye Wenhua; Li Yingjun

2010-01-01

The linear growth rate of the anisotropic preheating ablative Rayleigh-Taylor instability (ARTI) is studied by numerical simulations. The preheating model κ(T)=κ SH [1+f(T)] is applied, where f(T) is the preheating function interpreting the preheating tongue effect in the cold plasma ahead of the ablative front. An arbitrary coefficient D is introduced in the energy equation to study the influence of transverse thermal conductivity on the growth of the ARTI. We find that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. Numerical simulations exhibit a significant stabilization of the ablation front by improving the transverse thermal conduction. Our results are in general agreement with the theory analysis and numerical simulations by Masse. (authors)

Effect of ballooning modes on thermal transport and magnetic field diffusion in the solar corona

International Nuclear Information System (INIS)

Strauss, H.R.

1989-01-01

Presently favored mechanisms of coronal heating: current sheet dissipation and Alfven wave resonant heating: deposit heat in thin layers. Classical thermal conduction cannot explain how heat is transported across the magnetic field. If heating occurs in thin layers, large pressure gradients can be created, which can give rise to ballooning modes. These instabilities are caused by the pressure gradient and the curvature of the magnetic field, and are stabilized by magnetic tension. The modes are broad band in wavelength and should produce turbulence. A mixing length expression for the turbulent heat transport shows that it is more than adequate to rapidly convect heat into much broader layers. Furthermore, the turbulent resistivity implies that heating occurs over most of the width of these broadened layers. The broadening also implies that much shorter time scales are required for heating. The β values in the corona suggest that 1--10 turbulent layers are formed in typical loop or arch structures. copyright American Geophysical Union 1989

Optical feedback-induced light modulation for fiber-based laser ablation.

Science.gov (United States)

Kang, Hyun Wook

2014-11-01

Optical fibers have been used as a minimally invasive tool in various medical fields. However, due to excessive heat accumulation, the distal end of a fiber often suffers from severe melting or devitrification, leading to the eventual fiber failure during laser treatment. In order to minimize thermal damage at the fiber tip, an optical feedback sensor was developed and tested ex vivo. Porcine kidney tissue was used to evaluate the feasibility of optical feedback in terms of signal activation, ablation performance, and light transmission. Testing various signal thresholds demonstrated that 3 V was relatively appropriate to trigger the feedback sensor and to prevent the fiber deterioration during kidney tissue ablation. Based upon the development of temporal signal signatures, full contact mode rapidly activated the optical feedback sensor possibly due to heat accumulation. Modulated light delivery induced by optical feedback diminished ablation efficiency by 30% in comparison with no feedback case. However, long-term transmission results validated that laser ablation assisted with optical feedback was able to almost consistently sustain light delivery to the tissue as well as ablation efficiency. Therefore, an optical feedback sensor can be a feasible tool to protect optical fiber tips by minimizing debris contamination and delaying thermal damage process and to ensure more efficient and safer laser-induced tissue ablation.

Clefting in pumpkin balloons

Science.gov (United States)

Baginski, F.; Schur, W.

NASA's effort to develop a large payload, high altitude, long duration balloon, the Ultra Long Duration Balloon, focuses on a pumpkin shape super-pressure design. It has been observed that a pumpkin balloon may be unable to pressurize into the desired cyclically symmetric equilibrium configuration, settling into a distorted, undesired stable state instead. Hoop stress considerations in the pumpkin design leads to choosing the lowest possible bulge radius, while robust deployment is favored by a large bulge radius. Some qualitative understanding of design aspects on undesired equilibria in pumpkin balloons has been obtained via small-scale balloon testing. Poorly deploying balloons have clefts, but most gores away from the cleft deploy uniformly. In this paper, we present models for pumpkin balloons with clefts. Long term success of the pumpkin balloon for NASA requires a thorough understanding of the phenomenon of multiple stable equilibria and means for quantitative assessment of measures that prevent their occurrence. This paper attempts to determine numerical thresholds of design parameters that distinguish between properly deploying designs and improperly deploying designs by analytically investigating designs in the vicinity of criticality. Design elements which may trigger the onset undesired equilibria and remedial measures that ensure deployment are discussed.

Femtosecond laser ablation of bovine cortical bone

Science.gov (United States)

Cangueiro, Liliana T.; Vilar, Rui; Botelho do Rego, Ana M.; Muralha, Vania S. F.

2012-12-01

We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

Performance of Conformable Phenolic Impregnated Carbon Ablator in Aerothermal Environments

Science.gov (United States)

Thornton, Jeremy; Fan, Wendy; Stackpoole, Mairead; Kao, David; Skokova, Kristina; Chavez-Garcia, Jose

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 PICA's 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.

Pulsed Tm:YAG laser ablation of knee joint tissues

Science.gov (United States)

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.

Theoretical prediction of thermal conductivity for thermal protection systems

International Nuclear Information System (INIS)

Gori, F.; Corasaniti, S.; Worek, W.M.; Minkowycz, W.J.

2012-01-01

The present work is aimed to evaluate the effective thermal conductivity of an ablative composite material in the state of virgin material and in three paths of degradation. The composite material is undergoing ablation with formation of void pores or char and void pores. The one dimensional effective thermal conductivity is evaluated theoretically by the solution of heat conduction under two assumptions, i.e. parallel isotherms and parallel heat fluxes. The paper presents the theoretical model applied to an elementary cubic cell of the composite material which is made of two crossed fibres and a matrix. A numerical simulation is carried out to compare the numerical results with the theoretical ones for different values of the filler volume fraction. - Highlights: ► Theoretical models of the thermal conductivity of an ablative composite. ► Composite material is made of two crossed fibres and a matrix. ► Three mechanisms of degradation are investigated. ► One dimensional thermal conductivity is evaluated by the heat conduction equation. ► Numerical simulations to be compared with the theoretical models.

Numerical Simulation of Anisotropic Preheating Ablative Rayleigh–Taylor Instability

International Nuclear Information System (INIS)

Li-Feng, Wang; Wen-Hua, Ye; Ying-Jun, Li

2010-01-01

The linear growth rate of the anisotropic preheating ablative Rayleigh–Taylor instability (ARTI) is studied by numerical simulations. The preheating model κ(T) = κ SH [1 + f(T)] is applied, where f(T) is the preheating function interpreting the preheating tongue effect in the cold plasma ahead of the ablative front. An arbitrary coefficient D is introduced in the energy equation to study the influence of transverse thermal conductivity on the growth of the ARTI. We find that enhancing diffusion in a plane transverse to the mean longitudinal flow can strongly reduce the growth of the instability. Numerical simulations exhibit a significant stabilization of the ablation front by improving the transverse thermal conduction. Our results are in general agreement with the theory analysis and numerical simulations by Masse [Phys. Rev. Lett. 98 (2007) 245001]. (physics of gases, plasmas, and electric discharges)

Power Laser Ablation Symposia

CERN Document Server

Phipps, Claude

2007-01-01

Laser ablation describes the interaction of intense optical fields with matter, in which atoms are selectively driven off by thermal or nonthermal mechanisms. The field of laser ablation physics is advancing so rapidly that its principal results are seen only in specialized journals and conferences. This is the first book that combines the most recent results in this rapidly advancing field with authoritative treatment of laser ablation and its applications, including the physics of high-power laser-matter interaction. Many practical applications exist, ranging from inertial confinement fusion to propulsion of aerostats for pollution monitoring to laser ignition of hypersonic engines to laser cleaning nanoscale contaminants in high-volume computer hard drive manufacture to direct observation of the electronic or dissociative states in atoms and molecules, to studying the properties of materials during 200kbar shocks developed in 200fs. Selecting topics which are representative of such a broad field is difficu...

Balloon sinuplasty

OpenAIRE

Ahmad, Zahoor

2010-01-01

Balloon sinuplasty is a technique in endoscopic sinus surgery that involves minimally invasive procedures to dilate the obstructed or stenosed anatomical sinus pathways. Procedure is derived from the well-recognized techinique of angioplasty. This article highlights the procedural methods with review of literature and my personal experience in balloon sinupalsty.

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

Science.gov (United States)

Howe, John T.; Yang, Lily

1991-01-01

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

Percutaneous treatment of bone tumors by radiofrequency thermal ablation

International Nuclear Information System (INIS)

Ruiz Santiago, Fernando; Mar Castellano Garcia, Maria del; Guzman Alvarez, Luis; Martinez Montes, Jose Luis; Ruiz Garcia, Manuel; Tristan Fernandez, Juan MIguel

2011-01-01

We present our experience of the treatment of bone tumors with radiofrequency thermal ablation (RFTA). Over the past 4 years, we have treated 26 cases (22 benign and 4 malignant) using CT-guided RFTA. RFTA was the sole treatment in 19 cases and was combined with percutaneous cementation during the same session in the remaining seven cases. Our approach to the tumors was simplified, using a single point of entrance for both RFTA and percutaneous osteoplasty. In the benign cases, clinical success was defined as resolution of pain within 1 month of the procedure and no recurrence during the follow-up period. It was achieved in 19 out of the 21 patients in which curative treatment was attempted. The two non-resolved cases were a patient with osteoid osteoma who developed a symptomatic bone infarct after a symptom-free period of 2 months and another with femoral diaphysis osteoblastoma who suffered a pathological fracture after 8 months without symptoms. The procedure was considered clinically successful in the five cases (4 malign and 1 benign) in which palliative treatment was attempted, because there was a mean (±SD) reduction in visual analogue scale (VAS) pain score from 9.0 ± 0.4 before the procedure to <4 during the follow-up period.

Percutaneous treatment of bone tumors by radiofrequency thermal ablation

Energy Technology Data Exchange (ETDEWEB)

Ruiz Santiago, Fernando, E-mail: ferusan@ono.com [Department of Radiology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18013 Granada (Spain); Mar Castellano Garcia, Maria del; Guzman Alvarez, Luis [Department of Radiology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18013 Granada (Spain); Martinez Montes, Jose Luis [Department of Traumatology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18013 Granada (Spain); Ruiz Garcia, Manuel; Tristan Fernandez, Juan MIguel [Department of Radiology, Hospital of Traumatology (Ciudad Sanitaria Virgen de las Nieves), Carretera de Jaen SN, 18013 Granada (Spain)

2011-01-15

We present our experience of the treatment of bone tumors with radiofrequency thermal ablation (RFTA). Over the past 4 years, we have treated 26 cases (22 benign and 4 malignant) using CT-guided RFTA. RFTA was the sole treatment in 19 cases and was combined with percutaneous cementation during the same session in the remaining seven cases. Our approach to the tumors was simplified, using a single point of entrance for both RFTA and percutaneous osteoplasty. In the benign cases, clinical success was defined as resolution of pain within 1 month of the procedure and no recurrence during the follow-up period. It was achieved in 19 out of the 21 patients in which curative treatment was attempted. The two non-resolved cases were a patient with osteoid osteoma who developed a symptomatic bone infarct after a symptom-free period of 2 months and another with femoral diaphysis osteoblastoma who suffered a pathological fracture after 8 months without symptoms. The procedure was considered clinically successful in the five cases (4 malign and 1 benign) in which palliative treatment was attempted, because there was a mean ({+-}SD) reduction in visual analogue scale (VAS) pain score from 9.0 {+-} 0.4 before the procedure to <4 during the follow-up period.

Image-guided radiofrequency ablation of renal cell carcinoma

International Nuclear Information System (INIS)

Boss, Andreas; Clasen, Stephan; Pereira, Philippe L.; Kuczyk, Markus; Schick, Fritz

2007-01-01

The incidence of renal cell carcinoma is rising with the increased number of incidental detection of small tumours. During the past few years, percutaneous imaging-guided radiofrequency ablation has evolved as a minimally invasive treatment of small unresectable renal tumours offering reduced patient morbidity and overall health care costs. In radiofrequency ablation, thermal energy is deposited into a targeted tumour by means of a radiofrequency applicator. In recent studies, radiofrequency ablation was shown to be an effective and safe modality for local destruction of renal cell carcinoma. Radiofrequency applicator navigation can be performed via ultrasound, computed tomography or magnetic resonance guidance; however, ultrasound seems less favourable because of the absence of monitoring capabilities during ablation. On-line monitoring of treatment outcome can only be performed with magnetic resonance imaging giving the possibility of eventual applicator repositioning to ablate visible residual tumour tissue. Long-term follow-up is crucial to assess completeness of tumour ablation. New developments in ablation technology and radiological equipment will further increase the indication field for radiofrequency ablation of renal cell carcinoma. Altogether, radiofrequency ablation seems to be a promising new modality for the minimally invasive treatment of renal cell carcinoma, which was demonstrated to exhibit high short-term effectiveness. (orig.)

Decomposition of dioxin analogues and ablation study for carbon nanotube

International Nuclear Information System (INIS)

Yamauchi, Toshihiko

2002-01-01

Two application studies associated with the free electron laser are presented separately, which are the titles of 'Decomposition of Dioxin Analogues' and 'Ablation Study for Carbon Nanotube'. The decomposition of dioxin analogues by infrared (IR) laser irradiation includes the thermal destruction and multiple-photon dissociation. It is important for us to choose the highly absorbable laser wavelength for the decomposition. The thermal decomposition takes place by the irradiation of the low IR laser power. Considering the model of thermal decomposition, it is proposed that adjacent water molecules assist the decomposition of dioxin analogues in addition to the thermal decomposition by the direct laser absorption. The laser ablation study is performed for the aim of a carbon nanotube synthesis. The vapor by the ablation is weakly ionized in the power of several-hundred megawatts. The plasma internal energy is kept over an 8.5 times longer than the vacuum. The cluster was produced from the weakly ionized gas in the enclosed gas, which is composed of the rough particles in the low power laser more than the high power which is composed of the fine particles. (J.P.N.)

Real-time near IR (1310 nm) imaging of CO2 laser ablation of enamel.

Science.gov (United States)

Darling, Cynthia L; Fried, Daniel

2008-02-18

The high-transparency of dental enamel in the near-IR (NIR) can be exploited for real-time imaging of ablation crater formation during drilling with lasers. NIR images were acquired with an InGaAs focal plane array and a NIR zoom microscope during drilling incisions in human enamel samples with a lambda=9.3-microm CO(2) laser operating at repetition rates of 50-300-Hz with and without a water spray. Crack formation, dehydration and thermal changes were observed during ablation. These initial images demonstrate the potential of NIR imaging to monitor laser-ablation events in real-time to provide information about the mechanism of ablation and to evaluate the potential for peripheral thermal and mechanical damage.

Hard tissue ablation with a spray-assisted mid-IR laser

International Nuclear Information System (INIS)

Kang, H W; Rizoiu, I; Welch, A J

2007-01-01

The objective of this study was to understand the dominant mechanism(s) for dental enamel ablation with the application of water spray. A free-running Er,Cr:YSGG (yttrium, scandium, gallium, garnet) laser was used to ablate human enamel tissue at various radiant exposures. During dental ablation, distilled water was sprayed on the sample surface, and these results were compared to ablation without a spray (dry ablation). In order to identify dominant ablation mechanisms, transient acoustic waves were compared to ablation thresholds and the volume of material removed. The ablation profile and depth were measured using optical coherence tomography (OCT). Irregular surface modification, charring and peripheral cracks were associated with dry ablation, whereas craters for spray samples were relatively clean without thermal damage. In spite of a 60% higher ablation threshold for spray associated irradiations owing to water absorption, acoustic peak pressures were six times higher and ablation volume was up to a factor of 2 larger compared to dry ablation. The enhanced pressure and ablation performance of the spray-assisted process was the result of rapid water vaporization, material ejection with recoil stress, interstitial water explosion and possibly liquid-jet formation. With water cooling and abrasive/disruptive mechanical effects, the spray ablation can be a safe and efficient modality for dental treatment

Hard tissue ablation with a spray-assisted mid-IR laser

Science.gov (United States)

Kang, H. W.; Rizoiu, I.; Welch, A. J.

2007-12-01

The objective of this study was to understand the dominant mechanism(s) for dental enamel ablation with the application of water spray. A free-running Er,Cr:YSGG (yttrium, scandium, gallium, garnet) laser was used to ablate human enamel tissue at various radiant exposures. During dental ablation, distilled water was sprayed on the sample surface, and these results were compared to ablation without a spray (dry ablation). In order to identify dominant ablation mechanisms, transient acoustic waves were compared to ablation thresholds and the volume of material removed. The ablation profile and depth were measured using optical coherence tomography (OCT). Irregular surface modification, charring and peripheral cracks were associated with dry ablation, whereas craters for spray samples were relatively clean without thermal damage. In spite of a 60% higher ablation threshold for spray associated irradiations owing to water absorption, acoustic peak pressures were six times higher and ablation volume was up to a factor of 2 larger compared to dry ablation. The enhanced pressure and ablation performance of the spray-assisted process was the result of rapid water vaporization, material ejection with recoil stress, interstitial water explosion and possibly liquid-jet formation. With water cooling and abrasive/disruptive mechanical effects, the spray ablation can be a safe and efficient modality for dental treatment.

Status of the NASA Balloon Program

Science.gov (United States)

Needleman, H. C.; Nock, R. S.; Bawcom, D. W.

1993-02-01

In the early 1980's the U.S. National Aeronautics and Space Administration (NASA) Balloon Program was faced with a problem of catastrophic balloon failures. In 1986 a balloon recovery program was initiated. This program included qualification of new balloon films, and investigations into materials, processing, structures and performance of balloons. This recovery program has been very successful. To date, more than 100 balloons manufactured of newly developed films have been flown with unprecedented success. There has been much progress made across the spectrum of balloon related disciplines. A new design philosophy has been developed and is being used for all NASA balloons. An updated balloon reliability and quality assurance program is in effect. The long duration balloon development project has been initiated with the first flight test having been conducted in December 1989 from Antarctica. A comprehensive research and development (R&D) effort has been initiated and is progressing well. The progress, status and future plans for these and other aspects of the NASA program, along with a description of the comprehensive balloon R&D activity, will be presented.

Investigation of hot air balloon fatalities.

Science.gov (United States)

McConnell, T S; Smialek, J E; Capron, R G

1985-04-01

The rising popularity of the sport of hot air ballooning has been accompanied by several recent incidents, both in this country and other parts of the world, where mechanical defects and the improper operation of balloons have resulted in several fatalities. A study was conducted to identify the location and frequency of hot air ballooning accidents. Furthermore, the study attempted to identify those accidents that were the result of improper handling on the part of the balloon operators and those that were related to specific defects in the construction of the balloon. This paper presents a background of the sport of hot air ballooning, together with an analysis of the construction of a typical hot air balloon, pointing out the specific areas where defects may occur that could result in a potential fatal balloon crash. Specific attention is given to the two recent balloon crashes that occurred in Albuquerque, N.M., hot air balloon capital of the world, and that resulted in multiple fatalities.

Cleft formation in pumpkin balloons

Science.gov (United States)

Baginski, Frank E.; Brakke, Kenneth A.; Schur, Willi W.

NASA’s development of a large payload, high altitude, long duration balloon, the Ultra Long Duration Balloon, centers on a pumpkin shape super-pressure design. Under certain circumstances, it has been observed that a pumpkin balloon may be unable to pressurize into the desired cyclically symmetric equilibrium configuration, settling into a distorted, undesired state instead. Success of the pumpkin balloon for NASA requires a thorough understanding of the phenomenon of multiple stable equilibria and developing of means for the quantitative assessment of design measures that prevent the occurrence of undesired equilibrium. In this paper, we will use the concept of stability to classify cyclically symmetric equilibrium states at full inflation and pressurization. Our mathematical model for a strained equilibrium balloon, when applied to a shape that mimics the Phase IV-A balloon of Flight 517, predicts instability at float. Launched in Spring 2003, this pumpkin balloon failed to deploy properly. Observations on pumpkin shape type super-pressure balloons that date back to the 1980s suggest that within a narrowly defined design class of pumpkin shape super-pressure balloons where individual designs are fully described by the number of gores ng and by a single measure of the bulging gore shape, the designs tend to become more vulnerable with the growing number of gores and with the diminishing size of the bulge radius rB Weight efficiency considerations favor a small bulge radius, while robust deployment into the desired cyclically symmetrical configuration becomes more likely with an increased bulge radius. In an effort to quantify this dependency, we will explore the stability of a family of balloon shapes parametrized by (ng, rB) which includes a design that is very similar, but not identical, to the balloon of Flight 517. In addition, we carry out a number of simulations that demonstrate other aspects related to multiple equilibria of pumpkin balloons.

Reassembling Solid Materials by Femtosecond Laser Ablation: Case of Aluminum Nitride

Science.gov (United States)

Kobayashi, Tohru; Matsuo, Yukari

2013-06-01

Through atomization and ionization, we could completely alter the composition of a nonconductive material, aluminum nitride, by femtosecond laser ablation. Preferential production of pure aluminum cluster cations Aln+ (n≤32) reflects not only their higher energetic stability compared with mixed clusters AlnNm+ but also completion of thermal relaxation in ablation plasma. Observation of metastable dissociation of Aln+ indicates that cluster cations have still enough internal energy for dissociation to occur, although the process is much slower than the cluster formation. Almost no cluster formation has been observed after nanosecond laser ablation of aluminum nitride, which highlights the distinct nature of ablation plasma produced by femtosecond laser ablation.

Weather Balloon Ascent Rate

Science.gov (United States)

Denny, Mark

2016-05-01

The physics of a weather balloon is analyzed. The surprising aspect of the motion of these balloons is that they ascend to great altitudes (typically 35 km) at a more or less constant rate. Such behavior is not surprising near the ground—say for a helium-filled party balloon rising from street level to the top of the Empire State building—but it is unexpected for a balloon that rises to altitudes where the air is rarefied. We show from elementary physical laws why the ascent rate is approximately constant.

Using FT-IR Spectroscopy to Elucidate the Structures of Ablative Polymers

Science.gov (United States)

Fan, Wendy

2011-01-01

The composition and structure of an ablative polymer has a multifaceted influence on its thermal, mechanical and ablative properties. Understanding the molecular level information is critical to the optimization of material performance because it helps to establish correlations with the macroscopic properties of the material, the so-called structure-property relationship. Moreover, accurate information of molecular structures is also essential to predict the thermal decomposition pathways as well as to identify decomposition species that are fundamentally important to modeling work. In this presentation, I will describe the use of infrared transmission spectroscopy (FT-IR) as a convenient tool to aid the discovery and development of thermal protection system materials.

Preintervention lesion remodelling affects operative mechanisms of balloon optimised directional coronary atherectomy procedures: a volumetric study with three dimensional intravascular ultrasound

Science.gov (United States)

von Birgelen, C; Mintz, G; de Vrey, E A; Serruys, P; Kimura, T; Nobuyoshi, M; Popma, J; Leon, M; Erbel, R; de Feyter, P J

2000-01-01

AIMS—To classify atherosclerotic coronary lesions on the basis of adequate or inadequate compensatory vascular enlargement, and to examine changes in lumen, plaque, and vessel volumes during balloon optimised directional coronary atherectomy procedures in relation to the state of adaptive remodelling before the intervention.
DESIGN—29 lesion segments in 29 patients were examined with intravascular ultrasound before and after successful balloon optimised directional coronary atherectomy procedures, and a validated volumetric intravascular ultrasound analysis was performed off-line to assess the atherosclerotic lesion remodelling and changes in plaque and vessel volumes that occurred during the intervention. Based on the intravascular ultrasound data, lesions were classified according to whether there was inadequate (group I) or adequate (group II) compensatory enlargement.
RESULTS—There was no significant difference in patient and lesion characteristics between groups I and II (n = 10 and 19), including lesion length and details of the intervention. Quantitative coronary angiographic data were similar for both groups. However, plaque and vessel volumes were significantly smaller in group I than in II. In group I, 9 (4)% (mean (SD)) of the plaque volume was ablated, while in group II 16 (11)% was ablated (p = 0.01). This difference was reflected in a lower lumen volume gain in group I than in group II (46 (18) mm3 v 80 (49) mm3 (p atherectomy procedures. Plaque ablation was found to be particularly low in lesions with inadequate compensatory vascular enlargement.


Keywords: intravascular ultrasound; ultrasonics; remodelling; coronary artery disease; atherectomy PMID:10648496

Neutral and plasma shielding model for pellet ablation

International Nuclear Information System (INIS)

Houlberg, W.A.; Milora, S.L.; Attenberger, S.E.

1987-10-01

The neutral gas shielding model for ablation of frozen hydrogenic pellets is extended to include the effects of an initial Maxwelliam distribution of incident electron energies; a cold plasma shield outside the neutral shield and extended along the magnetic field; energetic neutral beam ions and alpha particles; and self-limiting electron ablation in the collisionless plasma limit. Including the full electron distribution increases ablation, but adding the cold ionized shield reduces ablation; the net effect is a modest reduction in pellet penetration compared with the monoenergetic electron neutral shielding model with no plasma shield. Unlike electrons, fast ions can enter the neutral shield directly without passing through the cold ionized shield because their gyro-orbits are typically larger than the diameter of the cold plasma tube. Fast alpha particles should not enhance the ablation rate unless their population exceeds that expected from local classical thermalization. Fast beam ions, however, may enhance ablation in the plasma periphery if their population is high enough. Self-limiting ablation in the collisionless limit leads to a temporary distortion of the original plasma electron Maxwellian distribution function through preferential depopulation of the higher-energy electrons. 23 refs., 9 figs

Non-linear analysis and the design of Pumpkin Balloons: stress, stability and viscoelasticity

Science.gov (United States)

Rand, J. L.; Wakefield, D. S.

Tensys have a long-established background in the shape generation and load analysis of architectural stressed membrane structures Founded upon their inTENS finite element analysis suite these activities have broadened to encompass lighter than air structures such as aerostats hybrid air-vehicles and stratospheric balloons Winzen Engineering couple many years of practical balloon design and fabrication experience with both academic and practical knowledge of the characterisation of the non-linear viscoelastic response of the polymeric films typically used for high-altitude scientific balloons Both companies have provided consulting services to the NASA Ultra Long Duration Balloon ULDB Program Early implementations of pumpkin balloons have shown problems of geometric instability characterised by improper deployment and these difficulties have been reproduced numerically using inTENS The solution lies in both the shapes of the membrane lobes and also the need to generate a biaxial stress field in order to mobilise in-plane shear stiffness Balloons undergo significant temperature and pressure variations in flight The different thermal characteristics between tendons and film can lead to significant meridional stress Fabrication tolerances can lead to significant local hoop stress concentrations particularly adjacent to the base and apex end fittings The non-linear viscoelastic response of the envelope film acts positively to help dissipate stress concentrations However creep over time may produce lobe geometry variations that may

Preheating ablation effects on the Rayleigh-Taylor instability in the weakly nonlinear regime

International Nuclear Information System (INIS)

Wang, L. F.; Ye, W. H.; He, X. T.; Sheng, Z. M.; Don, Wai-Sun; Li, Y. J.

2010-01-01

The two-dimensional Rayleigh-Taylor instability (RTI) with and without thermal conduction is investigated by numerical simulation in the weakly nonlinear regime. A preheat model κ(T)=κ SH [1+f(T)] is introduced for the thermal conduction [W. H. Ye, W. Y. Zhang, and X. T. He, Phys. Rev. E 65, 057401 (2002)], where κ SH is the Spitzer-Haerm electron thermal conductivity coefficient and f(T) models the preheating tongue effect in the cold plasma ahead of the ablation front. The preheating ablation effects on the RTI are studied by comparing the RTI with and without thermal conduction with identical density profile relevant to inertial confinement fusion experiments. It is found that the ablation effects strongly influence the mode coupling process, especially with short perturbation wavelength. Overall, the ablation effects stabilize the RTI. First, the linear growth rate is reduced, especially for short perturbation wavelengths and a cutoff wavelength is observed in simulations. Second, the second harmonic generation is reduced for short perturbation wavelengths. Third, the third-order negative feedback to the fundamental mode is strengthened, which plays a stabilization role. Finally, on the contrary, the ablation effects increase the generation of the third harmonic when the perturbation wavelengths are long. Our simulation results indicate that, in the weakly nonlinear regime, the ablation effects are weakened as the perturbation wavelength is increased. Numerical results obtained are in general agreement with the recent weakly nonlinear theories as proposed in [J. Sanz, J. Ramirez, R. Ramis et al., Phys. Rev. Lett. 89, 195002 (2002); J. Garnier, P.-A. Raviart, C. Cherfils-Clerouin et al., Phys. Rev. Lett. 90, 185003 (2003)].

Landau-Darrieus instability in an ablation front

International Nuclear Information System (INIS)

Piriz, A.R.; Portugues, R.F.

2003-01-01

An analytical model that shows the conditions for the existence of the Landau-Darrieus instability of an ablation front is presented. The model seems to agree with recently claimed simulation results [L. Masse et al., Proceedings of the 1st International Conference on Inertial Fusion Sciences and Applications (Elsevier, Paris, 2000), p. 220]. The model shows that the ablation front can be unstable in absence of gravity when the thermal flux is inhibited within the supercritical region of the corona

Standard Test Method for Oxyacetylene Ablation Testing of Thermal Insulation Materials

CERN Document Server

American Society for Testing and Materials. Philadelphia

2008-01-01

1.1 This test method covers the screening of ablative materials to determine the relative thermal insulation effectiveness when tested as a flat panel in an environment of a steady flow of hot gas provided by an oxyacetylene burner. 1.2 This test method should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard of materials, products, or assemblies under actual fire conditions. However, results of this test method may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limi...

Single exponential decay waveform; a synergistic combination of electroporation and electrolysis (E2 for tissue ablation

Directory of Open Access Journals (Sweden)

Nina Klein

2017-04-01

Full Text Available Background Electrolytic ablation and electroporation based ablation are minimally invasive, non-thermal surgical technologies that employ electrical currents and electric fields to ablate undesirable cells in a volume of tissue. In this study, we explore the attributes of a new tissue ablation technology that simultaneously delivers a synergistic combination of electroporation and electrolysis (E2. Method A new device that delivers a controlled dose of electroporation field and electrolysis currents in the form of a single exponential decay waveform (EDW was applied to the pig liver, and the effect of various parameters on the extent of tissue ablation was examined with histology. Results Histological analysis shows that E2 delivered as EDW can produce tissue ablation in volumes of clinical significance, using electrical and temporal parameters which, if used in electroporation or electrolysis separately, cannot ablate the tissue. Discussion The E2 combination has advantages over the three basic technologies of non-thermal ablation: electrolytic ablation, electrochemical ablation (reversible electroporation with injection of drugs and irreversible electroporation. E2 ablates clinically relevant volumes of tissue in a shorter period of time than electrolysis and electroporation, without the need to inject drugs as in reversible electroporation or use paralyzing anesthesia as in irreversible electroporation.

Scientific Ballooning in India - Recent Developments

Science.gov (United States)

Manchanda, R. K.; Srinivasan, S.; Subbarao, J. V.

Established in 1972, the National Balloon Facility operated by TIFR in Hyderabad, India is is a unique facility in the country, which provides a complete solution in scientific ballooning. It is also one of its kind in the world since it combines both, the in-house balloon production and a complete flight support for scientific ballooning. With a large team working through out the year to design, fabricate and launch scientific balloons, the Hyderabad Facility is a unique centre of expertise where the balloon design, Research and Development, the production and launch facilities are located under one roof. Our balloons are manufactured from 100% indigenous components. The mission specific balloon design, high reliability control and support instrumentation, in-house competence in tracking, telemetry, telecommand, data processing, system design and mechanics is a hallmark of the Hyderabad balloon facility. In the past few years we have executed a major programme of upgradation of different components of balloon production, telemetry and telecommand hardware and various support facilities. This paper focuses on our increased capability of balloon production of large sizes up to size of 780,000 M^3 using Antrix film, development of high strength balloon load tapes with the breaking strength of 182 kg, and the recent introduction of S-band telemetry and a commandable timer cut-off unit in the flight hardware. A summary of the various flights conducted in recent years will be presented along with the plans for new facilities.

Effect analysis of material properties of picosecond laser ablation for ABS/PVC

Science.gov (United States)

Tsai, Y. H.; Ho, C. Y.; Chiou, Y. J.

2017-06-01

This paper analytically investigates the picosecond laser ablation of ABS/PVC. Laser-pulsed ablation is a wellestablished tool for polymer. However the ablation mechanism of laser processing for polymer has not been thoroughly understood yet. This study utilized a thermal transport model to analyze the relationship between the ablation rate and laser fluences. This model considered the energy balance at the decomposition interface and Arrhenius law as the ablation mechanisms. The calculated variation of the ablation rate with the logarithm of the laser fluence agrees with the measured data. It is also validated in this work that the variation of the ablation rate with the logarithm of the laser fluence obeys Beer's law for low laser fluences. The effects of material properties and processing parameters on the ablation depth per pulse are also discussed for picosecond laser processing of ABS/PVC.

Femtosecond laser ablation of enamel

Science.gov (United States)

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.

Thermal and Ablative Properties of Ipns and Composites of High Ortho Resole Resin and Difurfurylidene Acetone

Directory of Open Access Journals (Sweden)

Tariq S. NAJIM

2008-12-01

Full Text Available High ortho resole resin was prepared by condensation of phenol with excess of formaldehyde in the presence of magnesium oxide as catalyst. Reaction of furfuraldehyde with acetone in basic medium led to difurfurylidene acetone (DFA. Their interpenetrating polymer network (IPNS were obtained by the reaction of predetermined quantities of difurfurylidene acetone and high ortho resole using p-toluene sulphonic acid (PTSA as curing agent. The thermal behavior of the resins was studied using thermogravimetry (TG under ambient and nitrogen atmospheres over a temperature range of (25-1000 Cº. It was observed that the IPN of 20% DFA – 80% resole has higher thermal stability than that of resole alone and the decomposition temperature was higher by 80 Cº. This behavior was attributed to highly cross linked structure and thermally stable backbone of ploy difurfurylidene acetone due to formation of ladder structure.Impregnation of chopped fiber glass type (E with the polymeric solutions was used to prepare their composites, and the ablative properties were investigated according to ASTM E-285 –80. It was observed that the IPN of (DFA- resol perform better than the resole composite alone.

Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions

Science.gov (United States)

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

2012-01-01

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

Efficacy and safety of Hybrid-APC for the ablation of Barrett's esophagus.

Science.gov (United States)

Manner, Hendrik; May, Andrea; Kouti, Ioanna; Pech, Oliver; Vieth, Michael; Ell, Christian

2016-04-01

After thermal ablation of Barrett's esophagus (BE), stricture formation is reported in 5 to over 10% of patients. The question arises whether submucosal fluid injection prior to ablation may lower the risk of stricture formation. The aim of the present study was to evaluate the efficacy and safety of the new technique of Hybrid-APC which combines submucosal injection with APC. Patients who had a residual BE segment of at least 1 cm after endoscopic resection of early Barrett's neoplasia underwent thermal ablation of BE by Hybrid-APC. Prior to thermal ablation, submucosal injection of sodium chloride 0.9% was carried out using a flexible water-jet probe (Erbejet 2; Erbe Elektromedizin, Tuebingen, Germany). Check-up upper GI endoscopy was carried out 3 months after macroscopically complete ablation including biopsies from the neo-Z-line and the former BE segment, and recording of stricture formation. From May 2011 to November 2012, a total of 60 patients (pt) were included in the study [55 pt male (92%); mean age 62 ± 9 years, range 42-79]. Ten patients were excluded from the study. In the remaining 50 pt, Hybrid-APC ablation and check-up endoscopy at 3 months were carried out. Forty-eight out of 50 pt (96%; ITT: 49/60, 82%) achieved macroscopically complete remission after a median of 3.5 APC sessions [SD 2.4; range 1-10]. Freedom from BE was histopathologically observed in 39/50 patients (78%). There was one treatment-related stricture (2%). Minor adverse events of Hybrid-APC were observed in 11 patients (22%). According to this pilot series, Hybrid-APC was effective and safe for BE ablation in a tertiary referral center. The rate of stricture formation was only 2%. Further studies are required to confirm the present results. DRKS00003369.

Transarterial ethanol ablation for sporadic and non-hemorrhaging angiomyolipoma in the kidney

International Nuclear Information System (INIS)

Takebayashi, Shigeo; Horikawa, Ayumi; Arai, Mito; Iso, Shinichiroh; Noguchi, Kazumi

2009-01-01

Purpose: We evaluated the efficacy and side effects of transarterial ethanol ablation in sporadic and non-hemorrhaging angiomyolipomas (AMLs) in the kidney. Material and Methods: A total of 10 patients with solitary and sporadic AMLs underwent selective transarterial absolute ethanol ablation for prophylaxis against hemorrhage. We confirmed the ratio areas of tumor vessel on angiogram, those of infraction on post-ablation computed tomography (CT) and those of tumor reduction in a 3-, 6- and 12-month follow-up CT. Results: Once or twice a single infusion of 1 or 2 ml absolute ethanol achieved in a total occlusion of 22 feeding arteries which consisted of 7 proximal interlobar arteries, 12 distal interlobar arteries and 3 renal capsular arteries. Nontarget occlusion did not occur by ethanol reflux in any cases but occurred causing spasms provoked by repeated inflation and deflation of the balloon in one case. Total occlusion of tumor vessels was observed in 7 patients and 92-95% occlusion in 3. Ethanol ablation produced 1.8-22.5% (mean 8.4 ± 6.8%) areas of infarctions but the outcome was not serious in all cases. Mean percentage areas of tumor reduction were 29.4 ± 10.6% in a 3-month follow-up, 45.7 ± 11.9% in a 6-month and 59.3 ± 11.5% in a 12-month follow-up. Conclusions: Absolute ethanol ablation for sporadic and non-hemorrhaging AML is safe and effective in reducing majority of tumor area in a 1-year follow-up.

Thermal modelling using discrete vasculature for thermal therapy: a review

Science.gov (United States)

Kok, H.P.; Gellermann, J.; van den Berg, C.A.T.; Stauffer, P.R.; Hand, J.W.; Crezee, J.

2013-01-01

Reliable temperature information during clinical hyperthermia and thermal ablation is essential for adequate treatment control, but conventional temperature measurements do not provide 3D temperature information. Treatment planning is a very useful tool to improve treatment quality and substantial progress has been made over the last decade. Thermal modelling is a very important and challenging aspect of hyperthermia treatment planning. Various thermal models have been developed for this purpose, with varying complexity. Since blood perfusion is such an important factor in thermal redistribution of energy in in vivo tissue, thermal simulations are most accurately performed by modelling discrete vasculature. This review describes the progress in thermal modelling with discrete vasculature for the purpose of hyperthermia treatment planning and thermal ablation. There has been significant progress in thermal modelling with discrete vasculature. Recent developments have made real-time simulations possible, which can provide feedback during treatment for improved therapy. Future clinical application of thermal modelling with discrete vasculature in hyperthermia treatment planning is expected to further improve treatment quality. PMID:23738700

Real-time monitoring of radiofrequency ablation of liver tumors using thermal-dose calculation by MR temperature imaging: initial results in nine patients, including follow-up

International Nuclear Information System (INIS)

Lepetit-Coiffe, Matthieu; Quesson, Bruno; Moonen, Chrit T.W.; Laumonier, Herve; Trillaud, Herve; Seror, Olivier; Sesay, Musa-Bahazid; Grenier, Nicolas

2010-01-01

To assess the practical feasibility and effectiveness of real-time magnetic resonance (MR) temperature monitoring for the radiofrequency (RF) ablation of liver tumours in a clinical setting, nine patients (aged 49-87 years, five men and four women) with one malignant tumour (14-50 mm, eight hepatocellular carcinomas and one colorectal metastasis), were treated by 12-min RF ablation using a 1.5-T closed magnet for real-time temperature monitoring. The clinical monopolar RF device was filtered at 64 MHz to avoid electromagnetic interference. Real-time computation of thermal-dose (TD) maps, based on Sapareto and Dewey's equation, was studied to determine its ability to provide a clear end-point of the RF procedure. Absence of local recurrence on follow-up MR images obtained 45 days after the RF ablation was used to assess the apoptotic and necrotic prediction obtained by real-time TD maps. Seven out of nine tumours were completely ablated according to the real-time TD maps. Compared with 45-day follow-up MR images, TD maps accurately predicted two primary treatment failures, but were not relevant in the later progression of one case of secondary local tumour. The real-time TD concept is a feasible and promising monitoring method for the RF ablation of liver tumours. (orig.)

Real-time monitoring of radiofrequency ablation of liver tumors using thermal-dose calculation by MR temperature imaging: initial results in nine patients, including follow-up

Energy Technology Data Exchange (ETDEWEB)

Lepetit-Coiffe, Matthieu; Quesson, Bruno; Moonen, Chrit T.W. [Universite Victor Segalen Bordeaux 2, Laboratoire Imagerie Moleculaire et Fonctionnelle: de la physiologie a la therapie CNRS UMR 5231, Bordeaux Cedex (France); Laumonier, Herve; Trillaud, Herve [Universite Victor Segalen Bordeaux 2, Laboratoire Imagerie Moleculaire et Fonctionnelle: de la physiologie a la therapie CNRS UMR 5231, Bordeaux Cedex (France); Service de Radiologie, Hopital Saint-Andre, CHU Bordeaux, Bordeaux (France); Seror, Olivier [Universite Victor Segalen Bordeaux 2, Laboratoire Imagerie Moleculaire et Fonctionnelle: de la physiologie a la therapie CNRS UMR 5231, Bordeaux Cedex (France); Service de Radiologie, Hopital Jean Verdier, Bondy (France); Sesay, Musa-Bahazid [Service d' Anesthesie Reanimation III, Hopital Pellegrin, CHU Bordeaux, Bordeaux (France); Grenier, Nicolas [Universite Victor Segalen Bordeaux 2, Laboratoire Imagerie Moleculaire et Fonctionnelle: de la physiologie a la therapie CNRS UMR 5231, Bordeaux Cedex (France); Service d' Imagerie Diagnostique et Therapeutique de l' Adulte, Hopital Pellegrin, CHU Bordeaux, Bordeaux (France)

2010-01-15

To assess the practical feasibility and effectiveness of real-time magnetic resonance (MR) temperature monitoring for the radiofrequency (RF) ablation of liver tumours in a clinical setting, nine patients (aged 49-87 years, five men and four women) with one malignant tumour (14-50 mm, eight hepatocellular carcinomas and one colorectal metastasis), were treated by 12-min RF ablation using a 1.5-T closed magnet for real-time temperature monitoring. The clinical monopolar RF device was filtered at 64 MHz to avoid electromagnetic interference. Real-time computation of thermal-dose (TD) maps, based on Sapareto and Dewey's equation, was studied to determine its ability to provide a clear end-point of the RF procedure. Absence of local recurrence on follow-up MR images obtained 45 days after the RF ablation was used to assess the apoptotic and necrotic prediction obtained by real-time TD maps. Seven out of nine tumours were completely ablated according to the real-time TD maps. Compared with 45-day follow-up MR images, TD maps accurately predicted two primary treatment failures, but were not relevant in the later progression of one case of secondary local tumour. The real-time TD concept is a feasible and promising monitoring method for the RF ablation of liver tumours. (orig.)

Tissue Necrosis Monitoring for HIFU Ablation with T1 Contrast MRI Imaging

Science.gov (United States)

Hwang, San-Chao; Yao, Ching; Kuo, Ih-Yuan; Tsai, Wei-Cheng; Chang, Hsu

2011-09-01

In MR-guided HIFU ablation, MTC (Magnetization Transfer Contrast) or perfusion imaging is usually used after ablation to evaluate the ablated area based on the thermally induced necrosis contrast. In our MR-guided HIFU ablation study, a T1 contrast MRI scan sequence has been used to distinguish between necrotic and non-necrotic tissue. The ablation of porcine meat in-vitro and in-vivo pig leg muscle show that the necrotic area of T1 contrast MRI image coincides with the photographs of sliced specimen. The sequence is considerably easier to apply than MTC or perfusion imaging, while giving good necrosis contrast. In addition, no injection of contrast agent is needed, allowing multiple scans to be applied throughout the entire ablation procedure.

Pulsed-laser ablation of co-deposits on JT-60 graphite tile

International Nuclear Information System (INIS)

Sakawa, Youichi; Watanabe, Daisuke; Shibahara, Takahiro; Sugiyama, Kazuyoshi; Tanabe, Tetsuo

2007-01-01

Pulsed laser ablation of the co-deposits on a JT-60 open-divertor tile using the fourth harmonic of a 20 ps-Nd: YAG laser has been investigated. With increasing the laser intensity, three regions, non-ablation region (NAR), weak-ablation region (WAR), and strong-ablation region (SAR) were distinguished. Transition from NAR to WAR and WAR to SAR occurred at the threshold laser intensity for laser ablation and that for strong ionization of carbon atoms, respectively. The ablation accompanied desorption of H 2 and C 2 H 2 , with minor contribution of other hydrocarbons, while production of H 2 O was small. In NAR and WAR the number of the hydrogen desorbed by the laser irradiation was less than that of hydrogen retained in the ablated volume, while in SAR it was much larger, owing to thermal desorption of hydrogen gas from the region surrounding the ablated volume. For the ablative removal of hydrogen isotopes, SAR is more desirable because of higher removal efficiency and less production of hydrocarbons

Pulsed-laser ablation of co-deposits on JT-60 graphite tile

Energy Technology Data Exchange (ETDEWEB)

Sakawa, Youichi [Institute of Laser Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871 (Japan)]. E-mail: sakawa-y@ile.osaka-u.ac.jp; Watanabe, Daisuke [Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Shibahara, Takahiro [Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Sugiyama, Kazuyoshi [Interdisciplinary School of Engineering Science, Kyushu University, Fukuoka, Fukuoka 812-8581 (Japan); Tanabe, Tetsuo [Interdisciplinary School of Engineering Science, Kyushu University, Fukuoka, Fukuoka 812-8581 (Japan)

2007-08-01

Pulsed laser ablation of the co-deposits on a JT-60 open-divertor tile using the fourth harmonic of a 20 ps-Nd: YAG laser has been investigated. With increasing the laser intensity, three regions, non-ablation region (NAR), weak-ablation region (WAR), and strong-ablation region (SAR) were distinguished. Transition from NAR to WAR and WAR to SAR occurred at the threshold laser intensity for laser ablation and that for strong ionization of carbon atoms, respectively. The ablation accompanied desorption of H{sub 2} and C{sub 2}H{sub 2}, with minor contribution of other hydrocarbons, while production of H{sub 2}O was small. In NAR and WAR the number of the hydrogen desorbed by the laser irradiation was less than that of hydrogen retained in the ablated volume, while in SAR it was much larger, owing to thermal desorption of hydrogen gas from the region surrounding the ablated volume. For the ablative removal of hydrogen isotopes, SAR is more desirable because of higher removal efficiency and less production of hydrocarbons.

Scientific ballooning in India Recent developments

Science.gov (United States)

Manchanda, R. K.

Established in 1971, the National Balloon Facility operated by TIFR in Hyderabad, India, is a unique facility in the country, which provides a complete solution in scientific ballooning. It is also one of its kind in the world since it combines both, the in-house balloon production and a complete flight support for scientific ballooning. With a large team working through out the year to design, fabricate and launch scientific balloons, the Hyderabad Facility is a unique centre of expertise where the balloon design, research and development, the production and launch facilities are located under one roof. Our balloons are manufactured from 100% indigenous components. The mission specific balloon design, high reliability control and support instrumentation, in-house competence in tracking, telemetry, telecommand, data processing, system design and mechanics is its hallmark. In the past few years, we have executed a major programme of upgradation of different components of balloon production, telemetry and telecommand hardware and various support facilities. This paper focuses on our increased capability of balloon production of large sizes up to 780,000 m 3 using Antrix film, development of high strength balloon load tapes with the breaking strength of 182 kg, and the recent introduction of S-band telemetry and a commandable timer cut-off unit in the flight hardware. A summary of the various flights conducted in recent years will be presented along with the plans for new facilities.

Ballooning for Biologists: Mission Essentials for Flying Experiments on Large NASA Balloons

Science.gov (United States)

Smith, David J.; Sowa, Marianne

2017-01-01

Despite centuries of scientific balloon flights, only a handful of experiments have produced biologically-relevant results. Yet unlike orbital spaceflight, it is much faster and cheaper to conduct biology research with balloons, sending specimens to the near space environment of Earths stratosphere. Samples can be loaded the morning of a launch and sometimes returned to the laboratory within one day after flying. The National Aeronautics and Space Administration (NASA) flies large, unmanned scientific balloons from all over the globe, with missions ranging from hours to weeks in duration. A payload in the middle portion of the stratosphere (approx. 35 km above sea level) will be exposed to an environment similar to the surface of Mars: temperatures generally around -36 C, atmospheric pressure at a thin 1 kPa, relative humidity levels <1%, and a harsh illumination of ultraviolet (UV) and cosmic radiation levels (about 100 W/sq m and 0.1 mGy/d, respectively) that can be obtained nowhere else on the surface of the Earth, including environmental chambers and particle accelerator facilities attempting to simulate space radiation effects. Considering the operational advantages of ballooning and the fidelity of space-like stressors in the stratosphere, researchers in aerobiology, astrobiology, and space biology can benefit from balloon flight experiments as an intermediary step on the extraterrestrial continuum (ground, low Earth orbit, and deep space studies). Our presentation targets biologists with no background or experience in scientific ballooning. We will provide an overview of large balloon operations, biology topics that can be uniquely addressed in the stratosphere, and a roadmap for developing payloads to fly with NASA.

Careful treatment planning enables safe ablation of liver tumors adjacent to major blood vessels by percutaneous irreversible electroporation (IRE

Directory of Open Access Journals (Sweden)

Kos Bor

2015-09-01

Full Text Available Background. Irreversible electroporation (IRE is a tissue ablation method, which relies on the phenomenon of electroporation. When cells are exposed to a sufficiently electric field, the plasma membrane is disrupted and cells undergo an apoptotic or necrotic cell death. Although heating effects are known IRE is considered as non-thermal ablation technique and is currently applied to treat tumors in locations where thermal ablation techniques are contraindicated.

21 CFR 874.4100 - Epistaxis balloon.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Epistaxis balloon. 874.4100 Section 874.4100 Food... DEVICES EAR, NOSE, AND THROAT DEVICES Surgical Devices § 874.4100 Epistaxis balloon. (a) Identification. An epistaxis balloon is a device consisting of an inflatable balloon intended to control internal...

Rotational atherectomy ablation for an unexpandable stent under the guide of IVUS

Science.gov (United States)

Si, Daoyuan; Liu, Guohui; Tong, Yaliang; He, Yuquan

2018-01-01

Abstract Rationale: Inadequate stent expansion due to rigid calcified may result in restenosis lesions, but the available options are limited. Patient concerns: We report a case via the trans-radial approach of the severely underexpanded freshly deployed stent due to heavily calcified plaques Diagnoses: Coronary angiography revealed that there was no adequate expansion of the freshly deployed stent. Interventions: Under the guide of intravascular ultrasound (IVUS), rotational atherectomy (RA) successfully ablated the stent layers and the protruding calcified plaque. Followed by balloon angioplasty, the ablated segment was scaffolded with another stent, well expanded and documented by IVUS. Outcomes: The patient was uneventful during the procedure and remained angina free at the point of one year of clinical follow-up. Lessons: This case indicated that RA via the trans-radial approach could be a useful remedy in the situation of under-expansion of implanted stents, and the debulking should be performed under IVUS-guidance. PMID:29443790

Percutaneous laser ablation of benign and malignant thyroid nodules.

Science.gov (United States)

Papini, Enrico; Bizzarri, Giancarlo; Pacella, Claudio M

2008-10-01

Percutaneous image-guided procedures, largely based on thermal ablation, are at present under investigation for achieving a nonsurgical targeted cytoreduction in benign and malignant thyroid lesions. In several uncontrolled clinical trials and in two randomized clinical trials, laser ablation has demonstrated a good efficacy and safety for the shrinkage of benign cold thyroid nodules. In hyperfunctioning nodules, laser ablation induced a nearly 50% volume reduction with a variable frequency of normalization of thyroid-stimulating hormone levels. Laser ablation has been tested for the palliative treatment of poorly differentiated thyroid carcinomas, local recurrences or distant metastases. Laser ablation therapy is indicated for the shrinkage of benign cold nodules in patients with local pressure symptoms who are at high surgical risk. The treatment should be performed only by well trained operators and after a careful cytological evaluation. Laser ablation does not seem to be consistently effective in the long-term control of hyperfunctioning thyroid nodules and is not an alternative treatment to 131I therapy. Laser ablation may be considered for the cytoreduction of tumor tissue prior to external radiation therapy or chemotherapy of local or distant recurrences of thyroid malignancy that are not amenable to surgical or radioiodine treatment.

Developments of Highly Multiplexed, Multi-chroic Pixels for Balloon-Borne Platforms

Science.gov (United States)

Aubin, F.; Hanany, S.; Johnson, B. R.; Lee, A.; Suzuki, A.; Westbrook, B.; Young, K.

2018-02-01

We present our work to develop and characterize low thermal conductance bolometers that are part of sinuous antenna multi-chroic pixels (SAMP). We use longer, thinner and meandered bolometer legs to achieve 9 pW/K thermal conductance bolometers. We also discuss the development of inductor-capacitor chips operated at 4 K to extend the multiplexing factor of the frequency domain multiplexing to 105, an increase of 60% compared to the factor currently demonstrated for this readout system. This technology development is motivated by EBEX-IDS, a balloon-borne polarimeter designed to characterize the polarization of foregrounds and to detect the primordial gravity waves through their B-mode signature on the polarization of the cosmic microwave background. EBEX-IDS will operate 20,562 transition edge sensor bolometers spread over 7 frequency bands between 150 and 360 GHz. Balloon and satellite platforms enable observations at frequencies inaccessible from the ground and with higher instantaneous sensitivity. This development improves the readiness of the SAMP and frequency domain readout technologies for future satellite applications.

Radiofrequency ablation of liver tumors (II): clinical application and outcomes.

Science.gov (United States)

Vanagas, Tomas; Gulbinas, Antanas; Pundzius, Juozas; Barauskas, Giedrius

2010-01-01

Radiofrequency ablation is one of the alternatives in the management of liver tumors, especially in patients who are not candidates for surgery. The aim of this article is to review applicability of radiofrequency ablation achieving complete tumor destruction, utility of imaging techniques for patients' follow-up, indications for local ablative procedures, procedure-associated morbidity and mortality, and long-term results in patients with different tumors. The success of local thermal ablation consists in creating adequate volumes of tissue destruction with adequate "clear margin," depending on improved delivery of radiofrequency energy and modulated tissue biophysiology. Different volumes of coagulation necrosis are achieved applying different types of electrodes, pulsing energy sources, utilizing sophisticated ablation schemes. Some additional methods are used to increase the overall deposition of energy through alterations in tissue electrical conductivity, to improve heat retention within the tissue, and to modulate tolerance of tumor tissue to hyperthermia. Contrast-enhanced computed tomography, magnetic resonance imaging, ultrasound or positron emission tomography are applied to control the effectiveness of radiofrequency ablation. The long-term results of radiofrequency ablation are controversial.

Feasibility of magnetic resonance imaging-guided high intensity focused ultrasound therapy for ablating uterine fibroids in patients with bowel lies anterior to uterus

International Nuclear Information System (INIS)

Zhang Lian; Chen Wenzhi; Liu Yinjiang; Hu Xiao; Zhou Kun; Chen Li; Peng Song; Zhu Hui; Zou Huiling; Bai Jin; Wang Zhibiao

2010-01-01

Purpose: To prospectively evaluate the feasibility of magnetic resonance (MR) imaging-guided high intensity focused ultrasound (HIFU) therapeutic ablation of uterine fibroids in patients with bowel lies anterior to uterus. Materials and methods: Twenty-one patients with 23 uterine fibroids underwent MR imaging-guided high intensity focused ultrasound treatment, with a mean age of 39.4 ± 6.9 (20-49) years, with fibroids average measuring 6.0 ± 1.6 (range, 2.9-9.5) cm in diameter. After being compressed with a degassed water balloon on abdominal wall, MR imaging-guided high intensity focused ultrasound treatment was performed under conscious sedation by using fentanyl and midazolam. This procedure was performed by a Haifu JM focused ultrasound tumour therapeutic system (JM2.5C, Chongqing Haifu Technology Co., Ltd., China), in combination with a 1.5-Tesla MRI system (Symphony, Siemens, Germany), which provides real-time guidance and control. Contrast-enhanced MR imaging was performed to evaluate the efficacy of thermal ablation immediately and 3 months after HIFU treatment. The treatment time and adverse events were recorded. Results: The mean fibroid volume was 97.0 ± 78.3 (range, 12.7-318.3) cm 3 . According to the treatment plan, an average 75.0 ± 11.4% (range, 37.8-92.4%) of the fibroid volume was treated. The mean fibroid volume immediately after HIFU was 109.7 ± 93.1 (range, 11.9-389.6) cm 3 , slightly enlarged because of edema. The average non-perfused volume was 83.3 ± 71.7 (range, 7.7-282.9) cm 3 , the average fractional ablation, which was defined as non-perfused volume divided by the fibroid volume immediately after HIFU treatment, was 76.9 ± 18.7% (range, 21.0-97.0%). There were no statistically significant differences between the treatment volume and the non-perfused volume. Follow-up magnetic resonance imaging (MRI) at 3 months obtained in 12 patients, the fibroid volume decreased by 31.4 ± 29.3% (range, -1.9 to 60.0%) in average, with paired t

Feasibility of magnetic resonance imaging-guided high intensity focused ultrasound therapy for ablating uterine fibroids in patients with bowel lies anterior to uterus

Energy Technology Data Exchange (ETDEWEB)

Zhang Lian; Chen Wenzhi [Clinical Center for Tumour Therapy of 2nd Affiliated Hospital of Chongqing University of Medical Sciences, Chongqing 400010 (China); Liu Yinjiang; Hu Xiao [National Engineering Research Center of Ultrasound Medicine, Chongqing 400010 (China); Zhou Kun [Clinical Center for Tumour Therapy of 2nd Affiliated Hospital of Chongqing University of Medical Sciences, Chongqing 400010 (China); Chen Li [National Engineering Research Center of Ultrasound Medicine, Chongqing 400010 (China); Peng Song; Zhu Hui [Clinical Center for Tumour Therapy of 2nd Affiliated Hospital of Chongqing University of Medical Sciences, Chongqing 400010 (China); Zou Huiling [National Engineering Research Center of Ultrasound Medicine, Chongqing 400010 (China); Bai Jin [Institute of Ultrasound Engineering in Medicine of Chongqing University of Medical Sciences, Chongqing 400016 (China); Wang Zhibiao [Clinical Center for Tumour Therapy of 2nd Affiliated Hospital of Chongqing University of Medical Sciences, Chongqing 400010 (China); National Engineering Research Center of Ultrasound Medicine, Chongqing 400010 (China); Institute of Ultrasound Engineering in Medicine of Chongqing University of Medical Sciences, Chongqing 400016 (China)], E-mail: wangzhibiao@haifu.com.cn

2010-02-15

Purpose: To prospectively evaluate the feasibility of magnetic resonance (MR) imaging-guided high intensity focused ultrasound (HIFU) therapeutic ablation of uterine fibroids in patients with bowel lies anterior to uterus. Materials and methods: Twenty-one patients with 23 uterine fibroids underwent MR imaging-guided high intensity focused ultrasound treatment, with a mean age of 39.4 {+-} 6.9 (20-49) years, with fibroids average measuring 6.0 {+-} 1.6 (range, 2.9-9.5) cm in diameter. After being compressed with a degassed water balloon on abdominal wall, MR imaging-guided high intensity focused ultrasound treatment was performed under conscious sedation by using fentanyl and midazolam. This procedure was performed by a Haifu JM focused ultrasound tumour therapeutic system (JM2.5C, Chongqing Haifu Technology Co., Ltd., China), in combination with a 1.5-Tesla MRI system (Symphony, Siemens, Germany), which provides real-time guidance and control. Contrast-enhanced MR imaging was performed to evaluate the efficacy of thermal ablation immediately and 3 months after HIFU treatment. The treatment time and adverse events were recorded. Results: The mean fibroid volume was 97.0 {+-} 78.3 (range, 12.7-318.3) cm{sup 3}. According to the treatment plan, an average 75.0 {+-} 11.4% (range, 37.8-92.4%) of the fibroid volume was treated. The mean fibroid volume immediately after HIFU was 109.7 {+-} 93.1 (range, 11.9-389.6) cm{sup 3}, slightly enlarged because of edema. The average non-perfused volume was 83.3 {+-} 71.7 (range, 7.7-282.9) cm{sup 3}, the average fractional ablation, which was defined as non-perfused volume divided by the fibroid volume immediately after HIFU treatment, was 76.9 {+-} 18.7% (range, 21.0-97.0%). There were no statistically significant differences between the treatment volume and the non-perfused volume. Follow-up magnetic resonance imaging (MRI) at 3 months obtained in 12 patients, the fibroid volume decreased by 31.4 {+-} 29.3% (range, -1.9 to 60

Use of Radiofrequency Ablation in Benign Thyroid Nodules: A Literature Review and Updates

OpenAIRE

Wong, KP; Lang, HHB

2013-01-01

Successful thermal ablation using radiofrequency has been reported in various tumors including liver or kidney tumors. Nonsurgical minimally invasive ablative therapy such as radiofrequency ablation (RFA) has been reported to be a safe and efficient treatment option in managing symptomatic cold thyroid nodules or hyperfunctioning thyroid nodules. Pressure and cosmetic symptoms have been shown to be significantly improved both in the short and long terms after RFA. For hyperfunctioning thyroid...

Experimental and clinical studies with radiofrequency-induced thermal endometrial ablation for functional menorrhagia

Energy Technology Data Exchange (ETDEWEB)

Phipps, J.H.; Lewis, B.V.; Prior, M.V.; Roberts, T. (Watford General Hospital, Herts (England))

1990-11-01

A method of ablating the endometrium has been introduced into clinical practice that uses radiofrequency electromagnetic energy to heat the endometrium, using a probe inserted through the cervix. Preliminary studies suggest that over 80% of patients treated will develop either amenorrhea or a significant reduction in flow. The advantages of radiofrequency endometrial ablation over laser ablation or resection are the avoidance of intravascular fluid absorption, simplicity (no special operative hysteroscopic skills are required), speed of operation, and reduced cost compared with the Nd:YAG laser. In this paper, we describe the experimental studies performed during development of this new technique.

Launching Garbage-Bag Balloons.

Science.gov (United States)

Kim, Hy

1997-01-01

Presents a modification of a procedure for making and launching hot air balloons made out of garbage bags. Student instructions for balloon construction, launching instructions, and scale diagrams are included. (DDR)

Effects of Non-Equilibrium Chemistry and Darcy-Forchheimer Flow of Pyrolysis Gas for a Charring Ablator

Science.gov (United States)

Chen, Yih-Kanq; Milos, Frank S.

2011-01-01

The Fully Implicit Ablation and Thermal Response code, FIAT, simulates pyrolysis and ablation of thermal protection materials and systems. The governing equations, which include energy conservation, a three-component decomposition model, and a surface energy balance, are solved with a moving grid. This work describes new modeling capabilities that are added to a special version of FIAT. These capabilities include a time-dependent pyrolysis gas flow momentum equation with Darcy-Forchheimer terms and pyrolysis gas species conservation equations with finite-rate homogeneous chemical reactions. The total energy conservation equation is also enhanced for consistency with these new additions. Parametric studies are performed using this enhanced version of FIAT. Two groups of analyses of Phenolic Impregnated Carbon Ablator (PICA) are presented. In the first group, an Orion flight environment for a proposed Lunar-return trajectory is considered. In the second group, various test conditions for arcjet models are examined. The central focus of these parametric studies is to understand the effect of pyrolysis gas momentum transfer on PICA material in-depth thermal responses with finite-rate, equilibrium, or frozen homogeneous gas chemistry. Results are presented, discussed, and compared with those predicted by the baseline PICA/FIAT ablation and thermal response model developed by the Orion Thermal Protection System Advanced Development Project.

Pulsed Dose Radiofrequency Before Ablation of Medial Branch of the Lumbar Dorsal Ramus for Zygapophyseal Joint Pain Reduces Post-procedural Pain.

Science.gov (United States)

Arsanious, David; Gage, Emmanuel; Koning, Jonathon; Sarhan, Mazin; Chaiban, Gassan; Almualim, Mohammed; Atallah, Joseph

2016-01-01

One of the potential side effects with radiofrequency ablation (RFA) includes painful cutaneous dysesthesias and increased pain due to neuritis or neurogenic inflammation. This pain may require the prescription of opioids or non-opioid analgesics to control post-procedural pain and discomfort. The goal of this study is to compare post-procedural pain scores and post-procedural oral analgesic use in patients receiving continuous thermal radiofrequency ablation versus patients receiving pulsed dose radiofrequency immediately followed by continuous thermal radiofrequency ablation for zygopophaseal joint disease. This is a prospective, double-blinded, randomized, controlled trial. Patients who met all the inclusion criteria and were not subject to any of the exclusion criteria were required to have two positive diagnostic medial branch blocks prior to undergoing randomization, intervention, and analysis. University hospital. Eligible patients were randomized in a 1:1 ratio to either receive thermal radiofrequency ablation alone (standard group) or pulsed dose radiofrequency (PDRF) immediately followed by thermal radiofrequency ablation (investigational group), all of which were performed by a single Board Certified Pain Medicine physician. Post-procedural pain levels between the two groups were assessed using the numerical pain Scale (NPS), and patients were contacted by phone on post-procedural days 1 and 2 in the morning and afternoon regarding the amount of oral analgesic medications used in the first 48 hours following the procedure. Patients who received pulsed dose radiofrequency followed by continuous radiofrequency neurotomy reported statistically significantly lower post-procedural pain scores in the first 24 hours compared to patients who received thermal radiofrequency neurotomy alone. These patients also used less oral analgesic medication in the post-procedural period. These interventions were carried out by one board accredited pain physician at one

Adaptive ultrasound temperature imaging for monitoring radiofrequency ablation.

Directory of Open Access Journals (Sweden)

Yi-Da Liu

Full Text Available Radiofrequency ablation (RFA has been widely used as an alternative treatment modality for liver tumors. Monitoring the temperature distribution in the tissue during RFA is required to assess the thermal dosage. Ultrasound temperature imaging based on the detection of echo time shifts has received the most attention in the past decade. The coefficient k, connecting the temperature change and the echo time shift, is a medium-dependent parameter used to describe the confounding effects of changes in the speed of sound and thermal expansion as temperature increases. The current algorithm of temperature estimate based on echo time shift detection typically uses a constant k, resulting in estimation errors when ablation temperatures are higher than 50°C. This study proposes an adaptive-k algorithm that enables the automatic adjustment of the coefficient k during ultrasound temperature monitoring of RFA. To verify the proposed algorithm, RFA experiments on in vitro porcine liver samples (total n = 15 were performed using ablation powers of 10, 15, and 20 W. During RFA, a clinical ultrasound system equipped with a 7.5-MHz linear transducer was used to collect backscattered signals for ultrasound temperature imaging using the constant- and adaptive-k algorithms. Concurrently, an infrared imaging system and thermocouples were used to measure surface temperature distribution of the sample and internal ablation temperatures for comparisons with ultrasound estimates. Experimental results demonstrated that the proposed adaptive-k method improved the performance in visualizing the temperature distribution. In particular, the estimation errors were also reduced even when the temperature of the tissue is higher than 50°C. The proposed adaptive-k ultrasound temperature imaging strategy has potential to serve as a thermal dosage evaluation tool for monitoring high-temperature RFA.

Pellet ablation and ablation model development

International Nuclear Information System (INIS)

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

JACEE long duration balloon flights

International Nuclear Information System (INIS)

Burnett, T.; Iwai, J.; Lord, J.J.; Strausz, S.; Wilkes, R.J.; Dake, S.; Oda, H.; Miyamura, O.; Fuki, M.; Jones, W.V.; Gregory, J.; Hayashi, T.; Takahashi, U.; Tominaga, Y.; Wefel, J.P.; Fountain, W.; Derrickson, J.; Parnell, T.A.; Roberts, E.; Tabuki, T.; Watts, J.W.

1989-01-01

JACEE balloon-borne emulsion chamber detectors are used to observe the spectra and interactions of cosmic ray protons and nuclei in the energy range 1-100A TeV. Experience with long duration mid-latitude balloon flights and characteristics of the detector system that make it ideal for planned Antarctic balloon flights are discussed. 5 refs., 2 figs

Modeling of Heat Transfer and Ablation of Refractory Material Due to Rocket Plume Impingement

Science.gov (United States)

Harris, Michael F.; Vu, Bruce T.

2012-01-01

CR Tech's Thermal Desktop-SINDA/FLUINT software was used in the thermal analysis of a flame deflector design for Launch Complex 39B at Kennedy Space Center, Florida. The analysis of the flame deflector takes into account heat transfer due to plume impingement from expected vehicles to be launched at KSC. The heat flux from the plume was computed using computational fluid dynamics provided by Ames Research Center in Moffet Field, California. The results from the CFD solutions were mapped onto a 3-D Thermal Desktop model of the flame deflector using the boundary condition mapping capabilities in Thermal Desktop. The ablation subroutine in SINDA/FLUINT was then used to model the ablation of the refractory material.

Fasting and meal-suppressed ghrelin levels before and after intragastric balloons and balloon-induced weight loss

NARCIS (Netherlands)

Mathus-Vliegen, E. M. H.; Eichenberger, R. I.

2014-01-01

Intragastric balloons may be an option for obese patients with weight loss failure. Its mode of action remains enigmatic. We hypothesised depressed fasting ghrelin concentrations and enhanced meal suppression of ghrelin secretion by the gastric fundus through balloon contact and balloon-induced

Technologies developed by CNES balloon team

Science.gov (United States)

Sosa-Sesma, Sergio; Charbonnier, Jean-Marc; Deramecourt, Arnaud

CNES balloon team develops and operates all the components of this kind of vehicle: it means envelope and gondola. This abstract will point out only developments done for envelope. Nowadays CNES offers to scientists four types of envelops that cover a large range of mission demands. These envelops are: 1. Zero pressure balloons: Size going from 3,000m3 to 600,000m3, this kind of envelop is ideal for short duration flights (a few hours) but if we use an intelligent management of ballast consumption and if we chose the best launch site, it is possible to perform medium duration flights (10/20 days depending on the ballast on board). Flight train mass starts at 50kg for small balloons and reach 1000kg for larger ones. Zero pressure balloons are inflated with helium gas. 2. Super pressure balloons: Diameter going from 2.5m to 12m, this kind of envelop is ideal for long duration flights (1 to 6 months). Flight train is inside the envelop for small balloons, it means 2.5 diameter meters which is usually called BPCL (Super pressure balloon for Earth boundary layer) and it is about 3kg of mass. Larger ones could lift external flight trains about 50kg of mass. Super pressure balloons are inflated with helium gas. 3. MIR balloons: Size going from 36,000m3 to 46,000m3. Ceiling is reach with helium gas but after three days helium is no longer present inside and lift force is produced by difference of temperature between air inside and air of atmosphere. Flight trains must not be over 50kg. 4. Aero Clipper balloons: A concept to correlate measurements done in oceans and in nearest layers of atmosphere simultaneously. Flight train is made by a "fish" that drags inside water and an atmospheric gondola few meters above "fish", both pushed by a balloon which profits of the wind force. Materials used for construction and assembling depend on balloon type; they are usually made of polyester or polyethylene. Thickness varies from 12 micrometers to 120 micrometers. Balloon assembling

Real-time near-IR imaging of laser-ablation crater evolution in dental enamel

Science.gov (United States)

Darling, Cynthia L.; Fried, Daniel

2007-02-01

We have shown that the enamel of the tooth is almost completely transparent near 1310-nm in the near-infrared and that near-IR (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue and for observing defects in the interior of the tooth. Lasers are now routinely used for many applications in dentistry including the ablation of dental caries. The objective of this study was to test the hypothesis that real-time NIR imaging can be used to monitor laser-ablation under varying conditions to assess peripheral thermal and transient-stress induced damage and to measure the rate and efficiency of ablation. Moreover, NIR imaging may have considerable potential for monitoring the removal of demineralized areas of the tooth during cavity preparations. Sound human tooth sections of approximately 3-mm thickness were irradiated by a CO II laser under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with band-pass filter centered at 131--nm combined with an InGaAs focal plane array with a NIR zoom microscope in transillumination. Due to the high transparency of enamel at 1310-nm, laser-incisions were clearly visible to the dentin-enamel junction and crack formation, dehydration and irreversible thermal changes were observed during ablation. This study showed that there is great potential for near-IR imaging to monitor laser-ablation events in real-time to: assess safe laser operating parameters by imaging thermal and stress-induced damage, elaborate the mechanisms involved in ablation such as dehydration, and monitor the removal of demineralized enamel.

Radiofrequency ablation with epinephrine injection: in vivo study in normal pig livers

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyoung Jung; Lee, Dong Hoo; Lim, Joo Won; Ko, Young Tae; Kim, Youn Wha; Choi, Bong Keun [Kyung Hee University Medical Center, Seoul (Korea, Republic of)

2007-07-15

We wanted to evaluate whether epinephrine injection prior to radiofrequency (RF) ablation can increase the extent of thermally mediated coagulation in vivo normal pig liver tissue. Eighteen RF ablation zones were created in six pigs using a 17-gauge internally cooled electrode under ultrasound guidance. Three RF ablation zones were created in each pig under three conditions: RF ablation alone, RF ablation after the injection of 3 mL of normal saline, and RF ablation after the injection of 3 mL of epinephrine (1:10,000 solution). After the RF ablation, we measured the short and long diameters of the white zones in the gross specimens. Three of the RF ablations were technically unsuccessful; therefore, measurement of white zone was finally done in 15 RF ablation zones. The mean short and long diameters of the white zone of the RF ablation after epinephrine injection (17.2 mm {+-} 1.8 and 20.8 mm {+-} 3.7, respectively) were larger than those of RF ablation only (10 mm {+-} 1.2 and 12.2 mm {+-} 1.1, respectively) and RF ablation after normal saline injection (12.8 mm {+-} 1.5 and 15.6 mm {+-} 2.5, respectively) ({rho} < .05). RF ablation with epinephrine injection can increase the diameter of the RF ablation zone in normal pig liver tissue.

Experimental study on 800 nm femtosecond laser ablation of fused silica in air and vacuum

Energy Technology Data Exchange (ETDEWEB)

Xu, Shi-zhen, E-mail: xusz@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yao, Cai-zhen; Liao, Wei [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yuan, Xiao-dong, E-mail: yxd66my@163.com [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Wang, Tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Zu, Xiao-tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2016-10-15

Ablation rates of fused silica were studied as a function of femtosecond laser pulse fluences (0.7–41 J/cm{sup 2}) in air and vacuum. The experiment was conducted by using a Ti:sapphire laser that emits radiation at 800 nm with a pulse width of 35 fs and a repetition rate of 10 Hz. The morphology and ablation depth of laser-induced damage crater were evaluated by using optical microscopy and scanning electron microscopy (SEM). Ablation rates were calculated from the depth of craters induced by multiple laser pulses. Results showed that two ablation regimes, i.e. non-thermal and thermal ablation co-existed in air and vacuum at low and moderate fluences. A drop of ablation rate was observed at high fluence (higher than 9.5 J/cm{sup 2}) in air. While in vacuum, the ablation rate increased continuously with the increasing of laser fluence and much higher than that in air. The drop of ablation rate observed at high fluence in air was due to the strong defocusing effects associated with the non-equilibrium ionization of air. Furthermore, the laser-induced damage threshold (LIDT), which was determined from the relationship between crater area and the logarithm of laser energy, was found to depend on the number of incident pulses on the same spot, and similar phenomenon was observed in air and vacuum.

Two Tethered Balloon Systems

Science.gov (United States)

Youngbluth, Otto; Owens, Thomas L.; Storey, Richard W.

1990-01-01

Systems take meteorological measurements for variety of research projects. Report describes work done by NASA Langley Research Center in atmospheric research using tethered balloon systems composed of commercially available equipment. Two separate tethered balloon systems described in report have payloads and configurations tailored to requirements of specific projects. Each system capable of measuring atmospheric parameter or species in situ and then telemetering this data in real time to ground station. Meteorological data and concentration of ozone typically measured. Indicates instrumented tethered balloon systems have distinct advantages over other systems for gathering data on troposphere.

Recent Developments in Scientific Research Ballooning

International Nuclear Information System (INIS)

Jones, W. Vernon

2007-01-01

The National Aeronautics and Space Administration (NASA) Balloon Program is committed to meeting the need for extended duration scientific investigations by providing advanced balloon vehicles and support systems. A sea change in ballooning capability occurred with the inauguration of 8 - 20 day flights around Antarctica in the early 1990's. The attainment of 28-31 day flights and a record-breaking 42-day flight in, respectively, two and three circumnavigations of the continent has greatly increased the expectations of the scientific users. A new super-pressure balloon is currently under development for future flights of 60-100 days at any latitude, which would bring another sea change in scientific research ballooning

Pioneering Space Research with Balloons

Science.gov (United States)

Jones, W. V.

NASA s Scientific Ballooning Planning Team has concluded that ballooning enables significant scientific discoveries while providing test beds for space instruments and training for young scientists Circumpolar flights around Antarctica have been spectacularly successful with fight durations up to 42 days Demand for participation in this Long-Duration Balloon LDB program a partnership with the U S National Science Foundation Office of Polar Programs is greater than the current capacity of two flights per campaign Given appropriate international agreements LDB flights in the Northern Hemisphere would be competitive with Antarctic flights and super-pressure balloons would allow comparable flights at any latitude The Balloon Planning Team made several recommendations for LDB flights provide a reliable funding source for sophisticated payloads extend the Antarctic capability to three flights per year and develop a comparable capability in the Arctic provide aircraft for intact-payload recovery develop a modest trajectory modification capability to enable longer flights and enhance super-pressure balloons to carry 1-ton payloads to 38 km Implementation of these recommendations would facilitate frequent access to near-space for cutting-edge research and technology development for a wide range of investigations

Modeling of beam-target interaction during pulsed electron beam ablation of graphite: Case of melting

Energy Technology Data Exchange (ETDEWEB)

Ali, Muddassir, E-mail: mx1_ali@laurentian.ca; Henda, Redhouane

2017-02-28

Highlights: • Modeling of ablation stage induced during pulsed electron beam ablation (PEBA). • Thermal model to describe heating, melting and vaporization of a graphite target. • Model results show good accordance with reported data in the literature. - Abstract: A one-dimensional thermal model based on a two-stage heat conduction equation is employed to investigate the ablation of graphite target during nanosecond pulsed electron beam ablation. This comprehensive model accounts for the complex physical phenomena comprised of target heating, melting and vaporization upon irradiation with a polyenergetic electron beam. Melting and vaporization effects induced during ablation are taken into account by introducing moving phase boundaries. Phase transition induced during ablation is considered through the temperature dependent thermodynamic properties of graphite. The effect of electron beam efficiency, power density, and accelerating voltage on ablation is analyzed. For an electron beam operating at an accelerating voltage of 15 kV and efficiency of 0.6, the model findings show that the target surface temperature can reach up to 7500 K at the end of the pulse. The surface begins to melt within 25 ns from the pulse start. For the same process conditions, the estimated ablation depth and ablated mass per unit area are about 0.60 μm and 1.05 μg/mm{sup 2}, respectively. Model results indicate that ablation takes place primarily in the regime of normal vaporization from the surface. The results obtained at an accelerating voltage of 15 kV and efficiency factor of 0.6 are satisfactorily in good accordance with available experimental data in the literature.

Development of a New Coaxial Balloon Catheter System for Balloon-Occluded Retrograde Transvenous Obliteration (B-RTO)

International Nuclear Information System (INIS)

Tanoue, Shuichi; Kiyosue, Hiro; Matsumoto, Shunro; Hori, Yuzo; Okahara, Mika; Kashiwagi, Junji; Mori, Hiromu

2006-01-01

Purpose. To develop a new coaxial balloon catheter system and evaluate its clinical feasibility for balloon-occluded retrograde transvenous obliteration (B-RTO). Methods. A coaxial balloon catheter system was constructed with 9 Fr guiding balloon catheter and 5 Fr balloon catheter. A 5 Fr catheter has a high flexibility and can be coaxially inserted into the guiding catheter in advance. The catheter balloons are made of natural rubber and can be inflated to 2 cm (guiding) and 1 cm (5 Fr) maximum diameter. Between July 2003 and April 2005, 8 consecutive patients (6 men, 2 women; age range 33-72 years, mean age 55.5 years) underwent B-RTO using the balloon catheter system. Five percent ethanolamine oleate iopamidol (EOI) was used as sclerosing agent. The procedures, including maneuverability of the catheter, amount of injected sclerosing agent, necessity for coil embolization of collateral draining veins, and initial clinical results, were evaluated retrospectively. The occlusion rate was assessed by postcontrast CT within 2 weeks after B-RTO. Results. The balloon catheter could be advanced into the proximal potion of the gastrorenal shunt beyond the collateral draining vein in all cases. The amount of injected EOI ranged from 3 to 34 ml. Coil embolization of the collateral draining vein was required in 2 cases. Complete obliteration of gastric varices on initial follow-up CT was obtained in 7 cases. The remaining case required re-treatment that resulted in complete obstruction of the varices after the second B-RTO. No procedure-related complications were observed. Conclusion. B-RTO using the new coaxial balloon catheter is feasible. Gastric varices can be treated more simply by using this catheter system

In-vitro ablation of fibrocartilage by XeCl excimer laser

Science.gov (United States)

Buchelt, Martin; Papaioannou, Thanassis; Fishbein, Michael C.; Peters, Werner; Beeder, Clain; Grundfest, Warren S.

1991-07-01

A 308 nm excimer laser was employed for ablation of human fibrocartilage. Experiments were conducted in vitro. The tissue response was investigated with respect to dosimetry (ablation rate versus radiant exposure) and thermal effect (thermographic analysis). Irradiation was performed via a 600 um fiber, with radiant exposures ranging between 20mj/mm2 and 80mj/mm2, at 20Hz. The ablation rates were found to range from 3um/pulse to 80um/pulse depending on the radiant exposure and/or the applied pressure on the delivery system. Thermographic analysis, during ablation, revealed maximum average temperatures of about 65 degree(s)C. Similar measurements performed, for the purpose of comparison, with a CW Nd:YAG and a CW CO2 laser showed higher values, of the order of 200 degree(s)C.

Complications of balloon packing in epistaxis

NARCIS (Netherlands)

Vermeeren, Lenka; Derks, Wynia; Fokkens, Wytske; Menger, Dirk Jan

2015-01-01

Although balloon packing appears to be efficient to control epistaxis, severe local complications can occur. We describe four patients with local lesions after balloon packing. Prolonged balloon packing can cause damage to nasal mucosa, septum and alar skin (nasal mucosa, the cartilaginous skeleton

Critical appraisal of paclitaxel balloon angioplasty for femoral-popliteal arterial disease.

Science.gov (United States)

Herten, Monika; Torsello, Giovanni B; Schönefeld, Eva; Stahlhoff, Stefan

2016-01-01

Peripheral arterial disease, particularly critical limb ischemia, is an area with urgent need for optimized therapies because, to date, vascular interventions often have limited life spans. In spite of initial encouraging technical success after femoropopliteal percutaneous transluminal angioplasty or stenting, postprocedural restenosis remains the major problem. The challenging idea behind the drug-coated balloon (DCB) concept is the biological modification of the injury response after balloon dilatation. Antiproliferative drugs administered via DCBs or drug-eluting stents are able to suppress neointimal hyperplasia, the main cause of restenosis. This article reviews the results of DCB treatments of femoropopliteal and infrapopliteal lesions in comparison to standard angioplasty with uncoated balloons. A systematic literature search was performed in 1) medical journals (ie, MEDLINE), 2) international registers for clinical studies (ie, www.clinicaltrials.gov), and 3) abstracts of scientific sessions. Several controlled randomized trials with follow-up periods of up to 5 years demonstrated the efficacy of paclitaxel -DCB technology. However, calcified lesions seem to affect the efficacy of DCB. Combinations of preconditioning methods with DCBs showed promising results. Although the mechanical abrasion of calcium via atherectomy or laser ablation showed favorable periprocedural results, the long-term impact on restenosis and clinical outcome has to be demonstrated. Major advantages of the DCBs are the rapid delivery of drug at uniform concentrations with a single dose, their efficacy in areas wherein stents have been contraindicated until now (ie, bifurcation, ostial lesions), and in leaving no stent scaffold behind. Reinterventions are easier to perform because DCBs leave no metal behind. Various combinations of DCBs with other treatment modalities may prove to be viable options in future. The follow-up results of clinical studies will evaluate the long-term impact

Comparative study of excimer and erbium:YAG lasers for ablation of structural components of the knee

Science.gov (United States)

Vari, Sandor G.; Shi, Wei-Qiang; van der Veen, Maurits J.; Fishbein, Michael C.; Miller, J. M.; Papaioannou, Thanassis; Grundfest, Warren S.

1991-05-01

This study was designed to compare the efficiency and thermal effect of a 135 ns pulsed-stretched XeCl excimer laser (308 nm) and a free-running Erbium:YAG laser (2940 nm) with 200 microsecond(s) pulse duration for ablation of knee joint structures (hyaline and fibrous cartilage, tendon and bone). The radiant exposure used for tissue ablation ranged from 2 to 15 J/cm2 for the XeCl excimer and from 33 to 120 J/cm2 for Er:YAG. The excimer and Er:YAG lasers were operated at 4 and 5 Hz respectively. The ablative laser energy was delivered to tissue through fibers. Ablation rates of soft tissues (hyaline and fibrous cartilage, tendon) varied from 8.5 to 203 micrometers /pulse for excimer and from 8.2 to 273 micrometers /pulse for Er:YAG lasers. Ablation rates of soft tissues are linearly dependent on the radiant exposure. Within the range of parameters tested all the tissues except the bone could be rapidly ablated by both lasers. Bone ablation was much less efficient, requiring 15 J/cm2 and 110 J/cm2 radiant exposure for excimer and Er:YAG lasers to ablate 9.5 and 8.2 micrometers tissue per pulse. However, excimer laser ablation produced less thermal damage in the tissues studied compared to Er:YAG at the same laser parameters. The authors conclude that both lasers are capable of efficient knee joint tissue ablation. XeCl excimer laser requires an order of magnitude less energy than Er:YAG laser for comparable tissue ablation.

Femtosecond laser ablation of polytetrafluoroethylene (Teflon) in ambient air

International Nuclear Information System (INIS)

Wang, Z.B.; Hong, M.H.; Lu, Y.F.; Wu, D.J.; Lan, B.; Chong, T.C.

2003-01-01

Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (bio-compatible, nonflammable, antiadhesive, and heat resistant). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of PTFE in ambient air by a Ti:sapphire femtosecond laser (780 nm, 110 fs) is investigated. It is found that the pulse number on each irradiated surface area must be large enough for a clear edge definition and the ablated depth increases with the pulse number. The air ionization effect at high laser fluences not only degrades the ablated structures quality but also reduces the ablation efficiency. High quality microstructures are demonstrated with controlling laser fluence below a critical fluence to exclude the air ionization effect. The ablated microstructures show strong adhesion property to liquids and clear edges that are suitable for bio-implantation applications. Theoretical calculation is used to analyze the evolution of the ablated width and depth at various laser fluences

The TopHat experiment: A balloon-borne instrument for mapping millimeter and submillimeter emission

DEFF Research Database (Denmark)

Silverberg, R.F.; Cheng, E.S.; Aguirre, J.E.

2005-01-01

The TopHat experiment was designed to measure the anisotropy in the cosmic microwave background radiation on angular scales from 0.degrees 3 to 30 degrees and the thermal emission from both Galactic and extragalactic dust. The balloon-borne instrument had five spectral bands spanning frequencies ...

The Tethered Balloon Current Generator - A space shuttle-tethered subsatellite for plasma studies and power generation

Science.gov (United States)

Williamson, P. R.; Banks, P. M.

1976-01-01

The objectives of the Tethered Balloon Current Generator experiment are to: (1) generate relatively large regions of thermalized, field-aligned currents, (2) produce controlled-amplitude Alfven waves, (3) study current-driven electrostatic plasma instabilities, and (4) generate substantial amounts of power or propulsion through the MHD interaction. A large balloon (a diameter of about 30 m) will be deployed with a conducting surface above the space shuttle at a distance of about 10 km. For a generally eastward directed orbit at an altitude near 400 km, the balloon, connected to the shuttle by a conducting wire, will be positive with respect to the shuttle, enabling it to collect electrons. At the same time, the shuttle will collect positive ions and, upon command, emit an electron beam to vary current flow in the system.

Modelling Hot Air Balloons.

Science.gov (United States)

Brimicombe, M. W.

1991-01-01

A macroscopic way of modeling hot air balloons using a Newtonian approach is presented. Misleading examples using a car tire and the concept of hot air rising are discussed. Pressure gradient changes in the atmosphere are used to explain how hot air balloons work. (KR)

Stress assisted selective ablation of ITO thin film by picosecond laser

Science.gov (United States)

Farid, Nazar; Chan, Helios; Milne, David; Brunton, Adam; M. O'Connor, Gerard

2018-01-01

Fast selective pattering with high precession on 175 nm ITO thin film with IR ps lasers is investigated. Ablation parameters are optimized with detailed studies on the scribed depth, topography, and particle generation using AFM and SEM. A comparison of 10 and 150 ps laser revealed that the shorter pulse (10 ps) laser is more appropriate in selective and partial ablation; up to 20 nm resolution for controlled depth with multipulses having energy below the damage threshold is demonstrated. The experimental results are interpreted to involve stress assisted ablation mechanism for the 10 ps laser while thermal ablation along with intense melting occurs for 150 ps laser. The transition between these regimes is estimated to occur at approximately 30 ps.

Solar research with stratospheric balloons

Science.gov (United States)

Vázquez, Manuel; Wittmann, Axel D.

Balloons, driven by hot air or some gas lighter than air, were the first artificial machines able to lift payloads (including humans) from the ground. After some pioneering flights the study of the physical properties of the terrestrial atmosphere constituted the first scientific target. A bit later astronomers realized that the turbulence of the atmospheric layers above their ground-based telescopes deteriorated the image quality, and that balloons were an appropriate means to overcome, total or partially, this problem. Some of the most highly-resolved photographs and spectrograms of the sun during the 20th century were actually obtained by balloon-borne telescopes from the stratosphere. Some more recent projects of solar balloon astronomy will also be described.

Effect of Nanoclay on Mechanical Properties and Ablation Behavior of a Nitrile-Based Heat Insulator

Directory of Open Access Journals (Sweden)

Fatemeh Arabgol

2013-02-01

Full Text Available Thermal insulation of rocket motor chamber is one of the most important functions of elastomeric ablative material. Combustion of solid rocket motor propellant produces turbulent media containing gases with a velocity more than 1000 m/s, temperature and pressure more than 3000°C and 10 MPa, respectively,which destroys all metallic alloys. Elastomeric nanocomposite heat insulators are more attractive subjects in comparison to their non-elastomeric counterparts, due to their excellent thermal stresses and larger deformation bearing capacity. Nitrile rubber with high thermal properties is a proper candidate in such applications. Development in ablation performance of these heat shields is considered as an important challenge nowadays. A few works have been recently carried out using organoclay to enhancethe ablation and mechanical properties of heat insulators. In this work, an elastomeric heat insulator with superior ablative and mechanical properties was presented using nanotechnology. The results showed that an elastomeric nanocomposite heat insulator containing 15 wt% organoclay exhibits superior characteristics compared to its composite counterpart such as: 46% more tensile strength, 60% more elongationat-break, 1.7 times higher modulus (at 100% strain, 62% higher “insulating index number” and 36% lower mass ablation and erosion rates under a standard test with a heat flux of 2500 kW/m2 for 15 s.

Thyroid tissue: US-guided percutaneous laser thermal ablation.

Science.gov (United States)

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

2004-07-01

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

Abdominal cavity balloon for preventing a patient's bleeding

OpenAIRE

Naber, E.E.H.; Rutten, H.J.T.; Jakimowicz, J.J.; Goossens, R.H.M.; Moes, C.C.M.; Buzink, S.N.

2007-01-01

The invention relates to an abdominal cavity balloon for preventing a haemorrhage in a patient's pelvic region, comprising an inflatable balloon, wherein the balloon is pro vided with a smooth surface and with a strip that is flex- urally stiff and formed to follow the balloon's shape for po sitioning the balloon.

Calculating Payload for a Tethered Balloon System

Science.gov (United States)

Charles D. Tangren

1980-01-01

A graph method to calculate payload for a tethered balloon system, with the supporting helium lift and payload equations. is described. The balloon system is designed to collect emissions data during the convective-lift and no-convective-lift phases of a forest fire. A description of the balloon system and a list of factors affecting balloon selection are included....

Thermochemical ablation therapy of VX2 tumor using a permeable oil-packed liquid alkali metal.

Directory of Open Access Journals (Sweden)

Ziyi Guo

Full Text Available Alkali metal appears to be a promising tool in thermochemical ablation, but, it requires additional data on safety is required. The objective of this study was to explore the effectiveness of permeable oil-packed liquid alkali metal in the thermochemical ablation of tumors.Permeable oil-packed sodium-potassium (NaK was prepared using ultrasonic mixing of different ratios of metal to oil. The thermal effect of the mixture during ablation of muscle tissue ex vivo was evaluated using the Fluke Ti400 Thermal Imager. The thermochemical effect of the NaK-oil mixture on VX2 tumors was evaluated by performing perfusion CT scans both before and after treatment in 10 VX2 rabbit model tumors. VX2 tumors were harvested from two rabbits immediately after treatment to assess their viability using trypan blue and hematoxylin and eosin (H.E. staining.The injection of the NaK-oil mixture resulted in significantly higher heat in the ablation areas. The permeable oil controlled the rate of heat released during the NaK reaction with water in the living tissue. Perfusion computed tomography and its parameter map confirmed that the NaK-oil mixture had curative effects on VX2 tumors. Both trypan blue and H.E. staining showed partial necrosis of the VX2 tumors.The NaK-oil mixture may be used successfully to ablate tumor tissue in vivo. With reference to the controlled thermal and chemical lethal injury to tumors, using a liquid alkali in ablation is potentially an effective and safe method to treat malignant tumors.

Radiofrequency ablation of neuroendocrine liver metastases: the Middlesex experience.

Science.gov (United States)

Gillams, A; Cassoni, A; Conway, G; Lees, W

2005-01-01

Current treatment options for neuroendocrine liver metastases are not widely applicable or not that effective. Image-guided thermal ablation offers the possibility of a minimally invasive, albeit palliative, treatment that decreases tumor volume, preserves most of the normal liver, and can be repeated several times. We report our experience with image-guided thermal ablation in 25 patients with unresectable liver metastases. Since 1990 we have treated 189 tumors at 66 treatment sessions in 25 patients (12 female, 13 male; median age, 56 years; age range, 26--78 years). Thirty treatments were performed with a solid-state laser, and 36 treatments were performed with radiofrequency ablation. All but one treatment was performed percutaneously under image guidance. Sixteen patients had metastases from carcinoid primaries, three from gastrinoma, two from insulinoma, and four from miscellaneous causes. Fourteen of 25 had symptoms from hormone secretion. Imaging follow-up was available in 19 patients at a median of 21 months (range, 4--75 months). There was a complete response in six patients, a partial response in seven, and stable disease in one; hence, tumor load was controlled in 14 of 19 patients (74%). Relief of hormone-related symptoms was achieved in nine of 14 patients (69%). The median survival period from the diagnosis of liver metastases was 53 months. One patient with end-stage cardiac disease died after a carcinoid crisis. There were eight (12%) complications: five local and three distant, four major and four minor. As a minimally invasive, readily repeatable procedure that can be used to ablate small tumors, preferably before patients become severely symptomatic, radiofrequency ablation can provide effective control of liver tumor volume in most patients over many years.

Use of radiofrequency ablation in benign thyroid nodules: a literature review and updates.

Science.gov (United States)

Wong, Kai-Pun; Lang, Brian Hung-Hin

2013-01-01

Successful thermal ablation using radiofrequency has been reported in various tumors including liver or kidney tumors. Nonsurgical minimally invasive ablative therapy such as radiofrequency ablation (RFA) has been reported to be a safe and efficient treatment option in managing symptomatic cold thyroid nodules or hyperfunctioning thyroid nodules. Pressure and cosmetic symptoms have been shown to be significantly improved both in the short and long terms after RFA. For hyperfunctioning thyroid nodules, RFA is indicated for whom surgery or radioiodine are not indicated or ineffective or for those who refuse surgery or radio-iodine. Improvement of thyroid function with decreased need for antithyroid medications has been reported. Complication rate is relatively low. By reviewing the current literature, we reported its efficacy and complications and compared the efficacy of RFA relative to other ablative options such as ethanol ablation and laser ablation.

Use of Radiofrequency Ablation in Benign Thyroid Nodules: A Literature Review and Updates

Directory of Open Access Journals (Sweden)

Kai-Pun Wong

2013-01-01

Full Text Available Successful thermal ablation using radiofrequency has been reported in various tumors including liver or kidney tumors. Nonsurgical minimally invasive ablative therapy such as radiofrequency ablation (RFA has been reported to be a safe and efficient treatment option in managing symptomatic cold thyroid nodules or hyperfunctioning thyroid nodules. Pressure and cosmetic symptoms have been shown to be significantly improved both in the short and long terms after RFA. For hyperfunctioning thyroid nodules, RFA is indicated for whom surgery or radioiodine are not indicated or ineffective or for those who refuse surgery or radio-iodine. Improvement of thyroid function with decreased need for antithyroid medications has been reported. Complication rate is relatively low. By reviewing the current literature, we reported its efficacy and complications and compared the efficacy of RFA relative to other ablative options such as ethanol ablation and laser ablation.

Laser thermal ablation of multidrug-resistant bacteria using functionalized gold nanoparticles

Directory of Open Access Journals (Sweden)

Mocan L

2017-03-01

Full Text Available Lucian Mocan,1,2 Flaviu A Tabaran,3 Teodora Mocan,2,4 Teodora Pop,5 Ofelia Mosteanu,5 Lucia Agoston-Coldea,6 Cristian T Matea,2 Diana Gonciar,2 Claudiu Zdrehus,1,2 Cornel Iancu1 13rd Department of General Surgery, “Iuliu Hatieganu” University of Medicine and Pharmacy, 2Department of Nanomedicine, “Octavian Fodor” Gastroenterology Institute, 3Department of Pathology, University of Agricultural Sciences and Veterinary Medicine, Faculty of Veterinary Medicine, 4Department of Physiology, 53rd Gastroenterology Department, 6Department of Internal Medicine, “Iuliu Hatieganu” University of Medicine and Pharmacy, Cluj-Napoca, Romania Abstract: The issue of multidrug resistance (MDR has become an increasing threat to public health. One alternative strategy against MDR bacteria would be to construct therapeutic vectors capable of physically damaging these microorganisms. Gold nanoparticles hold great promise for the development of such therapeutic agents, since the nanoparticles exhibit impressive properties, of which the most important is the ability to convert light into heat. This property has scientific significance since is exploited to develop nano-photothermal vectors to destroy bacteria at a molecular level. The present paper summarizes the latest advancements in the field of nanotargeted laser hyperthermia of MDR bacteria mediated by gold nanoparticles. Keywords: bacteria, photo-thermal ablation, gold nanoparticles, antibiotic resistance

Critical appraisal of paclitaxel balloon angioplasty for femoral–popliteal arterial disease

Directory of Open Access Journals (Sweden)

Herten M

2016-08-01

Full Text Available Monika Herten,1 Giovanni B Torsello,1,2 Eva Schönefeld,3 Stefan Stahlhoff2 1Department of Vascular and Endovascular Surgery, University Hospital Münster, 2Department of Vascular Surgery, St Franziskus Hospital, Münster, 3Institute for Education and Student Affairs, University Hospital Münster, Münster, Germany Abstract: Peripheral arterial disease, particularly critical limb ischemia, is an area with urgent need for optimized therapies because, to date, vascular interventions often have limited life spans. In spite of initial encouraging technical success after femoropopliteal percutaneous transluminal angioplasty or stenting, postprocedural restenosis remains the major problem. The challenging idea behind the drug-coated balloon (DCB concept is the biological modification of the injury response after balloon dilatation. Antiproliferative drugs administered via DCBs or drug-eluting stents are able to suppress neointimal hyperplasia, the main cause of restenosis. This article reviews the results of DCB treatments of femoropopliteal and infrapopliteal lesions in comparison to standard angioplasty with uncoated balloons. A systematic literature search was performed in 1 medical journals (ie, MEDLINE, 2 international registers for clinical studies (ie, www.clinicaltrials.gov, and 3 abstracts of scientific sessions. Several controlled randomized trials with follow-up periods of up to 5 years demonstrated the efficacy of paclitaxel –DCB technology. However, calcified lesions seem to affect the efficacy of DCB. Combinations of preconditioning methods with DCBs showed promising results. Although the mechanical abrasion of calcium via atherectomy or laser ablation showed favorable periprocedural results, the long-term impact on restenosis and clinical outcome has to be demonstrated. Major advantages of the DCBs are the rapid delivery of drug at uniform concentrations with a single dose, their efficacy in areas wherein stents have been

No-touch radiofrequency ablation: A comparison of switching bipolar and switching monopolar ablation in Ex Vivo bovine liver

International Nuclear Information System (INIS)

Chang, Won; Lee, Jeong Min; Lee, Sang Min; Hank, Joon Koo

2017-01-01

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. 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. 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. 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

No-touch radiofrequency ablation: A comparison of switching bipolar and switching monopolar ablation in Ex Vivo bovine liver

Energy Technology Data Exchange (ETDEWEB)

Chang, Won; Lee, Jeong Min; Lee, Sang Min; Hank, Joon Koo [Dept. of Radiology, Seoul National University Hospital, Seoul (Korea, Republic of)

2017-04-15

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. 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. 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. 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.

Radiofrequency ablation of pancreas and optimal cooling of peripancreatic tissue in an ex-vivo porcine model

Directory of Open Access Journals (Sweden)

Michal Crha

2011-01-01

Full Text Available Radiofrequency ablation is a possible palliative treatment for patients suffering from pancreatic neoplasia. However, radiofrequency-induced damage to the peripancreatic tissues during pancreatic ablation might cause fatal complications. The aim of this experimental ex vivo study on pigs was to verify ablation protocols and evaluate whether or not the cooling of peripancereatic tissues during pancreatic ablation has any benefit for their protection against thermal injury. Radiofrequency ablation was performed on 52 pancreatic specimens obtained from pigs. During each pancreatic ablation, continuous measurements of the temperature in the portal vein and duodenal lumen were performed. Peripancreatic tissues were either not cooled or were cooled by being submerged in 14 °C water, or by a perfusion of the portal vein and duodenum with 14 °C saline. The effects of variation in target temperature of the ablated area (90 °C and 100 °C, duration of ablation (5 and 10 min and the effect of peripancreatic tissues cooling were studied. We proved that optimal radiofrequency ablation of the porcine pancreas can be reached with the temperature of 90  °C for 5 min in the ablated area. The perfusion of the duodenal and portal vein by 14 °C saline was found to be the most effective cooling method for minimizing damage to the walls. Continuous measurement of temperatures in peripancreatic tissues will provide useful feedback to assist in their protection against thermal injury. This therapy could be used in the treatment of pancreatic tumours.

Research of electrosurgical unit with novel antiadhesion composite thin film for tumor ablation: Microstructural characteristics, thermal conduction properties, and biological behaviors.

Science.gov (United States)

Shen, Yun-Dun; Lin, Li-Hsiang; Chiang, Hsi-Jen; Ou, Keng-Liang; Cheng, Han-Yi

2016-01-01

The objective of this study was to use surface functionalization to evaluate the antiadhesion property and thermal injury effects on the liver when using a novel electrosurgical unit with nanostructured-doped diamond-like carbon (DLC-Cu) thin films for tumor ablations. The physical and chemical properties of DLC-Cu thin films were characterized by contact angle goniometer, scanning electron microscope, and transmission electron microscope. Three-dimensional (3D) hepatic models were reconstructed using magnetic resonance imaging to simulate a clinical electrosurgical operation. The results indicated a significant increase of the contact angle on the nanostructured DLC-Cu thin films, and the antiadhesion properties were also observed in an animal model. Furthermore, the surgical temperature in the DLC-Cu electrosurgical unit was found to be significantly lower than the untreated unit when analyzed using 3D models and thermal images. In addition, DLC-Cu electrodes caused a relatively small injury area and lateral thermal effect. The results indicated that the nanostructured DLC-Cu thin film coating reduced excessive thermal injury and tissue adherence effect in the liver. © 2015 Wiley Periodicals, Inc.

Scientific ballooning. Proceedings of the symposium on the scientific use of balloons and related technical problems, Innsbruck, Austria, May 29-June 10, 1978

Energy Technology Data Exchange (ETDEWEB)

Riedler, W

1979-01-01

The book includes works on operational and technical aspects of balloon launching I and II, cooperative balloon campaigns, and new developments in scientific use of balloons. The specific topics discussed are coordinated balloon and rocket measurements of stratospheric wind shears and turbulence, ballooning in Japan and India, magnetospheric processes investigated with data taken from balloon flights, and remote sensing of middle atmosphere winds from balloon platforms.

In vitro analysis of balloon cuffing phenomenon: inherent biophysical properties of catheter material or mechanics of catheter balloon deflation?

Science.gov (United States)

Chung, Eric; So, Karina

2012-06-01

To investigates the different methods of balloon deflation, types of urinary catheters and exposure to urine media in catheter balloon cuffing. Bardex®, Bard-Lubri-Sil®, Argyle®, Releen® and Biocath® were tested in sterile and E.Coli inoculated urine at 0, 14 and 28 days. Catheter deflation was performed with active deflation; passive deflation; passive auto-deflation; and excision of the balloon inflow channel. Balloon cuffing was assessed objectively by running the deflated balloon over a plate of agar and subjectively by 3 independent observers. Bardex®, Argyle® and Biocath® showed greater degree of catheter balloon cuffing (p deflation was the worst method (p 0.05). Linear regression model analysis confirmed time as the most significant factor. The duration of catheters exposure, different deflation methods and types of catheters tested contributed significantly to catheter balloon cuffing (p < 0.01).

Flight Qualification of the NASA's Super Pressure Balloon

Science.gov (United States)

Cathey, Henry; Said, Magdi; Fairbrother, Debora

Designs of new balloons to support space science require a number of actual flights under various flight conditions to qualify them to as standard balloon flight offerings to the science community. Development of the new Super Pressure Balloon for the National Aeronautics and Space Administration’s Balloon Program Office has entailed employing new design, analysis, and production techniques to advance the state of the art. Some of these advances have been evolutionary steps and some have been revolutionary steps requiring a maturing understanding of the materials, designs, and manufacturing approaches. The NASA Super Pressure Balloon development end goal is to produce a flight vehicle that is qualified to carry a ton of science instrumentation, at an altitude greater than 33 km while maintaining a near constant pressure altitude for extended periods of up to 100 days, and at any latitude on the globe. The NASA’s Balloon Program Office has pursued this development in a carefully executed incremental approach by gradually increasing payload carrying capability and increasing balloon volume to reach these end goal. A very successful test flight of a ~200,700 m3 balloon was launch in late 2008 from Antarctica. This balloon flew for over 54 days at a constant altitude and circled the Antarctic continent almost three times. A larger balloon was flown from Antarctica in early 2011. This ~422,400 m3 flew at a constant altitude for 22 days making one circuit around Antarctica. Although the performance was nominal, the flight was terminated via command to recover high valued assets from the payload. The balloon designed to reach the program goals is a ~532,200 m3 pumpkin shaped Super Pressure Balloon. A test flight of this balloon was launched from the Swedish Space Corporation’s Esrange Balloon Launch Facilities near Kiruna, Sweden on 14 August, 2012. This flight was another success for this development program. Valuable information was gained from this short test

Esophageal achalasia : results of balloon dilation

Energy Technology Data Exchange (ETDEWEB)

Ki, Won Woo; Kang, Sung Gwon; Yoon, Kwon Ha; Kim, Nam Hyeon; Lee, Hyo Jeong; Yoon, Hyun Ki; Sung, Kyu Bo; Song, Ho Young [Ulsan Univ. College of Medicine, Seoul (Korea, Republic of)

1996-08-01

To evaluate the clinical effectiveness of fluoroscopically guided balloon dilation in the treatment of esophageal achalasia. Under fluoroscopic guidance, 21 balloon dilation procedures were performed in 14 patients with achalasia. A balloon with a diameter of 20 mm was used for the initial attempt.If the patient tolerated this well, the procedure was repeated with a 10-20 mm balloon, placed alongside at the same session. If, however the patient complained of severe chest pain and/or a postprocedural esophagogram showed an improvement,the additional balloon was not used. For patients whose results were unsatisfactory, the dilation procedure was repeated at sessions three to seven days apart. Succesful dilation was achieved in 13 of 14 patients(92.9%), who needed a total of 20 sessions of balloon dilation, ranging from one to three sessions per patient(mean, 1.54 sessions). Esophageal rupture occured in one of 14 patients(7.1%) ; of the 13 patients who underwent a successful dilation procedure, 12(92.3%) were free of recurrent symptoms during the follow-up period of 1-56(mean, 18.5) months. The remaning patient(7.7%) had a recurrence seven months after dilation. Fluoroscopically guided balloon dilation seems to be safe and effective in the treatment of esophageal achalasia.

Esophageal achalasia : results of balloon dilation

International Nuclear Information System (INIS)

Ki, Won Woo; Kang, Sung Gwon; Yoon, Kwon Ha; Kim, Nam Hyeon; Lee, Hyo Jeong; Yoon, Hyun Ki; Sung, Kyu Bo; Song, Ho Young

1996-01-01

To evaluate the clinical effectiveness of fluoroscopically guided balloon dilation in the treatment of esophageal achalasia. Under fluoroscopic guidance, 21 balloon dilation procedures were performed in 14 patients with achalasia. A balloon with a diameter of 20 mm was used for the initial attempt.If the patient tolerated this well, the procedure was repeated with a 10-20 mm balloon, placed alongside at the same session. If, however the patient complained of severe chest pain and/or a postprocedural esophagogram showed an improvement,the additional balloon was not used. For patients whose results were unsatisfactory, the dilation procedure was repeated at sessions three to seven days apart. Succesful dilation was achieved in 13 of 14 patients(92.9%), who needed a total of 20 sessions of balloon dilation, ranging from one to three sessions per patient(mean, 1.54 sessions). Esophageal rupture occured in one of 14 patients(7.1%) ; of the 13 patients who underwent a successful dilation procedure, 12(92.3%) were free of recurrent symptoms during the follow-up period of 1-56(mean, 18.5) months. The remaning patient(7.7%) had a recurrence seven months after dilation. Fluoroscopically guided balloon dilation seems to be safe and effective in the treatment of esophageal achalasia

Wall ablation of heated compound-materials into non-equilibrium discharge plasmas

Science.gov (United States)

Wang, Weizong; Kong, Linghan; Geng, Jinyue; Wei, Fuzhi; Xia, Guangqing

2017-02-01

The discharge properties of the plasma bulk flow near the surface of heated compound-materials strongly affects the kinetic layer parameters modeled and manifested in the Knudsen layer. This paper extends the widely used two-layer kinetic ablation model to the ablation controlled non-equilibrium discharge due to the fact that the local thermodynamic equilibrium (LTE) approximation is often violated as a result of the interaction between the plasma and solid walls. Modifications to the governing set of equations, to account for this effect, are derived and presented by assuming that the temperature of the electrons deviates from that of the heavy particles. The ablation characteristics of one typical material, polytetrafluoroethylene (PTFE) are calculated with this improved model. The internal degrees of freedom as well as the average particle mass and specific heat ratio of the polyatomic vapor, which strongly depends on the temperature, pressure and plasma non-equilibrium degree and plays a crucial role in the accurate determination of the ablation behavior by this model, are also taken into account. Our assessment showed the significance of including such modifications related to the non-equilibrium effect in the study of vaporization of heated compound materials in ablation controlled arcs. Additionally, a two-temperature magneto-hydrodynamic (MHD) model accounting for the thermal non-equilibrium occurring near the wall surface is developed and applied into an ablation-dominated discharge for an electro-thermal chemical launch device. Special attention is paid to the interaction between the non-equilibrium plasma and the solid propellant surface. Both the mass exchange process caused by the wall ablation and plasma species deposition as well as the associated momentum and energy exchange processes are taken into account. A detailed comparison of the results of the non-equilibrium model with those of an equilibrium model is presented. The non-equilibrium results

Early Cosmic Ray Research with Balloons

Energy Technology Data Exchange (ETDEWEB)

Walter, Michael, E-mail: michael.walter@desy.de

2013-06-15

The discovery of cosmic rays by Victor Hess during a balloon flight in 1912 at an altitude of 5350 m would not have been possible without the more than one hundred years development of scientific ballooning. The discovery of hot air and hydrogen balloons and their first flights in Europe is shortly described. Scientific ballooning was mainly connected with activities of meteorologists. It was also the geologist and meteorologist Franz Linke, who probably observed first indications of a penetrating radiation whose intensity seemed to increase with the altitude. Karl Bergwitz and Albert Gockel were the first physicists studying the penetrating radiation during balloon flights. The main part of the article deals with the discovery of the extraterrestrial radiation by V. Hess and the confirmation by Werner Kolhörster.

Early Cosmic Ray Research with Balloons

Science.gov (United States)

Walter, Michael

2013-06-01

The discovery of cosmic rays by Victor Hess during a balloon flight in 1912 at an altitude of 5350 m would not have been possible without the more than one hundred years development of scientific ballooning. The discovery of hot air and hydrogen balloons and their first flights in Europe is shortly described. Scientific ballooning was mainly connected with activities of meteorologists. It was also the geologist and meteorologist Franz Linke, who probably observed first indications of a penetrating radiation whose intensity seemed to increase with the altitude. Karl Bergwitz and Albert Gockel were the first physicists studying the penetrating radiation during balloon flights. The main part of the article deals with the discovery of the extraterrestrial radiation by V. Hess and the confirmation by Werner Kolhörster.

Early Cosmic Ray Research with Balloons

International Nuclear Information System (INIS)

Walter, Michael

2013-01-01

The discovery of cosmic rays by Victor Hess during a balloon flight in 1912 at an altitude of 5350 m would not have been possible without the more than one hundred years development of scientific ballooning. The discovery of hot air and hydrogen balloons and their first flights in Europe is shortly described. Scientific ballooning was mainly connected with activities of meteorologists. It was also the geologist and meteorologist Franz Linke, who probably observed first indications of a penetrating radiation whose intensity seemed to increase with the altitude. Karl Bergwitz and Albert Gockel were the first physicists studying the penetrating radiation during balloon flights. The main part of the article deals with the discovery of the extraterrestrial radiation by V. Hess and the confirmation by Werner Kolhörster

Temporal dependence of the mass ablation rate in uv irradiated spherical targets

International Nuclear Information System (INIS)

Delettrez, J.; Jaanimagi, P.A.; Henke, B.L.; Richardson, M.C.

1985-01-01

In this talk, measurements of thermal transport in spherical geometry using time-resolved x-ray spectroscopy are presented. The time dependence of the mass ablation rate (m) is determined by following the progress of the ablation surface through thin layers of material embedded at various depths below the surface of the target. These measurements made with 6, 12 and 24 uv (351 nm) beams from OMEGA are compared to previous thermal transport data and are in qualitative agreement with detailed LILAC hydrodynamic code simulations which predict a sharp decrease in m after the peak of the laser pulse. Viewgraphs of the talk comprise the report

High-Fidelity Modeling of Ablation and Coupled CFD-Material Response

Data.gov (United States)

National Aeronautics and Space Administration — This research proposal seeks to improve the state of the art in the modeling and simulation of ablating thermal protection systems (TPS). It will accomplish the...

Interstitial ultrasound ablation of tumors within or adjacent to bone: Contributions of preferential heating at the bone surface

Science.gov (United States)

Scott, Serena J.; Prakash, Punit; Salgaonkar, Vasant; Jones, Peter D.; Cam, Richard N.; Han, Misung; Rieke, Viola; Burdette, E. Clif; Diederich, Chris J.

2013-02-01

Preferential heating of bone due to high ultrasound attenuation may enhance thermal ablation performed with cathetercooled interstitial ultrasound applicators in or near bone. At the same time, thermally and acoustically insulating cortical bone may protect sensitive structures nearby. 3D acoustic and biothermal transient finite element models were developed to simulate temperature and thermal dose distributions during catheter-cooled interstitial ultrasound ablation near bone. Experiments in ex vivo tissues and tissue-mimicking phantoms were performed to validate the models and to quantify the temperature profiles and ablated volumes for various distances between the interstitial applicator and the bone surface. 3D patient-specific models selected to bracket the range of clinical usage were developed to investigate what types of tumors could be treated, applicator configurations, insertion paths, safety margins, and other parameters. Experiments show that preferential heating at the bone surface decreases treatment times compared to when bone is absent and that all tissue between an applicator and bone can be ablated when they are up to 2 cm apart. Simulations indicate that a 5-7 mm safety margin of normal bone is needed to protect (thermal dose tumors 1.0-3.8 cm (L) and 1.3-3.0 cm (D) near or within bone were ablated (thermal dose > 240 CEM43°C) within 10 min without damaging the nearby spinal cord, lungs, esophagus, trachea, or major vasculature. Preferential absorption of ultrasound by bone may provide improved localization, faster treatment times, and larger treatment zones in tumors in and near bone compared to other heating modalities.

Ultraviolet-laser ablation of skin

Energy Technology Data Exchange (ETDEWEB)

Lane, R.J.; Linsker, R.; Wynne, J.J.; Torres, A.; Geronemus, R.G.

1985-05-01

The authors report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding began. The 248-nm radiation, however, continued to remove tissue despite bleeding and left a clean incision with only minimal thermal damage. The krypton-fluoride excimer laser beam at 248 nm, which should be deliverable through a quartz optical fiber, has great potential as a surgical instrument.

Statistical approach of weakly nonlinear ablative Rayleigh-Taylor instability

International Nuclear Information System (INIS)

Garnier, J.; Masse, L.

2005-01-01

A weakly nonlinear model is proposed for the Rayleigh-Taylor instability in presence of ablation and thermal transport. The nonlinear effects for a single-mode disturbance are computed, included the nonlinear correction to the exponential growth of the fundamental modulation. Mode coupling in the spectrum of a multimode disturbance is thoroughly analyzed by a statistical approach. The exponential growth of the linear regime is shown to be reduced by the nonlinear mode coupling. The saturation amplitude is around 0.1λ for long wavelengths, but higher for short instable wavelengths in the ablative regime

Effect of intra-aortic balloon pump on coronary blood flow during different balloon cycles support: A computer study.

Science.gov (United States)

Aye, Thin Pa Pa; Htet, Zwe Lin; Singhavilai, Thamvarit; Naiyanetr, Phornphop

2015-01-01

Intra-aortic balloon pump (IABP) has been used in clinical treatment as a mechanical circulatory support device for patients with heart failure. A computer model is used to study the effect on coronary blood flow (CBF) with different balloon cycles under both normal and pathological conditions. The model of cardiovascular and IABP is developed by using MATLAB SIMULINK. The effect on coronary blood flow has been studied under both normal and pathological conditions using different balloon cycles (balloon off; 1:4; 1:2; 1:1). A pathological heart is implemented by reducing the left ventricular contractility. The result of this study shows that the rate of balloon cycles is related to the level of coronary blood flow.

NASA balloon design and flight - Philosophy and criteria

Science.gov (United States)

Smith, I. S., Jr.

1993-01-01

The NASA philosophy and criteria for the design and flight of scientific balloons are set forth and discussed. The thickness of balloon films is standardized at 20.3 microns to isolate potential film problems, and design equations are given for specific balloon parameters. Expressions are given for: flight-stress index, total required thickness, cap length, load-tape rating, and venting-duct area. The balloon design criteria were used in the design of scientific balloons under NASA auspices since 1986, and the resulting designs are shown to be 95 percent effective. These results represent a significant increase in the effectiveness of the balloons and therefore indicate that the design criteria are valuable. The criteria are applicable to four balloon volume classes in combination with seven payload ranges.

Percutaneous treatment of extrahepatic bile duct stones assisted by balloon sphincteroplasty and occlusion balloon

Energy Technology Data Exchange (ETDEWEB)

Park, Yong Sung; Kim, Ji Hyung; Choi, Young Woo; Lee, Tae Hee; Hwang, Cheol Mog; Cho, Young Jun; Kim, Keum Won [Konyang University Hospital, Daejeon (Korea, Republic of)

2005-12-15

To describe the technical feasibility and usefulness of extrahepatic biliary stone removal by balloon sphincteroplasty and occlusion balloon pushing. Fifteen patients with extrahepatic bile duct stones were included in this study. Endoscopic stone removal was not successful in 13 patients, and two patients refused the procedure due to endoscopy phobia. At first, all patients underwent percutaneous transhepatic biliary drainage (PTBD). A few days later, through the PTBD route, balloon assisted dilatation for common bile duct (CBD) sphincter was performed, and then the stones were pushed into the duodenum using an 11.5 mm occlusion balloon. Success rate, reason for failure, and complications associated with the procedure were evaluated. Eight patients had one stone, five patients had two stones, and two patients had more than five stones. The procedure was successful in 13 patients (13/15). In 12 of the patients, all stones were removed in the first trial. In one patients, residual stones were discovered on follow-up cholangiography, and were subsequently removed in the second trial. Technical failure occurred in two patients. Both of these patients had severely dilated CBD and multiple stones with various sizes. Ten patients complained of pain in the right upper quadrant and epigastrium of the abdomen immediately following the procedure, but there were no significant procedure-related complications such as bleeding or pancreatitis. Percutaneous extrahepatic biliary stone removal by balloon sphincteroplasty and subsequent stone pushing with occlusion balloon is an effective, safe, and technically feasible procedure which can be used as an alternative method in patients when endoscopic extrahepatic biliary stone removal was not successful.

Percutaneous treatment of extrahepatic bile duct stones assisted by balloon sphincteroplasty and occlusion balloon

International Nuclear Information System (INIS)

Park, Yong Sung; Kim, Ji Hyung; Choi, Young Woo; Lee, Tae Hee; Hwang, Cheol Mog; Cho, Young Jun; Kim, Keum Won

2005-01-01

To describe the technical feasibility and usefulness of extrahepatic biliary stone removal by balloon sphincteroplasty and occlusion balloon pushing. Fifteen patients with extrahepatic bile duct stones were included in this study. Endoscopic stone removal was not successful in 13 patients, and two patients refused the procedure due to endoscopy phobia. At first, all patients underwent percutaneous transhepatic biliary drainage (PTBD). A few days later, through the PTBD route, balloon assisted dilatation for common bile duct (CBD) sphincter was performed, and then the stones were pushed into the duodenum using an 11.5 mm occlusion balloon. Success rate, reason for failure, and complications associated with the procedure were evaluated. Eight patients had one stone, five patients had two stones, and two patients had more than five stones. The procedure was successful in 13 patients (13/15). In 12 of the patients, all stones were removed in the first trial. In one patients, residual stones were discovered on follow-up cholangiography, and were subsequently removed in the second trial. Technical failure occurred in two patients. Both of these patients had severely dilated CBD and multiple stones with various sizes. Ten patients complained of pain in the right upper quadrant and epigastrium of the abdomen immediately following the procedure, but there were no significant procedure-related complications such as bleeding or pancreatitis. Percutaneous extrahepatic biliary stone removal by balloon sphincteroplasty and subsequent stone pushing with occlusion balloon is an effective, safe, and technically feasible procedure which can be used as an alternative method in patients when endoscopic extrahepatic biliary stone removal was not successful

Gondola development for CNES stratospheric balloons

Science.gov (United States)

Vargas, A.; Audoubert, J.; Cau, M.; Evrard, J.; Verdier, N.

The CNES has been supporting scientific ballooning since its establishment in 1962. The two main parts of the balloon system or aerostat are the balloon itself and the flight train, comprising the house-keeping gondola, for the control of balloon flight (localization and operational telemetry & telecommand - TM/TC), and the scientific gondola with its dedicated telecommunication system. For zero pressure balloon, the development of new TM/TC system for the housekeeping and science data transmission are going on from 1999. The main concepts are : - for balloon house-keeping and low rate scientific telemetry, the ELITE system, which is based on single I2C bus standardizing communication between the different components of the system : trajectography, balloon control, power supply, scientific TM/TC, .... In this concept, Radio Frequency links are developed between the house keeping gondola and the components of the aerostat (balloon valve, ballast machine, balloon gas temperature measurements, ...). The main objectives are to simplify the flight train preparation in term of gondola testing before flight, and also by reducing the number of long electrical cables integrated in the balloon and the flight train; - for high rate scientific telemetry, the use of functional interconnection Internet Protocol (IP) in interface with the Radio Frequency link. The main idea is to use off-the-shelf IP hardware products (routers, industrial PC, ...) and IP software (Telnet, FTP, Web-HTTP, ...) to reduce the development costs; - for safety increase, the adding, in the flight train, of a totally independent house keeping gondola based on the satellite Inmarsat M and Iridium telecommunication systems, which permits to get real time communications between the on-board data mobile and the ground station, reduced to a PC computer with modem connected to the phone network. These GEO and LEO telecommunication systems give also the capability to operate balloon flights over longer distance

Simultaneous stent expansion/balloon deflation technique to salvage failed balloon remodeling.

Science.gov (United States)

Ladner, Travis R; He, Lucy; Davis, Brandon J; Froehler, Michael T; Mocco, J

2016-04-01

Herniation, with possible embolization, of coils into the parent vessel following aneurysm coiling remains a frequent challenge. For this reason, balloon or stent assisted embolization remains an important technique. Despite the use of balloon remodeling, there are occasions where, on deflation of the balloon, some coils, or even the entire coil mass, may migrate. We report the successful use of a simultaneous adjacent stent deployment bailout technique in order to salvage coil prolapse during balloon remodeling in three patients. Case No 1 was a wide neck left internal carotid artery bifurcation aneurysm, measuring 9 mm×7.9 mm×6 mm with a 5 mm neck. Case No 2 was a complex left superior hypophyseal artery aneurysm, measuring 5.3 mm×4 mm×5 mm with a 2.9 mm neck. Case No 3 was a ruptured right posterior communicating artery aneurysm, measuring 4 mm×4 mm×4.5 mm with a 4 mm neck. This technique successfully returned the prolapsed coil mass into the aneurysm sac in all cases without procedural complications. The closed cell design of the Enterprise VRD (Codman and Shurtleff Inc, Raynham, Massachusetts, USA) makes it ideal for this bailout technique, by allowing the use of an 0.021 inch delivery catheter (necessary for simultaneous access) and by avoiding the possibility of an open cell strut getting caught on the deflated balloon. We hope this technique will prove useful to readers who may find themselves in a similar predicament. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Are drug-coated balloons cost effective for femoropopliteal occlusive disease? A comparison of bare metal stents and uncoated balloons.

Science.gov (United States)

Poder, Thomas G; Fisette, Jean-François

2016-07-01

To perform a cost-effectiveness analysis to help hospital decision-makers with regard to the use of drug-coated balloons compared with bare metal stents and uncoated balloons for femoropopliteal occlusive disease. Clinical outcomes were extracted from the results of meta-analyses already published, and cost units are those used in the Quebec healthcare network. The literature review was limited to the last four years to obtain the most recent data. The cost-effectiveness analysis was based on a 2-year perspective, and risk factors of reintervention were considered. The cost-effectiveness analysis indicated that drug-coated balloons were generally more efficient than bare metal stents, particularly for patients with higher risk of reintervention (up to CAD$1686 per patient TASC II C or D). Compared with uncoated balloons, results indicated that drug-coated balloons were more efficient if the reintervention rate associated with uncoated balloons is very high and for patients with higher risk of reintervention (up to CAD$3301 per patient). The higher a patient's risk of reintervention, the higher the savings associated with the use of a drug-coated balloon will be. For patients at lower risk, the uncoated balloon strategy is still recommended as a first choice for endovascular intervention.

Anderson localization and ballooning eigenfunctions

International Nuclear Information System (INIS)

Dewar, R.L.; Cuthbert, P.

1999-01-01

In solving the ballooning eigenvalue for a low-aspect-ratio stellarator equilibrium it is found that the quasiperiodic behaviour of the equilibrium quantities along a typical magnetic field line can lead to localization of the ballooning eigenfunction (Anderson localization) even in the limit of zero shear. This localization leads to strong field-line dependence of the ballooning eigenvalue, with different branches attaining their maximum growth rates on different field lines. A method is presented of estimating the field-line dependence of various eigenvalue branches by using toroidal and poloidal symmetry operations on the shear-free ballooning equation to generate an approximate set of eigenfunctions. These zero-shear predictions are compared with accurate numerical solutions for the H-1 Heliac and are shown to give a qualitatively correct picture, but finite shear corrections will be needed to give quantitative predictions

An investigation on 800 nm femtosecond laser ablation of K9 glass in air and vacuum

Energy Technology Data Exchange (ETDEWEB)

Xu, Shi-zhen, E-mail: xusz@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Yao, Cai-zhen [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Dou, Hong-qiang [Department of Material Science and Engineering, Sichuan Engineering Technical College, Deyang 618000 (China); Liao, Wei, E-mail: liaowei@caep.cn [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Li, Xiao-yang; Ding, Ren-jie [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Zhang, Li-juan; Liu, Hao; Yuan, Xiao-dong [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Zu, Xiao-tao [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2017-06-01

Highlights: • The fs laser ablation of borosilicate glass (K9) were investigated under 35 and 500 fs pulses. • At high fluence regime, the ablation rate at 35 fs in air increased to a plateau, and 500 fs in air and vacuum decreased. • The mechanisms of multiple-photon ionization and impact ionization were included. • The ablation morphologies of smooth zone and laser-induced periodic surface structures were presented and illustrated. • The ablation mechanisms of non-thermal and thermal ablation were included. - Abstract: Ablation rates of K9 glass were studied as a function of femtosecond laser fluences. The central wavelength was 800 nm, and pulse durations of 35 fs and 500 fs in air and vacuum were employed. Ablation thresholds of 0.42 J/cm{sup 2} and 2.1 J/cm{sup 2} were obtained at 35 fs and 500 fs, respectively, which were independent with the ambient conditions and depend on the incident pulse numbers due to incubation effects. The ablation rate of 35 fs pulse laser increased with the increasing of laser fluence in vacuum, while in air condition, it slowly increased to a plateau at high fluence. The ablation rate of 500 fs pulse laser showed an increase at low fluence and a slow drop of ablation rate was observed at high fluence in air and vacuum, which may due to the strong defocusing effects associated with the non-equilibrium ionization of air, and/or the shielding effects of conduction band electrons (CBEs) produced by multi-photon ionization and impact ionization in K9 glass surface. The typical ablation morphologies, e.g. smooth zone and laser-induced periodic surface structures (LIPSS) were also presented and illustrated.

Theoretical and experimental analysis of amplitude control ablation and bipolar ablation in creating linear lesion and discrete lesions for treating atrial fibrillation.

Science.gov (United States)

Yan, Shengjie; Wu, Xiaomei; Wang, Weiqi

2017-09-01

Radiofrequency (RF) energy is often used to create a linear lesion or discrete lesions for blocking the accessory conduction pathways for treating atrial fibrillation. By using finite element analysis, we study the ablation effect of amplitude control ablation mode (AcM) and bipolar ablation mode (BiM) in creating a linear lesion and discrete lesions in a 5-mm-thick atrial wall; particularly, the characteristic of lesion shape has been investigated in amplitude control ablation. Computer models of multipolar catheter were developed to study the lesion dimensions in atrial walls created through AcM, BiM and special electrodes activated ablation methods in AcM and BiM. To validate the theoretical results in this study, an in vitro experiment with porcine cardiac tissue was performed. At 40 V/20 V root mean squared (RMS) of the RF voltage for AcM, the continuous and transmural lesion was created by AcM-15s, AcM-5s and AcM-ad-20V ablation in 5-mm-thick atrial wall. At 20 V RMS for BiM, the continuous but not transmural lesion was created. AcM ablation yielded asymmetrical and discrete lesions shape, whereas the lesion shape turned to more symmetrical and continuous as the electrodes alternative activated period decreased from 15 s to 5 s. Two discrete lesions were created when using AcM, AcM-ad-40V, BiM-ad-20V and BiM-ad-40V. The experimental and computational thermal lesion shapes created in cardiac tissue were in agreement. Amplitude control ablation technology and bipolar ablation technology are feasible methods to create continuous lesion or discrete for pulmonary veins isolation.

Numerical Study for Optimizing Parameters of High-Intensity Focused Ultrasound-Induced Thermal Field during Liver Tumor Ablation: HIFU Simulator

Directory of Open Access Journals (Sweden)

Somayeh gharloghi

2017-03-01

Full Text Available Introduction High intensity focused ultrasound (HIFU is considered a noninvasive and effective technique for tumor ablation. Frequency and acoustic power are the most effective parameters for temperature distribution and the extent of tissue damage. The aim of this study was to optimize the operating transducer parameters such as frequency and input power in order to acquire suitable temperature and thermal dose distribution in the course of a numerical assessment. Materials and Methods To model the sound propagation, the Khokhlov-Zabolotskava-Kuznetsov (KZK nonlinear wave equation was used and simulation was carried out using MATLAB HIFU toolbox. Bioheat equation was applied to calculate the transient temperature in the liver tissue. Frequency ranges of 2, 3, 4, and 5 MHz and power levels of 50 and 100 W were applied using an extracorporeal transducer. Results Using a frequency of 2 MHz, the maximum temperatures reached 53°C and 90°C in the focal point for power levels of 50 W and 100 W, respectively. With the same powers and using a frequency of 3 MHz, the temperature reached to 71°C and 170°C, respectively. In addition, for these power levels at the frequency of 4 MHz, the temperature reached to 72°C and 145°C, respectively. However, at the 5 MHz frequency, the temperature in the focal spot was either 57°C or 79°C. Conclusion Use of frequency of 2 MHz and power of 100 W led to higher thermal dose distribution, and subsequently, reduction of the treatment duration and complications at the same exposure time in ablation of large tumors.

Numerical analysis of laser ablation using the axisymmetric two-temperature model

Science.gov (United States)

Dziatkiewicz, Jolanta; Majchrzak, Ewa

2018-01-01

Laser ablation of the axisymmetric micro-domain is analyzed. To describe the thermal processes occurring in the micro-domain the two-temperature hyperbolic model supplemented by the boundary and initial conditions is used. This model takes into account the phase changes of material (solid-liquid and liquid-vapour) and the ablation process. At the stage of numerical computations the finite difference method with staggered grid is used. In the final part the results of computations are shown.

Application of Electrocautery Needle Knife Combined with Balloon Dilatation versus Balloon Dilatation in the Treatment of Tracheal Fibrotic Scar Stenosis.

Science.gov (United States)

Bo, Liyan; Li, Congcong; Chen, Min; Mu, Deguang; Jin, Faguang

Electrocautery needle knives can largely reduce scar and granulation tissue hyperplasia and play an important role in treating patients with benign stricture. The aim of this retrospective study was to evaluate the efficacy and safety of electrocautery needle knife combined with balloon dilatation versus balloon dilatation alone in the treatment of tracheal stenosis caused by tracheal intubation or tracheotomy. We retrospectively analysed the clinical data of 43 patients with tracheal stenosis caused by tracheotomy or tracheal intubation in our department from January 2013 to January 2016. Among these 43 patients, 23 had simple web-like stenosis and 20 had complex steno sis. All patients were treated under general anaesthesia, and the treatment methods were (1) balloon dilatation alone, (2) needle knife excision of fibrotic tissue combined with balloon dilatation, and (3) needle knife radial incision of fibrotic tissue combined with balloon dilatation. After treatment the symptoms, such as shortness of breath, were markedly improved immediately in all cases. The stenosis degree of patients who were treated with the elec-trocautery needle knife combined with balloon dilatation had better improvement compared with that of those treated with balloon dilatation treatment alone after 3 months (0.45 ± 0.04 vs. 0.67 ± 0.05, p knife combined with balloon dilatation is an effective and safe treatment for tracheal fibrotic stenosis compared with balloon dilatation alone. © 2017 S. Karger AG, Basel.

Femtosecond laser ablation and cutting technology on PMP foam

International Nuclear Information System (INIS)

Song Chengwei; Li Guo; Huang Yanhua; Du Kai; Yang Liang

2013-01-01

The femtosecond laser ablation results of PMP foam (density of 90 mg/cm 3 ) were analyzed. The laser pulses used for the study were 800 nm in wavelength, 50 fs in pulse duration and the repetition rate was 1000 Hz. The ablation threshold of the foam was 0.91 J/cm 2 when it was shot by 100 laser pulses. The impacts of laser power, the pulse number and the numerical aperture of the focusing objective on the crater diameter were obtained. In the same femtosecond laser machining system, comparing with the ablation shape into copper foil, the important factor causing the irregular shape of the ablation region was verified that there were many different sizes and randomly distributed pores inside PMP foam. The carbonation phenomenon was observed on the edge of the ablated areas when the sample was ablated using high laser power or/and more laser pulses. Thermal effect was considered to be the causes of the carbonation. A new method based on coupling laser beam to cut thickness greater than 1 mm film-foam with femtosecond laser was proposed. Using this method, the femtosecond laser cutting thickness was greater than 1.5 mm, the angle between the cutting side wall and the laser beam optical axis might be less than 5°, and the cutting surface was clean. (authors)

Recent activities on the scientific ballooning in Japan

International Nuclear Information System (INIS)

Nisimura, J.; Hirosawa, H.

1984-01-01

Scientific ballooning is Japan has been organized by the Institute of Space and Astronautical Science, and about 15 balloons have been launched each year from Sanriku Balloon Center that belongs to this Institute. The balloon center is located in the northern part of Japan. The observations cover the field of X-ray, gamma-ray, infrared astronomy, cosmic rays, and atmospheric science. Systems of lon duration flights such as 'Boomerang Balloons', and fine attitude control systems were developed and widely applied to the scientific observations. International collaborative works were performed in Australia and Indonesia last year. Some details of these activities are reported and possible future collaborations with Braziian balloon group are also discussed. (Author) [pt

Development of Low Density, Flexible Carbon Phenolic Ablators

Science.gov (United States)

Stackpoole, Mairead; Thornton, Jeremy; Fan, Wendy; Covington, Alan; Doxtad, Evan; Beck, Robin; Gasch, Matt; Arnold, Jim

2012-01-01

Phenolic Impregnated Carbon Ablator (PICA) was the enabling TPS material for the Stardust mission where it was used as a single piece heatshield. PICA has the advantages of low density (approximately 0.27 grams per cubic centimeter) coupled with efficient ablative capability at high heat fluxes. Due to its brittle nature and low strain to failure recent efforts at NASA ARC have focused on alternative architectures to yield flexible and more conformal carbon phenolic materials with comparable densities to PICA. This presentation will discuss flexible alternatives to PICA and include preliminary mechanical and thermal properties as well as recent arc jet and LHMEL screening test results.

The French balloon and sounding rocket space program

Science.gov (United States)

Coutin/Faye, S.; Sadourny, I.

1987-08-01

Stratospheric and long duration flight balloon programs are outlined. Open stratospheric balloons up to 1 million cu m volume are used to carry astronomy, solar system, aeronomy, stratosphere, biology, space physics, and geophysics experiments. The long duration balloons can carry 50 kg payloads at 20 to 30 km altitude for 10 days to several weeks. Pressurized stratospheric balloons, and infrared hot air balloons are used. They are used to study the dynamics of stratospheric waves and atmospheric water vapor. Laboratories participating in sounding rocket programs are listed.

TMBM: Tethered Micro-Balloons on Mars

Science.gov (United States)

Sims, M. H.; Greeley, R.; Cutts, J. A.; Yavrouian, A. H.; Murbach, M.

2000-01-01

The use of balloons/aerobots on Mars has been under consideration for many years. Concepts include deployment during entry into the atmosphere from a carrier spacecraft, deployment from a lander, use of super-pressurized systems for long duration flights, 'hot-air' systems, etc. Principal advantages include the ability to obtain high-resolution data of the surface because balloons provide a low-altitude platform which moves relatively slowly. Work conducted within the last few years has removed many of the technical difficulties encountered in deployment and operation of balloons/aerobots on Mars. The concept proposed here (a tethered balloon released from a lander) uses a relatively simple approach which would enable aspects of Martian balloons to be tested while providing useful and potentially unique science results. Tethered Micro-Balloons on Mars (TMBM) would be carried to Mars on board a future lander as a stand-alone experiment having a total mass of one to two kilograms. It would consist of a helium balloon of up to 50 cubic meters that is inflated after landing and initially tethered to the lander. Its primary instrumentation would be a camera that would be carried to an altitude of up to tens of meters above the surface. Imaging data would be transmitted to the lander for inclusion in the mission data stream. The tether would be released in stages allowing different resolutions and coverage. In addition during this staged release a lander camera system may observe the motion of the balloon at various heights above he lander. Under some scenarios upon completion of the primary phase of TMBM operations, the tether would be cut, allowing TMBM to drift away from the landing site, during which images would be taken along the ground.

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

Directory of Open Access Journals (Sweden)

Chenguo Yao

Full Text Available 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.

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

Science.gov (United States)

Yao, Chenguo; Lv, Yanpeng; Dong, Shoulong; Zhao, Yajun; Liu, Hongmei

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.

Overview of the NASA balloon R&D program

Science.gov (United States)

Smith, I. Steve, Jr.

1994-01-01

The catastrophic balloon failure during the first half of the 1980's identified the need for a comprehensive and continuing balloon research and development (R&D) commitment by NASA. Technical understanding was lacking in many of the disciplines and processes associated with scientific ballooning. A comprehensive balloon R&D plan was developed in 1986 and implemented in 1987. The objectives were to develop the understanding of balloon system performance, limitations, and failure mechanisms. The program consisted of five major technical areas: structures, performance and analysis, materials, chemistry and processing, and quality control. Research activitites have been conducted at NASA/Goddard Space Flight Center (GSFC)-Wallops Flight Facility (WFF), other NASA centers and government facilities, universities, and the balloon manufacturers. Several new and increased capabilities and resources have resulted from this activity. The findings, capabilities, and plan of the balloon R&D program are presented.

Balloon pulmonary valvotomy – Not just a simple balloon dilatation

Directory of Open Access Journals (Sweden)

Subhendu Mohanty

2014-07-01

Full Text Available Balloon pulmonary valvotomy is the preferred mode of treatment in patients with isolated pulmonary valvar stenosis and has shown good long term results. It is generally considered a safe procedure with few complications. There have been however, case reports of potentially fatal acute severe pulmonary edema occurring after the procedure in some patients. The cause of this complication and its pathophysiology is still not clear. Its occurrence is also infrequent with less than 5 cases reported till now. We report a case of pulmonary valvar stenosis which developed acute severe refractory pulmonary edema immediately after balloon pulmonary valvotomy.

Effect of liquid properties on laser ablation of aluminum and titanium alloys

Energy Technology Data Exchange (ETDEWEB)

Ouyang, Peixuan, E-mail: oypx12@mails.tsinghua.edu.cn [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); Li, Peijie [National Center of Novel Materials for International Research, Tsinghua University, Beijing 100084 (China); State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Leksina, E.G.; Michurin, S.V. [Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow 119992 (Russian Federation); He, Liangju [School of Aerospace, Tsinghua University, Beijing 100084 (China)

2016-01-01

Graphical abstract: - Highlights: • Porous surfaces are formed in Al alloy after wet ablation due to phase explosion. • A higher ablation rate is produced in glycerin than that in water and isopropanol. • Effect of liquid properties on mass-removal mechanisms was discussed. • Phase explosion and plasma-induced pressure contribute greatly to mass removal. • Density, heat conductivity and shock impendence of liquid affect ablation rates. - Abstract: In order to study the effect of liquid properties on laser ablation in liquids, aluminum 5A06 and titanium TB5 targets were irradiated by single-pulse infrared laser in isopropanol, distilled water, glycerin and as a comparison, in air, respectively. Craters induced by laser ablation were characterized using scanning electron and white-light interferometric microscopies. The results show that for liquid-mediated ablation, craters with porous surface structures were formed in aluminum target through phase explosion, while no micro-cavities were formed in titanium target owing to high critical temperature of titanium. In addition, ablation rates of aluminum and titanium targets vary with types of ambient media in accordance with such sequence: air < isopropanol < water < glycerin. Further, the influence of liquid properties on material-removal mechanisms for laser ablation in liquid is discussed. It is concluded that the density, thermal conductivity and acoustical impedance of liquid play a dominant role in laser ablation efficiency.

Utilidade do Ultrassom intracardíaco no isolamento de veias pulmonares usando cateter-balão a laser Utilidad del ultrasonido intracardíaco en el aislamiento de venas pulmonares usando catéter-balón láser Utility of intracardiac ultrasound imaging to guide pulmonary vein ablation using laser balloon catheter

Directory of Open Access Journals (Sweden)

Luiz Leite

2009-12-01

. Se obtuvo el aislamiento completo en 38/59 (64%, y fue significantemente más común sin derrame: [30/38 (79% versus 8/23 (35%, pBACKGROUND: Pulmonary vein isolation (PVI with balloon catheter has been used as the endpoint for AF ablation. OBJECTIVE: To determine the usefulness of intracardiac ultrasound (ICUS to guide PVI using laser balloon catheter. METHODS: 59 PVs were ablated in 27 dogs. Doppler imaging was used to identify blood flow leaks between PV and balloon. After each energy delivery, the circular mapping catheter was repositioned to check if isolation had been achieved. The leak position was then correlated with the gap position at the pathological study. Multivariate logistic regression analysis was undertaken. RESULTS: 59 PV were ablated. Mean burn time was 279±177 sec, mean balloon diameter was 23±3 mm, and mean balloon length was 25±4 mm. Complete isolation was achieved in 38/59 (64% cases, and it was significantly more common when there was no leak: [30/38 (79% versus 8/23 (35%, p<0.001]. This occurred regardless of time of laser application (302±223 sec. vs. 266±148 sec., p=ns, laser power (3.5 W/cm, 4.5 W/cm, and 5.5 W/cm, balloon diameter (24± 3 mm vs. 22± 3 mm, p=ns and length (27±4 mm vs. 24±4mm, p=ns. The positive predictive value for predicting incomplete isolation was 65% and the negative predictive value was 83%. CONCLUSION: An identifiable leak between PV and the LBA device seen at the ICUS is predictive of lower PV isolation rates. ICUS may be useful for leak detection to avoid ineffective energy application during circumferential PV ablation. This could also be helpful when other types of energy are used.

Particle Astrophysics in NASA's Long Duration Balloon Program

International Nuclear Information System (INIS)

Gorham, Peter W.

2013-01-01

A century after Viktor Hess' discovery of cosmic rays, balloon flights still play a central role in the investigation of cosmic rays over nearly their entire spectrum. We report on the current status of NASA balloon program for particle astrophysics, with particular emphasis on the very successful Antarctic long-duration balloon program, and new developments in the progress toward ultra-long duration balloons

Laser welding of balloon catheters

Science.gov (United States)

Flanagan, Aidan J.

2003-03-01

The balloon catheter is one of the principal instruments of non-invasive vascular surgery. It is used most commonly for angioplasty (and in recent years for delivering stents) at a multitude of different sites in the body from small arteries in the heart to the bilary duct. It is composed of a polymer balloon that is attached to a polymer shaft at two points called the distal and proximal bonds. The diverse utility of balloon catheters means a large range of component sizes and materials are used during production; this leads to a complexity of bonding methods and technology. The proximal and distal bonds have been conventionally made using cyanoacrylate or UV curing glue, however with performance requirements of bond strength, flexibility, profile, and manufacturing costs these bonds are increasingly being made by welding using laser, RF, and Hot Jaw methods. This paper describes laser welding of distal and proximal balloon bonds and details beam delivery, bonding mechanisms, bond shaping, laser types, and wavelength choice.

NASA Langley Research Center tethered balloon systems

Science.gov (United States)

Owens, Thomas L.; Storey, Richard W.; Youngbluth, Otto

1987-01-01

The NASA Langley Research Center tethered balloon system operations are covered in this report for the period of 1979 through 1983. Meteorological data, ozone concentrations, and other data were obtained from in situ measurements. The large tethered balloon had a lifting capability of 30 kilograms to 2500 meters. The report includes descriptions of the various components of the balloon systems such as the balloons, the sensors, the electronics, and the hardware. Several photographs of the system are included as well as a list of projects including the types of data gathered.

Lesion size in relation to ablation site during radiofrequency ablation

DEFF Research Database (Denmark)

Petersen, H H; Chen, X; Pietersen, A

1998-01-01

This study was designed to investigate the effect of the convective cooling of the tip of the ablation electrode during temperature controlled radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ablation was perfor......This study was designed to investigate the effect of the convective cooling of the tip of the ablation electrode during temperature controlled radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ablation...... was performed during two different flow-velocities in a tissue bath, while electrode contact pressure and position were unchanged. Target temperature was 80 degrees C. Obtained tip temperature, power consumption and lesion dimensions were measured. In vivo lesion volume, depth and width were found significantly.......61 in vitro). We conclude that during temperature controlled radiofrequency ablation lesion size differs for septal and apical left ventricular applications. Differences in convective cooling might play an important role in this respect. This is supported by our in vitro experiments, where increased...

Cardiac ablation

Directory of Open Access Journals (Sweden)

Kelly Ratheal

2016-01-01

Full Text Available Cardiac ablation is a procedure that uses either radiofrequency or cryothermal energy to destroy cells in the heart to terminate and/or prevent arrhythmias. The indications for cardiac catheter ablation include refractory, symptomatic arrhythmias, with more specific guidelines for atrial fibrillation in particular. The ablation procedure itself involves mapping the arrhythmia and destruction of the aberrant pathway in an effort to permanently prevent the arrhythmia. There are many types of arrhythmias, and they require individualized approaches to ablation based on their innately different electrical pathways. Ablation of arrhythmias, such as Wolff-Parkinson-White syndrome, AV nodal reentrant tachycardia, and atrial-fibrillation, is discussed in this review. Ablation has a high success rate overall and minimal complication rates, leading to improved quality of life in many patients.

Percutaneous Thermal Ablation of Breast Cancer Metastases in Oligometastatic Patients

Energy Technology Data Exchange (ETDEWEB)

Barral, M., E-mail: matthias-barral@yahoo.fr [Institut Gustave Roussy, Interventional Radiology Department (France); Auperin, A., E-mail: anne.auperin@gustaveroussy.fr [Institut Gustave Roussy, Biostatistics and Epidemiology Unit (France); Hakime, A., E-mail: thakime@yahoo.com; Cartier, V., E-mail: victoirecartier@hotmail.com; Tacher, V., E-mail: vaniatacher@gmail.com [Institut Gustave Roussy, Interventional Radiology Department (France); Otmezguine, Yves, E-mail: yotmezguine@ccps.com [Centre Clinique de la Porte de Saint-Cloud, Radiotherapy (France); Tselikas, L., E-mail: lambros.tselikas@gmail.com; Baere, T. de, E-mail: thierry.debaere@gustaveroussy.fr; Deschamps, F., E-mail: frederic.deschamps@gustaveroussy.fr [Institut Gustave Roussy, Interventional Radiology Department (France)

2016-06-15

ObjectiveTo evaluate prognostic factors associated with local control and disease-free-survival (DFS) of oligometastatic breast cancer patients treated by percutaneous thermal ablation (PTA).Materials and MethodsSeventy-nine consecutive patients (54.5 ± 11.2 years old) with 114 breast cancer metastases (28.9 ± 16.1 mm in diameter), involving the lungs, the liver, and/or the bone, were treated using PTA with a curative intent. The goal was to achieve a complete remission in association with systemic chemotherapy and hormonal therapy. We retrospectively evaluated the prognostic factors associated with 1- and 2-year local control and the 1- and 2-year DFS rates.ResultsThe 1- and 2-year local control rates were 83.0 and 76.1 %, respectively. Tumor burden was associated with a poorer outcome for local control after PTA (HR 1.027 by additional millimeter, p = 0.026; >4 cm HR 3.90). The 1- and 2-year DFS rates were 54.2 and 30.4 %, respectively. In multivariate analysis, triple-negative histological subtype and increased size of treated metastases were associated with a poorer DFS (HR 2.22; 95 % CI [1.13–4.36]; p = 0.02 and HR 2.43; 95 % CI [1.22–4.82]; p = 0.011, respectively).ConclusionPTA is effective for local control of breast cancer oligometastases. Tumor burden >4 cm and triple-negative histological subtype are associated with a poorer outcome.

Deployment Instabilities of Lobed-Pumpkin Balloon

Science.gov (United States)

Nakashino, Kyoichi

A lobed-pumpkin balloon, currently being developed in ISAS/JAXA as well as in NASA, is a promising vehicle for long duration scientific observations in the stratosphere. Recent ground and flight experiments, however, have revealed that the balloon has deployment instabilities under certain conditions. In order to overcome the instability problems, a next generation SPB called 'tawara' type balloon has been proposed, in which an additional cylindrical part is appended to the standard lobed-pumpkin balloon. The present study investigates the deployment stability of tawara type SPB in comparison to that of standard lobed-pumpkin SPB through eigenvalue analysis on the basis of finite element methods. Our numerical results show that tawara type SPB enjoys excellent deployment performance over the standard lobed-pumpkin SPBs.

Gigantic balloon type artificial lightning generator

Energy Technology Data Exchange (ETDEWEB)

Horii; kenji

1988-09-05

This paper outlines a hot-air balloon type Van de Graaf 50-MV generator which can generate a 50,000,000 V, 0.2 to 0.3 coulomb artificial lightning comparable to natural lightning discharge and reports the results of investigation on discharging experiments conducted using this apparatus. The subjects covered are as follows: (1) Outline of the hot-air balloon type Van de Graaf 50-MV generator, (2) electric characteristics of the Van de Graaf 50-MV generator, (3) charge transfer with film and balloon charging, (4) the load of the balloon and buoyancy calculation, (5) leakage of charges, (6) study of charging experiments, and (7) evaluation of the apparatus and its method and problems to be solved. (4 figs, 4 tabs, 4 refs)

X-ray Micro-Tomography of Ablative Heat Shield Materials

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Panerai, Francesco; Ferguson, Joseph; Borner, Arnaud; Mansour, Nagi N.; Barnard, Harold S.; MacDowell, Alastair A.; Parkinson, Dilworth Y.

2016-01-01

X-ray micro-tomography is a non-destructive characterization technique that allows imaging of materials structures with voxel sizes in the micrometer range. This level of resolution makes the technique very attractive for imaging porous ablators used in hypersonic entry systems. Besides providing a high fidelity description of the material architecture, micro-tomography enables computations of bulk material properties and simulations of micro-scale phenomena. This presentation provides an overview of a collaborative effort between NASA Ames Research Center and Lawrence Berkeley National Laboratory, aimed at developing micro-tomography experiments and simulations for porous ablative materials. Measurements are carried using x-rays from the Advanced Light Source at Berkeley Lab on different classes of ablative materials used in NASA entry systems. Challenges, strengths and limitations of the technique for imaging materials such as lightweight carbon-phenolic systems and woven textiles are discussed. Computational tools developed to perform numerical simulations based on micro-tomography are described. These enable computations of material properties such as permeability, thermal and radiative conductivity, tortuosity and other parameters that are used in ablator response models. Finally, we present the design of environmental cells that enable imaging materials under simulated operational conditions, such as high temperature, mechanical loads and oxidizing atmospheres.Keywords: Micro-tomography, Porous media, Ablation

Influence of transcatheter hepatic artery embolization using iodized oil on radiofrequency ablation of hepatic neoplasms

International Nuclear Information System (INIS)

Du Xilin; Ma Qingjiu; Wang Yiqing; Wang Zhimin; Zhang Hongxin

2004-01-01

Objective: To observe the effect of iodized oil on radiofrequency thermal ablation (RFA) of hepatic neoplasms by using a cluster array of ten separate electrodes. Methods: The patients were divided into 2 groups, group A with transcatheter hepatic artery embolization, group B without transcatheter hepatic artery embolization. All patients were undergone radiofrequency ablation of hepatic neoplasms. Results: The time of RFA for group A was (9 ± 2.1) minutes, showing the diameter of necrosis of (5.3 ± 1.4) cm. The time of RFA for group B was (16 ± 4. 6) minutes demonstrating the diameter of necrosis of (3.5 ± 1.8) cm (P<0.01). Conclusions: These findings suggest that radiofrequency thermal ablation of hepatic neoplasms with transcatheter hepatic artery embolization using iodized oil might improve the safety and synergic effect

Balloon cell nevus of the iris.

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Morcos, Mohib W; Odashiro, Alexandre; Bazin, Richard; Pereira, Patricia Rusa; O'Meara, Aisling; Burnier, Miguel N

2014-12-01

Balloon cell nevus is a rare histopathological lesion characterized by a predominance of large, vesicular and clear cells, called balloon cells. There is only 1 case of balloon cell nevus of the iris reported in the literature. A 55 year-old man presented a pigmented elevated lesion in the right iris since the age of 12 years old. The lesion had been growing for the past 2 years and excision was performed. Histopathological examination showed a balloon cell nevus composed of clear and vacuolated cells without atypia. A typical spindle cell nevus of the iris was also observed. The differential diagnosis included xanthomatous lesions, brown adipocyte or other adipocytic lesions, clear cell hidradenoma, metastatic clear cell carcinoma of the kidney and clear cell sarcoma. The tumor was positive for Melan A, S100 protein and HMB45. Balloon cell nevus of the iris is rare but should be considered in the differential diagnosis of melanocytic lesions of the iris. Copyright © 2014 Elsevier GmbH. All rights reserved.

The Titan Sky Simulator ™ - Testing Prototype Balloons in Conditions Approximating those in Titan's Atmosphere

Science.gov (United States)

Nott, Julian

This paper will describe practical work flying prototype balloons in the "The Titan Sky Simulator TM " in conditions approximating those found in Titan's atmosphere. Saturn's moon, Titan, is attracting intense scientific interest. This has led to wide interest in exploring it with Aerobots, balloons or airships. Their function would be similar to the Rovers exploring Mars, but instead of moving laboriously across the rough terrain on wheels, they would float freely from location to location. To design any balloon or airship it is essential to know the temperature of the lifting gas as this influences the volume of the gas, which in turn influences the lift. To determine this temperature it is necessary to know how heat is transferred between the craft and its surroundings. Heat transfer for existing balloons is well understood. However, Titan conditions are utterly different from those in which balloons have ever been flown, so heat transfer rates cannot currently be calculated. In particular, thermal radiation accounts for most heat transfer for existing balloons but over Titan heat transfer will be dominated by convection. To be able to make these fundamental calculations, it is necessary to get fundamental experimental data. This is being obtained by flying balloons in a Simulator filled with nitrogen gas at very low temperature, about 95° K / minus 180° C, typical of Titan's temperatures. Because the gas in the Simulator is so cold, operating at atmospheric pressure the density is close to that of Titan's atmosphere. "The Titan Sky Simulator TM " has an open interior approximately 4.5 meter tall and 2.5 meters square. It has already been operated at 95° K/-180° C. By the time of the Conference it is fully expected to have data to present from actual balloons flying at this temperature. Perhaps the most important purpose of this testing is to validate numerical [computational fluid dynamics] models being developed by Tim Colonius of Caltech. These numerical

Mars Solar Balloon Lander, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — The Mars Solar Balloon Lander (MSBL) is a novel concept which utilizes the capability of solar-heated hot air balloons to perform soft landings of scientific...

Targeted Vessel Ablation for More Efficient Magnetic Resonance-Guided High-Intensity Focused Ultrasound Ablation of Uterine Fibroids

Energy Technology Data Exchange (ETDEWEB)

Voogt, Marianne J., E-mail: m.voogt@umcutrecht.nl [University Medical Center Utrecht, Department of Radiology (Netherlands); Stralen, Marijn van [University Medical Center Utrecht, Image Sciences Institute (Netherlands); Ikink, Marlijne E. [University Medical Center Utrecht, Department of Radiology (Netherlands); Deckers, Roel; Vincken, Koen L.; Bartels, Lambertus W. [University Medical Center Utrecht, Image Sciences Institute (Netherlands); Mali, Willem P. Th. M.; Bosch, Maurice A. A. J. van den [University Medical Center Utrecht, Department of Radiology (Netherlands)

2012-10-15

Purpose: To report the first clinical experience with targeted vessel ablation during magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) treatment of symptomatic uterine fibroids. Methods: Pretreatment T1-weighted contrast-enhanced magnetic resonance angiography was used to create a detailed map of the uterine arteries and feeding branches to the fibroids. A three-dimensional overlay of the magnetic resonance angiography images was registered on 3D T2-weighted pretreatment imaging data. Treatment was focused primarily on locations where supplying vessels entered the fibroid. Patients were followed 6 months after treatment with a questionnaire to assess symptoms and quality of life (Uterine Fibroid Symptom and Quality of Life) and magnetic resonance imaging to quantify shrinkage of fibroid volumes. Results: In two patients, three fibroids were treated with targeted vessel ablation during MR-HIFU. The treatments resulted in almost total fibroid devascularization with nonperfused volume to total fibroid volume ratios of 84, 68, and 86%, respectively, of treated fibroids. The predicted ablated volumes during MR-HIFU in patients 1 and 2 were 45, 40, and 82 ml, respectively, while the nonperfused volumes determined immediately after treatment were 195, 92, and 190 ml respectively, which is 4.3 (patient 1) and 2.3 (patient 2) times higher than expected based on the thermal dose distribution. Fibroid-related symptoms reduced after treatment, and quality of life improved. Fibroid volume reduction ranged 31-59% at 6 months after treatment. Conclusion: Targeted vessel ablation during MR-HIFU allowed nearly complete fibroid ablation in both patients. This technique may enhance the use of MR-HIFU for fibroid treatment in clinical practice.

Microsecond enamel ablation with 10.6μm CO2 laser radiation

Science.gov (United States)

Góra, W. S.; McDonald, A.; Hand, D. P.; Shephard, J. D.

2016-02-01

Lasers have been previously been used for dental applications, however there remain issues with thermally-induced cracking. In this paper we investigate the impact of pulse length on CO2 laser ablation of human dental enamel. Experiments were carried in vitro on molar teeth without any modification to the enamel surface, such as grinding or polishing. In addition to varying the pulse length, we also varied pulse energy and focal position, to determine the most efficient ablation of dental hard tissue and more importantly to minimize or eradicate cracking. The maximum temperature rise during the multi pulse ablation process was monitored using a set of thermocouples embedded into the pulpal chamber. The application of a laser device in dental surgery allows removal of tissue with higher precision, which results in minimal loss of healthy dental tissue. In this study we use an RF discharge excited CO2 laser operating at 10.6μm. The wavelength of 10.6 μm overlaps with a phosphate band (PO3-4) absorption in dental hard tissue hence the CO2 laser radiation has been selected as a potential source for modification of the tissue. This research describes an in-depth analysis of single pulse laser ablation. To determine the parameters that are best suited for the ablation of hard dental tissue without thermal cracking, a range of pulse lengths (10-200 μs), and fluences (0-100 J/cm2) are tested. In addition, different laser focusing approaches are investigated to select the most beneficial way of delivering laser radiation to the surface (divergent/convergent beam). To ensure that these processes do not increase the temperature above the critical threshold and cause the necrosis of the tissue a set of thermocouples was placed into the pulpal chambers. Intermittent laser radiation was investigated with and without application of a water spray to cool down the ablation site and the adjacent area. Results show that the temperature can be kept below the critical threshold

Therapeutic efficacy of percutaneous radiofrequency ablation versus microwave ablation for hepatocellular carcinoma.

Directory of Open Access Journals (Sweden)

Lei Zhang

Full Text Available The aim of this study was to investigate the therapeutic efficacy of percutaneous radiofrequency (RF ablation versus microwave (MW ablation for hepatocellular carcinoma (HCC measuring ≤ 5 cm in greatest diameter. From January 2006 to December 2006, 78 patients had undergone RF ablation whereas 77 had undergone MW ablation. Complete ablation (CA, local tumour progression (LTP and distant recurrence (DR were compared. The overall survival curves were calculated with the Kaplan-Meier technique and compared with the log-rank test. The CA rate was 83.4% (78/93 for RF ablation and 86.7%(91/105 for MW ablation. The LTP rate was 11.8% (11/93 for RF ablation and 10.5% (11/105 for MW ablation. DR was found in 51 (65.4% in the RF ablation and 62 (80.5% in the MW ablation. There was no significant difference in the 1-, 3-, and 5-year overall survival rates (P = 0.780 and the 1-, 3-, and 5-year disease-free survival rates (P = 0.123 between RF and MW ablation. At subgroup analyses, for patients with tumors ≤ 3.0 cm, there was no significant difference in the 1-, 3-, and 5-year overall survival rates (P = 0.067 and the corresponding disease-free survival rates(P = 0.849. For patients with tumor diameters of 3.1-5.0 cm, the 1-, 3-, and 5-year overall survival rates were 87.1%, 61.3%, and 40.1% for RF ablation and 85.4%, 36.6%, and 22% for MW ablation, with no significant difference (P = 0.068. The corresponding disease-free survival rates were 74.2%, 54.8%, and 45.2% for the RF ablation group and 53.3%, 26.8%, and 17.1% for the MW ablation group. The disease-free survival curve for the RF ablation group was significantly better than that for the MW ablation group (P = 0.018. RF ablation and MW ablation are both effective methods in treating hepatocellular carcinomas, with no significant differences in CA, LTP, DR, and overall survival.

GCD TechPort Data Sheets Thermal Protection System Materials (TPSM) Project

Science.gov (United States)

Chinnapongse, Ronald L.

2014-01-01

The Thermal Protection System Materials (TPSM) Project consists of three distinct project elements: the 3-Dimensional Multifunctional Ablative Thermal Protection System (3D MAT) project element; the Conformal Ablative Thermal Protection System (CA-TPS) project element; and the Heatshield for Extreme Entry Environment Technology (HEEET) project element. 3D MAT seeks to design, develop and deliver a game changing material solution based on 3-dimensional weaving and resin infusion approach for manufacturing a material that can function as a robust structure as well as a thermal protection system. CA-TPS seeks to develop and deliver a conformal ablative material designed to be efficient and capable of withstanding peak heat flux up to 500 W/ sq cm, peak pressure up to 0.4 atm, and shear up to 500 Pa. HEEET is developing a new ablative TPS that takes advantage of state-of-the-art 3D weaving technologies and traditional manufacturing processes to infuse woven preforms with a resin, machine them to shape, and assemble them as a tiled solution on the entry vehicle substructure or heatshield.

Vertical sounding balloons for stratospheric photochemistry

Science.gov (United States)

Pommereau, J. P.

The use of vertical sounding balloons for stratospheric photochemistry studies is illustrated by the use of a vertical piloted gas balloon for the search of NO2 diurnal variations. It is shown that the use of montgolfieres (hot air balloons) can enhance the vertical sounding technique. Particular attention is given to a sun-heated montgolfiere and to the more sophisticated infrared montgolfiere that is able to perform three to four vertical excursions per day and to remain aloft for weeks or months.

Boston's balloon dilatation for treatment of cardiac achalasia

International Nuclear Information System (INIS)

Yin Jianguo; Song Jinwen; Yang Yan; Liu Xiaohong; Fu Zhiming; Zhang Yaqin

2001-01-01

Objective: To review and summarize effectiveness and method of the Boston's balloon dilation in cardiac achalasia. Methods: The intensified guide wire was inserted into stomach through mouth cavity under TV control. The Boston's balloon was inserted to the cardiac stricture through the guide wire and dilatated with 15% contrast medium with to a maximum diameter for five minutes and then the balloon was dilatated again for 3-5 minutes, all together for 3-4 times. The severe stricture must be pre-dilatated with 20-25 mm diameter balloon. Results: The balloon insertion was technically successful in all 26 patients. The once success of balloon dilation was achieved in 24 patients and twice in other 2. Follow-up time was from 2 weeks to 31 months (mean 10.6 months). Recurrent stenosis had not occurred in all patients. Remission rate of dysphagia was 100%. Esophageal reflux occurred in 3 patients. Conclusions: The Boston's balloon dilatation is simple and effective for treatment of cardiac achalasia. The method sometimes may replace surgical procedure

Clinical experience with the Monorail balloon catheter for coronary angioplasty.

Science.gov (United States)

Finci, L; Meier, B; Roy, P; Steffenino, G; Rutishauser, W

1988-01-01

The Monorail balloon catheter is distinctly different from other current balloon catheters: the guidewire passes through the balloon itself, exits the catheter proximal to the balloon, and runs alongside its small shaft (3 French) through the guiding catheter. Monorail coronary angioplasty was attempted in 61 patients on 73 lesions with balloons from 2.0 to 3.7 mm. Angiographic success was obtained in 66 lesions (90%). For 15 lesions, balloon exchanges were needed. In three lesions, the Monorail balloon failed to cross the lesion, while a standard balloon succeeded; two lesions could not be crossed with any balloon. Vessel occlusion occurred in four patients: two had emergency surgery without infarct (one died suddenly 4 days later and one had a stroke 1 day later), one was recanalized with a standard balloon, and one had a myocardial infarct. Continuous infusion of urokinase was used until patient 3 in whom problems with the delivery system led to cardiocerebral air embolization (with complete recovery). No thrombotic complications were observed in the subsequent 58 patients with only a bolus of 10,000 U of heparin. The Monorail balloon facilitates contrast injections and balloon exchanges but appears more difficult to pass through tight lesions. Omission of the previously recommended infusion with a thrombolytic agent proved safe.

Use of monorail PTCA balloon catheter for local drug delivery.

Science.gov (United States)

Trehan, Vijay; Nair, Girish M; Gupta, Mohit D

2007-01-01

We report the use of monorail coronary balloon as an infusion catheter to give bailout abciximab selectively into the site of stent thrombosis as an adjunct to plain old balloon angioplasty (POBA) in a patient of subacute stent thrombosis of the left anterior descending coronary artery. The balloon component (polyamide material) of the monorail balloon catheter was shaved off the catheter so that abciximab injected through the balloon port of the catheter exited out the shaft of the balloon catheter at the site from where the balloon material was shaved off. We believe that selective infusion with abciximab along with POBA established antegrade flow and relieved the patient's ischemia. In the absence of essential hardware to give intracoronary drugs in an emergency situation, one may employ our technique of infusion through a monorail balloon catheter after shaving the balloon component from the catheter.

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

Science.gov (United States)

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

2017-12-01

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

[Monitoring radiofrequency ablation by ultrasound temperature imaging and elastography under different power intensities].

Science.gov (United States)

Geng, Xiaonan; Li, Qiang; Tsui, Pohsiang; Wang, Chiaoyin; Liu, Haoli

2013-09-01

To evaluate the reliability of diagnostic ultrasound-based temperature and elasticity imaging during radiofrequency ablation (RFA) through ex vivo experiments. Procine liver samples (n=7) were employed for RFA experiments with exposures of different power intensities (10 and 50w). The RFA process was monitored by a diagnostic ultrasound imager and the information were postoperatively captured for further temperature and elasticity image analysis. Infrared thermometry was concurrently applied to provide temperature change calibration during the RFA process. Results from this study demonstrated that temperature imaging was valid under 10 W RF exposure (r=0.95), but the ablation zone was no longer consistent with the reference infrared temperature distribution under high RF exposures. The elasticity change could well reflect the ablation zone under a 50 W exposure, whereas under low exposures, the thermal lesion could not be well detected due to the limited range of temperature elevation and incomplete tissue necrosis. Diagnostic ultrasound-based temperature and elastography is valid for monitoring thr RFA process. Temperature estimation can well reflect mild-power RF ablation dynamics, whereas the elastic-change estimation can can well predict the tissue necrosis. This study provide advances toward using diagnostic ultrasound to monitor RFA or other thermal-based interventions.

Growth rates of the ablative Rayleigh endash Taylor instability in inertial confinement fusion

International Nuclear Information System (INIS)

Betti, R.; Goncharov, V.N.; McCrory, R.L.; Verdon, C.P.

1998-01-01

A simple procedure is developed to determine the Froude number Fr, the effective power index for thermal conduction ν, the ablation-front thickness L 0 , the ablation velocity V a , and the acceleration g of laser-accelerated ablation fronts. These parameters are determined by fitting the density and pressure profiles obtained from one-dimensional numerical simulations with the analytic isobaric profiles of Kull and Anisimov [Phys. Fluids 29, 2067 (1986)]. These quantities are then used to calculate the growth rate of the ablative Rayleigh endash Taylor instability using the theory developed by Goncharov et al. [Phys. Plasmas 3, 4665 (1996)]. The complicated expression of the growth rate (valid for arbitrary Froude numbers) derived by Goncharov et al. is simplified by using reasonably accurate fitting formulas. copyright 1998 American Institute of Physics

N-butyl cyanoacrylate embolization with blood flow control of an arterioportal shunt that developed after radiofrequency ablation of hepatocellular carcinoma

Energy Technology Data Exchange (ETDEWEB)

Sonomura, Tetsuo; Kawai, Nobuyuki; Kishi, Kazushi [Wakayama Medical University, Wakayama (Japan); and others

2014-04-15

We present a case of a patient with rapid deterioration of esophageal varices caused by portal hypertension accompanied by a large arterioportal shunt that developed after radiofrequency ablation of hepatocellular carcinoma. We used n-butyl cyanoacrylate (NBCA) as an embolic material to achieve pinpoint embolization of the shunt, because the microcatheter tip was 2 cm away from the shunt site. Under hepatic arterial flow control using a balloon catheter, the arterioportal shunt was successfully embolized with NBCA, which caused an improvement in the esophageal varices.

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

Science.gov (United States)

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

2015-01-01

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

Microjet-assisted dye-enhanced diode laser ablation of cartilaginous tissue

Science.gov (United States)

Pohl, John; Bell, Brent A.; Motamedi, Massoud; Frederickson, Chris J.; Wallace, David B.; Hayes, Donald J.; Cowan, Daniel

1994-08-01

Recent studies have established clinical application of laser ablation of cartilaginous tissue. The goal of this study was to investigate removal of cartilaginous tissue using diode laser. To enhance the interaction of laser light with tissue, improve the ablation efficiency and localize the extent of laser-induced thermal damage in surrounding tissue, we studied the use of a novel delivery system developed by MicroFab Technologies to dispense a known amount of Indocyanine Green (ICG) with a high spatial resolution to alter the optical properties of the tissue in a controlled fashion. Canine intervertebral disks were harvested and used within eight hours after collection. One hundred forty nL of ICG was topically applied to both annulus and nucleus at the desired location with the MicroJet prior to each irradiation. Fiber catheters (600 micrometers ) were used and positioned to irradiate the tissue with a 0.8 mm spot size. Laser powers of 3 - 10 W (Diomed, 810 nm) were used to irradiate the tissue with ten pulses (200 - 500 msec). Discs not stained with ICG were irradiated as control samples. Efficient tissue ablation (80 - 300 micrometers /pulse) was observed using ICG to enhance light absorption and confine thermal damage while there was no observable ablation in control studied. The extent of tissue damage observed microscopically was limited to 50 - 100 micrometers . The diode laser/Microjet combination showed promise for applications involving removal of cartilaginous tissue. This procedure can be performed using a low power compact diode laser, is efficient, and potentially more economical compared to procedures using conventional lasers.

Structure variations of pumpkin balloon

Science.gov (United States)

Yajima, N.; Izutsu, N.; Honda, H.

2004-01-01

A lobed pumpkin balloon by 3-D gore design concept is recognized as a basic form for a super-pressure balloon. This paper deals with extensions of this design concept for other large pressurized membrane structures, such as a stratospheric airship and a balloon of which volume is controllable. The structural modifications are performed by means of additional ropes, belts or a strut. When the original pumpkin shape is modified by these systems, the superior characteristics of the 3-D gore design, incorporating large bulges with a small local radius and unidirectional film tension, should be maintained. Improved design methods which are adequate for the above subjects will be discussed in detail. Application for ground structures are also mentioned.

Chemical nonequilibrium Navier-Stokes solutions for hypersonic flow over an ablating graphite nosetip

Science.gov (United States)

Chen, Y. K.; Henline, W. D.

1993-01-01

The general boundary conditions including mass and energy balances of chemically equilibrated or nonequilibrated gas adjacent to ablating surfaces have been derived. A computer procedure based on these conditions was developed and interfaced with the Navier-Stokes solver for predictions of the flow field, surface temperature, and surface ablation rates over re-entry space vehicles with ablating Thermal Protection Systems (TPS). The Navier-Stokes solver with general surface thermochemistry boundary conditions can predict more realistic solutions and provide useful information for the design of TPS. A test case with a proposed hypersonic test vehicle configuration and associated free stream conditions was developed. Solutions with various surface boundary conditions were obtained, and the effect of nonequilibrium gas as well as surface chemistry on surface heating and ablation rate were examined. The solutions of the GASP code with complete ablating surface conditions were compared with those of the ASC code. The direction of future work is also discussed.

Development of a Super-Pressure Balloon with an Improved Design

Science.gov (United States)

Izutsu, Naoki; Akita, Daisuke; Fuke, Hideyuki; Iijima, Issei; Kato, Yoichi; Kawada, Jiro; Matsushima, Kiyoho; Matsuzaka, Yukihiko; Mizuta, Eiichi; Nakada, Takashi; Nonaka, Naoki; Saito, Yoshitaka; Takada, Atsushi; Tamura, Keisuke; Yamada, Kazuhiko; Yoshida, Tetsuya

A zero-pressure balloon used for scientific observation in the stratosphere has an unmanageable limitation that its floating altitude decreases during a nighttime because of temperature drop of the lifting gas. Since a super-pressure balloon may not change its volume, the lifetime can extend very long. We had introduced so called the ‘lobed-pumpkin’ type of super-pressure balloon that can realize a full-scale long-duration balloon and it will be in practical use in the very near future. As for larger super-pressure balloons, however, we still have some potential difficulties to be resolved. We here propose a new design suitable for a larger super-pressure balloon, which is roughly ‘lobed pumpkin with lobed cylinder’ and can adapt a single design for balloons of a wide range of volumes. Indoor inflation tests were successfully carried out with balloons designed and made by the method. It has been shown that the limit of the resisting pressure differential for a new designed balloon is same as that of a normal lobed-pumpkin balloon.

Ballooning behavior in the golden orbweb spider Nephilapilipes (Araneae: Nephilidae

Directory of Open Access Journals (Sweden)

Vanessa M.J. Lee

2015-01-01

Full Text Available Ballooning, a mode of aerial dispersal in spiders, is an innate behavior that requires appropriate physiological and meteorological conditions. Although only rarely reported in the golden orbweb spiders, family Nephilidae, the large geographic distributions of most nephilids—in particular of Nephila species—would imply that these spiders likely routinely disperse by ballooning in spite of giant female sizes. Here we study ballooning behavior in the golden orbweb spider Nephila pilipes (Fabricius, 1793. Specifically, we test for the propensity of spiderlings to deploy ballooning as a dispersal mechanism. We subjected a total of 59 first-instar spiderlings to a wind experiment at two wind speeds (2.17 ± 0.02 m s-1 and 3.17 ± 0.02 m s-1 under laboratory conditions. Under an average wind speed of 3.17 m s-1, none of the spiderlings exhibited pre-ballooning or ballooning behavior. However, at an average wind speed of 2.17 m s-1, 53 (89.8% spiderlings showed pre-ballooning behavior, and 17 (32.1% of the pre-ballooners ultimately ballooned. Our results concur with prior reports on spiderlings of other families that pre-ballooning behavior is a requirement for ballooning to occur. Furthermore, although we cannot rule out other dispersal mechanisms such as synanthropic spread, our findings suggest that the widespread N. pilipes uses ballooning to colonize remote oceanic islands.

Evaluation of great saphenous vein occlusion rate and clinical outcome in patients undergoing laser thermal ablation with a 1470-nm bare fiber laser with low linear endovenous energy density

Directory of Open Access Journals (Sweden)

Walter Junior Boim Araujo

2015-12-01

Full Text Available Abstract Background Water-specific 1470-nm lasers enable vein ablation at lower energy densities and with fewer side effects because they target interstitial water in the vessel wall. Objectives To determine great saphenous vein (GSV occlusion rate after thermal ablation with 1470-nm laser using 7W power and to evaluate clinical outcomes and complications. Method Nineteen patients (31 GSVs underwent thermal ablation. Follow-up duplex scanning, clinical evaluation using the Venous Clinical Severity Score (VCSS, and evaluation of procedure-related complications were performed at 3-5 days after the procedure and at 30 and 180 days. Results Mean patient age was 46 years and 17 of the patients were female (89.47%. Of 31 limbs treated, 2 limbs were clinical class C2, 19 were C3, 9 were C4, and 1 limb was C5 according to the Clinical-Etiology-Anatomy-Pathophysiology (CEAP classification. Mean linear endovenous energy density was 33.53 J/cm. The GSV occlusion rate was 93.5% immediately after treatment, 100% at 3-5 days and 100% at 30 days after treatment and 87.1% 180 days after treatment. There was a significant reduction in VCSS at all time points. Conclusions The data from this study support the possibility that the incidence of complications can be reduced without significantly affecting the clinical outcomes, by using lower energy density. However, this appears to be at the cost of reduced efficacy in terms of GSV occlusion rates.

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

Science.gov (United States)

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

2013-01-01

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

Optimizing logistics for balloon-occluded retrograde transvenous obliteration (BRTO) of gastric varices by doing away with the indwelling balloon: concept and techniques.

Science.gov (United States)

Saad, Wael E; Nicholson, David B

2013-06-01

Since the conception of balloon-occluded retrograde transvenous obliteration (BRTO) of gastric varices 25 years ago, the placement of an indwelling balloon for hours has been central to the BRTO procedure. Numerous variables and variations of the BRTO procedure have been described, including methods to reduce sclerosant, combining percutaneous transhepatic obliteration, varying sclerosant, and using multiple sclerosants within the same procedure. However, the consistent feature of BRTO has always remained the indwelling balloon. Placing an indwelling balloon over hours for the BRTO procedure is a logistical burden that taxes the interventional radiology team and hospital resources. Substituting the balloon with hardware (coils or Amplatzer vascular plugs [AVPs] or both) is technically feasible and its risks most likely correlate with gastrorenal shunt (GRS) size. The current authors use packed 0.018- or 0.035-in coils or both for small gastric variceal systems (GRS size A and B) and AVPs for GRS sizes up to size E (from size A-E). The current authors recommend an indwelling balloon (no hardware substitute) for very large gastric variceal system (GRS size F). Substituting the indwelling balloon for hardware in size F and potentially size E GRS can also be risky. The current article describes the techniques of placing up to 16-mm AVPs through balloon occlusion guide catheters and then deflating the balloon once it has been substituted with the AVPs. In addition, 22-mm AVPs can be placed through sheaths once the balloon occlusion catheters are removed to further augment the 16-mm Amplatzer occlusion. To date, there are no studies describing, let alone evaluating, the clinical feasibility of performing BRTO without indwelling balloons. The described techniques have been successfully performed by the current authors. However, the long-term safety and effectiveness of these techniques is yet to be determined. Copyright © 2013 Elsevier Inc. All rights reserved.

Ultrasound-guided radiofrequency thermal ablation of normal kidney in a rabbit model: correlation with CT and histopathology

Energy Technology Data Exchange (ETDEWEB)

Kim, Sang Won; Lee, Jeong Min; Kin, Chong Soo; Lee, Sang Hun [College of Medicine, Chonbuk National Univ., Chonju (Korea, Republic of)

2002-01-01

To assess the feasibility and safety of using a cooled-tip electrode to perform percutaneous radiofrequency ablation of kidney tissue in rabbits, and to evaluate the ability of CT to reveal the appearance and extent of tissue necrosis during follow-up after ablation. Using ultrasound guidance, a 17-G cooled-tip electrode was inserted into the right lower portion of the kidney in 26 New Zealand White rabbits. Radiofrequency was applied for 2 mins, and biphasic helical CT scanning was used to assess tissue destruction and the presence or absence of complications immediately after the procedure and at 24 hrs, 2 and 3 days, and 1,2,3,4,5,6 and 7 weeks. The study had three phases: acute (immediately killed : N=10); subacute (killed at 24 hrs (n=3), 2 days (n=3), 3 days (n=1) : N=7); chronic (killed at 1 week (n=4), 2 weeks (n=2), 4 weeks (n=1), 7 weeks (n=1): N=8). After the animals were killed, their kidneys were histopathologically examined and the radiologic and pathologic findings of lesion size and configuration were correlated. In each instance, ultrasound-guided radiofrequency ablations of the lower pole of the kidney were technically successful. Contrast-enhanced biphasic helical CT revealed regions of hypoattenuation devoid of parenchymal enhancement, and these correlated closely with true pathologic lesion size (r=0.884; p>0.05). In subacute and chronic models, CT scanning revealed gradual spontaneous resorption of the ablated lesion and the presence of perilesional calcification. Histopathologically, in the acute phase the ablated lesion showed coagulative necrosis and infiltration of inflammatory cells, and in the chronic phase there was clear cut necrosis of glomeruli, tubules and renal interstitium, with diminishing inflammatory response and peripheral fibrotic tissue formation. Ultrasound-guided renal radiofrequency ablation is technically feasible and safe. In addition, the avascular lesion measured at contrast-enhanced helical CT closely correlated with

Ultrasound-guided radiofrequency thermal ablation of normal kidney in a rabbit model: correlation with CT and histopathology

International Nuclear Information System (INIS)

Kim, Sang Won; Lee, Jeong Min; Kin, Chong Soo; Lee, Sang Hun

2002-01-01

To assess the feasibility and safety of using a cooled-tip electrode to perform percutaneous radiofrequency ablation of kidney tissue in rabbits, and to evaluate the ability of CT to reveal the appearance and extent of tissue necrosis during follow-up after ablation. Using ultrasound guidance, a 17-G cooled-tip electrode was inserted into the right lower portion of the kidney in 26 New Zealand White rabbits. Radiofrequency was applied for 2 mins, and biphasic helical CT scanning was used to assess tissue destruction and the presence or absence of complications immediately after the procedure and at 24 hrs, 2 and 3 days, and 1,2,3,4,5,6 and 7 weeks. The study had three phases: acute (immediately killed : N=10); subacute (killed at 24 hrs (n=3), 2 days (n=3), 3 days (n=1) : N=7); chronic (killed at 1 week (n=4), 2 weeks (n=2), 4 weeks (n=1), 7 weeks (n=1): N=8). After the animals were killed, their kidneys were histopathologically examined and the radiologic and pathologic findings of lesion size and configuration were correlated. In each instance, ultrasound-guided radiofrequency ablations of the lower pole of the kidney were technically successful. Contrast-enhanced biphasic helical CT revealed regions of hypoattenuation devoid of parenchymal enhancement, and these correlated closely with true pathologic lesion size (r=0.884; p>0.05). In subacute and chronic models, CT scanning revealed gradual spontaneous resorption of the ablated lesion and the presence of perilesional calcification. Histopathologically, in the acute phase the ablated lesion showed coagulative necrosis and infiltration of inflammatory cells, and in the chronic phase there was clear cut necrosis of glomeruli, tubules and renal interstitium, with diminishing inflammatory response and peripheral fibrotic tissue formation. Ultrasound-guided renal radiofrequency ablation is technically feasible and safe. In addition, the avascular lesion measured at contrast-enhanced helical CT closely correlated with

How to perform combined cutting balloon and high pressure balloon valvuloplasty for dogs with subaortic stenosis.

Science.gov (United States)

Kleman, Mandi E; Estrada, Amara H; Maisenbacher, Herbert W; Prošek, Robert; Pogue, Brandon; Shih, Andre; Paolillo, Joseph A

2012-01-01

Subvalvular aortic stenosis (SAS) is one of the most common congenital cardiac malformations in dogs. Unfortunately, the long term success rate and survival data following either open heart surgery or catheter based intervention has been disappointing in dogs with severe subaortic stenosis. Medical therapy is currently the only standard recommended treatment option. A cutting balloon dilation catheter has been used successfully for resistant coronary artery and peripheral pulmonary arterial stenoses in humans. This catheter is unique in that it has the ability to cut, or score, the stenotic region prior to balloon dilatation of the stenosis. The use of cutting balloon valvuloplasty combined with high pressure valvuloplasty for dogs with severe subaortic stenosis has recently been reported to be a safe and feasible alternative therapeutic option. The following report describes this technique, outlines the materials required, and provides some 'tips' for successful percutaneous subaortic balloon valvuloplasty. Copyright © 2012 Elsevier B.V. All rights reserved.

21 CFR 884.5050 - Metreurynter-balloon abortion system.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Metreurynter-balloon abortion system. 884.5050... Devices § 884.5050 Metreurynter-balloon abortion system. (a) Identification. A metreurynter-balloon abortion system is a device used to induce abortion. The device is inserted into the uterine cavity...

Effect of ablation geometry on the dynamics, composition, and geometrical shape of thin film plasma

Science.gov (United States)

Mondal, Alamgir; Singh, R. K.; Kumar, Ajai

2018-01-01

The characteristics of plasma plume produced by front and back ablation of thin films have been investigated using fast imaging and optical emission spectroscopy. Ablation geometry dependence of the plume dynamics, its geometrical aspect and composition is emphasized. Also, the effect of an ambient environment and the beam diameter of an ablating laser on the front and back ablations is briefly discussed. Analysis of time resolved images and plasma parameters indicates that the energetic and spherical plasma formed by front ablation is strikingly different in comparison to the slow and nearly cylindrical plasma plume observed in the case of back ablation. Further shock formation, plume confinement, thermalization and validity of different expansion models in these two ablation geometries are also presented. The present study demonstrates the manipulation of kinetic energy, shape, ion/neutral compositions and directionality of the expanding plume by adjusting the experimental configuration, which is highly relevant to its utilization in various applications e.g., generation of energetic particles, tokamak edge plasma diagnostics, thin film deposition, etc.

Particular Morphology of Inferior Pulmonary Veins and Difficulty of Cryoballoon Ablation in Patients With Paroxysmal Atrial Fibrillation.

Science.gov (United States)

Yasuoka, Ryobun; Kurita, Takashi; Kotake, Yasuhito; Hashiguchi, Naotaka; Motoki, Koichiro; Kobuke, Kazuhiro; Iwanaga, Yoshitaka; Miyazaki, Shunichi

2017-04-25

The CRYO-Japan PMS study indicated that cryoballoon ablation (Cryo-Abl) has a lower acute success rate of pulmonary vein isolation (PVI) for the right and left inferior PVs (RIPV and LIPV, respectively) than for the superior PVs. This study aimed to determine if the orientation and position of the inferior PVs are related to the difficulty of acute success of PVI.Methods and Results:We investigated 30 consecutive patients who underwent Cryo-Abl. A "difficult PV" was defined as the requirement for >2 cooling applications and/or touch-up ablation to achieve PVI. We measured the ventral angle between the vertical line and the direction of each PV trunk (PV angle) on the transverse plane of enhanced CT images. PV position was defined as the difference in the levels between the bottom of the RIPVs and the non-coronary cusp of the aorta. PV angle position position: OR=12.14, CI -2.77301 to -0.23160, P=0.014). PV position difficulty of LIPV isolation (OR=5.78, CI -1.77095 to -0.09474, P=0.027). RIPV with ventral orientation may require difficult maneuvers to advance an ablation system towards it. Low take-off of the inferior PVs may cause non-coaxial configuration of balloon catheters towards the direction of these veins.

Balloon launching station, Mildura, Victoria

International Nuclear Information System (INIS)

The Mildura Balloon Launching Station was established in 1960 by the Department of Supply (now the Department of Manufacturing Industry) on behalf of the United States Atomic Energy Commission (USAEC) to determine the content of radioactive material in the upper atmosphere over Australia. The Station location and layout, staffing, balloon launching equipment, launching, tracking and recovery are described. (R.L.)

Differences in Nanosecond Laser Ablation and Deposition of Tungsten, Boron, and WB2/B Composite due to Optical Properties

Directory of Open Access Journals (Sweden)

Tomasz Moscicki

2016-01-01

Full Text Available The first attempt to the deposition of WB3 films using nanosecond Nd:YAG laser demonstrated that deposited coatings are superhard. However, they have very high roughness. The deposited films consisted mainly of droplets. Therefore, in the present work, the explanation of this phenomenon is conducted. The interaction of Nd:YAG nanosecond laser pulse with tungsten, boron, and WB2/B target during ablation is investigated. The studies show the fundamental differences in ablation of those materials. The ablation of tungsten is thermal and occurs due to only evaporation. In the same conditions, during ablation of boron, the phase explosion and/or fragmentation due to recoil pressure is observed. The deposited films have a significant contribution of big debris with irregular shape. In the case of WB2/B composite, ablation is significantly different. The ablation seems to be the detonation in the liquid phase. The deposition mechanism is related mainly to the mechanical transport of the target material in the form of droplets, while the gaseous phase plays marginal role. The main origin of differences is optical properties of studied materials. A method estimating phase explosion occurrence based on material data such as critical temperature, thermal diffusivity, and optical properties is shown. Moreover, the effect of laser wavelength on the ablation process and the quality of the deposited films is discussed.

Fiber Optic Sensors for Temperature Monitoring during Thermal Treatments: An Overview

Science.gov (United States)

Schena, Emiliano; Tosi, Daniele; Saccomandi, Paola; Lewis, Elfed; Kim, Taesung

2016-01-01

During recent decades, minimally invasive thermal treatments (i.e., Radiofrequency ablation, Laser ablation, Microwave ablation, High Intensity Focused Ultrasound ablation, and Cryo-ablation) have gained widespread recognition in the field of tumor removal. These techniques induce a localized temperature increase or decrease to remove the tumor while the surrounding healthy tissue remains intact. An accurate measurement of tissue temperature may be particularly beneficial to improve treatment outcomes, because it can be used as a clear end-point to achieve complete tumor ablation and minimize recurrence. Among the several thermometric techniques used in this field, fiber optic sensors (FOSs) have several attractive features: high flexibility and small size of both sensor and cabling, allowing insertion of FOSs within deep-seated tissue; metrological characteristics, such as accuracy (better than 1 °C), sensitivity (e.g., 10 pm·°C−1 for Fiber Bragg Gratings), and frequency response (hundreds of kHz), are adequate for this application; immunity to electromagnetic interference allows the use of FOSs during Magnetic Resonance- or Computed Tomography-guided thermal procedures. In this review the current status of the most used FOSs for temperature monitoring during thermal procedure (e.g., fiber Bragg Grating sensors; fluoroptic sensors) is presented, with emphasis placed on their working principles and metrological characteristics. The essential physics of the common ablation techniques are included to explain the advantages of using FOSs during these procedures. PMID:27455273

Fiber Optic Sensors for Temperature Monitoring during Thermal Treatments: An Overview

Directory of Open Access Journals (Sweden)

Emiliano Schena

2016-07-01

Full Text Available During recent decades, minimally invasive thermal treatments (i.e., Radiofrequency ablation, Laser ablation, Microwave ablation, High Intensity Focused Ultrasound ablation, and Cryo-ablation have gained widespread recognition in the field of tumor removal. These techniques induce a localized temperature increase or decrease to remove the tumor while the surrounding healthy tissue remains intact. An accurate measurement of tissue temperature may be particularly beneficial to improve treatment outcomes, because it can be used as a clear end-point to achieve complete tumor ablation and minimize recurrence. Among the several thermometric techniques used in this field, fiber optic sensors (FOSs have several attractive features: high flexibility and small size of both sensor and cabling, allowing insertion of FOSs within deep-seated tissue; metrological characteristics, such as accuracy (better than 1 °C, sensitivity (e.g., 10 pm·°C−1 for Fiber Bragg Gratings, and frequency response (hundreds of kHz, are adequate for this application; immunity to electromagnetic interference allows the use of FOSs during Magnetic Resonance- or Computed Tomography-guided thermal procedures. In this review the current status of the most used FOSs for temperature monitoring during thermal procedure (e.g., fiber Bragg Grating sensors; fluoroptic sensors is presented, with emphasis placed on their working principles and metrological characteristics. The essential physics of the common ablation techniques are included to explain the advantages of using FOSs during these procedures.

Insight into electronic mechanisms of nanosecond-laser ablation of silicon

International Nuclear Information System (INIS)

Marine, Wladimir; Patrone, Lionel; Ozerov, Igor; Bulgakova, Nadezhda M.

2008-01-01

We present experimental and theoretical studies of nanosecond ArF excimer laser desorption and ablation of silicon with insight into material removal mechanisms. The experimental studies involve a comprehensive analysis of the laser-induced plume dynamics and measurements of the charge gained by the target during irradiation time. At low laser fluences, well below the melting threshold, high-energy ions with a narrow energy distribution are observed. When the fluence is increased, a thermal component of the plume is formed superimposing on the nonthermal ions, which are still abundant. The origin of these ions is discussed on the basis of two modeling approaches, thermal and electronic, and we analyze the dynamics of silicon target excitation, heating, melting, and ablation. An electronic model is developed that provides insight into the charge-carrier transport in the target. We demonstrate that, contrary to a commonly accepted opinion, a complete thermalization between the electron and lattice subsystems is not reached during the nanosecond-laser pulse action. Moreover, the charging effects can retard the melting process and have an effect on the overall target behavior and laser-induced plume dynamics

Improving the ablation efficiency of excimer laser systems with higher repetition rates through enhanced debris removal and optimized spot pattern.

Science.gov (United States)

Arba-Mosquera, Samuel; Klinner, Thomas

2014-03-01

To evaluate the reasons for the required increased radiant exposure for higher-repetition-rate excimer lasers and determine experimentally possible compensations to achieve equivalent ablation profiles maintaining the same single-pulse energies and radiant exposures for laser repetition rates ranging from 430 to 1000 Hz. Schwind eye-tech-solutions GmbH and Co. KG, Kleinostheim, Germany. Experimental study. Poly(methyl methacrylate) (PMMA) plates were photoablated. The pulse laser energy was maintained during all experiments; the effects of the flow of the debris removal, the shot pattern for the correction, and precooling the PMMA plates were evaluated in terms of achieved ablation versus repetition rate. The mean ablation performance ranged from 88% to 100%; the variability between the profile measurements ranged from 1.4% to 6.2%. Increasing the laser repetition rate from 430 Hz to 1000 Hz reduced the mean ablation performance from 98% to 91% and worsened the variability from 1.9% to 4.3%. Increasing the flow of the debris removal, precooling the PMMA plates to -18°C, and adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the variability. Only adapting the shot pattern for the thermal response of PMMA to excimer ablation helped stabilize the mean ablation performance. The ablation performance of higher-repetition-rate excimer lasers on PMMA improved with improvements in the debris removal systems and shot pattern. More powerful debris removal systems and smart shot patterns in terms of thermal response improved the performance of these excimer lasers. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Polyimide-Foam/Aerogel Composites for Thermal Insulation

Science.gov (United States)

Williams, Martha; Fesmire, James; Sass, Jared; Smith, Trent; Weoser. Erol

2009-01-01

Composites of specific types of polymer foams and aerogel particles or blankets have been proposed to obtain thermal insulation performance superior to those of the neat polyimide foams. These composites have potential to also provide enhanced properties for vibration dampening or acoustic attenuation. The specific type of polymer foam is denoted "TEEK-H", signifying a series, denoted H, within a family of polyimide foams that were developed at NASA s Langley Research Center and are collectively denoted TEEK (an acronym of the inventors names). The specific types of aerogels include Nanogel aerogel particles from Cabot Corporation in Billerica, MA. and of Spaceloft aerogel blanket from Aspen Aerogels in Northborough, MA. The composites are inherently flame-retardant and exceptionally thermally stable. There are numerous potential uses for these composites, at temperatures from cryogenic to high temperatures, in diverse applications that include aerospace vehicles, aircraft, ocean vessels, buildings, and industrial process equipment. Some low-temperature applications, for example, include cryogenic storage and transfer or the transport of foods, medicines, and chemicals. Because of thermal cycling, aging, and weathering most polymer foams do not perform well at cryogenic temperatures and will undergo further cracking over time. The TEEK polyimides are among the few exceptions to this pattern, and the proposed composites are intended to have all the desirable properties of TEEK-H foams, plus improved thermal performance along with enhanced vibration or acoustic-attenuation performance. A composite panel as proposed would be fabricated by adding an appropriate amount of TEEK friable balloons into a mold to form a bottom layer. A piece of flexible aerogel blanket material, cut to the desired size and shape, would then be placed on the bottom TEEK layer and sandwiched between another top layer of polyimide friable balloons so that the aerogel blanket would become

[Balloon cell nevi of the conjunctiva (author's transl)].

Science.gov (United States)

Schlageter, P E; Daicker, B

1975-06-01

The clinical and histological features of three cases of conjunctival balloon cell nevi are described. This peculiar form of nevus is very rare in the conjunctiva. The findings are compared with the descriptions in the literature of dermal balloon cell nevi. They demonstrate, that the conjunctival and dermal tumours are of idential histological structure. The proliferations of the conjunctival epithelium often found in conjunctival nevi do not modify the balloon cell nevi. These can not be diagnosed clinically. The problems of the pathogenesis of the balloon cell nevi are discussed.

Simulating clefts in pumpkin balloons

Science.gov (United States)

Baginski, Frank; Brakke, Kenneth

2010-02-01

The geometry of a large axisymmetric balloon with positive differential pressure, such as a sphere, leads to very high film stresses. These stresses can be significantly reduced by using a tendon re-enforced lobed pumpkin-like shape. A number of schemes have been proposed to achieve a cyclically symmetric pumpkin shape, including the constant bulge angle (CBA) design, the constant bulge radius (CBR) design, CBA/CBR hybrids, and NASA’s recent constant stress (CS) design. Utilizing a hybrid CBA/CBR pumpkin design, Flight 555-NT in June 2006 formed an S-cleft and was unable to fully deploy. In order to better understand the S-cleft phenomenon, a series of inflation tests involving four 27-m diameter 200-gore pumpkin balloons were conducted in 2007. One of the test vehicles was a 1/3-scale mockup of the Flight 555-NT balloon. Using an inflation procedure intended to mimic ascent, the 1/3-scale mockup developed an S-cleft feature strikingly similar to the one observed in Flight 555-NT. Our analysis of the 1/3-scale mockup found it to be unstable. We compute asymmetric equilibrium configurations of this balloon, including shapes with an S-cleft feature.

TU-B-210-01: MRg HIFU - Bone and Soft Tissue Tumor Ablation

International Nuclear Information System (INIS)

Ghanouni, P.

2015-01-01

MR guided focused ultrasound (MRgFUS), or alternatively high-intensity focused ultrasound (MRgHIFU), is approved for thermal ablative treatment of uterine fibroids and pain palliation in bone metastases. Ablation of malignant tumors is under active investigation in sites such as breast, prostate, brain, liver, kidney, pancreas, and soft tissue. Hyperthermia therapy with MRgFUS is also feasible, and may be used in conjunction with radiotherapy and for local targeted drug delivery. MRI allows in situ target definition and provides continuous temperature monitoring and subsequent thermal dose mapping during HIFU. Although MRgHIFU can be very precise, treatment of mobile organs is challenging and advanced techniques are required because of artifacts in MR temperature mapping, the need for intercostal firing, and need for gated HIFU or tracking of the lesion in real time. The first invited talk, “MR guided Focused Ultrasound Treatment of Tumors in Bone and Soft Tissue”, will summarize the treatment protocol and review results from treatment of bone tumors. In addition, efforts to extend this technology to treat both benign and malignant soft tissue tumors of the extremities will be presented. The second invited talk, “MRI guided High Intensity Focused Ultrasound – Advanced Approaches for Ablation and Hyperthermia”, will provide an overview of techniques that are in or near clinical trials for thermal ablation and hyperthermia, with an emphasis of applications in abdominal organs and breast, including methods for MRTI and tracking targets in moving organs. Learning Objectives: Learn background on devices and techniques for MR guided HIFU for cancer therapy Understand issues and current status of clinical MRg HIFU Understand strategies for compensating for organ movement during MRgHIFU Understand strategies for strategies for delivering hyperthermia with MRgHIFU CM - research collaboration with Philips

TU-B-210-02: MRg HIFU - Advanced Approaches for Ablation and Hyperthermia

Energy Technology Data Exchange (ETDEWEB)

Moonen, C. [University Medical Center Utrecht (Netherlands)

2015-06-15

MR guided focused ultrasound (MRgFUS), or alternatively high-intensity focused ultrasound (MRgHIFU), is approved for thermal ablative treatment of uterine fibroids and pain palliation in bone metastases. Ablation of malignant tumors is under active investigation in sites such as breast, prostate, brain, liver, kidney, pancreas, and soft tissue. Hyperthermia therapy with MRgFUS is also feasible, and may be used in conjunction with radiotherapy and for local targeted drug delivery. MRI allows in situ target definition and provides continuous temperature monitoring and subsequent thermal dose mapping during HIFU. Although MRgHIFU can be very precise, treatment of mobile organs is challenging and advanced techniques are required because of artifacts in MR temperature mapping, the need for intercostal firing, and need for gated HIFU or tracking of the lesion in real time. The first invited talk, “MR guided Focused Ultrasound Treatment of Tumors in Bone and Soft Tissue”, will summarize the treatment protocol and review results from treatment of bone tumors. In addition, efforts to extend this technology to treat both benign and malignant soft tissue tumors of the extremities will be presented. The second invited talk, “MRI guided High Intensity Focused Ultrasound – Advanced Approaches for Ablation and Hyperthermia”, will provide an overview of techniques that are in or near clinical trials for thermal ablation and hyperthermia, with an emphasis of applications in abdominal organs and breast, including methods for MRTI and tracking targets in moving organs. Learning Objectives: Learn background on devices and techniques for MR guided HIFU for cancer therapy Understand issues and current status of clinical MRg HIFU Understand strategies for compensating for organ movement during MRgHIFU Understand strategies for strategies for delivering hyperthermia with MRgHIFU CM - research collaboration with Philips.

TU-B-210-01: MRg HIFU - Bone and Soft Tissue Tumor Ablation

Energy Technology Data Exchange (ETDEWEB)

Ghanouni, P. [Stanford University (United States)

2015-06-15

MR guided focused ultrasound (MRgFUS), or alternatively high-intensity focused ultrasound (MRgHIFU), is approved for thermal ablative treatment of uterine fibroids and pain palliation in bone metastases. Ablation of malignant tumors is under active investigation in sites such as breast, prostate, brain, liver, kidney, pancreas, and soft tissue. Hyperthermia therapy with MRgFUS is also feasible, and may be used in conjunction with radiotherapy and for local targeted drug delivery. MRI allows in situ target definition and provides continuous temperature monitoring and subsequent thermal dose mapping during HIFU. Although MRgHIFU can be very precise, treatment of mobile organs is challenging and advanced techniques are required because of artifacts in MR temperature mapping, the need for intercostal firing, and need for gated HIFU or tracking of the lesion in real time. The first invited talk, “MR guided Focused Ultrasound Treatment of Tumors in Bone and Soft Tissue”, will summarize the treatment protocol and review results from treatment of bone tumors. In addition, efforts to extend this technology to treat both benign and malignant soft tissue tumors of the extremities will be presented. The second invited talk, “MRI guided High Intensity Focused Ultrasound – Advanced Approaches for Ablation and Hyperthermia”, will provide an overview of techniques that are in or near clinical trials for thermal ablation and hyperthermia, with an emphasis of applications in abdominal organs and breast, including methods for MRTI and tracking targets in moving organs. Learning Objectives: Learn background on devices and techniques for MR guided HIFU for cancer therapy Understand issues and current status of clinical MRg HIFU Understand strategies for compensating for organ movement during MRgHIFU Understand strategies for strategies for delivering hyperthermia with MRgHIFU CM - research collaboration with Philips.

Comparison of wet radiofrequency ablation with dry radiofrequency ablation and radiofrequency ablation using hypertonic saline preinjection: ex vivo bovine liver

International Nuclear Information System (INIS)

Lee, Jeong Min; Han, Joon Koo; Kim, Se Hyung; Lee, Jae Young; Park, Hee Sun; Hur, Hurn; Choi, Byung Ihn; Shin, Kyung Sook

2004-01-01

We wished to compare the in-vitro efficiency of wet radiofrequency (RF) ablation with the efficiency of dry RF ablation and RF ablation with preinjection of NaCl solutions using excised bovine liver. Radiofrequency was applied to excised bovine livers in a monopolar mode for 10 minutes using a 200 W generator and a perfused-cooled electrode with or without injection or slow infusion of NaCl solutions. After placing the perfused-cooled electrode in the explanted liver, 50 ablation zones were created with five different regimens: group A; standard dry RF ablation, group B; RF ablation with 11 mL of 5% NaCl solution preinjection, group C; RF ablation with infusion of 11 mL of 5% NaCl solution at a rate of 1 mL/min, group D; RFA with 6 mL of 36% NaCl solution preinjection, group E; RF ablation with infusion of 6 mL of 36% NaCl solution at a rate of 0.5 mL/min. In groups C and E, infusion of the NaCl solutions was started 1 min before RF ablation and then maintained during RF ablation (wet RF ablation). During RF ablation, we measured the tissue temperature at 15 mm from the electrode. The dimensions of the ablation zones and changes in impedance, current and liver temperature during RF ablation were then compared between the groups. With injection or infusion of NaCl solutions, the mean initial tissue impedance prior to RF ablation was significantly less in groups B, C, D, and E (43-75 Ω) than for group A (80 Ω) (ρ 3 in group A; 12.4 ± 3.8 cm 3 in group B; 80.9 ± 9.9 cm 3 in group C; 45.3 ± 11.3 cm 3 in group D and 81.6 ± 8.6 cm 3 in group E. The tissue temperature measured at 15 mm from the electrode was higher in groups C, D and E than other groups (ρ < 0.05): 53 ± 12 .deg. C in group A, 42 ± 2 .deg. C in group B, 93 ± 8 .deg. C in group C; 79 ± 12 .deg. C in group D and 83 ± 8 .deg.C in group E. Wet RF ablation with 5% or 36% NaCl solutions shows better efficiency in creating a large ablation zone than does dry RF ablation or RF ablation with

Thermal modelling using discrete vasculature for thermal therapy: A review

NARCIS (Netherlands)

Kok, H. Petra; Gellermann, Johanna; van den Berg, Cornelis A. T.; Stauffer, Paul R.; Hand, Jeffrey W.; Crezee, Johannes

2013-01-01

Reliable temperature information during clinical hyperthermia and thermal ablation is essential for adequate treatment control, but conventional temperature measurements do not provide 3D temperature information. Treatment planning is a very useful tool to improve treatment quality, and substantial

Magnetic resonance–guided interstitial high-intensity focused ultrasound for brain tumor ablation

Science.gov (United States)

MacDonell, Jacquelyn; Patel, Niravkumar; Rubino, Sebastian; Ghoshal, Goutam; Fischer, Gregory; Burdette, E. Clif; Hwang, Roy; Pilitsis, Julie G.

2018-01-01

Currently, treatment of brain tumors is limited to resection, chemotherapy, and radiotherapy. Thermal ablation has been recently explored. High-intensity focused ultrasound (HIFU) is being explored as an alternative. Specifically, the authors propose delivering HIFU internally to the tumor with an MRI-guided robotic assistant (MRgRA). The advantage of the authors’ interstitial device over external MRI-guided HIFU (MRgHIFU) is that it allows for conformal, precise ablation and concurrent tissue sampling. The authors describe their workflow for MRgRA HIFU delivery. PMID:29385926

Identification of photoacoustic transients during pulsed laser ablation of the human temporal bone: an experimental model.

Science.gov (United States)

Wong, B J; Dickinson, M R; Berns, M W; Neev, J

1996-12-01

Laser ablation of hard tissues during neurotologic operations has been accomplished with continuous-wave (CW) lasers in the visible and midinfrared spectrum. The mechanism of ablation at these wavelengths is secondary to photothermal-induced tissue destruction. As a result, significant thermal damage to surrounding tissue may occur. Pulsed ultraviolet (UV) lasers have been suggested as an alternative to the argon, KTP-532, and CO2 lasers currently used in clinical practice. The pulse length of Excimer lasers are considerably shorter than the thermal diffusion time of bone tissue, and as a consequence thermal injury is minimal. This makes pulsed lasers an attractive tool for tissue ablation in the ear: in essence a "cold knife." However, the short pulse width of Excimer lasers (typically 10-150 ns) can create large thermoelastic stresses in the ablation specimen. This study identifies the presence of these photoacoustic waves during the Excimer laser treatment of the cadaveric human temporal bone. A XeCl (lambda = 308 nm, tau p = 12 ns) excimer laser was used to ablate hard tissue surrounding the oval window and facial ridge with energies of 75, 45, 25, and 12 mJ/pulse. Spot size was estimated to be 0.5 mm2. Custom high-frequency polyvinyldifluoride (PVDF) piezoelectric film transducers were fabricated and attached to the promontory, round window niche, and facial ridges. The signals were amplified using a low-noise preamplifier and recorded on a digitizing oscilloscope. Photoacoustic waves were clearly identified. Notably, large acoustic waves were measured on the promontory and on both sides of the facial ridge. The implications and clinical relevance of these findings is discussed and compared to findings obtained from a model system.

Radiofrequency Ablation Treatment for Renal Cell Carcinoma: Early Clinical Experience

Energy Technology Data Exchange (ETDEWEB)

Park, Seong Hoon; Yoon, Seong Kuk; Cho, Jin Han; Oh, Jong Young; Nam, Kyung Jin; Kwon, Hee Jin; Kim, Su Yeon; Kang, Myong Jin; Choi, Sun Seob; Sung, Gyung Tak [Dong-A University College of Medicine, Busan (Korea, Republic of)

2008-08-15

To evaluate the early clinical experience associated with radiofrequency (RF) ablation in patients with renal cell carcinoma (RCC). The RF ablation treatment was performed on 17 tumors from 16 patients (mean age, 60.5 years; range, 43 73 years) with RCC. The treatment indications were localized, solid renal mass, comorbidities, high operation risk, and refusal to perform surgery. All tumors were treated by a percutaneous CT (n = 10), followed by an US-guided (n = 2), laparoscopy-assisted US (n = 2), and an open (n = 2) RF ablation. Furthermore, patients underwent a follow- up CT at one day, one week, one month, three and six months, and then every six months from the onset of treatment. We evaluated the technical success, technical effectiveness, ablation zone, benign periablation enhancement, irregular peripheral enhancement, and complications. All 17 exophytic tumors (mean size, 2.2 cm; range, 1.1 5.0 cm) were completely ablated. Technical success and effectiveness was achieved in all cases and the mean follow-up period was 23.8 months (range, 17 33 months). A local recurrence was not detected in any of the cases; however, five patients developed complications as a result of treatment, including hematuria (n = 2), mild thermal injury of the psoas muscle (n = 1), mild hydronephrosis (n = 1), and fistula formation (n = 1). The RF ablation is an alternative treatment for exophytic RCCs and represents a promising treatment for some patients with small RCCs.

Radiofrequency Ablation Treatment for Renal Cell Carcinoma: Early Clinical Experience

International Nuclear Information System (INIS)

Park, Seong Hoon; Yoon, Seong Kuk; Cho, Jin Han; Oh, Jong Young; Nam, Kyung Jin; Kwon, Hee Jin; Kim, Su Yeon; Kang, Myong Jin; Choi, Sun Seob; Sung, Gyung Tak

2008-01-01

To evaluate the early clinical experience associated with radiofrequency (RF) ablation in patients with renal cell carcinoma (RCC). The RF ablation treatment was performed on 17 tumors from 16 patients (mean age, 60.5 years; range, 43 73 years) with RCC. The treatment indications were localized, solid renal mass, comorbidities, high operation risk, and refusal to perform surgery. All tumors were treated by a percutaneous CT (n = 10), followed by an US-guided (n = 2), laparoscopy-assisted US (n = 2), and an open (n = 2) RF ablation. Furthermore, patients underwent a follow- up CT at one day, one week, one month, three and six months, and then every six months from the onset of treatment. We evaluated the technical success, technical effectiveness, ablation zone, benign periablation enhancement, irregular peripheral enhancement, and complications. All 17 exophytic tumors (mean size, 2.2 cm; range, 1.1 5.0 cm) were completely ablated. Technical success and effectiveness was achieved in all cases and the mean follow-up period was 23.8 months (range, 17 33 months). A local recurrence was not detected in any of the cases; however, five patients developed complications as a result of treatment, including hematuria (n = 2), mild thermal injury of the psoas muscle (n = 1), mild hydronephrosis (n = 1), and fistula formation (n = 1). The RF ablation is an alternative treatment for exophytic RCCs and represents a promising treatment for some patients with small RCCs

MR-Guided Laser Ablation of Osteoid Osteoma in an Open High-Field System (1.0 T)

International Nuclear Information System (INIS)

Streitparth, F.; Gebauer, B.; Melcher, I.; Schaser, K.; Philipp, C.; Rump, J.; Hamm, B.; Teichgraeber, U.

2009-01-01

Computed tomography is the standard imaging modality to minimize the extent of surgical or ablative treatment in osteoid osteomas. In the last 15 years, since a description of thermal ablation of osteoid osteomas was first published, this technique has become a treatment of choice for this tumor. We report the case of a 20-year-old man with an osteoid osteoma treated with laser ablation in an open high-field magnetic resonance imaging scanner (1.0 T). The tumor, located in the right fibula, was safely and effectively ablated under online monitoring. We describe the steps of this interventional procedure and discuss related innovative guidance and monitoring features and potential benefits compared with computed tomographic guidance.

Retained intraaortic balloon. Case report and review of the literature.

Science.gov (United States)

Grande, A M; Martinelli, L; Graffigna, A; Viganò, M

1995-01-01

We report a case of intraaortic balloon entrapment in a 70-year-old man who underwent emergency triple coronary bypass. Intraaortic balloon rupture caused the formation of a clot inside the balloon that eventually was responsible for the balloon's entrapment at the aortic bifurcation. The patient had severe atherosclerosis of the aorta and iliac arteries. Balloon removal required aorto-iliac exposure and aorto-bifemoral bypass. After 16 months, he is symptom free and at home.

Upper gastrointestinal strictures: The results of balloon dilatation

Energy Technology Data Exchange (ETDEWEB)

Lee, Kil Woo; Lim, Hyo Keun; Choo, In Wook; Bae, Sang Hoon; Yoon, Jong Sup [Hallym University College of Medicine, Seoul (Korea, Republic of); Yoo, Hyung Sik [Yonsei University College of Medicine, Seoul (Korea, Republic of)

1990-12-15

Balloon catheter dilatation of upper gastrointestinal strictures is an accepted mode of therapy. The authors report the balloon dilatation in 11 consecutive patients. The lesions treated included 10 benign strictures, and 1 esophageal cancer. Esophageal balloon were ranged from 2 mm in diameter, 4 cm in length, to 30 mm in diameter, 8 cm in length. Inflation was held for from 30 to 60 seconds and then repeated two or three times during each session. The balloons were inflated to pressure of from 2 to 12 atmospheres. There were from 1 to 13 dilatations. Two esophageal perforations were occurred in one esophagitis patient and other lye stricture patient. Two perforations were not required any surgical repair. All dilatation were performed without anesthesia. All strictures were responded immediately to dilatation. Prolonged course of treatment were needed with chronic severe esophagitis, lye stricture, gastrojejunostomy with chemotherapy, as a result, all patients, except esophageal cancer, could take regular diet after balloon catheter dilatation. Balloon catheter dilatation of upper gastrointestinal stenosis was effective and safe. It should be considered before other methods of treatment applicable.

Percutaneous balloon dilation of pulmonary stenosis

International Nuclear Information System (INIS)

Hua Yangde; Huang Ming; Li Jinkang; Qian Jinqing; Chen Xiuyu; Yang Siyuan

2003-01-01

Objective: Review our experience of balloon dilation of valvular pulmonary stenosis in 32 cases. Methods: Totally 32 cases of pulmonary stenosis admitted from 1995-2001 with age of 1.5-13 yrs mean 6.8. Diagnosis was made by clinical manifestations, EKG, ECHO and angiocardiography. Results: Before dilation, the mean systolic pressure of right ventricle was (93.5 ± 28.5) mmHg, after the procedure it reduced to (42 ± 9.0) mmHg. The pressure gradient between right ventricle and pulmonary artery before dilation was (76 ± 30) mmHg and become (24.5 ± 8.5) mmHg after dilation. The gradient pressure after dilation was less than 25 mmHg in 90.6% cases. A case of Noonan syndrome showed no response to balloon dilation and died during valvulectomy from accompanying left ventricular cardiomyopathy. Conclusions: Balloon dilation of valvular pulmonary stenosis is effective and safe. The selection of proper diameter of pulmonary valvular rings and sized of the balloon are the major factors

Stability of the pumpkin balloon

Science.gov (United States)

Baginski, Frank

A large axisymmetric balloon with positive differential pressure, e.g., a sphere, leads to high film stresses. These can be significantly reduced by using a lobed pumpkin-like shape re-enforced with tendons. A number of schemes have been proposed to achieve a cyclically symmetric pumpkin-shape at full inflation, including the constant bulge angle (CBA) design and the constant bulge radius (CBR) design. The authors and others have carried out stability studies of CBA and CBR designs and found instabilities under various conditions. While stability seems to be a good indicator of deployment problems for large balloons under normal ascent conditions, one cannot conclude that a stable design will deploy reliably. Nevertheless, stability analysis allows one to quantify certain deployment characteristics. Ongoing research by NASA's Balloon Program Office utilizes a new design approach developed by Rodger Farley, NASA/GSFC, that takes into account film and tendon strain. We refer to such a balloon as a constant stress (CS) pumpkin design. In June 2006, the Flight 555-NT balloon (based on a hybrid CBR/CBA design) developed an S-cleft and did not deploy. In order to understand the S-cleft phenomena and study a number of aspects related to the CS-design, a series of inflation tests were conducted at TCOM, Elizabeth City, NC in 2007. The test vehicles were 27 meter diameter pumpkins distinguished by their respective equatorial bulge angles (BA). For example, BA98 indicates an equatorial bulge angle of 98° . BA90, BA55, and BA00 are similarly defined. BA98 was essentially a one-third scale version of of the Flight 555 balloon (i.e., 12 micron film instead of 38.1 micron, mini-tendons, etc.). BA90 and BA55 were Farley CS-designs. BA00 was derived from the BA55 design so that a flat chord spanned adjacent tendons. In this paper, we will carry out stability studies of BA98, BA90, BA55, and BA00. We discuss the deployment problem of pumpkin balloons in light of 2007 inflation

Balloon dilatation of ureteric strictures.

Directory of Open Access Journals (Sweden)

Punekar S

2000-01-01

Full Text Available AIMS: Evaluation of dilatation as a minimally invasive technique for the treatment of ureteric strictures. MATERIAL AND METHODS: We evaluated this technique in 16 patients with ureteric and secondary pelviureteric junction strictures from June 1998. Of these, 7 were men and 9 were women. The age range was from 14 to 40 years. RESULTS: Balloon dilatation was successful in 69% of patients. Strictures secondary to previous surgery had nearly 100% success. Of the 8 cases diagnosed as genitourinary tuberculosis, success rate was 50%. CONCLUSIONS: Factors affecting success of balloon dilatation are: a age of the stricture b length of the stricture and c etiology of the stricture. In a select group of patients with fresh post-operative or post-inflammatory strictures, balloon dilatation may be an attractive alternative to surgery.

Nanosecond laser ablation processes in aluminum-doped zinc-oxide for photovoltaic devices

Energy Technology Data Exchange (ETDEWEB)

Canteli, D., E-mail: david.canteli@ciemat.es [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain); Fernandez, S. [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain); Molpeceres, C. [Centro Laser, Universidad Politecnica de Madrid, Ctra. de Valencia Km 7.3, 28031 Madrid (Spain); Torres, I.; Gandia, J.J. [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain)

2012-09-15

Highlights: Black-Right-Pointing-Pointer A study of the ablation of AZO thin films deposited at different temperature conditions with nanosecond UV laser light for photovoltaic devices has been performed. Black-Right-Pointing-Pointer The ablation threshold of AZO thin films was measured and related with the absorption coefficient of the films at the laser wavelength, showing a direct correspondence. Black-Right-Pointing-Pointer A change in the material structure in the areas closest to the edges of laser grooves made in samples deposited at temperatures below 100 Degree-Sign C was observed and studied. - Abstract: Aiming to a future use in thin film solar modules, the processing of aluminum doped zinc oxide thin films with good optoelectronic properties with a nanosecond-pulsed ultraviolet laser has been studied. The ablation threshold fluence of the films has been determined and associated with the material properties. The ablation process has been optimized and grooves with good properties for photovoltaic devices have been obtained. The morphology of the ablated surfaces has been observed by confocal microscopy and its structure has been characterized by Raman spectroscopy. The influence of ablation parameters like focus distance, pulse energy and repetition frequency in the groove morphology has been studied with special attention to the thermal effects on the material structure.

Nanosecond laser ablation processes in aluminum-doped zinc-oxide for photovoltaic devices

International Nuclear Information System (INIS)

Canteli, D.; Fernandez, S.; Molpeceres, C.; Torres, I.; Gandía, J.J.

2012-01-01

Highlights: ► A study of the ablation of AZO thin films deposited at different temperature conditions with nanosecond UV laser light for photovoltaic devices has been performed. ► The ablation threshold of AZO thin films was measured and related with the absorption coefficient of the films at the laser wavelength, showing a direct correspondence. ► A change in the material structure in the areas closest to the edges of laser grooves made in samples deposited at temperatures below 100 °C was observed and studied. - Abstract: Aiming to a future use in thin film solar modules, the processing of aluminum doped zinc oxide thin films with good optoelectronic properties with a nanosecond-pulsed ultraviolet laser has been studied. The ablation threshold fluence of the films has been determined and associated with the material properties. The ablation process has been optimized and grooves with good properties for photovoltaic devices have been obtained. The morphology of the ablated surfaces has been observed by confocal microscopy and its structure has been characterized by Raman spectroscopy. The influence of ablation parameters like focus distance, pulse energy and repetition frequency in the groove morphology has been studied with special attention to the thermal effects on the material structure.

Potassium titanyl phosphate laser tissue ablation: development and experimental validation of a new numerical model.

Science.gov (United States)

Elkhalil, Hossam; Akkin, Taner; Pearce, John; Bischof, John

2012-10-01

The photoselective vaporization of prostate (PVP) green light (532 nm) laser is increasingly being used as an alternative to the transurethral resection of prostate (TURP) for treatment of benign prostatic hyperplasia (BPH) in older patients and those who are poor surgical candidates. In order to achieve the goals of increased tissue removal volume (i.e., "ablation" in the engineering sense) and reduced collateral thermal damage during the PVP green light treatment, a two dimensional computational model for laser tissue ablation based on available parameters in the literature has been developed and compared to experiments. The model is based on the control volume finite difference and the enthalpy method with a mechanistically defined energy necessary to ablate (i.e., physically remove) a volume of tissue (i.e., energy of ablation E(ab)). The model was able to capture the general trends experimentally observed in terms of ablation and coagulation areas, their ratio (therapeutic index (TI)), and the ablation rate (AR) (mm(3)/s). The model and experiment were in good agreement at a smaller working distance (WD) (distance from the tissue in mm) and a larger scanning speed (SS) (laser scan speed in mm/s). However, the model and experiment deviated somewhat with a larger WD and a smaller SS; this is most likely due to optical shielding and heat diffusion in the laser scanning direction, which are neglected in the model. This model is a useful first step in the mechanistic prediction of PVP based BPH laser tissue ablation. Future modeling efforts should focus on optical shielding, heat diffusion in the laser scanning direction (i.e., including 3D effects), convective heat losses at the tissue boundary, and the dynamic optical, thermal, and coagulation properties of BPH tissue.

The spectrum of laser skin resurfacing: nonablative, fractional, and ablative laser resurfacing.

Science.gov (United States)

Alexiades-Armenakas, Macrene R; Dover, Jeffrey S; Arndt, Kenneth A

2008-05-01

The drive to attain cosmetic facial enhancement with minimal risk and rapid recovery has inspired the field of nonsurgical skin rejuvenation. Laser resurfacing was introduced in the 1980s with continuous wave carbon dioxide (CO(2)) lasers; however, because of a high rate of side effects, including scarring, short-pulse, high-peak power, and rapidly scanned, focused-beam CO(2) lasers and normal-mode erbium-doped yttrium aluminium garnet lasers were developed, which remove skin in a precisely controlled manner. The prolonged 2-week recovery time and small but significant complication risk prompted the development of non-ablative and, more recently, fractional resurfacing in order to minimize risk and shorten recovery times. Nonablative resurfacing produces dermal thermal injury to improve rhytides and photodamage while preserving the epidermis. Fractional resurfacing thermally ablates microscopic columns of epidermal and dermal tissue in regularly spaced arrays over a fraction of the skin surface. This intermediate approach increases efficacy as compared to nonablative resurfacing, but with faster recovery as compared to ablative resurfacing. Neither nonablative nor fractional resurfacing produces results comparable to ablative laser skin resurfacing, but both have become much more popular than the latter because the risks of treatment are limited in the face of acceptable improvement. At the completion of this learning activity, participants should be familiar with the spectrum of lasers and light technologies available for skin resurfacing, published studies of safety and efficacy, indications, methodologies, side effects, complications, and management.

Synthesis and characterization of a novel laser ablation sensitive triazene incorporated epoxy resin

KAUST Repository

Patole, Archana S.; Hyeon, Jeong min; Hyun, Jung Mn; Kim, Tae Ho; Patole, Shashikant P.; Hong, Dae Jo; Lee, Chang Bo; Choi, Cheol Ho

2014-01-01

. Thermogravimetrical investigations indicate the loss of nitrogen being the initial thermal decomposition step and exhibit sufficient stabilities for the requirements for laser ablation application. Fourier transform infra-red, nuclear magnetic resonance, and gas

Ablation Behavior of Plasma-Sprayed La1-xSrxTiO3+δ Coating Irradiated by High-Intensity Continuous Laser.

Science.gov (United States)

Zhu, Jinpeng; Ma, Zhuang; Gao, Yinjun; Gao, Lihong; Pervak, Vladimir; Wang, Lijun; Wei, Chenghua; Wang, Fuchi

2017-10-11

Laser protection for optical components, particularly those in high-power laser systems, has been a major concern. La 1-x Sr x TiO 3+δ with its good optical and thermal properties can be potentially applied as a high-temperature optical protective coating or high-reflectivity material for optical components. However, the high-power laser ablation behavior of plasma-sprayed La 1-x Sr x TiO 3+δ (x = 0.1) coatings has rarely been investigated. Thus, in this study, laser irradiation experiments were performed to study the effect of high-intensity continuous laser on the ablation behavior of the La 1-x Sr x TiO 3+δ coating. The results show that the La 1-x Sr x TiO 3+δ coating undergoes three ablation stages during laser irradiation: coating oxidation, formation and growth of new structures (columnar and dendritic crystals), and mechanical failure. A finite-element simulation was also conducted to explore the mechanism of the ablation damage to the La 1-x Sr x TiO 3+δ coating and provided a good understanding of the ablation behavior. The apparent ablation characteristics are attributed to the different temperature gradients determined by the reflectivity and thermal diffusivity of the La 1-x Sr x TiO 3+δ coating material, which are critical factors for improving the antilaser ablation property. Now, the stainless steel substrate deposited by it can effectively work as a protective shield layer against ablation by laser irradiation.

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

Science.gov (United States)

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

2017-04-01

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

Steady state model for the thermal regimes of shells of airships and hot air balloons

Science.gov (United States)

Luchev, Oleg A.

1992-10-01

A steady state model of the temperature regime of airships and hot air balloons shells is developed. The model includes three governing equations: the equation of the temperature field of airships or balloons shell, the integral equation for the radiative fluxes on the internal surface of the shell, and the integral equation for the natural convective heat exchange between the shell and the internal gas. In the model the following radiative fluxes on the shell external surface are considered: the direct and the earth reflected solar radiation, the diffuse solar radiation, the infrared radiation of the earth surface and that of the atmosphere. For the calculations of the infrared external radiation the model of the plane layer of the atmosphere is used. The convective heat transfer on the external surface of the shell is considered for the cases of the forced and the natural convection. To solve the mentioned set of the equations the numerical iterative procedure is developed. The model and the numerical procedure are used for the simulation study of the temperature fields of an airship shell under the forced and the natural convective heat transfer.

Synthesis and characterization of a novel laser ablation sensitive triazene incorporated epoxy resin

KAUST Repository

Patole, Archana S.

2014-01-01

New triazene monomer was synthesized and further employed as a crosslinking agent partner with epoxy matrix using ethyl methyl imidazole as a curing agent in order to investigate the effect of triazene moieties on polymeric properties for laser ablation application. The synthesized triazene monomer was characterized by analytical and spectroscopic methods, while the surface morphology of resist after laser ablation was visualized by optical laser scanning images and scanning electron microscopy. Thermogravimetrical investigations indicate the loss of nitrogen being the initial thermal decomposition step and exhibit sufficient stabilities for the requirements for laser ablation application. Fourier transform infra-red, nuclear magnetic resonance, and gas chromatography analyses showed the successful synthesis of triazene. The ablation results from the optical laser scanning images revealed that the etching depth could be controlled by varying the concentration of triazene monomer in the formulation of epoxy. The shear strength analysis revealed that that the shear strength increased with increasing the amount of triazene in the formulation of direct ablation sensitive resist. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

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

Science.gov (United States)

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

2011-01-17

The main goal of this investigation was to develop and test a new method of treatment for human hepatocellular carcinoma (HCC). We present a method of carbon nanotube-enhanced laser thermal ablation of HepG2 cells (human hepatocellular liver carcinoma cell line) based on a simple multiwalled carbon nanotube (MWCNT) carrier system, such as human serum albumin (HSA), and demonstrate its selective therapeutic efficacy compared with normal hepatocyte cells. Both HepG2 cells and hepatocytes were treated with HSA-MWCNTs at various concentrations and at various incubation times and further irradiated using a 2 W, 808 nm laser beam. Transmission electron, phase contrast, and confocal microscopy combined with immunochemical staining were used to demonstrate the selective internalization of HSA-MWCNTs via Gp60 receptors and the caveolin-mediated endocytosis inside HepG2 cells. The postirradiation apoptotic rate of HepG2 cells treated with HSA-MWCNTs ranged from 88.24% (for 50 mg/L) at 60 sec to 92.34% (for 50 mg/L) at 30 min. Significantly lower necrotic rates were obtained when human hepatocytes were treated with HSA-MWCNTs in a similar manner. Our results clearly show that HSA-MWCNTs selectively attach on the albondin (aka Gp60) receptor located on the HepG2 membrane, followed by an uptake through a caveolin-dependent endocytosis process. These unique results may represent a major step in liver cancer treatment using nanolocalized thermal ablation by laser heating.

Ablation mass features in multi-pulses femtosecond laser ablate molybdenum target

Science.gov (United States)

Zhao, Dongye; Gierse, Niels; Wegner, Julian; Pretzler, Georg; Oelmann, Jannis; Brezinsek, Sebastijan; Liang, Yunfeng; Neubauer, Olaf; Rasinski, Marcin; Linsmeier, Christian; Ding, Hongbin

2018-03-01

In this study, the ablation mass features related to reflectivity of bulk Molybdenum (Mo) were investigated by a Ti: Sa 6 fs laser pulse at central wavelength 790 nm. The ablated mass removal was determined using Confocal Microscopy (CM) technique. The surface reflectivity was calibrated and measured by a Lambda 950 spectrophotometer as well as a CCD camera during laser ablation. The ablation mass loss per pulse increase with the increasing of laser shots, meanwhile the surface reflectivity decrease. The multi-pulses (100 shots) ablation threshold of Mo was determined to be 0.15 J/cm2. The incubation coefficient was estimated as 0.835. The reflectivity change of the Mo target surface following multi-pulses laser ablation were studied as a function of laser ablation shots at various laser fluences from 1.07 J/cm2 to 36.23 J/cm2. The results of measured reflectivity indicate that surface reflectivity of Mo target has a significant decline in the first 3-laser pulses at the various fluences. These results are important for developing a quantitative analysis model for laser induced ablation and laser induced breakdown spectroscopy for the first wall diagnosis of EAST tokamak.

Properties of ballooning modes in the Heliotron configurations

International Nuclear Information System (INIS)

Nakajima, N.; Hudson, S.R.; Hegna, C.C.

2005-01-01

The stability of ballooning modes is influenced by the local and global magnetic shear and local and global magnetic curvature so significantly that it is fairly difficult to get those general properties in the three dimensional configurations with strong flexibility due to the external coil system. In the case of the planar axis heliotron configurations allowing a large Shafranov shift, like LHD, properties of the high-mode-number ballooning modes have been intensively investigated. It has been analytically shown that the local magnetic shear comes to disappear in the stellarator-like global magnetic shear region, as the Shafranov shift becomes large. Based on this mechanism and the characteristics of the local and global magnetic curvature, it is numerically shown that the destabilized ballooning modes have strong three-dimensional properties (both poloidal and toroidal mode couplings) in the Mercier stable region, and that those are fairly similar to ballooning modes in the axisymmetric system in the Mercier unstable region. As is well known, however, no quantization condition is applicable to the ballooning modes in the three-dimensional system without symmetry, and so the results of the high-mode-number ballooning modes in the covering space had to be confirmed in the real space. Such a confirmation has been done in the Mercier stable region and also in the Mercier unstable region by using three dimensional linearized ideal MHD stability code cas3d. Confirming the relation between high-mode-number ballooning analyses by the global mode analyses, the method of the equilibrium profile variations has been developed in the tree dimensional system, giving dt/dψ - dP/dψ stability diagram corresponding to the s - α diagram in tokamaks. This method of profile variation are very powerful to investigate the second stability of high-mode-number ballooning modes and has been more developed. Recently it has been applied to the plasma in the inward-shifted LHD

Dynamics of tissue shrinkage during ablative temperature exposures

International Nuclear Information System (INIS)

Rossmann, Christian; Haemmerich, Dieter; Garrett-Mayer, Elizabeth; Rattay, Frank

2014-01-01

There is a lack of studies that examine the dynamics of heat-induced shrinkage of organ tissues. Clinical procedures such as radiofrequency ablation, microwave ablation or high-intensity focused ultrasound, use heat to treat diseases such as cancer and cardiac arrhythmia. When heat is applied to tissues, shrinkage occurs due to protein denaturation, dehydration and contraction of collagen at temperatures greater 50 °C. This is particularly relevant for image-guided procedures such as tumor ablation, where pre- and post-treatment images are compared and any changes in dimensions must be considered to avoid misinterpretations of the treatment outcome. We present data from ex vivo, isothermal shrinkage tests in porcine liver tissue, where axial changes in tissue length were recorded during 15 min of heating to temperatures between 60 and 95 °C. A mathematical model was developed to accurately describe the time and temperature-dependent shrinkage behavior. The shrinkage dynamics had the same characteristics independent of temperature; the estimated relative shrinkage, adjusted for time since death, after 15 min heating to temperatures of 60, 65, 75, 85 and 95 °C, was 12.3, 13.8, 16.6, 19.2 and 21.7%, respectively. Our results demonstrate the shrinkage dynamics of organ tissues, and suggest the importance of considering tissue shrinkage for thermal ablative treatments. (paper)

Pathological effects of lung radiofrequency ablation that contribute to pneumothorax, using a porcine model.

Science.gov (United States)

Izaaryene, Jean; Cohen, Frederic; Souteyrand, Philippe; Rolland, Pierre-Henri; Vidal, Vincent; Bartoli, Jean-Michel; Secq, Veronique; Gaubert, Jean-Yves

2017-11-01

The incidence of pneumothorax is 7 times higher after lung radiofrequency ablation (RFA) than after lung biopsy. The reasons for such a difference have never been objectified. The histopathologic changes in lung tissue are well-studied and established for RF in the ablation zone. However, it has not been previously described what the nature of thermal injury might be along the shaft of the RF electrode as it traverses through normal lung tissue to reach the ablation zone. The purpose of this study was to determine the changes occurring around the RF needle along the pathway between the ablated zone and the pleura. In 3 anaesthetised and ventilated swine, 6 RFA procedures (right and left lungs) were performed using a 14-gauge unipolar multi-tined retractable 3 cm radiofrequency LeVeen probe with a coaxial introducer positioned under CT fluoroscopic guidance. In compliance with literature guidelines, we implemented a gradually increasing thermo-ablation protocol using a RF generator. Helical CT images were acquired pre- and post-RFA procedure to detect and evaluate pneumothorax. Four percutaneous 19-gauge lung biopsies were also performed on the fourth swine under CT guidance. Swine were sacrificed for lung ex vivo examinations, scanning electron microscopy (SEM) and pathological analysis. Three severe (over 50 ml) pneumothorax were detected after RFA. In each one of them, pathological examination revealed a fistulous tract between ablation zone and pleura. No fistulous tract was observed after biopsies. In the 3 cases of severe pneumothorax, the tract was wide open and clearly visible on post procedure CT images and SEM examinations. The RFA tract differed from the needle biopsy tract. The histological changes that are usually found in the ablated zone were observed in the RFA tract's wall and were related to thermal lesions. These modifications caused the creation of a coagulated pulmonary parenchyma rim between the thermo-ablation zone and the pleural space

Analysis of Flight of Near-Space Balloon

Science.gov (United States)

Miller, Zech; Evans, Austin; Seyfert, James; Leadlove, Kyle; Gumina, Kaitlyn; Martell, Eric

2015-04-01

In December 2014, the Electronics class at Millikin University launched a balloon designed to travel into the near-space region of the atmosphere. The balloon was equipped with an instrumentation package including a camera, accelerometer, barometric pressure sensor, temperature probes, as well as a system for tracking using an Automatic Packet Reporting System (APRS). The balloon was launched from Decatur, IL, and landed in Marysville, OH, nearly 320 miles away. The students then analyzed the data from the flight and compared results to expectations.

Heat Transfer Model for Hot Air Balloons

OpenAIRE

Lladó Gambín, Adriana

2016-01-01

A heat transfer model and analysis for hot air balloons is presented in this work, backed with a flow simulation using SolidWorks. The objective is to understand the major heat losses in the balloon and to identify the parameters that affect most its flight performance. Results show that more than 70% of the heat losses are due to the emitted radiation from the balloon envelope and that convection losses represent around 20% of the total. A simulated heating source is also included in the mod...

Accurate Determination of the Volume of an Irregular Helium Balloon

Science.gov (United States)

Blumenthal, Jack; Bradvica, Rafaela; Karl, Katherine

2013-01-01

In a recent paper, Zable described an experiment with a near-spherical balloon filled with impure helium. Measuring the temperature and the pressure inside and outside the balloon, the lift of the balloon, and the mass of the balloon materials, he described how to use the ideal gas laws and Archimedes' principal to compute the average molecular…

Percutaneous Irreversible Electroporation Lung Ablation: Preliminary Results in a Porcine Model

International Nuclear Information System (INIS)

Deodhar, Ajita; Monette, Sébastien; Single, Gordon W.; Hamilton, William C.; Thornton, Raymond H.; Sofocleous, Constantinos T.; Maybody, Majid; Solomon, Stephen B.

2011-01-01

Objective: Irreversible electroporation (IRE) uses direct electrical pulses to create permanent “pores” in cell membranes to cause cell death. In contrast to conventional modalities, IRE has a nonthermal mechanism of action. Our objective was to study the histopathological and imaging features of IRE in normal swine lung. Materials and Methods: Eleven female swine were studied for hyperacute (8 h), acute (24 h), subacute (96 h), and chronic (3 week) effects of IRE ablation in lung. Paired unipolar IRE applicators were placed under computed tomography (CT) guidance. Some applicators were deliberately positioned near bronchovascular structures. IRE pulse delivery was synchronized with the cardiac rhythm only when ablation was performed within 2 cm of the heart. Contrast-enhanced CT scan was performed immediately before and after IRE and at 1 and 3 weeks after IRE ablation. Representative tissue was stained with hematoxylin and eosin for histopathology. Results: Twenty-five ablations were created: ten hyperacute, four acute, and three subacute ablations showed alveolar edema and necrosis with necrosis of bronchial, bronchiolar, and vascular epithelium. Bronchovascular architecture was maintained. Chronic ablations showed bronchiolitis obliterans and alveolar interstitial fibrosis. Immediate post-procedure CT images showed linear or patchy density along the applicator tract. At 1 week, there was consolidation that resolved partially or completely by 3 weeks. Pneumothorax requiring chest tube developed in two animals; no significant cardiac arrhythmias were noted. Conclusion: Our preliminary porcine study demonstrates the nonthermal and extracellular matrix sparing mechanism of action of IRE. IRE is a potential alternative to thermal ablative modalities.

MR thermometry for monitoring tumor ablation

International Nuclear Information System (INIS)

Senneville, Baudouin D. de; Quesson, Bruno; Dragonu, Iulius; Moonen, Chrit T.W.; Mougenot, Charles; Grenier, Nicolas

2007-01-01

Local thermal therapies are increasingly used in the clinic for tissue ablation. During energy deposition, the actual tissue temperature is difficult to estimate since physiological processes may modify local heat conduction and energy absorption. Blood flow may increase during temperature increase and thus change heat conduction. In order to improve the therapeutic efficiency and the safety of the intervention, mapping of temperature and thermal dose appear to offer the best strategy to optimize such interventions and to provide therapy endpoints. MRI can be used to monitor local temperature changes during thermal therapies. On-line availability of dynamic temperature mapping allows prediction of tissue death during the intervention based on semi-empirical thermal dose calculations. Much progress has been made recently in MR thermometry research, and some applications are appearing in the clinic. In this paper, the principles of MRI temperature mapping are described with special emphasis on methods employing the temperature dependency of the water proton resonance frequency. Then, the prospects and requirements for widespread applications of MR thermometry in the clinic are evaluated. (orig.)

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

International Nuclear Information System (INIS)

Ortiz, Rocio; Quintana, Iban; Etxarri, Jon; Lejardi, Ainhoa; Sarasua, Jose-Ramon

2011-01-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

Energy Technology Data Exchange (ETDEWEB)

Ortiz, Rocio; Quintana, Iban; Etxarri, Jon [Manufacturing Processes Department, Fundacion TEKNIKER, Av. Otaola 20, 20600, Eibar, Guipuzcoa (Spain); Lejardi, Ainhoa; Sarasua, Jose-Ramon [Department of Mining and Metallurgy Engineering and Materials Science, School of Engineering, University of the Basque Country (EHU-UPV), Alameda de Urquijo s/n, 48013 Bilbao (Spain)

2011-11-01

The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

Meshed-Pumpkin Super-Pressure Balloon Design

Science.gov (United States)

Jones, Jack; Yavrouian, Andre

2003-01-01

An improved, lightweight design has been proposed for super-pressure balloons used to carry scientific instruments at high altitudes in the atmosphere of Earth for times as long as 100 days. [A super-pressure balloon is one in which the pressure of the buoyant gas (typically, helium) is kept somewhat above ambient pressure in order to maintain approximately constant density and thereby regulate the altitude.] The proposed design, called "meshed pumpkin," incorporates the basic concept of the pumpkin design, which is so named because of its appearance. The pumpkin design entails less weight than does a spherical design, and the meshed-pumpkin design would reduce weight further. The basic idea of the meshed-pumpkin design is to reinforce the membrane of a pumpkin balloon by attaching a strong, lightweight fabric mesh to its outer surface. The reinforcement would make it possible to reduce the membrane mass to one-third or less of that of the basic pumpkin design while retaining sufficient strength to enable the balloon to remain at approximately constant altitude for months.

Introduction (Special Issue on Scientific Balloon Capabilities and Instrumentation)

Science.gov (United States)

Gaskin, Jessica A.; Smith, I. S.; Jones, W. V.

2014-01-01

In 1783, the Montgolfier brothers ushered in a new era of transportation and exploration when they used hot air to drive an un-tethered balloon to an altitude of 2 km. Made of sackcloth and held together with cords, this balloon challenged the way we thought about human travel, and it has since evolved into a robust platform for performing novel science and testing new technologies. Today, high-altitude balloons regularly reach altitudes of 40 km, and they can support payloads that weigh more than 3,000 kg. Long-duration balloons can currently support mission durations lasting 55 days, and developing balloon technologies (i.e. Super-Pressure Balloons) are expected to extend that duration to 100 days or longer; competing with satellite payloads. This relatively inexpensive platform supports a broad range of science payloads, spanning multiple disciplines (astrophysics, heliophysics, planetary and earth science.) Applications extending beyond traditional science include testing new technologies for eventual space-based application and stratospheric airships for planetary applications.

Unscheduled DNA synthesis in human skin after in vitro ultraviolet-excimer laser ablation

International Nuclear Information System (INIS)

Green, H.A.; Margolis, R.; Boll, J.; Kochevar, I.E.; Parrish, J.A.; Oseroff, A.R.

1987-01-01

DNA damage repaired by the excision repair system and measured as unscheduled DNA synthesis (UDS) was assessed in freshly excised human skin after 193 and 248 nm ultraviolet (UV)-excimer laser ablative incisions. Laser irradiation at 248 nm induced DNA damage throughout a zone of cells surrounding the ablated and heat-damaged area. In contrast, with 193 nm irradiation UDS was not detected in cells adjacent to the ablated area, even though DNA strongly absorbs this wavelength. Our results suggest that the lack of UDS after 193 nm irradiation is due to: ''shielding'' of DNA by the cellular interstitium, membrane, and cytoplasm, DNA damage that is not repaired by excision repair, or thermal effects that either temporarily or permanently inhibit the excision repair processes

Non-Fourier heat conduction and phase transition in laser ablation of polytetrafluoroethylene (PTFE)

Science.gov (United States)

Zhang, Yu; Zhang, Daixian; Wu, Jianjun; Li, Jian; He, Zhaofu

2017-11-01

The phase transition in heat conduction of polytetrafluoroethylene-like polymers was investigated and applied in many fields of science and engineering. Considering more details including internal absorption of laser radiation, reflectivity of material and non-Fourier effect etc., the combined heat conduction and phase transition in laser ablation of polytetrafluoroethylene were modeled and investigated numerically. The thermal and mechanic issues in laser ablation were illustrated and analyzed. Especially, the phenomenon of temperature discontinuity formed in the combined phase transition and non-Fourier heat conduction was discussed. Comparisons of target temperature profiles between Fourier and non-Fourier heat conduction in melting process were implemented. It was indicated that the effect of non-Fourier plays an important role in the temperature evolvement. The effect of laser fluence was proven to be significant and the thermal wave propagation was independent on the laser intensity for the non-Fourier heat conduction. Besides, the effect of absorption coefficients on temperature evolvements was studied. For different ranges of absorption coefficients, different temperature evolvements can be achieved. The above numerical simulation provided insight into physical processes of combined non-Fourier heat conduction and phase transition in laser ablation.

Looners: Inside the world of balloon fetishism

OpenAIRE

McIntyre, Karen E

2011-01-01

In the spring of 1997, Shaun had just broken up with a boyfriend, and his roommate had moved out. Living alone for the first time and relieved of the fear that someone might walk in the door, he was finally able to indulge his fantasy. The young man sat on his couch and started blowing up balloons. Shaun had loved playing with balloons since he was a child. When he hit puberty, he felt his first orgasm rubbing against a balloon. It was then that his relationship with the object took ...

Taking the Hot Air Out of Balloons.

Science.gov (United States)

Brinks, Virgil L.; Brinks, Robyn L.

1994-01-01

Describes how a teacher can give their students the challenge of designing and building model balloons or blimps. The project helps students learn the basics of balloon flight and what it really means to be "lighter than air." (PR)

Determination of ablation threshold for composite resins and amalgam irradiated with femtosecond laser pulses

International Nuclear Information System (INIS)

Freitas, A Z; Samad, R E; Zezell, D M; Vieira Jr, N D; Freschi, L R; Gouw-Soares, S C

2010-01-01

The use of laser for caries removal and cavity preparation is already a reality in the dental clinic. The objective of the present study was to consider the viability of ultrashort laser pulses for restorative material selective removal, by determining the ablation threshold fluence for composite resins and amalgam irradiated with femtosecond laser pulses. Lasers pulses centered at 830 nm with 50 fs of duration and 1 kHz of repetition rate, with energies in the range of 300 to 770 μJ were used to irradiate the samples. The samples were irradiated using two different geometrical methods for ablation threshold fluence determinations and the volume ablation was measured by optical coherence tomography. The shape of the ablated surfaces were analyzed by optical microscopy and scanning electron microscopy. The determined ablation threshold fluence is 0.35 J/cm 2 for the composite resins Z-100 and Z-350, and 0.25 J/cm 2 for the amalgam. These values are half of the value for enamel in this temporal regime. Thermal damages were not observed in the samples. Using the OCT technique (optical coherence tomography) was possible to determine the ablated volume and the total mass removed

Paraplegia following intraaortic balloon circulatory assistance

Directory of Open Access Journals (Sweden)

Benício Anderson

1999-01-01

Full Text Available Intraaortic balloon counterpulsation is frequently used in patients experiencing severe ventricular dysfunction following maximal drug therapy. However, even with the improvement of percutaneous insertion techniques, the procedure has always been followed by vascular, infectious, and neurological complications. This article describes a case of paraplegia due to intraaortic balloon counterpulsation in the postoperative period of cardiac surgery.

Radiofrequency Ablation of Lung Tumors

Science.gov (United States)

... News Physician Resources Professions Site Index A-Z Radiofrequency Ablation (RFA) / Microwave Ablation (MWA) of Lung Tumors ... and Microwave Ablation of Lung Tumors? What are Radiofrequency and Microwave Ablation of Lung Tumors? Radiofrequency ablation, ...

Deflation of gastric band balloon in pregnancy for improving outcomes.

Science.gov (United States)

Jefferys, Amanda E; Siassakos, Dimitrios; Draycott, Tim; Akande, Valentine A; Fox, Robert

2013-04-30

In line with the rise in the prevalence of obesity, an increasing number of women of childbearing age are undergoing laparoscopic adjustable gastric banding (LAGB), resulting in an increasing number of pregnancies with a band in place. Currently, there is no consensus on optimal band management in pregnancy. Some clinicians advocate leaving the band balloon inflated to reduce gestational weight gain and associated adverse perinatal outcomes. However, there are concerns that maintaining balloon inflation during pregnancy might increase the risk of band complications and adversely affect fetal development and/or growth as a result of reduced nutritional intake. To compare maternal and perinatal outcomes for elective gastric band balloon deflation versus intention to maintain balloon inflation during pregnancy. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2012) and the Web of Science database (1940 to September 2012). Randomised-controlled trials comparing elective deflation of the gastric band balloon with intention to maintain balloon inflation in pregnant women who have undergone LAGB. Two review authors independently assessed studies for inclusion. No studies met the criteria for inclusion in the review. To date no randomised controlled trials exist that compare elective deflation of the gastric band balloon in pregnancy versus intention to maintain balloon inflation. Further research is needed to define the optimum management of the gastric band balloon in pregnancy.

Non-coaxial-based microwave ablation antennas for creating symmetric and asymmetric coagulation zones

Science.gov (United States)

Mohtashami, Yahya; Luyen, Hung; Hagness, Susan C.; Behdad, Nader

2018-06-01

We present an investigation of a new class of microwave ablation (MWA) antennas capable of producing axially symmetric or asymmetric heating patterns. The antenna design is based on a dipole fed by a balanced parallel-wire transmission line. The angle and direction of the deployed dipole arms are used to control the heating pattern. We analyzed the specific absorption rate and temperature profiles using electromagnetic and thermal simulations. Two prototypes were fabricated and tested in ex vivo ablation experiments: one was designed to produce symmetric heating patterns and the other was designed to generate asymmetric heating patterns. Both fabricated prototypes exhibited good impedance matching and produced localized coagulation zones as predicted by the simulations. The prototype operating in porcine muscle created an ˜10 cm3 symmetric ablation zone after 10 min of ablation with a power level of 18 W. The prototype operating in egg white created an ˜4 cm3 asymmetric ablation zone with a directionality ratio of 40% after 5 min of ablation with a power level of 25 W. The proposed MWA antenna design shows promise for minimally invasive treatment of tumors in various clinical scenarios where, depending on the situation, a symmetric or an asymmetric heating pattern may be needed.

Reduction of prostate intrafraction motion using gas-release rectal balloons

International Nuclear Information System (INIS)

Su Zhong; Zhao Tianyu; Li Zuofeng; Hoppe, Brad; Henderson, Randy; Mendenhall, William; Nichols, R. Charles; Marcus, Robert; Mendenhall, Nancy

2012-01-01

Purpose: To analyze prostate intrafraction motion using both non-gas-release (NGR) and gas-release (GR) rectal balloons and to evaluate the ability of GR rectal balloons to reduce prostate intrafraction motion. Methods: Twenty-nine patients with NGR rectal balloons and 29 patients with GR balloons were randomly selected from prostate patients treated with proton therapy at University of Florida Proton Therapy Institute (Jacksonville, FL). Their pretreatment and post-treatment orthogonal radiographs were analyzed, and both pretreatment setup residual error and intrafraction-motion data were obtained. Population histograms of intrafraction motion were plotted for both types of balloons. Population planning target-volume (PTV) margins were calculated with the van Herk formula of 2.5Σ+ 0.7σ to account for setup residual errors and intrafraction motion errors. Results: Pretreatment and post-treatment radiographs indicated that the use of gas-release rectal balloons reduced prostate intrafraction motion along superior–inferior (SI) and anterior–posterior (AP) directions. Similar patient setup residual errors were exhibited for both types of balloons. Gas-release rectal balloons resulted in PTV margin reductions from 3.9 to 2.8 mm in the SI direction, 3.1 to 1.8 mm in the AP direction, and an increase from 1.9 to 2.1 mm in the left–right direction. Conclusions: Prostate intrafraction motion is an important uncertainty source in radiotherapy after image-guided patient setup with online corrections. Compared to non-gas-release rectal balloons, gas-release balloons can reduce prostate intrafraction motion in the SI and AP directions caused by gas buildup.

Reduction of prostate intrafraction motion using gas-release rectal balloons

Energy Technology Data Exchange (ETDEWEB)

Su Zhong; Zhao Tianyu; Li Zuofeng; Hoppe, Brad; Henderson, Randy; Mendenhall, William; Nichols, R. Charles; Marcus, Robert; Mendenhall, Nancy [Department of Radiation Oncology, University of Florida Proton Therapy Institute, Jacksonville, Florida 32206 (United States)

2012-10-15

Purpose: To analyze prostate intrafraction motion using both non-gas-release (NGR) and gas-release (GR) rectal balloons and to evaluate the ability of GR rectal balloons to reduce prostate intrafraction motion. Methods: Twenty-nine patients with NGR rectal balloons and 29 patients with GR balloons were randomly selected from prostate patients treated with proton therapy at University of Florida Proton Therapy Institute (Jacksonville, FL). Their pretreatment and post-treatment orthogonal radiographs were analyzed, and both pretreatment setup residual error and intrafraction-motion data were obtained. Population histograms of intrafraction motion were plotted for both types of balloons. Population planning target-volume (PTV) margins were calculated with the van Herk formula of 2.5{Sigma}+ 0.7{sigma} to account for setup residual errors and intrafraction motion errors. Results: Pretreatment and post-treatment radiographs indicated that the use of gas-release rectal balloons reduced prostate intrafraction motion along superior-inferior (SI) and anterior-posterior (AP) directions. Similar patient setup residual errors were exhibited for both types of balloons. Gas-release rectal balloons resulted in PTV margin reductions from 3.9 to 2.8 mm in the SI direction, 3.1 to 1.8 mm in the AP direction, and an increase from 1.9 to 2.1 mm in the left-right direction. Conclusions: Prostate intrafraction motion is an important uncertainty source in radiotherapy after image-guided patient setup with online corrections. Compared to non-gas-release rectal balloons, gas-release balloons can reduce prostate intrafraction motion in the SI and AP directions caused by gas buildup.

Feasibility of saline infusion on the liver surface during radiofrequency ablation of subcapsuIar hepatic tumor: an experimentaI study

International Nuclear Information System (INIS)

Lee, Young Rang; Kim, Young Sun; Rhim, Hyun Chul; Seo, Heung Suk; Cho, On Koo; Koh, Byung Hee; Kim, Yong Soo; Kim, Sung Kyu; Paik, Seung Sam

2004-01-01

The purpose of the study was to evaluate the feasibility of infusion of normal saline onto the surface of the liver capsule for minimizing thermal injury of the adjacent organs during radiofrequency ablation of subcapsular hepatic tumor in an ex-vivo porcine model. We used porcine small bowel with it's serosal surface spread onto the porcine liver as an experiment model. The puncturing electrode was inserted into a 6 Fr introducer sheath, and the introducer sheath was connected to the infusion pump for creating a saline flow over the liver surface. A total of 15 ablations were divided into the control group (n=5), intermittent saline infusion group (n=5) and continuous saline infusion (n=5) group. The ablations were done during 3 minutes, and the infusion was set at 2 ml/min and stopped every 30 seconds in the intermittent saline infusion group. After the ablation, we measured the size of the ablated lesion on the surface of bowel and liver, and we also measured the depth of hepatic lesion. Ablated areas of bowel and liver surface in the control group, intermittent saline infusion group and continuous infusion group were 210.7±89.1 mm 2 , 74.6±27.2 mm 2 and 35.8±43.4 mm 2 , respectively, and 312.6±73.6 mm 2 , 228.4±110.5 mm 2 , and 80.9±55.1 mm 2 , respectively. In contrast to the broad base of the ablated area on the surface of the liver in the control group, the shapes of the lesions became narrower approaching to the liver surface in all cases of the continuous saline infusion group, and the shapes of the lesions were broad based in 3 cases and narrow based in 2 cases of the intermittent saline infusion group. Continuous infusion of normaI saline onto the surface of the liver during radiofrequency ablation of subcapsular hepatic tumor is a feasible method for minimizing thermal injury of the adjacent organs. Further exploration of the optimal parameters or techniques to maximize the hepatic ablation and simultaneously to minimize the thermal injury of

An inverse method for non linear ablative thermics with experimentation of automatic differentiation

Energy Technology Data Exchange (ETDEWEB)

Alestra, S [Simulation Information Technology and Systems Engineering, EADS IW Toulouse (France); Collinet, J [Re-entry Systems and Technologies, EADS ASTRIUM ST, Les Mureaux (France); Dubois, F [Professor of Applied Mathematics, Conservatoire National des Arts et Metiers Paris (France)], E-mail: stephane.alestra@eads.net, E-mail: jean.collinet@astrium.eads.net, E-mail: fdubois@cnam.fr

2008-11-01

Thermal Protection System is a key element for atmospheric re-entry missions of aerospace vehicles. The high level of heat fluxes encountered in such missions has a direct effect on mass balance of the heat shield. Consequently, the identification of heat fluxes is of great industrial interest but is in flight only available by indirect methods based on temperature measurements. This paper is concerned with inverse analyses of highly evolutive heat fluxes. An inverse problem is used to estimate transient surface heat fluxes (convection coefficient), for degradable thermal material (ablation and pyrolysis), by using time domain temperature measurements on thermal protection. The inverse problem is formulated as a minimization problem involving an objective functional, through an optimization loop. An optimal control formulation (Lagrangian, adjoint and gradient steepest descent method combined with quasi-Newton method computations) is then developed and applied, using Monopyro, a transient one-dimensional thermal model with one moving boundary (ablative surface) that has been developed since many years by ASTRIUM-ST. To compute numerically the adjoint and gradient quantities, for the inverse problem in heat convection coefficient, we have used both an analytical manual differentiation and an Automatic Differentiation (AD) engine tool, Tapenade, developed at INRIA Sophia-Antipolis by the TROPICS team. Several validation test cases, using synthetic temperature measurements are carried out, by applying the results of the inverse method with minimization algorithm. Accurate results of identification on high fluxes test cases, and good agreement for temperatures restitutions, are obtained, without and with ablation and pyrolysis, using bad fluxes initial guesses. First encouraging results with an automatic differentiation procedure are also presented in this paper.

Influence of water content on the ablation of skin with a 532 nm nanosecond Nd:YAG laser

Science.gov (United States)

Kim, Soogeun; Eom, Tae Joong; Jeong, Sungho

2015-01-01

This work reports that the ablation volume and rate of porcine skin changed significantly with the change of skin water content. Under the same laser irradiation conditions (532 nm Nd:YAG laser, pulse width=11.5 ns, pulse energy=1.54 J, beam radius=0.54 mm), the ablation volume dropped by a factor of 4 as the skin water content decreased from 40 wt. % (native) to 19 wt. % with a change in the ablation rate below and above around 25 wt. %. Based on the ablation characteristics observed by in situ shadowgraph images and the calculated tissue temperatures, it is considered that an explosive rupture by rapid volumetric vaporization of water is responsible for the ablation of the high water content of skin, whereas thermal disintegration of directly irradiated surface layer is responsible for the low water content of skin.

Thermal Protection System Mass Estimating Relationships For Blunt-Body, Earth Entry Spacecraft

Science.gov (United States)

Sepka, Steven A.; Samareh, Jamshid A.

2015-01-01

Mass estimating relationships (MERs) are developed to predict the amount of thermal protection system (TPS) necessary for safe Earth entry for blunt-body spacecraft using simple correlations that are non-ITAR and closely match estimates from NASA's highfidelity ablation modeling tool, the Fully Implicit Ablation and Thermal Analysis Program (FIAT). These MERs provide a first order estimate for rapid feasibility studies. There are 840 different trajectories considered in this study, and each TPS MER has a peak heating limit. MERs for the vehicle forebody include the ablators Phenolic Impregnated Carbon Ablator (PICA) and Carbon Phenolic atop Advanced Carbon-Carbon. For the aftbody, the materials are Silicone Impregnated Reusable Ceramic Ablator (SIRCA), Acusil II, SLA- 561V, and LI-900. The MERs are accurate to within 14% (at one standard deviation) of FIAT prediction, and the most any MER can under predict FIAT TPS thickness is 18.7%. This work focuses on the development of these MERs, the resulting equations, model limitations, and model accuracy.

Temperature changes in the pulp chamber during dentin ablation with Er:YAG laser

Science.gov (United States)

Zhang, Xianzeng; Zhao, Haibin; Zhan, Zhenlin; Guo, Wenqing; Xie, Shusen

2012-12-01

To examine the temperature changes in the pulp chamber during cavity preparation in dentin with the Er:YAG laser (2940 nm), a total 20 intact premolars teeth were divided into 4 groups for dentin ablation with different radiant exposures at 4Hz and 8Hz with and without water spray. A K-type thermocouple was used to monitor the temperature changes in pulp chamber during laser treatment. The total time of irradiation was 70 sec. the water spray rate was 3 mL/min. It showed that maximum temperature rise increases with the increasing of radiant exposure and pulse repetition rate and the additional water cooling during laser ablation can significantly reduce the temperature rise in pulp chamber which will benefit to avoid or reduce thermal damage to tooth structure and dental pulp. The highest rise of temperature in the pulp was achieved with 20 J/cm2 and 8 Hz (19.83°C ). For all sample without water spray, the rise of temperature was exceed 5 °C . In contrast, with water spray, the temperature rise in the pulp can be firmly controlled under 1°C. The results also indicated that ablation rate and efficiency can be enhanced by increasing the incident radiant exposure and pulse repetition rate, which simultaneously producing more heat accumulation in dental tissue and causing thermal damage to dental tissue. By applying an additional water spray, thermal damage can be significantly reduced in clinical application.

Ballooning modes or Fourier modes in a toroidal plasma?

International Nuclear Information System (INIS)

Connor, J.W.; Taylor, J.B.

1987-01-01

The relationship between two different descriptions of eigenmodes in a torus is investigated. In one the eigenmodes are similar to Fourier modes in a cylinder and are highly localized near a particular rational surface. In the other they are the so-called ballooning modes that extend over many rational surfaces. Using a model that represents both drift waves and resistive interchanges the transition from one of these structures to the other is investigated. In this simplified model the transition depends on a single parameter which embodies the competition between toroidal coupling of Fourier modes (which enhances ballooning) and variation in frequency of Fourier modes from one rational surface to another (which diminishes ballooning). As the coupling is increased each Fourier mode acquires a sideband on an adjacent rational surface and these sidebands then expand across the radius to form the extended mode described by the conventional ballooning mode approximation. This analysis shows that the ballooning approximation is appropriate for drift waves in a tokamak but not for resistive interchanges in a pinch. In the latter the conventional ballooning effect is negligible but they may nevertheless show a ballooning feature. This is localized near the same rational surface as the primary Fourier mode and so does not lead to a radially extended structure