CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma: specific technical aspects and clinical results.

PubMed

Sommer, C M; Lemm, G; Hohenstein, E; Bellemann, N; Stampfl, U; Goezen, A S; Rassweiler, J; Kauczor, H U; Radeleff, B A; Pereira, P L

2013-06-01

This study was designed to evaluate the clinical efficacy of CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma (RCC) and to analyze specific technical aspects between both technologies. We included 22 consecutive patients (3 women; age 74.2 ± 8.6 years) after 28 CT-guided bipolar or multipolar RF ablations of 28 RCCs (diameter 2.5 ± 0.8 cm). Procedures were performed with a commercially available RF system (Celon AG Olympus, Berlin, Germany). Technical aspects of RF ablation procedures (ablation mode [bipolar or multipolar], number of applicators and ablation cycles, overall ablation time and deployed energy, and technical success rate) were analyzed. Clinical results (local recurrence-free survival and local tumor control rate, renal function [glomerular filtration rate (GFR)]) and complication rates were evaluated. Bipolar RF ablation was performed in 12 procedures and multipolar RF ablation in 16 procedures (2 applicators in 14 procedures and 3 applicators in 2 procedures). One ablation cycle was performed in 15 procedures and two ablation cycles in 13 procedures. Overall ablation time and deployed energy were 35.0 ± 13.6 min and 43.7 ± 17.9 kJ. Technical success rate was 100 %. Major and minor complication rates were 4 and 14 %. At an imaging follow-up of 15.2 ± 8.8 months, local recurrence-free survival was 14.4 ± 8.8 months and local tumor control rate was 93 %. GFR did not deteriorate after RF ablation (50.8 ± 16.6 ml/min/1.73 m(2) before RF ablation vs. 47.2 ± 11.9 ml/min/1.73 m(2) after RF ablation; not significant). CT-guided bipolar and multipolar RF ablation of RCC has a high rate of clinical success and low complication rates. At short-term follow-up, clinical efficacy is high without deterioration of the renal function.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gockner, T. L., E-mail: theresa.gockner@med.uni-heidelberg.de; Zelzer, S., E-mail: s.zelzer@dkfz-heidelberg.de; Mokry, T., E-mail: theresa.mokry@med.uni-heidelberg.de

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

Ablative heat shield design for space shuttle

NASA Technical Reports Server (NTRS)

Seiferth, R. W.

1973-01-01

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

On the origin of extraterrestrial stratospheric particles: Interplanetary dust or meteor ablation debris?. M.S. Thesis

NASA Technical Reports Server (NTRS)

Kyte, F. T.

1977-01-01

Meteor ablation debris was distinguished from unablated interplanetary dust in a collection of extraterrestrial particles collected in the stratosphere using NASA U-2 aircraft. A 62 g sample of the Murchison (C2) meteorite was artificially ablated to characterize ablation debris for comparison with the stratospheric particles. By using proper experimental conditions, artificial ablation debris can be produced that is similar to natural ablation debris. Analyses of natural fusion crusts, artificial fusion crust, and artificial ablation debris of the Murchison meteorite produced criteria for recognizing debris ablated by a primitive meteoroid. Ninety-five percent of the stratospheric particles can be described as either ablation debris from a primitive meteoroid, or as very primitive interplanetary dust.

Image-Guided Ablation of Adrenal Lesions

PubMed Central

Yamakado, Koichiro

2014-01-01

Although laparoscopic adrenalectomy has remained the standard of care for the treatment for adrenal tumors, percutaneous image-guided ablation therapy, such as chemical ablation, radiofrequency ablation, cryoablation, and microwave ablation, has been shown to be clinically useful in many nonsurgical candidates. Ablation therapy has been used to treat both functioning adenomas and malignant tumors, including primary adrenal carcinoma and metastasis. For patients with functioning adenomas, biochemical and symptomatic improvement is achieved in 96 to 100% after ablation; for patients with malignant adrenal neoplasms, however, the survival benefit from ablation therapy remains unclear, though good initial results have been reported. This article outlines the current role of ablation therapy for adrenal lesions, as well as identifying some of the technical considerations for this procedure. PMID:25049444

Impact of Tricuspid Regurgitation on the Success of Atrioventricular Node Ablation for Rate Control in Patients With Atrial Fibrillation: The Node Blast Study.

PubMed

Reddy, Yeruva Madhu; Gunda, Sampath; Vallakati, Ajay; Kanmanthareddy, Arun; Pillarisetti, Jayasree; Atkins, Donita; Bommana, Sudharani; Emert, Martin P; Pimentel, Rhea; Dendi, Raghuveer; Berenbom, Loren D; Lakkireddy, Dhanunjaya

2015-09-15

Atrioventricular node (AVN) ablation is an effective treatment for symptomatic patients with atrial arrhythmias who are refractory to rhythm and rate control strategies where optimal ventricular rate control is desired. There are limited data on the predictors of failure of AVN ablation. Our objective was to identify the predictors of failure of AVN ablation. This is an observational single-center study of consecutive patients who underwent AVN ablation in a large academic center. Baseline characteristics, procedural variables, and outcomes of AVN ablation were collected. AVN "ablation failure" was defined as resumption of AVN conduction resulting in recurrence of either rapid ventricular response or suboptimal biventricular pacing. A total of 247 patients drug refractory AF who underwent AVN ablation at our center with a mean age of 71 ± 12 years with 46% being males were included. Ablation failure was seen in 11 (4.5%) patients. There were no statistical differences between patients with "ablation failure" versus "ablation success" in any of the baseline clinical variables. Patients with moderate-to-severe tricuspid regurgitation (TR) were much more likely to have ablation failure than those with ablation success (8 [73%] vs 65 [27%]; p = 0.003). All 11 patients with ablation failure had a successful redo procedure, 9 with right and 2 with the left sided approach. On multivariate analysis, presence of moderate-to-severe TR was found to be the only predictor of failure of AVN ablation (odds ratio 9.1, confidence interval 1.99 to 42.22, p = 0.004). In conclusion, moderate-to-severe TR is a strong and independent predictor of failure of AVN ablation. Copyright © 2015 Elsevier Inc. All rights reserved.

Comparison between different thickness umbrella-shaped expandable radiofrequency electrodes (SuperSlim and CoAccess): Experimental and clinical study

PubMed Central

KODA, MASAHIKO; TOKUNAGA, SHIHO; MATONO, TOMOMITSU; SUGIHARA, TAKAAKI; NAGAHARA, TAKAKAZU; MURAWAKI, YOSHIKAZU

2011-01-01

The purpose of the present study was to compare the size and configuration of the ablation zones created by SuperSlim and CoAccess electrodes, using various ablation algorithms in ex vivo bovine liver and in clinical cases. In the experimental study, we ablated explanted bovine liver using 2 types of electrodes and 4 ablation algorithms (combinations of incremental power supply, stepwise expansion and additional low-power ablation) and evaluated the ablation area and time. In the clinical study, we compared the ablation volume and the shape of the ablation zone between both electrodes in 23 hepatocellular carcinoma (HCC) cases with the best algorithm (incremental power supply, stepwise expansion and additional low-power ablation) as derived from the experimental study. In the experimental study, the ablation area and time by the CoAccess electrode were significantly greater compared to those by the SuperSlim electrode for the single-step (algorithm 1, p=0.0209 and 0.0325, respectively) and stepwise expansion algorithms (algorithm 2, p=0.0002 and <0.0001, respectively; algorithm 3, p= 0.006 and 0.0407, respectively). However, differences were not significant for the additional low-power ablation algorithm. In the clinical study, the ablation volume and time in the CoAccess group were significantly larger and longer, respectively, compared to those in the SuperSlim group (p=0.0242 and 0.009, respectively). Round ablation zones were acquired in 91.7% of the CoAccess group, while irregular ablation zones were obtained in 45.5% of the SuperSlim group (p=0.0428). In conclusion, the CoAccess electrode achieves larger and more uniform ablation zones compared with the SuperSlim electrode, though it requires longer ablation times in experimental and clinical studies. PMID:22977647

Use of bipolar radiofrequency catheter ablation in treatment of cardiac arrhythmias.

PubMed

Soucek, Filip; Starek, Zdenek

2018-05-23

Background Arrhythmia management is a complex process involving both pharmacological and non-pharmacological approaches. Radiofrequency ablation is the pillar of non-pharmacological arrhythmia treatment. Unipolar ablation is considered to be the gold standard in the treatment of the majority of arrhythmias; however, its efficacy is limited to specific cases. In particular, the creation of deep or transmural lesions to eliminate intramurally originating arrhythmias remains inadequate. Bipolar ablation is proposed as an alternative to overcome unipolar ablation boundaries. Results Despite promising results gained from in vitro and animal studies showing that bipolar ablation is superior in creating transmural lesions, the use of bipolar ablation in daily clinical practice is limited. Several studies have been published showing that bipolar ablation is effective in the treatment of clinical arrhythmias after failed unipolar ablation, however there is inconsistency regarding safety of bipolar ablation within the available research papers. According to research evidence the most common indications for bipolar ablation use are ventricular originating rhythmic disorders in patients with structural heart disease resistant to standard radiofrequency ablation. Conclusions To allow wider clinical application the efficiency and safety of bipolar ablation need to be verified in future studies. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Radiofrequency thermo-ablation of PVNS in the knee: initial results.

PubMed

Lalam, Radhesh K; Cribb, Gillian L; Cassar-Pullicino, Victor N; Cool, Wim P; Singh, Jaspreet; Tyrrell, Prudencia N M; Tins, Bernhard J; Winn, Naomi

2015-12-01

Pigmented villonodular synovitis (PVNS) is normally treated by arthroscopic or open surgical excision. We present our initial experience with radiofrequency thermo-ablation (RF ablation) of PVNS located in an inaccessible location in the knee. Review of all patients with histologically proven PVNS treated with RF ablation and with at least 2-year follow-up. Three patients met inclusion criteria and were treated with RF ablation. Two of the patients were treated successfully by one ablation procedure. One of the three patients had a recurrence which was also treated successfully by repeat RF ablation. There were no complications and all patients returned to their previous occupations following RF ablation. In this study we demonstrated the feasibility of performing RF ablation to treat PVNS in relatively inaccessible locations with curative intent. We have also discussed various post-ablation imaging appearances which can confound the assessment for residual/recurrent disease.

Automated microwave ablation therapy planning with single and multiple entry points

NASA Astrophysics Data System (ADS)

Liu, Sheena X.; Dalal, Sandeep; Kruecker, Jochen

2012-02-01

Microwave ablation (MWA) has become a recommended treatment modality for interventional cancer treatment. Compared with radiofrequency ablation (RFA), MWA provides more rapid and larger-volume tissue heating. It allows simultaneous ablation from different entry points and allows users to change the ablation size by controlling the power/time parameters. Ablation planning systems have been proposed in the past, mainly addressing the needs for RFA procedures. Thus a planning system addressing MWA-specific parameters and workflows is highly desirable to help physicians achieve better microwave ablation results. In this paper, we design and implement an automated MWA planning system that provides precise probe locations for complete coverage of tumor and margin. We model the thermal ablation lesion as an ellipsoidal object with three known radii varying with the duration of the ablation and the power supplied to the probe. The search for the best ablation coverage can be seen as an iterative optimization problem. The ablation centers are steered toward the location which minimizes both un-ablated tumor tissue and the collateral damage caused to the healthy tissue. We assess the performance of our algorithm using simulated lesions with known "ground truth" optimal coverage. The Mean Localization Error (MLE) between the computed ablation center in 3D and the ground truth ablation center achieves 1.75mm (Standard deviation of the mean (STD): 0.69mm). The Mean Radial Error (MRE) which is estimated by comparing the computed ablation radii with the ground truth radii reaches 0.64mm (STD: 0.43mm). These preliminary results demonstrate the accuracy and robustness of the described planning algorithm.

A cost-utility analysis of ablative therapy for Barrett’s esophagus

PubMed Central

Inadomi, John M.; Somsouk, Ma; Madanick, Ryan D.; Thomas, Jennifer P.; Shaheen, Nicholas J.

2009-01-01

Background & Aims Recommendations for patients with Barrett’s esophagus (BE) include endoscopic surveillance with esophagectomy for early-stage cancer, although new technologies to ablate dysplasia and metaplasia are available. This study compares the cost-utility of ablation with that of endoscopic surveillance strategies. Methods A decision analysis model was created to examine a population of patients with BE (mean age 50), with separate analyses for patients with no dysplasia, low-grade dysplasia (LGD), or high-grade dysplasia (HGD). Strategies compared were: no endoscopic surveillance; endoscopic surveillance with ablation for incident dysplasia; immediate ablation followed by endoscopic surveillance in all patients or limited to patients in whom metaplasia persisted, and esophagectomy. Ablation modalities modeled included radiofrequency, argon plasma coagulation, multipolar electrocoagulation and photodynamic therapy. Results Endoscopic ablation for patients with HGD could increase life expectancy by 3 quality-adjusted years at an incremental cost of < $6,000, compared with no intervention. Patients with LGD or no dysplasia can also be optimally managed with ablation, but continued surveillance after eradication of metaplasia is expensive. If ablation permanently eradicates at least 28% of LGD or 40% of non-dysplastic metaplasias, ablation would be preferred to surveillance. Conclusions Endoscopic ablation could be the preferred strategy for managing patients with BE with HGD. Ablation might also be preferred in subjects with LGD or no dysplasia, but the cost-effectiveness depends on the long-term effectiveness of ablation and whether surveillance endoscopy can be discontinued following successful ablation. As further post-ablation data become available, the optimal management strategy will be clarified. PMID:19272389

Femtosecond laser for cavity preparation in enamel and dentin: ablation efficiency related factors.

PubMed

Chen, H; Li, H; Sun, Yc; Wang, Y; Lü, Pj

2016-02-11

To study the effects of laser fluence (laser energy density), scanning line spacing and ablation depth on the efficiency of a femtosecond laser for three-dimensional ablation of enamel and dentin. A diode-pumped, thin-disk femtosecond laser (wavelength 1025 nm, pulse width 400 fs) was used for the ablation of enamel and dentin. The laser spot was guided in a series of overlapping parallel lines on enamel and dentin surfaces to form a three-dimensional cavity. The depth and volume of the ablated cavity was then measured under a 3D measurement microscope to determine the ablation efficiency. Different values of fluence, scanning line spacing and ablation depth were used to assess the effects of each variable on ablation efficiency. Ablation efficiencies for enamel and dentin were maximized at different laser fluences and number of scanning lines and decreased with increases in laser fluence or with increases in scanning line spacing beyond spot diameter or with increases in ablation depth. Laser fluence, scanning line spacing and ablation depth all significantly affected femtosecond laser ablation efficiency. Use of a reasonable control for each of these parameters will improve future clinical application.

Ablation properties of carbon/carbon composites with tungsten carbide

NASA Astrophysics Data System (ADS)

Yin, Jian; Zhang, Hongbo; Xiong, Xiang; Huang, Baiyun; Zuo, Jinlv

2009-02-01

The ablation properties and morphologies of carbon/carbon (C/C) composites with tungsten carbide (WC) filaments were investigated by ablation test on an arc heater and scanning electron microscopy. And the results were compared with those without tungsten carbide (WC) filaments tested under the same conditions. It shows that there is a big difference between C/C composites with and without WC filaments on both macroscopic and microscopic ablation morphologies and the ablation rates of the former are higher than the latter. It is found that the ablation process of C/C composites with WC filaments includes oxidation of carbon fibers, carbon matrices and WC, melting of WC and WO 3, and denudation of WC, WO 3 and C/C composites. Oxidation and melting of WC leads to the formation of holes in z directional carbon fiber bundles, which increases the coarseness of the ablation surfaces of the composites, speeds up ablation and leads to the higher ablation rate. Moreover, it is further found that the molten WC and WO 3 cannot form a continuous film on the ablation surface to prevent further ablation of C/C composites.

Study on ablation behavior of silicone rubber based insulation material under the condition of boron oxide particles erosion

NASA Astrophysics Data System (ADS)

Zha, B. L.; Shi, Y. A.; Wang, J. J.; Su, Q. D.

2018-01-01

Self-designed oxygen-kerosene ablation system was employed to study the ablation characteristics of silicone rubber based thermal insulation materials under the condition of boron oxide particles erosion. The ablation test was designed with a mass fraction of 1.69% boron oxide particles and particles-free, the microstructure and elemental analysis of the specimens before and after ablation were carried out by Scanning Electron Microscopy (SEM) and Energy Dispersion Spectrum (EDS). Experiment results show that the average mass ablation rate of the materials was 0.0099 g•s-1 and the average ablation rate was -0.025 mm•s-1 under the condition of pure gas phase ablation; and the average mass ablation rate of the multiphase ablation test group was 0.1775 g•s-1, whose average ablation rate was 0.437 mm•s-1 during the ablation process, the boron oxide particles would adhere a molten layer on the flame contact surface of the specimen, which covering the pores on the material surface, blocking the infiltration channel for the oxidizing component and slowing down the oxidation loss rate of the material below the surface, but because the particles erosion was the main reason for material depletion, the combined effect of the above both led to the upward material ablation rates of Silicone Rubber.

Bimodal electric tissue ablation (BETA) - in-vivo evaluation of the effect of applying direct current before and during radiofrequency ablation of porcine liver.

PubMed

Cockburn, J F; Maddern, G J; Wemyss-Holden, S A

2007-03-01

To examine the effect of applying increasing amounts of direct current (DC) before and during alternating current radiofrequency ablation of porcine liver. Using a Radiotherapeutics RF3000 generator, a 9 V AC/DC transformer and a 16 G plain aluminium tube as an electrode, a control group of 24 porcine hepatic radiofrequency ablation zones was compared with 24 zones created using a bimodal electric tissue ablation (BETA) technique in three pigs. All ablations were terminated when tissue impedance rose to greater than 999 Omega or radiofrequency energy input fell below 5 W on three successive measurements taken at 1 min intervals. BETA ablations were performed in two phases: an initial phase of variable duration DC followed by a second phase during which standard radiofrequency ablation was applied simultaneously with DC. During this second phase, radiofrequency power input was regulated by the feedback circuitry of the RF3000 generator according to changes in tissue impedance. The diameters (mm) of each ablation zone were measured by two observers in two planes perpendicular to the plane of needle insertion. The mean short axis diameter of each ablation zone was subjected to statistical analysis. With increased duration of prior application of DC, there was a progressive increase in the diameter of the ablation zone (p<0.001). This effect increased sharply up to 300 s of pre-treatment after which a further increase in diameter occurred, but at a much lesser rate. A maximum ablation zone diameter of 32 mm was produced (control diameters 10-13 mm). Applying a 9 V DC to porcine liver in vivo, and continuing this DC application during subsequent radiofrequency ablation, results in larger ablation zone diameters compared with radiofrequency ablation alone.

Sequential high intensity focused ultrasound (HIFU) ablation in the treatment of benign multinodular goitre: an observational retrospective study.

PubMed

Lang, Brian H H; Woo, Yu-Cho; Chiu, Keith Wan-Hang

2018-03-19

Assessing the efficacy and safety of sequential high-intensity focused ultrasound (HIFU) ablation in a multinodular goitre (MNG) by comparing them with single HIFU ablation. One hundred and four (84.6%) patients underwent single ablation of a single nodule (group I), while 19 (15.4%) underwent sequential ablation of two relatively-dominant nodules in a MNG (group II). Extent of shrinkage per nodule [by volume reduction ratio (VRR)], pain scores (by 0-10 visual analogue scale) during and after ablation, and rate of vocal cord palsy (VCP), skin burn and nausea/vomiting were compared between the two groups. All 19 (100%) sequential ablations completed successfully. The 3- and 6-month VRR of each nodule were comparable between the two groups (p > 0.05) and in group II, the 3- and 6-month VRR between the first and second nodules were comparable (p = 0.710 and p = 0.548, respectively). Pain score was significantly higher in group II in the morning after ablation (2.29 vs 1.15, p = 0.047) and nausea/vomiting occurred significantly more frequently in group II (15.8% vs 0.0%, p = 0.012). However, VCP and skin burn were comparable (p > 0.05). Sequential ablation had comparable efficacy and safety as single ablation. However, patients undergoing sequential ablation are at higher likelihood of pain in the following morning and nausea/vomiting after ablation. • Sequential HIFU ablation is well-tolerated in patients with two dominant thyroid nodules • More pain is experienced in the morning following sequential HIFU ablation • More nausea/vomiting is experienced following sequential HIFU ablation.

Histopathology of breast cancer after magnetic resonance-guided high-intensity focused ultrasound and radiofrequency ablation.

PubMed

Knuttel, Floortje M; Waaijer, Laurien; Merckel, Laura G; van den Bosch, Maurice A A J; Witkamp, Arjen J; Deckers, Roel; van Diest, Paul J

2016-08-01

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation and radiofrequency ablation (RFA) are being researched as possible substitutes for surgery in breast cancer patients. The histopathological appearance of ablated tissue has not been studied in great detail. This study aimed to compare histopathological features of breast cancer after MR-HIFU ablation and RFA. MR-HIFU ablation and RFA were performed in- and ex-vivo. Tumours in six mastectomy specimens were partially ablated with RFA or MR-HIFU. In-vivo MR-HIFU ablation was performed 3-6 days before excision; RFA was performed in the operation room. Tissue was fixed in formalin and processed to haematoxylin and eosin (H&E) and cytokeratin-8 (CK-8)-stained slides. Morphology and cell viability were assessed. Ex-vivo ablation resulted in clear morphological changes after RFA versus subtle differences after MR-HIFU. CK-8 staining was decreased or absent. H&E tended to underestimate the size of thermal damage. In-vivo MR-HIFU resulted in necrotic-like changes. Surprisingly, some ablated lesions were CK-8-positive. Histopathology after in-vivo RFA resembled ex-vivo RFA, with hyper-eosinophilic stroma and elongated nuclei. Lesion borders were sharp after MR-HIFU and indistinct after RFA. Histopathological differences between MR-HIFU-ablated tissue and RF-ablated tissue were demonstrated. CK-8 was more reliable for cell viability assessment than H&E when used directly after ablation, while H&E was more reliable in ablated tissue left in situ for a few days. Our results contribute to improved understanding of histopathological features in breast cancer lesions treated with minimally invasive ablative techniques. © 2016 John Wiley & Sons Ltd.

Performance of Er:YAG laser ablation of hard bone under different irrigation water cooling conditions

NASA Astrophysics Data System (ADS)

Beltrán Bernal, Lina M.; Shayeganrad, Gholamreza; Kosa, Gabor; Zelechowski, Marek; Rauter, Georg; Friederich, Niklaus; Cattin, Philippe C.; Zam, Azhar

2018-02-01

The biological applicability of the Erbium-doped Yttrium Aluminum Garnet (Er:YAG) laser in surgical processes is so far limited to hard dental tissues. Using the Er:YAG laser for bone ablation is being studied since it has shown good performance for ablating dental hard tissues at the wavelength 2.94 μm, which coincides with the absorption peak of water, one of the main components of hard tissue, like teeth and bone. To obtain a decent performance of the laser in the cutting process, we aim at examining the influence of sequenced water jet irrigation on both, the ablation rate and the prevention of carbonization while performing laser ablation of bone with fixed laser parameters. An Er:YAG laser at 2.94 μm wavelength, 940 mJ energy per pulse, 400 μs pulse width, and 10 Hz repetition rate is used for the ablation of a porcine femur bone under different pulsed water jet irrigation conditions. We used micro-computed tomography (micro-CT) scans to determine the geometry of the ablated areas. In addition, scanning electron microscopy (SEM) is used for qualitative observations for the presence of carbonization and micro-fractures on the ablated surfaces. We evaluate the performance of the laser ablation process for the different water jet conditions in terms of the ablation rate, quantified by the ablated volume per second and the ablation efficiency, calculated as the ablated volume per pulse energy. We provide an optimized system for laser ablation which delivers the appropriate amount of water to the bone and consequently, the bone is ablated in the most efficient way possible without carbonization.

Robotically assisted ablation produces more rapid and greater signal attenuation than manual ablation.

PubMed

Koa-Wing, Michael; Kojodjojo, Pipin; Malcolme-Lawes, Louisa C; Salukhe, Tushar V; Linton, Nick W F; Grogan, Aaron P; Bergman, Dale; Lim, Phang Boon; Whinnett, Zachary I; McCarthy, Karen; Ho, Siew Yen; O'Neill, Mark D; Peters, Nicholas S; Davies, D Wyn; Kanagaratnam, Prapa

2009-12-01

Robotic remote catheter ablation potentially provides improved catheter-tip stability, which should improve the efficiency of radiofrequency energy delivery. Percentage reduction in electrogram peak-to-peak voltage has been used as a measure of effectiveness of ablation. We tested the hypothesis that improved catheter-tip stability of robotic ablation can diminish signals to a greater degree than manual ablation. In vivo NavX maps of 7 pig atria were constructed. Separate lines of ablation were performed robotically and manually, recording pre- and postablation peak-to-peak voltages at 10, 20, 30, and 60 seconds and calculating signal amplitude reduction. Catheter ablation settings were constant (25W, 50 degrees , 17 mL/min, 20-30 g catheter tip pressure). The pigs were sacrificed and ablation lesions correlated with NavX maps. Robotic ablation reduced signal amplitude to a greater degree than manual ablation (49 +/- 2.6% vs 29 +/- 4.5% signal reduction after 1 minute [P = 0.0002]). The mean energy delivered (223 +/- 184 J vs 231 +/- 190 J, P = 0.42), power (19 +/- 3.5 W vs 19 +/- 4 W, P = 0.84), and duration of ablation (15 +/- 9 seconds vs 15 +/- 9 seconds, P = 0.89) was the same for manual and robotic. The mean peak catheter-tip temperature was higher for robotic (45 +/- 5 degrees C vs 42 +/- 3 degrees C [P < 0.0001]). The incidence of >50% signal reduction was greater for robotic (37%) than manual (21%) ablation (P = 0.0001). Robotically assisted ablation appears to be more effective than manual ablation at signal amplitude reduction, therefore may be expected to produce improved clinical outcomes.

Carbon Dioxide Laser Ablation of Basal Cell Carcinoma with Visual Guidance by Reflectance Confocal Microscopy: A Proof of Principle Pilot Study

PubMed Central

Hibler, B.P.; Sierra, H.; Cordova, M.; Phillips, W.; Rajadhyaksha, M.; Nehal, K.S.; Rossi, A.M.

2016-01-01

Background Laser ablation is an alternative, non-surgical treatment modality for low-risk basal cell carcinoma (BCC); however, lack of confirmative tumour destruction or residual tumour presence has been a limiting factor to adoption. Reflectance confocal microscopy (RCM) provides non-invasive, cellular-level resolution imaging of the skin and is capable of identifying tumour. Objective To evaluate the use of RCM to guide carbon dioxide (CO2) laser ablation of BCC, confirm destruction, and correlate findings with histology. Methods RCM was used pre-ablation to evaluate for features of BCC. Ablation was performed with a CO2 laser, and the response rapidly assessed using handheld RCM to evaluate for residual tumour. Confirmative pathology was used to verify confocal imaging. Results RCM imaging identified tumour pre-ablation with features not identified on normal, surrounding skin. Post-ablation, RCM documented complete removal of tumour in six cases and residual tumour in two. Histologic examination identified the ablated area and confirmed clearance of tumour in the six aforementioned cases and corroborated confocal findings for residual tumour in the other two cases. Conclusions We report successful treatment of superficial and nodular BCC using CO2 laser ablation augmented by RCM imaging for pre-ablation guidance and verification of tumour removal post-ablation. Akin to complete circumferential and deep margin control techniques, using RCM helps to map peripheral and deep BCC margins to hone in on areas exhibiting persistent tumour after ablation. CO2 laser ablation visually guided by RCM can help circumvent previously cited limiting factors of laser ablation for tumour destruction by providing cellular-level resolution imaging of tumour and margin assessment in between each laser pass and post-ablation. PMID:26800657

Dynamical analysis of surface-insulated planar wire array Z-pinches

NASA Astrophysics Data System (ADS)

Li, Yang; Sheng, Liang; Hei, Dongwei; Li, Xingwen; Zhang, Jinhai; Li, Mo; Qiu, Aici

2018-05-01

The ablation and implosion dynamics of planar wire array Z-pinches with and without surface insulation are compared and discussed in this paper. This paper first presents a phenomenological model named the ablation and cascade snowplow implosion (ACSI) model, which accounts for the ablation and implosion phases of a planar wire array Z-pinch in a single simulation. The comparison between experimental data and simulation results shows that the ACSI model could give a fairly good description about the dynamical characteristics of planar wire array Z-pinches. Surface insulation introduces notable differences in the ablation phase of planar wire array Z-pinches. The ablation phase is divided into two stages: insulation layer ablation and tungsten wire ablation. The two-stage ablation process of insulated wires is simulated in the ACSI model by updating the formulas describing the ablation process.

Ventricular fibrillation occurring after atrioventricular node ablation despite minimal difference between pre- and post-ablation heart rates.

PubMed

Squara, F; Theodore, G; Scarlatti, D; Ferrari, E

2017-02-01

We report the case of an 82-year-old man presenting with ventricular fibrillation (VF) occurring acutely after atrioventricular node (AVN) ablation. This patient had severe valvular cardiomyopathy, chronic atrial fibrillation (AF), and underwent prior to the AVN ablation a biventricular implantable cardiac defibrillator positioning. The VF was successfully cardioverted with one external electrical shock. What makes this presentation original is that the pre-ablation spontaneous heart rate in AF was slow (84 bpm), and that VF occurred after ablation despite a minimal heart rate drop of only 14 bpm. VF is the most feared complication of AVN ablation, but it had previously only been described in case of acute heart rate drop after ablation of at least 30 bpm (and more frequently>50 bpm). This case report highlights the fact that VF may occur after AVN ablation regardless of the heart rate drop, rendering temporary fast ventricular pacing mandatory whatever the pre-ablation heart rate. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Ablation of aluminum nitride films by nanosecond and femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly; Tzou, Robert; Salakhutdinov, Ildar; Danylyuk, Yuriy; McCullen, Erik; Auner, Gregory

2009-02-01

We present results of comparative study of laser-induced ablation of AlN films with variable content of oxygen as a surface-doping element. The films deposited on sapphire substrate were ablated by a single nanosecond pulse at wavelength 248 nm, and by a single femtosecond pulse at wavelength 775 nm in air at normal pressure. Ablation craters were inspected by AFM and Nomarski high-resolution microscope. Irradiation by nanosecond pulses leads to a significant removal of material accompanied by extensive thermal effects, chemical modification of the films around the ablation craters and formation of specific defect structures next to the craters. Remarkable feature of the nanosecond experiments was total absence of thermo-mechanical fracturing near the edges of ablation craters. The femtosecond pulses produced very gentle ablation removing sub-micrometer layers of the films. No remarkable signs of thermal, thermo-mechanical or chemical effects were found on the films after the femtosecond ablation. We discuss mechanisms responsible for the specific ablation effects and morphology of the ablation craters.

TPS Ablator Technologies for Interplanetary Spacecraft

NASA Technical Reports Server (NTRS)

Curry, Donald M.

2004-01-01

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

Noninvasive Assessment of Tissue Heating During Cardiac Radiofrequency Ablation Using MRI Thermography

PubMed Central

Kolandaivelu, Aravindan; Zviman, Menekhem M.; Castro, Valeria; Lardo, Albert C.; Berger, Ronald D.; Halperin, Henry R.

2010-01-01

Background Failure to achieve properly localized, permanent tissue destruction is a common cause of arrhythmia recurrence after cardiac ablation. Current methods of assessing lesion size and location during cardiac radiofrequency ablation are unreliable or not suited for repeated assessment during the procedure. MRI thermography could be used to delineate permanent ablation lesions because tissue heating above 50°C is the cause of permanent tissue destruction during radiofrequency ablation. However, image artifacts caused by cardiac motion, the ablation electrode, and radiofrequency ablation currently pose a challenge to MRI thermography in the heart. In the current study, we sought to demonstrate the feasibility of MRI thermography during cardiac ablation. Methods and Results An MRI-compatible electrophysiology catheter and filtered radiofrequency ablation system was used to perform ablation in the left ventricle of 6 mongrel dogs in a 1.5-T MRI system. Fast gradient-echo imaging was performed before and during radiofrequency ablation, and thermography images were derived from the preheating and postheating images. Lesion extent by thermography was within 20% of the gross pathology lesion. Conclusions MR thermography appears to be a promising technique for monitoring lesion formation and may allow for more accurate placement and titration of ablation, possibly reducing arrhythmia recurrences. PMID:20657028

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

PubMed

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

2018-05-11

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

Automated planning of ablation targets in atrial fibrillation treatment

NASA Astrophysics Data System (ADS)

Keustermans, Johannes; De Buck, Stijn; Heidbüchel, Hein; Suetens, Paul

2011-03-01

Catheter based radio-frequency ablation is used as an invasive treatment of atrial fibrillation. This procedure is often guided by the use of 3D anatomical models obtained from CT, MRI or rotational angiography. During the intervention the operator accurately guides the catheter to prespecified target ablation lines. The planning stage, however, can be time consuming and operator dependent which is suboptimal both from a cost and health perspective. Therefore, we present a novel statistical model-based algorithm for locating ablation targets from 3D rotational angiography images. Based on a training data set of 20 patients, consisting of 3D rotational angiography images with 30 manually indicated ablation points, a statistical local appearance and shape model is built. The local appearance model is based on local image descriptors to capture the intensity patterns around each ablation point. The local shape model is constructed by embedding the ablation points in an undirected graph and imposing that each ablation point only interacts with its neighbors. Identifying the ablation points on a new 3D rotational angiography image is performed by proposing a set of possible candidate locations for each ablation point, as such, converting the problem into a labeling problem. The algorithm is validated using a leave-one-out-approach on the training data set, by computing the distance between the ablation lines obtained by the algorithm and the manually identified ablation points. The distance error is equal to 3.8+/-2.9 mm. As ablation lesion size is around 5-7 mm, automated planning of ablation targets by the presented approach is sufficiently accurate.

Thermal distribution of microwave antenna for atrial fibrillation catheter ablation.

PubMed

Zhang, Huijuan; Nan, Qun; Liu, Youjun

2013-09-01

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

Increase in pulmonary arterial pressure after atrial fibrillation ablation: incidence and associated findings.

PubMed

Witt, Chance M; Fenstad, Eric R; Cha, Yong-Mei; Kane, Garvan C; Kushwaha, Sudhir S; Hodge, David O; Asirvatham, Samuel J; Oh, Jae K; Packer, Douglas L; Powell, Brian D

2014-06-01

The stiff left atrial (LA) syndrome is defined as pulmonary hypertension (PH) secondary to reduced LA compliance and has recently been shown to be one cause of PH after atrial fibrillation (AF) ablation. We aimed to determine the incidence of an increase in pulmonary arterial (PA) pressure post-ablation and examine the clinical and echocardiographic associations. Patients who underwent AF ablation between 1999 and 2011 were included if they had both an echocardiogram pre-ablation and 3 months post-ablation. Patients were then separated into two groups with the increased PA pressure group defined as patients with >10 mmHg increase in right ventricular systolic pressure (RVSP) post-ablation and a post-ablation RVSP >35 mmHg. Of the 499 patients meeting the study criteria, 41 (8.2%) had an increase in RVSP >10 mmHg and RVSP >35 mmHg post-ablation. On echocardiogram, the two groups had similar E/A and E/e' ratios pre-ablation. However, post-ablation, the increased PA pressure group had higher E/A (2.12 vs. 1.49, p < 0.01) and E/e' (14.7 vs. 11.2, p < 0.01) ratios. LA expansion index values were lower in the increased PA pressure group pre-ablation (51 vs. 92%, p < 0.01), but not significantly different post-ablation (82 vs. 88%, p = 0.44). Around 8% of patients develop an increase in estimated PA pressure after AF ablation. Echocardiographic parameters suggest that patients who develop increased PA pressure are developing (or unmasking) left ventricular diastolic dysfunction.

Ablation of "Background Tachycardia" in Long Standing Atrial Fibrillation: Improving the Outcomes by Unmasking a Residual Atrial Fibrillation Perpetuator.

PubMed

Pachón-M, José Carlos; Pachón-M, Enrique I; Santillana P, Tomas G; Lobo, Tasso Julio; Pachón, Carlos Thiene C; Pachón-M, Juán Carlos; Albornoz V, Remy Nelson; Zerpa A, Juán Carlos; Ortencio, Felipe; Arruda, Mauricio

2017-01-01

Catheter ablation of long-standing persistent AF (LSAF) remains challenging. Since AF-Nest (AFN) description, we have observed that a stable, protected, fast source firing, namely "Background Tachycardia"(BT), could be hidden beneath the chaotic AF. Following pulmonary vein isolation (PVI)+AFN ablation one or more BT may arise or be induced in 30-40% of patients, which could be the culprit forAF maintenance and ablation recurrences. We studied 114 patients, from 322 sequential LSAF regular ablations, having spontaneous or induced residual BT after EGM-guided PVI+AFN ablation of LSAF; 55.6±11y/o, 97males (85.1%), EF=65.5±8%, LA=42.8±6.7mm. Macroreentrant tachycardias were excluded. Pre-ablationAF 12-leads ECG Digital processing(DP) and spectral analysis(SA) was performed searching for BT before AF ablation and its correlation with BT during ablation.After PVI, 38.1±9 AFN sites/patient and 135 sustained BTs (1-3, 1.2±0.5/patient) were ablated. BT cycle length(CL) was 246.3±37.3ms. In 79 patients presenting suitable DP for SA, the BT-CL was 241.6±34.3ms with intra procedure BT-CL correlation r=0.83/p<0.01. Following BT ablation, AF could not be induced. During FU of 13→60 months(22.8±12m), AF freedom for BT RF(+) vs. BT RF(-) groups were 77.9% vs. 56.4% (p=0.009), respectively. There was no significant complication. BT ablation following PVI and AFN ablation improved long-term outcomes ofLSAF ablation. BT is likely due to sustained microreentry, protected during AF by entry block. BT can be suspected by spectral analysis of the pre-ablation ECG and is likely one important AF perpetuator by causing electrical resonance of the AFN. This ablation strategy warrants randomized, multicenter investigation.

Brain Emboli After Left Ventricular Endocardial Ablation.

PubMed

Whitman, Isaac R; Gladstone, Rachel A; Badhwar, Nitish; Hsia, Henry H; Lee, Byron K; Josephson, S Andrew; Meisel, Karl M; Dillon, William P; Hess, Christopher P; Gerstenfeld, Edward P; Marcus, Gregory M

2017-02-28

Catheter ablation for ventricular tachycardia and premature ventricular complexes (PVCs) is common. Catheter ablation of atrial fibrillation is associated with a risk of cerebral emboli attributed to cardioversions and numerous ablation lesions in the low-flow left atrium, but cerebral embolic risk in ventricular ablation has not been evaluated. We enrolled 18 consecutive patients meeting study criteria scheduled for ventricular tachycardia or PVC ablation over a 9-month period. Patients undergoing left ventricular (LV) ablation were compared with a control group of those undergoing right ventricular ablation only. Patients were excluded if they had implantable cardioverter defibrillators or permanent pacemakers. Radiofrequency energy was used for ablation in all cases and heparin was administered with goal-activated clotting times of 300 to 400 seconds for all LV procedures. Pre- and postprocedural brain MRI was performed on each patient within a week of the ablation procedure. Embolic infarcts were defined as new foci of reduced diffusion and high signal intensity on fluid-attenuated inversion recovery brain MRI within a vascular distribution. The mean age was 58 years, half of the patients were men, half had a history of hypertension, and the majority had no known vascular disease or heart failure. LV ablation was performed in 12 patients (ventricular tachycardia, n=2; PVC, n=10) and right ventricular ablation was performed exclusively in 6 patients (ventricular tachycardia, n=1; PVC, n=5). Seven patients (58%) undergoing LV ablation experienced a total of 16 cerebral emboli, in comparison with zero patients undergoing right ventricular ablation ( P =0.04). Seven of 11 patients (63%) undergoing a retrograde approach to the LV developed at least 1 new brain lesion. More than half of patients undergoing routine LV ablation procedures (predominately PVC ablations) experienced new brain emboli after the procedure. Future research is critical to understanding the long-term consequences of these lesions and to determining optimal strategies to avoid them. © 2017 American Heart Association, Inc.

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, D.N.

1996-09-24

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

Dual beam optical system for pulsed laser ablation film deposition

DOEpatents

Mashburn, Douglas N.

1996-01-01

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

Ion acceleration enhanced by target ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, S.; State Key Laboratory of Nuclear Physics and Technology, and Key Lab of HEDPS, CAPT, Peking University, Beijing 100871; Institute of Radiation, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden

2015-07-15

Laser proton acceleration can be enhanced by using target ablation, due to the energetic electrons generated in the ablation preplasma. When the ablation pulse matches main pulse, the enhancement gets optimized because the electrons' energy density is highest. A scaling law between the ablation pulse and main pulse is confirmed by the simulation, showing that for given CPA pulse and target, proton energy improvement can be achieved several times by adjusting the target ablation.

Biophysics and pathology of catheter energy delivery systems.

PubMed

Nath, S; Haines, D E

1995-01-01

Catheter ablation has rapidly emerged as the treatment of choice for many symptomatic cardiac arrhythmias. The initial experience with catheter ablation used high-energy DC as the energy source. However, over the last several years radiofrequency (RF) catheter ablation has become the dominant mode of energy delivery. Currently, a major limitation of RF ablation is the small lesion size created by this technique that has reduced its success rate in ablation of larger arrhythmogenic substrates such as coronary artery disease-related ventricular tachycardia. Alternate energy sources such as microwave or ultrasound catheter ablation are being developed that have the potential for producing larger lesions than RF ablation. This review will discuss the biophysics and pathophysiology of the various energy modalities used in catheter ablation.

Biophysics and clinical utility of irrigated-tip radiofrequency catheter ablation.

PubMed

Houmsse, Mahmoud; Daoud, Emile G

2012-01-01

Catheter ablation by radiofrequency (RF) energy has successfully eliminated cardiac tachyarrhythmias. RF ablation lesions are created by thermal energy. Electrode catheters with 4-mm-tips have been adequate to ablate arrhythmias located near the endocardium; however, the 4-mm-tip electrode does not readily ablate deeper tachyarrhythmia substrate. With 8- and 10-mm-tip RF electrodes, ablation lesions were larger; yet, these catheters are associated with increased risk for coagulum, char and thrombus formation, as well as myocardial steam rupture. Cooled-tip catheter technology was designed to cool the electrode tip, prevent excessive temperatures at the electrode tip-tissue interface, and thus allow continued delivery of RF current into the surrounding tissue. This ablation system creates larger and deeper ablation lesions and minimizes steam pops and thrombus formation. The purpose of this article is to review cooled-tip RF ablation biophysics and outcomes of clinical studies as well as to discuss future technological improvements.

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

NASA Astrophysics Data System (ADS)

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 dentin and enamel: relationship between laser fluence and ablation efficiency.

PubMed

Chen, Hu; Liu, Jing; Li, Hong; Ge, Wenqi; Sun, Yuchun; Wang, Yong; Lü, Peijun

2015-02-01

The objective was to study the relationship between laser fluence and ablation efficiency of a femtosecond laser with a Gaussian-shaped pulse used to ablate dentin and enamel for prosthodontic tooth preparation. A diode-pumped thin-disk femtosecond laser with wavelength of 1025 nm and pulse width of 400 fs was used for the ablation of dentin and enamel. The laser spot was guided in a line on the dentin and enamel surfaces to form a groove-shaped ablation zone under a series of laser pulse energies. The width and volume of the ablated line were measured under a three-dimensional confocal microscope to calculate the ablation efficiency. Ablation efficiency for dentin reached a maximum value of 0.020 mm3∕J when the laser fluence was set at 6.51 J∕cm2. For enamel, the maximum ablation efficiency was 0.009 mm3∕J at a fluence of 7.59 J∕cm2.Ablation efficiency of the femtosecond laser on dentin and enamel is closely related to the laser fluence and may reach a maximum when the laser fluence is set to an appropriate value. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

Enhanced Radiofrequency Ablation With Magnetically Directed Metallic Nanoparticles.

PubMed

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.

Five seconds of 50-60 W radio frequency atrial ablations were transmural and safe: an in vitro mechanistic assessment and force-controlled in vivo validation.

PubMed

Bhaskaran, Abhishek; Chik, William; Pouliopoulos, Jim; Nalliah, Chrishan; Qian, Pierre; Barry, Tony; Nadri, Fazlur; Samanta, Rahul; Tran, Ying; Thomas, Stuart; Kovoor, Pramesh; Thiagalingam, Aravinda

2017-05-01

Longer procedural time is associated with complications in radiofrequency atrial fibrillation ablation. We sought to reduce ablation time and thereby potentially reduce complications. The aim was to compare the dimensions and complications of 40 W/30 s setting to that of high-power ablations (50-80 W) for 5 s in the in vitro and in vivo models. In vitro ablations-40 W/30 s were compared with 40-80 W powers for 5 s. In vivo ablations-40 W/30 s were compared with 50-80 W powers for 5 s. All in vivo ablations were performed with 10 g contact force and 30 mL/min irrigation rate. Steam pops and depth of lung lesions identified post-mortem were noted as complications. A total of 72 lesions on the non-trabeculated part of right atrium were performed in 10 Ovine. All in vitro ablations except for the 40 W/5 s setting achieved the critical lesion depth of 2 mm. For in vivo ablations, all lesions were transmural, and the lesion depths for the settings of 40 W/30 s, 50 W/5 s, 60 W/5 s, 70 W/5 s, and 80 W/5 s were 2.2 ± 0.5, 2.3 ± 0.5, 2.1 ± 0.4, 2.0 ± 0.3, and 2.3 ± 0.7 mm, respectively. The lesion depths of short-duration ablations were similar to that of the conventional ablation. Steam pops occurred in the ablation settings of 40 W/30 s and 80 W/5 s in 8 and 11% of ablations, respectively. Complications were absent in short-duration ablations of 50 and 60 W. High-power, short-duration atrial ablation was as safe and effective as the conventional ablation. Compared with the conventional 40 W/30 s setting, 50 and 60 W ablation for 5 s achieved transmurality and had fewer complications. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

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

NASA Astrophysics Data System (ADS)

Mosquera, Samuel Arba; Verma, Shwetabh

2015-07-01

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

Radiofrequency Ablation for the Treatment of Hepatocellular Carcinoma in Patients with Transjugular Intrahepatic Portosystemic Shunts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jonathan K., E-mail: jonathan.park09@gmail.com; Al-Tariq, Quazi Z., E-mail: qat200@gmail.com; Zaw, Taryar M., E-mail: taryar.zaw@gmail.com

PurposeTo assess radiofrequency (RF) ablation efficacy, as well as the patency of transjugular intrahepatic portosystemic shunts (TIPSs), in patients with hepatocellular carcinoma (HCC).Materials and MethodsRetrospective database review of patients with pre-existing TIPS undergoing RF ablation of HCC was conducted over a 159-month period ending in November 2013. TIPS patency pre- and post-RF ablation was assessed by ultrasound, angiography, and/or contrast-enhanced CT or MRI. Patient demographics and immediate post-RF ablation outcomes and complications were also reviewed.Results19 patients with 21 lesions undergoing 25 RF ablation sessions were included. Child-Pugh class A, B, and C scores were seen in 1, 13, and 5more » patients, respectively. Eleven patients (58 %) ultimately underwent liver transplantation. Immediate technical success was seen in all ablation sessions without residual tumor enhancement (100 %). No patients (0 %) suffered liver failure within 1 month of ablation. Pre-ablation TIPS patency was demonstrated in 22/25 sessions (88 %). Of 22 cases with patent TIPS prior to ablation, post-ablation patency was demonstrated in 22/22 (100 %) at immediate post-ablation imaging and in 21/22 (95 %) at last follow-up (1 patient was incidentally noted to have occlusion 31 months later). No immediate complications were observed.ConclusionAblation efficacy was similar to the cited literature values for patients without TIPS. Furthermore, TIPS patency was preserved in the majority of cases. Patients with both portal hypertension and HCC are not uncommonly encountered, and a pre-existing TIPS does not appear to be a definite contraindication for RF ablation.« less

Acute and long term outcomes of catheter ablation using remote magnetic navigation for the treatment of electrical storm in patients with severe ischemic heart failure.

PubMed

Jin, Qi; Jacobsen, Peter Karl; Pehrson, Steen; Chen, Xu

2015-03-15

Catheter ablation with remote magnetic navigation (RMN) can offer some advantages compared to manual techniques. However, the relevant clinical evidence for how RMN-guided ablation affects electrical storm (ES) due to ventricular tachycardia (VT) in patients with severe ischemic heart failure (SIHF) is still limited. Forty consecutive SIHF patients (left ventricular ejection fraction, 21 ± 6.9%) presenting with ES underwent ablation using RMN. All the patients received implantable cardioverter-defibrillators (ICDs) either before or after ablation. Acute ablation success was defined as noninducibility of any sustained monophasic VT at the end of the procedure. Long-term analysis addressed VT recurrence, ICD therapies and all-cause death. ES was acutely suppressed by ablation in all patients. Acute ablation success was obtained in 32 of 40 (80%) patients. The procedure time and fluoroscopy time were 105 ± 27 min and 7.5 ± 4.8 min respectively. No major complications occurred during procedures. During a mean follow-up of 17.4 months, 19 patients (47.5%) remained free of VT recurrence. The percentage of patients receiving ICD shocks after ablation was lower than before ablation (30% vs 69%, P<0.01). The mean number of ICD shocks per individual per year was reduced from 4.3 before ablation to 1.9 after ablation (P<0.05). Ten patients died during follow-up. Acute catheter ablation with RMN is safe and effective to suppress ES in SIHF patients. RMN-guided catheter ablation can prevent VT recurrence and significantly reduce ICD shocks, suggesting that this strategy can be used as an alternative therapy for VT storm in SIHF patients with ICDs. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

The Femtosecond Laser Ablation on Ultrafine-Grained Copper

NASA Astrophysics Data System (ADS)

Lu, Jianxun; Wu, Xiaoyu; Ruan, Shuangchen; Guo, Dengji; Du, Chenlin; Liang, Xiong; Wu, Zhaozhi

2018-07-01

To investigate the effects of femtosecond laser ablation on the surface morphology and microstructure of ultrafine-grained copper, point, single-line scanning, and area scanning ablation of ultrafine-grained and coarse-grained copper were performed at room temperature. The ablation threshold gradually increased and materials processing became more difficult with decreasing grain size. In addition, the ablation depth and width of the channels formed by single-line scanning ablation gradually increased with increasing grain size for the same laser pulse energy. The microhardness of the ablated specimens was also evaluated as a function of laser pulse energy using area scanning ablation. The microhardness difference before and after ablation increased with decreasing grain size for the same laser pulse energy. In addition, the microhardness after ablation gradually decreased with increasing laser pulse energy for the ultrafine-grained specimens. However, for the coarse-grained copper specimens, no clear changes of the microhardness were observed after ablation with varying laser pulse energies. The grain sizes of the ultrafine-grained specimens were also surveyed as a function of laser pulse energy using electron backscattered diffraction (EBSD). The heat generated by laser ablation caused recrystallization and grain growth of the ultrafine-grained copper; moreover, the grain size gradually increased with increasing pulse energy. In contrast, no obvious changes in grain size were observed for the coarse-grained copper specimens with increasing pulse energy.

The Femtosecond Laser Ablation on Ultrafine-Grained Copper

NASA Astrophysics Data System (ADS)

Lu, Jianxun; Wu, Xiaoyu; Ruan, Shuangchen; Guo, Dengji; Du, Chenlin; Liang, Xiong; Wu, Zhaozhi

2018-05-01

To investigate the effects of femtosecond laser ablation on the surface morphology and microstructure of ultrafine-grained copper, point, single-line scanning, and area scanning ablation of ultrafine-grained and coarse-grained copper were performed at room temperature. The ablation threshold gradually increased and materials processing became more difficult with decreasing grain size. In addition, the ablation depth and width of the channels formed by single-line scanning ablation gradually increased with increasing grain size for the same laser pulse energy. The microhardness of the ablated specimens was also evaluated as a function of laser pulse energy using area scanning ablation. The microhardness difference before and after ablation increased with decreasing grain size for the same laser pulse energy. In addition, the microhardness after ablation gradually decreased with increasing laser pulse energy for the ultrafine-grained specimens. However, for the coarse-grained copper specimens, no clear changes of the microhardness were observed after ablation with varying laser pulse energies. The grain sizes of the ultrafine-grained specimens were also surveyed as a function of laser pulse energy using electron backscattered diffraction (EBSD). The heat generated by laser ablation caused recrystallization and grain growth of the ultrafine-grained copper; moreover, the grain size gradually increased with increasing pulse energy. In contrast, no obvious changes in grain size were observed for the coarse-grained copper specimens with increasing pulse energy.

Heat sink phenomenon of bipolar and monopolar radiofrequency ablation observed using polypropylene tubes for vessel simulation.

PubMed

Al-Alem, Ihssan; Pillai, Krishna; Akhter, Javed; Chua, Terence C; Morris, David L

2014-06-01

Radiofrequency ablation (RFA) is widely used for treating liver tumors; recurrence is common owing to proximity to blood vessels possibly due to the heat sink effect. We seek to investigate this phenomenon using unipolar and bipolar RFA on an egg white tumor tissue model and an animal liver model. Temperature profiles during ablation (with and without vessel simulation) were studied, using both bipolar and unipolar RFA probes by 4 strategically placed temperature leads to monitor temperature profile during ablation. The volume of ablated tissue was also measured. The volume ablated during vessel simulation confirmed the impact of the heat sink phenomenon. The heat sink effect of unipolar RFA was greater compared with bipolar RFA (ratio of volume affected 2:1) in both tissue and liver models. The volume ablated using unipolar RFA was less than the bipolar RFA (ratio of volume ablated = 1:4). Unipolar RFA achieved higher ablation temperatures (122°C vs 98°C). Unipolar RFA resulted in tissue damage beyond the vessel, which was not observed using bipolar RFA. Bipolar RFA ablates a larger tumor volume compared with unipolar RFA, with a single ablation. The impact of heat sink phenomenon in tumor ablation is less so with bipolar than unipolar RFA with sparing of adjacent vessel damage. © The Author(s) 2013.

Selective rear side ablation of thin nickel-chromium-alloy films using ultrashort laser pulses

NASA Astrophysics Data System (ADS)

Pabst, Linda; Ullmann, Frank; Ebert, Robby; Exner, Horst

2018-03-01

In recent years, the selective laser structuring from the transparent substrate side plays an increased role in thin film processing. The rear side ablation is a highly effective ablation method for thin film structuring and revels a high structuring quality. Therefore, the rear side ablation of nickel-chromium-alloy thin films on glass substrate was investigated using femtosecond laser irradiation. Single and multiple pulses ablation thresholds as well as the incubation coefficient were determined. By irradiation from the transparent substrate side at low fluences a cracking or a partly delamination of the film could be observed. By increasing the fluence the most part of the film was ablated, however, a very thin film remained at the interface of the glass substrate. This thin remaining layer could be completely ablated by two pulses. A further increase of the pulse number had no influence on the ablation morphology. The ablated film was still intact and an entire disc or fragments could be collected near the ablation area. The fragments showed no morphology change and were still in solid state.

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation of liver tumours.

PubMed

Wijlemans, J W; Bartels, L W; Deckers, R; Ries, M; Mali, W P Th M; Moonen, C T W; van den Bosch, M A A J

2012-09-28

Recent decades have seen a paradigm shift in the treatment of liver tumours from invasive surgical procedures to minimally invasive image-guided ablation techniques. Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a novel, completely non-invasive ablation technique that has the potential to change the field of liver tumour ablation. The image guidance, using MR imaging and MR temperature mapping, provides excellent planning images and real-time temperature information during the ablation procedure. However, before clinical implementation of MR-HIFU for liver tumour ablation is feasible, several organ-specific challenges have to be addressed. In this review we discuss the MR-HIFU ablation technique, the liver-specific challenges for MR-HIFU tumour ablation, and the proposed solutions for clinical translation.

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablation of liver tumours

PubMed Central

Bartels, L.W.; Deckers, R.; Ries, M.; Mali, W.P.Th.M.; Moonen, C.T.W.; van den Bosch, M.A.A.J.

2012-01-01

Abstract Recent decades have seen a paradigm shift in the treatment of liver tumours from invasive surgical procedures to minimally invasive image-guided ablation techniques. Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a novel, completely non-invasive ablation technique that has the potential to change the field of liver tumour ablation. The image guidance, using MR imaging and MR temperature mapping, provides excellent planning images and real-time temperature information during the ablation procedure. However, before clinical implementation of MR-HIFU for liver tumour ablation is feasible, several organ-specific challenges have to be addressed. In this review we discuss the MR-HIFU ablation technique, the liver-specific challenges for MR-HIFU tumour ablation, and the proposed solutions for clinical translation. PMID:23022541

A study of angular dependence in the ablation rate of polymers by nanosecond pulses

NASA Astrophysics Data System (ADS)

Pedder, James E. A.; Holmes, Andrew S.

2006-02-01

Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.

Laparoscopic vs computerized tomography-guided radiofrequency ablation for large hepatic hemangiomas abutting the diaphragm

PubMed Central

Gao, Jun; Kong, Jian; Ding, Xue-Mei; Ke, Shan; Niu, Hai-Gang; Xin, Zong-Hai; Ning, Chun-Min; Guo, Shi-Gang; Li, Xiao-Long; Zhang, Long; Dong, Yong-Hong; Sun, Wen-Bing

2015-01-01

AIM: To compare safety and therapeutic efficacy of laparoscopic radiofrequency (RF) ablation vs computed tomography (CT)-guided RF ablation for large hepatic hemangiomas abutting the diaphragm. METHODS: We retrospectively reviewed our sequential experience of treating 51 large hepatic hemangiomas abutting the diaphragm in 51 patients by CT-guided or laparoscopic RF ablation due to either the presence of symptoms and/or the enlargement of hemangioma. Altogether, 24 hemangiomas were ablated via a CT-guided percutaneous approach (CT-guided ablation group), and 27 hemangiomas were treated via a laparoscopic approach (laparoscopic ablation group). RESULTS: The mean diameter of the 51 hemangiomas was 9.6 ± 1.8 cm (range, 6.0-12.0 cm). There was no difference in the diameter of hemangiomas between the two groups (P > 0.05). RF ablation was performed successfully in all patients. There was no difference in ablation times between groups (P > 0.05). There were 23 thoracic complications in 17 patients: 15 (62.5%, 15/24) in the CT-guided ablation group and 2 (7.4%, 2/27) in the laparoscopic ablation group (P < 0.05). According to the Dindo-Clavien classification, two complications (pleural effusion and diaphragmatic rupture grade III) were major in two patients. All others were minor (grade I). Both major complications occurred in the CT-guided ablation group. The minor complications were treated successfully with conservative measures, and the two major complications underwent treatment by chest tube drainage and thoracoscopic surgery, respectively. Complete ablation was achieved in 91.7% (22/24) and 96.3% (26/27) in the CT-guided and the laparoscopic ablation groups, respectively (P > 0.05). CONCLUSION: Laparoscopic RF ablation therapy should be used as the first-line treatment option for large hepatic hemangiomas abutting the diaphragm. It avoids thermal injury to the diaphragm and reduces thoracic complications. PMID:26019459

Efficacy and survival analysis of percutaneous radiofrequency versus microwave ablation for hepatocellular carcinoma: an Egyptian multidisciplinary clinic experience.

PubMed

Abdelaziz, Ashraf; Elbaz, Tamer; Shousha, Hend Ibrahim; Mahmoud, Sherif; Ibrahim, Mostafa; Abdelmaksoud, Ahmed; Nabeel, Mohamed

2014-12-01

Hepatocellular carcinoma (HCC) is a primary tumor of the liver with poor prognosis. For early stage HCC, treatment options include surgical resection, liver transplantation, and percutaneous ablation. Percutaneous ablative techniques (radiofrequency and microwave techniques) emerged as best therapeutic options for nonsurgical patients. We aimed to determine the safety and efficacy of radiofrequency and microwave procedures for ablation of early stage HCC lesions and prospectively follow up our patients for survival analysis. One Hundred and 11 patients with early HCC are managed in our multidisciplinary clinic using either radiofrequency or microwave ablation. Patients are assessed for efficacy and safety. Complete ablation rate, local recurrence, and overall survival analysis are compared between both procedures. Radiofrequency ablation group (n = 45) and microwave ablation group (n = 66) were nearly comparable as regards the tumor and patients characteristics. Complete ablation was achieved in 94.2 and 96.1% of patients managed by radiofrequency and microwave ablation techniques, respectively (p value 0.6) with a low rate of minor complications (11.1 and 3.2, respectively) including subcapsular hematoma, thigh burn, abdominal wall skin burn, and pleural effusion. Ablation rates did not differ between ablated lesions ≤ 3 and 3-5 cm. A lower incidence of local recurrence was observed in microwave group (3.9 vs. 13.5% in radiofrequency group, p value 0.04). No difference between both groups as regards de novo lesions, portal vein thrombosis, and abdominal lymphadenopathy. The overall actuarial probability of survival was 91.6% at 1 year and 86.1% at 2 years with a higher survival rates noticed in microwave group but still without significant difference (p value 0.49). Radiofrequency and microwave ablations led to safe and equivalent ablation and survival rates (with superiority for microwave ablation as regards the incidence of local recurrence).

Pleural Puncture that Excludes the Ablation Zone Decreases the Risk of Pneumothorax after Percutaneous Microwave Ablation in Porcine Lung

PubMed Central

Lee, Kyungmouk Steve; Takaki, Haruyuki; Yarmohammadi, Hooman; Srimathveeravalli, Govindarajan; Luchins, Kerith; Monette, Sébastien; Nair, Sreejit; Kishore, Sirish; Erinjeri, Joseph P.

2017-01-01

Purpose To test the hypothesis that the geometry of probe placement with respect to the pleural puncture site affects the risk of pneumothorax after microwave (MW) ablation in the lung. Materials and Methods Computed tomography–guided MW ablation of the lung was performed in 8 swine under general anesthesia and mechanical ventilation. The orientation of the 17-gauge probe was either perpendicular (90°) or parallel (< 30°) with respect to the pleural puncture site, and the ablation power was 30 W or 65 W for 5 minutes. After MW ablation, swine were euthanized, and histopathologic changes were assessed. Frequency and factors affecting pneumothorax were evaluated by multivariate analysis. Results Among 62 lung MW ablations, 13 (21%) pneumothoraces occurred. No statistically significant difference was noted in the rate of pneumothorax between the perpendicular and the parallel orientations of the probe (31% vs 14%; odds ratio [OR], 2.8; P = .11). The pneumothorax rate was equal for 65-W and 30-W ablation powers (21% and 21%; OR, 1.0; P = .94). Under multivariate analysis, 2 factors were independent positive predictors of pneumothorax: ablation zone inclusive of pleural insertion point (OR, 7.7; P = .02) and time since intubation (hours) (OR, 2.7; P = .02). Conclusions Geometries where the pleural puncture site excluded the ablation zone decreased pneumothorax in swine undergoing MW ablation in the lung. Treatment planning to ensure that the pleural puncture site excludes the subsequent ablation zone may reduce the rate of pneumothorax in patients undergoing MW ablation in the lung. PMID:25753501

Visualizing ex vivo radiofrequency and microwave ablation zones using electrode vibration elastography

PubMed Central

DeWall, Ryan J.; Varghese, Tomy; Brace, Chris L.

2012-01-01

Purpose: Electrode vibration elastography is a new shear wave imaging technique that can be used to visualize thermal ablation zones. Prior work has shown the ability of electrode vibration elastography to delineate radiofrequency ablations; however, there has been no previous study of delineation of microwave ablations or radiological–pathological correlations using multiple observers. Methods: Radiofrequency and microwave ablations were formed in ex vivo bovine liver tissue. Their visualization was compared on shear wave velocity and maximum displacement images. Ablation dimensions were compared to gross pathology. Elastographic imaging and gross pathology overlap and interobserver variability were quantified using similarity measures. Results: Elastographic imaging correlated with gross pathology. Correlation of area estimates was better in radiofrequency than in microwave ablations, with Pearson coefficients of 0.79 and 0.54 on shear wave velocity images and 0.90 and 0.70 on maximum displacement images for radiofrequency and microwave ablations, respectively. The absolute relative difference in area between elastographic imaging and gross pathology was 18.9% and 22.9% on shear wave velocity images and 16.0% and 23.1% on maximum displacement images for radiofrequency and microwave ablations, respectively. Conclusions: Statistically significant radiological–pathological correlation was observed in this study, but correlation coefficients were lower than other modulus imaging techniques, most notably in microwave ablations. Observers provided similar delineations for most thermal ablations. These results suggest that electrode vibration elastography is capable of imaging thermal ablations, but refinement of the technique may be necessary before it can be used to monitor thermal ablation procedures clinically. PMID:23127063

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

PubMed

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

2017-02-01

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

Atrial fibrillation ablation using cryoballoon technology: Recent advances and practical techniques.

PubMed

Chen, Shaojie; Schmidt, Boris; Bordignon, Stefano; Bologna, Fabrizio; Perrotta, Laura; Nagase, Takahiko; Chun, K R Julian

2018-04-16

Atrial fibrillation (AF) affects 1-2% of the population, and its prevalence is estimated to double in the next 50 years as the population ages. AF results in impaired patients' life quality, deteriorated cardiac function, and even increased mortality. Antiarrhythmic drugs frequently fail to restore sinus rhythm. Catheter ablation is a valuable treatment approach for AF, even as a first-line therapy strategy in selected patients. Effective electrical pulmonary vein isolation (PVI) is the cornerstone of all AF ablation strategies. Use of radiofrequency (RF) catheter in combination of a three-dimensional electroanatomical mapping system is the most established ablation approach. However, catheter ablation of AF is challenging even sometimes for experienced operators. To facilitate catheter ablation of AF without compromising the durability of the pulmonary vein isolation, "single shot" ablation devices have been developed; of them, cryoballoon ablation, is by far the most widely investigated. In this report, we review the current knowledge of AF and discuss the recent evidence in catheter ablation of AF, particularly cryoballoon ablation. Moreover, we review relevant data from the literature as well as our own experience and summarize the key procedural practical techniques in PVI using cryoballoon technology, aiming to shorten the learning curve of the ablation technique and to contribute further to reduction of the disease burden. © 2018 Wiley Periodicals, Inc.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2016-04-21

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

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

PubMed

Amasyali, Basri; Kilic, Ayhan

2015-06-01

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

Through-the-thickness selective laser ablation of ceramic coatings on soda-lime glass

NASA Astrophysics Data System (ADS)

Romoli, L.; Khan, M. M. A.; Valentini, M.

2017-05-01

This paper investigates through-thickness laser ablation characteristics of ceramic coating deposited on the bottom surface of the soda-lime glass substrate. Experimental studies were focused on determining the effects of energy density, hatch distance and coating color on the ablation completion index. Effect of glass thickness was also tested to verify the robustness of the designed process. Up to a certain threshold limit, the ablation completion index is energy-limited and has an inverse U-shape relationship with the energy density input. Since greater hatch distance means faster ablation and lesser ablation completion index, there must be a tradeoff between ablation completion index and hatch distance. During through-thickness laser ablation of ceramic coating, energy density input should be in the range of 0.049 J/mm2 - 0.251 J/mm2 for black ceramic coating and 0.112 J/mm2 - 0.251 J/mm2 for other coatings. Finally, the designed process is capable of ablating the ceramic coating effectively through varied thickness.

Pulsed laser ablation of IC packages for device failure analyses

NASA Astrophysics Data System (ADS)

Hong, Ming Hui; Mai, ZhiHong; Chen, G. X.; Thiam, Thomas; Song, Wen D.; Lu, Yongfeng; Soh, Chye E.; Chong, Tow Chong

2002-06-01

Pulsed laser ablation of mold compounds for IC packaging in air and with steam assistance is investigated. It is applied to decap IC packages and expose computer CPU dies for the device failure analyses. Compared with chemical decapping, the laser ablation has advantages of being fast speed, non- contact and dry processing. Laser ablation with the steam assistance results in higher ablation rate and wider ablated crater with much smoother surface morphology. It implies that the steam assisted laser ablation can achieve a faster and better quality laser processing. Audible acoustic wave and plasma optical signal diagnostics are also carried out to have a better understanding of the mechanisms behind. Light wavelength and laser fluence applied in the decapping are two important parameters. The 532 nm Nd:YAG laser decapping at a low laser fluence can achieve a large decapping area with a fine ablation profile. IC packages decapped by the laser ablation show good quality for the device failure analyses.

Effect of bromine-dopant on radiation-driven Rayleigh-Taylor instability in plastic foil

NASA Astrophysics Data System (ADS)

Xu, Binbin; Ma, Yanyun; Yang, Xiaohu; Tang, Wenhui; Ge, Zheyi; Zhao, Yuan; Ke, Yanzhao; Kawata, Shiego

2017-10-01

Effects of bromine (Br) dopant on the growth of radiation-driven ablative Rayleigh-Taylor instability (RTI) in plastic foils are studied by radiation hydrodynamics simulations and theoretical analysis. It is found that the Br-dopant in plastic foil reduces the seed of ablative RTI. The main reasons of the reduction are attributed to the smaller oscillation amplitude of ablative Richtmyer-Meshkov instability (RMI) induced by the smaller post-shock sound speed, and the smaller oscillation frequency of ablative RMI induced by the smaller ablation velocity and blow-off plasma velocity. The Br-dopant also decreases the linear growth rate of ablative RTI due to the smaller acceleration. Treating the perturbation growth as a function of foil’s displacement, the perturbation growth would increase in Br-doped foil at the phase of ablative RTI, which is attributed to the decrease of the ablation velocity and the density gradient scale length. The results are helpful for further understanding the influence of high-Z dopant on the radiation-driven ablative RTI.

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

NASA Technical Reports Server (NTRS)

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

1973-01-01

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

Determination of excimer laser ablation rate of the human cornea using in vivo Scheimpflug videography.

PubMed

Huebscher, H J; Genth, U; Seiler, T

1996-01-01

To determine in vivo the amount of human corneal tissue removed by each excimer laser pulse, the so-called ablation rate, during photorefractive keratectomy (PRK). There is confusion in the literature because the experimentally determined ablation rate of 0.4 to 0.5 microns per pulse differs from the nominal ablation rate of 0.23 to 0.3 microns per pulse, which is the value used in clinical procedures. Eleven eyes of 11 patients were treated with PRK for correction of myopia. The corneal curvature was determined by Scheimpflug videography before and immediately after surgery. Starting from this curvature change, the authors calculated the real ablation rate. The real ablation rate is coincident with the nominal ablation rate and differs significantly from the ablation rate derived from deep keratectomy experiments. The outer layers of the cornea show significantly different ablation behavior than the deeper stroma. This information has clinical relevance for the predictability of intrastromal excimer laser procedures.

Monitoring of tissue ablation using time series of ultrasound RF data.

PubMed

Imani, Farhad; Wu, Mark Z; Lasso, Andras; Burdette, Everett C; Daoud, Mohammad; Fitchinger, Gabor; Abolmaesumi, Purang; Mousavi, Parvin

2011-01-01

This paper is the first report on the monitoring of tissue ablation using ultrasound RF echo time series. We calcuate frequency and time domain features of time series of RF echoes from stationary tissue and transducer, and correlate them with ablated and non-ablated tissue properties. We combine these features in a nonlinear classification framework and demonstrate up to 99% classification accuracy in distinguishing ablated and non-ablated regions of tissue, in areas as small as 12mm2 in size. We also demonstrate significant improvement of ablated tissue classification using RF time series compared to the conventional approach of using single RF scan lines. The results of this study suggest RF echo time series as a promising approach for monitoring ablation, and capturing the changes in the tissue microstructure as a result of heat-induced necrosis.

Simulations of Neon Pellets for Plasma Disruption Mitigation in Tokamaks

NASA Astrophysics Data System (ADS)

Bosviel, Nicolas; Samulyak, Roman; Parks, Paul

2017-10-01

Numerical studies of the ablation of neon pellets in tokamaks in the plasma disruption mitigation parameter space have been performed using a time-dependent pellet ablation model based on the front tracking code FronTier-MHD. The main features of the model include the explicit tracking of the solid pellet/ablated gas interface, a self-consistent evolving potential distribution in the ablation cloud, JxB forces, atomic processes, and an improved electrical conductivity model. The equation of state model accounts for atomic processes in the ablation cloud as well as deviations from the ideal gas law in the dense, cold layers of neon gas near the pellet surface. Simulations predict processes in the ablation cloud and pellet ablation rates and address the sensitivity of pellet ablation processes to details of physics models, in particular the equation of state.

[Effect of low-dose focused ultrasound pre-irradiation versus microbubbles for enhancing high-intensity focused ultrasound ablation of VX2 hepatic tumor in rabbits].

PubMed

Zhang, Yi; Yang, Chao; Zou, Jian-Zhong; Chen, Fei; Ou, Xia; Zou, Hai-Rong; Wang, Yan

2016-10-20

To compare the effect of low-dose focused ultrasound pre-irradiation and microbubbles for enhancing the ablation effect of high intensity focused ultrasound (HIFU) on VX 2 hepatic tumor in rabbits. Fifty-five rabbits bearing VX 2 hepatic tumor were randomly divided into low-dose pre-irradiation + HIFU ablation group, microbubbles+HIFU ablation group, and HIFU ablation group for corresponding treatments. The pathological changes in the tumors after low-dose irradiation, time for HIFU ablation, tumor volume with coagulative necrosis, energy efficiency factor (EEF), pathological changes in the ablated tumor, and sound channel of HIFU ablation were observed. Tumor cell edema, vacuolar changes in the cytoplasm and tumor interstitial vascular congestion were observed 24 h after low-dose pre-irradiation. The ablation time were significantly shorter, coagulative necrosis volume was larger, and EEF was lower in low-dose irradiation + HIFU ablation group and microbubbles+HIFU ablation group than in simple HIFU ablation group (P<0.05), but the differences between the former two groups were not significant. The effectiveness and stability of the synergistic effect of low-dose pre-irradiation were inferior to microbubbles, but the former ensured a better safety of the sound channel. Low-dose irradiation has comparable synergistic effect in HIFU with microbubbles with such advantages as non-invasiveness, high concentration and good safety, and can be a potentially new method to enhance the efficiency of HIFU.

Perioral Rejuvenation With Ablative Erbium Resurfacing.

PubMed

Cohen, Joel L

2015-11-01

Since the introduction of the scanning full-field erbium laser, misconceptions regarding ablative erbium resurfacing have resulted in its being largely overshadowed by ablative fractional resurfacing. This case report illustrates the appropriateness of full-field erbium ablation for perioral resurfacing. A patient with profoundly severe perioral photodamage etched-in lines underwent full-field ablative perioral resurfacing with an erbium laser (Contour TRL, Sciton Inc., Palo Alto, CA) that allows separate control of ablation and coagulation. The pre-procedure consultations included evaluation of the severity of etched-in lines, and discussion of patient goals, expectations, and appropriate treatment options, as well as a review of patient photos and post-treatment care required. The author generally avoids full-field erbium ablation in patients with Fitzpatrick type IV and above. For each of 2 treatment sessions (separated by approximately 4 months), the patient received (12 cc plain 2% lidodaine) sulcus blocks before undergoing 4 passes with the erbium laser at 150 μ ablation, no coagulation, and then some very focal 30 μ ablation to areas of residual lines still visualized through the pinpoint bleeding. Similarly, full-field ablative resurfacing can be very reliable for significant wrinkles and creping in the lower eyelid skin--where often a single treatment of 80 μ ablation, 50 μ coagulation can lead to a nice improvement. Standardized digital imaging revealed significant improvement in deeply etched rhytides without significant adverse events. For appropriately selected patients requiring perioral (or periorbital) rejuvenation, full-field ablative erbium resurfacing is safe, efficacious and merits consideration.

Comparison of microbubble presence in the right heart during mechanochemical and radiofrequency ablation for varicose veins.

PubMed

Moon, K H; Dharmarajah, B; Bootun, R; Lim, C S; Lane, Tra; Moore, H M; Sritharan, K; Davies, A H

2017-07-01

Objective Mechanochemical ablation is a novel technique for ablation of varicose veins utilising a rotating catheter and liquid sclerosant. Mechanochemical ablation and radiofrequency ablation have no reported neurological side-effect but the rotating mechanism of mechanochemical ablation may produce microbubbles. Air emboli have been implicated as a cause of cerebrovascular events during ultrasound-guided foam sclerotherapy and microbubbles in the heart during ultrasound-guided foam sclerotherapy have been demonstrated. This study investigated the presence of microbubbles in the right heart during varicose vein ablation by mechanochemical abaltion and radiofrequency abaltion. Methods Patients undergoing great saphenous vein ablation by mechanochemical abaltion or radiofrequency ablation were recruited. During the ablative procedure, the presence of microbubbles was assessed using transthoracic echocardiogram. Offline blinded image quantification was performed using International Consensus Criteria grading guidelines. Results From 32 recruited patients, 28 data sets were analysed. Eleven underwent mechanochemical abaltion and 17 underwent radiofrequency abaltion. There were no neurological complications. In total, 39% (11/28) of patients had grade 1 or 2 microbubbles detected. Thirty-six percent (4/11) of mechanochemical abaltion patients and 29% (5/17) of radiofrequency ablation patients had microbubbles with no significant difference between the groups ( p=0.8065). Conclusion A comparable prevalence of microbubbles between mechanochemical abaltion and radiofrequency ablation both of which are lower than that previously reported for ultrasound-guided foam sclerotherapy suggests that mechanochemical abaltion may not confer the same risk of neurological events as ultrasound-guided foam sclerotherapy for treatment of varicose veins.

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

NASA Astrophysics Data System (ADS)

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.

Factors affecting tumor ablation during high intensity focused ultrasound treatment.

PubMed

Hassanuddin, Aizan; Choi, Jun-Ho; Seo, Dong-Wan; Ryu, Choong Heon; Kim, Su-Hui; Park, Do Hyun; Lee, Sang Soo; Lee, Sung Koo; Kim, Myung-Hwan

2014-07-01

High intensity focused ultrasound (HIFU) utilizes a targeted extracorporeal focused ultrasound beam to ablate neoplastic pancreatic tissue. We used an in vitro model to examine the effects of bone, metallic stents, plastic stents, metal plates, and cyst-like lesions on HIFU treatment. HIFU was delivered to the phantom models implanted with foreign bodies, and the location, shape, and size of the ablated zones were evaluated. Bone and metallic plates reflected the ultrasound beam, shifting the ablation zone from the focal zone to the prefocal area. In the phantoms containing metal stent, plastic stent, and cyst, most of the ablative energy was reflected to the prefocal area by the surface, with the remainder penetrating through the phantom. The area of the ablated margins was significantly larger in size and volume than the intended focal ablation zone. During HIFU therapy, artificial or anatomical barriers could affect the direction of the ultrasound beams, shifting the ablation zone from the focal area to a prefocal site with a larger than expected ablation zone. These factors should be considered prior to HIFU treatment for pancreatic tumors because they could limit ablation success, in addition to causing complications.

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

PubMed Central

DeWall, Ryan J.; Varghese, Tomy

2013-01-01

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

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

PubMed

DeWall, Ryan J; Varghese, Tomy

2012-01-01

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

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

PubMed Central

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

2011-01-01

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

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

PubMed

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

2011-12-01

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

Selective Angiography Using the Radiofrequency Catheter: An Alternative Technique for Mapping and Ablation in the Aortic Cusps.

PubMed

Roca-Luque, Ivo; Rivas, Nuria; Francisco, Jaume; Perez, Jordi; Acosta, Gabriel; Oristrell, Gerard; Terricabres, Maria; Garcia-Dorado, David; Moya, Angel

2017-01-01

Ablation in aortic cusps could be necessary in up to 15% of the patients, especially in para-Hisian atrial tachycardia and ventricular arrhythmias arising from outflow tracts. Risk of coronary damage has led to recommendation of systematic coronary angiography (CA) during the procedure. Other image tests as intravascular (ICE) or transesophageal echocardiography (TEE) have been proposed. Both methods have limitations: additional vascular access for ICE and need for additional CA in some patients in case of TEE. We describe an alternative method to assess relation of catheter tip and coronary ostia during ablation in aortic cusps without additional vascular accesses by performing selective angiography with the ablation catheter. We prospectively evaluated 12 consecutive patients (69.3 ± 8.5, 6 female) who underwent ablation in right (1), left (5), and noncoronary cusps (6). We performed angiography through the ablation cooled tip radiofrequency catheter at the ablation site. Ablation was effective in 91.6% of the patients (3 patients needed additional ablation out of coronary cusps: pulmonary cusp, right ventricular outflow tract (RVOT), and coronary sinus and 1 patient underwent a second procedure because recurrence). No complications occurred neither during procedure nor follow-up (6.2 ± 3.8 months). No technical problems occurred with the ablation catheter after contrast injection. Selective angiography through a cooled-tip radiofrequency ablation catheter is feasible to assess relation of coronary ostia and ablation site when ablation in aortic cusps. It allows continuous real-time assessment of this relation, avoids the need for additional vascular accesses and no complications occurred in our series. © 2016 Wiley Periodicals, Inc.

Echo decorrelation imaging of ex vivo HIFU and bulk ultrasound ablation using image-treat arrays

NASA Astrophysics Data System (ADS)

Fosnight, Tyler R.; Hooi, Fong Ming; Colbert, Sadie B.; Keil, Ryan D.; Barthe, Peter G.; Mast, T. Douglas

2017-03-01

In this study, the ability of ultrasound echo decorrelation imaging to map and predict heat-induced cell death was tested using bulk ultrasound thermal ablation, high intensity focused ultrasound (HIFU) thermal ablation, and pulse-echo imaging of ex vivo liver tissue by a custom image-treat array. Tissue was sonicated at 5.0 MHz using either pulses of unfocused ultrasound (N=12) (7.5 s, 50.9-101.8 W/cm2 in situ spatial-peak, temporal-peak intensity) for bulk ablation or focused ultrasound (N=21) (1 s, 284-769 W/cm2 in situ spatial-peak, temporal-peak intensity and focus depth of 10 mm) for HIFU ablation. Echo decorrelation and integrated backscatter (IBS) maps were formed from radiofrequency pulse-echo images captured at 118 frames per second during 5.0 s rest periods, beginning 1.1 s after each sonication pulse. Tissue samples were frozen at -80˚C, sectioned, vitally stained, imaged, and semi-automatically segmented for receiver operating characteristic (ROC) analysis. ROC curves were constructed to assess prediction performance for echo decorrelation and IBS. Logarithmically scaled mean echo decorrelation in non-ablated and ablated tissue regions before and after electronic noise and motion correction were compared. Ablation prediction by echo decorrelation and IBS was significant for both focused and bulk ultrasound ablation. The log10-scaled mean echo decorrelation was significantly greater in regions of ablation for both HIFU and bulk ultrasound ablation. Echo decorrelation due to electronic noise and motion was significantly reduced by correction. These results suggest that ultrasound echo decorrelation imaging is a promising approach for real-time prediction of heat-induced cell death for guidance and monitoring of clinical thermal ablation, including radiofrequency ablation and HIFU.

Ablation in teeth with the free-electron laser around the absorption peak of hydroxyapatite (9.5 μm) and between 6.0 and 7.5 μm

NASA Astrophysics Data System (ADS)

Ostertag, Manfred; Walker, Rudolf; Weber, Heiner; van der Meer, Lex; McKinley, Jim T.; Tolk, Norman H.; Jean, Benedikt J.

1996-04-01

Pulsed IR laser ablation on dental hard substances was studied in the wavelength range between 9.5 and 11.5 micrometers with the Free-Electron Laser (FEL) in Nieuwegein/NL and between 6.0 and 7.5 micrometers with the FEL at Vanderbilt University in Nashville/TN. Depth, diameter and volume of the ablation crater were determined with a special silicon replica method and subsequent confocal laser topometry. The irradiated surfaces and the ejected debris were examined with an SEM 9.5 - 11.5 micrometers : depth, diameter and volume of the ablation crater are greater and the ablation threshold is lower for ablation with a wavelength corresponding to the absorption max. of hydroxyapatite (9.5 micrometers ), compared to ablation at wavelengths with lower absorption (10.5 - 11.5 micrometers ). For all wavelengths, no thermal cracking can be observed after ablation in dentine, however a small amount of thermal cracking can be observed after ablation in enamel. After ablation at 9.5 micrometers , a few droplets of solidified melt were seen on the irradiated areas, whereas the debris consisted only of solidified melt. In contrast, the surface and the debris obtained from ablation using the other wavelengths showed the natural structure of dentine 6.0 - 7.5 micrometers : the depth of the ablation crater increases and the ablation threshold decreases for an increasing absorption coefficient of the target material. Different tissue components absorbed the laser radiation of different wavelengths (around 6.0 micrometers water and collagen, 6.5 micrometers collagen and water, 7.0 micrometers carbonated hydroxyapatite). Nevertheless the results have shown no major influence on the primary tissue absorber.

Measurement of intrahepatic pressure during radiofrequency ablation in porcine liver.

PubMed

Kawamoto, Chiaki; Yamauchi, Atsushi; Baba, Yoko; Kaneko, Keiko; Yakabi, Koji

2010-04-01

To identify the most effective procedures to avoid increased intrahepatic pressure during radiofrequency ablation, we evaluated different ablation methods. Laparotomy was performed in 19 pigs. Intrahepatic pressure was monitored using an invasive blood pressure monitor. Radiofrequency ablation was performed as follows: single-step standard ablation; single-step at 30 W; single-step at 70 W; 4-step at 30 W; 8-step at 30 W; 8-step at 70 W; and cooled-tip. The array was fully deployed in single-step methods. In the multi-step methods, the array was gradually deployed in four or eight steps. With the cooled-tip, ablation was performed by increasing output by 10 W/min, starting at 40 W. Intrahepatic pressure was as follows: single-step standard ablation, 154.5 +/- 30.9 mmHg; single-step at 30 W, 34.2 +/- 20.0 mmHg; single-step at 70 W, 46.7 +/- 24.3 mmHg; 4-step at 30 W, 42.3 +/- 17.9 mmHg; 8-step at 30 W, 24.1 +/- 18.2 mmHg; 8-step at 70 W, 47.5 +/- 31.5 mmHg; and cooled-tip, 114.5 +/- 16.6 mmHg. The radiofrequency ablation-induced area was spherical with single-step standard ablation, 4-step at 30 W, and 8-step at 30 W. Conversely, the ablated area was irregular with single-step at 30 W, single-step at 70 W, and 8-step at 70 W. The ablation time was significantly shorter for the multi-step method than for the single-step method. Increased intrahepatic pressure could be controlled using multi-step methods. From the shapes of the ablation area, 30-W 8-step expansions appear to be most suitable for radiofrequency ablation.

Radiofrequency ablation versus cryoablation for atrioventricular nodal re-entrant tachycardia in children: a value comparison.

PubMed

Oster, Matthew E; Yang, Zhou; Stewart-Huey, Kay; Glanville, Michelle; Porter, Arlene; Campbell, Robert; Webb, Brad; Strieper, Margaret

2017-03-01

It is unclear whether cryoablation or radiofrequency ablation offers better value for treating atrioventricular nodal re-entrant tachycardia in children. We aimed to compare the value of these procedures for treating atrioventricular nodal re-entrant tachycardia in children, with value being outcomes relative to costs. We performed a retrospective cohort study of all atrioventricular nodal re-entrant tachycardia ablations for children (age⩽18 years) from July, 2009 to June, 2011 at our institution. Costs included fixed costs, miscellaneous hospital costs, and labour costs, and key outcomes were acute and long-term success (6 months) of the ablations. We conducted T-tests and regression analyses to investigate the associations between the ablation procedure type and the cost and success of the ablations. Of 96 unique cases performed by three paediatric electrophysiologists, 48 were cryoablation only, 42 radiofrequency ablation only, and six were a combination. Acute success was 100% for the cryoablation only and radiofrequency ablation only cases and 83% for the combination cases. There were no notable adverse events. The average total cost was $9636 for cryoablation cases, $9708 for radiofrequency ablation cases, and $10,967 for combination cases (p=0.51 for cryoablation only versus radiofrequency ablation only). The long-term success rate was 79.1% for cryoablation only, 92.8% for radiofrequency ablation only, and 66.7% for the combination (p=0.01 for cryoablation only versus radiofrequency ablation only), but long-term success varied notably by provider. Cryoablation and radiofrequency ablation offer similar value in the short term for the treatment of atrioventricular nodal re-entrant tachycardia in children. Differences in long-term success may vary substantially by physician, and thus may lead to differences in long-term value.

Novel Percutaneous Epicardial Autonomic Modulation in the Canine for Atrial Fibrillation: Results of an Efficacy and Safety Study

PubMed Central

Madhavan, Malini; Venkatachalam, K. L.; Swale, Matthew J.; DeSimone, Christopher V.; Gard, Joseph J.; Johnson, Susan B.; Suddendorf, Scott H.; Mikell, Susan B.; Ladewig, Dorothy J.; Nosbush, Toni Grabinger; Danielsen, Andrew J.; Knudson, Mark; Asirvatham, Samuel J.

2016-01-01

Background Endocardial ablation of atrial ganglionated plexi (GP) has been described for treatment of atrial fibrillation (AF). Our objective in this study was to develop percutaneous epicardial GP ablation in a canine model using novel energy sources and catheters. Methods Phase 1: The efficacy of several modalities to ablate the GP was tested in an open chest canine model (n=10). Phase 2: Percutaneous epicardial ablation of GP was done in 6 dogs using the most efficacious modality identified in phase 1 using 2 novel catheters. Results Phase 1: DC in varying doses [blocking (7 -12μA), electroporation (300-500μA), ablation (3000- 7500μA)], radiofrequency ablation (25–50 W), ultrasound (1.5MHz), and alcohol (2-5ml) injection were successful at 0/8, 4/12, 5/7, 3/8, 1/5 and 5/7 GP sites. DC (500–5000μA) along with alcohol irrigation was tested in phase 2. Phase 2: Percutaneous epicardial ablation of the right atrium, oblique sinus, vein of Marshall, and transverse sinus GP was successful in 5/6 dogs. One dog died of ventricular fibrillation (VF) during DC ablation at 5000 μA. Programmed stimulation induced AF in 6 dogs pre-ablation and no atrial arrhythmia in 3, flutter in 1 and AF in 1 post-ablation. Heart rate, blood pressure, effective atrial refractory period and local atrial electrogram amplitude did not change significantly post-ablation. Microscopic examination showed elimination of GP, and minimal injury to atrial myocardium. Conclusion Percutaneous epicardial ablation of GP using direct current and novel catheters is safe and feasible and may be used as an adjunct to pulmonary vein isolation in the treatment of atrial fibrillation in order to minimize additional atrial myocardial ablation. PMID:26854009

Early Efficacy Analysis of Biatrial Ablation versus Left and Simplified Right Atrial Ablation for Atrial Fibrillation Treatment in Patients with Rheumatic Heart Disease.

PubMed

Liu, Hong; Chen, Lin; Xiao, Yingbin; Ma, Ruiyan; Hao, Jia; Chen, Baicheng; Qin, Chuan; Cheng, Wei

2015-08-01

Atrial fibrillation (AF) is the most common sustained arrhythmia. About 60% of patients with rheumatic heart disease have persistent AF. A total of 197 patients underwent valve replacement concomitant bipolar radiofrequency ablation (BRFA). Patients were divided into the biatrial ablation group and the simplified right atrial ablation group. In biatrial ablation group, the patients underwent a complete left and right atrial ablation. In simplified right atrial ablation group, the patients underwent a complete left atrial ablation and a simplified right atrial ablation. The conversion of sinus rhythm (SR) was high in both groups during the follow-up period. In the simplified right atrial ablation group, SR conversion rate was 88.29% at discharge. At six months and 12 months after surgery, 87.39% of patients and 86.49% of patients were in SR free of antiarrhythmic drugs, respectively. While in the biatrial ablation group, SA conversion rate was 89.53% at discharge. Percentage of patients in SR free of antiarrhythmic drugs was 88.37% and 88.37% at six months and 12 months after surgery, respectively. Echocardiography showed left atrial diameter decreased significantly after the surgery in the two groups. The ejection fraction and fractional shortening were improved significantly, without significant differences between the two groups. The results suggest that the concomitant left atrial and simplified right atrial BRFA for AF in patients undergoing valve replacement can achieve similar early efficiency as biatrial ablation. Copyright © 2015 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction.

PubMed

Verma, Shwetabh; Hesser, Juergen; Arba-Mosquera, Samuel

2017-04-01

Controversial opinions exist regarding optimum laser beam characteristics for achieving smoother ablations in laser-based vision correction. The purpose of the study was to outline a rigorous simulation model for simulating shot-by-shot ablation process. The impact of laser beam characteristics like super Gaussian order, truncation radius, spot geometry, spot overlap, and lattice geometry were tested on ablation smoothness. Given the super Gaussian order, the theoretical beam profile was determined following Lambert-Beer model. The intensity beam profile originating from an excimer laser was measured with a beam profiler camera. For both, the measured and theoretical beam profiles, two spot geometries (round and square spots) were considered, and two types of lattices (reticular and triangular) were simulated with varying spot overlaps and ablated material (cornea or polymethylmethacrylate [PMMA]). The roughness in ablation was determined by the root-mean-square per square root of layer depth. Truncating the beam profile increases the roughness in ablation, Gaussian profiles theoretically result in smoother ablations, round spot geometries produce lower roughness in ablation compared to square geometry, triangular lattices theoretically produce lower roughness in ablation compared to the reticular lattice, theoretically modeled beam profiles show lower roughness in ablation compared to the measured beam profile, and the simulated roughness in ablation on PMMA tends to be lower than on human cornea. For given input parameters, proper optimum parameters for minimizing the roughness have been found. Theoretically, the proposed model can be used for achieving smoothness with laser systems used for ablation processes at relatively low cost. This model may improve the quality of results and could be directly applied for improving postoperative surface quality.

Left Septal Slow Pathway Ablation for Atrioventricular Nodal Reentrant Tachycardia.

PubMed

Katritsis, Demosthenes G; John, Roy M; Latchamsetty, Rakesh; Muthalaly, Rahul G; Zografos, Theodoros; Katritsis, George D; Stevenson, William G; Efimov, Igor R; Morady, Fred

2018-03-01

Immunohistochemistry studies suggest that the anatomic substrate of the slow pathway in atrioventricular nodal reentrant tachycardia (AVNRT) is the left inferior nodal extension. We hypothesized that slow pathway ablation from the left septum is an effective alternative to right-sided ablation. We analyzed our databases of AVNRT in search of cases that had used slow pathway ablation from the left septum because of failure of right septal ablation, and then prospectively subjected consenting patients to a left septal-only procedure. Of 1342 patients subjected to right septal slow pathway ablation for AVNRT, 15 patients, 11 with typical and 4 with atypical AVNRT, had a left septal approach after unsuccessful right-sided ablation (R+L group). Eleven patients were subjected to a left septal-only approach for slow pathway ablation without a previous right septal attempt (L group). Fluoroscopy times in the R+L and L groups were 30.5 (21.0-44.0) and 20.0 (17.0-25.0) minutes, respectively ( P =0.061), and radiofrequency current delivery times were 11.3 (5.0-19.1) and 10.0 (7.0-12.0) minutes, respectively ( P =0.897). There was no need for additional ablation lesions at other anatomic sites in either group, and no cases of atrioventricular block were encountered. Recurrence rates of the arrhythmia for the R+L and L groups were 6.7% and 0%, respectively, in the 3 months after ablation ( P =1.000). Left septal ablation at the anatomic site of the left inferior nodal extension is an alternative for ablation of both typical and atypical AVNRT when ablation at the right posterior septum is ineffective. © 2018 American Heart Association, Inc.

Nanosecond laser-metal ablation at different ambient conditions

NASA Astrophysics Data System (ADS)

Elsied, Ahmed M.; Dieffenbach, Payson C.; Diwakar, Prasoon K.; Hassanein, Ahmed

2018-05-01

Ablation of metals under different ambient conditions and laser fluences, was investigated through series of experiments. A 1064 nm, 6 ns Nd:YAG laser was used to ablate 1 mm thick metal targets with laser energy ranging from 2 mJ to 300 mJ. The experiments were designed to study the effect of material properties, laser fluence, ambient gas, and ambient pressure on laser-metal ablation. The first experiment was conducted under vacuum to study the effect of laser fluence and material properties on metal ablation, using a wide range of laser fluences (2 J/cm2 up to 300 J/cm2) and two different targets, Al and W. The second experiment was conducted at atmospheric pressure using two different ambient gases air and argon, to understand the effect of ambient gas on laser-metal ablation process. The third experiment was conducted at two different pressures (10 Torr and 760 Torr) using the same ambient gas to investigate the effect of ambient pressure on laser-metal ablation. To compare the different ablation processes, the amount of mass ablated, ablation depth, crater profile and melt formation were measured using White Light Profilometer (WLP). The experimental results show that at low laser fluence: the ablated mass, ablation depth, and height of molten layer follow a logarithmic function of the incident laser fluence. While, at high laser fluence they follow a linear function. This dependence on laser fluence was found to be independent on ambient conditions and irradiated material. The effect of ambient pressure was more pronounced than the effect of ambient gas type. Plasma shielding effect was found to be very pronounced in the presence of ambient gas and led to significant reduction in the total mass ablation.

Ablative Thermal Protection System Fundamentals

NASA Technical Reports Server (NTRS)

Beck, Robin A. S.

2013-01-01

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

Aluminum X-ray mass-ablation rate measurements

DOE PAGES

Kline, John L.; Hager, Jonathan D.

2016-10-15

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

[The application of Atricure bipolar radiofrequency system in ablation of different parts and different times of pig heart atrium and the analysis of transmural lesions].

PubMed

Liu, Pei-sheng; Chen, Xin; Liu, Ming

2010-12-15

To analyze the transmural lesions of different parts of the pig heart atrium received different times of ablation applied with Atricure bipolar radiofrequency system. Six fresh (ex vivo time<20 min) pig hearts with atrium preserved intact were used as the experimental objects and experimental groups were divided according to the ablation position. The Atricure bipolar radiofrequency system was applied in the ablation of the parts of the atrium, such as posterior wall of left atrium, anterior wall of left atrium, anterior wall of right atrium and posterior wall of left atrium close to mitral posterior ring. Ablate the position of the atrium lengthened about 2.0 cm with the same thickness with an interval of 0.5 cm for 4 times respectively, also recording the time of every ablation. For each part and each time of ablation, the ablated atrial tissue was preserved with 4% formaldehyde and 5% glutaraldehyde, and was sent for observation under light microscope and transmission electron microscope. The ablation time and lesion were analyzed statistically. In the same position of the atrium, ablation time decreased with the times of the ablation, in different position of the atrium with same time of ablation, time showed a positive proportion with the thickness of the atrium. Atricure bipolar radiofrequency system is very safe and efficient, also convenient for manipulation. With regard to the relatively thinner part of the atrium, such as posterior wall and anterior wall of left atrium, at least two times of ablation can ensure transmural lesion of the atrial tissue, but to the position of the atrium such as anterior wall of right atrium and posterior wall of left atrium close to mitral posterior ring, 3 to 4 times of ablation can ensure transmural lesion of the atrial tissue.

Voltage and pace-capture mapping of linear ablation lesions overestimates chronic ablation gap size.

PubMed

O'Neill, Louisa; Harrison, James; Chubb, Henry; Whitaker, John; Mukherjee, Rahul K; Bloch, Lars Ølgaard; Andersen, Niels Peter; Dam, Høgni; Jensen, Henrik K; Niederer, Steven; Wright, Matthew; O'Neill, Mark; Williams, Steven E

2018-04-26

Conducting gaps in lesion sets are a major reason for failure of ablation procedures. Voltage mapping and pace-capture have been proposed for intra-procedural identification of gaps. We aimed to compare gap size measured acutely and chronically post-ablation to macroscopic gap size in a porcine model. Intercaval linear ablation was performed in eight Göttingen minipigs with a deliberate gap of ∼5 mm left in the ablation line. Gap size was measured by interpolating ablation contact force values between ablation tags and thresholding at a low force cut-off of 5 g. Bipolar voltage mapping and pace-capture mapping along the length of the line were performed immediately, and at 2 months, post-ablation. Animals were euthanized and gap sizes were measured macroscopically. Voltage thresholds to define scar were determined by receiver operating characteristic analysis as <0.56 mV (acutely) and <0.62 mV (chronically). Taking the macroscopic gap size as gold standard, error in gap measurements were determined for voltage, pace-capture, and ablation contact force maps. All modalities overestimated chronic gap size, by 1.4 ± 2.0 mm (ablation contact force map), 5.1 ± 3.4 mm (pace-capture), and 9.5 ± 3.8 mm (voltage mapping). Error on ablation contact force map gap measurements were significantly less than for voltage mapping (P = 0.003, Tukey's multiple comparisons test). Chronically, voltage mapping and pace-capture mapping overestimated macroscopic gap size by 11.9 ± 3.7 and 9.8 ± 3.5 mm, respectively. Bipolar voltage and pace-capture mapping overestimate the size of chronic gap formation in linear ablation lesions. The most accurate estimation of chronic gap size was achieved by analysis of catheter-myocardium contact force during ablation.

Noninvasive microwave ablation zone radii estimation using x-ray CT image analysis.

PubMed

Weiss, Noam; Goldberg, S Nahum; Nissenbaum, Yitzhak; Sosna, Jacob; Azhari, Haim

2016-08-01

The aims of this study were to noninvasively and automatically estimate both the radius of the ablated liver tissue and the radius encircling the treated zone, which also defines where the tissue is definitely untreated during a microwave (MW) thermal ablation procedure. Fourteen ex vivo bovine fresh liver specimens were ablated at 40 W using a 14 G microwave antenna, for durations of 3, 6, 8, and 10 min. The tissues were scanned every 5 s during the ablation using an x-ray CT scanner. In order to estimate the radius of the ablation zone, the acquired images were transformed into a polar presentation by displaying the Hounsfield units (HU) as a function of angle and radius. From this polar presentation, the average HU radial profile was analyzed at each time point and the ablation zone radius was estimated. In addition, textural analysis was applied to the original CT images. The proposed algorithm identified high entropy regions and estimated the treated zone radius per time. The estimated ablated zone radii as a function of treatment durations were compared, by means of correlation coefficient and root mean square error (RMSE) to gross pathology measurements taken immediately post-treatment from similarly ablated tissue. Both the estimated ablation radii and the treated zone radii demonstrated strong correlation with the measured gross pathology values (R(2) ≥ 0.89 and R(2) ≥ 0.86, respectively). The automated ablation radii estimation had an average discrepancy of less than 1 mm (RMSE = 0.65 mm) from the gross pathology measured values, while the treated zone radii showed a slight overestimation of approximately 1.5 mm (RMSE = 1.6 mm). Noninvasive monitoring of MW ablation using x-ray CT and image analysis is feasible. Automatic estimations of the ablation zone radius and the radius encompassing the treated zone that highly correlate with actual ablation measured values can be obtained. This technique can therefore potentially be used to obtain real time monitoring and improve the clinical outcome.

A randomized prospective long-term (>1 year) clinical trial comparing the efficacy and safety of radiofrequency ablation to 980 nm laser ablation of the great saphenous vein.

PubMed

Sydnor, Malcolm; Mavropoulos, John; Slobodnik, Natalia; Wolfe, Luke; Strife, Brian; Komorowski, Daniel

2017-07-01

Purpose To compare the short- and long-term (>1 year) efficacy and safety of radiofrequency ablation (ClosureFAST™) versus endovenous laser ablation (980 nm diode laser) for the treatment of superficial venous insufficiency of the great saphenous vein. Materials and methods Two hundred patients with superficial venous insufficiency of the great saphenous vein were randomized to receive either radiofrequency ablation or endovenous laser ablation (and simultaneous adjunctive therapies for surface varicosities when appropriate). Post-treatment sonographic and clinical assessment was conducted at one week, six weeks, and six months for closure, complications, and patient satisfaction. Clinical assessment of each patient was conducted at one year and then at yearly intervals for patient satisfaction. Results Post-procedure pain ( p < 0.0001) and objective post-procedure bruising ( p = 0.0114) were significantly lower in the radiofrequency ablation group. Improvements in venous clinical severity score were noted through six months in both groups (endovenous laser ablation 6.6 to 1; radiofrequency ablation 6.2 to 1) with no significant difference in venous clinical severity score ( p = 0.4066) or measured adverse effects; 89 endovenous laser ablation and 87 radiofrequency patients were interviewed at least 12 months out with a mean long-term follow-up of 44 and 42 months ( p = 0.1096), respectively. There were four treatment failures in each group, and every case was correctable with further treatment. Overall, there were no significant differences with regard to patient satisfaction between radiofrequency ablation and endovenous laser ablation ( p = 0.3009). There were no cases of deep venous thrombosis in either group at any time during this study. Conclusions Radiofrequency ablation and endovenous laser ablation are highly effective and safe from both anatomic and clinical standpoints over a multi-year period and neither modality achieved superiority over the other.

Direct quantitative comparison of molecular responses in photodamaged human skin to fractionated and fully ablative carbon dioxide laser resurfacing.

PubMed

Orringer, Jeffrey S; Sachs, Dana L; Shao, Yuan; Hammerberg, Craig; Cui, Yilei; Voorhees, John J; Fisher, Gary J

2012-10-01

Fractionated ablative laser resurfacing has become a widely used treatment modality. Its clinical results are often found to approach those of traditional fully ablative laser resurfacing. To directly compare the molecular changes that result from fractionated and fully ablative carbon dioxide (CO(2)) laser resurfacing in photodamaged human skin. Photodamaged skin of 34 adult volunteers was focally treated at distinct sites with a fully ablative CO(2) laser and a fractionated CO(2) laser. Serial skin samples were obtained at baseline and several time points after treatment. Real-time reverse transcriptase polymerase chain reaction technology and immunohistochemistry were used to quantify molecular responses to each type of laser treatment. Fully ablative and fractionated CO(2) laser resurfacing induced significant dermal remodeling and collagen induction. After a single treatment, fractionated ablative laser resurfacing resulted in collagen induction that was approximately 40% to 50% as pronounced as that induced by fully ablative laser resurfacing. The fundamental cutaneous responses that result from fully ablative and fractionated carbon dioxide laser resurfacing are similar but differ in magnitude and duration, with the fully ablative procedure inducing relatively greater changes including more pronounced collagen induction. However, the molecular data reported here provide substantial support for fractionated ablative resurfacing as an effective treatment modality for improving skin texture. © 2012 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.

Bipolar radiofrequency ablation of spinal tumors: predictability, safety and outcome.

PubMed

Gazis, Angelos N; Beuing, Oliver; Franke, Jörg; Jöllenbeck, Boris; Skalej, Martin

2014-04-01

Bone metastases are often the cause of tumor-associated pain and reduction of quality of life. For patients that cannot be treated by surgery, a local minimally invasive therapy such as radiofrequency ablation can be a useful option. In cases in which tumorous masses are adjacent to vulnerable structures, the monopolar radiofrequency can cause severe neuronal damage because of the unpredictability of current flow. The aim of this study is to show that the bipolar radiofrequency ablation provides an opportunity to safely treat such spinal lesions because of precise predictability of the emerging ablation zone. Prospective cohort study of 36 patients undergoing treatment at a single institution. Thirty-six patients in advanced tumor stage with primary or secondary tumor involvement of spine undergoing radiofrequency ablation. Prediction of emerging ablation zone. Clinical outcome of treated patients. X-ray-controlled treatment of 39 lesions by bipolar radiofrequency ablation. Magnetic resonance imaging was performed pre- and postinterventionally. Patients were observed clinically during their postinterventional stay. The extent of the ablation zones was predictable to the millimeter because it did not cross the peri-interventional planned dorsal and ventral boundaries in any case. No complications were observed. Ablation of tumorous masses adjacent to vulnerable structures is feasible and predictable by using the bipolar radiofrequency ablation. Damage of neuronal structures can be avoided through precise prediction of the ablation area. Copyright © 2014 Elsevier Inc. All rights reserved.

Atrial Tachycardias Following Atrial Fibrillation Ablation

PubMed Central

Sághy, László; Tutuianu, Cristina; Szilágyi, Judith

2015-01-01

One of the most important proarrhythmic complications after left atrial (LA) ablation is regular atrial tachycardia (AT) or flutter. Those tachycardias that occur after atrial fibrillation (AF) ablation can cause even more severe symptoms than those from the original arrhythmia prior to the index ablation procedure since they are often incessant and associated with rapid ventricular response. Depending on the method and extent of LA ablation and on the electrophysiological properties of underlying LA substrate, the reported incidence of late ATs is variable. To establish the exact mechanism of these tachycardias can be difficult and controversial but correlates with the ablation technique and in the vast majority of cases the mechanism is reentry related to gaps in prior ablation lines. When tachycardias occur, conservative therapy usually is not effective, radiofrequency ablation procedure is mostly successful, but can be challenging, and requires a complex approach. PMID:25308808

The role of rotors in atrial fibrillation

PubMed Central

Swarup, Vijay; Narayan, Sanjiv M.

2015-01-01

Despite significant advances in our understanding of atrial fibrillation (AF) mechanisms in the last 15 years, ablation outcomes remain suboptimal. A potential reason is that many ablation techniques focus on anatomic, rather than patient-specific functional targets for ablation. Panoramic contact mapping, incorporating phase analysis, repolarization and conduction dynamics, and oscillations in AF rate, overcomes many prior difficulties with mapping AF. This approach provides evidence that the mechanisms sustaining human AF are deterministic, largely due to stable electrical rotors and focal sources in either atrium. Ablation of such sources (Focal Impulse and Rotor Modulation: FIRM ablation) has been shown to improve ablation outcome compared with conventional ablation alone; independent laboratories directly targeting stable rotors have shown similar results. Clinical trials examining the role of stand-alone FIRM ablation are in progress. Looking forward, translating insights from patient-specific mapping to evidence-based guidelines and clinical practice is the next challenge in improving patient outcomes in AF management. PMID:25713729

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

NASA Technical Reports Server (NTRS)

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

2005-01-01

Production of single-walled carbon nanotubes (SWNT) has taken place for a number of years and by a variety of methods such as laser ablation, chemical vapor deposition, and arc-jet ablation. Yet, little is actually understood about the exact chemical kinetics and processes that occur in SWNT formation. In recent time, NASA Johnson Space Center has devoted a considerable effort to the experimental evaluation of the laser ablation production process for SWNT originally developed at Rice University. To fully understand the nature of the laser ablation process it is necessary to understand the development of the carbon plume dynamics within the laser ablation oven. The present work is a continuation of previous studies into the efforts to model plume dynamics using computational fluid dynamics (CFD). The ultimate goal of the work is to improve understanding of the laser ablation process, and through that improved understanding, refine the laser ablation production of SWNT.

Effects of pressure rise on cw laser ablation of tissue

NASA Astrophysics Data System (ADS)

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

1991-06-01

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

Is AF Ablation Cost Effective?

PubMed Central

Martin-Doyle, William; Reynolds, Matthew R.

2010-01-01

The use of catheter ablation to treat AF is increasing rapidly, but there is presently an incomplete understanding of its cost-effectiveness. AF ablation procedures involve significant up-front expenditures, but multiple randomized trials have demonstrated that ablation is more effective than antiarrhythmic drugs at maintaining sinus rhythm in a second-line and possibly first-line rhythm control setting. Although truly long-term data are limited, ablation, as compared with antiarrrhythmic drugs, also appears associated with improved symptoms and quality of life and a reduction in downstream hospitalization and other health care resource utilization. Several groups have developed cost effectiveness models comparing AF ablation primarily to antiarrhythmic drugs and the model results suggest that ablation likely falls within the range generally accepted as cost-effective in developed nations. This paper will review available information on the cost-effectiveness of catheter ablation for the treatment of atrial fibrillation, and discuss continued areas of uncertainty where further research is required. PMID:20936083

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

PubMed Central

Prakash, Punit; Diederich, Chris J.

2012-01-01

Purpose To determine the impact of including dynamic changes in tissue physical properties during heating on feedback controlled thermal ablation with catheter-based ultrasound. Additionally, we compared impact several indicators of thermal damage on predicted extents of ablation zones for planning and monitoring ablations with this modality. Methods A 3D model of ultrasound ablation with interstitial and transurethral applicators incorporating temperature based feedback control was used to simulate thermal ablations in prostate and liver tissue. We investigated five coupled models of heat dependent changes in tissue acoustic attenuation/absorption and blood perfusion of varying degrees of complexity.. Dimensions of the ablation zone were computed using temperature, thermal dose, and Arrhenius thermal damage indicators of coagulative necrosis. A comparison of the predictions by each of these models was illustrated on a patient-specific anatomy in the treatment planning setting. Results Models including dynamic changes in blood perfusion and acoustic attenuation as a function of thermal dose/damage predicted near-identical ablation zone volumes (maximum variation < 2.5%). Accounting for dynamic acoustic attenuation appeared to play a critical role in estimating ablation zone size, as models using constant values for acoustic attenuation predicted ablation zone volumes up to 50% larger or 47% smaller in liver and prostate tissue, respectively. Thermal dose (t43 ≥ 240min) and thermal damage (Ω ≥ 4.6) thresholds for coagulative necrosis are in good agreement for all heating durations, temperature thresholds in the range of 54 °C for short (< 5 min) duration ablations and 50 °C for long (15 min) ablations may serve as surrogates for determination of the outer treatment boundary. Conclusions Accounting for dynamic changes in acoustic attenuation/absorption appeared to play a critical role in predicted extents of ablation zones. For typical 5—15 min ablations with this modality, thermal dose and Arrhenius damage measures of ablation zone dimensions are in good agreement, while appropriately selected temperature thresholds provide a computationally cheaper surrogate. PMID:22235787

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

PubMed

Zhou, Wenhui; Arellano, Ronald S

2018-04-06

To evaluate perioperative outcomes of thermal ablation with microwave (MW), radiofrequency (RF), and cryoablation for stage T1c renal cell carcinoma (RCC). A retrospective analysis of 384 patients (mean age, 71 y; range, 22-88 y) was performed between October 2006 and October 2016. Mean radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, and location relative to polar lines; preoperative aspects and dimensions used for anatomic classification; and centrality index scores were 6.3, 7.9, and 2.7, respectively. Assessment of pre- and postablation serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate was performed to assess functional outcomes. Linear regression analyses were performed to compare sedation medication dosages among the three treatment cohorts. Univariable and multivariable logistic regression analyses were performed to compare rates of residual disease and complications among treatment modalities. A total of 437 clinical stage T1N0M0 biopsy-proven RCCs measuring 1.2-6.9 cm were treated with computed tomography (CT)-guided MW ablation (n = 44; 10%), RF ablation (n = 347; 79%), or cryoablation (n = 46; 11%). There were no significant differences in patient demographic or tumor characteristics among cohorts. Complication rates and immediate renal function changes were similar among the three ablation modalities (P = .46 and P = .08, respectively). MW ablation was associated with significantly decreased ablation time (P < .05), procedural time (P < .05), and dosage of sedative medication (P < .05) compared with RF ablation and cryoablation. CT-guided percutaneous MW ablation is comparable to RF ablation or cryoablation for the treatment of stage T1N0M0 RCC with regard to treatment response and is associated with shorter treatment times and less sedation than RF ablation or cryoablation. In addition, the safety profile of CT-guided MW ablation is noninferior to those of RF ablation or cryoablation. Copyright © 2017 SIR. Published by Elsevier Inc. All rights reserved.

Epicardial Radiofrequency Ablation Failure During Ablation Procedures for Ventricular Arrhythmias: Reasons and Implications for Outcomes.

PubMed

Baldinger, Samuel H; Kumar, Saurabh; Barbhaiya, Chirag R; Mahida, Saagar; Epstein, Laurence M; Michaud, Gregory F; John, Roy; Tedrow, Usha B; Stevenson, William G

2015-12-01

Radiofrequency ablation (RFA) from the epicardial space for ventricular arrhythmias is limited or impossible in some cases. Reasons for epicardial ablation failure and the effect on outcome have not been systematically analyzed. We assessed reasons for epicardial RFA failure relative to the anatomic target area and the type of heart disease and assessed the effect of failed epicardial RFA on outcome after ablation procedures for ventricular arrhythmias in a large single-center cohort. Epicardial access was attempted during 309 ablation procedures in 277 patients and was achieved in 291 procedures (94%). Unlimited ablation in an identified target region could be performed in 181 cases (59%), limited ablation was possible in 22 cases (7%), and epicardial ablation was deemed not feasible in 88 cases (28%). Reasons for failed or limited ablation were unsuccessful epicardial access (6%), failure to identify an epicardial target (15%), proximity to a coronary artery (13%), proximity to the phrenic nerve (6%), and complications (<1%). Epicardial RFA was impeded in the majority of cases targeting the left ventricular summit region. Acute complications occurred in 9%. The risk for acute ablation failure was 8.3× higher (4.5-15.0; P<0.001) after no or limited epicardial RFA compared with unlimited RFA, and patients with unlimited epicardial RFA had better recurrence-free survival rates (P<0.001). Epicardial RFA for ventricular arrhythmias is often limited even when pericardial access is successful. Variability of success is dependent on the target area, and the presence of factors limiting ablation is associated with worse outcomes. © 2015 American Heart Association, Inc.

An approach to ablate and pace:AV junction ablation and pacemaker implantation performed concurrently from the same venous access site.

PubMed

Issa, Ziad F

2007-09-01

Atrioventricular junction (AVJ) ablation combined with permanent pacemaker implantation (the "ablate and pace" approach) remains an acceptable alternative treatment strategy for symptomatic, drug-refractory atrial fibrillation (AF) with rapid ventricular response. This case series describes the feasibility and safety of catheter ablation of the AVJ via a superior vena caval approach performed during concurrent dual-chamber pacemaker implantation. A total of 17 consecutive patients with symptomatic, drug-refractory, paroxysmal AF underwent combined AVJ ablation and dual-chamber pacemaker implantation procedure using a left axillary venous approach. Two separate introducer sheaths were placed into the axillary vein. The first sheath was used for implantation of the pacemaker ventricular lead, which was then connected to the pulse generator. Subsequently, a standard ablation catheter was introduced through the second axillary venous sheath and used for radiofrequency (RF) ablation of the AVJ. After successful ablation, the catheter was withdrawn and the pacemaker atrial lead was advanced through that same sheath and implanted in the right atrium. Catheter ablation of the AVJ was successfully achieved in all patients. The median number of RF applications required to achieve complete AV block was three (range 1-10). In one patient, AV conduction recovered within the first hour after completion of the procedure, and AVJ ablation was then performed using the conventional femoral venous approach. There were no procedural complications. Catheter ablation of the AVJ can be performed successfully and safely via a superior vena caval approach in patients undergoing concurrent dual-chamber pacemaker implantation.

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

NASA Astrophysics Data System (ADS)

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.

Slow Pathway Radiofrequency Ablation Using Magnetic Navigation: A Description of Technique and Retrospective Case Analysis.

PubMed

Bhaskaran, Abhishek; Albarri, Maha; Ross, Neil; Al Raisi, Sara; Samanta, Rahul; Roode, Leonette; Nadri, Fazlur; Ng, Jeanette; Thomas, Stuart; Thiagalingam, Aravinda; Kovoor, Pramesh

2017-12-01

The Magnetic Navigation System (MNS) catheter was shown to be stable in the presence of significant cardiac wall motion and delivered more effective lesions compared to manual control. This stability could potentially make AV junctional re-entrant tachycardia (AVNRT) ablation safer. The aim of this study is to describe the method of mapping and ablation of AVNRT with MNS and 3-D electro-anatomical mapping system (CARTO, Biosense Webster, Diamond bar, CA, USA) anatomical mapping, with a view to improve the safety of ablation. The method of precise mapping and ablation with MNS is described. Consecutive AVNRT cases (n=30) from 2012 January to 2015 November, in which magnetic navigation was used, are analysed. Ablation was successful in 27 (90%) out of 30 patients. In three cases, ablation was abandoned due to the proximity of the three-dimensional His image to the potential ablation site. No complications, including AV nodal injury, occurred. The distance from the nearest His position to successful ablation site in both LAO and RAO projections of CARTO images was 26.4±8.8 and 27±7.7mm respectively. Only in two (9%) patients, ablation needed to be extended superior to the plane of coronary sinus ostium, towards the His bundle region, to achieve slow pathway modification. AVNRT ablation with MNS allows for accurate mapping of the AV node and stable ablation at a safe distance, which could help avoid AV nodal injury. We recommend this modality for younger patients with AVNRT. Copyright © 2017. Published by Elsevier B.V.

Bipolar radiofrequency ablation with 2 × 2 electrodes as a building block for matrix radiofrequency ablation: Ex vivo liver experiments and finite element method modelling.

PubMed

Mulier, Stefaan; Jiang, Yansheng; Jamart, Jacques; Wang, Chong; Feng, Yuanbo; Marchal, Guy; Michel, Luc; Ni, Yicheng

2015-01-01

Size and geometry of the ablation zone obtained by currently available radiofrequency (RF) electrodes is highly variable. Reliability might be improved by matrix radiofrequency ablation (MRFA), in which the whole tumour volume is contained within a cage of x × y parallel electrodes. The aim of this study was to optimise the smallest building block for matrix radiofrequency ablation: a recently developed bipolar 2 × 2 electrode system. In ex vivo bovine liver, the parameters of the experimental set-up were changed one by one. In a second step, a finite element method (FEM) modelling of the experiment was performed to better understand the experimental findings. The optimal power to obtain complete ablation in the shortest time was 50-60 W. Performing an ablation until impedance rise was superior to ablation for a fixed duration. Increasing electrode diameter improved completeness of ablation due to lower temperature along the electrodes. A chessboard pattern of electrode polarity was inferior to a row pattern due to an electric field void in between the electrodes. Variability of ablation size was limited. The FEM correctly simulated and explained the findings in ex vivo liver. These experiments and FEM modelling allowed a better insight in the factors influencing the ablation zone in a bipolar 2 × 2 electrode RF system. With optimal parameters, complete ablation was obtained quickly and with limited variability. This knowledge will be useful to build a larger system with x × y electrodes for MRFA.

Outcomes after cryoablation vs. radiofrequency in patients with paroxysmal atrial fibrillation: impact of pulmonary veins anatomy.

PubMed

Khoueiry, Z; Albenque, J-P; Providencia, R; Combes, S; Combes, N; Jourda, F; Sousa, P A; Cardin, C; Pasquie, J-L; Cung, T T; Massin, F; Marijon, E; Boveda, S

2016-09-01

Pulmonary vein isolation is the mainstay of treatment in catheter ablation of paroxysmal atrial fibrillation (AF). Cryoballoon ablation has been introduced more recently than radiofrequency ablation, the standard technique in most centres. Pulmonary veins frequently display anatomical variants, which may compromise the results of cryoballoon ablation. We aimed to evaluate the mid-term outcomes of cryoballoon ablation in an unselected population with paroxysmal AF from an anatomical viewpoint. Consecutive patients with paroxysmal AF who underwent a first procedure of cryoballoon ablation or radiofrequency were enrolled in this single-centre study. All patients underwent systematic standardized follow-up. Comparisons between radiofrequency and cryoballoon ablation (Arctic Front™ or Arctic Front Advance™) were performed regarding safety and efficacy endpoints, according to pulmonary vein (PV) anatomical variants. A total of 687 patients were enrolled (376 radiofrequency and 311 cryoballoon ablation). Baseline characteristics and distribution of PV anatomical variants were generally similar in the groups. After a mean follow-up of 14 ± 8 months, there was no difference in the incidence of relapse (17.0% cryoballoon ablation vs. 14.1% radiofrequency, P = 0.25). We observed no interaction of PV anatomical variants on mid-term procedural success. Our findings suggest that mid-term outcomes of cryoballoon ablation for paroxysmal AF ablation are similar to those of radiofrequency, regardless of PV anatomy. The presence of anatomical variants of PVs should not discourage the referral of patients with paroxysmal AF for cryoballoon ablation. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

A multimodality imaging-compatible insertion robot with a respiratory motion calibration module designed for ablation of liver tumors: a preclinical study.

PubMed

Li, Dongrui; Cheng, Zhigang; Chen, Gang; Liu, Fangyi; Wu, Wenbo; Yu, Jie; Gu, Ying; Liu, Fengyong; Ren, Chao; Liang, Ping

2018-04-03

To test the accuracy and efficacy of the multimodality imaging-compatible insertion robot with a respiratory motion calibration module designed for ablation of liver tumors in phantom and animal models. To evaluate and compare the influences of intervention experience on robot-assisted and ultrasound-controlled ablation procedures. Accuracy tests on rigid body/phantom model with a respiratory movement simulation device and microwave ablation tests on porcine liver tumor/rabbit liver cancer were performed with the robot we designed or with the traditional ultrasound-guidance by physicians with or without intervention experience. In the accuracy tests performed by the physicians without intervention experience, the insertion accuracy and efficiency of robot-assisted group was higher than those of ultrasound-guided group with statistically significant differences. In the microwave ablation tests performed by the physicians without intervention experience, better complete ablation rate was achieved when applying the robot. In the microwave ablation tests performed by the physicians with intervention experience, there was no statistically significant difference of the insertion number and total ablation time between the robot-assisted group and the ultrasound-controlled group. The evaluation by the NASA-TLX suggested that the robot-assisted insertion and microwave ablation process performed by physicians with or without experience were more comfortable. The multimodality imaging-compatible insertion robot with a respiratory motion calibration module designed for ablation of liver tumors could increase the insertion accuracy and ablation efficacy, and minimize the influence of the physicians' experience. The ablation procedure could be more comfortable with less stress with the application of the robot.

OCDR guided laser ablation device

DOEpatents

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

2002-01-01

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

Multiple-electrode radiofrequency ablation: simultaneous production of separate zones of coagulation in an in vivo porcine liver model.

PubMed

Laeseke, Paul F; Sampson, Lisa A; Haemmerich, Dieter; Brace, Chris L; Fine, Jason P; Frey, Tina M; Winter, Thomas C; Lee, Fred T

2005-12-01

A multiple-electrode radiofrequency (RF) system was developed based on switching between electrodes that allows for the simultaneous use of as many as three electrically independent electrodes. The purpose of this study was to determine if each multiple-electrode ablation zone is identical to an ablation zone created with conventional single-electrode mode. Nine female domestic pigs (mean weight, 90 kg) were used for this study. A prototype monopolar multiple-electrode RF ablation system was created with use of an RF generator and an electronic switching algorithm. A maximum of three electrodes can be used simultaneously by switching between electrodes at each impedance spike (30 omega greater than baseline levels). A total of 39 zones of ablation were created at open laparotomy in pig livers with use of a conventional single electrode (n = 9), two single electrodes simultaneously (n = 6 ablations; 12 ablation zones), or three single electrodes simultaneously (n = 6 ablations; 18 ablation zones). RF electrodes were spaced in separate lobes of the liver when multiple zones of coagulation were created simultaneously. Animals were euthanized after RF ablation, livers were removed, and ablation zones were sectioned and measured. Zones of coagulation created simultaneously with two or three electrodes were equivalent to ablation zones created with use of conventional single-electrode ablation. No significant differences were observed among control animals treated with a single electrode, those with two separate zones of ablation created simultaneously, and those with three simultaneously created ablation zones in terms of mean (+/-SD) minimum diameter (1.6 cm +/- 0.6, 1.6 cm +/- 0.5, and 1.7 cm +/- 0.4, respectively), maximum diameter (2.0 cm +/- 0.5, 2.3 cm +/- 0.5, 2.2 cm +/- 0.5, respectively), and volume (6.7 cm3 +/- 3.7, 7.4 cm3 +/- 3.8, and 7.8 cm3 +/- 3.9; P > .30, analysis of variance, pairwise t-test comparisons). A rapid-switching multiple-electrode RF system was able to simultaneously create as many as three separate ablation zones of equivalent size compared with single-electrode controls. This system would allow physicians to simultaneously treat multiple tumors, substantially reducing procedure time and anesthesia risk.

Active contour configuration model for estimating the posterior ablative margin in image fusion of real-time ultrasound and 3D ultrasound or magnetic resonance images for radiofrequency ablation: an experimental study.

PubMed

Lee, Junkyo; Lee, Min Woo; Choi, Dongil; Cha, Dong Ik; Lee, Sunyoung; Kang, Tae Wook; Yang, Jehoon; Jo, Jaemoon; Bang, Won-Chul; Kim, Jongsik; Shin, Dongkuk

2017-12-21

The purpose of this study was to evaluate the accuracy of an active contour model for estimating the posterior ablative margin in images obtained by the fusion of real-time ultrasonography (US) and 3-dimensional (3D) US or magnetic resonance (MR) images of an experimental tumor model for radiofrequency ablation. Chickpeas (n=12) and bovine rump meat (n=12) were used as an experimental tumor model. Grayscale 3D US and T1-weighted MR images were pre-acquired for use as reference datasets. US and MR/3D US fusion was performed for one group (n=4), and US and 3D US fusion only (n=8) was performed for the other group. Half of the models in each group were completely ablated, while the other half were incompletely ablated. Hyperechoic ablation areas were extracted using an active contour model from real-time US images, and the posterior margin of the ablation zone was estimated from the anterior margin. After the experiments, the ablated pieces of bovine rump meat were cut along the electrode path and the cut planes were photographed. The US images with the estimated posterior margin were compared with the photographs and post-ablation MR images. The extracted contours of the ablation zones from 12 US fusion videos and post-ablation MR images were also matched. In the four models fused under real-time US with MR/3D US, compression from the transducer and the insertion of an electrode resulted in misregistration between the real-time US and MR images, making the estimation of the ablation zones less accurate than was achieved through fusion between real-time US and 3D US. Eight of the 12 post-ablation 3D US images were graded as good when compared with the sectioned specimens, and 10 of the 12 were graded as good in a comparison with nicotinamide adenine dinucleotide staining and histopathologic results. Estimating the posterior ablative margin using an active contour model is a feasible way of predicting the ablation area, and US/3D US fusion was more accurate than US/MR fusion.

Investigations on laser hard tissue ablation under various environments

NASA Astrophysics Data System (ADS)

Kang, H. W.; Oh, J.; Welch, A. J.

2008-06-01

The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 µm wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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

Simulation of the impact of refractive surgery ablative laser pulses with a flying-spot laser beam on intrasurgery corneal temperature.

PubMed

Shraiki, Mario; Arba-Mosquera, Samuel

2011-06-01

To evaluate ablation algorithms and temperature changes in laser refractive surgery. The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process. Ablation efficiency reduction in the periphery resulted in a lower peripheral temperature increase. Steep corneas had lesser temperature increases than flat ones. The maximum rise in temperature depends on the spatial density of the ablation pulses. For the same number of ablative pulses, myopic corrections showed the highest temperature increase, followed by myopic astigmatism, mixed astigmatism, phototherapeutic keratectomy (PTK), hyperopic astigmatism, and hyperopic treatments. The proposed model can be used, at relatively low cost, for calibration, verification, and validation of the laser systems used for ablation processes and would directly improve the quality of the results.

Conformal needle-based ultrasound ablation using EM-tracked conebeam CT image guidance

NASA Astrophysics Data System (ADS)

Burdette, E. Clif; Banovac, Filip; Diederich, Chris J.; Cheng, Patrick; Wilson, Emmanuel; Cleary, Kevin R.

2011-03-01

Numerous studies have demonstrated the efficacy of interstitial ablative approaches for the treatment of renal and hepatic tumors. Despite these promising results, current systems remain highly dependent on operator skill, and cannot treat many tumors because there is little control of the size and shape of the zone of necrosis, and no control over ablator trajectory within tissue once insertion has taken place. Additionally, tissue deformation and target motion make it extremely difficult to accurately place the ablator device into the target. Irregularly shaped target volumes typically require multiple insertions and several sequential thermal ablation procedures. This study demonstrated feasibility of spatially tracked image-guided conformal ultrasound (US) ablation for percutaneous directional ablation of diseased tissue. Tissue was prepared by suturing the liver within a pig belly and 1mm BBs placed to serve as needle targets. The image guided system used integrated electromagnetic tracking and cone-beam CT (CBCT) with conformable needlebased high-intensity US ablation in the interventional suite. Tomographic images from cone beam CT were transferred electronically to the image-guided tracking system (IGSTK). Paired-point registration was used to register the target specimen to CT images and enable navigation. Path planning is done by selecting the target BB on the GUI of the realtime tracking system and determining skin entry location until an optimal path is selected. Power was applied to create the desired ablation extent within 7-10 minutes at a thermal dose (>300eqm43). The system was successfully used to place the US ablator in planned target locations within ex-vivo kidney and liver through percutaneous access. Targeting accuracy was 3-4 mm. Sectioned specimens demonstrated uniform ablation within the planned target zone. Subsequent experiments were conducted for multiple ablator positions based upon treatment planning simulations. Ablation zones in liver were 73cc, 84cc, and 140cc for 3, 4, and 5 placements, respectively. These experiments demonstrate the feasibility of combining real-time spatially tracked image guidance with directional interstitial ultrasound ablation. Interstitial ultrasound ablation delivered on multiple needles permit the size and shape of the ablation zone to be "sculpted" by modifying the angle and intensity of the active US elements in the array. This paper summarizes the design and development of the first system incorporating thermal treatment planning and integration of a novel interstitial acoustic ablation device with integrated 3D electromagnetic tracking and guidance strategy.

Plume collimation for laser ablation electrospray ionization mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vertes, Akos; Stolee, Jessica A.

2016-06-07

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

Plume collimation for laser ablation electrospray ionization mass spectrometry

DOEpatents

Vertes, Akos; Stolee, Jessica A.

2014-09-09

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

Global ablation techniques.

PubMed

Woods, Sarah; Taylor, Betsy

2013-12-01

Global endometrial ablation techniques are a relatively new surgical technology for the treatment of heavy menstrual bleeding that can now be used even in an outpatient clinic setting. A comparison of global ablation versus earlier ablation technologies notes no significant differences in success rates and some improvement in patient satisfaction. The advantages of the newer global endometrial ablation systems include less operative time, improved recovery time, and decreased anesthetic risk. Ablation procedures performed in an outpatient surgical or clinic setting provide advantages both of potential cost savings for patients and the health care system and improved patient convenience. Copyright © 2013. Published by Elsevier Inc.

Influence of large intrahepatic blood vessels on the gross and histological characteristics of lesions produced by radiofrequency ablation in a pig liver model.

PubMed

Tamaki, Katsuyoshi; Shimizu, Ichiro; Oshio, Atsuo; Fukuno, Hiroshi; Inoue, Hiroshi; Tsutsui, Akemi; Shibata, Hiroshi; Sano, Nobuya; Ito, Susumu

2004-12-01

To determine whether the presence of large intrahepatic blood vessels (>/=3 mm) affect radiofrequency (RF)-induced coagulation necrosis, the gross and histological characteristics of RF-ablated areas proximal to or around vessels were examined in normal pig livers. An RF ablation treatment using a two-stepwise extension technique produced 12 lesions: six contained vessels (Group A), and the other six were localized around vessels (Group B). Gross examination revealed that the longest and shortest diameters of the ablated lesions were significantly larger in Group B than in Group A. In Group A, patent vessels contiguous to the lesion were present in a tongue-shaped area, whereas the lesions in Group B were spherical. Staining with nicotinamide adenine dinucleotide diaphorase was negative within the ablated area; but, if vessels were present in the ablated area, the cells around the vessels in an opposite direction to the ablation were stained blue. Roll-off can be achieved with 100% cellular destruction within a lesion that does not contain large vessels. The ablated area was decreased in lesions that contained large vessels, suggesting that the presence of large vessels in the ablated area further increases the cooling effect and may require repeated RF ablation treatment to achieve complete coagulation necrosis.

Clinical effects of non-ablative and ablative fractional lasers on various hair disorders: a case series of 17 patients.

PubMed

Cho, Suhyun; Choi, Min Ju; Zheng, Zhenlong; Goo, Boncheol; Kim, Do-Young; Cho, Sung Bin

2013-04-01

Both ablative and non-ablative fractional lasers have been applied to various uncommon hair disorders. The purpose of this study was to demonstrate the clinical effects of fractional laser therapy on the course of primary follicular and perifollicular pathologies and subsequent hair regrowth. A retrospective review of 17 patients with uncommon hair disorders - including ophiasis, autosomal recessive woolly hair/hypotrichosis, various secondary cicatricial alopecias, pubic hypotrichosis, frontal fibrosing alopecia, and perifolliculitis abscedens et suffodiens - was conducted. All patients had been treated with non-ablative and/or ablative fractional laser therapies. The mean clinical improvement score in these 17 patients was 2.2, while the mean patient satisfaction score was 2.5. Of the 17 subjects, 12 (70.6%) demonstrated a clinical response to non-ablative and/or ablative fractional laser treatments, including individuals with ophiasis, autosomal recessive woolly hair/hypotrichosis, secondary cicatricial alopecia (scleroderma and pressure-induced alopecia), frontal fibrosing alopecia, and perifolliculitis abscedens et suffodiens. Conversely, patients with long-standing ophiasis, surgical scar-induced secondary cicatricial alopecia, and pubic hypotrichosis did not respond to fractional laser therapy. Our findings demonstrate that the use of non-ablative and/or ablative fractional lasers promoted hair growth in certain cases of uncommon hair disorders without any remarkable side effects.

Artificial pneumothorax: a safe and simple method to relieve pain during microwave ablation of subpleural lung malignancy.

PubMed

Hou, Xiaowei; Zhuang, Xingjun; Zhang, Haiwen; Wang, Kai; Zhang, Yuanxin

2017-08-01

Microwave ablation has been extensively used for eliminating pulmonary tumors; however, it is usually associated with severe pain under local anesthesia. Decreasing the power and shortening the ablation time can help to relieve the pain; however, this leads to incomplete ablation and an increasing recurrence rate. This research aims to employ an artificial pneumothorax to increase both the curative effect and pain relief during the ablation procedure. From July 2013 to January 2015, nine patients presenting with 10 subpleural lung tumors (age: 44-78 years) with a high possibility of severe pain underwent the artificial pneumothorax during microwave ablation. The pain assessment scores and complications induced by the artificial pneumothorax were recorded and analyzed by a CT scan follow-up. The tumors of the nine patients were eliminated successfully using microwave ablation with artificial pneumothorax under local anesthesia. The pain caused by the ablation was relieved to a great extent with an average rate of 94.66% (range: 63.3%-100%) and all tumors were ablated completely. No severe complications occurred after the operation. The artificial pneumothorax is a reliable therapy to improve the curative effect of microwave ablation under local anesthesia by relieving the pain of the patients.

Right Ventricular Pacing for Assessment of Cavo-Tricuspid Isthmus Block.

PubMed

Venkataraman, Ganesh; Wish, Marc; Friehling, Ted; Strickberger, S Adam

2016-01-01

Background: Cavo-tricuspid isthmus (CTI) dependent atrial flutter is typically treated with cardiac ablation. Standard techniques to assess CTI block after ablation can be technically challenging. Right ventricular (RV) pacing may allow for another technique to assess CTI block after ablation. Objective: The purpose of this study was to evaluate RV pacing as a method to assess CTI block after ablation of CTI dependent atrial flutter, and define endpoints of ablation using this technique. Methods: 28 patients undergoing ablation of CTI dependent atrial flutter with intact ventriculoatrial (VA) conduction were prospectively enrolled in this study and underwent the RV pacing protocol, as well as standard coronary sinus (CS) pacing techniques to assess CTI block. Results: The mean trans-isthmus conduction interval during CS pacing (TICI CS ) at 600 and 400ms after CTI ablation was 168 +/- 9ms and 175 +/- 18ms, respectively. The mean trans-isthmus conduction interval during RV pacing (TICI RV ) at 600ms and 400ms after CTI ablation was 109 +/- 5ms and 111 +/- 5ms, respectively. A TICI RV >100ms was associated with a successful outcome after CTI ablation. Conclusions: RV pacing may add incremental value in the assessment of CTI block in patients undergoing ablation of CTI dependent atrial flutter.

An observation of ablation effect of soft biotissue by pulsed Er:YAG laser

NASA Astrophysics Data System (ADS)

Zhang, Xianzeng; Xie, Shusen; Ye, Qing; Zhan, Zhenlin

2007-02-01

Because of the unique properties with regard to the absorption in organic tissue, pulsed Er:YAG laser has found most interest for various application in medicine, such as dermatology, dentistry, and cosmetic surgery. However, consensus regarding the optimal parameters for clinical use of this tool has not been reached. In this paper, the laser ablation characteristics of soft tissue by Er:YAG laser irradiation was studied. Porcine skin tissue in vitro was used in the experiment. Laser fluences ranged from 25mJ/mm2 to 200mJ/mm2, repetition rates was 5Hz, spot sizes on the tissue surface was 2mm. The ablation effects were assessed by the means of optical microscope, ablation diameters and depths were measured with reading microscope. It was shown that the ablation of soft biotissue by pulsed Er:YAG laser was a threshold process. With appropriate choice of irradiation parameters, high quality ablation with clean, sharp cuts following closely the spatial contour of the incident beam can be achieved. The curves of ablation crater diameter and depth versus laser fluence were obtained, then the ablation threshold and ablation yield were calculated subsequently, and the influence of the number of pulses fired into a crater on ablation crater depth was also discussed.

Development of Naphthalene PLIF for Making Quantitative Measurements of Ablation Products Transport in Supersonic Flows

NASA Astrophysics Data System (ADS)

Combs, Christopher; Clemens, Noel

2014-11-01

Ablation is a multi-physics process involving heat and mass transfer and codes aiming to predict ablation are in need of experimental data pertaining to the turbulent transport of ablation products for validation. Low-temperature sublimating ablators such as naphthalene can be used to create a limited physics problem and simulate ablation at relatively low temperature conditions. At The University of Texas at Austin, a technique is being developed that uses planar laser-induced fluorescence (PLIF) of naphthalene to visualize the transport of ablation products in a supersonic flow. In the current work, naphthalene PLIF will be used to make quantitative measurements of the concentration of ablation products in a Mach 5 turbulent boundary layer. For this technique to be used for quantitative research in supersonic wind tunnel facilities, the fluorescence properties of naphthalene must first be investigated over a wide range of state conditions and excitation wavelengths. The resulting calibration of naphthalene fluorescence will be applied to the PLIF images of ablation from a boundary layer plug, yielding 2-D fields of naphthalene mole fraction. These images may help provide data necessary to validate computational models of ablative thermal protection systems for reentry vehicles. Work supported by NASA Space Technology Research Fellowship Program under grant NNX11AN55H.

Additive Effects of Mechanical Marrow Ablation and PTH Treatment on de Novo Bone Formation in Mature Adult Rats

PubMed Central

Zhang, Qing; Miller, Christopher; Bible, Jesse; Li, Jiliang; Xu, Xiaoqing; Mehta, Nozer; Gilligan, James; Vignery, Agnès; Scholz, Jodi A Carlson

2012-01-01

Mechanical ablation of bone marrow in young rats induces rapid but transient bone growth, which can be enhanced and maintained for three weeks by the administration of parathyroid hormone (PTH). Additionally, marrow ablation, followed by PTH treatment for three months leads to increased cortical thickness. In this study, we sought to determine whether PTH enhances bone formation after marrow ablation in aged rats. Aged rats underwent unilateral femoral marrow ablation and treatment with PTH or vehicle for four weeks. Both femurs from each rat were analyzed by X-ray and pQCT, then analyzed either by microCT, histology or biomechanical testing. Marrow ablation alone induced transient bone formation of low abundance that persisted over four weeks, while marrow ablation followed by PTH induced bone formation of high abundance that also persisted over four weeks. Our data confirms that the osteo-inducive effect of marrow ablation and the additive effect of marrow ablation, followed by PTH, occurs in aged rats. Our observations open new avenues of investigations in the field of tissue regeneration. Local marrow ablation, in conjunction with an anabolic agent, might provide a new platform for rapid site-directed bone growth in areas of high bone loss, such as in the hip and wrist, which are subject to fracture. PMID:24710549

Contemporary Tools and Techniques for Substrate Ablation of Ventricular Tachycardia in Structural Heart Disease.

PubMed

Hutchinson, Mathew D; Garza, Hyon-He K

2018-02-24

As we have witnessed in other arenas of catheter-based therapeutics, ventricular tachycardia (VT) ablation has become increasingly anatomical in its execution. Multi-modality imaging provides anatomical detail in substrate characterization, which is often complex in nonischemic cardiomyopathy patients. Patients with intramural, intraseptal, and epicardial substrates provide challenges in delivering effective ablation to the critical arrhythmia substrate due to the depth of origin or the presence of adjacent critical structures. Novel ablation techniques such as simultaneous unipolar or bipolar ablation can be useful to achieve greater lesion depth, though at the expense of increasing collateral damage. Disruptive technologies like stereotactic radioablation may provide a tailored approach to these complex patients while minimizing procedural risk. Substrate ablation is a cornerstone of the contemporary VT ablation procedure, and recent data suggest that it is as effective and more efficient that conventional activation guided ablation. A number of specific targets and techniques for substrate ablation have been described, and all have shown a fairly high success in achieving their acute procedural endpoint. Substrate ablation also provides a novel and reproducible procedural endpoint, which may add predictive value for VT recurrence beyond conventional programmed stimulation. Extrapolation of outcome data to nonischemic phenotypes requires caution given both the variability in substrate nonischemic distribution and the underrepresentation of these patients in previous trials.

Efficacy of microwave ablation versus radiofrequency ablation for the treatment of hepatocellular carcinoma in patients with chronic liver disease: a randomised controlled phase 2 trial.

PubMed

Vietti Violi, Naïk; Duran, Rafael; Guiu, Boris; Cercueil, Jean-Pierre; Aubé, Christophe; Digklia, Antonia; Pache, Isabelle; Deltenre, Pierre; Knebel, Jean-François; Denys, Alban

2018-05-01

Radiofrequency ablation is the recommended treatment for patients with hepatocellular carcinoma who have lesions smaller than 3 cm and are therefore not candidates for surgery. Microwave ablation is a more recent technique with certain theoretical advantages that have not yet been confirmed clinically. We aimed to compare the efficacy of both techniques in the treatment of hepatocellular carcinoma lesions of 4 cm or smaller. We did a randomised controlled, single-blinded phase 2 trial at four tertiary university centres in France and Switzerland. Patients with chronic liver disease and hepatocellular carcinoma with up to three lesions of 4 cm or smaller who were not eligible for surgery were randomised to receive microwave ablation (experimental group) or radiofrequency ablation (control group). Randomisation was centralised and done by use of a fixed block method (block size 4). Patients were randomly assigned by a co-investigator by use of the sealed opaque envelope method and were masked to the treatment; physicians were not masked to treatment, since the devices used were different. The primary outcome was the proportion of lesions with local tumour progression at 2 years of follow-up. Local tumour progression was defined as the appearance of a new nodule with features typical of hepatocellular carcinoma in the edge of the ablation zone. All analyses were done in the per-protocol population. The study is completed, but patients will continue to be followed up for 5 years. This study is registered with ClinicalTrials.gov, number NCT02859753. Between Nov 15, 2011, and Feb 27, 2015, 152 patients were randomly assigned: 76 patients to receive microwave ablation and 76 patients to receive radiofrequency ablation. For the per-protocol analysis, five patients were excluded from the microwave ablation group as were three patients from the radiofrequency ablation group. Median follow-up was 26 months (IQR 18-29) in the microwave ablation group and 25 months (18-34) in the radiofrequency ablation group. At 2 years, six (6%) of 98 lesions had local tumour progression in the microwave ablation group as did 12 (12%) of 104 in the radiofrequency ablation group (risk ratio 1·62, 95% CI 0·66-3·94; p=0·27). Complications were infrequent, with only two grade 4 complications (two events of arterial bleeding requiring embolisation, both in the microwave ablation group) and three grade 3 complications (pneumothorax; lesion of the umbilical vein; and intrahepatic segmental necrosis, all in the radiofrequency ablation group). No treatment-related deaths were reported. Although we did not find that microwave ablation was more effective than radiofrequency ablation for treatment of hepatocellular carcinoma lesions of 4 cm or smaller, our results show that the proportion of lesions with local tumour progression at 2 years of follow-up was low with both tested percutaneous methods. Microsulis (AngioDynamics). Copyright © 2018 Elsevier Ltd. All rights reserved.

Spatiotemporal Variability of Great Lakes Basin Snow Cover Ablation Events

NASA Astrophysics Data System (ADS)

Suriano, Z. J.; Leathers, D. J.

2017-12-01

In the Great Lakes basin of North America, annual runoff is dominated by snowmelt. This snowmelt-induced runoff plays an important role within the hydrologic cycle of the basin, influencing soil moisture availability and driving the seasonal cycle of spring and summer Lake levels. Despite this, relatively little is understood about the patterns and trends of snow ablation event frequency and magnitude within the Great Lakes basin. This study uses a gridded dataset of Canadian and United States surface snow depth observations to develop a regional climatology of snow ablation events from 1960-2009. An ablation event is defined as an inter-diurnal snow depth decrease within an individual grid cell. A clear seasonal cycle in ablation event frequency exists within the basin and peak ablation event frequency is latitudinally dependent. Most of the basin experiences peak ablation frequency in March, while the northern and southern regions of the basin experience respective peaks in April and February. An investigation into the inter-annual frequency of ablation events reveals ablation events significantly decrease within the northeastern and northwestern Lake Superior drainage basins and significantly increase within the eastern Lake Huron and Georgian Bay drainage basins. In the eastern Lake Huron and Georgian Bay drainage basins, larger ablation events are occurring more frequently, and a larger impact to the hydrology can be expected. Trends in ablation events are attributed primarily to changes in snowfall and snow depth across the region.

Wire ablation dynamics model and its application to imploding wire arrays of different geometries.

PubMed

Esaulov, A A; Kantsyrev, V L; Safronova, A S; Velikovich, A L; Shrestha, I K; Williamson, K M; Osborne, G C

2012-10-01

The paper presents an extended description of the amplified wire ablation dynamics model (WADM), which accounts in a single simulation for the processes of wire ablation and implosion of a wire array load of arbitrary geometry and wire material composition. To investigate the role of wire ablation effects, the implosions of cylindrical and planar wire array loads at the university based generators Cobra (Cornell University) and Zebra (University of Nevada, Reno) have been analyzed. The analysis of the experimental data shows that the wire mass ablation rate can be described as a function of the current through the wire and some coefficient defined by the wire material properties. The aluminum wires were found to ablate with the highest rate, while the copper ablation is the slowest one. The lower wire ablation rate results in a higher inward velocity of the ablated plasma, a higher rate of the energy coupling with the ablated plasma, and a more significant delay of implosion for a heavy load due to the ablation effects, which manifest the most in a cylindrical array configuration and almost vanish in a single-planar array configuration. The WADM is an efficient tool suited for wire array load design and optimization in wide parameter ranges, including the loads with specific properties needed for the inertial confinement fusion research and laboratory astrophysics experiments. The data output from the WADM simulation can be used to simplify the radiation magnetohydrodynamics modeling of the wire array plasma.

Ablative and transport fractionation of trace elements during laser sampling of glass and copper

NASA Astrophysics Data System (ADS)

Outridge, P. M.; Doherty, W.; Gregoire, D. C.

1997-12-01

The fractionation of trace elements due to ablation and transport processes was quantified during Q-switched infrared laser sampling of glass and copper reference materials. Filter-trapping of the ablated product at different points in the sample introduction system showed ablation and transport sometimes caused opposing fractionation effects, leading to a confounded measure of overall (ablative + transport) fractionation. An unexpected result was the greater ablative fractionation of some elements (Au, Ag, Bi, Te in glass and Au, Be, Bi, Ni, Te in copper) at a higher laser fluence of 1.35 × 10 4W cm -2 than at 0.62 × 10 4W cm -2, which contradicted predictions from modelling studies of ablation processes. With glass, there was an inverse logarithmic relationship between the extent of ablative and overall fractionation and element oxide melting point (OMPs), with elements with OMPs < 1000° C exhibiting overall concentration increases of 20-1340%. Fractionation during transport was quantitatively important for most certified elements in copper, and for the most volatile elements (Au, Ag, Bi, Te) in glass. Elements common to both matrices showed 50-100% higher ablative fractionation in copper, possibly because of greater heat conductance away from the ablation site causing increased element volatilisation or zone refinement. These differences between matrices indicate that non-matrix-matched standardisation is likely to provide inaccurate calibration of laser ablation inductively coupled plasma-mass spectrometry analyses of at least some elements.

Characteristics of Cavotricuspid Isthmus Ablation for Atrial Flutter Guided by Novel Parameters Using a Contact Force Catheter.

PubMed

Gould, Paul A; Booth, Cameron; Dauber, Kieran; Ng, Kevin; Claughton, Andrew; Kaye, Gerald C

2016-12-01

This study sought to investigate specific contact force (CF) parameters to guide cavotricuspid isthmus (CTI) ablation and compare the outcome with a historical control cohort. Patients (30) undergoing CTI ablation were enrolled prospectively in the Study cohort and compared with a retrospective Control cohort of 30 patients. Ablation in the Study cohort was performed using CF parameters >10 g and <40 g and a Force Time Integral (FTI) of 800 ± 10 g. The Control cohort underwent traditionally guided CTI ablation. Traditional parameters (electrogram and impedance change) were assessed in both cohorts. All ablations regardless of achieving targets were included in data analysis. Bidirectional CTI block was achieved in all of the Study and 27 of the Control cohort. Atrial flutter recurred in 3 (10%) patients (follow-up 564 ± 212 days) in the study cohort and in 3 (10%) patients (follow-up 804 ± 540 days) in the Control cohort. There were no major complications in either cohort. Traditional parameters correlated poorly with CF parameters. In the Study cohort, flutter recurrence was associated with significantly lower FTI and ablation duration, but was not associated with total average CF. CTI ablation can be safely performed using CF parameters guiding ablation, with similar long-term results to a historical ablation control group. Potentially CF parameters may provide adjunctive information to enable a more efficient CTI ablation. Further research is required to confirm this. © 2016 Wiley Periodicals, Inc.

Tumor abolition and antitumor immunostimulation by physico-chemical tumor ablation.

PubMed

Keisari, Yona

2017-01-01

Tumor ablation by thermal, chemical and radiological sources has received substantial attention for the treatment of many localized malignancies. The primary goal of most ablation procedures is to eradicate all viable malignant cells within a designated target volume through the application of energy or chemicals. Methods such as radiotherapy, chemical and biological ablation, photodynamic therapy, cryoablation, high-temperature ablation (radiofrequency, microwave, laser, and ultrasound), and electric-based ablation have been developed for focal malignancies. In recent years a large volume of data emerged on the effect of in situ tumor destruction (ablation) on inflammatory and immune components resulting in systemic anti-tumor reactions. It is evident that in situ tumor ablation can involve tumor antigen release, cross presentation and the release of DAMPS and make the tumor its own cellular vaccine. Tumor tissue destruction by in situ ablation may stimulate antigen-specific cellular immunity engendered by an inflammatory milieu. Dendritic cells (DCs) attracted to this microenvironment, will undergo maturation after internalizing cellular debris containing tumor antigens and will be exposed to damage associated molecular pattern (DAMP). Mature DCs can mediate antigen-specific cellular immunity via presentation of processed antigens to T cells. The immunomodulatory properties, exhibited by in situ ablation could portend a future collaboration with immunotherapeutic measures. In this review are summarized and discuss the preclinical and clinical studies pertinent to the phenomena of stimulation of specific anti-tumor immunity by various ablation modalities and the immunology related measures used to boost this response.

Effect of laser absorption on picosecond laser ablation of Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide

NASA Astrophysics Data System (ADS)

Wu, Baoye; Liu, Peng; Wang, Xizhao; Zhang, Fei; Deng, Leimin; Duan, Jun; Zeng, Xiaoyan

2018-05-01

Due to excellent properties, Cr12MoV mold steel, 9Cr18 stainless steel and H13A cemented carbide are widely used in industry. In this paper, the effect of absorption of laser light on ablation efficiency and roughness have been studied using a picosecond pulse Nd:YVO4 laser. The experimental results reveal that laser wavelength, original surface roughness and chemical composition play an important role in controlling ablation efficiency and roughness. Firstly, higher ablation efficiency with lower surface roughness is achieved on the ablation of 9Cr18 at 532, comparing with 1064 nm. Secondly, the ablation efficiency increases while the Ra of the ablated region decreases with the decrease of original surface roughness on ablation of Cr12MoV mold steel at 532 nm. Thirdly, the ablation efficiency of H13A cemented carbide is much higher than 9Cr18 stainless steel and Cr12MoV mold steel at 1064 nm. Scanning electron microscopy images reveals the formation of pores on the surface of 9Cr18 stainless steel and Cr12MoV mold steel at 532 nm while no pores are formed at 1064 nm. As to H13A cemented carbide, worm-like structure is formed at 1064 nm. The synergetic effects of the heat accumulation, plasma shielding and ablation threshold on laser ablation efficiency and machining quality were analyzed and discussed systematically in this paper.

Assessment of tbe Performance of Ablative Insulators Under Realistic Solid Rocket Motor Operating Conditions (a Doctoral Dissertation)

NASA Technical Reports Server (NTRS)

Martin, Heath Thomas

2013-01-01

Ablative insulators are used in the interior surfaces of solid rocket motors to prevent the mechanical structure of the rocket from failing due to intense heating by the high-temperature solid-propellant combustion products. The complexity of the ablation process underscores the need for ablative material response data procured from a realistic solid rocket motor environment, where all of the potential contributions to material degradation are present and in their appropriate proportions. For this purpose, the present study examines ablative material behavior in a laboratory-scale solid rocket motor. The test apparatus includes a planar, two-dimensional flow channel in which flat ablative material samples are installed downstream of an aluminized solid propellant grain and imaged via real-time X-ray radiography. In this way, the in-situ transient thermal response of an ablator to all of the thermal, chemical, and mechanical erosion mechanisms present in a solid rocket environment can be observed and recorded. The ablative material is instrumented with multiple micro-thermocouples, so that in-depth temperature histories are known. Both total heat flux and thermal radiation flux gauges have been designed, fabricated, and tested to characterize the thermal environment to which the ablative material samples are exposed. These tests not only allow different ablative materials to be compared in a realistic solid rocket motor environment but also improve the understanding of the mechanisms that influence the erosion behavior of a given ablative material.

Radiofrequency ablation of accessory pathways in patients with the Wolff-Parkinson-White syndrome: the long-term mortality and risk of atrial fibrillation.

PubMed

Borregaard, Rune; Lukac, Peter; Gerdes, Christian; Møller, Dorthe; Mortensen, Peter Thomas; Pedersen, Lars; Nielsen, Jens Cosedis; Jensen, Henrik Kjærulf

2015-01-01

To assess the long-term mortality and occurrence of post-ablation atrial fibrillation in patients undergoing a radiofrequency ablation for the Wolff-Parkinson-White (WPW) syndrome. A retrospective cohort study of patients (N = 362) subjected to radiofrequency ablation of the WPW syndrome at Aarhus University Hospital from 1990 to 2011. A comparison cohort (N = 3619) was generated from the Danish National Board of Health Central Population Registry. We found no significant difference in all-cause mortality when comparing the WPW group with the control group [hazard ratio (HR): 0.77 and confidence interval (CI): 0.47-1.25]. After radiofrequency ablation, the WPW group had a significantly higher risk of atrial fibrillation than the control group (HR: 4.77 and CI: 3.05-7.43). Atrial fibrillation prior to ablation (HR: 4.66 and CI: 2.09-10.41) and age over 50 years (HR: 9.79 and CI: 4.29-22.36) at the time of ablation were independent risk factors for post-ablation atrial fibrillation in the WPW group. Patients with radiofrequency ablation-treated WPW syndrome have a post-ablation mortality that is similar to the background population. The risk of atrial fibrillation remains high after radiofrequency ablation of the WPW syndrome. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.

Treatment Planning and Image Guidance for Radiofrequency Ablations of Large Tumors

PubMed Central

Ren, Hongliang; Campos-Nanez, Enrique; Yaniv, Ziv; Banovac, Filip; Abeledo, Hernan; Hata, Nobuhiko; Cleary, Kevin

2014-01-01

This article addresses the two key challenges in computer-assisted percutaneous tumor ablation: planning multiple overlapping ablations for large tumors while avoiding critical structures, and executing the prescribed plan. Towards semi-automatic treatment planning for image-guided surgical interventions, we develop a systematic approach to the needle-based ablation placement task, ranging from pre-operative planning algorithms to an intra-operative execution platform. The planning system incorporates clinical constraints on ablations and trajectories using a multiple objective optimization formulation, which consists of optimal path selection and ablation coverage optimization based on integer programming. The system implementation is presented and validated in phantom studies and on an animal model. The presented system can potentially be further extended for other ablation techniques such as cryotherapy. PMID:24235279

Effect of interconnection between cervical vagus trunk, epicardial fat pad on sinus node function, and atrial fibrillation.

PubMed

Zhou, Qina; Zhang, Ling; Wang, Kun; Xu, Xiaoxia; Ji, Meng; Zhang, Feng; Wang, Hongli; Hou, Yuemei

2014-03-01

The epicardial fat pad (FP) integrates the autonomic innervation between the extrinsic and intrinsic cardiac autonomic nervous system and affects atrial electrophysiology and pathophysiology. Eighteen dogs were divided into two groups: sequential ablation of sinoatrial node FP (SAN-FP) and atrioventricular node FP (AVN-FP). Sinus rate (SR), atrial fibrillation (AF) inducibility, and effective refractory period (ERP) changes during electrical stimulation of the vagus trunk were detected before and after ablation. In the SAN-FP group, the SR slowing, increasing AF inducibility, and ERP shortening that induced by vagus trunk stimulation were significantly attenuated by isolated SAN-FP ablation, compared with the same group prior to ablation (all P < 0.05). Subsequent AVN-FP ablation following SAN-FP ablation almost cannot produce further attenuation during vagus trunk stimulation, compared with isolated SAN-FP ablation (P > 0.05). In the AVN-FP group, SR slowing, increasing AF inducibility, and ERP shortening that induced by vagus trunk stimulation were completely eliminated by isolated AVN-FP ablation, compared with the same group prior to ablation (all P < 0.05). Subsequent SAN-FP ablation following AVN-FP ablation produced no further attenuation, compared with isolated AVN-FP ablation (P > 0.05). A neural pathway from the cervical vagus trunk to the sinus node and atrium runs through the SAN-FP, but eventually converges at the AVN-FP and also suggested that the AVN-FP serves as an "integration center" for the SAN-FP to modulate sinus node function. The AVN-FP may play a more critical role in the initiation and maintenance of AF. ©2013 First Affilated Hospital of Xingiang Medical University Pacing and Clinical Electrophysiology ©2013 Wiley Periodicals, Inc.

Luminal esophageal temperature monitoring with a deflectable esophageal temperature probe and intracardiac echocardiography may reduce esophageal injury during atrial fibrillation ablation procedures: results of a pilot study.

PubMed

Leite, Luiz R; Santos, Simone N; Maia, Henrique; Henz, Benhur D; Giuseppin, Fábio; Oliverira, Anderson; Zanatta, André R; Peres, Ayrton K; Novakoski, Clarissa; Barreto, Jose R; Vassalo, Fabrício; d'Avila, Andre; Singh, Sheldon M

2011-04-01

Luminal esophageal temperature (LET) monitoring is one strategy to minimize esophageal injury during atrial fibrillation ablation procedures. However, esophageal ulceration and fistulas have been reported despite adequate LET monitoring. The objective of this study was to assess a novel approach to LET monitoring with a deflectable LET probe on the rate of esophageal injury in patients undergoing atrial fibrillation ablation. Forty-five consecutive patients undergoing an atrial fibrillation ablation procedure followed by esophageal endoscopy were included in this prospective observational pilot study. LET monitoring was performed with a 7F deflectable ablation catheter that was positioned as close as possible to the site of left atrial ablation using the deflectable component of the catheter guided by visualization of its position on intracardiac echocardiography. Ablation in the posterior left atrial was limited to 25 W and terminated when the LET increased 2°C from baseline. Endoscopy was performed 1 to 2 days after the procedure. All patients had at least 1 LET elevation >2°C necessitating cessation of ablation. Deflection of the LET probe was needed to accurately measure LET in 5% of patients when ablating near the left pulmonary veins, whereas deflection of the LET probe was necessary in 88% of patients when ablating near the right pulmonary veins. The average maximum increase in LET was 2.5±1.5°C. No patients had esophageal thermal injury on follow-up endoscopy. A strategy of optimal LET probe placement using a deflectable LET probe and intracardiac echocardiography guidance, combined with cessation of radiofrequency ablation with a 2°C rise in LET, may reduce esophageal thermal injury during left atrial ablation procedures.

Circuit Impedance Could Be a Crucial Factor Influencing Radiofrequency Ablation Efficacy and Safety: A Myocardial Phantom Study of the Problem and its Correction.

PubMed

Bhaskaran, Abhishek; Barry, M A; Pouliopoulos, Jim; Nalliah, Chrishan; Qian, Pierre; Chik, William; Thavapalachandran, Sujitha; Davis, Lloyd; McEwan, Alistair; Thomas, Stuart; Kovoor, Pramesh; Thiagalingam, Aravinda

2016-03-01

Circuit impedance could affect the safety and efficacy of radiofrequency (RF) ablation. To perform irrigated RF ablations with graded impedance to compare (1) lesion dimensions and overheated dimensions in fixed power ablations (2) and in power corrected ablations. Ablations were performed with irrigated Navistar Thermocool catheter and Stockert EP shuttle generator at settings of 40 W power for 60 seconds, in a previously validated myocardial phantom. The impedance of the circuit was set at 60 Ω, 80 Ω, 100 Ω, 120 Ω, 140 Ω, and 160 Ω. The lesion and overheated dimensions were measured at 53 °C and 80 °C isotherms, respectively. In the second set of ablations, power was corrected according to circuit impedance. In total, 70 ablations were performed. The lesion volume was 72.0 ± 4.8% and 44.7 ± 4.6% higher at 80 Ω and 100 Ω, respectively, compared to that at 120 Ω and it was 15.4 ± 1.2%, 28.1 ± 2.0%, and 38.0 ± 1.8% lower at 140 Ω, 160 Ω, and 180 Ω, respectively. The overheated volume was four times larger when impedance was reduced to 80 Ω from 100 Ω. It was absent at 120 Ω and above. In the power corrected ablations, the lesion volumes were similar to that of 40 W/120 Ω ablations and there was no evidence of overheating. The lesion and overheated dimensions were significantly larger with lower circuit impedance during irrigated RF ablation and the lesion size was smaller in high impedance ablations. Power delivery adjusted to impedance using a simple equation improved the consistency of lesion formation and prevented overheating. © 2015 Wiley Periodicals, Inc.

Near-IR imaging of erbium laser ablation with a water spray

NASA Astrophysics Data System (ADS)

Darling, Cynthia L.; Maffei, Marie E.; Fried, William A.; Fried, Daniel

2008-02-01

Near-IR (NIR) imaging can be used to view the formation of ablation craters during laser ablation since the enamel of the tooth is almost completely transparent near 1310-nm1. Laser ablation craters can be monitored under varying irradiation conditions to assess peripheral thermal and transient-stress induced damage, measure the rate and efficiency of ablation and provide insight into the ablation mechanism. There are fundamental differences in the mechanism of enamel ablation using erbium lasers versus carbon dioxide laser systems due to the nature of the primary absorber and it is necessary to have water present on the tooth surface for efficient ablation at erbium laser wavelengths. In this study, sound human tooth sections of approximately 2-3-mm thickness were irradiated by free running and Q-switched Er:YAG & Er:YSGG lasers 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 a band-pass filter centered at 1310-nm combined with an InGaAs area camera with a NIR zoom microscope. Obvious differences in the crater evolution were observed between CO2 and erbium lasers. Ablation stalled after a few laser pulses without a water spray as anticipated. Efficient ablation was re-initiated by resuming the water spray. Micro-fractures were continuously produced apparently driven along prism lines during multi-pulse ablation. These fractures or fissures appeared to merge together as the crater evolved to form the leading edge of the ablation crater. These observations support the proposed thermo-mechanical mechanisms of erbium laser involving the strong mechanical forces generated by selective absorption by water.

Ablation of Rotor and Focal Sources Reduces Late Recurrence of Atrial Fibrillation Compared to Trigger Ablation Alone

PubMed Central

Narayan, Sanjiv M.; Baykaner, Tina; Clopton, Paul; Schricker, Amir; Lalani, Gautam; Krummen, David E.; Shivkumar, Kalyanam; Miller, John M.

2014-01-01

Objectives To determine if ablation that targets patient-specific AF-sustaining substrates (rotors or focal sources) is more durable than trigger ablation alone at preventing late AF recurrences. Background Late recurrence substantially limits the efficacy of pulmonary vein (PV) isolation for AF, and is associated with PV reconnection and the emergence of new triggers. Methods We performed 3 year follow-up of the CONFIRM trial, in which 92 consecutive AF patients (70.7% persistent) underwent novel computational mapping to reveal a median of 2 (IQR 1–2) rotors or focal sources in 97.7% of patients during AF. Ablation comprised source (Focal Impulse and Rotor Modulation, FIRM) then conventional ablation in n=27 (FIRM-guided), and conventional ablation alone in n=65 (FIRM-blinded). Patients were followed with implanted ECG monitors when possible (85.2% FIRM guided, 23.1% FIRM-blinded). Results On 890 days follow-up (median; IQR 224–1563) compared FIRM-blinded therapy, patients receiving FIRM-guided ablation maintained higher freedom from AF after 1.2±0.4 procedures (median 1, IQR 1–1) (77.8% vs 38.5%; p=0.001) and a single procedure (p>0.001), and higher freedom from all atrial arrhythmias (p=0.003). Freedom from AF was higher when ablation directly or coincidentally passed through sources than when it missed sources (p>0.001). CONCLUSIONS FIRM-guided ablation is more durable than conventional trigger-based ablation at preventing 3 year AF recurrence. Future studies should investigate how ablation of patient-specific AF-sustaining rotors and focal sources alters the natural history of arrhythmia recurrence. PMID:24632280

Robotically Assisted Sonic Therapy as a Noninvasive Nonthermal Ablation Modality: Proof of Concept in a Porcine Liver Model.

PubMed

Smolock, Amanda R; Cristescu, Mircea M; Vlaisavljevich, Eli; Gendron-Fitzpatrick, Annette; Green, Chelsey; Cannata, Jonathan; Ziemlewicz, Timothy J; Lee, Fred T

2018-05-01

Purpose To determine the feasibility of creating a clinically relevant hepatic ablation (ie, an ablation zone capable of treating a 2-cm liver tumor) by using robotically assisted sonic therapy (RAST), a noninvasive and nonthermal focused ultrasound therapy based on histotripsy. Materials and Methods This study was approved by the institutional animal use and care committee. Ten female pigs were treated with RAST in a single session with a prescribed 3-cm spherical treatment region and immediately underwent abdominal magnetic resonance (MR) imaging. Three pigs (acute group) were sacrificed immediately following MR imaging. Seven pigs (chronic group) were survived for approximately 4 weeks and were reimaged with MR imaging immediately before sacrifice. Animals underwent necropsy and harvesting of the liver for histologic evaluation of the ablation zone. RAST ablations were performed with a 700-kHz therapy transducer. Student t tests were performed to compare prescribed versus achieved ablation diameter, difference of sphericity from 1, and change in ablation zone volume from acute to chronic imaging. Results Ablation zones had a sphericity index of 0.99 ± 0.01 (standard deviation) (P < .001 vs sphericity index of 1). Anteroposterior and transverse dimensions were not significantly different from prescribed (3.4 ± 0.7; P = .08 and 3.2 ± 0.8; P = .29, respectively). The craniocaudal dimension was significantly larger than prescribed (3.8 ± 1.1; P = .04), likely because of respiratory motion. The central ablation zone demonstrated complete cell destruction and a zone of partial necrosis. A fibrous capsule surrounded the ablation zone by 4 weeks. On 4-week follow-up images, ablation zone volumes decreased by 64% (P < .001). Conclusion RAST is capable of producing clinically relevant ablation zones in a noninvasive manner in a porcine model. © RSNA, 2018.

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

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

Impact of catheter ablation with remote magnetic navigation on procedural outcomes in patients with persistent and long-standing persistent atrial fibrillation.

PubMed

Jin, Qi; Pehrson, Steen; Jacobsen, Peter Karl; Chen, Xu

2015-11-01

The objectives of this study were to assess the procedural outcomes of persistent and long-standing persistent atrial fibrillation (PsAF and L-PsAF) ablation guided by remote magnetic navigation (RMN), and to detect factors predicting acute restoration of sinus rhythm (SR) by ablation with RMN. A total of 313 patients (275 male, age 59 ± 9.5 years) with PsAF (187/313) or L-PsAF (126/313) undergoing ablation using RMN were included. Patients' disease history, pulmonary venous anatomy, left atrial (LA) volume, procedure time, mapping plus ablation time, radiofrequency (RF) ablation time, fluoroscopy time, radiation dose, and complications were assessed. Stepwise regression was used to predict which variable could best predict acute restoration from AF to SR by ablation. Compared to PsAF, procedure time and RF ablation time were significantly increased in patients with L-PsAF (P = 0.01 and P < 0.001, respectively). No major complications occurred during the procedures in either PsAF or L-PsAF patients. Fifty five of 313 patients converted directly to SR by ablation. Compared to L-PsAF, the rate of SR restoration was significantly higher in PsAF (21 vs 12%, P = 0.03). Stepwise regression analysis showed LA volume was the primary parameter affecting SR restoration (P = 0.01). The LA volume of patients without direct SR restoration by ablation was 24% greater than that of patients with SR restoration (P < 0.001). Catheter ablation using RMN is a safe and effective method for PsAF and L-PsAF. LA volume could be a predictor of direct restoration of SR from sustaining AF by ablation using RMN.

Theoretical analyses of the refractive implications of transepithelial PRK ablations.

PubMed

Arba Mosquera, Samuel; Awwad, Shady T

2013-07-01

To analyse the refractive implications of single-step, transepithelial photorefractive keratectomy (TransPRK) ablations. A simulation for quantifying the refractive implications of TransPRK ablations has been developed. The simulation includes a simple modelling of corneal epithelial profiles, epithelial ablation profiles as well as refractive ablation profiles, and allows the analytical quantification of the refractive implications of TransPRK in terms of wasted tissue, achieved optical zone (OZ) and induced refractive error. Wasted tissue occurs whenever the actual corneal epithelial profile is thinner than the applied epithelial ablation profile, achieved OZ is reduced whenever the actual corneal epithelial profile is thicker than the applied epithelial ablation profile and additional refractive errors are induced whenever the actual difference centre-to-periphery in the corneal epithelial profile deviates from the difference in the applied epithelial ablation profile. The refractive implications of TransPRK ablations can be quantified using simple theoretical simulations. These implications can be wasted tissue (∼14 µm, if the corneal epithelial profile is thinner than the ablated one), reduced OZ (if the corneal epithelial profile is thicker than ablated one, very severe for low corrections) and additional refractive errors (∼0.66 D, if the centre-to-periphery progression of the corneal epithelial profile deviates from the progression of the ablated one). When TransPRK profiles are applied to normal, not previously treated, non-pathologic corneas, no specific refractive implications associated to the transepithelial profile can be anticipated; TransPRK would provide refractive outcomes equal to those of standard PRK. Adjustments for the planned OZ and, in the event of retreatments, for the target sphere can be easily derived.

Ablation of ghrelin receptor in leptin-deficient ob/ob mice has paradoxical effects on glucose homeostasis when compared with ablation of ghrelin in ob/ob mice.

PubMed

Ma, Xiaojun; Lin, Yuezhen; Lin, Ligen; Qin, Guijun; Pereira, Fred A; Haymond, Morey W; Butte, Nancy F; Sun, Yuxiang

2012-08-01

The orexigenic hormone ghrelin is important in diabetes because it has an inhibitory effect on insulin secretion. Ghrelin ablation in leptin-deficient ob/ob (Ghrelin(-/-):ob/ob) mice increases insulin secretion and improves hyperglycemia. The physiologically relevant ghrelin receptor is the growth hormone secretagogue receptor (GHS-R), and GHS-R antagonists are thought to be an effective strategy for treating diabetes. However, since some of ghrelin's effects are independent of GHS-R, we have utilized genetic approaches to determine whether ghrelin's effect on insulin secretion is mediated through GHS-R and whether GHS-R antagonism indeed inhibits insulin secretion. We investigated the effects of GHS-R on glucose homeostasis in Ghsr-ablated ob/ob mice (Ghsr(-/-):ob/ob). Ghsr ablation did not rescue the hyperphagia, obesity, or insulin resistance of ob/ob mice. Surprisingly, Ghsr ablation worsened the hyperglycemia, decreased insulin, and impaired glucose tolerance. Consistently, Ghsr ablation in ob/ob mice upregulated negative β-cell regulators (such as UCP-2, SREBP-1c, ChREBP, and MIF-1) and downregulated positive β-cell regulators (such as HIF-1α, FGF-21, and PDX-1) in whole pancreas; this suggests that Ghsr ablation impairs pancreatic β-cell function in leptin deficiency. Of note, Ghsr ablation in ob/ob mice did not affect the islet size; the average islet size of Ghsr(-/-):ob/ob mice is similar to that of ob/ob mice. In summary, because Ghsr ablation in leptin deficiency impairs insulin secretion and worsens hyperglycemia, this suggests that GHS-R antagonists may actually aggravate diabetes under certain conditions. The paradoxical effects of ghrelin ablation and Ghsr ablation in ob/ob mice highlight the complexity of the ghrelin-signaling pathway.

ACUTE TERMINATION OF HUMAN ATRIAL FIBRILLATION BY IDENTIFICATION AND CATHETER ABLATION OF LOCALIZED ROTORS AND SOURCES

PubMed Central

Shivkumar, Kalyanam; Ellenbogen, Kenneth A.; Hummel, John D.; Miller, John M.; Steinberg, Jonathan S.

2012-01-01

Catheter ablation of atrial fibrillation (AF) currently relies on eliminating triggers, and no reliable method exists to map the arrhythmia itself to identify ablation targets. The aim of this multicenter study was to define the use of Focal Impulse and Rotor Modulation (FIRM) for identifying ablation targets. METHODS We prospectively enrolled the first (n=14, 11 males) consecutive patients undergoing FIRM guided ablation for persistent (n=11) and paroxysmal AF at 5 centers. A 64 pole basket catheter was used for panoramic right and left atrial mapping during AF. AF electrograms were analyzed using a novel system to identify sustained rotors (spiral waves), or focal beats (centrifugal activation to surrounding atrium). Ablation was performed first at identified sources. The primary endpoints were acute AF termination or organization (>10 % cycle length prolongation). Conventional ablation was performed only after FIRM guided ablation. RESULTS 12/14 cases were mapped. AF sources were demonstrated in all patients (average of 1.9±0.8 per patient). Sources were left atrial in 18 cases, and right atrial in 5 cases, and 21/23 were rotors. FIRM guided ablation achieved the acute endpoint in all patients, consisting of AF termination in n=8 (4.9±3.9 min at the primary source), and organization in n=4. Total FIRM time for all patients was 12.3±8.6 min. CONCLUSIONS FIRM guided ablation revealed localized AF rotors/focal sources in patients with paroxysmal, persistent and longstanding persistent AF. Brief targeted FIRM guided ablation at a priori identified sites terminated or substantially organized AF in all cases prior to any other ablation. PMID:23130890

Comparison of the aerodynamic characteristics of an ablating and nonablating blunted conical body

NASA Technical Reports Server (NTRS)

Kruse, R. L.

1973-01-01

The influence of ablation on the aerodynamic characteristics of a blunted slender cone was investigated. Plastic models were launched in free flight at ablating conditions. The results were compared with results of similar tests using metal nonablating models. Ablation was found to decrease the dynamic stability and the drag, but had little effect on static stability and lift. The plastic models appeared to experience ablation-induced roll.

[Thoracoscopic, epicardial ablation of atrial fibrillation using the COBRA Fusion system as the first part of hybrid ablation].

PubMed

Budera, P; Osmančík, P; Talavera, D; Fojt, R; Kraupnerová, A; Žďárská, J; Vaněk, T; Straka, Z

2017-01-01

Treatment of persistent and long-standing persistent atrial fibrillation is not successfully managed by methods of catheter ablation or pharmacotherapy. Hybrid ablation (i.e. combination of minimally invasive surgical ablation, followed by electrophysiological assessment and subsequent endocardial catheter ablation to complete the entire intended procedure) presents an ever more used and very promising treatment method. Patients underwent thoracoscopic ablation of pulmonary veins and posterior wall of the left atrium (the box-lesion) with use of the COBRA Fusion catheter; thoracoscopic occlusion of the left atrial appendage using the AtriClip system was also done in later patients. After 23 months, electrophysiological assessment and catheter ablation followed. In this article we summarize a strategy of the surgical part of the hybrid procedure performed in our centre. We describe the surgery itself (including possible periprocedural complications) and we also present our short-term results, especially with respect to subsequent electrophysiological findings. Data of the first 51 patients were analyzed. The first 25 patients underwent unilateral ablation; the mean time of surgery was 102 min. Subsequent 26 patients underwent the bilateral procedure with the mean surgery time of 160 min. Serious complications included 1 stroke, 1 phrenic nerve palsy and 2 surgical re-explorations for bleeding. After 1 month, 65% of patients showed sinus rhythm. The box-lesion was found complete during electrophysiological assessment in 38% of patients and after catheter ablation, 96% of patients were discharged in sinus rhythm. The surgical part of the hybrid procedure with use of the minimally invasive approach and the COBRA Fusion catheter is a well-feasible method with a low number of periprocedural complications. For electrophysiologists, it provides a very good basis for successful completion of the hybrid ablation.Key words: atrial fibrillation hybrid ablation - thoracoscopy catheter ablation electrophysiology assessment.

Low pressure laser ablation coupled to inductively coupled plasma mass spectrometry

NASA Astrophysics Data System (ADS)

Fliegel, Daniel; Günther, Detlef

2006-07-01

The particle size distribution in laser ablation inductively coupled plasma mass spectrometry is known to be a critical parameter for complete vaporization of particles. Any strategy to reduce the particle size distribution of laser generated aerosols has the potential to increase the ion signal intensity and to reduce fractionation effects. Due to the fact that vapor generation, nucleation, condensation, and agglomeration take place within an extremely short period of time, ablation under atmospheric pressure might not allow influencing these processes while under reduced pressure condition the cooling of the aerosol and therefore the condensation is expected to be slower. In this study, a low pressure laser ablation cell for the generation of laser aerosols was coupled to an ICP-MS. In contrast to the previously developed trapped ablation mode, the newly designed cell allows the adjustment of the pressure in the ablation cell between 20 and 1400 mbar prior to the ablation. Ablation experiments carried out using this configuration showed a dependence of the aerosol properties (size distribution and particle structure) on the ablation cell pressure. The intensity ratio U/Th measured as a figure of merit for complete vaporization within the ICP indicated a change in the aerosol structure at approximately 500 mbar toward smaller particle size. A significant difference between low pressure and at ambient pressure ablated aerosol was observed. The intensity ratios (U/Th) of the ablated sample moves closer to the bulk composition at lower pressures at the expense of sensitivity. Therefore the decrease in the ICP-MS signal intensity in the low pressure cell can be attributed to vapor deposition within the ablation cell walls. Moreover, scanning electron microscope images of aerosols collected on filters after the low pressure ablation cell suggest the possibility of a slower cooling velocity of the aerosol, which was observed in the condensed material on the surface of ejected spherical particles. The expansion of the laser aerosol was also investigated using polished brass substrates in the expansion path-way for particle collection.

Interferometric analysis of the ablation profile in refractive surgery

NASA Astrophysics Data System (ADS)

Rodríguez-Rodríguez, M. I.; López-Olazagasti, E.; Rosales, M. A.; Ramírez-Zavaleta, G.; Cantú, R.; Tepichín, E.

2008-08-01

In ophthalmology, the laser excimer corneal surface ablation used to correct the refractive eye defects, such as myopia, astigmatism and hyperopia and, more recently, presbyopia is known as refractive surgery. Typically, the characterization of the corresponding technique, as well as the laser accuracy, is performed by analyzing standard ablation profiles made on PMMA (polymethylmethacrylate) plates. A drawback of this technique is that those plates do not necessarily represent the dimensions of the cornea during the ablation. On the other hand, due to the time varying process of the eye aberrations, the direct eye refractometric measurements can produce some errors. We report in this work the interferometric analysis of the ablation profile obtained with refractive surgery, applied directly on a contact lens. In this case, the resultant ablation profile might be closer to the real profile as well as time invariant. We use, as a reference, a similar contact lens without ablation. The preliminary results of the characterization of the corresponding ablation profile are also presented.

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

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2017-09-01

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

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

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-06-01

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

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

PubMed

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

2015-03-01

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

Creation of short microwave ablation zones: in vivo characterization of single and paired modified triaxial antennas.

PubMed

Lubner, Meghan G; Ziemlewicz, Tim J; Hinshaw, J Louis; Lee, Fred T; Sampson, Lisa A; Brace, Christopher L

2014-10-01

To characterize modified triaxial microwave antennas configured to produce short ablation zones. Fifty single-antenna and 27 paired-antenna hepatic ablations were performed in domestic swine (N = 11) with 17-gauge gas-cooled modified triaxial antennas powered at 65 W from a 2.45-GHz generator. Single-antenna ablations were performed at 2 (n = 16), 5 (n = 21), and 10 (n = 13) minutes. Paired-antenna ablations were performed at 1-cm and 2-cm spacing for 5 (n = 7 and n = 8, respectively) and 10 minutes (n = 7 and n = 5, respectively). Mean transverse width, length, and aspect ratio of sectioned ablation zones were measured and compared. For single antennas, mean ablation zone lengths were 2.9 cm ± 0.45, 3.5 cm ± 0.55, and 4.2 cm ± 0.40 at 2, 5, and 10 minutes, respectively. Mean widths were 1.8 cm ± 0.3, 2.0 cm ± 0.32, and 2.5 cm ± 0.25 at 2, 5, and 10 minutes, respectively. For paired antennas, mean length at 5 minutes with 1-cm and 2-cm spacing and 10 minutes with 1-cm and 2-cm spacing was 4.2 cm ± 0.9, 4.9 cm ± 1.0, 4.8 cm ± 0.5, and 4.8 cm ± 1.3, respectively. Mean width was 3.1 cm ± 1.0, 4.4 cm ± 0.7, 3.8 cm ± 0.4, and 4.5 cm ± 0.7, respectively. Paired-antenna ablations were more spherical (aspect ratios, 0.72-0.79 for 5-10 min) than single-antenna ablations (aspect ratios, 0.57-0.59). For paired-antenna ablations, 1-cm spacing appeared optimal, with improved circularity and decreased clefting compared with 2-cm spacing (circularity, 0.85 at 1 cm, 0.78 at 2 cm). Modified triaxial antennas can generate relatively short, spherical ablation zones. Paired-antenna ablations were rounder and larger in transverse dimension than single antenna ablations, with 1-cm spacing optimal for confluence of the ablation zone. Copyright © 2014 SIR. Published by Elsevier Inc. All rights reserved.

Creation of short microwave ablation zones: In Vivo Characterization of single and paired Modified Triaxial Antennas Laboratory Investigation

PubMed Central

Lubner, Meghan G.; Ziemlewicz, Tim J; Hinshaw, J. Louis; Lee, Fred T.; Sampson, Lisa J.; Brace, Chris L.

2014-01-01

Purpose To characterize modified triaxial microwave antennas configured to produce short ablation zones. Materials and Methods 50 single- and 27 paired-antenna hepatic ablations were performed in domestic swine (n=11) with 17-gauge, gas-cooled modified triaxial antennas powered at 65W from a 2.45 GHz generator. Single-antenna ablations were performed at 2 (n=16), 5 (n=21), and 10 (n=13) minutes. Paired-antenna ablations were performed at 1-cm and 2-cm spacing for 5 (n=7, n=8) and 10 minutes (n=7, n=5). Mean transverse width, length and aspect ratio of sectioned ablation zones were measured and compared. Results For single antennas, mean ablation zone length was 2.9±0.45, 3.5±0.55 and 4.2±0.40 cm at 2, 5, and 10 minutes respectively. Mean width was 1.8±0.3, 2.0±0.32, 2.5±0.25 cm at 2, 5, and 10 minutes. For paired antennas, mean length at 5 min 1 and 2 cm and 10 min 1 and 2 cm spacing was 4.2±0.9, 4.4±0.9, 4.8±0.5 and 4.3±0.9 cm respectively. Mean width was 3.1±1.0, 4.0±0.8 and 3.8±0.4, 4.2±0.6 cm respectively. Paired-antenna ablations were more spherical (aspect ratios 0.72-0.79 for 5-10 min) than single-antenna ablations (0.57-0.59). For paired-antenna ablations, 1 cm spacing appeared optimal, with improved circularity and decreased clefting compared to 2 cm spacing (circ 1 cm 0.85, 2 cm 0.78). Conclusion Modified triaxial antennas can generate relatively short, spherical ablation zones. Paired-antenna ablations were rounder and larger in transverse dimension compared to single antenna ablations, with 1 cm spacing optimal for confluence of the ablation zone. PMID:25156644

Heat Sink Effect on Tumor Ablation Characteristics as Observed in Monopolar Radiofrequency, Bipolar Radiofrequency, and Microwave, Using Ex Vivo Calf Liver Model

PubMed Central

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

2015-01-01

Abstract Thermal ablation of liver tumors near large blood vessels is affected by the cooling effect of blood flow, leading to incomplete ablation. Hence, we conducted a comparative investigation of heat sink effect in monopolar (MP) and bipolar (BP) radiofrequency ablation (RFA), and microwave (MW) ablation devices. With a perfused calf liver, the ablative performances (volume, mass, density, dimensions), with and without heat sink, were measured. Heat sink was present when the ablative tip of the probes were 8.0 mm close to a major hepatic vein and absent when >30 mm away. Temperatures (T1 and T2) on either side of the hepatic vein near the tip of the probes, heating probe temperature (T3), outlet perfusate temperature (T4), and ablation time were monitored. With or without heat sink, BP radiofrequency ablated a larger volume and mass, compared with MP RFA or MW ablation, with latter device producing the highest density of tissue ablated. MW ablation produced an ellipsoidal shape while radiofrequency devices produced spheres. Percentage heat sink effect in Bipolar radiofrequency : Mono-polar radiofrequency : Microwave was (Volume) 33:41:22; (mass) 23:56:34; (density) 9.0:26:18; and (relative elipscity) 5.8:12.9:1.3, indicating that BP and MW devices were less affected. Percentage heat sink effect on time (minutes) to reach maximum temperature (W) = 13.28:9.2:29.8; time at maximum temperature (X) is 87:66:16.66; temperature difference (Y) between the thermal probes (T3) and the temperature (T1 + T2)/2 on either side of the hepatic vessel was 100:87:20; and temperature difference between the (T1 + T2)/2 and temperature of outlet circulating solution (T4), Z was 20.33:30.23:37.5. MW and BP radiofrequencies were less affected by heat sink while MP RFA was the most affected. With a single ablation, BP radiofrequency ablated a larger volume and mass regardless of heat sink. PMID:25738477

Confocal microscopy to guide laser ablation of basal cell carinoma: a preliminary feasibility study

NASA Astrophysics Data System (ADS)

Larson, Bjorg A.; Sierra, Heidy; Chen, Jason; Rajadhyaksha, Milind

2013-03-01

Laser ablation may be a promising method for removal of skin lesions, with the potential for better cosmetic outcomes and reduced scarring and infection. An obstacle to implementing laser ablation is that the treatment leaves no tissue for histopathological analysis. Pre-operative and intra-operative mapping of BCCs using confocal microscopy may guide the ablation of the tumor until all tumor is removed. We demonstrate preliminary feasibility of confocal microscopy to guide laser ablation of BCCs in freshly excised tissue from Mohs surgery. A 2940 nm Er:YAG laser provides efficient ablation of tumor with reduced thermal damage to the surrounding tissue.

Atomistic simulation of laser-pulse surface modification: Predictions of models with various length and time scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Starikov, Sergey V., E-mail: starikov@ihed.ras.ru; Pisarev, Vasily V.; Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412

2015-04-07

In this work, the femtosecond laser pulse modification of surface is studied for aluminium (Al) and gold (Au) by use of two-temperature atomistic simulation. The results are obtained for various atomistic models with different scales: from pseudo-one-dimensional to full-scale three-dimensional simulation. The surface modification after laser irradiation can be caused by ablation and melting. For low energy laser pulses, the nanoscale ripples may be induced on a surface by melting without laser ablation. In this case, nanoscale changes of the surface are due to a splash of molten metal under temperature gradient. Laser ablation occurs at a higher pulse energymore » when a crater is formed on the surface. There are essential differences between Al ablation and Au ablation. In the first step of shock-wave induced ablation, swelling and void formation occur for both metals. However, the simulation of ablation in gold shows an additional athermal type of ablation that is associated with electron pressure relaxation. This type of ablation takes place at the surface layer, at a depth of several nanometers, and does not induce swelling.« less

Assessment of Ablative Therapies in Swine: Response of Respiratory Diaphragm to Varying Doses.

PubMed

Singal, Ashish; Mattison, Lars M; Soule, Charles L; Ballard, John R; Rudie, Eric N; Cressman, Erik N K; Iaizzo, Paul A

2018-03-28

Ablation is a common procedure for treating patients with cancer, cardiac arrhythmia, and other conditions, yet it can cause collateral injury to the respiratory diaphragm. Collateral injury can alter the diaphragm's properties and/or lead to respiratory dysfunction. Thus, it is important to understand the diaphragm's physiologic and biomechanical properties in response to ablation therapies, in order to better understand ablative modalities, minimize complications, and maximize the safety and efficacy of ablative procedures. In this study, we analyzed physiologic and biomechanical properties of swine respiratory diaphragm muscle bundles when exposed to 5 ablative modalities. To assess physiologic properties, we performed in vitro tissue bath studies and measured changes in peak force and baseline force. To assess biomechanical properties, we performed uniaxial stress tests, measuring force-displacement responses, stress-strain characteristics, and avulsion forces. After treating the muscle bundles with all 5 ablative modalities, we observed dose-dependent sustained reductions in peak force and transient increases in baseline force-but no consistent dose-dependent biomechanical responses. These data provide novel insights into the effects of various ablative modalities on the respiratory diaphragm, insights that could enable improvements in ablative techniques and therapies.

Ultrafast laser ablation for targeted atherosclerotic plaque removal

NASA Astrophysics Data System (ADS)

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

2015-07-01

Coronary artery disease, the main cause of heart disease, develops as immune cells and lipids accumulate into plaques within the coronary arterial wall. As a plaque grows, the tissue layer (fibrous cap) separating it from the blood flow becomes thinner and increasingly susceptible to rupturing and causing a potentially lethal thrombosis. The stabilization and/or treatment of atherosclerotic plaque is required to prevent rupturing and remains an unsolved medical problem. Here we show for the first time targeted, subsurface ablation of atherosclerotic plaque using ultrafast laser pulses. Excised atherosclerotic mouse aortas were ablated with ultrafast near-infrared (NIR) laser pulses. The physical damage was characterized with histological sections of the ablated atherosclerotic arteries from six different mice. The ultrafast ablation system was integrated with optical coherence tomography (OCT) imaging for plaque-specific targeting and monitoring of the resulting ablation volume. We find that ultrafast ablation of plaque just below the surface is possible without causing damage to the fibrous cap, which indicates the potential use of ultrafast ablation for subsurface atherosclerotic plaque removal. We further demonstrate ex vivo subsurface ablation of a plaque volume through a catheter device with the high-energy ultrafast pulse delivered via hollow-core photonic crystal fiber.

State-of-the-art and emerging technologies for atrial fibrillation ablation.

PubMed

Dewire, Jane; Calkins, Hugh

2010-03-01

Catheter ablation is an important treatment modality for patients with atrial fibrillation (AF). Although the superiority of catheter ablation over antiarrhythmic drug therapy has been demonstrated in middle-aged patients with paroxysmal AF, the role the procedure in other patient subgroups-particularly those with long-standing persistent AF-has not been well defined. Furthermore, although AF ablation can be performed with reasonable efficacy and safety by experienced operators, long-term success rates for single procedures are suboptimal. Fortunately, extensive ongoing research will improve our understanding of the mechanisms of AF, and considerable funds are being invested in developing new ablation technologies to improve patient outcomes. These technologies include ablation catheters designed to electrically isolate the pulmonary veins with improved safety, efficacy, and speed, catheters designed to deliver radiofrequency energy with improved precision, robotic systems to address the technological demands of the procedure, improved imaging and electrical mapping systems, and MRI-guided ablation strategies. The tools, technologies, and techniques that will ultimately stand the test of time and become the standard approach to AF ablation in the future remain unclear. However, technological advances are sure to result in the necessary improvements in the safety and efficacy of AF ablation procedures.

Infrared thermography and thermocouple mapping of radiofrequency renal ablation to assess treatment adequacy and ablation margins.

PubMed

Ogan, Kenneth; Roberts, William W; Wilhelm, David M; Bonnell, Leonard; Leiner, Dennis; Lindberg, Guy; Kavoussi, Louis R; Cadeddu, Jeffrey A

2003-07-01

The primary disadvantage of renal tumor RF ablation is the inability to monitor the intraoperative propagation of the RF lesion with real-time imaging. We sought to assess whether adequately lethal temperatures are obtained at the margins of the intended ablation zone using laparoscopic thermography to monitor radiofrequency (RF) lesions in real time, thermocouple measurements, and histopathologic evaluation. Renal RF lesions were created under direct laparoscopic vision in the upper (1 cm diameter) and lower (2 cm) poles of the right kidney in 5 female pigs. The RF lesions were produced with the RITA generator and probe, set at 105 degrees C for 5-minute ablations. During RF treatment, a laparoscopic infrared (IR) camera measured the surface parenchymal temperatures, as did multiple thermocouples. The pigs were then either immediately killed (n = 3) or allowed to live for 2 weeks (n = 2). The kidneys were removed to correlate the temperature measurements with histologic analysis of the ablated lesion. Using a threshold temperature of greater than 70 degrees C for visual "temperature" color change, the IR camera identified the region of pathologic necrosis of the renal parenchyma during RF ablation. Thermocouple measurements demonstrated that the temperatures at the intended ablation radius reached 77.5 degrees C at the renal surface and 83.7 degrees C centrally, and temperatures 5 mm beyond the set radius reached 52.6 degrees C at the surface and 47.7 degrees C centrally. The average diameter of the gross lesion on the surface of the kidney measured 17.1 mm and 22.4 mm for 1-cm and 2-cm ablations, respectively. These surface measurements correlated with an average diameter of 16.1 mm and 15.9 mm (1-cm and 2-cm ablations, respectively) as measured with the IR camera. All cells within these ablation zones were nonviable by nicotinamide adenine dinucleotide diaphorase analysis. The average depth of the lesions measured 19 mm (1-cm ablation) and 25 mm (2-cm ablation) on gross histologic examination. The laparoscopic IR camera is able to monitor the surface renal temperatures during RF treatment. Thermocouple measurements during RF ablation confirmed the thermographic findings and demonstrated that lethal temperatures at the margin of the intended treatment zone are routinely obtained and that a rapid decline in temperature occurs beyond the predicted ablation margin.

Relationship between LIBS Ablation and Pit Volume for Geologic Samples: Applications for in situ Absolute Geochronology

NASA Technical Reports Server (NTRS)

Devismes, D.; Cohen, Barbara A.

2014-01-01

In planetary sciences, in situ absolute geochronology is a scientific and engineering challenge. Currently, the age of the Martian surface can only be determined by crater density counting. However this method has significant uncertainties and needs to be calibrated with absolute ages. We are developing an instrument to acquire in situ absolute geochronology based on the K-Ar method. The protocol is based on the laser ablation of a rock by hundreds of laser pulses. Laser Induced Breakdown Spectroscopy (LIBS) gives the potassium content of the ablated material and a mass spectrometer (quadrupole or ion trap) measures the quantity of 40Ar released. In order to accurately measure the quantity of released 40Ar in cases where Ar is an atmospheric constituent (e.g., Mars), the sample is first put into a chamber under high vacuum. The 40Arquantity, the concentration of K and the estimation of the ablated mass are the parameters needed to give the age of the rocks. The main uncertainties with this method are directly linked to the measures of the mass (typically some µg) and of the concentration of K by LIBS (up to 10%). Because the ablated mass is small compared to the mass of the sample, and because material is redeposited onto the sample after ablation, it is not possible to directly measure the ablated mass. Our current protocol measures the ablated volume and estimates the sample density to calculate ablated mass. The precision and accuracy of this method may be improved by using knowledge of the sample's geologic properties to predict its response to laser ablation, i.e., understanding whether natural samples have a predictable relationship between laser energy deposited and resultant ablation volume. In contrast to most previous studies of laser ablation, theoretical equations are not highly applicable. The reasons are numerous, but the most important are: a) geologic rocks are complex, polymineralic materials; b) the conditions of ablation are unusual (for example, variable vacuum pressure), and c) the ablation is made with hundreds of successive laser pulses. In this work, we aim to understand the effects that occur on LIBS spectra when a homogeneous rock or a mineral is ablated under high vacuum. Understanding these effects is important to define best practices for LIBS measurements and may lead to improved measurement (or possibly prediction) of the ablated volume. We will describe our laboratory approach and first results, and discuss its utility for situ absolute geochronology campaigns.

Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

PubMed Central

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

2011-01-01

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

Subcellular analysis by laser ablation electrospray ionization mass spectrometry

DOEpatents

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

2014-12-02

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

Improved Ablation Resistance of Silicone Rubber Composites by Introducing Montmorillonite and Silicon Carbide Whisker

PubMed Central

Zhang, Guangwu; Wang, Fuzhong; Huang, Zhixiong; Dai, Jing; Shi, Minxian

2016-01-01

Montmorillonite (MMT) was added to silicone rubber (SR) to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw) were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break of the composite increased after the addition of MMT. The ablation test results showed that MMT helped to form a covering layer by bonding with the silica and other components on the ablated surface. The linear and mass ablation rates exhibited decreases of 22.5% and 18.2%, respectively, in comparison to a control sample. After further incorporation of SiCw as the second filler, the resulting composites exhibited significantly higher tensile strength and ablation resistance, but not particularly lower elongation at break in comparison to the control sample. The SiCw/MMT fillers were beneficial in forming a dense and compact covering layer that delayed the heat and oxygen diffusion into the inner layers, which improved the ablation properties effectively. The remaining whiskers acted as a micro skeleton to maintain the composite’s char strength. Compared to the control sample, the linear and mass ablation rates of the composite after incorporating 6 phr SiCw and 10 phr MMT decreased by 59.2% and 43.6%, respectively. These experimental results showed that the fabricated composites exhibited outstanding mechanical properties and excellent ablation resistance. PMID:28773846

Ablation of hypertrophic septum using radiofrequency energy: an alternative for gradient reduction in patient with hypertrophic obstructive cardiomyopathy?

PubMed

Riedlbauchová, Lucie; Janoušek, Jan; Veselka, Josef

2013-06-01

Alcohol septal ablation and surgical myectomy represent accepted therapeutic options for treatment of symptomatic patients with hypertrophic obstructive cardiomyopathy. Long-term experience with radiofrequency ablation of arrhythmogenic substrates raised a question if this technique might be effective for left ventricular outflow tract (LVOT) gradient reduction. We report on a 63-year-old patient with recurrence of symptoms 1 year after alcohol septal ablation (ASA) leading originally to a significant reduction of both symptoms and gradient. Due to a new increase of gradient in the LVOT up to 200 mm Hg with corresponding worsening of symptoms and due to refusal of surgical myectomy by the patient, endocardial radiofrequency ablation of the septal hypertrophy (ERASH) was indicated. Radiofrequency ablation was performed in the LVOT using irrigated-tip ablation catheter; the target site was identified using intracardiac echocardiography and electroanatomical CARTO mapping. ERASH caused an immediate gradient reduction due to hypokinesis of the ablated septum. At 2-month follow-up exam, significant clinical improvement was observed, together with persistent gradient reduction assessed with Doppler echocardiography. Echocardiography and magnetic resonance revealed persistent septal hypokinesis and slight thinning of the ablated region. Septal ablation using radiofrequency energy may be a promising alternative or adjunct to the treatment of hypertrophic obstructive cardiomyopathy. Intracardiac echocardiography and electroanatomical CARTO mapping enable exact lesion placement and preservation of atrioventricular conduction.

Improved Ablation Resistance of Silicone Rubber Composites by Introducing Montmorillonite and Silicon Carbide Whisker.

PubMed

Zhang, Guangwu; Wang, Fuzhong; Huang, Zhixiong; Dai, Jing; Shi, Minxian

2016-08-24

Montmorillonite (MMT) was added to silicone rubber (SR) to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw) were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break of the composite increased after the addition of MMT. The ablation test results showed that MMT helped to form a covering layer by bonding with the silica and other components on the ablated surface. The linear and mass ablation rates exhibited decreases of 22.5% and 18.2%, respectively, in comparison to a control sample. After further incorporation of SiCw as the second filler, the resulting composites exhibited significantly higher tensile strength and ablation resistance, but not particularly lower elongation at break in comparison to the control sample. The SiCw/MMT fillers were beneficial in forming a dense and compact covering layer that delayed the heat and oxygen diffusion into the inner layers, which improved the ablation properties effectively. The remaining whiskers acted as a micro skeleton to maintain the composite's char strength. Compared to the control sample, the linear and mass ablation rates of the composite after incorporating 6 phr SiCw and 10 phr MMT decreased by 59.2% and 43.6%, respectively. These experimental results showed that the fabricated composites exhibited outstanding mechanical properties and excellent ablation resistance.

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

PubMed

Duan, Ya-Qi; Liang, Ping

2013-05-01

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

Naphthalene Planar Laser-Induced Fluorescence Imaging of Orion Multi-Purpose Crew Vehicle Heat Shield Ablation Products

NASA Astrophysics Data System (ADS)

Combs, Christopher S.; Clemens, Noel T.; Danehy, Paul M.

2013-11-01

The Orion Multi-Purpose Crew Vehicle (MPCV) calls for an ablative heat shield. In order to better design this heat shield and others that will undergo planetary entry, an improved understanding of the ablation process is required. Given that ablation is a multi-physics process involving heat and mass transfer, codes aiming to predict heat shield ablation are in need of experimental data pertaining to the turbulent transport of ablation products for validation. At The University of Texas at Austin, a technique is being developed that uses planar laser-induced fluorescence (PLIF) of a low-temperature sublimating ablator (naphthalene) to visualize the transport of ablation products in a supersonic flow. Since ablation at reentry temperatures can be difficult to recreate in a laboratory setting it is desirable to create a limited physics problem and simulate the ablation process at relatively low temperature conditions using naphthalene. A scaled Orion MPCV model with a solid naphthalene heat shield has been tested in a Mach 5 wind tunnel at various angles of attack in the current work. PLIF images have shown high concentrations of scalar in the capsule wake region, intermittent turbulent structures on the heat shield surface, and interesting details of the capsule shear layer structure. This work was supported by a NASA Office of the Chief Technologist's Space Technology Research Fellowship (NNX11AN55H).

[Ultrasound-guided microwave ablation with artificial pleural effusion for liver tumor adjacent to 
diaphragmatic dome].

PubMed

Tang, Tian; Gu, Shanzhi; Li, Guowen; Huang, Manping; Huang, Bin; Xiong, Zhengping

2017-02-28

To explore the value of ultrasound-guided microwave ablation with artificial pleural effusion for liver tumor adjacent to diaphragmatic dome.
 Methods: A total of 34 patients with liver tumors located at diaphragmatic dome in Hunan Provincial Tumor Hospital were recruited from January 2014 to October 2015. The number of lesions ≤3 or lesion diameter ≤5 cm was in line with the microwave ablation indications. B ultrasound-guided microwave ablation for the liver tumors was undertaken after the artificial pleural effusion being established. 3-4 weeks later after the microwave ablation, all patients were imaged with enhance CT or MRI. The effect of ablation and the complications were evaluated.
 Results: There were 49 lesions in 34 patients, including 30 cases (88.2%) of complete ablation (CA), 3 cases (8.8%) of partial ablation (PA) and one case with new lesions after ablation (2.9%). Thirty-four patients had (1 580±230.7) mL of pleural effusion volume, while one case had bloody pleural effusion. One case had a diaphragmatic thermal injury, and one case had a biliary tumor infection. All of them showed remission after symptomatic treatment. 
 Conclusion: Combination of ultrasound-guided microwave ablation with artificial pleural effusion is a safe and effective therapy for liver tumor adjacent to diaphragmatic dome.

Ablation enhancement of silicon by ultrashort double-pulse laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Xin; Shin, Yung C.

In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1 ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1 ps), the enhancement is due to the electron excitation by the first pulse.more » The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.« less

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

NASA Technical Reports Server (NTRS)

Milos, Frank S.; Chen, Yih-Kanq

2010-01-01

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

Evolution of the ablation region after magnetic resonance-guided high-intensity focused ultrasound ablation in a Vx2 tumor model.

PubMed

Wijlemans, Joost W; Deckers, Roel; van den Bosch, Maurice A A J; Seinstra, Beatrijs A; van Stralen, Marijn; van Diest, Paul J; Moonen, Chrit T W; Bartels, Lambertus W

2013-06-01

Volumetric magnetic resonance (MR)-guided high-intensity focused ultrasound (HIFU) is a completely noninvasive image-guided thermal ablation technique. Recently, there has been growing interest in the use of MR-HIFU for noninvasive ablation of malignant tumors. Of particular interest for noninvasive ablation of malignant tumors is reliable treatment monitoring and evaluation of response. At this point, there is limited evidence on the evolution of the ablation region after MR-HIFU treatment. The purpose of the present study was to comprehensively characterize the evolution of the ablation region after volumetric MR-HIFU ablation in a Vx2 tumor model using MR imaging, MR temperature data, and histological data. Vx2 tumors in the hind limb muscle of New Zealand White rabbits (n = 30) were ablated using a clinical MR-HIFU system. Twenty-four animals were available for analyses. Magnetic resonance imaging was performed before and immediately after ablation; MR temperature mapping was performed during the ablation. The animals were distributed over 7 groups with different follow-up lengths. Depending on the group, animals were reimaged and then killed on day 0, 1, 3, 7, 14, 21, or 28 after ablation. For all time points, the size of nonperfused areas (NPAs) on contrast-enhanced T1-weighted (CE-T1-w) images was compared with lethal thermal dose areas (ie, the tissue area that received a thermal dose of 240 equivalent minutes or greater [EM] at 43°C) and with the necrotic tissue areas on histology sections. The NPA on CE-T1-w imaging showed an increase in median size from 266 ± 148 to 392 ± 178 mm(2) during the first day and to 343 ± 170 mm(2) on day 3, followed by a gradual decrease to 113 ± 103 mm(2) on day 28. Immediately after ablation, the NPA was 1.6 ± 1.4 times larger than the area that received a thermal dose of 240 EM or greater in all animals. The median size of the necrotic area on histology was 1.7 ± 0.4 times larger than the NPA immediately after ablation. After 7 days, the size of the NPA was in agreement with the necrotic tissue area on histology (ratio, 1.0 ± 0.2). During the first 3 days after MR-HIFU ablation, the ablation region increases in size, after which it gradually decreases in size. The NPA on CE-T1-w imaging underestimates the extent of tissue necrosis on histology in the initial few days, but after 1 week, the NPA is reliable in delineating the necrotic tissue area. The 240-EM thermal dose limit underestimates the necrotic tissue area immediately after MR-HIFU ablation. Reliable treatment evaluation techniques are particularly important for noninvasive, image-guided tumor ablation. Our results indicate that CE-T1-w imaging is reliable for MR-HIFU treatment evaluation after 1 week.

Experimental setup for the laboratory investigation of micrometeoroid ablation using a dust accelerator.

PubMed

Thomas, Evan; Simolka, Jonas; DeLuca, Michael; Horányi, Mihály; Janches, Diego; Marshall, Robert A; Munsat, Tobin; Plane, John M C; Sternovsky, Zoltan

2017-03-01

A facility has been developed to simulate the ablation of micrometeoroids in laboratory conditions. An electrostatic dust accelerator is used to generate iron particles with velocities of 10-70 km/s. The particles are then introduced into a chamber pressurized with a target gas, where the pressure is adjustable between 0.01 and 0.5 Torr, and the particle partially or completely ablates over a short distance. An array of biased electrodes above and below the ablation path is used to collect the generated ions/electrons with a spatial resolution of 2.6 cm along the ablating particles' path, thus allowing the study of the spatiotemporal evolution of the process. For completely ablated particles, the total collected charge directly yields the ionization coefficient of a given dust material-target gas combination. The first results of this facility measured the ionization coefficient of iron atoms with N 2 , air, CO 2 , and He target gases for impact velocities >20 km/s, and are reported by Thomas et al. [Geophys. Res. Lett. 43, 3645 (2016)]. The ablation chamber is also equipped with four optical ports that allow for the detection of the light emitted by the ablating particle. A multichannel photomultiplier tube system is used to observe the ablation process with a spatial and temporal resolution of 0.64 cm and 90 ns. The preliminary results indicate that it is possible to calculate the velocity of the ablating particle from the optical observations, and in conjunction with the spatially resolved charge measurements allow for experimental validation of ablation models in future studies.

Experimental setup for the laboratory investigation of micrometeoroid ablation using a dust accelerator

NASA Astrophysics Data System (ADS)

Thomas, Evan; Simolka, Jonas; DeLuca, Michael; Horányi, Mihály; Janches, Diego; Marshall, Robert A.; Munsat, Tobin; Plane, John M. C.; Sternovsky, Zoltan

2017-03-01

A facility has been developed to simulate the ablation of micrometeoroids in laboratory conditions. An electrostatic dust accelerator is used to generate iron particles with velocities of 10-70 km/s. The particles are then introduced into a chamber pressurized with a target gas, where the pressure is adjustable between 0.01 and 0.5 Torr, and the particle partially or completely ablates over a short distance. An array of biased electrodes above and below the ablation path is used to collect the generated ions/electrons with a spatial resolution of 2.6 cm along the ablating particles' path, thus allowing the study of the spatiotemporal evolution of the process. For completely ablated particles, the total collected charge directly yields the ionization coefficient of a given dust material-target gas combination. The first results of this facility measured the ionization coefficient of iron atoms with N2, air, CO2, and He target gases for impact velocities >20 km/s, and are reported by Thomas et al. [Geophys. Res. Lett. 43, 3645 (2016)]. The ablation chamber is also equipped with four optical ports that allow for the detection of the light emitted by the ablating particle. A multichannel photomultiplier tube system is used to observe the ablation process with a spatial and temporal resolution of 0.64 cm and 90 ns. The preliminary results indicate that it is possible to calculate the velocity of the ablating particle from the optical observations, and in conjunction with the spatially resolved charge measurements allow for experimental validation of ablation models in future studies.

Attitudes toward Catheter Ablation for Atrial Fibrillation: A Nationwide Survey among Danish Cardiologists.

PubMed

Vadmann, Henrik; Pedersen, Susanne S; Nielsen, Jens Cosedis; Rodrigo-Domingo, Maria; Pehrson, Steen; Johannessen, Arne; Hansen, Peter Steen; Johansen, Jens Brock; Riahi, Sam

2015-10-01

Catheter ablation for atrial fibrillation (AF) is an important but expensive procedure that is the subject of some debate. Physicians' attitudes toward catheter ablation may influence promotion and patient acceptance. This is the first study to examine the attitudes of Danish cardiologists toward catheter ablation for AF, using a nationwide survey. We developed a purpose-designed questionnaire to evaluate attitudes toward catheter ablation for AF that was sent to all Danish cardiologists (n = 401; response n = 272 (67.8%)). There was no association between attitudes toward ablation and the experience or age of the cardiologist with respect to patients with recurrent AF episodes with a duration of <48 hours or >7 days and/or need for cardioversion. The majority (69%) expected a recurrence of AF after catheter ablation in more than 30% of the cases. For patients with persistent longstanding AF with a duration of >1 year, the attitude toward ablation for longstanding AF was more likely to be positive with increasing age (P < 0.01) and years of experience of the cardiologist (P = 0.002). Danish cardiologists generally have a positive attitude toward catheter ablation for AF, maintain up-to-date knowledge of the procedure, and are aware what information on ablation treatment should be given to patients with AF. The cardiologists had a positive attitude toward ablation for AF in patients with AF episodes <48 hours and patients with episodes >7 days, or those who needed medical/electrical conversion, but a more negative attitude toward treating longstanding AF patients. © 2015 Wiley Periodicals, Inc.

First beryllium capsule implosions on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kline, J. L.; Yi, S. A.; Simakov, A. N.

2016-05-15

The first indirect drive implosion experiments using Beryllium (Be) capsules at the National Ignition Facility confirm the superior ablation properties and elucidate possible Be-ablator issues such as hohlraum filling by ablator material. Since the 1990s, Be has been the preferred Inertial Confinement Fusion (ICF) ablator because of its higher mass ablation rate compared to that of carbon-based ablators. This enables ICF target designs with higher implosion velocities at lower radiation temperatures and improved hydrodynamic stability through greater ablative stabilization. Recent experiments to demonstrate the viability of Be ablator target designs measured the backscattered laser energy, capsule implosion velocity, core implosionmore » shape from self-emission, and in-flight capsule shape from backlit imaging. The laser backscatter is similar to that from comparable plastic (CH) targets under the same hohlraum conditions. Implosion velocity measurements from backlit streaked radiography show that laser energy coupling to the hohlraum wall is comparable to plastic ablators. The measured implosion shape indicates no significant reduction of laser energy from the inner laser cone beams reaching the hohlraum wall as compared with plastic and high-density carbon ablators. These results indicate that the high mass ablation rate for beryllium capsules does not significantly alter hohlraum energetics. In addition, these data, together with data for low fill-density hohlraum performance, indicate that laser power multipliers, required to reconcile simulations with experimental observations, are likely due to our limited understanding of the hohlraum rather than the capsule physics since similar multipliers are needed for both Be and CH capsules as seen in experiments.« less

Real-time rotational ICE imaging of the relationship of the ablation catheter tip and the esophagus during atrial fibrillation ablation.

PubMed

Helms, Adam; West, J Jason; Patel, Amit; Mounsey, J Paul; DiMarco, John P; Mangrum, J Michael; Ferguson, John D

2009-02-01

Atrioesophageal fistula is a rare complication of atrial fibrillation (AF) ablation that should be avoided. We investigated whether rotational intracardiac echocardiography (ICE) can help to minimize ablation close to the esophagus. We studied 41 patients referred for catheter ablation of refractory AF. A rotational ICE catheter was inserted into the (LA) to determine the location of the esophagus. The esophagus was identified to be either adjacent to the pulmonary vein (PV) ostium or to a cuff 2 cm outside the ostium. Circumferential ablation was performed at the PV ostium, with the exact ablation location determined by ICE. The relationship of the catheter tip to the esophagus was imaged during energy delivery, allowing interruption when respiration moved the tip closer to the esophagus. Out of 41 patients, the esophagus was seen near left-sided PVs in 32 and near right-sided PVs in three patients. The median distance from LA endocardium to esophagus was 2.2 mm (range, 1.4-6 mm). In 21 of 35 patients with a closely related esophagus, ablation over the esophagus was avoided by ablating either lateral or medial to the esophagus. In 14 patients, the esophagus could not be avoided, and risk was minimized by limiting lesion size. Significant movement (>10 mm) of the esophagus during the procedure occurred in 3/41 cases. Rotational ICE can accurately determine the distance of ablation sites from the esophagus. Real-time imaging of the relationship of the ablation catheter tip to the esophagus may reduce the incidence of esophageal injury.

Use of New Imaging CARTO® Segmentation Module Software to Facilitate Ablation of Ventricular Arrhythmias.

PubMed

Tovia-Brodie, Oholi; Belhassen, Bernard; Glick, Aharon; Shmilovich, Haim; Aviram, Galit; Rosso, Raphael; Michowitz, Yoav

2017-02-01

A new imaging software (CARTO® Segmentation Module, Biosense Webster) allows preprocedural 3-D reconstruction of all heart chambers based on cardiac CT. We describe our initial experience with the new module during ablation of ventricular arrhythmias. Eighteen consecutive patients with idiopathic ventricular arrhythmias or ischemic ventricular tachycardia (VT) were studied. In the latter group, a combined endocardial and epicardial ablation was performed. Of the 14 patients with idiopathic arrhythmias, 12 were ablated in the outflow tract (OT), 1 in the midseptal left ventricle, and 1 at the left posterior fascicular area; acute successful ablation was achieved in 11 (78.6%) patients. The procedure was discontinued due to close proximity of the arrhythmia origin to the coronary arteries (CA) in 2 patients. Acute successful uncomplicated ablation was achieved in all 4 patients with ischemic VT. During ablation in the coronary cusps commissures, the CARTO® Segmentation Module accurately defined the cusps anatomy. The precise anatomic location provided by the module assisted in successfully ablating when information from activation mapping was not optimal, by ablating at the opposite side of the cusps. In addition, by demonstrating the precise location of the CA, it allowed safe ablation of arrhythmias that originated in close proximity to the CA both in the OT area and the epicardium, eliminating the need for repeat angiography. The CARTO® Segmentation Module is useful for accurate definition of the exact anatomic location of ventricular arrhythmias and for safely ablating them especially in close proximity to the CA. © 2016 Wiley Periodicals, Inc.

Successful Repeat Catheter Ablation of Recurrent Longstanding Persistent Atrial Fibrillation With Rotor Elimination as the Procedural Endpoint: A Case Series.

PubMed

Sommer, Philipp; Kircher, Simon; Rolf, Sascha; John, Silke; Arya, Arash; Dinov, Borislav; Richter, Sergio; Bollmann, Andreas; Hindricks, Gerhard

2016-03-01

There remains a lack of consensus regarding the ideal ablation strategy for atrial fibrillation (AF), particularly in patients with persistent or longstanding persistent AF. Given increasing evidence from clinical imaging studies that rotors sustain AF, rotor elimination may be a desirable procedural endpoint. However, there is no description to date of the clinical outcomes using rotor elimination during ablation as the procedural endpoint. Moreover, a series of studies question whether procedural AF termination is a desirable endpoint for ablation after many forms of AF ablation. We report a single-center experience of rotor elimination during AF ablation using Focal Impulse and Rotor Mapping (FIRM), describing 20 consecutive patients with case descriptions of 3 patients with recurrent longstanding persistent AF after prior ablation. In all cases, endocardial mapping using a 64-electrode basket catheter was performed to identify rotors, which were eliminated using radiofrequency catheter ablation. After it was verified that all identified rotors were eliminated, standard ablation consisting of PV isolation was performed. Notably, persistent AF terminated in only 1/20 (5%) patients. However, after a follow-up of 6 months, single-procedure freedom from AF was 80% (16/20 patients) with only 1 patient on antiarrhythmic drugs. All three patients in the highlighted series are AF free despite the lack of acute procedural AF termination. Patients with persistent AF including those with unsuccessful prior ablation can be treated successfully by rotor targeted ablation, using the elimination of all rotors rather than acute AF termination as the procedural endpoint. © 2015 Wiley Periodicals, Inc.

ANALYSIS OF FACTORS AFFECTING OUTCOME OF ULTRASOUND-GUIDED RADIOFREQUENCY HEAT ABLATION FOR TREATMENT OF PRIMARY HYPERPARATHYROIDISM IN DOGS.

PubMed

Bucy, Daniel; Pollard, Rachel; Nelson, Richard

2017-01-01

Radiofrequency (RF) parathyroid ablation is a noninvasive treatment for hyperparathyroidism in dogs. There are no published data assessing factors associated with RF parathyroid ablation success or failure in order to guide patient selection and improve outcome. The purpose of this retrospective analytical study was to determine whether imaging findings, biochemical data, or concurrent diseases were associated with RF heat ablation treatment failure. For inclusion in the study, dogs must have had a clinical diagnosis of primary hyperparathyroidism, undergone cervical ultrasound and RF ablation of abnormal parathyroid tissue, and must have had at least 3 months of follow-up information available following the date of ultrasound-guided parathyroid ablation. Dogs were grouped based on those with recurrent or persistent hypercalcemia and those without recurrent or persistent hypercalcemia following therapy. Parathyroid nodule size, thyroid lobe size, nodule location, and presence of concurrent disease were recorded. Recurrence of hypercalcemia occurred in 9/32 dogs that had ablation of abnormal parathyroid tissue (28%) and one patient had persistent hypercalcemia (3%) following parathyroid ablation. Nodule width (P = 0.036), height (P = 0.028), and largest cross-sectional area (P = 0.023) were larger in dogs that had recurrent or persistent hypercalcemia following ablation. Hypothyroidism was more common in dogs with recurrent disease (P = 0.044). Radiofrequency ablation was successful in 22/32 (69%) dogs. Larger parathyroid nodule size and/or concurrent hypothyroidism were associated with treatment failure in dogs that underwent ultrasound-guided RF parathyroid nodule ablation. © 2016 American College of Veterinary Radiology.

Atrio-ventricular junction ablation and pacemaker treatment: a comparison between men and women.

PubMed

Carnlöf, Carina; Insulander, Per; Jensen-Urstad, Mats; Iwarzon, Marie; Gadler, Fredrik

2018-06-01

To explore sex differences regarding indication for atrio-ventricular junction ablation (AVJ), choice of pacing system, complications to pacemaker treatment, long-term outcome, and cause of death after AVJ ablation. 700 patients who had undergone AVJ ablation between January 1990 and December 2010 were included. Data were retrieved from the patients´ medical records and the Swedish Pacemaker and Implantable Cardioverter-Defibrillator Registry. Information about admission to hospital and cause of death was retrieved from the National Board of Health and Welfare. Mean follow-up was 90 ± 64 months. Indication for AVJ ablation, choice of pacing system, and outcome after AVJ ablation differed between the sexes. The men had more often permanent atrial fibrillation, p = .0001, and a VVIR pacemaker or cardiac resynchronization therapy (CRT) implanted prior to ablation, p = .0001. Heart failure was present in 44% of the men vs. 28% of the women, p = .0001. LVEF decreased slightly in the whole cohort after the AVJ ablation. There were no sex differences in complication rates due to the pacemaker/ICD treatment, p = .3 or mortality due to AVJ ablation. In this long-term follow-up in patients with atrial fibrillation treated with AVJ ablation and pacing, indication, choice of pacing system, and morbidity differed but there were no sex differences regarding survival or primary cause of death found. The main factor influencing survival was age at the time of ablation. Women less often received treatment with ICD and/or CRT when indication was present compared with men.

First beryllium capsule implosions on the National Ignition Facility

DOE PAGES

Kline, J. L.; Yi, S. A.; Simakov, A. N.; ...

2016-05-01

The first indirect drive implosion experiments using Beryllium (Be) capsules at the National Ignition Facility confirm the superior ablation properties and elucidate possible Be-ablator issues such as hohlraum filling by ablator material. Since the 1990s, Be has been the preferred Inertial Confinement Fusion (ICF) ablator because of its higher mass ablation rate compared to that of carbon-based ablators. This enables ICF target designs with higher implosion velocities at lower radiation temperatures and improved hydrodynamic stability through greater ablative stabilization. Recent experiments to demonstrate the viability of Be ablator target designs measured the backscattered laser energy, capsule implosion velocity, core implosionmore » shape from self-emission, and in-flight capsule shape from backlit imaging. The laser backscatter is similar to that from comparable plastic (CH) targets under the same hohlraum conditions. Implosion velocity measurements from backlit streaked radiography show that laser energy coupling to the hohlraum wall is comparable to plastic ablators. The measured implosion shape indicates no significant reduction of laser energy from the inner laser cone beams reaching the hohlraum wall as compared with plastic and high-density carbon ablators. These results indicate that the high mass ablation rate for beryllium capsules does not significantly alter hohlraum energetics. In addition, these data, together with data for low fill-density hohlraum performance, indicate that laser power multipliers, required to reconcile simulations with experimental observations, are likely due to our limited understanding of the hohlraum rather than the capsule physics since similar multipliers are needed for both Be and CH capsules as seen in experiments.« less

A comparative analysis of clinical outcomes and disposable costs of different catheter ablation methods for the treatment of atrioventricular nodal reentrant tachycardia.

PubMed

Berman, Adam E; Rivner, Harold; Chalkley, Robin; Heboyan, Vahé

2017-01-01

Catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) is a commonly performed electrophysiology (EP) procedure. Few data exist comparing conventional (CONV) versus novel ablation strategies from both clinical and direct cost perspectives. We sought to investigate the disposable costs and clinical outcomes associated with three different ablation methodologies used in the ablation of AVNRT. We performed a retrospective review of AVNRT ablations performed at Augusta University Medical Center from 2006 to 2014. A total of 183 patients were identified. Three different ablation techniques were compared: CONV manual radiofrequency (RF) (n=60), remote magnetic navigation (RMN)-guided RF (n=67), and cryoablation (CRYO) (n=56). Baseline demographics did not differ between the three groups except for a higher prevalence of cardiomyopathy in the RMN group ( p <0.01). The clinical end point of interest was recurrent AVNRT following the index ablation procedure. A significantly higher number of recurrent AVNRT cases occurred in the CRYO group as compared to CONV and RMN ( p =0.003; OR =7.75) groups. Cost-benefit analysis showed both CONV and RMN to be dominant compared to CRYO. Cost-minimization analysis demonstrated the least expensive ablation method to be CONV (mean disposable catheter cost = CONV US$2340; CRYO US$3515; RMN US$5190). Despite comparable clinical outcomes, the incremental cost of RMN over CONV averaged US$3094 per procedure. AVNRT ablation using either CONV or RMN techniques is equally effective and associated with lower AVNRT recurrence rates than CRYO. CONV ablation carries significant disposable cost savings as compared to RMN, despite similar efficacy.

Experimental Setup for the Laboratory Investigation of Micrometeoroid Ablation Using a Dust Accelerator

NASA Technical Reports Server (NTRS)

Thomas, Evan; Simolka, Jonas; DeLuca, Michael; Horanyi, Mihaly; Janches, Diego; Marshall, Robert A.; Munsat, Tobin; Plane, John M. C.; Sternovsky, Zoltan

2017-01-01

A facility has been developed to simulate the ablation of micrometeoroids in laboratory conditions. An electrostatic dust accelerator is used to generate iron particles with velocities of 10-70 kilometers. The particles are then introduced into a chamber pressurized with a target gas, where the pressure is adjustable between 0.01 and 0.5 Torr, and the particle partially or completely ablates over a short distance. An array of biased electrodes above and below the ablation path is used to collect the generated ions/electrons with a spatial resolution of 2.6 centimeters along the ablating particles path, thus allowing the study of the spatiotemporal evolution of the process. For completely ablated particles, the total collected charge directly yields the ionization coefficient of a given dust material-target gas combination. The first results of this facility measured the ionization coefficient of iron atoms with N2, air, CO2, and He target gases for impact velocities greater than 20 kilometers per second, and are reported by Thomas et al. The ablation chamber is also equipped with four optical ports that allow for the detection of the light emitted by the ablating particle. A multichannel photomultiplier tube system is used to observe the ablation process with a spatial and temporal resolution of 0.64 centimeters and 90 nanoseconds. The preliminary results indicate that it is possible to calculate the velocity of the ablating particle from the optical observations, and in conjunction with the spatially resolved charge measurements allow for experimental validation of ablation models in future studies.

Preclinical Assessment of a 980-nm Diode Laser Ablation System in a Large Animal Tumor Model

PubMed Central

Ahrar, Kamran; Gowda, Ashok; Javadi, Sanaz; Borne, Agatha; Fox, Matthew; McNichols, Roger; Ahrar, Judy U.; Stephens, Clifton; Stafford, R. Jason

2010-01-01

Purpose To characterize the performance of a 980-nm diode laser ablation system in an in vivo tumor model. Materials and Methods This study was approved by the Institutional Animal Care and Use Committee. The ablation system consisted of a 15-W, 980-nm diode laser, flexible diffusing tipped fiber optic, and 17-gauge internally cooled catheter. Ten immunosuppressed dogs were inoculated subcutaneously with canine transmissible venereal tumor fragments in eight dorsal locations. Laser ablations were performed at 79 sites where inoculations were successful (99%) using powers of 10 W, 12.5 W, and 15 W, with exposure times between 60 and 180 seconds. In 20 cases, multiple overlapping ablations were performed. After the dogs were euthanized, the tumors were harvested, sectioned along the applicator track, measured and photographed. Measurements of ablation zone were performed on gross specimen. Histopathology and viability staining was performed using hematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide hydrogen (NADH) staining. Results Gross pathology confirmed well-circumscribed ablation zone with sharp boundaries between thermally ablated tumor in the center surrounded by viable tumor tissue. When a single applicator was used, the greatest ablation diameters ranged from 12 mm at the lowest dose (10 W, 60 sec) to 26 mm at the highest dose (15 W, 180 sec). Multiple applicators created ablation zones of up to 42 mm in greatest diameter (with the lasers operating at 15 W for 120 sec). Conclusions The new 980-nm diode laser and internally cooled applicator effectively creates large ellipsoid thermal ablations in less than 3 minutes. PMID:20346883

Varicose vein - noninvasive treatment

MedlinePlus

Sclerotherapy; Laser therapy - varicose veins; Radiofrequency vein ablation; Endovenous thermal ablation; Ambulatory phlebectomy; Transilluminated power phlebotomy; Endovenous laser ablation; Varicose vein therapy

Fractional ablative laser skin resurfacing: a review.

PubMed

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

2011-12-01

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

Experimental measurement of ablation effects in plasma armature railguns

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1986-01-01

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

Experimental measurement of ablation effects in plasma armature railguns

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1986-11-01

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

Ablation behaviors of carbon reinforced polymer composites by laser of different operation modes

NASA Astrophysics Data System (ADS)

Wu, Chen-Wu; Wu, Xian-Qian; Huang, Chen-Guang

2015-10-01

Laser ablation mechanism of Carbon Fiber Reinforced Polymer (CFRP) composite is of critical meaning for the laser machining process. The ablation behaviors are investigated on the CFRP laminates subject to continuous wave, long duration pulsed wave and short duration pulsed wave lasers. Distinctive ablation phenomena have been observed and the effects of laser operation modes are discussed. The typical temperature patterns resulted from laser irradiation are computed by finite element analysis and thereby the different ablation mechanisms are interpreted.

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

Tran, D. T.; Mori, K.

2017-02-01

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

In-situ tomographic observation of tissue surface during laser ablation

NASA Astrophysics Data System (ADS)

Haruna, Masamitsu; Konoshita, Ryuh; Ohmi, Masato; Kunizawa, Naomi; Miyachi, Mayumi

2001-07-01

In laser ablation of tissues, tomography of the tissue surface is necessary for measurement of the crater depth and observation of damage of the surrounding tissue. We demonstrate here OCT images of craters made by UV laser ablation of different tissues. The maximum depth of a crater is found among several OCT images, and then the ablation rate is determined. The conventional OCT of the spatial resolution of 15 μm was used in our experiment, but OCT of the resolution of the order of 1 μm is required because the ablation rate is usually a few microns per pulse. Such a high-resolution OCT is also demonstrated in this paper, where the light source is a halogen lamp. Combination of laser ablation and OCT will lead to in situ tomographic observation of tissue surface during laser ablation, which should allow us to develop new laser surgeries.

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

PubMed

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

2017-02-01

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

Rear-side picosecond laser ablation of indium tin oxide micro-grooves

NASA Astrophysics Data System (ADS)

Liu, Peng; Wang, Wenjun; Mei, Xuesong; Liu, Bin; Zhao, Wanqin

2015-06-01

A comparative study of the fabrication of micro-grooves in indium tin oxide films by picosecond laser ablation for application in thin film solar cells is presented, evaluating the variation of different process parameters. Compared with traditional front-side ablation, rear-side ablation results in thinner grooves with varying laser power at a certain scan speed. In particular, and in contrast to front-side ablation, the width of the micro-grooves remains unchanged when the scan speed was changed. Thus, the micro-groove quality can be optimized by adjusting the scan speed while the groove width would not be affected. Furthermore, high-quality micro-grooves with ripple free surfaces and steep sidewalls could only be achieved when applying rear-side ablation. Finally, the formation mechanism of micro-cracks on the groove rims during rear-side ablation is analyzed and the cracks can be almost entirely eliminated by an optimization of the scan speed.

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

PubMed

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

PubMed Central

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. PMID:24298282

Influence of the Liquid on Femtosecond Laser Ablation of Iron

NASA Astrophysics Data System (ADS)

Kanitz, A.; Hoppius, J. S.; Gurevich, E. L.; Ostendorf, A.

Ultrashort pulse laser ablation has become a very important industrial method for highly precise material removal ranging from sensitive thin film processing to drilling and cutting of metals. Over the last decade, a new method to produce pure nanoparticles emerged from this technique: Pulsed Laser Ablation in Liquids (PLAL). By this method, the ablation of material by a laser beam is used to generate a metal vapor within the liquid in order to obtain nanoparticles from its recondensation process. It is well known that the liquid significantly alters the ablation properties of the substrate, in our case iron. For example, the ablation rate and crater morphology differ depending on the used liquid. We present our studies on the efficiency and quality of ablated grooves in water, methanol, acetone, ethanol and toluene. The produced grooves are investigated by means of white-light interferometry, EDX and SEM.

Effects of pulse durations and environments on femtosecond laser ablation of stainless steel

NASA Astrophysics Data System (ADS)

Xu, Shizhen; Ding, Renjie; Yao, Caizhen; Liu, Hao; Wan, Yi; Wang, Jingxuan; Ye, Yayun; Yuan, Xiaodong

2018-04-01

The influence of pulse durations (35fs and 260 fs) and environments (air and vacuum) on the laser-induced damage thresholds (LIDTs) and ablation rates of 304 stainless steel were studied. Two distinct ablation regimes were obtained from the ablation rate curves. At low fluence regime, the ablation rates were similar in spite of the differences of pulse durations and experiment environments. At high fluence regime, the ablation rates of 35 fs pulse duration in vacuum were obviously higher than others. The ablation craters showed smooth edges, moth-eye such as structures, and laser-induced periodic surface structures (LIPSSs). At a fixed fluence, the periods of LIPSSs decreased monotonously in their mean spatial period between 700 nm (5 pulses) and 540 nm (200 pulses) with the increase of pulse numbers in air with 35 fs pulse duration. The formation mechanisms of moth-eye like structures and LIPSSs were also discussed.

Catheter ablation in patients with persistent atrial fibrillation

PubMed Central

Kirchhof, Paulus; Calkins, Hugh

2017-01-01

Catheter ablation is increasingly offered to patients who suffer from symptoms due to atrial fibrillation (AF), based on a growing body of evidence illustrating its efficacy compared with antiarrhythmic drug therapy. Approximately one-third of AF ablation procedures are currently performed in patients with persistent or long-standing persistent AF. Here, we review the available information to guide catheter ablation in these more chronic forms of AF. We identify the following principles: Our clinical ability to discriminate paroxysmal and persistent AF is limited. Pulmonary vein isolation is a reasonable and effective first approach for catheter ablation of persistent AF. Other ablation strategies are being developed and need to be properly evaluated in controlled, multicentre trials. Treatment of concomitant conditions promoting recurrent AF by life style interventions and medical therapy should be a routine adjunct to catheter ablation of persistent AF. Early rhythm control therapy has a biological rationale and trials evaluating its value are underway. There is a clear need to generate more evidence for the best approach to ablation of persistent AF beyond pulmonary vein isolation in the form of adequately powered controlled multi-centre trials. PMID:27389907

Morphology and mechanisms of picosecond ablation of metal films on fused silica substrates

NASA Astrophysics Data System (ADS)

Bass, Isaac L.; Negres, Raluca A.; Stanion, Ken; Guss, Gabe; Keller, Wesley J.; Matthews, Manyalibo J.; Rubenchik, Alexander M.; Yoo, Jae Hyuck; Bude, Jeffrey D.

2016-12-01

The ablation of magnetron sputtered metal films on fused silica substrates by a 1053 nm, picosecond class laser was studied as part of a demonstration of its use for in-situ characterization of the laser spot under conditions commonly used at the sample plane for laser machining and damage studies. Film thicknesses were 60 and 120 nm. Depth profiles and SEM images of the ablation sites revealed several striking and unexpected features distinct from those typically observed for ablation of bulk metals. Very sharp thresholds were observed for both partial and complete ablation of the films. Partial film ablation was largely independent of laser fluence with a surface smoothness comparable to that of the unablated surface. Clear evidence of material displacement was seen at the boundary for complete film ablation. These features were common to a number of different metal films including Inconel on commercial neutral density filters, stainless steel, and aluminum. We will present data showing the morphology of the ablation sites on these films as well as a model of the possible physical mechanisms producing the unique features observed.

Cartilage ablation studies using mid-IR free electron laser

NASA Astrophysics Data System (ADS)

Youn, Jong-In; Peavy, George M.; Venugopalan, Vasan

2005-04-01

The ablation rate of articular cartilage and fibrocartilage (meniscus), were quantified to examine wavelength and tissue-composition dependence of ablation efficiency for selected mid-infrared wavelengths. The wavelengths tested were 2.9 um (water dominant absorption), 6.1 (protein and water absorption) and 6.45 um (protein dominant absorption) generated by the Free Electron Laser (FEL) at Vanderbilt University. The measurement of tissue mass removal using a microbalance during laser ablation was conducted to determine the ablation rates of cartilage. The technique can be accurate over methods such as profilometer and histology sectioning where tissue surface and the crater morphology may be affected by tissue processing. The ablation efficiency was found to be dependent upon the wavelength. Both articular cartilage and meniscus (fibrocartilage) ablations at 6.1 um were more efficient than those at the other wavelengths evaluated. We observed the lowest ablation efficiency of both types of cartilage with the 6.45 um wavelength, possibly due to the reduction in water absorption at this wavelength in comparison to the other wavelengths that were evaluated.

Emerging needle ablation technology in urology.

PubMed

Leveillee, Raymond J; Pease, Karli; Salas, Nelson

2014-01-01

Thermal ablation of urologic tumors in the form of freezing (cryoablation) and heating (radiofrequency ablation) have been utilized successfully to treat and ablate soft tissue tumors for over 15 years. Multiple studies have demonstrated efficacy nearing that of extirpative surgery for certain urologic conditions. There are technical limitations to their speed and safety profile because of the physical limits of thermal diffusion. Recently, there has been a desire to investigate other forms of energy in an effort to circumvent the limitations of cryoblation and radiofrequency ablation. This review will focus on three relatively new energy applications as they pertain to tissue ablation: microwave, irreversible electroporation, and water vapor. High-intensity-focused ultrasound nor interstitial lasers are discussed, as there have been no recently published updates. Needle and probe-based ablative treatments will continue to play an important role. As three-dimensional imaging workstations move from the advanced radiologic interventional suite to the operating room, surgeons will likely still play a pivotal role in the +-application of these probe ablative devices. It is essential that the surgeon understands the fundamentals of these devices in order to optimize their application.

Primary malignant tumours of the bony pelvis: US-guided high intensity focused ultrasound ablation.

PubMed

Wang, Yang; Wang, Wei; Tang, Jie

2013-11-01

The aim of this review is to evaluate the value of ultrasound (US)-guided high intensity focused ultrasound (HIFU) ablation in the treatment of primary malignant tumours of the bony pelvis. Eleven patients with primary malignant tumours of the bony pelvis received US-guided HIFU ablation. The maximum tumour size ranged from 5.6 to 25.0 cm (median 10.5 cm). Treatment was curative in four patients and palliative in seven patients. During follow-up, the effectiveness of HIFU ablation was assessed by contrast-enhanced magnetic resonance (MR). Significant coagulative necrosis was obtained in all patients after scheduled HIFU ablations; the volume ablation ratio was 86.7% ± 12.5% (range 65-100%). Complete tumour necrosis was achieved in all patients receiving curative HIFU ablation. No major complications were encountered. No patients died of local tumour progression during follow-up. US-guided HIFU ablation may be a safe and effective minimally invasive technique for the local treatment of primary malignant tumours of the bony pelvis.

Nifurpirinol: A more potent and reliable substrate compared to metronidazole for nitroreductase-mediated cell ablations.

PubMed

Bergemann, David; Massoz, Laura; Bourdouxhe, Jordane; Carril Pardo, Claudio A; Voz, Marianne L; Peers, Bernard; Manfroid, Isabelle

2018-04-17

The zebrafish is a popular animal model with well-known regenerative capabilities. To study regeneration in this fish, the nitroreductase/metronidazole-mediated system is widely used for targeted ablation of various cell types. Nevertheless, we highlight here some variability in ablation efficiencies with the metronidazole prodrug that led us to search for a more efficient and reliable compound. Herein, we present nifurpirinol, another nitroaromatic antibiotic, as a more potent prodrug compared to metronidazole to trigger cell-ablation in nitroreductase expressing transgenic models. We show that nifurpirinol induces robust and reliable ablations at concentrations 2,000 fold lower than metronidazole and three times below its own toxic concentration. We confirmed the efficiency of nifurpirinol in triggering massive ablation of three different cell types: the pancreatic beta cells, osteoblasts, and dopaminergic neurons. Our results identify nifurpirinol as a very potent prodrug for the nitroreductase-mediated ablation system and suggest that its use could be extended to many other cell types, especially if difficult to ablate, or when combined pharmacological treatments are desired. © 2018 by the Wound Healing Society.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Setup for functional cell ablation with lasers: coupling of a laser to a microscope.

PubMed

Sweeney, Sean T; Hidalgo, Alicia; de Belle, J Steven; Keshishian, Haig

2012-06-01

The selective removal of cells by ablation is a powerful tool in the study of eukaryotic developmental biology, providing much information about their origin, fate, or function in the developing organism. In Drosophila, three main methods have been used to ablate cells: chemical, genetic, and laser ablation. Each method has its own applicability with regard to developmental stage and the cells to be ablated, and its own limitations. The primary advantage of laser-based ablation is the flexibility provided by the method: The operations can be performed in any cell pattern and at any time in development. Laser-based techniques permit manipulation of structures within cells, even to the molecular level. They can also be used for gene activation. However, laser ablation can be expensive, labor-intensive, and time-consuming. Although live cells can be difficult to image in Drosophila embryos, the use of vital fluorescent imaging methods has made laser-mediated cell manipulation methods more appealing; the methods are relatively straightforward. This article provides the information necessary for setting up and using a laser microscope for lasesr ablation studies.

Innovative approach for in-vivo ablation validation on multimodal images

NASA Astrophysics Data System (ADS)

Shahin, O.; Karagkounis, G.; Carnegie, D.; Schlaefer, A.; Boctor, E.

2014-03-01

Radiofrequency ablation (RFA) is an important therapeutic procedure for small hepatic tumors. To make sure that the target tumor is effectively treated, RFA monitoring is essential. While several imaging modalities can observe the ablation procedure, it is not clear how ablated lesions on the images correspond to actual necroses. This uncertainty contributes to the high local recurrence rates (up to 55%) after radiofrequency ablative therapy. This study investigates a novel approach to correlate images of ablated lesions with actual necroses. We mapped both intraoperative images of the lesion and a slice through the actual necrosis in a common reference frame. An electromagnetic tracking system was used to accurately match lesion slices from different imaging modalities. To minimize the liver deformation effect, the tracking reference frame was defined inside the tissue by anchoring an electromagnetic sensor adjacent to the lesion. A validation test was performed using a phantom and proved that the end-to-end accuracy of the approach was within 2mm. In an in-vivo experiment, intraoperative magnetic resonance imaging (MRI) and ultrasound (US) ablation images were correlated to gross and histopathology. The results indicate that the proposed method can accurately correlate invivo ablations on different modalities. Ultimately, this will improve the interpretation of the ablation monitoring and reduce the recurrence rates associated with RFA.

Water content contribution in calculus phantom ablation during Q-switched Tm:YAG laser lithotripsy.

PubMed

Zhang, Jian J; Rajabhandharaks, Danop; Xuan, Jason Rongwei; Wang, Hui; Chia, Ray W J; Hasenberg, Tom; Kang, Hyun Wook

2015-01-01

Q-switched (QS) Tm:YAG laser ablation mechanisms on urinary calculi are still unclear to researchers. Here, dependence of water content in calculus phantom on calculus ablation performance was investigated. White gypsum cement was used as a calculus phantom model. The calculus phantoms were ablated by a total 3-J laser pulse exposure (20 mJ, 100 Hz, 1.5 s) and contact mode with N=15 sample size. Ablation volume was obtained on average 0.079, 0.122, and 0.391  mm3 in dry calculus in air, wet calculus in air, and wet calculus in-water groups, respectively. There were three proposed ablation mechanisms that could explain the effect of water content in calculus phantom on calculus ablation performance, including shock wave due to laser pulse injection and bubble collapse, spallation, and microexplosion. Increased absorption coefficient of wet calculus can cause stronger spallation process compared with that caused by dry calculus; as a result, higher calculus ablation was observed in both wet calculus in air and wet calculus in water. The test result also indicates that the shock waves generated by short laser pulse under the in-water condition have great impact on the ablation volume by Tm:YAG QS laser.

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

PubMed

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.

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

PubMed Central

2017-01-01

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

Optical aberrations induced by subclinical decentrations of the ablation pattern

NASA Astrophysics Data System (ADS)

Mrochen, Michael; Kaemmerer, Maik; Riedel, Peter; Mierdel, Peter; Krinke, Hans-Eberhard; Seiler, Theo

2000-06-01

Purpose: The aim of this work was to study the effect of currently used ablation profiles along with eccentric ablations on the increase of higher order aberrations observed after PRK. Material and Methods: The optical aberrations of 10 eyes were tested before and after PRK. Refractive surgery was performed using a ArF-excimer laser system. In all cases, the ablation zone was 6 mm or larger. The spherical equivalent of the correction was ranging from -2.5 D to -6.0 D. The measured wavefront error was compared to numerical simulations done with the reduced eye model and currently used ablation profiles as well as compared with experimental results obtained from ablation on PMMA balls. Results: The aberration measurements result in a considerable change of the spherical- and coma-like wavefront errors. This result was in good correlation with the numerical simulations and the experimental results. Furthermore, it has been derived that the major contribution on the induced higher order aberrations are a result of the small decentration (less than 1.0 mm) of the ablation zone. Conclusions: Higher order spherical- and coma-like aberrations after PRK are mainly determined by the decentration of the ablation zone during laser refractive surgery. However, future laser systems should use efficient eye-tracking systems and aspherical ablation profiles to overcome this problem.

Experimental Evaluation of the Heat Sink Effect in Hepatic Microwave Ablation.

PubMed

Ringe, Kristina I; Lutat, Carolin; Rieder, Christian; Schenk, Andrea; Wacker, Frank; Raatschen, Hans-Juergen

2015-01-01

To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape. 108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn's multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle. Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15 mm distance to the antenna (p<0.05). At a flow rate of 700 ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15 mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively. Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15 mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels.

Laparoscopic microwave thermosphere ablation of malignant liver tumors: an initial clinical evaluation.

PubMed

Berber, Eren

2016-02-01

Microwave ablation (MWA) has been recently recognized as a technology to overcome the limitations of radiofrequency ablation. The aim of the current study was to evaluate the safety and efficacy of a new 2.45-GHz thermosphere MWA system in the treatment of malignant liver tumors. This was a prospective IRB-approved study of 18 patients with malignant liver tumors treated with MWA within a 3-month time period. Tumor sizes and response to MWA were obtained from triphasic liver CT scans done before and after MWA. The ablation zones were assessed for complete tumor response and spherical geometry. There were a total of 18 patients with an average of three tumors measuring 1.4 cm (range 0.2-4). Ablations were performed laparoscopically in all, but three patients who underwent combined liver resection. A single ablation was created in 72% and overlapping ablations in 28% of lesions. Total ablation time per patient was 15.6 ± 1.9 min. There was no morbidity or mortality. At 2-week CT scans, there was 100% tumor destruction, with no residual lesions. Roundness indices A, B and transverse were 1.1, 0.9 and 0.9, respectively, confirming the spherical nature of ablation zones. To the best of our knowledge, this is the first report of a new thermosphere MWA technology in the laparoscopic treatment of malignant liver tumors. The results demonstrate the safety of the technology, with satisfactory spherical ablation zones seen on post-procedural CT scans.

Management of ventricular tachycardia in the ablation era: results of the European Heart Rhythm Association Survey.

PubMed

Tilz, Roland Richard; Lenarczyk, Radoslaw; Scherr, Daniel; Haugaa, Kristina Herman; Iliodromitis, Konstantinos; Pürerfellner, Helmut; Kiliszek, Marek; Dagres, Nikolaos

2018-01-01

Patients with sustained ventricular tachycardia (VT) are at risk of sudden death. Treatment options for VT include antiarrhythmic drug therapy, insertion of an implantable cardioverter-defibrillator, and catheter ablation. Evidence on indications for VT ablation, timing, ablation strategies, and periprocedural management is sparse. The aim of this European Heart Rhythm Association (EHRA) survey was to evaluate clinical practice regarding management of VT among the European countries. An electronic questionnaire was sent to members of the EHRA Electrophysiology Research Network. Responses were received from 88 centres in 12 countries. The results have shown that management of VTs is very heterogeneous across the participating centres. Indications, periprocedural management, and ablation strategies vary substantially. This EP Wire survey has revealed that catheter ablation is the first-line therapy for the treatment of recurrent monomorphic stable VT in patients without structural heart disease as well as in patients with ischaemic cardiomyopathy and impaired left ventricular ejection fraction in the majority of centres. Furthermore, in patients with ischaemic cardiomyopathy and the first episode of monomorphic VT, most centres (62.0%) performed catheter ablation. On the contrary, in patients with non-ischaemic cardiomyopathy, amiodarone (41.4%) and catheter ablation (37.1%) are used in a very similar proportion. Ablation strategies, endpoints, and post-ablation antithrombotic management vary substantially among European centres. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Discrete prepotential as an indicator of successful ablation in patients with coronary cusp ventricular arrhythmia.

PubMed

Hachiya, Hitoshi; Yamauchi, Yasuteru; Iesaka, Yoshito; Yagishita, Atsuhiko; Sasaki, Takeshi; Higuchi, Koji; Kawabata, Mihoko; Sugiyama, Koji; Tanaka, Yasuaki; Kusa, Shigeki; Nakamura, Hiroaki; Miyazaki, Shinsuke; Taniguchi, Hiroshi; Isobe, Mitsuaki; Hirao, Kenzo

2013-10-01

Although coronary cusp (CC) ventricular arrhythmia (VA) can be treated by catheter ablation, reliable indicators of successful ablation sites have not been fully identified. This study comprised 392 patients undergoing radiofrequency catheter ablation for outflow tract-VA at 3 institutions from January 2007 to August 2012. The successful ablation site was on the left CC or right CC in 35 (8.9%) of the 392 patients. In 9 (26%) of these 35 patients, a discrete prepotential was recognized, 5 of whom had left CC-VAs and 4 of whom had right CC-VAs. Radiofrequency catheter ablation was successful at the site of the prepotential in all 9 of these patients. The duration of the isoelectric line between the end of the discrete prepotential and the onset of the ventricular electrogram was 27±13 ms. The time from onset of the discrete prepotential at the successful ablation site on the CC to the QRS onset (activation time) was 69±20 ms (range, 50-98 ms). Pace mapping was graded as excellent at the successful ablation site in only 1 patient. No discrete prepotential was recorded in any successful right outflow tract-VA ablation case in this study. A discrete prepotential was seen in 9 (26%) of 35 patients with CC-VA. In left and right CC-VA, the site of a discrete prepotential with ≥50 ms activation time may indicate a successful ablation site.

Recent Advances in Tumor Ablation for Hepatocellular Carcinoma

PubMed Central

Kang, Tae Wook; Rhim, Hyunchul

2015-01-01

Image-guided tumor ablation for early stage hepatocellular carcinoma (HCC) is an accepted non-surgical treatment that provides excellent local tumor control and favorable survival benefit. This review summarizes the recent advances in tumor ablation for HCC. Diagnostic imaging and molecular biology of HCC has recently undergone marked improvements. Second-generation ultrasonography (US) contrast agents, new computed tomography (CT) techniques, and liver-specific contrast agents for magnetic resonance imaging (MRI) have enabled the early detection of smaller and inconspicuous HCC lesions. Various imaging-guidance tools that incorporate imaging-fusion between real-time US and CT/MRI, that are now common for percutaneous tumor ablation, have increased operator confidence in the accurate targeting of technically difficult tumors. In addition to radiofrequency ablation (RFA), various therapeutic modalities including microwave ablation, irreversible electroporation, and high-intensity focused ultrasound ablation have attracted attention as alternative energy sources for effective locoregional treatment of HCC. In addition, combined treatment with RFA and chemoembolization or molecular agents may be able to overcome the limitation of advanced or large tumors. Finally, understanding of the biological mechanisms and advances in therapy associated with tumor ablation will be important for successful tumor control. All these advances in tumor ablation for HCC will result in significant improvement in the prognosis of HCC patients. In this review, we primarily focus on recent advances in molecular tumor biology, diagnosis, imaging-guidance tools, and therapeutic modalities, and refer to the current status and future perspectives for tumor ablation for HCC. PMID:26674766

Pneumothorax as a complication of percutaneous radiofrequency ablation for lung neoplasms.

PubMed

Yamagami, Takuji; Kato, Takeharu; Hirota, Tatsuya; Yoshimatsu, Rika; Matsumoto, Tomohiro; Nishimura, Tsunehiko

2006-10-01

The present study was performed to determine the frequency of the complication of pneumothorax after radiofrequency (RF) ablation for lung neoplasms and risk factors affecting such pneumothoraces. The study was based on 129 consecutive sessions of percutaneous RF ablation of lung neoplasms under real-time computed tomographic fluoroscopic guidance performed in a single institution between May 2003 and November 2005 in 41 patients (17 women, 24 men; mean age, 63 years; age range, 29-82 y). Correlation was determined between the incidence of pneumothorax after RF ablation and multiple factors: sex, age, presence of emphysema, lesion size, lesion depth, contact of tumor with pleura, number of punctures, maximum power of RF generator, period of ablation, tissue temperature at the end of the RF ablation session, and patient position during the procedure. Management of each case of iatrogenic pneumothorax was reviewed. Pneumothorax after RF ablation occurred in 38 of 129 RF ablation sessions (29.5%). Fourteen of the 38 cases were treated by manual aspiration, and 24 were simply observed. In five cases (3.9%), chest tube placement was required as therapy for pneumothorax. The risk of pneumothorax was significantly increased in patients with pulmonary emphysema. The frequency of pneumothorax after RF ablation in our experience is similar to the frequency of pneumothorax after lung biopsy reported in the literature. Various conditions for RF ablation did not influence the incidence of pneumothorax. Emphysema was the only individual factor that correlated significantly with the development of iatrogenic pneumothorax.

1.0 T open-configuration magnetic resonance-guided microwave ablation of pig livers in real time

PubMed Central

Dong, Jun; Zhang, Liang; Li, Wang; Mao, Siyue; Wang, Yiqi; Wang, Deling; Shen, Lujun; Dong, Annan; Wu, Peihong

2015-01-01

The current fastest frame rate of each single image slice in MR-guided ablation is 1.3 seconds, which means delayed imaging for human at an average reaction time: 0.33 seconds. The delayed imaging greatly limits the accuracy of puncture and ablation, and results in puncture injury or incomplete ablation. To overcome delayed imaging and obtain real-time imaging, the study was performed using a 1.0-T whole-body open configuration MR scanner in the livers of 10 Wuzhishan pigs. A respiratory-triggered liver matrix array was explored to guide and monitor microwave ablation in real-time. We successfully performed the entire ablation procedure under MR real-time guidance at 0.202 s, the fastest frame rate for each single image slice. The puncture time ranged from 23 min to 3 min. For the pigs, the mean puncture time was shorted to 4.75 minutes and the mean ablation time was 11.25 minutes at power 70 W. The mean length and widths were 4.62 ± 0.24 cm and 2.64 ± 0.13 cm, respectively. No complications or ablation related deaths during or after ablation were observed. In the current study, MR is able to guide microwave ablation like ultrasound in real-time guidance showing great potential for the treatment of liver tumors. PMID:26315365

A comparison of the DPSS UV laser ablation characteristic of 1024 and H10F WC-Co

NASA Astrophysics Data System (ADS)

See, Tian Long; Chantzis, Dimitrios; Royer, Raphael; Metsios, Ioannis; Antar, Mohammad; Marimuthu, Sundar

2017-07-01

An investigation on ablation characteristics of 1024 and H10F cobalt cemented tungsten carbide (WC-Co) with a DPSS nanosecond UV laser (50 ns pulse width, 355 nm wavelength, 90 W average power and 10 kHz repetition rate) is presented. The ablation characteristic parameters such as ablation threshold, incubation effect and optical penetration depth were evaluated based on the spot ablation diameter and depth. It was observed that the ablation threshold is significantly influenced by the number of pulses (NOP) and it decreases with increase NOP which is attributed to the incubation effect. Only one ablation region is observed at low laser fluence and an additional molten ablation region is observed at high laser fluence accompanied with cracks. The cracks formation is due to the thermal induced stress and changes in WC microstructure during laser beam irradiation. The crack depth is proportional to the thickness of the molten WC region. The ablation threshold of 1024 WC-Co and H10F WC-Co were found to be Fth1 =4.32 J/cm2 and Fth1 =4.26 J/cm2 respectively. The difference in chemical composition has insignificant effect on the ablation threshold value of the material. The incubation factor and optical penetration depth values of 1024 WC-Co and H10F WC-Co were found to be ξ=0.73, α-1 =411 nm and ξ=0.75, α-1 =397 nm respectively.

Real-Time MRI-Guided Cardiac Cryo-Ablation: A Feasibility Study.

PubMed

Kholmovski, Eugene G; Coulombe, Nicolas; Silvernagel, Joshua; Angel, Nathan; Parker, Dennis; Macleod, Rob; Marrouche, Nassir; Ranjan, Ravi

2016-05-01

MRI-based ablation provides an attractive capability of seeing ablation-related tissue changes in real time. Here we describe a real-time MRI-based cardiac cryo-ablation system. Studies were performed in canine model (n = 4) using MR-compatible cryo-ablation devices built for animal use: focal cryo-catheter with 8 mm tip and 28 mm diameter cryo-balloon. The main steps of MRI-guided cardiac cryo-ablation procedure (real-time navigation, confirmation of tip-tissue contact, confirmation of vessel occlusion, real-time monitoring of a freeze zone formation, and intra-procedural assessment of lesions) were validated in a 3 Tesla clinical MRI scanner. The MRI compatible cryo-devices were advanced to the right atrium (RA) and right ventricle (RV) and their position was confirmed by real-time MRI. Specifically, contact between catheter tip and myocardium and occlusion of superior vena cava (SVC) by the balloon was visually validated. Focal cryo-lesions were created in the RV septum. Circumferential ablation of SVC-RA junction with no gaps was achieved using the cryo-balloon. Real-time visualization of freeze zone formation was achieved in all studies when lesions were successfully created. The ablations and presence of collateral damage were confirmed by T1-weighted and late gadolinium enhancement MRI and gross pathological examination. This study confirms the feasibility of a MRI-based cryo-ablation system in performing cardiac ablation procedures. The system allows real-time catheter navigation, confirmation of catheter tip-tissue contact, validation of vessel occlusion by cryo-balloon, real-time monitoring of a freeze zone formation, and intra-procedural assessment of ablations including collateral damage. © 2016 Wiley Periodicals, Inc.

Treatment planning for prostate focal laser ablation in the face of needle placement uncertainty

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cepek, Jeremy, E-mail: jcepek@robarts.ca; Fenster, Aaron; Lindner, Uri

2014-01-15

Purpose: To study the effect of needle placement uncertainty on the expected probability of achieving complete focal target destruction in focal laser ablation (FLA) of prostate cancer. Methods: Using a simplified model of prostate cancer focal target, and focal laser ablation region shapes, Monte Carlo simulations of needle placement error were performed to estimate the probability of completely ablating a region of target tissue. Results: Graphs of the probability of complete focal target ablation are presented over clinically relevant ranges of focal target sizes and shapes, ablation region sizes, and levels of needle placement uncertainty. In addition, a table ismore » provided for estimating the maximum target size that is treatable. The results predict that targets whose length is at least 5 mm smaller than the diameter of each ablation region can be confidently ablated using, at most, four laser fibers if the standard deviation in each component of needle placement error is less than 3 mm. However, targets larger than this (i.e., near to or exceeding the diameter of each ablation region) require more careful planning. This process is facilitated by using the table provided. Conclusions: The probability of completely ablating a focal target using FLA is sensitive to the level of needle placement uncertainty, especially as the target length approaches and becomes greater than the diameter of ablated tissue that each individual laser fiber can achieve. The results of this work can be used to help determine individual patient eligibility for prostate FLA, to guide the planning of prostate FLA, and to quantify the clinical benefit of using advanced systems for accurate needle delivery for this treatment modality.« less

Laboratory Simulations of Micrometeoroid Ablation

NASA Astrophysics Data System (ADS)

Thomas, Evan Williamson

Each day, several tons of meteoric material enters Earth's atmosphere, the majority of which consist of small dust particles (micrometeoroids) that completely ablate at high altitudes. The dust input has been suggested to play a role in a variety of phenomena including: layers of metal atoms and ions, nucleation of noctilucent clouds, effects on stratospheric aerosols and ozone chemistry, and the fertilization of the ocean with bio-available iron. Furthermore, a correct understanding of the dust input to the Earth provides constraints on inner solar system dust models. Various methods are used to measure the dust input to the Earth including satellite detectors, radar, lidar, rocket-borne detectors, ice core and deep-sea sediment analysis. However, the best way to interpret each of these measurements is uncertain, which leads to large uncertainties in the total dust input. To better understand the ablation process, and thereby reduce uncertainties in micrometeoroid ablation measurements, a facility has been developed to simulate the ablation of micrometeoroids in laboratory conditions. An electrostatic dust accelerator is used to accelerate iron particles to relevant meteoric velocities (10-70 km/s). The particles are then introduced into a chamber pressurized with a target gas, and they partially or completely ablate over a short distance. An array of diagnostics then measure, with timing and spatial resolution, the charge and light that is generated in the ablation process. In this thesis, we present results from the newly developed ablation facility. The ionization coefficient, an important parameter for interpreting meteor radar measurements, is measured for various target gases. Furthermore, experimental ablation measurements are compared to predictions from commonly used ablation models. In light of these measurements, implications to the broader context of meteor ablation are discussed.

Approaches to catheter ablation for persistent atrial fibrillation.

PubMed

Verma, Atul; Jiang, Chen-yang; Betts, Timothy R; Chen, Jian; Deisenhofer, Isabel; Mantovan, Roberto; Macle, Laurent; Morillo, Carlos A; Haverkamp, Wilhelm; Weerasooriya, Rukshen; Albenque, Jean-Paul; Nardi, Stefano; Menardi, Endrj; Novak, Paul; Sanders, Prashanthan

2015-05-07

Catheter ablation is less successful for persistent atrial fibrillation than for paroxysmal atrial fibrillation. Guidelines suggest that adjuvant substrate modification in addition to pulmonary-vein isolation is required in persistent atrial fibrillation. We randomly assigned 589 patients with persistent atrial fibrillation in a 1:4:4 ratio to ablation with pulmonary-vein isolation alone (67 patients), pulmonary-vein isolation plus ablation of electrograms showing complex fractionated activity (263 patients), or pulmonary-vein isolation plus additional linear ablation across the left atrial roof and mitral valve isthmus (259 patients). The duration of follow-up was 18 months. The primary end point was freedom from any documented recurrence of atrial fibrillation lasting longer than 30 seconds after a single ablation procedure. Procedure time was significantly shorter for pulmonary-vein isolation alone than for the other two procedures (P<0.001). After 18 months, 59% of patients assigned to pulmonary-vein isolation alone were free from recurrent atrial fibrillation, as compared with 49% of patients assigned to pulmonary-vein isolation plus complex electrogram ablation and 46% of patients assigned to pulmonary-vein isolation plus linear ablation (P=0.15). There were also no significant differences among the three groups for the secondary end points, including freedom from atrial fibrillation after two ablation procedures and freedom from any atrial arrhythmia. Complications included tamponade (three patients), stroke or transient ischemic attack (three patients), and atrioesophageal fistula (one patient). Among patients with persistent atrial fibrillation, we found no reduction in the rate of recurrent atrial fibrillation when either linear ablation or ablation of complex fractionated electrograms was performed in addition to pulmonary-vein isolation. (Funded by St. Jude Medical; ClinicalTrials.gov number, NCT01203748.).

Microembolism and catheter ablation I: a comparison of irrigated radiofrequency and multielectrode-phased radiofrequency catheter ablation of pulmonary vein ostia.

PubMed

Haines, David E; Stewart, Mark T; Dahlberg, Sarah; Barka, Noah D; Condie, Cathy; Fiedler, Gary R; Kirchhof, Nicole A; Halimi, Franck; Deneke, Thomas

2013-02-01

Cerebral diffusion-weighted MRI lesions have been observed after catheter ablation of atrial fibrillation. We hypothesized that conditions predisposing to microembolization could be identified using a porcine model of pulmonary vein ablation and an extracorporeal circulation loop. Ablations of the pulmonary veins were performed in 18 swine with echo monitoring. The femoral artery and vein were cannulated and an extracorporeal circulation loop with 2 ultrasonic bubble detectors and a 73-μm filter were placed in series. Microemboli and microbubbles were compared between ablation with an irrigated radiofrequency system (Biosense-Webster) and a phased radiofrequency multielectrode system (pulmonary vein ablation catheter [PVAC], Medtronic, Inc, Carlsbad, CA) in unipolar and 3 blended unipolar/bipolar modes. Animal pathology was examined. The size and number of microbubbles observed during ablation ranged from 30 to 180 μm and 0 to 3253 bubbles per ablation. Microbubble volumes with PVAC (29.1 nL) were greater than with irrigated radiofrequency (0.4 nL; P=0.045), and greatest with type II or III microbubbles on transesophageal echocardiography. Ablation with the PVAC showed fewest microbubbles in the unipolar mode (P=0.012 versus bipolar). The most occurred during bipolar energy delivery with overlap of proximal and distal electrodes (median microbubble volume, 1744 nL; interquartile range, 737-4082 nL; maximum, 19 516 nL). No cerebral MRI lesions were seen, but 2 animals had renal embolization. Left atrial ablation with irrigated radiofrequency and PVAC catheters in swine is associated with microbubble and microembolus production. Avoiding overlap of electrodes 1 and 10 on PVAC should reduce the microembolic burden associated with this procedure.

Uterine fibroids: Influence of "T2-Rim sign" on immediate therapeutic responses to magnetic resonance imaging-guided high-intensity focused ultrasound ablation.

PubMed

Yeo, Sin Yuin; Kim, Young-Sun; Lim, Hyo Keun; Rhim, Hyunchul; Jung, Sin-Ho; Hwang, Na Young

2017-12-01

To investigate the influence of a high-signal-intensity peripheral rim on T2-weighted MR images (i.e., T2-rim sign) on the immediate therapeutic responses of MR-guided high intensity focused ultrasound (MR-HIFU) ablation of uterine fibroids. This retrospective study was approved by the institutional review board, and patient informed consent was obtained for MR-HIFU ablation. In total, 196 fibroids (diameter 6.2±2.6cm) in 123 women (age 43.4±5.0 years) who underwent MR-HIFU ablation from January 2013 to April 2016 were included. The effects of a T2-rim sign on the immediate therapeutic responses (non-perfused volume [NPV] ratio, ablation efficiency [NPV/treatment cell volume], ablation quality [grade 1-5, poor to excellent]) were investigated with univariable and multivariable analyses using generalized estimating equation (GEE) analysis. In multivariable analysis, T2 signal intensity ratio of fibroids-to-skeletal muscle, relative peak enhancement of fibroids, and subcutaneous fat thickness were also considered. The presence of a T2-rim sign significantly lowered the NPV ratio (54.0±28.0% vs. 83.7±17.7%), ablation efficiency (0.6±0.5 vs. 1.3±0.6), ablation quality (3.1±1.2 vs. 4.2±0.8), (P<0.0001). GEE analysis showed that the presence of a T2-rim sign was independently significant for ablation efficiency and ablation quality (P<0.05). Uterine fibroids with a T2-rim sign showed significantly poorer immediate therapeutic responses to MR-HIFU ablation. Copyright © 2017 Elsevier B.V. All rights reserved.

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

PubMed

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

2018-07-01

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

Radiofrequency ablation for hepatocellular carcinoma: assistant techniques for difficult cases.

PubMed

Inoue, Tatsuo; Minami, Yasunori; Chung, Hobyung; Hayaishi, Sousuke; Ueda, Taisuke; Tatsumi, Chie; Takita, Masahiro; Kitai, Satoshi; Hatanaka, Kinuyo; Ishikawa, Emi; Yada, Norihisa; Hagiwara, Satoru; Ueshima, Kazuomi; Kudo, Masatoshi

2010-07-01

To confirm the safety and effectiveness of techniques to assist radiofrequency ablation (RFA) for difficult cases, we retrospectively evaluated successful treatment rates, early complications and local tumor progressions. Between June 1999 and April 2009, a total of 341 patients with 535 nodules were treated as difficult cases. Artificial pleural effusion assisted ablation was performed on 64 patients with 82 nodules. Artificial ascites-assisted ablation was performed on 11 patients with 13 nodules. Cooling by endoscopic nasobiliary drainage (ENBD) tube-assisted ablation was performed on 6 patients with 8 nodules. When the tumors were not well visualized with conventional B-mode ultrasonography (US), contrast-enhanced US-assisted ablation with Levovist or Sonazoid or virtual CT sonography-assisted ablation was performed. Contrast-enhanced US-assisted ablation was performed on 139 patients with 224 nodules and virtual CT sonography-assisted ablation was performed on 121 patients with 209 nodules. In total, complete ablation was achieved in 514 of 535 (96%) nodules in difficult cases. For RFA with artificial pleural effusion, artificial ascites and ENBD, complete response was confirmed in all cases. For contrast-enhanced US- and CT sonography-assisted ablation, complete response was 95%. Early complications were recognized in 24 cases (4.5%). All cases recovered with no invasive treatment. Local tumor recurrence was investigated in 377 nodules of 245 patients, and 69 (18%) nodules were positive. Tumor recurrences in each assisted technique were 14.7% in artificial pleural effusion cases, 7% in artificial ascites, 12.5% in ENBD tube cases, 31% in virtual CT sonography, and 8.5% in contrast-enhanced US. Although local tumor progression needs to be carefully monitored, assisted techniques of RFA for difficult cases are well tolerated and expand the indications of RFA. Copyright (c) 2010 S. Karger AG, Basel.

Percutaneous Microwave Ablation of Renal Angiomyolipomas.

PubMed

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

2016-03-01

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

The effects of Magnetic Resonance Imaging-guided High-Intensity Focused Ultrasound ablation on human cadaver breast tissue.

PubMed

Merckel, Laura G; Deckers, Roel; Baron, Paul; Bleys, Ronald L A W; van Diest, Paul J; Moonen, Chrit T W; Mali, Willem P Th M; van den Bosch, Maurice A A J; Bartels, Lambertus W

2013-10-05

Magnetic Resonance Imaging-guided High-Intensity Focused Ultrasound (MR-HIFU) is a promising technique for non-invasive breast tumor ablation. The purpose of this study was to investigate the effects of HIFU ablation and thermal exposure on ex vivo human breast tissue. HIFU ablations were performed in three unembalmed cadaveric breast specimens using a clinical MR-HIFU system. Sonications were performed in fibroglandular and adipose tissue. During HIFU ablation, time-resolved anatomical MR images were acquired to monitor macroscopic tissue changes. Furthermore, the breast tissue temperature was measured using a thermocouple to investigate heating and cooling under HIFU exposure. After HIFU ablation, breast tissue samples were excised and prepared for histopathological analysis. In addition, thermal exposure experiments were performed to distinguish between different levels of thermal damage using immunohistochemical staining. Irreversible macroscopic deformations up to 3.7 mm were observed upon HIFU ablation both in fibroglandular and in adipose tissue. No relationship was found between the sonication power or the maximum tissue temperature and the size of the deformations. Temperature measurements after HIFU ablation showed a slow decline in breast tissue temperature. Histopathological analysis of sonicated regions demonstrated ablated tissue and morphologically complete cell death. After thermal exposure, samples exposed to three different temperatures could readily be distinguished. In conclusion, the irreversible macroscopic tissue deformations in ex vivo human breast tissue observed during HIFU ablation suggest that it might be relevant to monitor tissue deformations during MR-HIFU treatments. Furthermore, the slow decrease in breast tissue temperature after HIFU ablation increases the risk of heat accumulation between successive sonications. Since cell death was inflicted after already 5 minutes at 75°C, MR-HIFU may find a place in non-invasive treatment of breast tumors. © 2013 Elsevier B.V. All rights reserved.

Prediction of radiofrequency ablation lesion formation using a novel temperature sensing technology incorporated in a force sensing catheter.

PubMed

Rozen, Guy; Ptaszek, Leon; Zilberman, Israel; Cordaro, Kevin; Heist, E Kevin; Beeckler, Christopher; Altmann, Andres; Ying, Zhang; Liu, Zhenjiang; Ruskin, Jeremy N; Govari, Assaf; Mansour, Moussa

2017-02-01

Real-time radiofrequency (RF) ablation lesion assessment is a major unmet need in cardiac electrophysiology. The purpose of this study was to assess whether improved temperature measurement using a novel thermocoupling (TC) technology combined with information derived from impedance change, contact force (CF) sensing, and catheter orientation allows accurate real-time prediction of ablation lesion formation. RF ablation lesions were delivered in the ventricles of 15 swine using a novel externally irrigated-tip catheter containing 6 miniature TC sensors in addition to force sensing technology. Ablation duration, power, irrigation rate, impedance drop, CF, and temperature from each sensor were recorded. The catheter "orientation factor" was calculated using measurements from the different TC sensors. Information derived from all the sources was included in a mathematical model developed to predict lesion depth and validated against histologic measurements. A total of 143 ablation lesions were delivered to the left ventricle (n = 74) and right ventricle (n = 69). Mean CF applied during the ablations was 14.34 ± 3.55g, and mean impedance drop achieved during the ablations was 17.5 ± 6.41 Ω. Mean difference between predicted and measured ablation lesion depth was 0.72 ± 0.56 mm. In the majority of lesions (91.6%), the difference between estimated and measured depth was ≤1.5 mm. Accurate real-time prediction of RF lesion depth is feasible using a novel ablation catheter-based system in conjunction with a mathematical prediction model, combining elaborate temperature measurements with information derived from catheter orientation, CF sensing, impedance change, and additional ablation parameters. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

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

PubMed

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.

Efficacy and Safety of Radiofrequency Ablation for Focal Hepatic Lesions Adjacent to Gallbladder: Reconfiguration of the Ablation Zone through Probe Relocation and Ablation Time Reduction.

PubMed

Choi, In Young; Kim, Pyo Nyun; Lee, Sung Gu; Won, Hyung Jin; Shin, Yong Moon

2017-10-01

To evaluate the safety and efficacy of radiofrequency (RF) ablation for treatment of focal hepatic lesions adjacent to the gallbladder with electrode relocation and ablation time reduction. Thirty-nine patients who underwent RF ablation for focal hepatic lesions adjacent to the gallbladder (≤ 10 mm) were evaluated retrospectively from January 2011 to December 2014 (30 men and 9 women; age range, 51-85 y; mean age, 65 y). Of 36 patients with hepatocellular carcinoma, 3 had a second treatment for recurrence (mean tumor size, 15 mm ± 6). Patients were divided into 2 subgroups based on lesion distance from the gallbladder: nonabutting (> 5 mm; n = 19) and abutting (≤ 5 mm; n = 20). Electrodes were inserted parallel to the gallbladder through the center of a tumor in the nonabutting group and through the center of the expected ablation zone between a 5-mm safety zone on the liver side and the gallbladder in the abutting group. Ablation time was decreased in proportion to the transverse diameter of the expected ablation zone. Technical success and technical effectiveness rates were 89.7% and 97.4%, respectively, with no significant differences between groups (P = 1.00). Local tumor progression was observed in 3 patients (1 in the nonabutting group and 2 in the abutting group; P = 1.00). There were no major complications. The gallbladder was thickened in 10 patients, with no significant difference between groups (P = .72). Biloma occurred in 1 patient in the nonabutting group. RF ablation with electrode relocation and reduction of ablation time can be a safe and effective treatment for focal hepatic lesions adjacent to the gallbladder. Copyright © 2017 SIR. Published by Elsevier Inc. All rights reserved.

Impact of a Novel Catheter Tracking System on Radiation Exposure during the Procedural Phases of Atrial Fibrillation and Flutter Ablation.

PubMed

Malliet, Nicolas; Andrade, Jason G; Khairy, Paul; Thanh, Hien Kiem Nguyen; Venier, Sandrine; Dubuc, Marc; Dyrda, Katia; Guerra, Peter; Mondésert, Blandine; Rivard, Léna; Tadros, Rafik; Talajic, Mario; Thibault, Bernard; Roy, Denis; Macle, Laurent

2015-07-01

Fluoroscopic guidance is used to position catheters during cardiac ablation. We evaluated the impact of a novel nonfluoroscopic sensor-guided electromagnetic navigation system (MG) on radiation exposure during catheter ablation of atrial fibrillation (AF) or atrial flutter (AFL). A total of 134 consecutive patients referred for ablation of AF (n = 44) or AFL (n = 90) ablation were prospectively enrolled. In one group the MG system was used for nonfluoroscopic catheter positioning, whereas in the conventional group standard fluoroscopy was utilized. Fluoroscopy times were assessed for each stage of procedure and total radiation exposure was quantified. Patient characteristics were similar between the groups. The procedural end point was achieved in all. Median (interquartile range [IQR]) fluoroscopy times were 12.5 minutes (7.6, 17.4) MG group versus 21.5 minutes (15.3, 23.0) conventional group (P < 0.0001) for AF ablation, and 0.8 minutes (0.4, 2.5) MG group versus 9.9 minutes (5.1, 22.5) conventional group (P < 0.0001) for AFL ablation. Median (IQR) total radiation exposure (μGy·m(2)) was 1,107 (906, 2,033) MG group versus 2,835 (1,688, 3,855) conventional group (P = 0.0001) for AF ablation, and 161 (65, 537) MG group versus 1,651 (796, 4,569) conventional group (P < 0.0001) for AFL ablation. No difference in total procedural time was seen. The use of a novel nonfluoroscopic catheter tracking system is associated with a significant reduction in radiation exposure during AF and AFL ablation (61% and 90% reduction, respectively). In the era of heightened awareness of the importance of radiation reduction, this system represents a safe and efficient tool to decrease radiation exposure during electrophysiological ablation procedures. ©2015 Wiley Periodicals, Inc.

Long-Term Outcome With Catheter Ablation of Ventricular Tachycardia in Patients With Arrhythmogenic Right Ventricular Cardiomyopathy.

PubMed

Santangeli, Pasquale; Zado, Erica S; Supple, Gregory E; Haqqani, Haris M; Garcia, Fermin C; Tschabrunn, Cory M; Callans, David J; Lin, David; Dixit, Sanjay; Hutchinson, Mathew D; Riley, Michael P; Marchlinski, Francis E

2015-12-01

Catheter ablation of ventricular tachycardia (VT) in arrhythmogenic right ventricular cardiomyopathy improves short-term VT-free survival. We sought to determine the long-term outcomes of VT control and need for antiarrhythmic drug therapy after endocardial (ENDO) and adjuvant epicardial (EPI) substrate modification in patients with arrhythmogenic right ventricular cardiomyopathy. We examined 62 consecutive patients with Task Force criteria for arrhythmogenic right ventricular cardiomyopathy referred for VT ablation with a minimum follow-up of 1 year. Catheter ablation was guided by activation/entrainment mapping for tolerated VT and pacemapping/targeting of abnormal substrate for unmappable VT. Adjuvant EPI ablation was performed when recurrent VT or persistent inducibility after ENDO-only ablation. Endocardial plus adjuvant EPI ablation was performed in 39 (63%) patients, including 13 who crossed over to ENDO-EPI after VT recurrence during follow-up, after ENDO-only ablation. Before ablation, 54 of 62 patients failed a mean of 2.4 antiarrhythmic drugs, including amiodarone in 29 (47%) patients. During follow-up of 56±44 months after the last ablation, VT-free survival was 71% with only a single VT episode in additional 9 patients (15%). At last follow-up, 39 (64%) patients were only on β-blockers or no treatment, 21 were on class 1 or 3 antiarrhythmic drugs (11 for atrial arrhythmias), and 2 were on amiodarone as a bridge to heart transplantation. The long-term outcome after ENDO and adjuvant EPI substrate ablation of VT in arrhythmogenic right ventricular cardiomyopathy is good. Most patients have complete VT control without amiodarone therapy and limited need for antiarrhythmic drugs. © 2015 American Heart Association, Inc.

Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun, E-mail: wenjunwang@mail.xjtu.edu.cn

The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter), ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloymore » were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm{sup 2}.« less

A comparative analysis of clinical outcomes and disposable costs of different catheter ablation methods for the treatment of atrioventricular nodal reentrant tachycardia

PubMed Central

Berman, Adam E; Rivner, Harold; Chalkley, Robin; Heboyan, Vahé

2017-01-01

Background Catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) is a commonly performed electrophysiology (EP) procedure. Few data exist comparing conventional (CONV) versus novel ablation strategies from both clinical and direct cost perspectives. We sought to investigate the disposable costs and clinical outcomes associated with three different ablation methodologies used in the ablation of AVNRT. Methods We performed a retrospective review of AVNRT ablations performed at Augusta University Medical Center from 2006 to 2014. A total of 183 patients were identified. Three different ablation techniques were compared: CONV manual radiofrequency (RF) (n=60), remote magnetic navigation (RMN)-guided RF (n=67), and cryoablation (CRYO) (n=56). Results Baseline demographics did not differ between the three groups except for a higher prevalence of cardiomyopathy in the RMN group (p<0.01). The clinical end point of interest was recurrent AVNRT following the index ablation procedure. A significantly higher number of recurrent AVNRT cases occurred in the CRYO group as compared to CONV and RMN (p=0.003; OR =7.75) groups. Cost-benefit analysis showed both CONV and RMN to be dominant compared to CRYO. Cost-minimization analysis demonstrated the least expensive ablation method to be CONV (mean disposable catheter cost = CONV US$2340; CRYO US$3515; RMN US$5190). Despite comparable clinical outcomes, the incremental cost of RMN over CONV averaged US$3094 per procedure. Conclusion AVNRT ablation using either CONV or RMN techniques is equally effective and associated with lower AVNRT recurrence rates than CRYO. CONV ablation carries significant disposable cost savings as compared to RMN, despite similar efficacy. PMID:29138585

Impact of steerable sheaths on contact forces and reconnection sites in ablation for persistent atrial fibrillation.

PubMed

Ullah, Waqas; Hunter, Ross J; McLean, Ailsa; Dhinoja, Mehul; Earley, Mark J; Sporton, Simon; Schilling, Richard J

2015-03-01

In preclinical studies, catheter contact force (CF) during radiofrequency ablation correlates with the subsequent lesion size. We investigated the impact of steerable sheaths on ablation CF, its consistency, and wide area circumferential ablation (WACA) line reconnection sites. Five thousand and sixty-four ablations were analyzed across 60 patients undergoing first-time ablation for persistent AF using a CF-sensing catheter: 19 manual nonsteerable sheath (Manual-NSS), 11 manual steerable sheath, and 30 robotic steerable sheath (Sensei, Hansen Medical Inc.) procedures were studied. Ablation CFs were higher in the steerable sheath groups for all left atrial ablations and also WACA ablations specifically (P < 0.006), but less consistent per WACA segment (P < 0.005). There were significant differences in the CFs around both WACAs by group: in the left WACA CFs were lower with Manual-NSS, other than at the anterior-inferior and posterior-superior regions, and lower in the right WACA, other than the anterior-superior region. There was a difference in the proportion of segments chronically reconnecting across groups: Manual-NSS 26.5%, manual steerable sheath 4.6%, robotic 12% (P < 0.0005). The left atrial appendage/PV ridge and right posterior wall were common sites of reconnection in all groups. Steerable sheaths increased ablation CF; however, there were region-specific heterogeneities in the extent of increment, with some segments where they failed to increase CF. Steerable sheath use was associated with reduced WACA-segment reconnection. It may be that the benefits of steerable sheath use in terms of higher CFs could be translated to improved clinical outcomes if regional weaknesses of this technology are taken into account during ablation procedures. © 2014 Wiley Periodicals, Inc.

Assessment of liver ablation using cone beam computed tomography.

PubMed

Abdel-Rehim, Mohamed; Ronot, Maxime; Sibert, Annie; Vilgrain, Valérie

2015-01-14

To investigate the feasibility and accuracy of cone beam computed tomography (CBCT) in assessing the ablation zone after liver tumor ablation. Twenty-three patients (17 men and 6 women, range: 45-85 years old, mean age 65 years) with malignant liver tumors underwent ultrasound-guided percutaneous tumor ablation [radiofrequency (n = 14), microwave (n = 9)] followed by intravenous contrast-enhanced CBCT. Baseline multidetector computed tomography (MDCT) and peri-procedural CBCT images were compared. CBCT image quality was assessed as poor, good, or excellent. Image fusion was performed to assess tumor coverage, and quality of fusion was rated as bad, good, or excellent. Ablation zone volumes on peri-procedural CBCT and post-procedural MDCT were compared using the non-parametric paired Wilcoxon t-test. Rate of primary ablation effectiveness was 100%. There were no complications related to ablation. Local tumor recurrence and new liver tumors were found 3 mo after initial treatment in one patient (4%). The ablation zone was identified in 21/23 (91.3%) patients on CBCT. The fusion of baseline MDCT and peri-procedural CBCT images was feasible in all patients and showed satisfactory tumor coverage (at least 5-mm margin). CBCT image quality was poor, good, and excellent in 2 (9%), 8 (35%), and 13 (56%), patients respectively. Registration quality between peri-procedural CBCT and post-procedural MDCT images was good to excellent in 17/23 (74%) patients. The median ablation volume on peri-procedural CBCT and post-procedural MDCT was 30 cm(3) (range: 4-95 cm(3)) and 30 cm(3) (range: 4-124 cm(3)), respectively (P-value > 0.2). There was a good correlation (r = 0.79) between the volumes of the two techniques. Contrast-enhanced CBCT after tumor ablation of the liver allows early assessment of the ablation zone.

High power microwave ablation of normal swine lung: impact of duration of energy delivery on adverse event and heat sink effects.

PubMed

Kodama, Hiroshi; Ueshima, Eisuke; Gao, Song; Monette, Sebastien; Paluch, Lee-Ronn; Howk, Kreg; Erinjeri, Joseph P; Solomon, Stephen B; Srimathveeravalli, Govindarajan

2018-04-18

The purpose of this study is to assess the impact of duration of energy delivery on adverse events (AEs) and heat sink effects during high power microwave ablation (MWA) of normal swine lung. High power (100 W) MWA was performed with short (2 min, 18 ablations) or long (10 min, nine ablations) duration of energy delivery in unilateral lung of swine (n = 10). CT imaging was done prior to sacrifice at 2 or 28 d post-treatment, with additional imaging at 7 and 14 d for the latter cohort. Ablation zones were assessed with CT imaging and histopathology analysis. Differences in AEs and ablation characteristics between groups were compared with Fisher's exact test and Student's t-test, respectively. There were no significant differences in formation of air-filled needle tract, cavitation, and pneumonia (p > 0.5) between the treatment groups. Intra-procedural pneumothorax requiring chest tube placement occurred in three animals. Substantial (>20%, p = 0.01) intra-procedural ablation zone distortion was observed in both groups. The presence of large airways or blood vessels did not result in heat sink effect within the ablation zones and was not indicative of reduced ablation size. Increased energy delivery yielded larger (8.9 ± 3.1 cm 3 vs. 3.4 ± 1.7 cm 3 , p < 0.001) spherical ablations (sphericity: 0.70 ± 0.10 vs. 0.56 ± 0.13, p = 0.01). High power MWA of normal lung with longer duration of energy delivery can create larger spherical ablations, without significant differences in post-procedure AEs when compared with shorter energy delivery time.

Microwave Ablation (MWA): Basics, Technique and Results in Primary and Metastatic Liver Neoplasms - Review Article.

PubMed

Vogl, Thomas J; Nour-Eldin, Nour-Eldin A; Hammerstingl, Renate Maria; Panahi, Bita; Naguib, Nagy N N

2017-11-01

Purpose  The locoregional interventional oncological treatment approach is an accepted modality for liver neoplasms, especially for hepatocellular carcinoma (HCC) and oligonodular liver metastases. Materials and Methods  The main aim of ablation therapies like microwave ablation (MWA) is to eradicate all malignant cells in a minimally invasive technique under imaging guidance while preserving the healthy tissue with a sufficient safety margin (at least 5 mm) surrounding the ablated lesion. Results  Ablation therapy can be performed via a percutaneous, laparoscopic or intraoperative approach under ultrasound, MRI or CT guidance for adequate localization and monitoring of the ablation process. Conclusion  Ablation is the method of choice for oligonodular HCCs ≤ 3 cm. The technical success rate varies from 88 % to 98 % and progression-free survival (PFS) at 3 years from 27 % to 91.7 %. The same criteria apply to the therapy of liver metastases. Key Points   · Careful selection of patients proves to be essential for optimum results of MWA. · Interventionists should be familiar with all aspects of complication and rapid assessment of imaging methods in order to evaluate induced damage by thermal ablation. · MWA seems to have some advantages over radiofrequency ablation, like shorter ablation time, less pain, less heat sink effect; however, scientific proof is needed. Citation Format · Vogl TJ, Nour-Eldin A, Hammerstingl RM et al. Microwave Ablation (MWA): Basics, Technique and Results in Primary and Metastatic Liver Neoplasms - Review Article. Fortschr Röntgenstr 2017; 189: 1055 - 1066. © Georg Thieme Verlag KG Stuttgart · New York.

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

PubMed

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

2018-02-01

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

Microwave ablation with multiple simultaneously powered small-gauge triaxial antennas: results from an in vivo swine liver model.

PubMed

Brace, Christopher L; Laeseke, Paul F; Sampson, Lisa A; Frey, Tina M; van der Weide, Daniel W; Lee, Fred T

2007-07-01

To prospectively investigate the ability of a single generator to power multiple small-diameter antennas and create large zones of ablation in an in vivo swine liver model. Thirteen female domestic swine (mean weight, 70 kg) were used for the study as approved by the animal care and use committee. A single generator was used to simultaneously power three triaxial antennas at 55 W per antenna for 10 minutes in three groups: a control group where antennas were spaced to eliminate ablation zone overlap (n=6; 18 individual zones of ablation) and experimental groups where antennas were spaced 2.5 cm (n=7) or 3.0 cm (n=5) apart. Animals were euthanized after ablation, and ablation zones were sectioned and measured. A mixed linear model was used to test for differences in size and circularity among groups. Mean (+/-standard deviation) cross-sectional areas of multiple-antenna zones of ablation at 2.5- and 3.0-cm spacing (26.6 cm(2) +/- 9.7 and 32.2 cm(2) +/- 8.1, respectively) were significantly larger than individual ablation zones created with single antennas (6.76 cm(2) +/- 2.8, P<.001) and were 31% (2.5-cm spacing group: multiple antenna mean area, 26.6 cm(2); 3 x single antenna mean area, 20.28 cm(2)) to 59% (3.0-cm spacing group: multiple antenna mean area, 32.2 cm(2); 3 x single antenna mean area, 20.28 cm(2)) larger than 3 times the mean area of the single-antenna zones. Zones of ablation were found to be very circular, and vessels as large as 1.1 cm were completely coagulated with multiple antennas. A single generator may effectively deliver microwave power to multiple antennas. Large volumes of tissue may be ablated and large vessels coagulated with multiple-antenna ablation in the same time as single-antenna ablation. (c) RSNA, 2007.

Determining Distributed Ablation over Dirty Ice Areas of Debris-covered Glaciers Using a UAV-SfM Approach

NASA Astrophysics Data System (ADS)

Woodget, A.; Fyffe, C. L.; Kirkbride, M. P.; Deline, P.; Westoby, M.; Brock, B. W.

2017-12-01

Dirty ice areas (where debris cover is discontinuous) are often found on debris-covered glaciers above the limit of continuous debris and are important because they are areas of high melt and have been recognized as the locus of the identified upglacier increase in debris cover. The modelling of glacial ablation in areas of dirty ice is in its infancy and is currently restricted to theoretical studies. Glacial ablation is traditionally determined at point locations using stakes drilled into the ice. However, in areas of dirty ice, ablation is highly spatially variable, since debris a few centimetres thick is near the threshold between enhancing and reducing ablation. As a result, it is very difficult to ascertain if point ablation measurements are representative of ablation of the area surrounding the stake - making these measurements unsuitable for the validation of models of dirty ice ablation. This paper aims to quantify distributed ablation and its relationship to essential dirty ice characteristics with a view to informing the construction of dirty ice melt models. A novel approach to determine distributed ablation is presented which uses repeat aerial imagery acquired from a UAV (Unmanned Aerial Vehicle), processed using SfM (Structure from Motion) techniques, on an area of dirty ice on Miage Glacier, Italian Alps. A spatially continuous ablation map is presented, along with a correlation to the local debris characteristics. Furthermore, methods are developed which link ground truth data on the percentage debris cover, albedo and clast depth to the UAV imagery, allowing these characteristics to be determined for the entire study area, and used as model inputs. For example, debris thickness is determined through a field relationship with clast size, which is then correlated with image texture and point cloud roughness metrics derived from the UAV imagery. Finally, we evaluate the potential of our novel approach to lead to improved modelling of dirty ice ablation.

Chemoattraction and chemorepulsion of Strongyloides stercoralis infective larvae on a sodium chloride gradient is mediated by amphidial neuron pairs ASE and ASH, respectively.

PubMed

Forbes, W M; Ashton, F T; Boston, R; Zhu, X; Schad, G A

2004-03-25

Depending on its concentration, sodium chloride acts as either an attractant or a repellant to the infective larvae (L3i) of Strongyloides stercoralis. On a concentration gradient, L3i are attracted to 0.05 M NaCl, but repelled by 2.8M. To test the hypothesis that amphidial neurons ASE and ASH might mediate attraction and repulsion, respectively, these neurons, and control neurons as well, were ablated in hatchling larvae with a laser microbeam. After the larvae attained infectivity (L3i), they were tested on a NaCl gradient. When placed at low salinity, 73.5% of normal controls migrated "up" the gradient, while 26.4% crawled randomly. In contrast, only 20.6% of ASE-ablated L3i migrated "up" the gradient, while 79.4% migrated randomly. Ablation-control ASK-ablated L3i (58.8%) migrated "up" the gradient while 41.1% crawled randomly. When placed at a region of high salinity, 100% of normal control L3i migrated "down" the gradient, whereas 62.5% of ASH-ablated L3i migrated randomly, the remaining 37.5% migrating "down" the gradient. In sharp contrast with ASH-ablated L3i, 94.1% of ablation-control larvae, i.e. ASK-ablated L3i, migrated "down" the gradient. Migration behavior of ASE- and ASH-ablated L3i was significantly different (P < 0.001) from that of ASK-ablated L3i and normal controls. It is noteworthy that 87.5% of ASE-ablated L3i that failed to exhibit chemoattractive behavior were actively chemorepelled from high salinity. Also, 70.0% of ASH-ablated L3i that failed to be chemorepelled from high salinity were capable of chemoattractive behavior, indicating that the worms had retained their behavioral responses except for those associated with the targeted neurons.

Radiofrequency Ablation, MR Thermometry, and High-Spatial-Resolution MR Parametric Imaging with a Single, Minimally Invasive Device.

PubMed

Ertürk, M Arcan; Sathyanarayana Hegde, Shashank; Bottomley, Paul A

2016-12-01

Purpose To develop and demonstrate in vitro and in vivo a single interventional magnetic resonance (MR)-active device that integrates the functions of precise identification of a tissue site with the delivery of radiofrequency (RF) energy for ablation, high-spatial-resolution thermal mapping to monitor thermal dose, and quantitative MR imaging relaxometry to document ablation-induced tissue changes for characterizing ablated tissue. Materials and Methods All animal studies were approved by the institutional animal care and use committee. A loopless MR imaging antenna composed of a tuned microcable either 0.8 or 2.2 mm in diameter with an extended central conductor was switched between a 3-T MR imaging unit and an RF power source to monitor and perform RF ablation in bovine muscle and human artery samples in vitro and in rabbits in vivo. High-spatial-resolution (250-300-μm) proton resonance frequency shift MR thermometry was interleaved with ablations. Quantitative spin-lattice (T1) and spin-spin (T2) relaxation time MR imaging mapping was performed before and after ablation. These maps were compared with findings from gross tissue examination of the region of ablated tissue after MR imaging. Results High-spatial-resolution MR imaging afforded temperature mapping in less than 8 seconds for monitoring ablation temperatures in excess of 85°C delivered by the same device. This produced irreversible thermal injury and necrosis. Quantitative MR imaging relaxation time maps demonstrated up to a twofold variation in mean regional T1 and T2 after ablation versus before ablation. Conclusion A simple, integrated, minimally invasive interventional probe that provides image-guided therapy delivery, thermal mapping of dose, and detection of ablation-associated MR imaging parametric changes was developed and demonstrated. With this single-device approach, coupling-related safety concerns associated with multiple conductor approaches were avoided. © RSNA, 2016 Online supplemental material is available for this article.

Volumetric Trends Associated with MR-guided Stereotactic Laser Amygdalohippocampectomy in Mesial Temporal Lobe Epilepsy

PubMed Central

Patel, Nitesh V; Sundararajan, Sri; Keller, Irwin; Danish, Shabbar

2018-01-01

Objective: Magnetic resonance (MR)-guided stereotactic laser amygdalohippocampectomy is a minimally invasive procedure for the treatment of refractory epilepsy in patients with mesial temporal sclerosis. Limited data exist on post-ablation volumetric trends associated with the procedure. Methods: 10 patients with mesial temporal sclerosis underwent MR-guided stereotactic laser amygdalohippocampectomy. Three independent raters computed ablation volumes at the following time points: pre-ablation (PreA), immediate post-ablation (IPA), 24 hours post-ablation (24PA), first follow-up post-ablation (FPA), and greater than three months follow-up post-ablation (>3MPA), using OsiriX DICOM Viewer (Pixmeo, Bernex, Switzerland). Statistical trends in post-ablation volumes were determined for the time points. Results: MR-guided stereotactic laser amygdalohippocampectomy produces a rapid rise and distinct peak in post-ablation volume immediately following the procedure. IPA volumes are significantly higher than all other time points. Comparing individual time points within each raters dataset (intra-rater), a significant difference was seen between the IPA time point and all others. There was no statistical difference between the 24PA, FPA, and >3MPA time points. A correlation analysis demonstrated the strongest correlations at the 24PA (r=0.97), FPA (r=0.95), and 3MPA time points (r=0.99), with a weaker correlation at IPA (r=0.92). Conclusion: MR-guided stereotactic laser amygdalohippocampectomy produces a maximal increase in post-ablation volume immediately following the procedure, which decreases and stabilizes at 24 hours post-procedure and beyond three months follow-up. Based on the correlation analysis, the lower inter-rater reliability at the IPA time point suggests it may be less accurate to assess volume at this time point. We recommend post-ablation volume assessments be made at least 24 hours post-selective ablation of the amygdalohippocampal complex (SLAH).

The Effect of Atrial Fibrillation Ablation Techniques on P Wave Duration and P Wave Dispersion.

PubMed

Furniss, Guy O; Panagopoulos, Dimitrios; Kanoun, Sadeek; Davies, Edward J; Tomlinson, David R; Haywood, Guy A

2018-02-14

A reduction in surface electrocardiogram (ECG) P wave duration and dispersion is associated with improved outcomes in atrial fibrillation ablation. We investigated the effects of different ablation strategies on P wave duration and dispersion, hypothesising that extensive left atrial (LA) ablation with left atrial posterior wall isolation would give a greater reduction in P wave duration than more limited ablation techniques. A retrospective analysis of ECGs from patients who have undergone atrial fibrillation (AF) ablation was performed and pre-procedural sinus rhythm ECGs were compared with the post procedure ECGs. Maximal P wave duration was measured in leads I or II, minimum P wave duration in any lead and values were calculated for P wave duration and dispersion. Left atrial dimensions and medications at the time of ECG were documented. Ablation strategies compared were; pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF) and the persistent AF (PsAF) ablation strategies of pulmonary vein isolation plus additional linear lesions (Lines), left atrial posterior wall isolation via catheter (PWI) and left atrial posterior wall isolation via staged surgical and catheter ablation (Hybrid). Sixty-nine patients' ECGs were analysed: 19 PVI, 21 Lines, 14 PWI, 15 Hybrid. Little correlation was seen between pre-procedure left atrial size and P wave duration (r=0.24) but LA size and P wave duration was larger in PsAF patients. A significant difference was seen in P wave reduction driven by Hybrid AF ablation (p<0.005) and Lines (<0.02). There was no difference amongst P wave dispersion between groups but the largest reduction was seen in the Hybrid ablation group. P wave duration increased with duration of continuous atrial fibrillation. Hybrid AF ablation significantly reduced P wave duration and dispersion compared to other ablation strategies including posterior wall isolation via catheter despite this being the same lesion set. Copyright © 2018 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.

Real-time iterative monitoring of radiofrequency ablation tumor therapy with 15O-water PET imaging.

PubMed

Bao, Ande; Goins, Beth; Dodd, Gerald D; Soundararajan, Anuradha; Santoyo, Cristina; Otto, Randal A; Davis, Michael D; Phillips, William T

2008-10-01

A method that provides real-time image-based monitoring of solid tumor therapy to ensure complete tumor eradication during image-guided interventional therapy would be a valuable tool. The short, 2-min half-life of (15)O makes it possible to perform repeated PET imaging at 20-min intervals at multiple time points before and after image-guided therapy. In this study, (15)O-water PET was evaluated as a tool to provide real-time feedback and iterative image guidance to rapidly monitor the intratumoral coverage of radiofrequency (RF) ablation therapy. Tumor RF ablation therapy was performed on head and neck squamous cell carcinoma (SCC) xenograft tumors (length, approximately 23 mm) in 6 nude rats. The tumor in each animal was ablated with RF (1-cm active size ablation catheter, 70 degrees C for 5 min) twice in 2 separate tumor regions with a 20-min separation. The (15)O-water PET images were acquired before RF ablation and after the first RF and second RF ablations using a small-animal PET scanner. In each PET session, approximately 100 MBq of (15)O-water in 1.0 mL of saline were injected intravenously into each animal. List-mode PET images were acquired for 7 min starting 20 s before injection. PET images were reconstructed by 2-dimensional ordered-subset expectation maximization into single-frame images and dynamic images at 10 s/frame. PET images were displayed and analyzed with software. Pre-RF ablation images demonstrate that (15)O-water accumulates in tumors with (15)O activity reaching peak levels immediately after administration. After RF ablation, the ablated region had almost zero activity, whereas the unablated tumor tissue continued to have a high (15)O-water accumulation. Using image feedback, the RF probe was repositioned to a tumor region with residual (15)O-water uptake and then ablated. The second RF ablation in this new region of the tumor resulted in additional ablation of the solid tumor, with a corresponding decrease in activity on the (15)O-water PET image. (15)O-water PET clearly demonstrated the ablated tumor region, whereas the unablated tumor continued to show high (15)O-water accumulation. (15)O-water imaging shows promise as a tool for on-site, real-time monitoring of image-guided interventional cancer therapy.

Initial clinical experience with a remote magnetic catheter navigation system for ablation of cavotricuspid isthmus-dependent right atrial flutter.

PubMed

Arya, Arash; Kottkamp, Hans; Piorkowski, Christopher; Bollmann, Andreas; Gerdes-Li, Jin-Hong; Riahi, Sam; Esato, Masahiro; Hindricks, Gerhard

2008-05-01

A remote magnetic navigation system (MNS) is available and has been used with a 4-mm-tip magnetic catheter for radiofrequency (RF) ablation of some supraventricular and ventricular arrhythmias; however, it has not been evaluated for the ablation of cavotricuspid isthmus-dependent right atrial flutter (AFL). The present study evaluates the feasibility and efficiency of this system and the newly available 8-mm-tip magnetic catheter to perform RF ablation in patients with AFL. Twenty-six consecutive patients (23 men, mean age 64.6 +/- 9.6 years) underwent RF ablation using a remote MNS. RF ablation was performed with an 8-mm-tip magnetic catheter (70 degrees C, maximum power 70 W, 90 seconds). The endpoint of ablation was complete bidirectional isthmus block. To assess a possible learning curve, procedural data were compared between the first 14 (group 1) and the rest (group 2) of the patients. The initial rhythm during ablation was AFL in 20 (19 counterclockwise and 1 clockwise) and sinus rhythm in six patients. Due to technical issues, the ablation in the 18th patient could not be done with the MNS, and so we switched to conventional ablation. The remote magnetic navigation and ablation procedure was successful in 24 of the 25 (96%) remaining patients with AFL. In one patient (patient 2), conventional catheter was used to complete the isthmus block after termination of AFL. The procedure, preparation, ablation, and fluoroscopy times (median [range]) were 53 (30-130) minutes, 28 (10-65) minutes, 25 (12-78) minutes, and 7.5 (3.2-20.8) minutes, respectively. Patients in group 2 had shorter procedure (45 [30-70] min vs 80 [57-130] min, P = 0.0001), preparation (25 [10-30] min vs 42 [30-65] min, P = 0.0001), ablation (20 [12-40] min vs 31 [20-78] min, P = 0.002), and fluoroscopy (7.2 [3.2-12.2] min vs 11.0 [5.4-20.8] min, P = 0.014) times. No complication occurred during the procedure. Using a remote MNS and an 8-mm-tip magnetic catheter, ablation of AFL is feasible, safe, and effective. Our data suggest that there is a short learning curve for this procedure.

[Catheter ablation of atrial fibrillation: Health Technology Assessment Report from the Italian Association of Arrhythmology and Cardiac Pacing (AIAC)].

PubMed

Themistoclakis, Sakis; Tritto, Massimo; Bertaglia, Emanuele; Berto, Patrizia; Bongiorni, Maria Grazia; Catanzariti, Domenico; De Fabrizio, Giuseppe; De Ponti, Roberto; Grimaldi, Massimo; Pandozi, Claudio; Tondo, Claudio; Gulizia, Michele

2011-11-01

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and significantly impact patients' quality of life, morbidity and mortality. The number of affected patients is expected to increase as well as the costs associated with AF management, mainly driven by hospitalizations. Over the last decade, catheter ablation techniques targeting pulmonary vein isolation have demonstrated to be effective in treating AF and preventing AF recurrence. This Health Technology Assessment report of the Italian Association of Arrhythmology and Cardiac Pacing (AIAC) aims to define the current role of catheter ablation of AF in terms of effectiveness, efficiency and appropriateness. On the basis of an extensive review of the available literature, this report provides (i) an overview of the epidemiology, clinical impact and socio-economic burden of AF; (ii) an evaluation of therapeutic options other than catheter ablation of AF; and (iii) a detailed presentation of clinical outcomes and cost-benefit ratio associated with catheter ablation. The costs of catheter ablation of AF in Italy were obtained using a bottom-up analysis of a resource utilization survey of 52 hospitals that were considered a representative sample, including 4 Centers that contributed with additional unit cost information in a separate questionnaire. An analysis of budget impact was also performed to evaluate the impact of ablation on the management costs of AF. Results of this analysis show that (1) catheter ablation is effective, safe and superior to antiarrhythmic drug therapy in maintaining sinus rhythm; (2) the cost of an ablation procedure in Italy typically ranges from €8868 to €9455, though current reimbursement remains insufficient, covering only about 60% of the costs; (3) the costs of follow-up are modest (about 8% of total costs); (4) assuming an adjustment of reimbursement to the real cost of an ablation procedure and a 5-10% increase in the annual rate of ablation procedures, after approximately 5-6 years this would result in significant incremental savings for the Italian Healthcare System. In conclusion, catheter ablation of AF is a cost-effective procedure that is inadequately reimbursed in Italy. Insufficient reimbursement may serve as disincentive to perform AF ablation, thereby limiting patient access to this treatment. Considering the healthcare system perspective, higher initial costs for ablation procedures in the short term may be offset by cost savings mainly associated with decreased hospitalizations over time.

Real-time monitoring of radiofrequency ablation and postablation assessment: accuracy of contrast-enhanced US in experimental rat liver model.

PubMed

Wu, Hanping; Wilkins, Luke R; Ziats, Nicholas P; Haaga, John R; Exner, Agata A

2014-01-01

To examine the accuracy of the unenhanced zone at contrast material-enhanced ultrasonography (US) in predicting coagulative necrosis during and 21 days after radiofrequency (RF) ablation by using radiologic-pathologic comparison. Animal studies were approved by the Institutional Animal Care and Use Committee. The livers of 28 rats underwent US-guided RF ablation. In four animals, contrast-enhanced US was performed during ablation and 2 hours and 2, 7, 14, and 21 days after ablation. The unenhanced zone area on US images was measured. DiI-labeled microbubbles were administered during ablation at 2, 4, and 6 minutes or at 2 hours and 2, 7, 14, and 21 days after ablation in the remaining 24 animals (n = 3 at each time point). One minute later, the animal was euthanized, and the ablated liver was harvested. Tissue samples were imaged to quantify total fluorescence, and NADH staining was performed on the same slice. Hematoxylin-eosin staining was also performed. The findings on fluorescence images, NADH-stained images, and hematoxylin-eosin-stained images were compared. The areas of DiI bubble-negative zones, NADH-negative zones, and lightly NADH-staining zones were measured. Data were analyzed by using one-way analysis of variance. The area of the unenhanced zone on contrast-enhanced US images increased during RF ablation and reached a maximum within 2 days after ablation. At histopathologic examination, a transition zone manifested adjacent to the coagulation zone until 2 days after ablation. The DiI-bubble negative zone on fluorescence images and the damaged zone (transition zone plus coagulation zone) on NADH-stained images increased rapidly within 2 hours after ablation, then slowly reached the maximum on day 2. The ratios of the mean areas of these two zones at hour 2 to those at day 2 were 94.6% and 95.6%, respectively. High uniformity between the damaged zone on NADH-stained images and the DiI bubble-negative zone on fluorescence images was noted at all time points. The temporary transition zone in NADH staining is partially damaged and should transition to nonviability 2 days after ablation. These results demonstrate that contrast-enhanced US can help delineate the maximum area of cell damage (to within 5% of the maximum) as early as 2 hours after ablation. Contrast-enhanced US may be a simple and accurate tool for monitoring the effects of RF ablation and quantifying the size of thermal damage after treatment. © RSNA, 2013.

Myocardium tissue ablation with high-peak-power nanosecond 1,064- and 532-nm pulsed lasers: influence of laser-induced plasma.

PubMed

Ogura, Makoto; Sato, Shunichi; Ishihara, Miya; Kawauchi, Satoko; Arai, Tunenori; Matsui, Takemi; Kurita, Akira; Kikuchi, Makoto; Ashida, Hiroshi; Obara, Minoru

2002-01-01

We investigated the mechanism and characteristics of porcine myocardium tissue ablation in vitro with nanosecond 1,064- and 532-nm pulsed lasers at laser intensities up to approximately 5.0 GW/cm(2). Particular attention was paid to study the influence of the laser-induced plasma on the ablation characteristics. The applicability of these two lasers to transmyocardial laser revascularization (TMLR) was discussed. Porcine myocardium tissue samples were irradiated with 1,064- and 532-nm, Q-switched Nd:YAG laser pulses, and the ablation depths were measured. The temporal profiles of the laser-induced optical emissions were measured with a biplanar phototube. For the ablated tissue samples, histological analysis was performed with an optical microscope and a polarization microscope. The ablation efficiency at 1,064 nm was higher than that at 532 nm. The ablation threshold at 1,064 nm (approximately 0.8 GW/cm(2)) was lower than that at 532 nm (approximately 1.6 GW/cm(2)), in spite of the lower absorption coefficient being expected at 1,064 nm. For the 1,064-nm laser-ablated tissues, thermal damage was very limited, while damage presumably caused by the mechanical effect was observed in most of the cases. For the 1,064-nm laser ablation, the ablation threshold was equal to the threshold of the laser-induced optical emission (approximately 0.8 GW/cm(2)), while for the 532-nm laser ablation, the optical emission threshold ( approximately 2.4 GW/cm(2)) was higher than the ablation threshold. We considered that for the 1,064-nm laser ablation, the tissue removal was achieved through a photodisruption process at laser intensities of > approximately 0.8 GW/cm(2). At laser intensities of > 3.0 GW/cm(2), however, the ablation efficiency decreased; this can be attributed to the absorption of incoming laser pulses by the plasma. For the 532-nm laser ablation, the tissue removal was achieved through a photothermal process at laser intensities of > approximately 1.6 GW/cm(2). At laser intensities of > 2.4 GW/cm(2), a photodisruption process may also contribute to the tissue removal, in addition to a photothermal process. With regard to the ablation rates, the 1,064-nm laser was more suitable for TMLR than the 532-nm laser. We concluded that the 1,064-nm Q-switched Nd:YAG laser would be a potential candidate for a laser source for TMLR because of possible fiber-based beam delivery, its compact structure, cost effectiveness, and easy maintenance. Animal trials, however, have to be carried out to evaluate the influence of the tissue damage. Copyright 2002 Wiley-Liss, Inc.

Ultrafast properties of femtosecond-laser-ablated GaAs and its application to terahertz optoelectronics.

PubMed

Madéo, Julien; Margiolakis, Athanasios; Zhao, Zhen-Yu; Hale, Peter J; Man, Michael K L; Zhao, Quan-Zhong; Peng, Wei; Shi, Wang-Zhou; Dani, Keshav M

2015-07-15

We report on the first terahertz (THz) emitter based on femtosecond-laser-ablated gallium arsenide (GaAs), demonstrating a 65% enhancement in THz emission at high optical power compared to the nonablated device. Counter-intuitively, the ablated device shows significantly lower photocurrent and carrier mobility. We understand this behavior in terms of n-doping, shorter carrier lifetime, and enhanced photoabsorption arising from the ablation process. Our results show that laser ablation allows for efficient and cost-effective optoelectronic THz devices via the manipulation of fundamental properties of materials.

Numerical method of carbon-based material ablation effects on aero-heating for half-sphere

NASA Astrophysics Data System (ADS)

Wang, Jiang-Feng; Li, Jia-Wei; Zhao, Fa-Ming; Fan, Xiao-Feng

2018-05-01

A numerical method of aerodynamic heating with material thermal ablation effects for hypersonic half-sphere is presented. A surface material ablation model is provided to analyze the ablation effects on aero-thermal properties and structural heat conduction for thermal protection system (TPS) of hypersonic vehicles. To demonstrate its capability, applications for thermal analysis of hypersonic vehicles using carbonaceous ceramic ablators are performed and discussed. The numerical results show the high efficiency and validation of the method developed in thermal characteristics analysis of hypersonic aerodynamic heating.

Pulsed Tm:YAG laser ablation of knee joint tissues

NASA Astrophysics Data System (ADS)

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

1992-06-01

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

From Laser Desorption to Laser Ablation of Biopolymers

NASA Astrophysics Data System (ADS)

Franz, Hillenkamp

1998-03-01

For selected indications laser ablation and cutting of biological tissues is clinical practice. Preferentially lasers with emission wavelengths in the far UV and the mid IR are used, for which tissue absorption is very high. Morphologically the ablation sites look surprisingly similar for the two wavelength ranges, despite of the very different prim y putative interaction mechanisms. Ablation depth as a function of fluence follows a sigmoidal curve. Even factors below the nominal ablation threshold superficial layers of material get removed from the surface. This is the fluence range for Matrix-Assisted Laser Desorption/Ionization (MALDI). Evidence will be presented which suggest that strong similarities exist between the desorption and ablation processes both for UV- as well as for IR-wavelengths.

Nonequilibrium Ablation of Phenolic Impregnated Carbon Ablator

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

Fast and automatic depth control of iterative bone ablation based on optical coherence tomography data

NASA Astrophysics Data System (ADS)

Fuchs, Alexander; Pengel, Steffen; Bergmeier, Jan; Kahrs, Lüder A.; Ortmaier, Tobias

2015-07-01

Laser surgery is an established clinical procedure in dental applications, soft tissue ablation, and ophthalmology. The presented experimental set-up for closed-loop control of laser bone ablation addresses a feedback system and enables safe ablation towards anatomical structures that usually would have high risk of damage. This study is based on combined working volumes of optical coherence tomography (OCT) and Er:YAG cutting laser. High level of automation in fast image data processing and tissue treatment enables reproducible results and shortens the time in the operating room. For registration of the two coordinate systems a cross-like incision is ablated with the Er:YAG laser and segmented with OCT in three distances. The resulting Er:YAG coordinate system is reconstructed. A parameter list defines multiple sets of laser parameters including discrete and specific ablation rates as ablation model. The control algorithm uses this model to plan corrective laser paths for each set of laser parameters and dynamically adapts the distance of the laser focus. With this iterative control cycle consisting of image processing, path planning, ablation, and moistening of tissue the target geometry and desired depth are approximated until no further corrective laser paths can be set. The achieved depth stays within the tolerances of the parameter set with the smallest ablation rate. Specimen trials with fresh porcine bone have been conducted to prove the functionality of the developed concept. Flat bottom surfaces and sharp edges of the outline without visual signs of thermal damage verify the feasibility of automated, OCT controlled laser bone ablation with minimal process time.

Linear ablation of right atrial free wall flutter: demonstration of bidirectional conduction block as an endpoint associated with long-term success.

PubMed

Snowdon, Richard L; Balasubramaniam, Richard; Teh, Andrew W; Haqqani, Haris M; Medi, Caroline; Rosso, Raphael; Vohra, Jitendra K; Kistler, Peter M; Morton, Joseph B; Sparks, Paul B; Kalman, Jonathan M

2010-05-01

Ablation for atypical atrial flutter (AFL) is often performed during tachycardia, with termination or noninducibility of AFL as the endpoint. Termination alone is, however, an inadequate endpoint for typical AFL ablation, where incomplete isthmus block leads to high recurrence rates. We assessed conduction block across a low lateral right atrial (RA) ablation line (LRA) from free wall scar to the inferior vena cava (IVC) or tricuspid annulus in 11 consecutive patients with atypical RA free wall flutter. LRA block was assessed following termination of AFL, by pacing from the ablation catheter in the low lateral RA posterior to the ablation line and recording the sequence and timing of activation anterior to the line with a duodecapole catheter, and vice versa for bidirectional block. LRA block resulted in a high to low activation pattern on the halo and a mean conduction time of 201 +/- 48 ms to distal halo. LRA conduction block was present in only 2 out of 6 patients after termination of AFL by ablation. Ablation was performed during sinus rhythm (SR) in 9 patients to achieve LRA conduction block. No recurrence of AFL was observed at long-term follow-up (22 +/- 12 months); 3 patients developed AF. Termination of right free wall flutter is often associated with persistent LRA conduction and additional radiofrequency ablation (RFA) in SR is usually required. Low RA pacing may be used to assess LRA conduction block and offers a robust endpoint for atypical RA free wall flutter ablation, which results in a high long-term cure rate.

Thinking outside the Box: Rotor Modulation in the Treatment of Atrial Fibrillation.

PubMed

Sehra, Ruchir; Narayan, Sanjiv M; Hummel, John

2013-01-01

Ablation for atrial fibrillation (AF) is an important and exciting therapy whose results remain suboptimal. Although most clinical trials show that ablation eliminates AF more effectively than medications, it is disappointing that the continued single procedural success remains ≈50% despite the substantial advances that have taken place in imaging, catheter positioning and energy delivery. Focal impulse and rotor modulation (FIRM), on the other hand, offers the opportunity to precisely define and then ablate patient-specific sustaining mechanisms for AF, rather than trying to eliminate all possible AF triggers. For over a decade, electrophysiologists have described cases in which AF terminates after only limited ablation - usually that cannot be explained by 'random' meandering wavelets. Indeed, recent studies from several laboratories show that all forms of clinical AF are typically 'driven' by stable electrical rotors and focal sources, not by multiple meandering waves. FIRM mapping enables an operator to place a catheter at typically 1-3 predicted sites in the atria, and with <5-10 minutes of RF ablation, terminate AF and potentially render it non-inducible. Several independent laboratories have now shown that such FIRM ablation alone can terminate or substantially slow AF in >80% of patients with persistent and paroxysmal AF and increase the single procedure rate of AF elimination from 50% with PV isolation alone to >80%. Ongoing studies hint that FIRM only ablation, enabling ablation times in the range observed for typical atrial flutter, may also achieve these high success rates without subsequent trigger ablation. This review summarizes the current state-of-the-art on FIRM mapping and ablation.

Mechanisms for the Termination of Atrial Fibrillation by Localized Ablation: Computational and Clinical Studies.

PubMed

Rappel, Wouter-Jan; Zaman, Junaid A B; Narayan, Sanjiv M

2015-12-01

Human atrial fibrillation (AF) can terminate after ablating localized regions, which supports the existence of localized rotors (spiral waves) or focal drivers. However, it is unclear why ablation near a spiral wave tip would terminate AF and not anchor reentry. We addressed this question by analyzing competing mechanisms for AF termination in numeric simulations, referenced to clinical observations. Spiral wave reentry was simulated in monodomain 2-dimensional myocyte sheets using clinically realistic rate-dependent values for repolarization and conduction. Heterogeneous models were created by introduction of parameterized variations in tissue excitability. Ablation lesions were applied as nonconducting circular regions. Models confirmed that localized ablation may anchor spiral wave reentry, producing organized tachycardias. Several mechanisms referenced to clinical observations explained termination of AF to sinus rhythm. First, lesions may create an excitable gap vulnerable to invasion by fibrillatory waves. Second, ablation of rotors in regions of low-excitability (from remodeling) produced re-entry in more excitable tissue allowing collision of wavefront and back. Conversely, ablation of rotors in high-excitability regions migrated spiral waves to less excitable tissue, where they detached to collide with nonconducting boundaries. Third, ablation may connect rotors to nonconducting anatomic orifices. Fourth, reentry through slow-conducting channels may terminate if ablation closes these channels. Limited ablation can terminate AF by several mechanisms. These data shed light on how clinical AF may be sustained in patients' atria, emphasizing heterogeneities in tissue excitability, slow-conducting channels, and obstacles that are increasingly detectable in patients and should be the focus of future translational studies. © 2015 American Heart Association, Inc.

The impact of frequency on the performance of microwave ablation.

PubMed

Sawicki, James F; Shea, Jacob D; Behdad, Nader; Hagness, Susan C

2017-02-01

The use of higher frequencies in percutaneous microwave ablation (MWA) may offer compelling interstitial antenna design advantages over the 915 MHz and 2.45 GHz frequencies typically employed in current systems. To evaluate the impact of higher frequencies on ablation performance, we conducted a comprehensive computational and experimental study of microwave absorption and tissue heating as a function of frequency. We performed electromagnetic and thermal simulations of MWA in ex vivo and in vivo porcine muscle at discrete frequencies in the 1.9-26 GHz range. Ex vivo ablation experiments were performed in the 1.9-18 GHz range. We tracked the size of the ablation zone across frequency for constant input power and ablation duration. Further, we conducted simulations to investigate antenna feed line heating as a function of frequency, input power, and cable diameter. As the frequency was increased from 1.9 to 26 GHz the resulting ablation zone dimensions decreased in the longitudinal direction while remaining relatively constant in the radial direction; thus at higher frequencies the overall ablation zone was more spherical. However, cable heating at higher frequencies became more problematic for smaller diameter cables at constant input power. Comparably sized ablation zones are achievable well above 1.9 GHz, despite increasingly localised power absorption. Specific absorption rate alone does not accurately predict ablation performance, particularly at higher frequencies where thermal diffusion plays an important role. Cable heating due to ohmic losses at higher frequencies may be controlled through judicious choices of input power and cable diameter.

Safe and rapid isolation of pulmonary veins using a novel circular ablation catheter and duty-cycled RF generator.

PubMed

Fredersdorf, Sabine; Weber, Stefan; Jilek, Clemens; Heinicke, Norbert; VON Bary, Christian; Jungbauer, Carsten; Riegger, Günter A; Hamer, Okka W; Jeron, Andreas

2009-10-01

Ablation of atrial fibrillation (AF) has been one of the most difficult and time-consuming electrophysiological procedures. Due to the rapidly increasing demand for ablation procedures, technical advances would be helpful to reduce complexity and procedure time in AF ablation. Therefore, we investigated the feasibility of a single-catheter technique for pulmonary vein (PV) isolation utilizing a decapolar catheter combined with a duty-cycled, unipolar-bipolar radiofrequency (RF) generator. AF mapping and ablation was performed in 21 consecutive patients (mean age 59 +/- 12 years, 9 males) with paroxysmal AF (n = 17) and persistent AF (n = 4). The ablation catheter was forwarded to the LA via single-transseptal puncture. All electrodes were energized in 2 to 5 applications per vein, followed by segmental RF applications, as needed, to achieve electrical isolation. To assess left atrial anatomy for purposes of catheter manipulation, and later evaluate the possibility of asymptomatic PV-stenosis, CT or MR imaging was performed both prior to ablation and at 6-month follow-up. Isolation could be achieved in 85/86 veins (99%). Procedure time for ablation was 81 +/- 13 minutes, and fluoroscopy time was 30 +/- 11 minutes. There were no procedural complications. Success rate at 6 months was 86% (18/21). MR or CT imaging excluded asymptomatic PV-stenosis. Mapping and ablation of PVs can be performed in a safe and efficient manner using a single-catheter technique, with short procedure times and minimal learning curve. Thus, this system may be of high interest not only for high volume but all centers performing AF ablation.

Efficiency of planetesimal ablation in giant planetary envelopes

NASA Astrophysics Data System (ADS)

Pinhas, Arazi; Madhusudhan, Nikku; Clarke, Cathie

2016-12-01

Observations of exoplanetary spectra are leading to unprecedented constraints on their atmospheric elemental abundances, particularly O/H, C/H, and C/O ratios. Recent studies suggest that elemental ratios could provide important constraints on formation and migration mechanisms of giant exoplanets. A fundamental assumption in such studies is that the chemical composition of the planetary envelope represents the sum-total of compositions of the accreted gas and solids during the formation history of the planet. We investigate the efficiency with which accreted planetesimals ablate in a giant planetary envelope thereby contributing to its composition rather than sinking to the core. From considerations of aerodynamic drag causing `frictional ablation' and the envelope temperature structure causing `thermal ablation', we compute mass ablations for impacting planetesimals of radii 30 m to 1 km for different compositions (ice to iron) and a wide range of velocities and impact angles, assuming spherical symmetry. Icy impactors are fully ablated in the outer envelope for a wide range of parameters. Even for Fe impactors substantial ablation occurs in the envelope for a wide range of sizes and velocities. For example, iron impactors of sizes below ˜0.5 km and velocities above ˜30 km s-1 are found to ablate by ˜60-80 per cent within the outer envelope at pressures below 103 bar due to frictional ablation alone. For deeper pressures (˜107 bar), substantial ablation happens over a wider range of parameters. Therefore, our exploratory study suggests that atmospheric abundances of volatile elements in giant planets reflect their accretion history during formation.

Radiofrequency catheter ablation versus balloon cryoablation of atrial fibrillation: markers of myocardial damage, inflammation, and thrombogenesis.

PubMed

Antolič, Bor; Pernat, Andrej; Cvijić, Marta; Žižek, David; Jan, Matevž; Šinkovec, Matjaž

2016-07-01

Evidence from animal and human studies suggests that cryoablation might be associated with a lesser inflammatory response and activation of coagulation compared with radiofrequency ablation. The study was aimed at comparing the effect of cryoballoon and radiofrequency catheter ablation of paroxysmal atrial fibrillation on markers of myocardial damage, inflammation, and activation of coagulation. Forty-one patients received either cryoballoon (n = 23) or radiofrequency (n = 18) ablation of atrial fibrillation. We measured troponin I, high-sensitivity CRP, and interleukin 6 at baseline from the cubital vein, and from the right and left atrium before and after ablation, and from the cubital vein the following day. Prothrombin fragments 1 + 2, soluble P‑selectin, and D‑dimer were measured before and after ablation from both atria. We observed higher troponin I release in the cryoballoon than in the radiofrequency group (7.01 mcg/l (interquartile range [IQR]: 5.30-9.09) vs 2.32 mcg/l (IQR: 1.45-2.98), p < 0.001). The levels of inflammatory markers (high-sensitivity CRP and interleukin 6) in the two groups were comparable, as were the levels of markers of coagulation activation. Procedure duration, fluoroscopy times, and mid-term success (23 months, IQR 7-32) of the two groups were also comparable. Cryoballoon ablation of atrial fibrillation causes more significant myocardial damage, that is, more extensive ablation lesions, compared with radiofrequency catheter ablation. However, no major differences between these two ablation techniques with regard to the inflammatory response and activation of the coagulation system were observed.

Histopomorphic Evaluation of Radiofrequency Mediated Débridement Chondroplasty

PubMed Central

Ganguly, Kumkum; McRury, Ian D; Goodwin, Peter M; Morgan, Roy E; Augé II, Wayne K

2010-01-01

The use of radiofrequency devices has become widespread for surgical ablation procedures. When ablation devices have been deployed in treatment settings requiring tissue preservation like débridement chondroplasty, adoption has been limited due to the collateral damage caused by these devices in healthy tissue surrounding the treatment site. Ex vivo radiofrequency mediated débridement chondroplasty was performed on osteochondral specimens demonstrating surface fibrillation obtained from patients undergoing knee total joint replacement. Three radiofrequency systems designed to perform débridement chondroplasty were tested each demonstrating different energy delivery methods: monopolar ablation, bipolar ablation, and non-ablation energy. Treatment outcomes were compared with control specimens as to clinical endpoint and histopomorphic characteristics. Fibrillated cartilage was removed in all specimens; however, the residual tissue remaining at the treatment site displayed significantly different characteristics attributable to radiofrequency energy delivery method. Systems that delivered ablation-based energies caused tissue necrosis and collateral damage at the treatment site including corruption of cartilage Superficial and Transitional Zones; whereas, the non-ablation system created a smooth articular surface with Superficial Zone maintenance and without chondrocyte death or tissue necrosis. The mechanism of radiofrequency energy deposition upon tissues is particularly important in treatment settings requiring tissue preservation. Ablation-based device systems can cause a worsened state of articular cartilage from that of pre-treatment. Non-ablation energy can be successful in modifying/preconditioning tissue during débridement chondroplasty without causing collateral damage. Utilizing a non-ablation radiofrequency system provides the ability to perform successful débridement chondroplasty without causing additional articular cartilage tissue damage and may allow for other cartilage intervention success. PMID:20721322

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendler, Johann Jakob, E-mail: johann.wendler@med.ovgu.de; Ricke, Jens, E-mail: jens.Ricke@med.ovgu.de; Pech, Maciej, E-mail: macej.pech@med.ovgu.de

IntroductionIt is postulated that focal IRE affords complete ablation of soft-tissue tumours while protecting the healthy peritumoral tissue. Therefore, IRE may be an interesting option for minimally invasive, kidney-tissue-sparing, non-thermal ablation of renal tumours.AimWith this current pilot study (“IRENE trial”), we present the first detailed histopathological data of IRE of human RCC followed by delayed tumour resection. The aim of this interim analysis of the first three patients was to investigate the ablation efficiency of percutaneous image-guided focal IRE in RCC, to assess whether a complete ablation of T1a RCC and tissue preservation with the NanoKnife system is possible andmore » to decide whether the ablation parameters need to be altered.MethodsFollowing resection 4 weeks after percutaneous IRE, the success of ablation and detailed histopathological description were used to check the ablation parameters.ResultsThe IRE led to a high degree of damage to the renal tumours (1 central, 2 peripheral; size range 15–17 mm). The postulated homogeneous, isomorphic damage was only partly confirmed. We found a zonal structuring of the ablation zone, negative margins and, enclosed within the ablation zone, very small tumour residues of unclear malignancy.ConclusionAccording to these initial, preliminary study results of the first three renal cases, a new zonal distribution of IRE damage was described and the curative intended, renal saving focal ablation of localised RCC below <3 cm by percutaneous IRE by the NanoKnife system appears to be possible, but needs further, systematic evaluation for this treatment method and treatment protocol.« less

Precise ablation of dental hard tissues with ultra-short pulsed lasers. Preliminary exploratory investigation on adequate laser parameters.

PubMed

Bello-Silva, Marina Stella; Wehner, Martin; Eduardo, Carlos de Paula; Lampert, Friedrich; Poprawe, Reinhart; Hermans, Martin; Esteves-Oliveira, Marcella

2013-01-01

This study aimed to evaluate the possibility of introducing ultra-short pulsed lasers (USPL) in restorative dentistry by maintaining the well-known benefits of lasers for caries removal, but also overcoming disadvantages, such as thermal damage of irradiated substrate. USPL ablation of dental hard tissues was investigated in two phases. Phase 1--different wavelengths (355, 532, 1,045, and 1,064 nm), pulse durations (picoseconds and femtoseconds) and irradiation parameters (scanning speed, output power, and pulse repetition rate) were assessed for enamel and dentin. Ablation rate was determined, and the temperature increase measured in real time. Phase 2--the most favorable laser parameters were evaluated to correlate temperature increase to ablation rate and ablation efficiency. The influence of cooling methods (air, air-water spray) on ablation process was further analyzed. All parameters tested provided precise and selective tissue ablation. For all lasers, faster scanning speeds resulted in better interaction and reduced temperature increase. The most adequate results were observed for the 1064-nm ps-laser and the 1045-nm fs-laser. Forced cooling caused moderate changes in temperature increase, but reduced ablation, being considered unnecessary during irradiation with USPL. For dentin, the correlation between temperature increase and ablation efficiency was satisfactory for both pulse durations, while for enamel, the best correlation was observed for fs-laser, independently of the power used. USPL may be suitable for cavity preparation in dentin and enamel, since effective ablation and low temperature increase were observed. If adequate laser parameters are selected, this technique seems to be promising for promoting the laser-assisted, minimally invasive approach.

Effect of nonparallel placement of in-circle bipolar radiofrequency ablation probes on volume of tissue ablated with heat sink.

PubMed

Pillai, Krishna; Al-Alem, Ihssan; Akhter, Javed; Chua, Terence C; Shehata, Mena; Morris, David L

2015-06-01

Percutaneous bipolar radiofrequency ablation (RFA) is a minimally invasive technique for treating liver tumors. It is not always possible to insert the bipolar probes parallel to each other on either side of tumor, since it restricts maneuverability away from vital structures or ablate certain tumor shape. Therefore, we investigated how nonparallel placement of probes affected ablation. Bipolar RFA in parallel and in divergent positions were submerged in tissue model (800 mL egg white) at 37°C and ablated. Temperature probes, T1 and T2 were placed 8.00 mm below the tip of the probes, T3 in between the probe coil elements and T4 and T5 at water inlet and outlet, respectively. Both models with heat sink (+HS) and without (-HS) were investigated. The mean ablated tissue volume, mass, density and height increased linearly with unit angle increase for -HS model. With +HS, a smaller increase in mean volume and mass, a slightly greater increase in mean density but a reduction in height of tissue was seen. The mean ablation time and duration of maximum temperature with +HS was slightly larger, compared with -HS, while -HS ablated at a slightly higher temperature. The heat sink present was minimal for probes in parallel position compared to nonparallel positions. Divergence from parallel insertion of bipolar RFA probes increased the mean volume, mass, and density of tissue ablated. However, the presence of large heat sinks may limit the application of this technique, when tumors border on larger vessels. © The Author(s) 2014.

Photoactive dye enhanced tissue ablation for endoscopic laser prostatectomy

NASA Astrophysics Data System (ADS)

Ahn, Minwoo; Nguyen, Trung Hau; Nguyen, Van Phuc; Oh, Junghwan; Kang, Hyun Wook

2015-02-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia with high laser power. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue ablation with low laser power. The experiment was implemented on chicken breast due to minimal optical absorption Amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532-nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm2. Light absorbance and ablation threshold were measured with UV-VIS spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with input parameter. Among the dyes, AR created the highest ablation rate of 44.2+/-0.2 μm/pulse due to higher absorbance and lower ablation threshold. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33 % reduced laser power with almost equivalent performance. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser treatment for BPH with low power application.

Comparative evaluation of three-dimensional Gd-EOB-DTPA-enhanced MR fusion imaging with CT fusion imaging in the assessment of treatment effect of radiofrequency ablation of hepatocellular carcinoma.

PubMed

Makino, Yuki; Imai, Yasuharu; Igura, Takumi; Hori, Masatoshi; Fukuda, Kazuto; Sawai, Yoshiyuki; Kogita, Sachiyo; Fujita, Norihiko; Takehara, Tetsuo; Murakami, Takamichi

2015-01-01

To assess the feasibility of fusion of pre- and post-ablation gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (Gd-EOB-DTPA-MRI) to evaluate the effects of radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC), compared with similarly fused CT images This retrospective study included 67 patients with 92 HCCs treated with RFA. Fusion images of pre- and post-RFA dynamic CT, and pre- and post-RFA Gd-EOB-DTPA-MRI were created, using a rigid registration method. The minimal ablative margin measured on fusion imaging was categorized into three groups: (1) tumor protruding outside the ablation zone boundary, (2) ablative margin 0-<5.0 mm beyond the tumor boundary, and (3) ablative margin ≥5.0 mm beyond the tumor boundary. The categorization of minimal ablative margins was compared between CT and MR fusion images. In 57 (62.0%) HCCs, treatment evaluation was possible both on CT and MR fusion images, and the overall agreement between them for the categorization of minimal ablative margin was good (κ coefficient = 0.676, P < 0.01). MR fusion imaging enabled treatment evaluation in a significantly larger number of HCCs than CT fusion imaging (86/92 [93.5%] vs. 62/92 [67.4%], P < 0.05). Fusion of pre- and post-ablation Gd-EOB-DTPA-MRI is feasible for treatment evaluation after RFA. It may enable accurate treatment evaluation in cases where CT fusion imaging is not helpful.

Bundle branch block after ablation for Wolff-Parkinson-White syndrome.

PubMed

Fuenmayor A, Abdel J; Rodríguez S, Yenny A

2013-09-20

Bundle branch block (BBB) is a difficult diagnosis in the Wolff-Parkinson-White syndrome (WPW). We investigated the clinical implications of BBB that appears after performing an accessory pathway (AP) ablation. We studied 199 patients with WPW who were submitted to AP ablation. Thirty (15%) exhibited BBB after the ablation. Twenty-two patients had right BBB and 8 had left BBB. Thirteen patients had right-sided AP and 17 had left-sided AP. They were compared with 82 similar patients without BBB after the AP ablation. Among the patients with BBB, 86.66% showed delays in the middle part of the QRS in the ECG recorded before ablation vs. 18.29% of the patients without BBB (p<0.05) (sensitivity 86%, specificity 81%, positive predictive value 67% and negative predictive value 93%). Forty-four percent of the patients with BBB had BBB morphology during orthodromic tachycardia vs. 10% of the patients without BBB (p<0.05) (sensitivity 44%, specificity 89%, positive predictive value 57% and negative predictive value 82%). No relationship was found between AP location and the site of the BBB. Ejection fraction was normal before (0.61 ± 0.03) and upon completion of follow-up (0.61 ± 0.07). BBB disappeared in 95.3% of the patients. Delays in the middle portion of the QRS may predict BBB after AP ablation. BBB after performing AP ablation is frequent, transient, benign, and not related to either the ablation lesion location or progression to structural heart disease. BBB after AP ablation may be related to cardiac memory. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Ablation for Atrial Fibrillation

PubMed Central

2006-01-01

Executive Summary Objective To review the effectiveness, safety, and costing of ablation methods to manage atrial fibrillation (AF). The ablation methods reviewed were catheter ablation and surgical ablation. Clinical Need Atrial fibrillation is characterized by an irregular, usually rapid, heart rate that limits the ability of the atria to pump blood effectively to the ventricles. Atrial fibrillation can be a primary diagnosis or it may be associated with other diseases, such as high blood pressure, abnormal heart muscle function, chronic lung diseases, and coronary heart disease. The most common symptom of AF is palpitations. Symptoms caused by decreased blood flow include dizziness, fatigue, and shortness of breath. Some patients with AF do not experience any symptoms. According to United States data, the incidence of AF increases with age, with a prevalence of 1 per 200 people aged between 50 and 60 years, and 1 per 10 people aged over 80 years. In 2004, the Institute for Clinical Evaluative Sciences (ICES) estimated that the rate of hospitalization for AF in Canada was 582.7 per 100,000 population. They also reported that of the patients discharged alive, 2.7% were readmitted within 1 year for stroke. One United States prevalence study of AF indicated that the overall prevalence of AF was 0.95%. When the results of this study were extrapolated to the population of Ontario, the prevalence of AF in Ontario is 98,758 for residents aged over 20 years. Currently, the first-line therapy for AF is medical therapy with antiarrhythmic drugs (AADs). There are several AADs available, because there is no one AAD that is effective for all patients. The AADs have critical adverse effects that can aggravate existing arrhythmias. The drug selection process frequently involves trial and error until the patient’s symptoms subside. The Technology Ablation has been frequently described as a “cure” for AF, compared with drug therapy, which controls AF but does not cure it. Ablation involves directing an energy source at cardiac tissue. For instance, radiofrequency energy uses heat to burn tissue near the source of the arrhythmia. The purpose is to create a series of scar tissue, so that the aberrant electrical pathways can no longer exist. Because the pulmonary veins are the predominant source of AF initiation, the primary goal of ablation is to isolate the pulmonary veins from the left atria through the creation of a conduction block. There are 2 methods of ablation: catheter ablation and surgical (operative) ablation. Radiofrequency energy is most commonly used for ablation. Catheter ablation involves inserting a catheter through the femoral vein to access the heart and burn abnormal foci of electrical activity by direct contact or by isolating them from the rest of the atrium. The surgical ablation is performed minimally invasively via direct visualization or with the assistance of a special scope for patients with lone AF. Review Strategy In March 2006, the following databases were searched: Cochrane Library International Agency for Health Technology Assessment (first quarter 2006), Cochrane Database of Systematic Reviews (first quarter 2006), Cochrane Central Register of Controlled Trials (first quarter 2006), MEDLINE (1966 to February 2006), MEDLINE In-Process and Other Non-indexed Citations (1966 to March 1, 2006), and EMBASE (1980 to 2006 week 9). The Medical Advisory Secretariat also searched Medscape on the Internet for recent reports on trials that were unpublished but that were presented at international conferences. In addition, the Web site Current Controlled Trials (www.controlled-trials.com) was searched for ongoing trials investigating ablation for atrial fibrillation. Search terms included: radiofrequency ablation, catheter ablation and atrial fibrillation. Summary of Findings Sixteen RCTs were identified that compared ablation methods in patients with AF. Two studies were identified that investigated first-line therapy for AF or atrial flutter. Seven other studies examined patients with drug-refractory, lone AF; and the remaining 7 RCTs compared ablation plus heart surgery to heart surgery alone in patients with drug-refractory AF and concomitant heart conditions. First-line Catheter Ablation for Atrial Fibrillation or Atrial Flutter Both studies concluded that catheter ablation was associated with significantly improved long-term freedom from arrhythmias and quality of life compared with medical therapy. These studies included different patient populations (those with AF in one pilot study, and those with atrial flutter in the other). Catheter ablation as first-line treatment is considered experimental at this time. Catheter Ablation Versus Medical Therapy in Patients With Drug-Refractory, Lone Atrial Fibrillation In this review, catheter ablation had success rates (freedom from arrhythmia) that ranged from 42% to 90% (median, 74%) in patients with drug-refractory, lone AF. All 3 of the RCTs comparing catheter ablation to medical therapy in patients with drug-refractory, lone AF found a significant improvement in terms of freedom from arrhythmia over a minimum of 12 months follow-up (P<.05). Ablation Plus Heart Surgery Versus Heart Surgery Alone in Patients With Atrial Fibrillation It is clear that patients with drug-refractory AF who are undergoing concomitant heart surgery (usually mitral valve repair or replacement) benefit significantly from surgical ablation, in terms of long-term freedom from AF, without substantial additional risk compared to open heart surgery alone. This group of patients represents about 1% of the patients with atrial fibrillation, thus the majority of the burden of AF lies within the patients with lone AF (i.e. those not requiring additional heart surgery). Conclusion Catheter ablation appears to be an effective treatment for patients with drug-refractory AF whose treatment alternatives are limited. Ablation technology is continually evolving with increasing success rates associated with the ablation procedure. PMID:23074498

The first clinical application of planning software for laparoscopic microwave thermosphere ablation of malignant liver tumours.

PubMed

Berber, Eren

2015-07-01

Liver tumour ablation is an operator-dependent procedure. The determination of the optimum needle trajectory and correct ablation parameters could be challenging. The aim of this study was to report the utility of a new, procedure planning software for microwave ablation (MWA) of liver tumours. This was a feasibility study in a pilot group of five patients with nine metastatic liver tumours who underwent laparoscopic MWA. Pre-operatively, parameters predicting the desired ablation zones were calculated for each tumour. Intra-operatively, this planning strategy was followed for both antenna placement and energy application. Post-operative 2-week computed tomography (CT) scans were performed to evaluate complete tumour destruction. The patients had an average of two tumours (range 1-4), measuring 1.9 ± 0.4 cm (range 0.9-4.4 cm). The ablation time was 7.1 ± 1.3 min (range 2.5-10 min) at 100W. There were no complications or mortality. The patients were discharged home on post-operative day (POD) 1. At 2-week CT scans, there were no residual tumours, with a complete ablation demonstrated in all lesions. This study describes and validates pre-treatment planning software for MWA of liver tumours. This software was found useful to determine precisely the ablation parameters and needle placement to create a predicted zone of ablation. © 2015 International Hepato-Pancreato-Biliary Association.

Influence of Coupled Radiation and Ablation on the Aerothermodynamic Environment of Planetary Entry Vehicles

NASA Technical Reports Server (NTRS)

Johnston, Christopher O.; Gnoffo, Peter A.; Mazaheri, Alireza

2013-01-01

A review of recently published coupled radiation and ablation capabilities involving the simulation of hypersonic flowfields relevant to Earth, Mars, or Venus entry is presented. The three fundamental mechanisms of radiation coupling are identified as radiative cooling, precursor photochemistry, and ablation-radiation interaction. The impact of these mechanisms are shown to be significant for a 3 m radius sphere entering Earth at hypothetical Mars return conditions (approximately 15 km/s). To estimate the influence precursor absorption on the radiative flux for a wide range of conditions, a simplified approach is developed that requires only the non-precursor solution. Details of a developed coupled ablation approach, which is capable of treating both massively ablating flowfields in the sublimation regime and weakly ablating diffusion Climited oxidation cases, are presented. A review of the two primary uncoupled ablation approximations, identified as the blowing correction and film coefficient approximations, is made and their impact for Earth and Mars entries is shown to be significant for recession and convective heating predictions. Fully coupled ablation and radiation simulations are presented for the Mars return sphere throughout its entire trajectory. Applying to the Mars return sphere the Pioneer- Venus heritage carbon phenolic heatshield, which has properties available in the open literature, the differences between steady state ablation and coupling to a material response code are shown to be significant.

Ultrafast dynamics of hard tissue ablation using fs-lasers.

PubMed

Domke, Matthias; Wick, Sebastian; Laible, Maike; Rapp, Stephan; Huber, Heinz P; Sroka, Ronald

2018-05-29

Several studies on hard tissue laser ablation demonstrated that ultrafast lasers enable precise material removal without thermal side effects. Although the principle ablation mechanisms have been thoroughly investigated, there are still open questions regarding the influence of material properties on transient dynamics. In this investigation, we applied pump-probe microscopy to record ablation dynamics of biomaterials with different tensile strengths (dentin, chicken bone, gallstone, kidney stones) at delay times between 1 ps and 10 μs. Transient reflectivity changes, pressure and shock wave velocities, and elastic constants were determined. The result revealed that absorption and excitation show the typical well-known transient behaviour of dielectric materials. We observed for all samples a photomechanical laser ablation process, where ultrafast expansion of the excited volume generates pressure waves leading to fragmentation around the excited region. Additionally, we identified tensile-strength-related differences in the size of ablated craters and ejected particles. The elastic constants derived were in agreement with literature values. In conclusion, pressure-wave-assisted material removal seems to be a general mechanism for hard tissue ablation with ultrafast lasers. This photomechanical process increases ablation efficiency and removes heated material, thus ultrafast laser ablation is of interest for clinical application where heating of the tissue must be avoided. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Idiopathic ventricular outflow tract arrhythmias from the great cardiac vein: challenges and risks of catheter ablation.

PubMed

Steven, D; Pott, C; Bittner, A; Sultan, A; Wasmer, K; Hoffmann, B A; Köbe, J; Drewitz, I; Milberg, P; Lueker, J; Mönnig, G; Servatius, H; Willems, S; Eckardt, L

2013-11-20

Catheter ablation for idiopathic ventricular arrhythmia is well established but epicardial origin, proximity to coronary arteries, and limited accessibility may complicate ablation from the venous system in particular from the great cardiac vein (GCV). Between April 2009 and October 2010 14 patients (56 ± 15 years; 9 male) out of a total group of 117 patients with idiopathic outflow tract tachycardias were included undergoing ablation for idiopathic VT or premature ventricular contractions (PVC) originating from GCV. All patients in whom the PVC arose from the GCV were subject to the study. In these patients angiography of the left coronary system was performed with the ablation catheter at the site of earliest activation. Successful ablation was performed in 6/14 (43%) and long-term success was achieved in 5/14 (36%) patients. In 4/14 patients (28.6%) ablation was not performed. In another 4 patients (26.7%), ablation did not abolish the PVC/VT. In the majority, the anatomical proximity to the left coronary system prohibited effective RF application. In 3 patients RF application resulted in a coronary spasm with complete regression as revealed in repeat coronary angiography. A relevant proportion idiopathic VT/PVC can safely be ablated from the GCV without significant permanent coronary artery stenosis after RF application. Our data furthermore demonstrate that damage to the coronary artery system is likely to be transient. © 2013.

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

PubMed

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

2016-07-25

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

Real-time ultrasound imaging of irreversible electroporation in a porcine liver model adequately characterizes the zone of cellular necrosis.

PubMed

Schmidt, Carl R; Shires, Peter; Mootoo, Mary

2012-02-01

  Irreversible electroporation (IRE) is a largely non-thermal method for the ablation of solid tumours. The ability of ultrasound (US) to measure the size of the IRE ablation zone was studied in a porcine liver model.   Three normal pig livers were treated in vivo with a total of 22 ablations using IRE. Ultrasound was used within minutes after ablation and just prior to liver harvest at either 6 h or 24 h after the procedure. The area of cellular necrosis was measured after staining with nitroblue tetrazolium and the percentage of cell death determined by histomorphometry.   Visible changes in the hepatic parenchyma were apparent by US after all 22 ablations using IRE. The mean maximum diameter of the ablation zone measured by US during the procedure was 20.1 ± 2.7 mm. This compared with a mean cellular necrosis zone maximum diameter of 20.3 ± 2.9 mm as measured histologically. The mean percentage of dead cells within the ablation zone was 77% at 6 h and 98% at 24 h after ablation.   Ultrasound is a useful modality for measuring the ablation zone within minutes of applying IRE to normal liver tissue. The area of parenchymal change measured by US correlates with the area of cellular necrosis. © 2011 International Hepato-Pancreato-Biliary Association.

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

NASA Astrophysics Data System (ADS)

Ali, Muddassir; Henda, Redhouane

2017-02-01

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/mm2, 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.

Dynamics of vitellogenin and vitellogenesis-inhibiting hormone levels in adult and subadult whiteleg shrimp, Litopenaeus vannamei: relation to molting and eyestalk ablation.

PubMed

Kang, Bong Jung; Okutsu, Tomoyuki; Tsutsui, Naoaki; Shinji, Junpei; Bae, Sun-Hye; Wilder, Marcy N

2014-01-01

Levels of vitellogenin (VG) and vitellogenesis-inhibiting hormone (VIH) in the whiteleg shrimp, Litopenaeus vannamei, were measured by time-resolved fluoroimmunoassay in relation to the molting cycle and ovarian maturation induced by eyestalk ablation. During the molt cycle, VG mRNA expression levels and VG concentrations showed similar patterns of fluctuation. VG levels increased significantly at early intermolt (stage C0) in adults, but not in subadults. Unilateral and bilateral eyestalk ablation increased VG levels in adults, whereas only bilateral eyestalk ablation affected subadults. VIH levels showed contrasting patterns between adults and subadults. In adults, levels were high in late postmolt adults (stage B) and then low thereafter, whereas they increased from postmolt (stage A) to intermolt (stage C0) in subadults and remained high. Unilateral eyestalk ablation increased VIH levels 10 days following ablation in adults, after which levels decreased at 20 days. VIH levels decreased from 10 to 20 days after bilateral ablation. Both unilateral and bilateral ablation led to increased VIH levels in subadults. Eyestalk ablation induced ovarian maturation, but did not reduce VIH concentrations in the hemolymph. This phenomenon was perhaps due to other crustacean hyperglycemic hormone peptides having cross-reactivity with VIH antibodies. This is the first report to quantify concentrations of VG and VIH together in L. vannamei hemolymph, and to examine their relative dynamics.

Experimental Evaluation of the Heat Sink Effect in Hepatic Microwave Ablation

PubMed Central

Ringe, Kristina I.; Lutat, Carolin; Rieder, Christian; Schenk, Andrea; Wacker, Frank; Raatschen, Hans-Juergen

2015-01-01

Purpose To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape. Materials and Methods 108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn’s multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle. Results Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15mm distance to the antenna (p<0.05). At a flow rate of 700ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively. Conclusion Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels. PMID:26222431

Persistent Atrial Fibrillation Ablation in Females: Insight from the MAGIC-AF Trial.

PubMed

Singh, Sheldon M; D'Avila, Andre; Aryana, Arash; Kim, Young-Hoon; Mangrum, J Michael; Michaud, Gregory F; Dukkipati, Srinivas R; Heist, E Kevin; Barrett, Conor D; Thorpe, Kevin E; Reddy, Vivek Y

2016-07-27

Atrial fibrillation (AF) ablation is less frequently performed in women when compared to men. There are conflicting data on the safety and efficacy of AF ablation in women. The objective of this study was to compare the clinical characteristics and outcomes in a contemporary cohort of men and women undergoing persistent AF ablation procedures. A total of 182 men and 53 women undergoing a first-ever persistent AF catheter ablation procedure in The Modified Ablation Guided by Ibutilide Use in Chronic Atrial Fibrillation (MAGIC-AF) trial were evaluated. Clinical and procedural characteristics were compared between each gender. The primary efficacy endpoint was the 1-year single procedure freedom from atrial arrhythmia off anti-arrhythmic drugs. Women undergoing catheter ablation procedures were older than men (P < 0.001). The duration of AF and associated co-morbidities were similar between both genders. Single procedure drug-free atrial arrhythmia recurrence occurred in 53% of the cohort with no difference based on gender (men = 54%, women = 53%; P = 1.0). Procedural (P = 0.04), fluoroscopic (P = 0.02), and ablation times (P = 0.003) were shorter in women compared to men. Periprocedural complications and postablation improvement in quality of life were similar between men and women. Women undergoing a first-ever persistent AF ablation procedure were older but had similar clinical outcomes and complications when compared with men. © 2016 Wiley Periodicals, Inc.

Subtotal Ablation of Parietal Epithelial Cells Induces Crescent Formation

PubMed Central

Sicking, Eva-Maria; Fuss, Astrid; Uhlig, Sandra; Jirak, Peggy; Dijkman, Henry; Wetzels, Jack; Engel, Daniel R.; Urzynicok, Torsten; Heidenreich, Stefan; Kriz, Wilhelm; Kurts, Christian; Ostendorf, Tammo; Floege, Jürgen; Smeets, Bart

2012-01-01

Parietal epithelial cells (PECs) of the renal glomerulus contribute to the formation of both cellular crescents in rapidly progressive GN and sclerotic lesions in FSGS. Subtotal transgenic ablation of podocytes induces FSGS but the effect of specific ablation of PECs is unknown. Here, we established an inducible transgenic mouse to allow subtotal ablation of PECs. Proteinuria developed during doxycycline-induced cellular ablation but fully reversed 26 days after termination of doxycycline administration. The ablation of PECs was focal, with only 30% of glomeruli exhibiting histologic changes; however, the number of PECs was reduced up to 90% within affected glomeruli. Ultrastructural analysis revealed disruption of PEC plasma membranes with cytoplasm shedding into Bowman’s space. Podocytes showed focal foot process effacement, which was the most likely cause for transient proteinuria. After >9 days of cellular ablation, the remaining PECs formed cellular extensions to cover the denuded Bowman’s capsule and expressed the activation marker CD44 de novo. The induced proliferation of PECs persisted throughout the observation period, resulting in the formation of typical cellular crescents with periglomerular infiltrate, albeit without accompanying proteinuria. In summary, subtotal ablation of PECs leads the remaining PECs to react with cellular activation and proliferation, which ultimately forms cellular crescents. PMID:22282596

Percutaneous laser ablation of benign and malignant thyroid nodules.

PubMed

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.

Predictors of cerebral microembolization during phased radiofrequency ablation of atrial fibrillation: role of the ongoing rhythm and the site of energy delivery.

PubMed

Nagy-Balo, Edina; Kiss, Alexandra; Condie, Catherine; Stewart, Mark; Edes, Istvan; Csanadi, Zoltan

2014-11-01

Pulmonary vein isolation with phased radiofrequency current and use of a pulmonary vein ablation catheter (PVAC) has recently been associated with a high incidence of clinically silent brain infarcts on diffusion-weighted magnetic resonance imaging, and a high microembolic signal (MES) count detected by transcranial Doppler. We investigated the potential effects of the ongoing rhythm and the target vein during energy delivery (ED) on MES generation during PVAC ablations. A total of 735 EDs during 48 PVAC ablations were analyzed. MES counts were recorded for each ED and time-stamped for correlation with the ongoing rhythm and the target vein for each ED. Significantly higher MES counts were observed during ablations of the left-sided as compared with the right-sided pulmonary veins (P = 0.0003). Similarly, higher MES counts were detected during EDs in atrial fibrillation as compared with sinus rhythm when the temperature was >56°C (P < 0.0001). The ongoing rhythm had no effect on the number of MESs at lower temperatures during ablation. Both the ongoing rhythm during ED and the site of ablation influence microembolus generation during PVAC ablation procedures. ©2014 Wiley Periodicals, Inc.

Real time determination of the laser ablated mass by means of electric field-perturbation measurement

NASA Astrophysics Data System (ADS)

Pacheco, P.; Álvarez, J.; Sarmiento, R.; Bredice, F.; Sánchez-Aké, C.; Villagrán-Muniz, M.; Palleschi, V.

2018-04-01

A Nd:YAG ns-pulsed laser was used to ablate Al, Cd and Zn targets, which were placed between the plates of a planar charged capacitor. The plasma generates a transient redistribution of the electrical charges on the plates that can be measured as a voltage drop across a resistor connected to the ground plate. This signal is proportional to the capacitor applied voltage, the distance between the plates and the total number of ions produced in the ablation process which in turn is related to the laser energy and the ablated mass. After a series of pulses, the targets were weighed on a thermogravimetric balance to measure the ablated mass. Our results show that the electrical signal measured on the resistor is univocally related to the ablated mass from the target. Therefore, after a proper calibration depending on the material and the experimental geometry, the electrical signal can be used for real time quantitative measurement of the ablated mass in pulsed laser generated plasma experiments. The experiments were repeated on an aluminum target, with and without the presence of the external electric field in order to determine the possible influence of the applied electric field on the ablated mass.

The Results of Ultrasonography-Guided Percutaneous Radiofrequency Ablation in Hyperparathyroid Patients in Whom Surgery Is Not Feasible

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sormaz, Ismail Cem, E-mail: icsormaz@gmail.com; Poyanlı, Arzu, E-mail: arzupoyanli@yahoo.com; Açar, Sami, E-mail: acarrsami@gmail.com

BackgroundThe aim of the study was to evaluate the results of ultrasonography (US)-guided percutaneous radiofrequency ablation (RFA) in hyperparathyroid patients who refused surgery or had high surgical risks.Patients and MethodsFive patients with hyperparathyroidism (HPT) underwent US-guided RFA for a single hyperfunctioning parathyroid lesion. Post-ablation serum calcium and parathormone (PTH) assays were performed. All patients underwent imaging studies 6 months after the ablation to visualize the post-ablation change in the size of the treated parathyroid lesions.ResultsAll patients were normocalcemic on the post-ablation 1st day and 6th month. The post-ablation PTH levels were normal in three patients but remained elevated in two patients.more » The size of the parathyroid lesion was ≥30 mm in the two patients with elevated PTH, whereas the lesion was smaller than 30 mm in those with normal post-ablation PTH values.ConclusionAlthough this is a limited case series, it demonstrates the potential feasibility of RFA for HPT. Benefits were achieved particularly in patients with small parathyroid lesions.« less

Guidance of aortic ablation using optical coherence tomography.

PubMed

Patel, Nirlep A; Li, Xingde; Stamper, Debra L; Fujimoto, James G; Brezinski, Mark E

2003-04-01

There is a significant need for an imaging modality that is capable of providing guidance for intravascular procedures, as current technologies suffer from significant limitations. In particular, laser ablation of in-stent restenosis, revascularization of chronic total occlusions, and pulmonary vein ablation could benefit from guidance. Optical coherence tomography (OCT), a recently introduced technology, is similar to ultrasound except that it measures the back-reflection of infrared light instead of sound. This study examines the ability of OCT to guide vascular laser ablation. Aorta samples underwent laser ablation using an argon laser at varying power outputs and were monitored with OCT collecting images at 4 frames. Samples were compared to the corresponding histopathology. Arterial layers could be differentiated in the images sequences. This allowed correlation of changes in the OCT image with power and duration in addition to histopathology. OCT provides real-time guidance of arterial ablation. At 4 frames, OCT was successfully able to show the microstructural changes in the vessel wall during laser ablation. Since current ablation procedures often injure surrounding tissue, the ability to minimize collateral damage to the adjoining tissue represents a useful advantage of this system. This study suggests a possible role for OCT in the guidance of intravascular procedures.

[Catheter ablation for paroxysmal atrial fibrillation: new generation cryoballoon or contact force sensing radiofrequency ablation?].

PubMed

Nagy, Zsófia; Kis, Zsuzsanna; Som, Zoltán; Földesi, Csaba; Kardos, Attila

2016-05-29

Contact force sensing radiofrequency ablation and the new generation cryoballoon ablation are prevalent techniques for the treatment of paroxysmal atrial fibrillation. The authors aimed to compare the procedural and 1-year outcome of patients after radiofrequency and cryoballoon ablation. 96 patients with paroxysmal atrial fibrillation (radiofrequency ablation: 58, cryoballoon: 38 patients; 65 men and 31 women aged 28-70 years) were enrolled. At postprocedural 1, 3, 6 and 12 months ECG, Holter monitoring and telephone interviews were performed. Procedure and fluorosocopy time were: radiofrequency ablation, 118.5 ± 15 min and 15.8 ± 6 min; cryoballoon, 73.5 ± 16 min (p<0.05) and 13.8 ± 4.,1 min (p = 0.09), respectively. One year later freedom from atrial fibrillation was achieved in 76.5% of patients who underwent radiofrequency ablation and in 81% of patients treated with cryoballoon. Temporary phrenic nerve palsy occurred in two patients and pericardial tamponade developed in one patient. In this single center study freedom from paroxysmal atrial fibrillation was similar in the two groups with significant shorter procedure time in the cryoballoon group.

A Fluorescence-Guided Laser Ablation System for Removal of Residual Cancer in a Mouse Model of Soft Tissue Sarcoma.

PubMed

Lazarides, Alexander L; Whitley, Melodi J; Strasfeld, David B; Cardona, Diana M; Ferrer, Jorge M; Mueller, Jenna L; Fu, Henry L; Bartholf DeWitt, Suzanne; Brigman, Brian E; Ramanujam, Nimmi; Kirsch, David G; Eward, William C

2016-01-01

The treatment of soft tissue sarcoma (STS) generally involves tumor excision with a wide margin. Although advances in fluorescence imaging make real-time detection of cancer possible, removal is limited by the precision of the human eye and hand. Here, we describe a novel pulsed Nd:YAG laser ablation system that, when used in conjunction with a previously described molecular imaging system, can identify and ablate cancer in vivo. Mice with primary STS were injected with the protease-activatable probe LUM015 to label tumors. Resected tissues from the mice were then imaged and treated with the laser using the paired fluorescence-imaging/ laser ablation device, generating ablation clefts with sub-millimeter precision and minimal underlying tissue damage. Laser ablation was guided by fluorescence to target tumor tissues, avoiding normal structures. The selective ablation of tumor implants in vivo improved recurrence-free survival after tumor resection in a cohort of 14 mice compared to 12 mice that received no ablative therapy. This prototype system has the potential to be modified so that it can be used during surgery to improve recurrence-free survival in patients with cancer.

Femtosecond laser ablation and nanoparticle formation in intermetallic NiAl

NASA Astrophysics Data System (ADS)

Jorgensen, David J.; Titus, Michael S.; Pollock, Tresa M.

2015-10-01

The ablation behavior of a stoichiometric intermetallic compound β-NiAl subjected to femtosecond laser pulsing in air has been investigated. The single-pulse ablation threshold for NiAl was determined to be 83 ± 4 mJ/cm2 and the transition to the high-fluence ablation regime occurred at 2.8 ± 0.3 J/cm2. Two sizes of nanoparticles consisting of Al, NiAl, Ni3Al and NiO were formed and ejected from the target during high-fluence ablation. Chemical analysis revealed that smaller nanoparticles (1-30 nm) tended to be rich in Al while larger nanoparticles (>100 nm) were lean in Al. Ablation in the low-fluence regime maintained this trend. Redeposited material and nanoparticles remaining on the surface after a single 3.7 J/cm2 pulse, one hundred 1.7 J/cm2 pulses, or one thousand 250 mJ/cm2 pulses were enriched in Al relative to the bulk target composition. Further, the surface of the irradiated high-fluence region was depleted in Al indicating that the fs laser ablation removal rate of the intermetallic constituents in this regime does not scale with the individual pure element ablation thresholds.

Micrometeoroid ablation simulated in the laboratory

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltan; Thomas, Evan W.; DeLuca, Michael; Horanyi, Mihaly; Janches, Diego; Munsat, Tobin L.; Plane, John M. C.

2016-04-01

A facility is developed to simulate the ablation of micrometeoroids in laboratory conditions, which also allows measuring the ionization probability of the ablated material. An electrostatic dust accelerator is used to generate iron and meteoric analog particles with velocities 10-50 km/s. The particles are then introduced into a cell filled with nitrogen, air or carbon dioxide gas with pressures adjustable in the 0.02 - 0.5 Torr range, where the partial or complete ablation of the particle occurs over a short distance. An array of biased electrodes is used to collect the ionized products with spatial resolution along the ablating particles' path, allowing thus the study of the temporal resolution of the process. A simple ablation model is used to match the observations. For completely ablated particles the total collected charge directly yields the ionization efficiency for. The measurements using iron particles in N2 and air are in relatively good agreement with earlier data. The measurements with CO2 and He gases, however, are significantly different from the expectations.

Radiofrequency ablation for hepatic hemangiomas: A consensus from a Chinese panel of experts

PubMed Central

Gao, Jun; Fan, Rui-Fang; Yang, Jia-Yin; Cui, Yan; Ji, Jian-Song; Ma, Kuan-Sheng; Li, Xiao-Long; Zhang, Long; Xu, Chong-Liang; Kong, Xin-Liang; Ke, Shan; Ding, Xue-Mei; Wang, Shao-Hong; Yang, Meng-Meng; Song, Jin-Jin; Zhai, Bo; Nin, Chun-Ming; Guo, Shi-Gang; Xin, Zong-Hai; Lu, Jun; Dong, Yong-Hong; Zhu, Hua-Qiang; Sun, Wen-Bing

2017-01-01

Recent studies have shown that radiofrequency (RF) ablation therapy is a safe, feasible, and effective procedure for hepatic hemangiomas, even huge hepatic hemangiomas. RF ablation has the following advantages in the treatment of hepatic hemangiomas: minimal invasiveness, definite efficacy, high safety, fast recovery, relatively simple operation, and wide applicability. It is necessary to formulate a widely accepted consensus among the experts in China who have extensive expertise and experience in the treatment of hepatic hemangiomas using RF ablation, which is important to standardize the application of RF ablation for the management of hepatic hemangiomas, regarding the selection of patients with suitable indications to receive RF ablation treatment, the technical details of the techniques, therapeutic effect evaluations, management of complications, etc. A final consensus by a Chinese panel of experts who have the expertise of using RF ablation to treat hepatic hemangiomas was reached by means of literature review, comprehensive discussion, and draft approval. PMID:29093616

Pulsed laser ablation of dental calculus in the near ultraviolet.

PubMed

Schoenly, Joshua E; Seka, Wolf; Rechmann, Peter

2014-02-01

Pulsed lasers emitting wavelengths near 400 nm can selectively ablate dental calculus without damaging underlying and surrounding sound dental hard tissue. Our results indicate that calculus ablation at this wavelength relies on the absorption of porphyrins endogenous to oral bacteria commonly found in calculus. Sub- and supragingival calculus on extracted human teeth, irradiated with 400-nm, 60-ns laser pulses at ≤8  J/cm2, exhibits a photobleached surface layer. Blue-light microscopy indicates this layer highly scatters 400-nm photons, whereas fluorescence spectroscopy indicates that bacterial porphyrins are permanently photobleached. A modified blow-off model for ablation is proposed that is based upon these observations and also reproduces our calculus ablation rates measured from laser profilometry. Tissue scattering and a stratified layering of absorbers within the calculus medium explain the gradual decrease in ablation rate from successive pulses. Depending on the calculus thickness, ablation stalling may occur at <5  J/cm2 but has not been observed above this fluence.

Laser Ablated Carbon Nanodots for Light Emission.

PubMed

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

2016-12-01

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

Material removal effect of microchannel processing by femtosecond laser

NASA Astrophysics Data System (ADS)

Zhang, Pan; Chen, Lei; Chen, Jianxiong; Tu, Yiliu

2017-11-01

Material processing using ultra-short-pulse laser is widely used in the field of micromachining, especially for the precision processing of hard and brittle materials. This paper reports a theoretical and experimental study of the ablation characteristics of a silicon wafer under micromachining using a femtosecond laser. The ablation morphology of the silicon wafer surface is surveyed by a detection test with an optical microscope. First, according to the relationship between the diameter of the ablation holes and the incident laser power, the ablation threshold of the silicon wafer is found to be 0.227 J/cm2. Second, the influence of various laser parameters on the size of the ablation microstructure is studied and the ablation morphology is analyzed. Furthermore, a mathematical model is proposed that can calculate the ablation depth per time for a given laser fluence and scanning velocity. Finally, a microchannel milling test is carried out on the micromachining center. The effectiveness and accuracy of the proposed models are verified by comparing the estimated depth to the actual measured results.

PHOTONICS AND NANOTECHNOLOGY Pulsed laser ablation of binary semiconductors: mechanisms of vaporisation and cluster formation

NASA Astrophysics Data System (ADS)

Bulgakov, A. V.; Evtushenko, A. B.; Shukhov, Yu G.; Ozerov, I.; Marin, W.

2010-12-01

Formation of small clusters during pulsed ablation of two binary semiconductors, zinc oxide and indium phosphide, in vacuum by UV, visible, and IR laser radiation is comparatively studied. The irradiation conditions favourable for generation of neutral and charged ZnnOm and InnPm clusters of different stoichiometry in the ablation products are found. The size and composition of the clusters, their expansion dynamics and reactivity are analysed by time-of-flight mass spectrometry. A particular attention is paid to the mechanisms of ZnO and InP ablation as a function of laser fluence, with the use of different ablation models. It is established that ZnO evapourates congruently in a wide range of irradiation conditions, while InP ablation leads to enrichment of the target surface with indium. It is shown that this radically different character of semiconductor ablation determines the composition of the nanostructures formed: zinc oxide clusters are mainly stoichiometric, whereas InnPm particles are significantly enriched with indium.

Paint stripping with a XeCl laser: basic research and processing techniques

NASA Astrophysics Data System (ADS)

Raiber, Armin; Plege, Burkhard; Holbein, Reinhold; Callies, Gert; Dausinger, Friedrich; Huegel, Helmut

1995-03-01

This work investigates the possibility of ablating paint from aerospace material with a XeCl- laser. The main advantage of this type of laser is the low heat generation during the ablation process. This is important when stripping thermally sensitive materials such as polymer composites. The dependence of the ablation process on energy density, pulse frequency as well as other laser parameters are presented. The results show the influence of chemical and UV artificial aging processes on ablation depth. Further, the behavior of the time-averaged transmission of the laser beam through the plasma is described as a function of the energy density. The time-varying temperature in the substrate at the point of ablation was measured during the process. An abrupt change in the temperature variation indicates the end of point ablation. This measured temperature variation is compared with the calculated temperatures, which are derived from the 1D heat equations. Finally, first results of repaintability and ablation rates will be presented.

Convergent ablation measurements with gas-filled rugby hohlraum on OMEGA

NASA Astrophysics Data System (ADS)

Casner, A.; Jalinaud, T.; Galmiche, D.

2016-03-01

Convergent ablation experiments with gas-filled rugby hohlraum were performed for the first time on the OMEGA laser facility. A time resolved 1D streaked radiography of capsule implosion is acquired in the direction perpendicular to hohlraum axis, whereas a 2D gated radiography is acquired at the same time along the hohlraum axis on a x-ray framing camera. The implosion trajectory has been measured for various kinds of uniformly doped ablators, including germanium-doped and silicon-doped polymers (CH), at two different doping fraction (2% and 4% at.). Our experiments aimed also at measuring the implosion performance of laminated capsules. A laminated ablator is constituted by thin alternate layers of un-doped and doped CH. It has been previously shown in planar geometry that laminated ablators could mitigate Rayleigh Taylor growth at ablation front. Our results confirm that the implosion of a capsule constituted with a uniform or laminated ablator behaves similarly, in accordance with post-shot simulations performed with the CEA hydrocode FCI2.

Laboratory simulations of atmospheric entry of micrometeoroids: ablation of magnesium

NASA Astrophysics Data System (ADS)

Bones, David; Gomez Martin, Juan Carlos; Diego Carrillo Sanchez, Juan; Dobson, Alexander; Plane, John

2017-04-01

We address the uncertainty in the cosmic dust input into the Earth's atmosphere by simulating the atmospheric entry of micrometeoroids in a custom built chamber, capable of heating particles to 3000 K in 2 s and able to precisely reproduce representative heating profiles. In lieu of interplanetary cosmic dust, we use a range of ground-up recovered meteorites and mineral analogues. We measure the ablation of two metals simultaneously with laser induced fluorescence (LIF). The resulting ablation profiles can be compared with the composition of the remaining, unablated particle, as determined from scanning electron microscopy-energy dispersive x-ray (SEM-EDX) analysis. Building on earlier studies of Na, Fe and Ca, here we present Mg profiles and compare them with results from our chemical ablation model (CABMOD). In general, Mg behaves as predicted, beginning to ablate steadily as one broad ablation peak once temperatures reach 2000 K. In contrast Fe, which should behave similarly to Mg, typically has two ablation peaks due to being present in two distinct phases.

Surface ablation of aluminum and silicon by ultrashort laser pulses of variable width

NASA Astrophysics Data System (ADS)

Zayarny, D. A.; Ionin, A. A.; Kudryashov, S. I.; Makarov, S. V.; Kuchmizhak, A. A.; Vitrik, O. B.; Kulchin, Yu. N.

2016-06-01

Single-shot thresholds of surface ablation of aluminum and silicon via spallative ablation by infrared (IR) and visible ultrashort laser pulses of variable width τlas (0.2-12 ps) have been measured by optical microscopy. For increasing laser pulse width τlas < 3 ps, a drastic (threefold) drop of the ablation threshold of aluminum has been observed for visible pulses compared to an almost negligible threshold variation for IR pulses. In contrast, the ablation threshold in silicon increases threefold with increasing τlas for IR pulses, while the corresponding thresholds for visible pulses remained almost constant. In aluminum, such a width-dependent decrease in ablation thresholds has been related to strongly diminished temperature gradients for pulse widths exceeding the characteristic electron-phonon thermalization time. In silicon, the observed increase in ablation thresholds has been ascribed to two-photon IR excitation, while in the visible range linear absorption of the material results in almost constant thresholds.

Experimental scaling law for mass ablation rate from a Sn plasma generated by a 1064 nm laser

NASA Astrophysics Data System (ADS)

Burdt, Russell A.; Yuspeh, Sam; Sequoia, Kevin L.; Tao, Yezheng; Tillack, Mark S.; Najmabadi, Farrokh

2009-08-01

The ablation depth in planar Sn targets irradiated with a pulsed 1064 nm laser was investigated over laser intensities from 3×1011 to 2×1012 W/cm2. The ablation depth was measured by irradiating a thin layer of Sn evaporated onto a Si wafer, and looking for signatures of Si ions in the expanding plasma with spectroscopic and particle diagnostics. It was found that ablation depth scales with laser intensity to the (5/9)th power, which is consistent with analytical models of steady-state laser ablation, as well as empirical formulae from previous studies of mass ablation rate in overlapping parameter space. In addition, the scaling of mass ablation rate with atomic number of the target as given by empirical formulae in previous studies using targets such as C and Al, are shown to remain valid for the higher atomic number of the target (Z =50) used in these experiments.

Reflectivity and laser ablation of ZrB2/Cu ultra high temperature ceramic

NASA Astrophysics Data System (ADS)

Yan, Zhenyu; Ma, Zhuang; Zhu, Shizhen; Liu, Ling; Xu, Qiang

2013-05-01

Ultra high temperature ceramics (UHTCs) were thought to be candidates for laser protective materials due to their high melting point, thermal shock and ablation resistance. The ablation behaviors of UHTCs like ZrB2 and its composite had been intensely investigated by the means of arc, plasma, oxyacetylene ablation. However, the ablation behavior under laser irradiation was still unknown by now. In this paper, the dense bulk composites of ZrB2/Cu were successfully sintered by spark plasma sintering (SPS) at 1650 degree C for 3min. The reflectivity of the composites measured by spectrophotometry achieved 60% in near infrared range and it decreased with the increasing wavelength of incident light. High intensity laser ablation was carried out on the ZrB2/Cu surface. The phase composition and microstructure changes before and after laser irradiation were characterized by X-ray diffraction and SEM respectively. The results revealed that the oxidation and melting were the main mechanisms during the ablation processing.

Analysis of ablation debris from natural and artificial iron meteorites

NASA Technical Reports Server (NTRS)

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

1977-01-01

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

Endometrial Ablation

MedlinePlus

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

A study of the effect of selected material properties on the ablation performance of artificial graphite

NASA Technical Reports Server (NTRS)

Maahs, H. G.

1972-01-01

Eighteen material properties were measured on 45 different, commercially available, artificial graphites. Ablation performance of these same graphites were also measured in a Mach 2 airstream at a stagnation pressure of 5.6 atm. Correlations were developed, where possible, between pairs of the material properties. Multiple regression equations were then formulated relating ablation performance to the various material properties, thus identifying those material properties having the strongest effect on ablation performance. These regression equations reveal that ablation performance in the present test environment depends primarily on maximum grain size, density, ash content, thermal conductivity, and mean pore radius. For optimization of ablation performance, grain size should be small, ash content low, density and thermal conductivity high, and mean pore radius large.

Image-Guided Radiofrequency Ablation (RFA) of Unresectable Hepatic Tumors Using a Triple-Spiral-Shaped Electrode Needle: Initial Experience in 34 Patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thanos, Loukas; Poulou, Loukia S., E-mail: ploukia@hotmail.co; Ziakas, Panayiotis D.

We evaluated the safety and efficacy of image-guided radiofrequency ablation (RFA) using a triple-spiral-shaped electrode needle for unresectable primary or metastatic hepatic tumors. Thirty-four patients with 46 index tumors were treated. Ablation zone, morbidity, and complications were assessed. The lesions were completely ablated with an ablative margin of about 1 cm. Five patients (14.7%) with a lesion larger than 4.5 cm had local tumor progression after 1 month and were retreated. Hemothorax, as a major complication, occurred in 1 of 34 patients (3.0%) or 1 of 46 lesions ablated (2.2%). RFA using this new electrode needle can be effective inmore » the treatment of large unresectable hepatic tumors.« less

Remote magnetic navigation to map and ablate left coronary cusp ventricular tachycardia.

PubMed

Burkhardt, J David; Saliba, Walid I; Schweikert, Robert A; Cummings, Jennifer; Natale, Andrea

2006-10-01

Premature ventricular contractions (PVCs) and ventricular tachycardia may arise from the coronary cusps. Navigation, mapping, and ablation in the coronary cusps can be challenging. Remote magnetic navigation may offer an alternative to conventional manually operated catheters. We report a case of left coronary cusp ventricular tachycardia ablation using remote magnetic navigation. Right ventricular outflow tract and coronary cusp mapping, and ablation of the left coronary cusp using a remote magnetic navigation and three-dimensional (3-D) mapping system was performed in a 28-year-old male with frequent, symptomatic PVCs and ventricular tachycardia. Successful ablation of left coronary cusp ventricular tachycardia was performed using remote magnetic navigation. Remote magnetic navigation may be used to map and ablate PVCs and ventricular tachycardia originating from the coronary cusps.

PHOTONICS AND NANOTECHNOLOGY Laser synthesis and modification of composite nanoparticles in liquids

NASA Astrophysics Data System (ADS)

Tarasenko, N. V.; Butsen, A. V.

2010-12-01

The works devoted to the formation and modification of nanoparticles using laser ablation of solid targets in liquids are reviewed. Several approaches to implement laser ablation in liquids, aimed at synthesising nanoparticles of complex composition, are considered: direct laser ablation of a target of corresponding composition, laser ablation of a combined target composed of two different metals, laser irradiation of a mixture of two or more colloidal solutions, and laser ablation in reactive liquids. The properties of two-component bimetallic systems (Ag — Cu, Ag — Au), semiconductor nanocrystals (ZnO, CdSe), chalcopyrite nanoparticles, and doped oxide nanoparticles (ZnO:Ag, Gd2O2:Tb3+) formed as a result of single- and double-pulse laser ablation in different liquids (water, ethanol, acetone, solutions of polysaccharides) are discussed.

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

NASA Astrophysics Data System (ADS)

Hu, Tao; Panhao, Tang; Xiao, Jiahua

2015-03-01

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

Laser ablation with applied magnetic field for electric propulsion

NASA Astrophysics Data System (ADS)

Batishcheva, Alla; Batishchev, Oleg; Cambier, Jean-Luc

2012-10-01

Using ultrafast lasers with tera-watt-level power allows efficient ablation and ionization of solid-density materials [1], creating dense and hot (˜100eV) plasma. We propose ablating small droplets in the magnetic nozzle configurations similar to mini-helicon plasma source [2]. Such approach may improve the momentum coupling compared to ablation of solid surfaces and facilitate plasma detachment. Results of 2D modeling of solid wire ablation in the applied magnetic field are presented and discussed. [4pt] [1] O. Batishchev et al, Ultrafast Laser Ablation for Space Propulsion, AIAA technical paper 2008-5294, -16p, 44th JPC, Hartford, 2008.[0pt] [2] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

Laser micro-etching of metal prostheses for personal identification

PubMed Central

Ganapathy, Dhanraj; Sivaswamy, Vinay; Sekhar, Prathap

2017-01-01

Denture marking techniques play a vital role in establishing personal identification in suitable clinical and forensic situations. The denture marking techniques are categorized broadly into additive and ablative methods. Additive methods involve embedding or impregnation of markers for establishing personal identity. Ablative methods involve partial removal of the denture surface thereby providing a marking for identification. Engraving and etching methods are the commonly used ablative methods. Ablative methods can be of contact and noncontact subtypes. Laser micro-etching is a precise noncontact ablative denture marking technique that could be used for prostheses-guided personal identification. PMID:28584473

Laser micro-etching of metal prostheses for personal identification.

PubMed

Ganapathy, Dhanraj; Sivaswamy, Vinay; Sekhar, Prathap

2017-01-01

Denture marking techniques play a vital role in establishing personal identification in suitable clinical and forensic situations. The denture marking techniques are categorized broadly into additive and ablative methods. Additive methods involve embedding or impregnation of markers for establishing personal identity. Ablative methods involve partial removal of the denture surface thereby providing a marking for identification. Engraving and etching methods are the commonly used ablative methods. Ablative methods can be of contact and noncontact subtypes. Laser micro-etching is a precise noncontact ablative denture marking technique that could be used for prostheses-guided personal identification.

Real-time Monitoring of Radiofrequency Ablation and Postablation Assessment: Accuracy of Contrast-enhanced US in Experimental Rat Liver Model

PubMed Central

Wu, Hanping; Wilkins, Luke R.; Ziats, Nicholas P.; Haaga, John R.

2014-01-01

Purpose To examine the accuracy of the unenhanced zone at contrast material–enhanced ultrasonography (US) in predicting coagulative necrosis during and 21 days after radiofrequency (RF) ablation by using radiologic-pathologic comparison. Materials and methods Animal studies were approved by the Institutional Animal Care and Use Committee. The livers of 28 rats underwent US-guided RF ablation. In four animals, contrast-enhanced US was performed during ablation and 2 hours and 2, 7, 14, and 21 days after ablation. The unenhanced zone area on US images was measured. DiI-labeled microbubbles were administered during ablation at 2, 4, and 6 minutes or at 2 hours and 2, 7, 14, and 21 days after ablation in the remaining 24 animals (n = 3 at each time point). One minute later, the animal was euthanized, and the ablated liver was harvested. Tissue samples were imaged to quantify total fluorescence, and NADH staining was performed on the same slice. Hematoxylin-eosin staining was also performed. The findings on fluorescence images, NADH-stained images, and hematoxylin-eosin–stained images were compared. The areas of DiI bubble–negative zones, NADH-negative zones, and lightly NADH-staining zones were measured. Data were analyzed by using one-way analysis of variance. Results The area of the unenhanced zone on contrast-enhanced US images increased during RF ablation and reached a maximum within 2 days after ablation. At histopathologic examination, a transition zone manifested adjacent to the coagulation zone until 2 days after ablation. The DiI-bubble negative zone on fluorescence images and the damaged zone (transition zone plus coagulation zone) on NADH-stained images increased rapidly within 2 hours after ablation, then slowly reached the maximum on day 2. The ratios of the mean areas of these two zones at hour 2 to those at day 2 were 94.6% and 95.6%, respectively. High uniformity between the damaged zone on NADH-stained images and the DiI bubble–negative zone on fluorescence images was noted at all time points. Conclusion The temporary transition zone in NADH staining is partially damaged and should transition to nonviability 2 days after ablation. These results demonstrate that contrast-enhanced US can help delineate the maximum area of cell damage (to within 5% of the maximum) as early as 2 hours after ablation. Contrast-enhanced US may be a simple and accurate tool for monitoring the effects of RF ablation and quantifying the size of thermal damage after treatment. © RSNA, 2013 Online supplemental material is available for this article. PMID:23912621

2D shear-wave ultrasound elastography (SWE) evaluation of ablation zone following radiofrequency ablation of liver lesions: is it more accurate?

PubMed Central

Bo, Xiao W; Li, Xiao L; Guo, Le H; Li, Dan D; Liu, Bo J; Wang, Dan; He, Ya P; Xu, Xiao H

2016-01-01

Objective: To evaluate the usefulness of two-dimensional quantitative ultrasound shear-wave elastography (2D-SWE) [i.e. virtual touch imaging quantification (VTIQ)] in assessing the ablation zone after radiofrequency ablation (RFA) for ex vivo swine livers. Methods: RFA was performed in 10 pieces of fresh ex vivo swine livers with a T20 electrode needle and 20-W output power. Conventional ultrasound, conventional strain elastography (SE) and VTIQ were performed to depict the ablation zone 0 min, 10 min, 30 min and 60 min after ablation. On VTIQ, the ablation zones were evaluated qualitatively by evaluating the shear-wave velocity (SWV) map and quantitatively by measuring the SWV. The ultrasound, SE and VTIQ results were compared against gross pathological and histopathological specimens. Results: VTIQ SWV maps gave more details about the ablation zone, the central necrotic zone appeared as red, lateral necrotic zone as green and transitional zone as light green, from inner to exterior, while the peripheral unablated liver appeared as blue. Conventional ultrasound and SE, however, only marginally depicted the whole ablation zone. The volumes of the whole ablation zone (central necrotic zone + lateral necrotic zone + transitional zone) and necrotic zone (central necrotic zone + lateral necrotic zone) measured by VTIQ showed excellent correlation (r = 0.915, p < 0.001, and 0.856, p = 0.002, respectively) with those by gross pathological specimen, whereas both conventional ultrasound and SE underestimated the volume of the whole ablation zone. The SWV values of the central necrotic zone, lateral necrotic zone, transitional zone and unablated liver parenchyma were 7.54–8.03 m s−1, 5.13–5.28 m s−1, 3.31–3.53 m s−1 and 2.11–2.21 m s−1, respectively (p < 0.001 for all the comparisons). The SWV value for each ablation zone did not change significantly at different observation times within an hour after RFA (all p > 0.05). Conclusion: The quantitative 2D-SWE of VTIQ is useful for the depiction of the ablation zone after RFA and it facilitates discrimination of different areas in the ablation zone qualitatively and quantitatively. This elastography technique might be useful for the therapeutic response evaluation instantly after RFA. Advances in knowledge: A new quantitative 2D-SWE (i.e. VTIQ) for evaluation treatment response after RFA is demonstrated. It facilitates discrimination of the different areas in the ablation zone qualitatively and quantitatively and may be useful for the therapeutic response evaluation instantly after RFA in the future. PMID:26933911

In vitro parameter optimization for spatial control of focused ultrasound ablation when using low boiling point phase-change nanoemulsions.

PubMed

Puett, Connor; Phillips, Linsey C; Sheeran, Paul S; Dayton, Paul A

2013-01-01

Phase-shift nanoemulsions (PSNEs) provide cavitation sites when the perfluorocarbon (PFC) nanodroplets (ND) are vaporized to microbubbles by acoustic energy. Their presence lowers the power required to ablate tissue by high-intensity focused ultrasound (HIFU), potentially making it a safer option for a broader range of treatment sites. However, spatial control over the ablation region can be problematic when cavitation is used to enhance heating. This study explored relationships between vaporization, ablation, and the PSNE concentration in vitro to optimize the acoustic intensity and insonation time required for spatially controlled ablation enhancement using a PSNE that included a volatile PFC component. HIFU (continuous wave at 1 MHz; insonation times of 5, 10, 15, and 20 s; cool-down times of 2, 4, and 6 s; peak negative pressures of 2, 3, and 4 MPa) was applied to albumin-acrylamide gels containing PFC agents (1:1 mix of volatile decafluorobutane and more stable dodecafluoropentane at 10(5) to 10(8) PFC ND per milliliter) or agent-free controls. Vaporization fields (microbubble clouds) were imaged by conventional ultrasound, and ablation lesions were measured directly by calipers. Controlled ablation was defined as the production of 'cigar'-shaped lesions corresponding with the acoustic focal zone. This control was considered to be lost when ablation occurred in prefocal vaporization fields having a predominantly 'tadpole' or oblong shape. Changes in the vaporization field shape and location occurred on a continuum with increasing PSNE concentration and acoustic intensity. Working with the maximum concentration-intensity combinations resulting in controlled ablation demonstrated a dose-responsive relationship between insonation time and volumes of both the vaporization fields (approximately 20 to 240 mm(3)) and the ablation lesions (1 to 135 mm(3)) within them. HIFU ablation was enhanced by this PSNE and could be achieved using intensities ≤650 W/cm(2). Although the ablation lesions were located within much larger microbubble clouds, optimum insonation times and intensities could be selected to achieve an ablation lesion of desired size and location for a given PSNE concentration. This demonstration of controllable enhancement using a PSNE that contained a volatile PFC component is another step toward developing phase-shift nanotechnology as a potential clinical tool to improve HIFU.

The Research of Feasibility and Efficacy of Radiofrequency Ablation in Treating Uterine Fibroids

PubMed Central

Luo, Xin; Shu, Shan-rong; Ma, Xue-feng; Shuai, Han-lin

2015-01-01

Abstract To explore the feasibility and efficacy of radiofrequency ablation in treating uterine fibroids. Ninety patients with multiple uterine fibroids, who had undergone hysterectomy were included in the study. After the uterus was resected, the temperature of 60, 80, 100°C were adopted to ablate the in vitro fibroid with each temperature dealing with 30 patients. Simultaneously, 5 patients were included, whose in vivo fibroid were ablated with the temperature of 100°C before the fibroids were removed after laparotomy. After the fibroids were ablated, the smooth muscle in the ablated center (group A), the ablated edge (group B) and 1 cm away from the ablated edge (group C) were taken. Then, the samples were stained with hematoxylin and eosin (HE) to examine the histopathological changes, and immunohistochemistry was performed to detect the expression of estrogen receptor (ER) and progesterone receptor (PR). After radiofrequency ablation, the ablated lesions were round, toast tan, and dry on gross appearance. There were no obvious tissue carbonization and there were distinct boundary from periphery tissue. In vitro: On automated analysis, the average optical density of ER and PR in group A, B, and C was lower than the control group (P < 0.05), and which were gradually raised with the increased distance to electrode. In the same treatment group, ER optical density was gradually decreased with the increased temperature among 3 different groups. The PR optical density was decreased with the increased temperature under different temperatures in group A and group B, there was significant difference among groups (P < 0.05). But in group C, there was no difference in PR expression among the temperature of 60, 80, and 100°C (P > 0.05). In vivo: Compared with the control group, the average optical density of ER and PR were significantly different among group A, B, and C (P < 0.05), what's more, it was gradually raised with the increased distance to electrode. After radiofrequency ablation, the tissues displayed coagulative necrosis, and decreased ER and PR expression. Radiofrequency ablation may be considered a minimally invasive alternative for those women who wish to retain their reproductive potential. Eighty degree Celsius was expected to be the optimum temperature in radiofrequency ablation treatment of uterine fibroid. PMID:26632689

Multipolar radiofrequency ablation with internally cooled electrodes: experimental study in ex vivo bovine liver with mathematic modeling.

PubMed

Clasen, Stephan; Schmidt, Diethard; Boss, Andreas; Dietz, Klaus; Kröber, Stefan M; Claussen, Claus D; Pereira, Philippe L

2006-03-01

To evaluate the size and geometry of thermally induced coagulation by using multipolar radiofrequency (RF) ablation and to determine a mathematic model to predict coagulation volume. Multipolar RF ablations (n = 80) were performed in ex vivo bovine livers by using three internally cooled bipolar applicators with two electrodes on the same shaft. Applicators were placed in a triangular array (spacing, 2-5 cm) and were activated in multipolar mode (power output, 75-225 W). The size and geometry of the coagulation zone, together with ablation time, were assessed. Mathematic functions were fitted, and the goodness of fit was assessed by using r(2). Coagulation volume, short-axis diameter, and ablation time were dependent on power output and applicator distance. The maximum zone of coagulation (volume, 324 cm(3); short-axis diameter, 8.4 cm; ablation time, 193 min) was induced with a power output of 75 W at an applicator distance of 5 cm. Coagulation volume and ablation time decreased as power output increased. Power outputs of 100-125 W at applicator distances of 2-4 cm led to a reasonable compromise between coagulation volume and ablation time. At 2 cm (100 W), coagulation volume, short-axis diameter, and ablation time were 66 cm(3), 4.5 cm, and 19 min, respectively; at 3 cm (100 W), 90 cm(3), 5.2 cm, and 22 min, respectively; at 4 cm (100 W), 132 cm(3), 6.1 cm, and 27 min, respectively; at 2 cm (125 W), 56 cm(3), 4.2 cm, and 9 min, respectively; at 3 cm (125 W), 73 cm(3), 4.9 cm, and 12 min, respectively; and at 4 cm (125 W), 103 cm(3), 5.5 cm, and 16 min, respectively. At applicator distances of 4 cm (>125 W) and 5 cm (>100 W), the zones of coagulation were not confluent. Coagulation volume (r(2) = 0.80) and RF ablation time (r(2) = 0.93) were determined by using the mathematic model. Multipolar RF ablation with three bipolar applicators may produce large volumes of confluent coagulation ex vivo. A compromise is necessary between prolonged RF ablations at lower power outputs, which produce larger volumes of coagulation, and faster RF ablations at higher power outputs, which produce smaller volumes of coagulation. Copyright RSNA, 2006.

Mechanistic Comparison of "Nearly Missed" Versus "On-Target" Rotor Ablation.

PubMed

Yamazaki, Masatoshi; Avula, Uma Mahesh R; Berenfeld, Omer; Kalifa, Jérôme

2015-08-01

This study used advanced optical mapping techniques to examine atrial fibrillation (AF) dynamics before and after 2 distinct electrogram-based ablation strategies: complex fractionated atrial electrograms (CFAEs) and DFmax/rotor ablation. Among the electrogram analytical features proposed to unravel the atrial regions that perpetuate AF, CFAEs, highest dominant frequency sites (DFmax), and, more recently, phase analysis-enabled rotor mapping have received the largest attention. Still, the mechanisms by which these approaches modulate AF dynamics and lead to AF termination are unknown. In Langendorff-perfused sheep hearts, AF was maintained by the continuous perfusion of acetylcholine and high-resolution endocardial-epicardial optical videos were recorded from the left atrial free wall and the posterior left atrium. Then, DFmax/rotor regions (n = 7), or CFAE regions harboring the highest wavebreak density (HWD) (n = 5), were targeted with a 4F ablation catheter (5 to 15 W, 30 to 60 s/point). Thereafter, we examined the changes in AF dynamics and whether AF terminated. DFmax/rotor point ablation resulted in a significant decrease in DFmax values. In 2 animals AF terminated, whereas in the remaining 5 animals the post-ablation DFmax domain remained in the vicinity of its pre-ablation location. However, after HWD/CFAEs density ablation, DFmax values did not change, AF did not terminate, and post-ablation DFmax domains relocated from the left atrial free wall to the pulmonary vein-posterior left atrium region. In another group of hearts (n = 12), we observed that upon a progressive increase in acetylcholine concentration-mimicking the acute electrophysiological changes occurring after ablation-3-dimensional rotors drifted from one atrial region to another along large gradients of myocardial thickness. "On-target" DFmax/rotor ablation leads to the annihilation of the fibrillation-driving rotor. This translates into large decreases in AF frequency or AF termination. In contrast, "nearly missed" HWD/CFAEs ablation spares the fibrillation-driving rotor, and set the stage for rotor drift along large myocardial thickness gradients. Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

1998-06-01

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

Peri-procedural interrupted oral anticoagulation for atrial fibrillation ablation: comparison of aspirin, warfarin, dabigatran, and rivaroxaban

PubMed Central

Winkle, Roger A.; Mead, R. Hardwin; Engel, Gregory; Kong, Melissa H.; Patrawala, Rob A.

2014-01-01

Aims Atrial fibrillation ablation requires peri-procedural oral anticoagulation (OAC) to prevent thromboembolic events. There are several options for OAC. We evaluate peri-procedural AF ablation complications using a variety of peri-procedural OACs. Methods and results We examined peri-procedural OAC and groin, bleeding, and thromboembolic complications for 2334 consecutive AF ablations using open irrigated-tip radiofrequency (RF) catheters. Pre-ablation OAC was warfarin in 1113 (47.7%), dabigatran 426 (18.3%), rivaroxaban 187 (8.0%), aspirin 472 (20.2%), and none 136 (5.8%). Oral anticoagulation was always interrupted and intraprocedural anticoagulation was unfractionated heparin (activated clotting time, ACT = 237 ± 26 s). Pre- and post-OAC drugs were the same for 1591 (68.2%) and were different for 743 (31.8%). Following ablation, 693 (29.7%) were treated with dabigatran and 291 (12.5%) were treated with rivaroxaban. There were no problems changing from one OAC pre-ablation to another post-ablation. Complications included 12 (0.51%) pericardial tamponades [no differences for dabigatran (P = 0.457) or rivaroxaban (P = 0.163) compared with warfarin], 12 (0.51%) groin complications [no differences for rivaroxaban (P = 0.709) and fewer for dabigatran (P = 0.041) compared with warfarin]. Only 5 of 2334 (0.21%) required blood transfusions. There were two strokes (0.086%) and no transient ischaemic attacks (TIAs) in the first 48 h post-ablation. Three additional strokes (0.13%), and two TIAs (0.086%) occurred from 48 h to 30 days. Only one stroke had a residual deficit. Compared with warfarin, the neurologic event rate was not different for dabigatran (P = 0.684) or rivaroxaban (P = 0.612). Conclusion Using interrupted OAC, low target intraprocedural ACT, and irrigated-tip RF, the rate of peri-procedural groin, haemorrhagic, and thromboembolic complications was extremely low. There were only minimal differences between OACs. Low-risk patients may remain on aspirin/no OAC pre-ablation. There are no problems changing from one OAC pre-ablation to another post-ablation. PMID:25115168

Visualization of Capsule Reentry Vehicle Heat Shield Ablation Using Naphthalene PLIF

NASA Technical Reports Server (NTRS)

Combs, Christopher S.; Clemens, Noel T.; Danehy, Paul M.

2014-01-01

The Orion Multi-Purpose Crew Vehicle (MPCV) will use an ablative heat shield and improved understanding of the ablation process would be beneficial for design purposes. Given that ablation is a multi-physics process involving heat and mass transfer, codes aiming to predict heat shield ablation are in need of experimental data pertaining to the turbulent transport of ablation products for validation. At The University of Texas at Austin, a technique is being developed that uses planar laser-induced fluorescence (PLIF) of a low-temperature sublimating ablator (naphthalene) to visualize the transport of ablation products in a supersonic flow. Since ablation at reentry temperatures can be difficult to recreate in a laboratory setting it is desirable to create a limited physics problem and simulate the ablation process at relatively low temperature conditions using naphthalene. A scaled Orion MPCV model with a solid naphthalene heat shield has been tested in a Mach 5 wind tunnel at various angles of attack in the current work. PLIF imaging reveals the distribution of the ablation products as they are transported into the heat-shield boundary layer and over the capsule shoulders into the separated shear layer and backshell recirculation region. Visualizations of the capsule shear layer using both naphthalene PLIF and Schlieren imaging compared favorably. High concentrations of naphthalene in the capsule separated flow region, intermittent turbulent structures on the heat shield surface, and interesting details of the capsule shear layer structure were observed using the naphthalene PLIF technique. The capsule shear layer was also shown to generally appear to be more turbulent at lower angles of attack. Furthermore, the PLIF signal increased steadily over the course of a run indicating that during a wind tunnel run the model heated up and the rate of naphthalene ablation increased. The shear layer showed increasing signs of turbulence over the course of a wind tunnel run as well, likely because of the combination of increased surface roughness and surface blowing rate. PLIF imaging also detected regions with a relatively low concentration of naphthalene in the capsule backshell recirculation region that are most likely the result of cross-flow-induced vortices on the capsule afterbody.

Catheter Ablation versus Thoracoscopic Surgical Ablation in Long Standing Persistent Atrial Fibrillation (CASA-AF): study protocol for a randomised controlled trial.

PubMed

Khan, Habib Rehman; Kralj-Hans, Ines; Haldar, Shouvik; Bahrami, Toufan; Clague, Jonathan; De Souza, Anthony; Francis, Darrel; Hussain, Wajid; Jarman, Julian; Jones, David Gareth; Mediratta, Neeraj; Mohiaddin, Raad; Salukhe, Tushar; Jones, Simon; Lord, Joanne; Murphy, Caroline; Kelly, Joanna; Markides, Vias; Gupta, Dhiraj; Wong, Tom

2018-02-20

Atrial fibrillation is the commonest arrhythmia which raises the risk of heart failure, thromboembolic stroke, morbidity and death. Pharmacological treatments of this condition are focused on heart rate control, rhythm control and reduction in risk of stroke. Selective ablation of cardiac tissues resulting in isolation of areas causing atrial fibrillation is another treatment strategy which can be delivered by two minimally invasive interventions: percutaneous catheter ablation and thoracoscopic surgical ablation. The main purpose of this trial is to compare the effectiveness and safety of these two interventions. Catheter Ablation versus Thoracoscopic Surgical Ablation in Long Standing Persistent Atrial Fibrillation (CASA-AF) is a prospective, multi-centre, randomised controlled trial within three NHS tertiary cardiovascular centres specialising in treatment of atrial fibrillation. Eligible adults (n = 120) with symptomatic, long-standing, persistent atrial fibrillation will be randomly allocated to either catheter ablation or thoracoscopic ablation in a 1:1 ratio. Pre-determined lesion sets will be delivered in each treatment arm with confirmation of appropriate conduction block. All patients will have an implantable loop recorder (ILR) inserted subcutaneously immediately following ablation to enable continuous heart rhythm monitoring for at least 12 months. The devices will be programmed to detect episodes of atrial fibrillation and atrial tachycardia ≥ 30 s in duration. The patients will be followed for 12 months, completing appropriate clinical assessments and questionnaires every 3 months. The ILR data will be wirelessly transmitted daily and evaluated every month for the duration of the follow-up. The primary endpoint in the study is freedom from atrial fibrillation and atrial tachycardia at the end of the follow-up period. The CASA-AF Trial is a National Institute for Health Research-funded study that will provide first-class evidence on the comparative efficacy, safety and cost-effectiveness of thoracoscopic surgical ablation and conventional percutaneous catheter ablation for long-standing persistent atrial fibrillation. In addition, the results of the trial will provide information on the effects on patients' quality of life. ISRCTN Registry, ISRCTN18250790 . Registered on 24 April 2015.

Radiofrequency ablation versus nephron-sparing surgery for small unilateral renal cell carcinoma: cost-effectiveness analysis.

PubMed

Pandharipande, Pari V; Gervais, Debra A; Mueller, Peter R; Hur, Chin; Gazelle, G Scott

2008-07-01

To evaluate the relative cost-effectiveness of percutaneous radiofrequency (RF) ablation versus nephron-sparing surgery (NSS) in patients with small (

Surgical ablation of atrial fibrillation during mitral-valve surgery.

PubMed

Gillinov, A Marc; Gelijns, Annetine C; Parides, Michael K; DeRose, Joseph J; Moskowitz, Alan J; Voisine, Pierre; Ailawadi, Gorav; Bouchard, Denis; Smith, Peter K; Mack, Michael J; Acker, Michael A; Mullen, John C; Rose, Eric A; Chang, Helena L; Puskas, John D; Couderc, Jean-Philippe; Gardner, Timothy J; Varghese, Robin; Horvath, Keith A; Bolling, Steven F; Michler, Robert E; Geller, Nancy L; Ascheim, Deborah D; Miller, Marissa A; Bagiella, Emilia; Moquete, Ellen G; Williams, Paula; Taddei-Peters, Wendy C; O'Gara, Patrick T; Blackstone, Eugene H; Argenziano, Michael

2015-04-09

Among patients undergoing mitral-valve surgery, 30 to 50% present with atrial fibrillation, which is associated with reduced survival and increased risk of stroke. Surgical ablation of atrial fibrillation has been widely adopted, but evidence regarding its safety and effectiveness is limited. We randomly assigned 260 patients with persistent or long-standing persistent atrial fibrillation who required mitral-valve surgery to undergo either surgical ablation (ablation group) or no ablation (control group) during the mitral-valve operation. Patients in the ablation group underwent further randomization to pulmonary-vein isolation or a biatrial maze procedure. All patients underwent closure of the left atrial appendage. The primary end point was freedom from atrial fibrillation at both 6 months and 12 months (as assessed by means of 3-day Holter monitoring). More patients in the ablation group than in the control group were free from atrial fibrillation at both 6 and 12 months (63.2% vs. 29.4%, P<0.001). There was no significant difference in the rate of freedom from atrial fibrillation between patients who underwent pulmonary-vein isolation and those who underwent the biatrial maze procedure (61.0% and 66.0%, respectively; P=0.60). One-year mortality was 6.8% in the ablation group and 8.7% in the control group (hazard ratio with ablation, 0.76; 95% confidence interval, 0.32 to 1.84; P=0.55). Ablation was associated with more implantations of a permanent pacemaker than was no ablation (21.5 vs. 8.1 per 100 patient-years, P=0.01). There were no significant between-group differences in major cardiac or cerebrovascular adverse events, overall serious adverse events, or hospital readmissions. The addition of atrial fibrillation ablation to mitral-valve surgery significantly increased the rate of freedom from atrial fibrillation at 1 year among patients with persistent or long-standing persistent atrial fibrillation, but the risk of implantation of a permanent pacemaker was also increased. (Funded by the National Institutes of Health and the Canadian Institutes of Health Research; ClinicalTrials.gov number, NCT00903370.).

Prophylactic Catheter Ablation for the Prevention of Defibrillator Therapy

PubMed Central

Reddy, Vivek Y.; Reynolds, Matthew R.; Neuzil, Petr; Richardson, Allison W.; Taborsky, Milos; Jongnarangsin, Krit; Kralovec, Stepan; Sediva, Lucie; Ruskin, Jeremy N.; Josephson, Mark E.

2008-01-01

BACKGROUND For patients who have a ventricular tachyarrhythmic event, implantable cardioverter–defibrillators (ICDs) are a mainstay of therapy to prevent sudden death. However, ICD shocks are painful, can result in clinical depression, and do not offer complete protection against death from arrhythmia. We designed this randomized trial to examine whether prophylactic radiofrequency catheter ablation of arrhythmogenic ventricular tissue would reduce the incidence of ICD therapy. METHODS Eligible patients with a history of a myocardial infarction underwent defibrillator implantation for spontaneous ventricular tachycardia or fibrillation. The patients did not receive antiarrhythmic drugs. Patients were randomly assigned to defibrillator implantation alone or defibrillator implantation with adjunctive catheter ablation (64 patients in each group). Ablation was performed with the use of a substrate-based approach in which the myocardial scar is mapped and ablated while the heart remains predominantly in sinus rhythm. The primary end point was survival free from any appropriate ICD therapy. RESULTS The mortality rate 30 days after ablation was zero, and there were no significant changes in ventricular function or functional class during the mean (±SD) follow-up period of 22.5±5.5 months. Twenty-one patients assigned to defibrillator implantation alone (33%) and eight patients assigned to defibrillator implantation plus ablation (12%) received appropriate ICD therapy (antitachycardia pacing or shocks) (hazard ratio in the ablation group, 0.35; 95% confidence interval, 0.15 to 0.78, P = 0.007). Among these patients, 20 in the control group (31%) and 6 in the ablation group (9%) received shocks (P = 0.003). Mortality was not increased in the group assigned to ablation as compared with the control group (9% vs. 17%, P = 0.29). CONCLUSIONS In this randomized trial, prophylactic substrate-based catheter ablation reduced the incidence of ICD therapy in patients with a history of myocardial infarction who received ICDs for the secondary prevention of sudden death. (Current Controlled Trials number, ISRCTN62488166.) PMID:18160685

Clinical Implications of Ablation of Drivers for Atrial Fibrillation: A Systematic Review and Meta-Analysis.

PubMed

Baykaner, Tina; Rogers, Albert J; Meckler, Gabriela L; Zaman, Junaid; Navara, Rachita; Rodrigo, Miguel; Alhusseini, Mahmood; Kowalewski, Christopher A B; Viswanathan, Mohan N; Narayan, Sanjiv M; Clopton, Paul; Wang, Paul J; Heidenreich, Paul A

2018-05-01

The outcomes from pulmonary vein isolation (PVI) for atrial fibrillation (AF) are suboptimal, but the benefits of additional lesion sets remain unproven. Recent studies propose ablation of AF drivers improves outcomes over PVI, yet with conflicting reports in the literature. We undertook a systematic literature review and meta-analysis to determine outcomes from ablation of AF drivers in addition to PVI or as a stand-alone procedure. Database search was done using the terms atrial fibrillation and ablation or catheter ablation and driver or rotor or focal impulse or FIRM (Focal Impulse and Rotor Modulation). We pooled data using random effects model and assessed heterogeneity with I 2 statistic. Seventeen studies met inclusion criteria, in a cohort size of 3294 patients. Adding AF driver ablation to PVI reported freedom from AF of 72.5% (confidence interval [CI], 62.1%-81.8%; P <0.01) and from all arrhythmias of 57.8% (CI, 47.5%-67.7%; P <0.01). AF driver ablation when added to PVI or as stand-alone procedure compared with controls produced an odds ratio of 3.1 (CI, 1.3-7.7; P =0.02) for freedom from AF and an odds ratio of 1.8 (CI, 1.2-2.7; P <0.01) for freedom from all arrhythmias in 4 controlled studies. AF termination rate was 40.5% (CI, 30.6%-50.9%) and predicted favorable outcome from ablation( P <0.05). In controlled studies, the addition of AF driver ablation to PVI supports the possible benefit of a combined approach of AF driver ablation and PVI in improving single-procedure freedom from all arrhythmias. However, most studies are uncontrolled and are limited by substantial heterogeneity in outcomes. Large multicenter randomized trials are needed to precisely define the benefits of adding driver ablation to PVI. © 2018 American Heart Association, Inc.

Experimental study on ablative stabilization of Rayleigh-Taylor instability of laser-irradiated targets

NASA Astrophysics Data System (ADS)

Shigemori, Keisuke; Sakaiya, Tatsuhiko; Otani, Kazuto; Fujioka, Shinsuke; Nakai, Mitsuo; Azechi, Hiroshi; Shiraga, Hiroyuki; Tamari, Yohei; Okuno, Kazuki; Sunahara, Atsushi; Nagatomo, Hideo; Murakami, Masakatsu; Nishihara, Katsunobu; Izawa, Yasukazu

2004-09-01

Hydrodynamic instabilities are key issues of the physics of inertial confinement fusion (ICF) targets. Among the instabilities, Rayleigh-Taylor (RT) instability is the most important because it gives the largest growth factor in the ICF targets. Perturbations on the laser irradiated surface grow exponentially, but the growth rate is reduced by ablation flow. The growth rate γ is written as Takabe-Betti formula: γ = [kg/(1+kL)]1/2-βkm/pa, where k is wave number of the perturbation, g is acceleration, L is density scale-length, β is a coefficient, m is mass ablation rate per unit surface, and ρa is density at the ablation front. We experimentally measured all the parameters in the formula for polystyrene (CH) targets. Experiments were done on the HIPER laser facility at Institute of Laser Engineering, Osaka University. We found that the β value in the formula is ~ 1.7, which is in good agreements with the theoretical prediction, whereas the β for certain perturbation wavelengths are larger than the prediction. This disagreement between the experiment and the theory is mainly due to the deformation of the cutoff surface, which is created by non-uniform ablation flow from the ablation surface. We also found that high-Z doped plastic targets have multiablation structure, which can reduce the RT growth rate. When a low-Z target with high-Z dopant is irradiated by laser, radiation due to the high-Z dopant creates secondary ablation front deep inside the target. Since, the secondary ablation front is ablated by x-rays, the mass ablation rate is larger than the laser-irradiated ablation surface, that is, further reduction of the RT growth is expected. We measured the RT growth rate of Br-doped polystyrene targets. The experimental results indicate that of the CHBr targets show significantly small growth rate, which is very good news for the design of the ICF targets.

Percutaneous Intraductal Radiofrequency Ablation Combined with Biliary Stent Placement for Nonresectable Malignant Biliary Obstruction Improves Stent Patency but not Survival.

PubMed

Wang, Jianfeng; Zhao, Lizhen; Zhou, Chuanguo; Gao, Kun; Huang, Qiang; Wei, Baojie; Gao, Jun

2016-04-01

Although radiofrequency (RF) ablation has been accepted as a curative treatment modality for solid organ tumors, intraductal RF ablation for malignant biliary obstruction has not been widely described. The aim of this study was to evaluate the feasibility, safety, and efficacy (in terms of stent patency and survival) of intraductal RF ablation combined with biliary stent placement for nonresectable malignant biliary obstruction. A search of the nonresectable malignant extrahepatic biliary obstruction database (179 patients) identified 18 consecutive patients who were treated with biliary intraluminal RF ablation during percutaneous transhepatic cholangiodrainage and inner stent placement (RF ablation group) and 18 patients who underwent inner stent placement without biliary intraluminal RF ablation (control group). The patients were matched for tumor type, location of obstruction, tumor stage, and Child-Pugh class status. Primary endpoints included safety, stent patency time, and survival rates. The secondary endpoint was effectiveness of the technique. The RF ablation and control groups were closely matched in terms of age, diagnosis, presence of metastases, presence of locally advanced tumor, American Society of Anesthesiologists (ASA) grade, and chemotherapy regimen (all P > 0.05). The technical success rate for both groups was 100%. The median time of stent patency in the RF ablation and control groups were 5.8 (2.8-11.5) months and 4.5 (2.4-8.0) months, respectively (Kaplan-Meier analysis: P = 0.03). The median survival times in the RF ablation and control groups were 6.1 (4.8-15.2) months and 5.8 (4.2-16.5) months, with no significant difference according to Kaplan-Meier analysis (P = 0.45). In univariate and multivariate analyses, poorer overall survival was associated with advanced age and presence of metastases (P < 0.05). Intraductal RF ablation combined with biliary stent placement for nonresectable malignant biliary obstruction is safe and feasible and effectively increases stent patency time. However, it does not improve patient survival.

Low rate of asymptomatic cerebral embolism and improved procedural efficiency with the novel pulmonary vein ablation catheter GOLD: results of the PRECISION GOLD trial.

PubMed

De Greef, Yves; Dekker, Lukas; Boersma, Lucas; Murray, Stephen; Wieczorek, Marcus; Spitzer, Stefan G; Davidson, Neil; Furniss, Steve; Hocini, Mélèze; Geller, J Christoph; Csanádi, Zoltan

2016-05-01

This prospective, multicentre study (PRECISION GOLD) evaluated the incidence of asymptomatic cerebral embolism (ACE) after pulmonary vein isolation (PVI) using a new gold multi-electrode radiofrequency (RF) ablation catheter, pulmonary vein ablation catheter (PVAC) GOLD. Also, procedural efficiency of PVAC GOLD was compared with ERACE. The ERACE study demonstrated that a low incidence of ACE can be achieved with a platinum multi-electrode RF catheter (PVAC) combined with procedural manoeuvres to reduce emboli. A total of 51 patients with paroxysmal atrial fibrillation (AF) (age 57 ± 9 years, CHA2DS2-VASc score 1.4 ± 1.4) underwent AF ablation with PVAC GOLD. Continuous oral anticoagulation using vitamin K antagonists, submerged catheter introduction, and heparinization (ACT ≥ 350 s prior to ablation) were applied. Cerebral magnetic resonance imaging (MRI) scans were performed within 48 h before and 16-72 h post-ablation. Cognitive function assessed by the Mini-Mental State Exam at baseline and 30 days post-ablation. New post-procedural ACE occurred in only 1 of 48 patients (2.1%) and was not detectable on MRI after 30 days. The average number of RF applications per patient to achieve PVI was lower in PRECISION GOLD (20.3 ± 10.0) than in ERACE (28.8 ± 16.1; P = 0.001). Further, PVAC GOLD ablations resulted in significantly fewer low-power (<3 W) ablations (15 vs. 23%, 5 vs. 10% and 2 vs. 7% in 4:1, 2:1, and 1:1 bipolar:unipolar energy modes, respectively). Mini-Mental State Exam was unchanged in all patients. Atrial fibrillation ablation with PVAC GOLD in combination with established embolic lowering manoeuvres results in a low incidence of ACE. Pulmonary vein ablation catheter GOLD demonstrates improved biophysical efficiency compared with platinum PVAC. ClinicalTrials.gov NCT01767558. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Cardiology.

Treatment of Atrial Fibrillation By The Ablation Of Localized Sources

PubMed Central

Narayan, Sanjiv M.; Krummen, David E.; Shivkumar, Kalyanam; Clopton, Paul; Rappel, Wouter-Jan; Miller, John M.

2012-01-01

Objectives We hypothesized that human atrial fibrillation (AF) may be sustained by localized sources (electrical rotors and focal impulses), whose elimination (Focal Impulse and Rotor Modulation, FIRM) may improve outcome from AF ablation. Background Catheter ablation for AF is a promising therapy, whose success is limited in part by uncertainty in the mechanisms that sustain AF. We developed a computational approach to map whether AF is sustained by several meandering waves (the prevailing hypothesis) or localized sources, then prospectively tested whether targeting patient-specific mechanisms revealed by mapping would improve AF ablation outcome. Methods We recruited 92 individuals during 107 consecutive ablation procedures for paroxysmal or persistent (72%) AF. Cases were prospectively treated, in a 2-arm 1:2 design, by ablation at sources (FIRM-Guided) followed by conventional ablation (n=36), or conventional ablation alone (n=71; FIRM-Blinded). Results Localized rotors or focal impulses were detected in 98 (97%) of 101 cases with sustained AF, each exhibiting 2.1±1.0 sources. The acute endpoint (AF termination or consistent slowing) was achieved in 86% of FIRM-guided versus 20% of FIRM-Blinded cases (p<0.001). FIRM ablation alone at the primary source terminated AF in 2.5 minutes (median; IQR 1.0–3.1). Total ablation time did not differ between groups (57.8±22.8 versus 52.1±17.8 minutes, p=0.16). During 273 days (median; IQR 132–681 days) after a single procedure, FIRM-Guided cases had higher freedom from AF (82.4% versus 44.9%; p<0.001) after a single procedure than FIRM-blinded cases with rigorous, often implanted, ECG monitoring. Adverse events did not differ between groups. CONCLUSIONS Localized electrical rotors and focal impulse sources are prevalent sustaining-mechanisms for human AF. FIRM ablation at patient-specific sources acutely terminated or slowed AF, and improved outcome. These results offer a novel mechanistic framework and treatment paradigm for AF. (ClinicalTrials.gov number, NCT01008722) PMID:22818076

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

PubMed

Jamil, Muhammad; Ng, E Y K

2015-07-01

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

Longitudinal outcomes of radiofrequency ablation versus surveillance endoscopy for Barrett's esophagus with low-grade dysplasia.

PubMed

Kahn, A; Al-Qaisi, M; Kommineni, V T; Callaway, J K; Boroff, E S; Burdick, G E; Lam-Himlin, D M; Temkit, M; Vela, M F; Ramirez, F C

2018-04-01

Radiofrequency ablation of Barrett's esophagus with low-grade dysplasia is recommended in recent American College of Gastroenterology guidelines, with endoscopic surveillance considered a reasonable alternative. Few studies have directly compared outcomes of radiofrequency ablation to surveillance and those that have are limited by short duration of follow-up. This study aims to compare the long-term effectiveness of radiofrequency ablation versus endoscopic surveillance in a large, longitudinal cohort of patients with Barrett's esophagus, and low-grade dysplasia.We conducted a retrospective analysis of patients with confirmed low-grade dysplasia at a single academic medical center from 1991 to 2014. Patients progressing to high-grade dysplasia or esophageal adenocarcinoma within one year of index LGD endoscopy were defined as missed dysplasia and excluded. Risk factors for progression were assessed via Cox proportional hazards model. Comparison of progression risk was conducted using a Kaplan-Meier analysis. Subset analyses were conducted to examine the effect of reintroducing early progressors and excluding patients diagnosed prior to the advent of ablative therapy. Of 173 total patients, 79 (45.7%) underwent radiofrequency ablation while 94 (54.3%) were untreated, with median follow up of 90 months. Seven (8.9%) patients progressed to high-grade dysplasia or adenocarcinoma despite ablation, compared with 14 (14.9%) undergoing surveillance (P = 0.44). This effect was preserved when patients diagnosed prior to the introduction of radiofrequency ablation were excluded (8.9% vs 13%, P = 0.68). Reintroduction of patients progressing within the first year of follow-up resulted in a trend toward significance for ablation versus surveillance (11.1% vs 23.8%, P = 0.053).In conclusion, progression to high-grade dysplasia or adenocarcinoma was not significantly reduced in the radiofrequency ablation cohort when compared to surveillance. Despite recent studies suggesting the superiority of radiofrequency ablation in reducing progression, diligent endoscopic surveillance may provide similar long-term outcomes.

Feasibility of zero or near zero fluoroscopy during catheter ablation procedures.

PubMed

Haegeli, Laurent M; Stutz, Linda; Mohsen, Mohammed; Wolber, Thomas; Brunckhorst, Corinna; On, Chol-Jun; Duru, Firat

2018-04-03

Awareness of risks associated with radiation exposure to patients and medical staff has significantly increased. It has been reported before that the use of advanced three-dimensional electro-anatomical mapping (EAM) system significantly reduces fluoroscopy time, however this study aimed for zero or near zero fluoroscopy ablation to assess its feasibility and safety in ablation of atrial fibrillation (AF) and other tachyarrhythmias in a "real world" experience of a single tertiary care center. This was a single-center study where ablation procedures were attempted without fluoroscopy in 34 consecutive patients with different tachyarrhythmias under the support of EAM system. When transseptal puncture (TSP) was needed, it was attempted under the guidance of intracardiac echocardiography (ICE). Among 34 patients consecutively enrolled in this study, 28 (82.4%) patients were referred for radiofrequency ablation (RFA) of AF, 3 (8.8%) patients for ablation of right ventricular outflow tract (RVOT) ventricular extrasystole (VES), 1 (2.9%) patient for ablation of atrioventricular nodal reentry tachycardia (AVNRT), 2 (5.9%) patients for typical atrial flutter ablation. In 21 (62%) patients the entire procedure was carried out without the use of fluoroscopy. Among 28 AF patients, 15 (54%) patients underwent ablation without the use of fluoroscopy and among these 15 patients, 10 (67%) patients required TSP under ICE guidance while 5 (33%) patients the catheters were introduced to left atrium through a patent foramen ovale. In 13 AF patients, fluoroscopy was only required for double TSP. The total procedure time of AF ablation was 130 ± 50 min. All patients referred for atrial flutter, AVNRT, and VES of the RVOT ablation did not require any fluoroscopy. This study demonstrates the feasibility of zero or near zero fluoroscopy procedure including TSP with the support of EAM and ICE guidance in a "real world" experience of a single tertiary care center. When fluoroscopy was required, it was limited to TSP hence keeping the radiation dose very low. .

Low rate of asymptomatic cerebral embolism and improved procedural efficiency with the novel pulmonary vein ablation catheter GOLD: results of the PRECISION GOLD trial

PubMed Central

De Greef, Yves; Dekker, Lukas; Boersma, Lucas; Murray, Stephen; Wieczorek, Marcus; Spitzer, Stefan G.; Davidson, Neil; Furniss, Steve; Hocini, Mélèze; Geller, J. Christoph; Csanádi, Zoltan

2016-01-01

Abstract Aims This prospective, multicentre study (PRECISION GOLD) evaluated the incidence of asymptomatic cerebral embolism (ACE) after pulmonary vein isolation (PVI) using a new gold multi-electrode radiofrequency (RF) ablation catheter, pulmonary vein ablation catheter (PVAC) GOLD. Also, procedural efficiency of PVAC GOLD was compared with ERACE. The ERACE study demonstrated that a low incidence of ACE can be achieved with a platinum multi-electrode RF catheter (PVAC) combined with procedural manoeuvres to reduce emboli. Methods and results A total of 51 patients with paroxysmal atrial fibrillation (AF) (age 57 ± 9 years, CHA2DS2-VASc score 1.4 ± 1.4) underwent AF ablation with PVAC GOLD. Continuous oral anticoagulation using vitamin K antagonists, submerged catheter introduction, and heparinization (ACT ≥ 350 s prior to ablation) were applied. Cerebral magnetic resonance imaging (MRI) scans were performed within 48 h before and 16–72 h post-ablation. Cognitive function assessed by the Mini-Mental State Exam at baseline and 30 days post-ablation. New post-procedural ACE occurred in only 1 of 48 patients (2.1%) and was not detectable on MRI after 30 days. The average number of RF applications per patient to achieve PVI was lower in PRECISION GOLD (20.3 ± 10.0) than in ERACE (28.8 ± 16.1; P = 0.001). Further, PVAC GOLD ablations resulted in significantly fewer low-power (<3 W) ablations (15 vs. 23%, 5 vs. 10% and 2 vs. 7% in 4:1, 2:1, and 1:1 bipolar:unipolar energy modes, respectively). Mini-Mental State Exam was unchanged in all patients. Conclusion Atrial fibrillation ablation with PVAC GOLD in combination with established embolic lowering manoeuvres results in a low incidence of ACE. Pulmonary vein ablation catheter GOLD demonstrates improved biophysical efficiency compared with platinum PVAC. Trial registration ClinicalTrials.gov NCT01767558. PMID:26826134

Robotic assistance and general anaesthesia improve catheter stability and increase signal attenuation during atrial fibrillation ablation.

PubMed

Malcolme-Lawes, Louisa C; Lim, Phang Boon; Koa-Wing, Michael; Whinnett, Zachary I; Jamil-Copley, Shahnaz; Hayat, Sajad; Francis, Darrel P; Kojodjojo, Pipin; Davies, D Wyn; Peters, Nicholas S; Kanagaratnam, Prapa

2013-01-01

Recurrent arrhythmias after ablation procedures are often caused by recovery of ablated tissue. Robotic catheter manipulation systems increase catheter tip stability which improves energy delivery and could produce more transmural lesions. We tested this assertion using bipolar voltage attenuation as a marker of lesion quality comparing robotic and manual circumferential pulmonary vein ablation for atrial fibrillation (AF). Twenty patients were randomly assigned to robotic or manual AF ablation at standard radiofrequency (RF) settings for our institution (30 W 60 s manual, 25 W 30 s robotic, R30). A separate group of 10 consecutive patients underwent robotic ablation at increased RF duration, 25 W for 60 s (R60). Lesions were marked on an electroanatomic map before and after ablation to measure distance moved and change in bipolar electrogram amplitude during RF. A total of 1108 lesions were studied (761 robotic, 347 manual). A correlation was identified between voltage attenuation and catheter movement during RF (Spearman's rho -0.929, P < 0.001). The ablation catheter was more stable during robotic RF; 2.9 ± 2.3 mm (R30) and 2.6 ± 2.2 mm (R60), both significantly less than the manual group (4.3 ± 3.0 mm, P < 0.001). Despite improved stability, there was no difference in signal attenuation between the manual and R30 group. However, there was increased signal attenuation in the R60 group (52.4 ± 19.4%) compared with manual (47.7 ± 25.4%, P = 0.01). When procedures under general anaesthesia (GA) and conscious sedation were analysed separately, the improvement in signal attenuation in the R60 group was only significant in the procedures under GA. Robotically assisted ablation has the capability to deliver greater bipolar voltage attenuation compared with manual ablation with appropriate selection of RF parameters. General anaesthesia confers additional benefits of catheter stability and greater signal attenuation. These findings may have a significant impact on outcomes from AF ablation procedures.

Randomised clinical trial of cryoballoon versus irrigated radio frequency catheter ablation for atrial fibrillation-the effect of double short versus standard exposure cryoablation duration during pulmonary vein isolation (CIRCA-DOSE): methods and rationale.

PubMed

Andrade, Jason G; Deyell, Marc W; Badra, Mariano; Champagne, Jean; Dubuc, Marc; Leong-Sit, Peter; Macle, Laurent; Novak, Paul; Roux, Jean-Francois; Sapp, John; Tang, Anthony; Verma, Atul; Wells, George A; Khairy, Paul

2017-10-05

Pulmonary vein isolation (PVI) is an effective therapy for paroxysmal atrial fibrillation (AF), but it has limitations. The two most significant recent advances have centred on the integration of real-time quantitative assessment of catheter contact force into focal radio frequency (RF) ablation catheters and the development of dedicated ablation tools capable of achieving PVI with a single ablation lesion (Arctic Front cryoballoon, Medtronic, Minneapolis, MN, USA). Although each of these holds promise for improving the clinical success of catheter ablation of AF, there has not been a rigorous comparison of these advanced ablation technologies. Moreover, the optimal duration of cryoablation (freezing time) has not been determined. Patients undergoing an initial PVI procedure for paroxysmal AF will be recruited. Patients will be randomised 1:1:1 between contact-force irrigated RF ablation, short duration cryoballoon ablation (2 min applications) and standard duration cryoballoon ablation (4 min applications). The primary outcome is time to first documented AF recurrence on implantable loop recorder. With a sample size of 111 per group and a two-sided 0.025 significance level (to account for the two main comparisons), the study will have 80% power (using a log-rank test) to detect a difference of 20% between contact force RF catheter ablation and either of the two cryoballoon ablation groups. Factoring in a 4% loss to follow-up, 116 patients per group should be randomised and followed for a year (total study population of 348). The study was approved by the University of British Columbia Office of Research (Services) Ethics Clinical Research Ethics Board. Results of the study will be submitted for publication in a peer-reviewed journal. NCT01913522; Pre-results. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Value of an old school approach: safety and long-term success of radiofrequency current catheter ablation of atrioventricular nodal reentrant tachycardia in children and young adolescents.

PubMed

Siebels, Henrike; Sohns, Christian; Nürnberg, Jan-Hendrik; Siebels, Jürgen; Langes, Klaus; Hebe, Joachim

2018-05-15

Radiofrequency current energy (RFC) ablation is still considered as the gold standard for atrioventricular nodal reentrant tachycardia (AVNRT). Success-rates for AVNRT ablation vary irrespective of the ablation technology and strategy. This study aimed to access safety, efficacy, and long-term outcome of RFC catheter ablation for the treatment of AVNRT in children and adolescents aged < 19 years with special focus on modulation versus ablation of the AV nodal slow pathway (SP). A total number of 1143 patients (pts) < 19 years were referred for invasive electrophysiological testing due to paroxysmal supraventricular tachycardia (SVT). Diagnosis of AVNRT was confirmed in 412 pts, and RFC-guided ablation was attempted in 386 pts (age 13.0 ± 3.5 years). No permanent complications were observed. RFC application resulted in SP-ablation in 171/386 (44.3%) and in SP modulation in 208/386 (53.9%) children, whereas attempts for RFC treatment failed in 7 pts. Follow-up was completed for 396/412 patients (96.1%). Within a mean follow-up period of 54.9 ± 39.7 months, in 51/379 pts (13.5%) AVNRT recurrence was observed. The median time until tachycardia recurrence was 19.5 months. No difference for AVNRT recurrence was found comparing SP ablation versus SP modulation (p > 0.05), whereas the recurrence rate was significantly higher in patients with non-inducible SVT and therefore empiric SP treatment as compared to patients with inducible AVNRT (p = 0.01). RFC-guided ablation for AVNRT in children and adolescents is safe and leads to an acceptable long-term freedom from recurrences. SP modulation and SP ablation resulted in comparable acute and long-term success rates. Late AVNRT recurrences can occur even after years of freedom from tachycardia-related symptoms.

Effects of Perfusion on Radiofrequency Ablation in Swine Kidneys1

PubMed Central

Chang, Isaac; Mikityansky, Igor; Wray-Cahen, Diane; Pritchard, William F.; Karanian, John W.; Wood, Bradford J.

2008-01-01

PURPOSE: To evaluate the effect of vascular occlusion on the size of radiofrequency (RF) ablation lesions and to evaluate embolization as an occlusion method. MATERIALS AND METHODS: The kidneys of six swine were surgically exposed. Fifteen RF ablation lesions were created in nine kidneys by using a 2-cm-tip single-needle ablation probe in varying conditions: Seven lesions were created with normal blood flow and eight were created with blood flow obstructed by means of vascular clamping (n = 5) or renal artery embolization (n = 3). The temperature, applied voltage, current, and impedance were recorded during RF ablation. Tissue-cooling curves acquired for 2 minutes immediately after the ablation were compared by using regression analysis. Lesions were bisected, and their maximum diameters were measured and compared by using analysis of variance. RESULTS: The mean diameter of ablation lesions created when blood flow was obstructed was 60% greater than that of lesions created when blood flow was normal (1.38 cm ± 0.05 [standard error of mean] vs 0.86 cm ± 0.07, P < .001). The two methods of flow obstruction yielded lesions of similar mean sizes: 1.40 cm ± 0.06 with vascular clamping and 1.33 cm ± 0.07 with embolization. The temperature at the probe tip when lesions were ablated with normal blood flow decreased more rapidly than did the temperature when lesions were ablated after flow obstruction (P < .001), but no significant differences in tissue-cooling curves between the two flow obstruction methods were observed. CONCLUSION: Obstruction of renal blood flow before and during RF ablation resulted in larger thermal lesions with potentially less variation in size compared with the lesions created with normal nonobstructed blood flow. Selective arterial embolization of the kidney vessels may be a useful adjunct to RF ablation of kidney tumors. PMID:15128994

Likelihood of Incomplete Kidney Tumor Ablation with Radio Frequency Energy: Degree of Enhancement Matters.

PubMed

Lay, Aaron H; Stewart, Jeremy; Canvasser, Noah E; Cadeddu, Jeffrey A; Gahan, Jeffrey C

2016-07-01

Larger size and clear cell histopathology are associated with worse outcomes for malignant renal tumors treated with radio frequency ablation. We hypothesize that greater tumor enhancement may be a risk factor for radio frequency ablation failure due to increased vascularity. A retrospective review of patients who underwent radio frequency ablation for renal tumors with contrast enhanced imaging available was performed. The change in Hounsfield units (HU) of the tumor from the noncontrast phase to the contrast enhanced arterial phase was calculated. Radio frequency ablation failure rates for biopsy confirmed malignant tumors were compared using the chi-squared test. Multivariate logistic analysis was performed to assess predictive variables for radio frequency ablation failure. Disease-free survival was calculated using Kaplan-Meier analysis. A total of 99 patients with biopsy confirmed malignant renal tumors and contrast enhanced imaging were identified. The incomplete ablation rate was significantly lower for tumors with enhancement less than 60 vs 60 HU or greater (0.0% vs 14.6%, p=0.005). On multivariate logistic regression analysis tumor enhancement 60 HU or greater (OR 1.14, p=0.008) remained a significant predictor of incomplete initial ablation. The 5-year disease-free survival for size less than 3 cm was 100% vs 69.2% for size 3 cm or greater (p <0.01), while 5-year disease-free survival for HU change less than 60 was 100% vs 92.4% for HU change 60 or greater (p=0.24). Biopsy confirmed malignant renal tumors, which exhibit a change in enhancement of 60 HU or greater, experience a higher rate of incomplete initial tumor ablation than tumors with enhancement less than 60 HU. Size 3 cm or greater portends worse 5-year disease-free survival after radio frequency ablation. The degree of enhancement should be considered when counseling patients before radio frequency ablation. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Radiofrequency ablation of accessory pathways in patients with the Wolff-Parkinson-White syndrome: long-term risk of mortality and coronary events.

PubMed

Wongcharoen, Wanwarang; Lin, Yenn-Jiang; Chung, Fa-Po; Chen, Yun-Yu; Chao, Tze-Fan; Chen, Pei-Chun; Chien, Kuo-Liong; Chen, Shih-Ann

2017-06-10

The long-term outcomes of radiofrequency catheter ablation (RFCA) in patients with Wolff-Parkinson-White syndrome (WPW) remain unclear. We investigated the impact of RFCA on the long-term risk of coronary events and mortality in WPW patients. We conducted a prospective cohort study utilizing the Taiwan National Health Insurance Research Database. Between 2000 and 2003, WPW patients with no prior coronary artery disease (CAD) history, aged over 18 years, who underwent RFCA were identified. WPW patients without RFCA were matched with propensity-score 1:4 matching for confounding coronary risk factors. The study outcomes were total mortality and coronary events. A total of 1524 matched non-ablated WPW patients (Group 1) and 381 ablated WPW patients (Group 2) were included. After a mean follow-up of 9.6 ± 2.9 and 10.3 ± 1.9 years, respectively, ablation group demonstrated a lower incidence of mortality compared with non-ablation group (17 vs. 26/1000 person-years, P < 0.001; adjusted HR: 0.57, 95% CI: 0.44-0.7). However, ablation group had a higher incidence of coronary events compared with non-ablation group (47 vs. 82/1000 person-years, P < 0.001; adjusted HR: 1.69, 95% CI: 1.4-2.04). The ablation-treated WPW patients had lower risk of total mortality but higher risk of coronary events than non-ablated WPW patients during the long-term follow-up. Coronary artery injury produced by RFCA may account for the increased risk of coronary events. Therefore, the ablation strategies to avoid coronary artery injury should be implemented. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Chronological changes of radiofrequency ablation zone in rabbit liver: an in vivo correlation between gross pathology and histopathology

PubMed Central

Song, Kyoung D; Rhim, Hyunchul; Kang, Tae Wook; Cha, Dong Ik; Yang, Jehoon

2017-01-01

Objective: To examine the gross pathology and histopathology of ablation zones created from radiofrequency (RF) ablation and to correlate their chronological changes. Methods: A total of 48 in vivo ablation zones (16 rabbit livers) were obtained immediately after and also 30 min, 1 h and 2 h after RF ablation and were subjected to haematoxylin and eosin (H&E) staining, nicotinamide adenine dinucleotide (NADH) diaphorase staining, terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining. Chronological changes in gross pathology and histopathology were evaluated and correlated with each other. Results: Peripheral red zones on gross pathology correlated with peripheral zones on H&E staining, lightly stained peripheral zones on NADH staining and peripheral positive zones on TUNEL staining. Central white zones on gross pathology correlated with combined central and border zones on H&E staining, central negative zones on NADH staining and combined central-positive and middle-negative zones on TUNEL staining. Boundary visibility between central white and peripheral red zones on gross pathology was significantly higher at 1 and 2 h than immediately after RF ablation. As time increased after RF ablation, visibility of the border zone on H&E staining and the grade of positively stained hepatocytes in the peripheral zone on TUNEL staining increased. Conclusion: Chronological changes in gross pathology of RF ablation zones correlated well with histopathology. The boundary between the central white and peripheral red zones tended to become clear at 1 h after RF ablation. Advances in knowledge: (1) RF ablation zones show chronological changes on gross pathology and histopathology. (2) Gross pathology and histopathology correlate well with each other. PMID:28139942

Controlling dental enamel-cavity ablation depth with optimized stepping parameters along the focal plane normal using a three axis, numerically controlled picosecond laser.

PubMed

Yuan, Fusong; Lv, Peijun; Wang, Dangxiao; Wang, Lei; Sun, Yuchun; Wang, Yong

2015-02-01

The purpose of this study was to establish a depth-control method in enamel-cavity ablation by optimizing the timing of the focal-plane-normal stepping and the single-step size of a three axis, numerically controlled picosecond laser. Although it has been proposed that picosecond lasers may be used to ablate dental hard tissue, the viability of such a depth-control method in enamel-cavity ablation remains uncertain. Forty-two enamel slices with approximately level surfaces were prepared and subjected to two-dimensional ablation by a picosecond laser. The additive-pulse layer, n, was set to 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70. A three-dimensional microscope was then used to measure the ablation depth, d, to obtain a quantitative function relating n and d. Six enamel slices were then subjected to three dimensional ablation to produce 10 cavities, respectively, with additive-pulse layer and single-step size set to corresponding values. The difference between the theoretical and measured values was calculated for both the cavity depth and the ablation depth of a single step. These were used to determine minimum-difference values for both the additive-pulse layer (n) and single-step size (d). When the additive-pulse layer and the single-step size were set 5 and 45, respectively, the depth error had a minimum of 2.25 μm, and 450 μm deep enamel cavities were produced. When performing three-dimensional ablating of enamel with a picosecond laser, adjusting the timing of the focal-plane-normal stepping and the single-step size allows for the control of ablation-depth error to the order of micrometers.

Importance of catheter contact force during irrigated radiofrequency ablation: evaluation in a porcine ex vivo model using a force-sensing catheter.

PubMed

Thiagalingam, Aravinda; D'Avila, Andre; Foley, Lori; Guerrero, J Luis; Lambert, Hendrik; Leo, Giovanni; Ruskin, Jeremy N; Reddy, Vivek Y

2010-07-01

Ablation electrode-tissue contact has been shown to be an important determinant of lesion size and safety during nonirrigated ablation but little data are available during irrigated ablation. We aimed to determine the importance of contact force during irrigated-tip ablation. Freshly excised hearts from 11 male pigs were perfused and superfused using fresh, heparinized, oxygenated swine blood in an ex vivo model. One-minute ablations were placed using one of 3 different power control strategies (impedance control-15 Omega target impedance drop, and 20 W or 30 W fixed power) and 3 different contact forces (2 g, 20 g, and 60 g) to give a grid of 9 ablation groups. The force sensing catheter (Tacticath, Endosense SA) was irrigated at 17 mL/min for all of the ablations. Of a total 101 ablations, no thrombus formation was noted but popping was seen in 17 lesions. The lesion depth and incidence of pops was 5.0 +/- 1.3 mm /0%, 5.0 +/- 1.6 mm /10% and 6.7 +/- 2.5 mm /45% for the 15 Omega, 20 W, and 30 W groups (P < 0.01), respectively, and 4.4 +/- 1.8 mm /3%, 5.8 +/- 1.6 mm /17% and 6.6 +/- 2.0 mm /37% for the 2 g, 20 g, and 60 g groups, respectively (P < 0.01). The impedance drop in the first 5 seconds was significantly correlated to catheter contact force: 9.7 +/- 9.9 Omega, 22.3 +/- 11.0 Omega, and 41.7 +/- 22.1 Omega, respectively, for the 2 g, 20 g, and 60 g groups (Pearson's r = 0.65, P < 0.01). Catheter contact force has an important impact on both ablation lesion size and the incidence of pops.

Rapid Recovery of Visual Function Associated with Blue Cone Ablation in Zebrafish

PubMed Central

Hagerman, Gordon F.; Noel, Nicole C. L.; Cao, Sylvia Y.; DuVal, Michèle G.; Oel, A. Phillip; Allison, W. Ted

2016-01-01

Hurdles in the treatment of retinal degeneration include managing the functional rewiring of surviving photoreceptors and integration of any newly added cells into the remaining second-order retinal neurons. Zebrafish are the premier genetic model for such questions, and we present two new transgenic lines allowing us to contrast vision loss and recovery following conditional ablation of specific cone types: UV or blue cones. The ablation of each cone type proved to be thorough (killing 80% of cells in each intended cone class), specific, and cell-autonomous. We assessed the loss and recovery of vision in larvae via the optomotor behavioural response (OMR). This visually mediated behaviour decreased to about 5% or 20% of control levels following ablation of UV or blue cones, respectively (P<0.05). We further assessed ocular photoreception by measuring the effects of UV light on body pigmentation, and observed that photoreceptor deficits and recovery occurred (p<0.01) with a timeline coincident to the OMR results. This corroborated and extended previous conclusions that UV cones are required photoreceptors for modulating body pigmentation, addressing assumptions that were unavoidable in previous experiments. Functional vision recovery following UV cone ablation was robust, as measured by both assays, returning to control levels within four days. In contrast, robust functional recovery following blue cone ablation was unexpectedly rapid, returning to normal levels within 24 hours after ablation. Ablation of cones led to increased proliferation in the retina, though the rapid recovery of vision following blue cone ablation was demonstrated to not be mediated by blue cone regeneration. Thus rapid visual recovery occurs following ablation of some, but not all, cone subtypes, suggesting an opportunity to contrast and dissect the sources and mechanisms of outer retinal recovery during cone photoreceptor death and regeneration. PMID:27893779

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wimmer, Thomas, E-mail: thomas.wimmer@medunigraz.at; Srimathveeravalli, Govindarajan; Gutta, Narendra

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

Nonthermal ablation in the rat brain using focused ultrasound and an ultrasound contrast agent: long-term effects

PubMed Central

McDannold, Nathan; Zhang, Yongzhi; Vykhodtseva, Natalia

2016-01-01

OBJECTIVE Thermal ablation with transcranial MRI-guided focused ultrasound (FUS) is currently under investigation as a less invasive alternative to radiosurgery and resection. A major limitation of the method is that its use is currently restricted to centrally located brain targets. The combination of FUS and a microbubble-based ultrasound contrast agent greatly reduces the ultrasound exposure level needed to ablate brain tissue and could be an effective means to increase the “treatment envelope” for FUS in the brain. This method, however, ablates tissue through a different mechanism: destruction of the microvasculature. It is not known whether nonthermal FUS ablation in substantial volumes of tissue can safely be performed without unexpected effects. The authors investigated this question by ablating volumes in the brains of normal rats. METHODS Overlapping sonications were performed in rats (n = 15) to ablate a volume in 1 hemisphere per animal. The sonications (10-msec bursts at 1 Hz for 60 seconds; peak negative pressure 0.8 MPa) were combined with the ultrasound contrast agent Optison (100 μl/kg). The rats were followed with MRI for 4–9 weeks after FUS, and the brains were examined with histological methods. RESULTS Two weeks after sonication and later, the lesions appeared as cyst-like areas in T2-weighted MR images that were stable over time. Histological examination demonstrated well-defined lesions consisting of a cyst-like cavity that remained lined by astrocytic tissue. Some white matter structures within the sonicated area were partially intact. CONCLUSIONS The results of this study indicate that nonthermal FUS ablation can be used to safely ablate tissue volumes in the brain without unexpected delayed effects. The findings are encouraging for the use of this ablation method in the brain. PMID:26848919

Medical and Interventional Outcomes in Pediatric Lone Atrial Fibrillation.

PubMed

Furst, Matthew L; Saarel, Elizabeth V; Hussein, Ayman A; Wazni, Oussama M; Tchou, Patrick; Kanj, Mohamed; Saliba, Walid I; Aziz, Peter F

2018-05-01

The goal of this study was to describe the clinical characteristics of pediatric patients with lone atrial fibrillation (LAF) and their treatment outcomes. The authors focused on patients who underwent ablation and compared the recurrence after ablation of supraventricular tachycardia substrates as presumed triggers versus pulmonary vein isolation (PVI). LAF in pediatrics is rare, and outcomes remain poorly defined. Current guidelines on ablation are based on a few small studies, and we present outcomes from the largest cohort of patients after ablation. This retrospective review included patients ≤21 years of age diagnosed with LAF from 2004 to 2015. Relevant clinical data, including recurrence rates after treatment, were tracked and analyzed with a focus on patients who underwent ablation procedures. Sixty-two patients were identified with LAF; 88% were male, and 63% were athletes. Of the 33 patients taking antiarrhythmic medication, 20 (61%) experienced recurrence. Overall, 16 patients (26%) underwent ablation: PVI in 10 (62.5%), ablation of an accessory pathway in 3 (19%), and modification of the slow atrioventricular nodal pathway in 3 (19%). One-half of patients who underwent PVI experienced documented recurrence. Of those who solely underwent supraventricular tachycardia substrate ablation, one-half also had symptomatic or documented recurrence. Ablation recurrence within this pediatric cohort was higher than expected. These recurrence rates may be demonstrative of the technical challenge of pediatric ablation compared with adult counterparts, characteristics of these patients such as athletic conditioning, or inherent differences in their atrial tissue, rendering it more refractory to substrate modification. Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Survival after Radiofrequency Ablation in 122 Patients with Inoperable Colorectal Lung Metastases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gillams, Alice, E-mail: alliesorting@gmail.com; Khan, Zahid; Osborn, Peter

2013-06-15

Purpose. To analyze the factors associated with favorable survival in patients with inoperable colorectal lung metastases treated with percutaneous image-guided radiofrequency ablation. Methods. Between 2002 and 2011, a total of 398 metastases were ablated in 122 patients (87 male, median age 68 years, range 29-90 years) at 256 procedures. Percutaneous CT-guided cool-tip radiofrequency ablation was performed under sedation/general anesthesia. Maximum tumor size, number of tumors ablated, number of procedures, concurrent/prior liver ablation, previous liver or lung resection, systemic chemotherapy, disease-free interval from primary resection to lung metastasis, and survival from first ablation were recorded prospectively. Kaplan-Meier analysis was performed, andmore » factors were compared by log rank test. Results. The initial number of metastases ablated was 2.3 (range 1-8); the total number was 3.3 (range 1-15). The maximum tumor diameter was 1.7 (range 0.5-4) cm, and the number of procedures was 2 (range 1-10). The major complication rate was 3.9 %. Overall median and 3-year survival rate were 41 months and 57 %. Survival was better in patients with smaller tumors-a median of 51 months, with 3-year survival of 64 % for tumors 2 cm or smaller versus 31 months and 44 % for tumors 2.1-4 cm (p = 0.08). The number of metastases ablated and whether the tumors were unilateral or bilateral did not affect survival. The presence of treated liver metastases, systemic chemotherapy, or prior lung resection did not affect survival. Conclusion. Three-year survival of 57 % in patients with inoperable colorectal lung metastases is better than would be expected with chemotherapy alone. Patients with inoperable but small-volume colorectal lung metastases should be referred for ablation.« less

Use of Oral Steroid and its Effects on Atrial Fibrillation Recurrence and Inflammatory Cytokines Post Ablation - The Steroid AF Study.

PubMed

Iskandar, Sandia; Reddy, Madhu; Afzal, Muhammad R; Rajasingh, Johnson; Atoui, Moustapha; Lavu, Madhav; Atkins, Donita; Bommana, Sudha; Umbarger, Linda; Jaeger, Misty; Pimentel, Rhea; Dendi, Raghuveer; Emert, Martin; Turagam, Mohit; Di Biase, Luigi; Natale, Andrea; Lakkireddy, Dhanunjaya

2017-01-01

Use of corticosteroids before and after atrial fibrillation (AF) ablation can decrease acute inflammation and reduce AF recurrence. To assess the efficacy of oral prednisone in improving the outcomes of pulmonary vein isolation with radiofrequency ablation and its effect on inflammatory cytokine. A total of 60 patients with paroxysmal AF undergoing radiofrequency ablation were randomized (1:1) to receive either 3 doses of 60 mg daily of oral prednisone or a placebo. Inflammatory cytokine levels (TNF-α, IL-1, IL6, IL-8) were measured at baseline, prior to ablation, immediately after ablation, and 24 hours post ablation. Patients underwent 30 day event monitoring at 3 months, 6 months and 12 months post procedure. Immediate post ablation levels of inflammatory cytokines were lower in the steroid group when compared to the placebo group; IL-6: 9.0 ±7 vs 15.8 ±13 p=0.031; IL-8: 10.5 ±9 vs 15.3 ±8; p=0.047 respectively. Acute PV reconnection rates during the procedure (7/23% vs 10/36%; p = 0.39), and RF ablation time (51±13 vs 56±11 min, p = 0.11) trended to be lower in the placebo group than the steroid group. There was no difference in the incidence of early recurrence of AF during the blanking period and freedom from AF off AAD at 12 months between both groups (5/17% vs 8/27%; p = 0.347 and 21/70% vs 18/60%; p=0.417 in placebo and steroid groups respectively). Although oral corticosteroids have significant effect in lowering certain cytokines, it did not impact the clinical outcomes of AF ablation.

Microwaves create larger ablations than radiofrequency when controlled for power in ex vivo tissue.

PubMed

Andreano, A; Huang, Yu; Meloni, M Franca; Lee, Fred T; Brace, Christopher

2010-06-01

To compare ablation zones created with equal amounts of 2.45 GHz microwave and 480 kHz radiofrequency (RF) energy in ex vivo liver and lung. A total of 38 ablations were performed in ex vivo liver and lung for 10 min each. Nineteen RF ablations (nine liver, ten lung) were performed with a 480 kHz system (200 W max, impedance-based pulsing) and cooled electrode while measuring the average RF power applied. Nineteen microwave ablations (nine liver, ten lung) were then created using a cooled triaxial antenna to deliver 2.45 GHz at the same power level as in RF experiments. Ablation zones were then sectioned and measured for minimum, maximum and mean diameters, and circularity. Measurements were compared using t-tests, with P < 0.05 indicating statistical significance. Mean diameters of microwave ablations were greater than RF ablations in both liver and lung (4.4 +/- 0.3 vs 3.3 +/- 0.2 cm in liver; 2.45 +/- 0.3 vs 1.6 +/- 0.5 cm in lungs; P < 0.0005 all comparisons). There was no significant difference in the mean power applied during microwave or RF ablations in either organ (54.44 +/- 1.71 W vs 56.4 +/- 6.7 W in liver, P > 0.05; 40 +/- 0.95 W vs 44.9 +/- 7.1 W in lung, P > 0.05). Using a single cooled applicator, microwave energy at 2.45 GHz produces larger ablations than an equivalent amount of 480 kHz RF energy in normal liver and lung. This was more apparent in lung, likely due to the high baseline impedance which limits RF, but not microwave power delivery.

Magnetic versus manual catheter navigation for ablation of free wall accessory pathways in children.

PubMed

Kim, Jeffrey J; Macicek, Scott L; Decker, Jamie A; Kertesz, Naomi J; Friedman, Richard A; Cannon, Bryan C

2012-08-01

Transcatheter ablation of accessory pathway (AP)-mediated tachycardia is routinely performed in children. Little data exist regarding the use of magnetic navigation (MN) and its potential benefits for ablation of AP-mediated tachycardia in this population. We performed a retrospective review of prospectively gathered data in children undergoing radiofrequency ablation at our institution since the installation of MN (Stereotaxis Inc, St. Louis, MO) in March 2009. The efficacy and safety between an MN-guided approach and standard manual techniques for mapping and ablation of AP-mediated tachycardia were compared. During the 26-month study period, 145 patients underwent radiofrequency ablation for AP-mediated tachycardia. Seventy-three patients were ablated with MN and 72 with a standard manual approach. There were no significant differences in demographic factors between the 2 groups with a mean cohort age of 13.1±4.0 years. Acute success rates were equivalent with 68 of 73 (93.2%) patients in the MN group being successfully ablated versus 68 of 72 (94.4%) patients in the manual group (P=0.889). During a median follow-up of 21.4 months, there were no recurrences in the MN group and 2 recurrences in the manual group (P=0.388). There were no differences in time to effect, number of lesions delivered, or average ablation power. There was also no difference in total procedure time, but fluoroscopy time was significantly reduced in the MN group at 14.0 (interquartile range, 3.8-23.9) minutes compared with the manual group at 28.1 (interquartile range, 15.3-47.3) minutes (P<0.001). There were no complications in either group. MN is a safe and effective approach to ablate AP-mediated tachycardia in children.

Pulmonary Microwave Ablation Near the Heart: Antenna Positioning Can Mitigate Cardiac Complications in a Porcine Model

PubMed Central

Nocerino, Elisabetta; Mason, Peter J.; Schwahn, Denise J.; Hetzel, Scott; Turnquist, Alyssa M.; Lee, Fred T.; Brace, Christopher L.

2017-01-01

Purpose To determine how close to the heart pulmonary microwave ablation can be performed without causing cardiac tissue injury or significant arrhythmia. Materials and Methods The study was performed with approval from the institutional animal care and use committee. Computed tomographic fluoroscopically guided microwave ablation of the lung was performed in 12 swine. Antennas were randomized to either parallel (180° ± 20°) or perpendicular (90° ± 20°) orientation relative to the heart surface and to distances of 0–10 mm from the heart. Ablations were performed at 65 W for 5 minutes or until a significant arrhythmia (asystole, heart block, bradycardia, supraventricular or ventricular tachycardia) developed. Heart tissue was evaluated with vital staining and histologic examination. Data were analyzed with mixed effects logistic regression, receiver operating characteristic curves, and the Fisher exact test. Results Thirty-four pulmonary microwave ablations were performed with the antenna a median distance of 4 mm from the heart in both perpendicular (n = 17) and parallel (n = 17) orientation. Significant arrhythmias developed during six (18%) ablations. Cardiac tissue injury occurred with 17 ablations (50%). Risk of arrhythmia and tissue injury decreased with increasing antenna distance from the heart with both antenna orientations. No cardiac complication occurred with a distance of greater than or equal to 4.4 mm from the heart. The ablation zone extended to the pleural surface adjacent to the heart in 71% of parallel and 17% of perpendicular ablations performed 5–10 mm from the heart. Conclusion Microwave lung ablations performed more than or equal to 5 mm from the heart were associated with a low risk of cardiac complications. © RSNA, 2016 PMID:27732159

The prediction of radiofrequency ablation zone volume using vascular indices of 3-dimensional volumetric colour Doppler ultrasound in an in vitro blood-perfused bovine liver model

PubMed Central

Lanctot, Anthony C; McCarter, Martin D; Roberts, Katherine M; Glueck, Deborah H; Dodd, Gerald D

2017-01-01

Objective: To determine the most reliable predictor of radiofrequency (RF) ablation zone volume among three-dimensional (3D) volumetric colour Doppler vascular indices in an in vitro blood-perfused bovine liver model. Methods: 3D colour Doppler volume data of the local hepatic parenchyma were acquired from 37 areas of 13 bovine livers connected to an in vitro oxygenated blood perfusion system. Doppler vascular indices of vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were obtained from the volume data using 3D volume analysis software. 37 RF ablations were performed at the same locations where the ultrasound data were obtained from. The relationship of these vascular indices and the ablation zone volumes measured from gross specimens were analyzed using a general linear mixed model fit with random effect for liver and backward stepwise regression analysis. Results: FI was significantly associated with ablation zone volumes measured on gross specimens (p = 0.0047), but explained little of the variance (Rβ2 = 0.21). Ablation zone volume decreased by 0.23 cm3 (95% confidence interval: −0.38, −0.08) for every 1 increase in FI. Neither VI nor VFI was significantly associated with ablation zone volumes (p > 0.05). Conclusion: Although FI was associated with ablation zone volumes, it could not sufficiently explain their variability, limiting its clinical applicability. VI, FI and VFI are not clinically useful in the prediction of RF ablation zone volume in the liver. Advances in knowledge: Despite a significant association of FI with ablation zone volumes, VI, FI and VFI cannot be used for their prediction. Different Doppler vascular indices need to be investigated for clinical use. PMID:27925468

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, Scott M., E-mail: Thompson.scott@mayo.edu; Callstrom, Matthew R., E-mail: callstrom.matthew@mayo.edu; McKusick, Michael A., E-mail: mckusick.michael@mayo.edu

PurposeThe purpose of this study was to determine the feasibility, safety, and early effectiveness of percutaneous image-guided ablation as second-line treatment for symptomatic soft-tissue vascular anomalies (VA).Materials and MethodsAn IRB-approved retrospective review was undertaken of all patients who underwent percutaneous image-guided ablation as second-line therapy for treatment of symptomatic soft-tissue VA during the period from 1/1/2008 to 5/20/2014. US/CT- or MRI-guided and monitored cryoablation or MRI-guided and monitored laser ablation was performed. Clinical follow-up began at one-month post-ablation.ResultsEight patients with nine torso or lower extremity VA were treated with US/CT (N = 4) or MRI-guided (N = 2) cryoablation or MRI-guided laser ablation (N = 5)more » for moderate to severe pain (N = 7) or diffuse bleeding secondary to hemangioma–thrombocytopenia syndrome (N = 1). The median maximal diameter was 9.0 cm (6.5–11.1 cm) and 2.5 cm (2.3–5.3 cm) for VA undergoing cryoablation and laser ablation, respectively. Seven VA were ablated in one session, one VA initially treated with MRI-guided cryoablation for severe pain was re-treated with MRI-guided laser ablation due to persistent moderate pain, and one VA was treated in a planned two-stage session due to large VA size. At an average follow-up of 19.8 months (range 2–62 months), 7 of 7 patients with painful VA reported symptomatic pain relief. There was no recurrence of bleeding at five-year post-ablation in the patient with hemangioma–thrombocytopenia syndrome. There were two minor complications and no major complications.ConclusionImage-guided percutaneous ablation is a feasible, safe, and effective second-line treatment option for symptomatic VA.« less

Interstitial ultrasound ablation of vertebral and paraspinal tumours: Parametric and patient-specific simulations

PubMed Central

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

2015-01-01

Purpose Theoretical parametric and patient-specific models are applied to assess the feasibility of interstitial ultrasound ablation of tumours in and near the spine and to identify potential treatment delivery strategies. Methods 3D patient-specific finite element models (n=11) of interstitial ultrasound ablation of tumours associated with spine were generated. Gaseous nerve insulation and various applicator configurations, frequencies (3 and 7 MHz), placement trajectories, and tumour locations were simulated. Parametric studies with multilayered models investigated the impacts of tumour attenuation, tumour dimension, and the thickness of bone insulating critical structures. Temperature and thermal dose were calculated to define ablation (>240 equivalent minutes at 43°C (EM43°C)) and safety margins (<45°C & <6 EM43°C), and to determine performance and required delivery parameters. Results Osteolytic tumours (≤44 mm) encapsulated by bone could be successfully ablated with 7 MHz interstitial ultrasound (8.1-16.6 W/cm2, 120-5900 J, 0.4-15 min). Ablation of tumours (94.6-100% volumetric) 0-14.5 mm from the spinal canal was achieved within 3-15 min without damaging critical nerves. 3 MHz devices provided faster ablation (390 versus 930 s) of an 18 mm diameter osteoblastic (high bone content) volume than 7 MHz devices. Critical anatomy in proximity to the tumour could be protected by selection of appropriate applicator configurations, active sectors, and applied power schemas, and through gaseous insulation. Preferential ultrasound absorption at bone surfaces facilitated faster, more effective ablations in osteolytic tumours and provided isolation of ablative energies and temperatures. Conclusions Parametric and patient-specific studies demonstrated the feasibility and potential advantages of interstitial ultrasound ablation treatment of paraspinal and osteolytic vertebral tumours. PMID:25017322

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

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease.

PubMed

Klein, L S; Shih, H T; Hackett, F K; Zipes, D P; Miles, W M

1992-05-01

Radiofrequency energy has been used safely and successfully to eliminate accessory pathways in patients with the Wolff-Parkinson-White syndrome and the substrate for atrioventricular nodal reentrant tachycardia. However, this form of ablation has had only limited success in eliminating ventricular tachycardia in patients with structural heart disease. In contrast, direct-current catheter ablation has been used successfully to eliminate ventricular tachycardia in patients with and without structural heart disease. The purpose of this study was to test whether radiofrequency energy can safely and effectively ablate ventricular tachycardia in patients without structural heart disease. Sixteen patients (nine women and seven men; mean age, 38 years; range, 18-55 years) without structural heart disease who had ventricular tachycardia underwent radiofrequency catheter ablation to eliminate the ventricular tachycardia. Two patients presented with syncope, nine with presyncope, and five with palpitations only. Mean duration of symptoms was 6.7 years (range, 0.5-20 years). Radiofrequency catheter ablation successfully eliminated ventricular tachycardia in 15 of 16 patients (94%). Sites of ventricular tachycardia origin included the high right ventricular outflow tract (12 patients), the right ventricular septum near the tricuspid valve (three patients), and the left ventricular septum (one patient). The only ablation failure was in a patient whose ventricular tachycardia arose from a region near the His bundle. An accurate pace map, early local endocardial activation, and firm catheter contact with endocardium were associated with successful ablation. Radiofrequency ablation did not cause arrhythmias, produced minimal cardiac enzyme rise, and resulted in no detectable change in cardiac function by Doppler echocardiography. Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease is effective and safe and may be considered as early therapy in these patients.

Physical mechanisms of SiN{sub x} layer structuring with ultrafast lasers by direct and confined laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rapp, S., E-mail: rapp@hm.edu; Erlangen Graduate School in Advanced Optical Technologies; Heinrich, G.

2015-03-14

In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deepermore » understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN{sub x}) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm{sup 2} and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN{sub x} layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN{sub x} island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates.« less

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

PubMed

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

2017-03-28

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

The modified stepwise ablation guided by low-dose ibutilide in chronic atrial fibrillation trial (The MAGIC-AF Study).

PubMed

Singh, Sheldon M; d'Avila, Andre; Kim, Young-Hoon; Aryana, Arash; Mangrum, J Michael; Michaud, Gregory F; Dukkipati, Srinivas R; Barrett, Conor D; Heist, E Kevin; Parides, Michael K; Thorpe, Kevin E; Reddy, Vivek Y

2016-05-21

Complex fractionated atrial electrograms (CFAE) are targeted during persistent atrial fibrillation (AF) ablation. However, many CFAE sites are non-specific resulting in extensive ablation. Ibutilide has been shown to reduce left atrial surface area exhibiting CFAE. We hypothesized that ibutilide administration prior to CFAE ablation would identify sites critical for persistent AF maintenance allowing for improved procedural efficacy and long-term freedom from atrial arrhythmias. Two hundred patients undergoing a first-ever persistent AF catheter ablation procedure were randomly assigned to receive either 0.25 mg of intravenous ibutilide or saline placebo upon completion of pulmonary vein isolation. Complex fractionated atrial electrogram sites were then targeted with ablation. The primary efficacy endpoint was the 1-year single procedure freedom from atrial arrhythmia off anti-arrhythmic drugs. Similar procedural characteristics (procedure, fluoroscopy, and ablation times) were observed with both strategies despite a greater reduction in left atrial surface area with CFAE sites (8 vs. 1%, P < 0.0001) and AF termination during CFAE ablation with ibutilide compared with placebo (75 vs. 57%, P = 0.007). The primary efficacy endpoint was achieved in 56% of patients receiving ibutilide and 49% receiving placebo (P = 0.35). No significant differences in peri-procedural complications were observed in both groups. Despite a reduction in CFAE area and greater AF termination during CFAE ablation, procedural characteristics and clinical outcomes were unchanged when CFAE ablation was guided by ibutilide administration. ClinicalTrials.gov number: NCT01014741. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.

Radiofrequency ablation versus electrocautery in tonsillectomy.

PubMed

Hall, Daniel J; Littlefield, Philip D; Birkmire-Peters, Deborah P; Holtel, Michael R

2004-03-01

The objective of this study was to compare the safety, difficulty of removal, and postoperative pain profile of radiofrequency ablation versus standard electrocautery removal of tonsils. A prospective, blinded study was designed to remove 1 tonsil with each of the 2 methods. Time of operation, estimated blood loss, difficulty of operation, postoperative pain, rate of postoperative hemorrhage, and the patient's preferred technique were evaluated. The operating time was significantly longer (P < 0.007) and the patients reported significantly less pain (P < 0.001) with radiofrequency ablation. There were no differences in blood loss, difficulty of operation, or postoperative hemorrhage rates. The patients preferred the radiofrequency ablation technique (P < 0.001). Radiofrequency ablation is a viable method to remove tonsillar tissue. Operating time for this procedure will likely decrease with experience. There was significantly less pain reported with radiofrequency ablation compared with standard electrocautery.

Cooled radiofrequency ablation for bilateral greater occipital neuralgia.

PubMed

Vu, Tiffany; Chhatre, Akhil

2014-01-01

This report describes a case of bilateral greater occipital neuralgia treated with cooled radiofrequency ablation. The case is considered in relation to a review of greater occipital neuralgia, continuous thermal and pulsed radiofrequency ablation, and current medical literature on cooled radiofrequency ablation. In this case, a 35-year-old female with a 2.5-year history of chronic suboccipital bilateral headaches, described as constant, burning, and pulsating pain that started at the suboccipital region and radiated into her vertex. She was diagnosed with bilateral greater occipital neuralgia. She underwent cooled radiofrequency ablation of bilateral greater occipital nerves with minimal side effects and 75% pain reduction. Cooled radiofrequency ablation of the greater occipital nerve in challenging cases is an alternative to pulsed and continuous RFA to alleviate pain with less side effects and potential for long-term efficacy.

Cooled Radiofrequency Ablation for Bilateral Greater Occipital Neuralgia

PubMed Central

Chhatre, Akhil

2014-01-01

This report describes a case of bilateral greater occipital neuralgia treated with cooled radiofrequency ablation. The case is considered in relation to a review of greater occipital neuralgia, continuous thermal and pulsed radiofrequency ablation, and current medical literature on cooled radiofrequency ablation. In this case, a 35-year-old female with a 2.5-year history of chronic suboccipital bilateral headaches, described as constant, burning, and pulsating pain that started at the suboccipital region and radiated into her vertex. She was diagnosed with bilateral greater occipital neuralgia. She underwent cooled radiofrequency ablation of bilateral greater occipital nerves with minimal side effects and 75% pain reduction. Cooled radiofrequency ablation of the greater occipital nerve in challenging cases is an alternative to pulsed and continuous RFA to alleviate pain with less side effects and potential for long-term efficacy. PMID:24716017

Flow-dependent vascular heat transfer during microwave thermal ablation.

PubMed

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

2012-01-01

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

The first clinical application of planning software for laparoscopic microwave thermosphere ablation of malignant liver tumours

PubMed Central

Berber, Eren

2015-01-01

Background Liver tumour ablation is an operator-dependent procedure. The determination of the optimum needle trajectory and correct ablation parameters could be challenging. The aim of this study was to report the utility of a new, procedure planning software for microwave ablation (MWA) of liver tumours. Methods This was a feasibility study in a pilot group of five patients with nine metastatic liver tumours who underwent laparoscopic MWA. Pre-operatively, parameters predicting the desired ablation zones were calculated for each tumour. Intra-operatively, this planning strategy was followed for both antenna placement and energy application. Post-operative 2-week computed tomography (CT) scans were performed to evaluate complete tumour destruction. Results The patients had an average of two tumours (range 1–4), measuring 1.9 ± 0.4 cm (range 0.9–4.4 cm). The ablation time was 7.1 ± 1.3 min (range 2.5–10 min) at 100W. There were no complications or mortality. The patients were discharged home on post-operative day (POD) 1. At 2-week CT scans, there were no residual tumours, with a complete ablation demonstrated in all lesions. Conclusions This study describes and validates pre-treatment planning software for MWA of liver tumours. This software was found useful to determine precisely the ablation parameters and needle placement to create a predicted zone of ablation. PMID:25980481

A volumetric ablation model of EPDM considering complex physicochemical process in porous structure of char layer

NASA Astrophysics Data System (ADS)

Yang, Liu; Xiao-Jing, Yu; Jian-Ming, Ma; Yi-Wen, Guan; Jiang, Li; Qiang, Li; Sa, Yang

2017-06-01

A volumetric ablation model for EPDM (ethylene- propylene-diene monomer) is established in this paper. This model considers the complex physicochemical process in the porous structure of a char layer. An ablation physics model based on a porous structure of a char layer and another model of heterogeneous volumetric ablation char layer physics are then built. In the model, porosity is used to describe the porous structure of a char layer. Gas diffusion and chemical reactions are introduced to the entire porous structure. Through detailed formation analysis, the causes of the compact or loose structure in the char layer and chemical vapor deposition (CVD) reaction between pyrolysis gas and char layer skeleton are introduced. The Arrhenius formula is adopted to determine the methods for calculating carbon deposition rate C which is the consumption rate caused by thermochemical reactions in the char layer, and porosity evolution. The critical porosity value is used as a criterion for char layer porous structure failure under gas flow and particle erosion. This critical porosity value is obtained by fitting experimental parameters and surface porosity of the char layer. Linear ablation and mass ablation rates are confirmed with the critical porosity value. Results of linear ablation and mass ablation rate calculations generally coincide with experimental results, suggesting that the ablation analysis proposed in this paper can accurately reflect practical situations and that the physics and mathematics models built are accurate and reasonable.

Rationale and design of the NO-PARTY trial: near-zero fluoroscopic exposure during catheter ablation of supraventricular arrhythmias in young patients.

PubMed

Casella, Michela; Dello Russo, Antonio; Pelargonio, Gemma; Bongiorni, Maria Grazia; Del Greco, Maurizio; Piacenti, Marcello; Andreassi, Maria Grazia; Santangeli, Pasquale; Bartoletti, Stefano; Moltrasio, Massimo; Fassini, Gaetano; Marini, Massimiliano; Di Cori, Andrea; Di Biase, Luigi; Fiorentini, Cesare; Zecchi, Paolo; Natale, Andrea; Picano, Eugenio; Tondo, Claudio

2012-10-01

Radiofrequency catheter ablation is the mainstay of therapy for supraventricular tachyarrhythmias. Conventional radiofrequency catheter ablation requires the use of fluoroscopy, thus exposing patients to ionising radiation. The feasibility and safety of non-fluoroscopic radiofrequency catheter ablation has been recently reported in a wide range of supraventricular tachyarrhythmias using the EnSite NavX™ mapping system. The NO-PARTY is a multi-centre, randomised controlled trial designed to test the hypothesis that catheter ablation of supraventricular tachyarrhythmias guided by the EnSite NavX™ mapping system results in a clinically significant reduction in exposure to ionising radiation compared with conventional catheter ablation. The study will randomise 210 patients undergoing catheter ablation of supraventricular tachyarrhythmias to either a conventional ablation technique or one guided by the EnSite NavX™ mapping system. The primary end-point is the reduction of the radiation dose to the patient. Secondary end-points include procedural success, reduction of the radiation dose to the operator, and a cost-effectiveness analysis. In a subgroup of patients, we will also evaluate the radiobiological effectiveness of dose reduction by assessing acute chromosomal DNA damage in peripheral blood lymphocytes. NO-PARTY will determine whether radiofrequency catheter ablation of supraventricular tachyarrhythmias guided by the EnSite NavX™ mapping system is a suitable and cost-effective approach to achieve a clinically significant reduction in ionising radiation exposure for both patient and operator.

Ablation of multi-wavelet re-entry: general principles and in silico analyses.

PubMed

Spector, Peter S; Correa de Sa, Daniel D; Tischler, Ethan S; Thompson, Nathaniel C; Habel, Nicole; Stinnett-Donnelly, Justin; Benson, Bryce E; Bielau, Philipp; Bates, Jason H T

2012-11-01

Catheter ablation strategies for treatment of cardiac arrhythmias are quite successful when targeting spatially constrained substrates. Complex, dynamic, and spatially varying substrates, however, pose a significant challenge for ablation, which delivers spatially fixed lesions. We describe tissue excitation using concepts of surface topology which provides a framework for addressing this challenge. The aim of this study was to test the efficacy of mechanism-based ablation strategies in the setting of complex dynamic substrates. We used a computational model of propagation through electrically excitable tissue to test the effects of ablation on excitation patterns of progressively greater complexity, from fixed rotors to multi-wavelet re-entry. Our results indicate that (i) focal ablation at a spiral-wave core does not result in termination; (ii) termination requires linear lesions from the tissue edge to the spiral-wave core; (iii) meandering spiral-waves terminate upon collision with a boundary (linear lesion or tissue edge); (iv) the probability of terminating multi-wavelet re-entry is proportional to the ratio of total boundary length to tissue area; (v) the efficacy of linear lesions varies directly with the regional density of spiral-waves. We establish a theoretical framework for re-entrant arrhythmias that explains the requirements for their successful treatment. We demonstrate the inadequacy of focal ablation for spatially fixed spiral-waves. Mechanistically guided principles for ablating multi-wavelet re-entry are provided. The potential to capitalize upon regional heterogeneity of spiral-wave density for improved ablation efficacy is described.

Radiofrequency assisted pancreaticoduodenectomy for palliative surgical resection of locally advanced pancreatic adenocarcinoma.

PubMed

Kumar, Jayant; Reccia, Isabella; Sodergren, Mikael H; Kusano, Tomokazu; Zanellato, Artur; Pai, Madhava; Spalding, Duncan; Zacharoulis, Dimitris; Habib, Nagy

2018-03-20

Despite careful patient selection and preoperative investigations curative resection rate (R0) in pancreaticoduodenectomy ranges from 15% to 87%. Here we describe a new palliative approach for pancreaticoduodenectomy using a radiofrequency energy device to ablate tumor in situ in patients undergoing R1/R2 resections for locally advanced pancreatic ductal adenocarcinoma where vascular reconstruction was not feasible. There was neither postoperative mortality nor significant morbidity. Each time the ablation lasted less than 15 minutes. Following radiofrequency ablation it was observed that the tumor remnant attached to the vessel had shrunk significantly. In four patients this allowed easier separation and dissection of the ablated tumor from the adherent vessel leading to R1 resection. In the other two patients, the ablated tumor did not separate from vessel due to true tumor invasion and patients had an R2 resection. The ablated remnant part of the tumor was left in situ. Whenever pancreaticoduodenectomy with R0 resection cannot be achieved, this new palliative procedure could be considered in order to facilitate resection and enable maximum destruction in remnant tumors. Six patients with suspected tumor infiltration and where vascular reconstruction was not warranted underwent radiofrequency-assisted pancreaticoduodenectomy for locally advanced pancreatic ductal adenocarcinoma. Radiofrequency was applied across the tumor vertically 5-10 mm from the edge of the mesenteric and portal veins. Following ablation, the duodenum and the head of pancreas were removed after knife excision along the ablated line. The remaining ablated tissue was left in situ attached to the vessel.

Length of Barrett's segment predicts failure of eradication in radiofrequency ablation for Barrett's esophagus: a retrospective cohort study.

PubMed

Luckett, Tyler; Allamneni, Chaitanya; Cowley, Kevin; Eick, John; Gullick, Allison; Peter, Shajan

2018-05-21

We aim to investigate factors that may contribute to failure of eradication of dysplastic Barrett's Esophagus among patients undergoing radiofrequency ablation treatment. A retrospective review of patients undergoing radiofrequency ablation for treatment of Barrett's Esophagus was performed. Data analyzed included patient demographics, medical history, length of Barrett's Esophagus, number of radiofrequency ablation sessions, and histopathology. Subsets of patients achieving complete eradication were compared with those not achieving complete eradication. A total of 107 patients underwent radiofrequency ablation for Barrett's Esophagus, the majority white, overweight, and male. Before treatment, 63 patients had low-grade dysplasia, and 44 patients had high-grade dysplasia or carcinoma. Complete eradication was achieved in a majority of patients (57% for metaplasia, and 76.6% for dysplasia). Failure of eradication occurred in 15.7% of patients. The median number of radiofrequency ablation treatments in patients achieving complete eradication was 3 sessions, compared to 4 sessions for failure of eradication (p = 0.06). Barrett's esophagus length of more than 5 cm was predictive of failure of eradication (p < 0.001). Radiofrequency ablation for dysplastic Barrett's Esophagus is a proven and effective treatment modality, associated with a high rate of complete eradication. Our rates of eradication from a center starting an ablation program are comparable to previously published studies. Length of Barrett's segment > 5 cm was found to be predictive of failure of eradication in patients undergoing radiofrequency ablation.

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

PubMed

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

2018-01-01

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

Pacemaker implantation after catheter ablation for atrial fibrillation.

PubMed

Deshmukh, Abhishek J; Yao, Xiaoxi; Schilz, Stephanie; Van Houten, Holly; Sangaralingham, Lindsey R; Asirvatham, Samuel J; Friedman, Paul A; Packer, Douglas L; Noseworthy, Peter A

2016-01-01

Sinus node dysfunction requiring pacemaker implantation is commonly associated with atrial fibrillation (AF), but may not be clinically apparent until restoration of sinus rhythm with ablation or cardioversion. We sought to determine frequency, time course, and predictors for pacemaker implantation after catheter ablation, and to compare the overall rates to a matched cardioversion cohort. We conducted a retrospective analysis using a large US commercial insurance database and identified 12,158 AF patients who underwent catheter ablation between January 1, 2005 and December 31, 2012. Over an average of 2.4 years of follow-up, 5.6 % of the patients underwent pacemaker implantation. Using the Cox proportional hazards models, we found that risk of risks of pacemaker implantation was associated with older age (50-64 and ≥65 versus <50 years), female gender, higher CHADS2 score (≥2 and 1 versus 0), higher Charlson index (≥2 versus 0-1), certain baseline comorbidities (conduction disorder, coronary atherosclerosis, and congestive heart failure), and the year of ablation. There was no significant difference in the risk of pacemaker implantation between ablation patients and propensity score (PS)-matched cardioversion groups (3.5 versus. 4.1 % at 1 year and 8.8 versus 8.3 % at 5 years). Overall, pacemaker implantation occurs in about 1/28 patients within 1 year of catheter ablation. The overall implantation rate decreased between 2005 and 2012. Furthermore, the risk after ablation is similar to cardioversion, suggesting that patients require pacing due to a common underlying electrophysiologic substrate, rather than the ablation itself.

Influence of ablation wavelength and time on optical properties of laser ablated carbon dots

NASA Astrophysics Data System (ADS)

Isnaeni, Hanna, M. Yusrul; Pambudi, A. A.; Murdaka, F. H.

2017-01-01

Carbon dots, which are unique and applicable materials, have been produced using many techniques. In this work, we have fabricated carbon dots made of coconut fiber using laser ablation technique. The purpose of this work is to evaluate two ablation parameters, which are ablation wavelength and ablation time. We used pulsed laser from Nd:YAG laser with emit wavelength at 355 nm, 532 nm and 1064 nm. We varied ablation time one hour and two hours. Photoluminescence and time-resolved photoluminescence setup were used to study the optical properties of fabricated carbon dots. In general, fabricated carbon dots emit bluish green color emission upon excitation by blue laser. We found that carbon dots fabricated using 1064 nm laser produced the highest carbon dots emission among other samples. The peak wavelength of carbon dots emission is between 495 nm until 505 nm, which gives bluish green color emission. Two hours fabricated carbon dots gave four times higher emission than one hour fabricated carbon dot. More emission intensity of carbon dots means more carbon dots nanoparticles were fabricated during laser ablation process. In addition, we also measured electron dynamics of carbon dots using time-resolved photoluminescence. We found that sample with higher emission has longer electron decay time. Our finding gives optimum condition of carbon dots fabrication from coconut fiber using laser ablation technique. Moreover, fabricated carbon dots are non-toxic nanoparticles that can be applied for health, bio-tagging and medical applications.

Accessory atrioventricular pathways refractory to catheter ablation: role of percutaneous epicardial approach.

PubMed

Scanavacca, Maurício Ibrahim; Sternick, Eduardo Back; Pisani, Cristiano; Lara, Sissy; Hardy, Carina; d'Ávila, André; Correa, Frederico Soares; Darrieux, Francisco; Hachul, Denise; Marcial, Miguel Barbero; Sosa, Eduardo A

2015-02-01

Epicardial mapping and ablation of accessory pathways through a subxiphoid approach can be an alternative when endocardial or epicardial transvenous mapping has failed. We reviewed acute and long-term follow-up of 21 patients (14 males) referred for percutaneous epicardial accessory pathway ablation. There was a median of 2 previous failed procedures. All patients were highly symptomatic, 8 had atrial fibrillation (3 with cardiac arrest) and 13 had frequent symptomatic episodes of atrioventricular reentrant tachycardia. Six patients (28.5%) had a successful epicardial ablation. Five patients (23.8%) underwent a successful repeated endocardial mapping, and ablation after epicardial mapping yielded no early activation site. Epicardial mapping was helpful in guiding endocardial ablation in 2 patients (9.5%), showing that the earliest activation was simultaneous at the epicardium and endocardium. Four patients (19%) underwent successful open-chest surgery after failing epicardial/endocardial ablation. Two patients (9.5%) remained controlled under antiarrhythmic drugs after unsuccessful endocardial/epicardial ablation. Two patients had a coronary sinus diverticulum and one a right atrium to right ventricle diverticulum. Three patients acquired postablation coronary sinus stenosis. There was no major complication related to pericardial access. Percutaneous epicardial approach is an alternative when conventional endocardial or transvenous epicardial ablation fails in the elimination of the accessory pathway. A new attempt by endocardial approach was successful in a significant number of patients. Open-chest surgery may be required in symptomatic cases refractory to endocardial-epicardial approach. © 2014 American Heart Association, Inc.

Influence of spatial and temporal spot distribution on the ocular surface quality and maximum ablation depth after photoablation with a 1050 Hz excimer laser system.

PubMed

Mrochen, Michael; Schelling, Urs; Wuellner, Christian; Donitzky, Christof

2009-02-01

To investigate the effect of temporal and spatial distributions of laser spots (scan sequences) on the corneal surface quality after ablation and the maximum ablation of a given refractive correction after photoablation with a high-repetition-rate scanning-spot laser. IROC AG, Zurich, Switzerland, and WaveLight AG, Erlangen, Germany. Bovine corneas and poly(methyl methacrylate) (PMMA) plates were photoablated using a 1050 Hz excimer laser prototype for corneal laser surgery. Four temporal and spatial spot distributions (scan sequences) with different temporal overlapping factors were created for 3 myopic, 3 hyperopic, and 3 phototherapeutic keratectomy ablation profiles. Surface quality and maximum ablation depth were measured using a surface profiling system. The surface quality factor increased (rough surfaces) as the amount of temporal overlapping in the scan sequence and the amount of correction increased. The rise in surface quality factor was less for bovine corneas than for PMMA. The scan sequence might cause systematic substructures at the surface of the ablated material depending on the overlapping factor. The maximum ablation varied within the scan sequence. The temporal and spatial distribution of the laser spots (scan sequence) during a corneal laser procedure affected the surface quality and maximum ablation depth of the ablation profile. Corneal laser surgery could theoretically benefit from smaller spot sizes and higher repetition rates. The temporal and spatial spot distributions are relevant to achieving these aims.

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

PubMed

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

2004-12-01

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

Numerical study of double-pulse laser ablation of Al

NASA Astrophysics Data System (ADS)

Förster, G. D.; Lewis, Laurent J.

2018-06-01

The effect of double laser pulses (DPs) on the ablation process in solids is studied using a hybrid two-temperature model combining a continuum description of the conduction band electrons with a classical molecular dynamics (MD) approach for the ions. The study is concerned with double pulses with delays in the range of 0-50 ps and absorbed laser fluences of 0.5, 1.0, and 1.5 J/m 2 [i.e., 1-3 times the ablation threshold for single-pulse ablation (SP)], taking Al as a generic example of simple metals. A detailed analysis, including the assessment of thermodynamic pathways and cavitation rates, leads to a comprehensive picture of the mechanisms active during the different stages of the ablation process initiated by DPs. This study provides an explanation for several phenomena observed in DP ablation experiments. In particular, with respect to SP ablation, crater depths are reduced, which can be explained by the compensation of the rarefaction wave from the first laser pulse with the compression wave from the second pulse, or, at higher fluences and larger delays, by the fact that the target surface is shielded with matter ablated by the first laser pulse. Also, we discuss how smoother surface structures obtained using DPs may be related to features found in the simulations—viz., reduced mechanical strain and peak lattice temperatures. Finally, vaporization appears to be enhanced in DP ablation, which may improve the resolution of emission spectra.

A Difference Scheme with Autocontrol Artificial Viscosity to Predict Ablated Nosetip Shape

DTIC Science & Technology

1989-09-29

I FTD-ID(RS)T-0640-89 U) (0 FOREIGN TECHNOLOGY DIVISION A DIFFERENCE SCHEME WITH AUTOCONTROL ARTIFICIAL VISCOSITY TO PREDICT ABLATED NOSETIP SHAPE by...September 1989 MICROFICHE NR: FTD-89-C-000800 A DIFFERENCE SCHEME WITH AUTOCONTROL ARTIFICIAL VISCOSITY TO PREDICT ABLATED NOSETIP SHAPE By: Yang Maozhao...DIFFERENCE SCHEME WITH AUTOCONTROL ARTIFICIAL VISCOSITY TO PREDICT ABLATED NOSETIP SHAPE Yang Maozhao (China Aerodynamic Research and Development Centre

New Experimental Results of Simulating Micrometeoroid Ablation in the Laboratory

NASA Astrophysics Data System (ADS)

Sternovsky, Zoltan; Thomas, Evan; DeLuca, Michael; Janches, Diego; Munsat, Tobin; Plane, John

2017-04-01

A facility is developed to simulate the ablation of micrometeoroids in laboratory conditions, which also allows measuring the ionization probability of the ablated material. An electrostatic dust accelerator is used to generate iron, aluminum and meteoric analog particles with velocities 10-50 km/s. The particles are then introduced into a cell filled with nitrogen, air or carbon dioxide gas with pressures adjustable in the 0.02 - 0.5 Torr range, where the partial or complete ablation of the particle occurs over a short distance. An array of biased electrodes is used to collect the ionized products with spatial resolution along the ablating particles' path, allowing thus the study of the temporal resolution of the process. A new optical observation setup using a 64 channel PMT system was added to the setup to allow the observation of the ablating particle and deceleration of the particle from the neutral drag. A simple ablation model is used to match the observations. For completely ablated particles the total collected charge directly yields the ionization efficiency. The measurements using iron particles in N2 and air are in relatively good agreement with earlier data. The new experimental data using aluminum particles suggest that the neutral drag acting of the particle is smaller than expected.

Structural modifications induced in dentin by femtosecond laser

NASA Astrophysics Data System (ADS)

Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

2016-12-01

The structural and chemical modifications induced in dentin by ultrafast laser ablation were studied. The laser experiments were performed with a Yb:KYW chirped-pulse-regenerative amplification laser system (560-fs pulse duration, 1030-nm radiation wavelength), fluences in the range 2 to 14 J/cm2, 1-kHz pulse repetition rate, and 5-mm/s scanning speed. The ablation surfaces were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The ablation surfaces produced with 2 J/cm2 presented an irregular morphology with exposed dentinal tubules and no evidence of thermal effects. For 7 and 14 J/cm2, the ablation surfaces were covered by a layer of redeposited ablation debris, consisting mainly of amorphous calcium phosphate. This layer is weakly adherent to the underlying tissue and can be easily removed by ultrasonication, revealing a surface with a morphology similar to the one obtained with 2 J/cm2. The constitution of the dentin ablation surfaces is similar to the constitution of pristine dentin, showing that, within this fluence range, the laser treatment does not significantly modify the structure and constitution of dentin. The results achieved suggest an ablation mechanism where collagen is preferentially decomposed by the laser radiation, reducing the tissue cohesive strength and leading, ultimately, to its ablation.

Image guided radiofrequency thermo-ablation therapy of chondroblastomas: should it replace surgery?

PubMed

Lalam, Radhesh K; Cribb, Gillian L; Tins, Bernard J; Cool, Wim P; Singh, Jaspreet; Tyrrell, Prudencia N M; Cassar-Pullicino, Victor N

2014-04-01

To assess the safety and effectiveness of image-guided radiofrequency ablation (RF ablation) in the treatment of chondroblastomas as an alternative to surgery. Twelve patients with histologically proven chondroblastoma at our institution from 2003 to date. We reviewed the indications, recurrences and complications in patients who underwent RF ablation. Twelve patients were diagnosed with chondroblastoma. Out of these, 8 patients (6 male, 2 female, mean age 17 years) with chondroblastoma (mean size 2.7 cm) underwent RF ablation. Multitine expandable electrodes were used in all patients. The number of probe positions needed varied from 1 to 4 and lesions were ablated at 90 °C for 5 min at each probe position. The tumours were successfully treated and all patients became asymptomatic. There were no recurrences. There were 2 patients with knee complications, 1 with minor asymptomatic infraction of the subchondral bone and a second patient with osteonecrosis/chondrolysis. Radiofrequency ablation appears to be a safe and effective alternative to surgical treatment with a low risk of recurrence and complications for most chondroblastomas. RF ablation is probably superior to surgery when chondroblastomas are small (less than 2.5 cm) with an intact bony margin with subchondral bone and in areas of difficult surgical access.

Ablation-cooled material removal with ultrafast bursts of pulses

NASA Astrophysics Data System (ADS)

Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K.; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D.; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer

2016-09-01

The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.

Ablation-cooled material removal with ultrafast bursts of pulses.

PubMed

Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer

2016-09-01

The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.

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

NASA Astrophysics Data System (ADS)

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

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.

Efficacy comparison between cryoablation and radiofrequency ablation for patients with cavotricuspid valve isthmus dependent atrial flutter: a meta-analysis

NASA Astrophysics Data System (ADS)

Chen, Yi-He; Lin, Hui; Xie, Cheng-Long; Zhang, Xiao-Ting; Li, Yi-Gang

2015-06-01

We perform this meta-analysis to compare the efficacy and safety of cryoablation versus radiofrequency ablation for patients with cavotricuspid valve isthmus dependent atrial flutter. By searching EMBASE, MEDLINE, PubMed and Cochrane electronic databases from March 1986 to September 2014, 7 randomized clinical trials were included. Acute (risk ratio[RR]: 0.93; P = 0.14) and long-term (RR: 0.94; P = 0.08) success rate were slightly lower in cryoablation group than in radiofrequency ablation group, but the difference was not statistically significant. Additionally, the fluoroscopy time was nonsignificantly reduced (weighted mean difference[WMD]: -2.83 P = 0.29), whereas procedure time was significantly longer (WMD: 25.95; P = 0.01) in cryoablation group compared with radiofrequency ablation group. Furthermore, Pain perception during the catheter ablation was substantially less in cryoabaltion group than in radiofrequency ablation group (standardized mean difference[SMD]: -2.36 P < 0.00001). Thus, our meta-analysis demonstrated that cryoablation and radiofrequency ablation produce comparable acute and long-term success rate for patients with cavotricuspid valve isthmus dependent atrial flutter. Meanwhile, cryoablation ablation tends to reduce the fluoroscopy time and significantly reduce pain perception in cost of significantly prolonged procedure time.

Efficacy comparison between cryoablation and radiofrequency ablation for patients with cavotricuspid valve isthmus dependent atrial flutter: a meta-analysis

PubMed Central

Chen, Yi-He; Lin, Hui; Xie, Cheng-Long; Zhang, Xiao-Ting; Li, Yi-Gang

2015-01-01

We perform this meta-analysis to compare the efficacy and safety of cryoablation versus radiofrequency ablation for patients with cavotricuspid valve isthmus dependent atrial flutter. By searching EMBASE, MEDLINE, PubMed and Cochrane electronic databases from March 1986 to September 2014, 7 randomized clinical trials were included. Acute (risk ratio[RR]: 0.93; P = 0.14) and long-term (RR: 0.94; P = 0.08) success rate were slightly lower in cryoablation group than in radiofrequency ablation group, but the difference was not statistically significant. Additionally, the fluoroscopy time was nonsignificantly reduced (weighted mean difference[WMD]: −2.83; P = 0.29), whereas procedure time was significantly longer (WMD: 25.95; P = 0.01) in cryoablation group compared with radiofrequency ablation group. Furthermore, Pain perception during the catheter ablation was substantially less in cryoabaltion group than in radiofrequency ablation group (standardized mean difference[SMD]: −2.36; P < 0.00001). Thus, our meta-analysis demonstrated that cryoablation and radiofrequency ablation produce comparable acute and long-term success rate for patients with cavotricuspid valve isthmus dependent atrial flutter. Meanwhile, cryoablation ablation tends to reduce the fluoroscopy time and significantly reduce pain perception in cost of significantly prolonged procedure time. PMID:26039980

Robotic navigation and ablation.

PubMed

Malcolme-Lawes, L; Kanagaratnam, P

2010-12-01

Robotic technologies have been developed to allow optimal catheter stability and reproducible catheter movements with the aim of achieving contiguous and transmural lesion delivery. Two systems for remote navigation of catheters within the heart have been developed; the first is based on a magnetic navigation system (MNS) Niobe, Stereotaxis, Saint-Louis, Missouri, USA, the second is based on a steerable sheath system (Sensei, Hansen Medical, Mountain View, CA, USA). Both robotic and magnetic navigation systems have proven to be feasible for performing ablation of both simple and complex arrhythmias, particularly atrial fibrillation. Studies to date have shown similar success rates for AF ablation compared to that of manual ablation, with many groups finding a reduction in fluoroscopy times. However, the early learning curve of cases demonstrated longer procedure times, mainly due to additional setup times. With centres performing increasing numbers of robotic ablations and the introduction of a pressure monitoring system, lower power settings and instinctive driving software, complication rates are reducing, and fluoroscopy times have been lower than manual ablation in many studies. As the demand for catheter ablation for arrhythmias such as atrial fibrillation increases and the number of centres performing these ablations increases, the demand for systems which reduce the hand skill requirement and improve the comfort of the operator will also increase.

Impact of Radiofrequency Ablation on Malignant Biliary Strictures: Results of a Collaborative Registry.

PubMed

Sharaiha, Reem Z; Sethi, Amrita; Weaver, Kristen R; Gonda, Tamas A; Shah, Raj J; Fukami, Norio; Kedia, Prashant; Kumta, Nikhil A; Clavo, Carlos M Rondon; Saunders, Michael D; Cerecedo-Rodriguez, Jorge; Barojas, Paola Figueroa; Widmer, Jessica L; Gaidhane, Monica; Brugge, William R; Kahaleh, Michel

2015-07-01

Radiofrequency ablation of malignant biliary strictures has been offered for the last 3 years, but only limited data have been published. To assess the safety, efficacy, and survival outcomes of patients receiving endoscopic radiofrequency ablation. Between April 2010 and December 2013, 69 patients with unresectable neoplastic lesions and malignant biliary obstruction underwent 98 radiofrequency ablation sessions with stenting. A total of 69 patients (22 male, aged 66.1 ± 13.3) were included in the registry. The etiology of malignant biliary stricture included unresectable cholangiocarcinoma (n = 45), pancreatic cancer (n = 19), gallbladder cancer (n = 2), gastric cancer (n = 1), and liver metastasis from colon cancer (n = 3). Seventy-eight percentage of patients had prior chemotherapy. All strictures were stented post-radiofrequency ablation with either plastic stents or metal stents. The mean stricture length treated was 14.3 mm. There was a statistically significant improvement in stricture diameter post-ablation (p < 0.0001). The likelihood of stricture improvement was significantly greater in pancreatic cancer-associated strictures [RR 1.8 (95 % 1.03-5.38)]. Seven patients (10 %) had adverse events, not linked directly to radiofrequency ablation. Median survival was 11.46 months (6.2-25 months). Radiofrequency ablation is effective and safe in malignant biliary obstruction and seems to be associated with improved survival.

X-ray driven implosions at ignition relevant velocities on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meezan, N. B.; MacKinnon, A. J.; Hicks, D. G.

2013-05-15

Backlit convergent ablator experiments on the National Ignition Facility [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] are indirect drive implosions that study the inflight dynamics of an imploding capsule. Side-on, backlit radiography provides data used by the National Ignition Campaign to measure time-dependent properties of the capsule ablator including its center of mass radius, velocity, and unablated mass. Previously, Callahan [D. A. Callahan et al., Phys. Plasmas 19, 056305 (2012)] and Hicks [D. H. Hicks et al., Phys. Plasmas 19, 122702 (2012)] reported backlit convergent ablator experiments demonstrating velocities approaching those required for ignition. This paper focusesmore » on implosion performance data in the “rocket curve” plane, velocity vs. ablator mass. These rocket curve data, along with supporting numerical simulations, show that the nominal 195 μm-thick ignition capsule would reach the ignition velocity goal V = 370 km/s with low ablator mass remaining–below the goal of M = 0.25 mg. This finding led to experiments with thicker capsule ablators. A recent symmetry capsule experiment with a 20 μm thicker capsule driven by 520 TW, 1.86 MJ laser pulse (along with a companion backlit convergent ablator experiment) appears to have demonstrated V≥350 km/s with ablator mass remaining above the ignition goal.« less

Anode sheath transition in an anodic arc for synthesis of nanomaterials

NASA Astrophysics Data System (ADS)

Nemchinsky, V. A.; Raitses, Y.

2016-06-01

The arc discharge with ablating anode or so-called anodic arc is widely used for synthesis of nanomaterials, including carbon nanotubes and fullerens, metal nanoparticles etc. We present the model of this arc, which confirms the existence of the two different modes of the arc operation with two different anode sheath regimes, namely, with negative anode sheath and with positive anode sheath. It was previously suggested that these regimes are associated with two different anode ablating modes—low ablation mode with constant ablation rate and the enhanced ablation mode (Fetterman et al 2008 Carbon 46 1322). The transition of the arc operation from low ablation mode to high ablation mode is determined by the current density at the anode. The model can be used to self-consistently determine the distribution of the electric field, electron density and electron temperature in the near-anode region of the arc discharge. Simulations of the carbon arc predict that for low arc ablating modes, the current is driven mainly by the electron diffusion to the anode. For positive anode sheath, the anode voltage is close to the ionization potential of anode material, while for negative anode sheath, the anode voltage is an order of magnitude smaller. It is also shown that the near-anode plasma, is far from the ionization equilibrium.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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

[Study of New Micropore RF system on Lesion Formation and Complications].

PubMed

Song, Yuwen; Xu, Xiulin; Cai, Yameng

2017-07-30

To study the safety and effectiveness of a new type of micropore ablation catheter in vitro ablation system, and to provide reference for clinical practice. To evaluate two kinds of catheter in cardiac tissue ablation depth, tissue temperature and thrombosis situation by the same RF system. The power set 25 W, There was no significant difference in ablation depth between the two groups, and no Pop and thrombosis occurred. When the power is more than 40 W, two groups occurred more Pop and thrombosis. When using high power for Cardiac RF ablation, doctors should pay more attention to complications and thrombosis.

Microwave ablation in primary and secondary liver tumours: technical and clinical approaches.

PubMed

Meloni, Maria Franca; Chiang, Jason; Laeseke, Paul F; Dietrich, Christoph F; Sannino, Angela; Solbiati, Marco; Nocerino, Elisabetta; Brace, Christopher L; Lee, Fred T

2017-02-01

Thermal ablation is increasingly being utilised in the treatment of primary and metastatic liver tumours, both as curative therapy and as a bridge to transplantation. Recent advances in high-powered microwave ablation systems have allowed physicians to realise the theoretical heating advantages of microwave energy compared to other ablation modalities. As a result there is a growing body of literature detailing the effects of microwave energy on tissue heating, as well as its effect on clinical outcomes. This article will discuss the relevant physics, review current clinical outcomes and then describe the current techniques used to optimise patient care when using microwave ablation systems.

Ablative Thermal Protection Systems Fundamentals

NASA Technical Reports Server (NTRS)

Beck, Robin A. S.

2017-01-01

This is a presentation of the fundamentals of ablative TPS materials for a short course at TFAWS 2017. It gives an overall description of what an ablator is, the equations that define it, and how to model it.

Experimental investigation of the laser ablation process on wood surfaces

NASA Astrophysics Data System (ADS)

Panzner, M.; Wiedemann, G.; Henneberg, K.; Fischer, R.; Wittke, Th.; Dietsch, R.

1998-05-01

Processing of wood by conventional mechanical tools like saws or planes leaves behind a layer of squeezed wood only slightly adhering to the solid wood surface. Laser ablation of this layer could improve the durability of coatings and glued joints. For technical applications, thorough knowledge about the laser ablation process is necessary. Results of ablation experiments by excimer lasers, Nd:YAG lasers, and TEA-CO 2 lasers on surfaces of different wood types and cut orientations are shown. The process of ablation was observed by a high-speed camera system and optical spectroscopy. The influence of the experimental parameters are demonstrated by SEM images and measurement of the ablation rate depending on energy density. Thermal effects like melting and also carbonizing of cellulose were found for IR- and also UV-laser wavelengths. Damage of the wood surface after laser ablation was weaker for excimer lasers and CO 2-TEA lasers. This can be explained by the high absorption of wood in the ultraviolet and middle infrared spectral range. As an additional result, this technique provides an easy way for preparing wood surfaces with excellently conserved cellular structure.

Avoiding Complications in Bone and Soft Tissue Ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurup, A. Nicholas, E-mail: kurup.anil@mayo.edu; Schmit, Grant D., E-mail: schmit.grant@mayo.edu; Morris, Jonathan M., E-mail: morris.jonathan@mayo.edu

As with percutaneous ablation of tumors in the liver, lungs, and kidneys, ablation of bone and non-visceral soft tissue tumors carries risk, primarily from collateral damage to vital structures in proximity to the target tumor. Certain risks are of particular interest when ablating bone and non-visceral soft tissue tumors, namely neural or skin injury, bowel injury, fracture, and gas embolism from damaged applicators. Ablation of large volume tumors also carries special risk. Many techniques may be employed by the interventional radiologist to minimize complications when treating tumors in the musculoskeletal system. These methods include those to depict, displace, or monitormore » critical structures. Thus, measures to provide thermoprotection may be active, such as careful ablation applicator placement and use of various displacement techniques, as well as passive, including employment of direct temperature, radiographic, or neurophysiologic monitoring techniques. Cementoplasty should be considered in certain skeletal locations at risk of fracture. Patients treated with large volume tumors should be monitored for renal dysfunction and properly hydrated. Finally, ablation applicators should be cautiously placed in the constrained environment of intact bone.« less

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

PubMed

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

2014-07-01

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

High-frequency microwave ablation method for enhanced cancer treatment with minimized collateral damage.

PubMed

Yoon, Jeonghoon; Cho, Jeiwon; Kim, Namgon; Kim, Dae-Duk; Lee, Eunsook; Cheon, Changyul; Kwon, Youngwoo

2011-10-15

To overcome the limits of conventional microwave ablation, a new frequency spectrum above 6 GHz has been explored for low-power and low collateral damage ablation procedure. A planar coaxial probe-based applicator, suitable for easy insertion into the human body, was developed for our study to cover a wideband frequency up to 30 GHz. Thermal ablations with small input power (1-3 W) at various microwave frequencies were performed on nude mice xenografted with human breast cancer. Comparative study of ablation efficiencies revealed that 18-GHz microwave results in the largest difference in the temperature rise between cancer and normal tissues as well as the highest ablation efficiency, reaching 20 times that of 2 GHz. Thermal profile study on the composite region of cancer and fat also showed significantly reduced collateral damage using 18 GHz. Application of low-power (1 W) 18-GHz microwave on the nude mice xenografted with human breast cancer cells resulted in recurrence-free treatment. The proposed microwave ablation method can be a very effective process to treat small-sized tumor with minimized invasiveness and collateral damages. Copyright © 2010 UICC.

Novel Laser Ablation Technology for Surface Decontamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Chung H.

2004-06-01

Laser ablation for surface cleaning has been pursued for the removal of paint on airplanes. It has also been pursued for the cleaning of semiconductor surfaces. However, all these approaches have been pursued by laser ablation in air. For highly contaminated surface, laser ablation in air can easily cause secondary contamination. Thus it is not suitable to apply to achieve surface decontamination for DOE facilities since many of these facilities have radioactive contaminants on the surface. Any secondary contamination will be a grave concern. The objective of this project is to develop a novel technology for laser ablation in liquidmore » for surface decontamination. It aims to achieve more efficient surface decontamination without secondary contamination and to evaluate the economic feasibility for large scale surface decontamination with laser ablation in liquid. When laser ablation is pursued in the solution, all the desorbed contaminants will be confined in liquid. The contaminants can be precipitated and subsequently contained in a small volume for disposal. It can reduce the risk of the decontamination workers. It can also reduce the volume of contaminants dramatically.« less

Laser selective cutting of biological tissues by impulsive heat deposition through ultrafast vibrational excitations.

PubMed

Franjic, Kresimir; Cowan, Michael L; Kraemer, Darren; Miller, R J Dwayne

2009-12-07

Mechanical and thermodynamic responses of biomaterials after impulsive heat deposition through vibrational excitations (IHDVE) are investigated and discussed. Specifically, we demonstrate highly efficient ablation of healthy tooth enamel using 55 ps infrared laser pulses tuned to the vibrational transition of interstitial water and hydroxyapatite around 2.95 microm. The peak intensity at 13 GW/cm(2) was well below the plasma generation threshold and the applied fluence 0.75 J/cm(2) was significantly smaller than the typical ablation thresholds observed with nanosecond and microsecond pulses from Er:YAG lasers operating at the same wavelength. The ablation was performed without adding any superficial water layer at the enamel surface. The total energy deposited per ablated volume was several times smaller than previously reported for non-resonant ultrafast plasma driven ablation with similar pulse durations. No micro-cracking of the ablated surface was observed with a scanning electron microscope. The highly efficient ablation is attributed to an enhanced photomechanical effect due to ultrafast vibrational relaxation into heat and the scattering of powerful ultrafast acoustic transients with random phases off the mesoscopic heterogeneous tissue structures.

A new catheter design for combined radiofrequency ablation and optoacoustic treatment monitoring using copper-coated light-guides

NASA Astrophysics Data System (ADS)

Rebling, Johannes; Oyaga Landa, Francisco Javier; Deán-Ben, Xosé Luis; Razansky, Daniel

2018-02-01

Electrosurgery, i.e. the application of radiofrequency current for tissue ablation, is a frequently used treatment for many cardiac arrhythmias. Electrophysiological and anatomic mapping, as well as careful radiofrequency power control typically guide the radiofrequency ablation procedure. Despite its widespread application, accurate monitoring of the lesion formation with sufficient spatio-temporal resolution remains challenging with the existing imaging techniques. We present a novel integrated catheter for simultaneous radiofrequency ablation and optoacoustic monitoring of the lesion formation in real time and 3D. The design combines the delivery of both electric current and optoacoustic excitation beam in a single catheter consisting of copper-coated multimode light-guides and its manufacturing is described in detail. The electrical current causes coagulation and desiccation while the excitation light is locally absorbed, generating OA responses from the entire treated volume. The combined ablation-monitoring capabilities were verified using ex-vivo bovine tissue. The formed ablation lesions showed a homogenous coagulation while the ablation was monitored in realtime with a volumetric frame rate of 10 Hz over 150 seconds.

Case study on the dynamics of ultrafast laser heating and ablation of gold thin films by ultrafast pump-probe reflectometry and ellipsometry

NASA Astrophysics Data System (ADS)

Pflug, T.; Wang, J.; Olbrich, M.; Frank, M.; Horn, A.

2018-02-01

To increase the comprehension of ultrafast laser ablation, the ablation process has to be portrayed with sufficient temporal resolution. For example, the temporal modification of the complex refractive index {\\tilde{n}} and the relative reflectance of a sample material after irradiation with ultrafast single-pulsed laser radiation can be measured with a pump-probe setup. This work describes the construction and validation of a pump-probe setup enabling spatially, temporally, and spectroscopically resolved Brewster angle microscopy, reflectometry, ellipsometry, and shadow photography. First pump-probe reflectometry and ellipsometry measurements are performed on gold at λ _{probe}= 440 nm and three fluences of the single-pulsed pump radiation at λ _{pump}= 800 nm generating no, gentle, and strong ablation. The relative reflectance overall increases at no and gentle ablation. At strong ablation, the relative reflectance locally decreases, presumable caused by emitted thermal electrons, ballistic electrons, and ablating material. The refractive index n is slightly decreasing after excitation, while the extinction coefficient k is increasing.

Doping He droplets by laser ablation with a pulsed supersonic jet source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katzy, R.; Singer, M.; Izadnia, S.

Laser ablation offers the possibility to study a rich number of atoms, molecules, and clusters in the gas phase. By attaching laser ablated materials to helium nanodroplets, one can gain highly resolved spectra of isolated species in a cold, weakly perturbed system. Here, we present a new setup for doping pulsed helium nanodroplet beams by means of laser ablation. In comparison to more well-established techniques using a continuous nozzle, pulsed nozzles show significant differences in the doping efficiency depending on certain experimental parameters (e.g., position of the ablation plume with respect to the droplet formation, nozzle design, and expansion conditions).more » In particular, we demonstrate that when the ablation region overlaps with the droplet formation region, one also creates a supersonic beam of helium atoms seeded with the sample material. The processes are characterized using a surface ionization detector. The overall doping signal is compared to that of conventional oven cell doping showing very similar dependence on helium stagnation conditions, indicating a comparable doping process. Finally, the ablated material was spectroscopically studied via laser induced fluorescence.« less

A clinically feasible treatment protocol for magnetic resonance-guided high-intensity focused ultrasound ablation in the liver.

PubMed

Wijlemans, Joost W; de Greef, Martijn; Schubert, Gerald; Bartels, Lambertus W; Moonen, Chrit T W; van den Bosch, Maurice A A J; Ries, Mario

2015-01-01

Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) allows for noninvasive thermal ablation under real-time temperature imaging guidance. The purpose of this study was to assess the feasibility and safety of MR-HIFU ablation of liver tissue in a clinically acceptable setting. The experimental protocol was designed with a clinical ablation procedure of a small malignant tumor in mind; the procedures were performed within a clinically feasible time frame and care was taken to avoid adverse events. The main outcome was the size and quality of the ablated liver tissue volume on imaging and histology. Secondary outcomes were safety and treatment time. Healthy pigs (n = 10) under general anesthesia were positioned on a clinical MR-HIFU system, which consisted of an HIFU tabletop with a skin cooling system integrated into a 1.5-T MR scanner. A liver tissue volume was ablated with multiple sonication cells (4 × 4 × 10 mm, 450 W). Both MR thermometry and sonication were respiratory-gated using a pencil beam navigator on the diaphragm. Contrast-enhanced T1-weighted (CE-T1w) imaging was performed for treatment evaluation. Targeted total treatment time was 3 hours. The abdominal wall, liver, and adjacent organs were inspected postmortem for thermal damage. Ablated tissue volumes were processed for cell viability staining. The ablated volumes were analyzed using MR imaging, MR thermometry, and cell viability histology. Eleven volume ablations were performed in 10 animals, resulting in a median nonperfused volume (NPV) on CE-T1w imaging of 1.6 mL (interquartile range [IQR], 0.8-2.3; range, 0.7-3.0). Cell viability histology showed a damaged volume of 1.5 mL (IQR, 1.1-1.8; range, 0.7-2.3). The NPV was confluent in 10 of the 11 cases. The ablated tissue volume on cell viability histology was confluent in all 9 available cases. In all cases, there was a good correspondence between the aspects of the NPV on CE-T1w and the ablated volume on cell viability histology. Two treatment-related adverse events occurred: 1 animal had a 7-mm skin burn and 1 animal showed evidence of thermal damage on the surface of the spleen. Median ablation time was 108 minutes (IQR, 101-120; range, 96-181 minutes) and median total treatment time was 180 minutes (IQR, 165-224; 130-250 minutes). Our results demonstrate the feasibility and safety of MR-HIFU ablation of liver tissue volumes. The imaging data and cell viability histology show, for the first time, that confluent ablation volumes can be achieved with motion-gated ablation and MR guidance. These results were obtained using a readily available MR-HIFU system with only minor modifications, within a clinically acceptable time frame, and with only minor adverse events. This shows that this technique is sufficiently reliable and safe to initiate a clinical trial.

Alternate energy sources for catheter ablation.

PubMed

Wang, P J; Homoud, M K; Link, M S; Estes III, N A

1999-07-01

Because of the limitations of conventional radiofrequency ablation in creating large or linear lesions, alternative energy sources have been used as possible methods of catheter ablation. Modified radiofrequency energy, cryoablation, and microwave, laser, and ultrasound technologies may be able to create longer, deeper, and more controlled lesions and may be particularly suited for the treatment of ventricular tachycardias and for linear atrial ablation. Future studies will establish the efficacy of these new and promising technologies.

Accessory pathway ablation in a 6-year-old girl using remote magnetic navigation as an alternative to cryoablation.

PubMed

Mantziari, Lilian; Rigby, Michael; Till, Janice; Ernst, Sabine

2013-03-01

A 6-year-old girl with evidence of a parahisian accessory pathway on a baseline electrocardiogram underwent successful catheter ablation using magnetic navigation. Magnetic remote controlled ablation eliminated the parahisian pathway with the first radiofrequency application. A second anterolaterally located concealed pathway was successfully ablated in the same session, resulting in exclusively atrioventricular nodal conduction bidirectionally (total fluoroscopy, 4 min; 25 μGy).

Transgenic Reproductive Cell Ablation.

PubMed

Lawit, Shai J; Chamberlin, Mark A

2017-01-01

Numerous cell ablation technologies are available and have been used in reproductive tissues, particularly for male tissues and cells. The importance of ablation of reproductive tissues is toward a fundamental understanding reproductive tissue development and fertilization, as well as, in developing sterility lines important to breeding strategies. Here, we describe techniques for developing ablation lines for both male and female reproductive cells. Also discussed are techniques for analysis, quality control, maintenance, and the lessening of pleiotropism in such lines.

Improved model for the angular dependence of excimer laser ablation rates in polymer materials

NASA Astrophysics Data System (ADS)

Pedder, J. E. A.; Holmes, A. S.; Dyer, P. E.

2009-10-01

Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer's law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.

Emergency catheter ablation in critical patients

PubMed Central

Tebbenjohanns, Jürgen; Rühmkorf, Klaus

2010-01-01

Emergency catheter ablation is justified in critical patients with drug-refractory life-threatening arrhythmias. The procedure can be used for ablation of an accessory pathway in preexcitation syndrome with high risk of ventricular fibrillation and in patients with shock due to ischemic cardiomyopathy and incessant ventricular tachycardia. Emergency catheter ablation can also be justified in patients with an electrical storm of the implanted cardioverter-defibrillator or in patients with idiopathic ventricular fibrillation. PMID:20606793

Successful catheter ablation of a left anterior accessory pathway from the non-coronary cusp of the aortic valve.

PubMed

Laranjo, Sérgio; Oliveira, Mário; Trigo, Conceição

2015-08-01

Left anterior accessory pathways are considered to be rare findings. Catheter ablation of accessory pathways in this location remains a challenging target, and few reports about successful ablation of these accessory pathways are available. We describe our experience regarding a case of a manifest left anterior accessory pathway ablation using radiofrequency energy at the junction of the left coronary cusp with the non-coronary cusp.

Real-time airborne particle analyzer

DOEpatents

Reilly, Peter T.A.

2012-10-16

An aerosol particle analyzer includes a laser ablation chamber, a gas-filled conduit, and a mass spectrometer. The laser ablation chamber can be operated at a low pressure, which can be from 0.1 mTorr to 30 mTorr. The ablated ions are transferred into a gas-filled conduit. The gas-filled conduit reduces the electrical charge and the speed of ablated ions as they collide and mix with buffer gases in the gas-filled conduit. Preferably, the gas filled-conduit includes an electromagnetic multipole structure that collimates the nascent ions into a beam, which is guided into the mass spectrometer. Because the gas-filled conduit allows storage of vast quantities of the ions from the ablated particles, the ions from a single ablated particle can be analyzed multiple times and by a variety of techniques to supply statistically meaningful analysis of composition and isotope ratios.

Effect of ZrO2 Powders on the Pyrolysis of Polycarbosilanes Coating Under Laser Ablation

NASA Astrophysics Data System (ADS)

Cheng, Han; Chen, Zhaofeng; Tao, Jie; Yan, Bo; Li, Cong; Wang, Liangbing; Zhang, Ying; Fang, Dan; Wan, Shuicheng; Wu, Wangping

Aircrafts hold the outstanding mastery of the sky in modern wars, however the laser beam weapons can carry out laser attacking to aircrafts. The purpose of the present paper is to research on a new type laser protective material. Polycarbosilanes (PCS)/divinylbenzene mixtures containing ZrO2 powders were brushed to the surface of the aluminum alloy plates and then cured at 150°C for 6 h. The PCS-coated plates were ablated by laser for 3 s. The phase identification of as-ablated powders was examined by X-ray diffraction. The results indicated that the as-ablated powders of cured PCS were composed of major phase β-SiC and smaller amounts of free carbon. The PCS composite coating played a certain role of laser ablation resistance. The effect of added ZrO2 powders on the pyrolysis of PCS-coating under laser ablation is conspicuous.

High-intensity focused ultrasound ablation induced apoptosis in human hepatocellular carcinoma.

PubMed

Yi, Jiang; Wu, Liguo; Liu, Zhou; Zou, Haibo; Li, Ning; Chen, Heping; Liu, Jinheng; Li, Tao; Zhang, Gang

2014-01-01

To evaluate the effect of high-intensity ultrasound (HIFU) ablation on human hepatocellular carcinoma tissues and apoptotic proteins (bcl-2 and p-53). Patients with hepatocellular carcinoma at stage B were treated with HIFU ablation. Levels of bcl-2 and p53 protein and the apoptosis rate were evaluated both in the pre-treatment and post-treatment tissue specimens using immunochemistry and TUNEL methods, respectively. After HIFU ablation, p53 protein levels were significantly increased around the coagulation necrosis area, whereas, the level of bcl-2 was significantly decreased. More apoptosis cells were found post ablation compared with those in the pretreatment tissues. Additionally, no significant correlation was found between p53/bcl-2 levels and apoptotic index. HIFU ablation may exert promote the apoptosis of hepatocellular carcinoma cells and the effect has a closely association with the change of p53 and bcl-2 expression.

Artificial meteor ablation studies - Iron oxides.

NASA Technical Reports Server (NTRS)

Blanchard, M. B.

1972-01-01

Artificial meteor ablation was performed on natural minerals composed predominantly of magnetite and hematite by using an arc-heated plasma stream of air. Analysis indicates that most of the ablated debris was composed of two or more minerals. Wustite, a metastable mineral, was found to occur as a common product. The 'magnetite' sample, which was 80% magnetite, 14% hematite, 4% apatite, and 2% quartz, yielded ablated products consisting of more than 12 different minerals. Magnetite occurred in 91% of the specimens examined, hematite in 16%, and wustite in 30%. The 'hematite' sample, which was 96% hematite and 3% quartz, yielded ablated products consisting of more than 13 different minerals. Hematite occurred in 47% of the specimens examined, magnetite in 60%, and wustite in 28%. The more volatile elements (Si, P, and Cl) were depleted by about 50%. This study has shown that artificially created ablation products from iron oxides exhibit unique properties that can be used for identification.

Atriocaval Rupture After Right Atrial Isthmus Ablation for Atrial Flutter.

PubMed

Vloka, Caroline; Nelson, Daniel W; Wetherbee, Jule

2016-06-01

A patient with symptomatic typical atrial flutter (AFL) underwent right atrial isthmus ablation with an 8-mm catheter. Eight months later, his typical AFL recurred. Ten months later, he underwent a repeat right atrial isthmus ablation with an irrigated tip catheter and an 8-mm tip catheter. Six weeks after his second procedure, while performing intense sprint intervals on a treadmill, he developed an abrupt onset of chest pain, hypotension, and cardiac tamponade. He underwent emergency surgery to repair an atriocaval rupture and has done well since. Our report suggests that an association of multiple radiofrequency ablations with increased risk for delayed atriocaval rupture occurring 1 to 3 months after ablation. In conclusion, although patients generally were advised to limit exercise for 1 to 2 weeks after AFL ablation procedures in the past, it may be prudent to avoid intense exercise for at least 3 months after procedure. Copyright © 2016 Elsevier Inc. All rights reserved.

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

NASA Technical Reports Server (NTRS)

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

2011-01-01

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

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

NASA Astrophysics Data System (ADS)

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.

Theoretical and experimental analysis of the impact on ablation depth of microchannel milling using femtosecond laser

NASA Astrophysics Data System (ADS)

Lei, Chen; Pan, Zhang; Jianxiong, Chen; Tu, Yiliu

2018-04-01

The plasma brightness cannot be used as a direct indicator of ablation depth detection by femtosecond laser was experimentally demonstrated, which led to the difficulty of depth measurement in the maching process. The tests of microchannel milling on the silicon wafer were carried out in the micromachining center in order to obtain the influences of parameters on the ablation depth. The test results showed that the defocusing distance had no significant impact on ablation depth in LAV effective range. Meanwhile, the reason of this was explained in this paper based on the theoretical analysis and simulation calculation. Then it was proven that the ablation depth mainly depends on laser fluence, step distance and scanning velocity. Finally, a research was further carried out to study the laser parameters which relate with the microchannel ablation depth inside the quartz glass for more efficiency and less cost in processing by femtosecond laser.

Molybdenum oxide nanocolloids prepared by an external field-assisted laser ablation in water

NASA Astrophysics Data System (ADS)

Spadaro, Salvatore; Bonsignore, Martina; Fazio, Enza; Cimino, Francesco; Speciale, Antonio; Trombetta, Domenico; Barreca, Francesco; Saija, Antonina; Neri, Fortunato

2018-01-01

he synthesis of extremely stable molybdenum oxide nanocolloids by pulsed laser ablation was studied. This green technique ensures the formation of contaminant-free nanostructures and the absence of by-products. A focused picosecond pulsed laser beam was used to ablate a solid molybdenum target immersed in deionized water. Molybdenum oxide nearly spherical nanoparticles with dimensions within few nanometers (20-100 nm) are synthesized when the ablation processes were carried out, in water, at room temperature and 80°C. The application of an external electric field during the ablation process induces a nanostructures reorganization, as indicated by Scanning-Transmission Electron Microscopy images analysis. The ablation products were also characterized by some spectroscopic techniques: conventional UV-vis optical absorption, atomic absorption, dynamic light scattering, micro-Raman and X-ray photoelectron spectroscopies. Finally, NIH/3T3 mouse fibroblasts were used to evaluate cell viability by the sulforhodamine B assay

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

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-02-01

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

[Radiofrequency ablation of hepatocellular carcinoma].

PubMed

Widmann, Gerlig; Schullian, Peter; Bale, Reto

2013-03-01

Percutaneous radiofrequency ablation (RFA) is well established in the treatment of hepatocellular carcinoma (HCC). Due to its curative potential, it is the method of choice for non resectable BCLC (Barcelona Liver Clinic) 0 and A. RFA challenges surgical resection for small HCC and is the method of choice in bridging for transplantation and recurrence after resection or transplantation. The technical feasibility of RFA depends on the size and location of the HCC and the availability of ablation techniques (one needle techniques, multi-needle techniques). More recently, stereotactic multi-needle techniques with 3D trajectory planning and guided needle placement substantially improve the spectrum of treatable lesions including large volume tumors. Treatment success depends on the realization of ablations with large intentional margins of tumor free tissue (A0 ablation in analogy to R0 resection), which has to be documented by fusion of post- with pre-ablation images, and confirmed during follow-up imaging.

Laser ablation efficiency during the production of Ag nanoparticles in ethanol at a low pulse repetition rate (1-10 Hz)

NASA Astrophysics Data System (ADS)

Valverde-Alva, M. A.; García-Fernández, T.; Esparza-Alegría, E.; Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R.; de la Mora, M. B.; Márquez-Herrera, C. E.; Sánchez Llamazares, J. L.

2016-10-01

We studied the effect of the repetition rate of laser pulses (RRLP) in the range from 1-10 Hz in the production of silver nanoparticles (Ag-NPs) by laser ablation in ethanol. Laser pulses with a duration of 7 ns, a wavelength of 1064 nm and an energy of 60 mJ were used to ablate a 99.99% pure silver target immersed in 10 ml of ethanol. Transmittance analysis and atomic absorption spectroscopy were used to study the silver concentration in the colloidal solutions. The ablation process was studied by measuring the transmission of the laser pulses through the colloid. It is shown that for a fixed number of laser pulses (NLP) the ablation efficiency, in terms of the ablated silver mass per laser pulse, increases with the RRLP. This result contradicts what had previously been established in the literature.

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

PubMed

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

2008-08-01

[Figure: see text]. Laser ablation harnesses photon energy to remove material from a surface. Although applications such as laser-assisted in situ keratomileusis (LASIK) surgery, lithography, and nanoscale device fabrication take advantage of this process, a better understanding the underlying mechanism of ablation in polymeric materials remains much sought after. Molecular simulation is a particularly attractive technique to study the basic aspects of ablation because it allows control over specific process parameters and enables observation of microscopic mechanistic details. This Account describes a hybrid molecular dynamics-Monte Carlo technique to simulate laser ablation in poly(methyl methacrylate) (PMMA). It also discusses the impact of thermal and chemical excitation on the ensuing ejection processes. We used molecular dynamics simulation to study the molecular interactions in a coarse-grained PMMA substrate following photon absorption. To ascertain the role of chemistry in initiating ablation, we embedded a Monte Carlo protocol within the simulation framework. These calculations permit chemical reactions to occur probabilistically during the molecular dynamics calculation using predetermined reaction pathways and Arrhenius rates. With this hybrid scheme, we can examine thermal and chemical pathways of decomposition separately. In the simulations, we observed distinct mechanisms of ablation for each type of photoexcitation pathway. Ablation via thermal processes is governed by a critical number of bond breaks following the deposition of energy. For the case in which an absorbed photon directly causes a bond scission, ablation occurs following the rapid chemical decomposition of material. A detailed analysis of the processes shows that a critical energy for ablation can describe this complex series of events. The simulations show a decrease in the critical energy with a greater amount of photochemistry. Additionally, the simulations demonstrate the effects of the energy deposition rate on the ejection mechanism. When the energy is deposited rapidly, not allowing for mechanical relaxation of the sample, the formation of a pressure wave and subsequent tensile wave dominates the ejection process. This study provides insight into the influence of thermal, chemical, and mechanical processes in PMMA and facilitates greater understanding of the complex nature of polymer ablation. These simulations complement experiments that have used chemical design to harness the photochemical properties of materials to enhance laser ablation. We successfully fit the results of the simulations to established analytical models of both photothermal and photochemical ablation and demonstrate their relevance. Although the simulations are for PMMA, the mechanistic concepts are applicable to a large range of systems and provide a conceptual foundation for interpretation of experimental data.

Hepatic Radiofrequency Ablation–induced Stimulation of Distant Tumor Growth Is Suppressed by c-Met Inhibition

PubMed Central

Kumar, Gaurav; Moussa, Marwan; Wang, Yuanguo; Rozenblum, Nir; Galun, Eithan; Goldberg, S. Nahum

2016-01-01

Purpose To elucidate how hepatic radiofrequency (RF) ablation affects distant extrahepatic tumor growth by means of two key molecular pathways. Materials and Methods Rats were used in this institutional animal care and use committee–approved study. First, the effect of hepatic RF ablation on distant subcutaneous in situ R3230 and MATBIII breast tumors was evaluated. Animals were randomly assigned to standardized RF ablation, sham procedure, or no treatment. Tumor growth rate was measured for 3½ to 7 days. Then, tissue was harvested for Ki-67 proliferative indexes and CD34 microvascular density. Second, hepatic RF ablation was performed for hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and c-Met receptor expression measurement in periablational rim, serum, and distant tumor 24 hours to 7 days after ablation. Third, hepatic RF ablation was combined with either a c-Met inhibitor (PHA-665752) or VEGF receptor inhibitor (semaxanib) and compared with sham or drug alone arms to assess distant tumor growth and growth factor levels. Finally, hepatic RF ablation was performed in rats with c-Met–negative R3230 tumors for comparison with the native c-Met–positive line. Tumor size and immunohistochemical quantification at day 0 and at sacrifice were compared with analysis of variance and the two-tailed Student t test. Tumor growth curves before and after treatment were analyzed with linear regression analysis to determine mean slopes of pre- and posttreatment growth curves on a per-tumor basis and were compared with analysis of variance and paired two-tailed t tests. Results After RF ablation of normal liver, distant R3230 tumors were substantially larger at 7 days compared with tumors treated with the sham procedure and untreated tumors, with higher growth rates and tumor cell proliferation. Similar findings were observed in MATBIII tumors. Hepatic RF ablation predominantly increased periablational and serum HGF and downstream distant tumor VEGF levels. Compared with RF ablation alone, RF ablation combined with adjuvant PHA-665752 or semaxanib reduced distant tumor growth, proliferation, and microvascular density. For c-Met–negative tumors, hepatic RF ablation did not increase distant tumor growth, proliferation, or microvascular density compared with sham treatment. Conclusion RF ablation of normal liver can stimulate distant subcutaneous tumor growth mediated by HGF/c-Met pathway and VEGF activation. This effect was not observed in c-Met–negative tumors and can be blocked with adjuvant c-Met and VEGF inhibitors. © RSNA, 2015 PMID:26418615

Loss of pace capture on the ablation line: a new marker for complete radiofrequency lesions to achieve pulmonary vein isolation.

PubMed

Steven, Daniel; Reddy, Vivek Y; Inada, Keiichi; Roberts-Thomson, Kurt C; Seiler, Jens; Stevenson, William G; Michaud, Gregory F

2010-03-01

Catheter ablation procedures for atrial fibrillation (AF) often involve circumferential antral isolation of pulmonary veins (PV). Inability to reliably identify conduction gaps on the ablation line necessitates placing additional lesions within the intended lesion set. This pilot study investigated the relationship between loss of pace capture directly along the ablation line and electrogram criteria for PV isolation (PVI). Using a 3-dimensional anatomic mapping system and irrigated-tip radiofrequency (RF) ablation catheter, lesions were placed in the PV antra to encircle ipsilateral vein pairs until pace capture at 10 mA/2 ms no longer occurred along the line. During ablation, a circular mapping catheter was placed in an ipsilateral PV, but the electrograms were not revealed until loss-of-pace capture. The procedural end point was PVI (entrance and exit block). Thirty patients (57 +/- 12 years; 15 male [50%]) undergoing PVI in 2 centers (3 primary operators) were included (left atrial diameter 40 +/- 4 mm, left ventricular ejection fraction 60 +/- 7%). All patients reached the end points of complete PVI and loss of pace capture. When PV electrograms were revealed after loss of pace capture along the line, PVI was present in 57 of 60 (95%) vein pairs. In the remaining 3 of 60 (5%) PV pairs, further RF applications achieved PVI. The procedure duration was 237 +/- 46 minutes, with a fluoroscopy time of 23 +/- 9 minutes. Analysis of the blinded PV electrograms revealed that even after PVI was achieved, additional sites of pace capture were present on the ablation line in 30 of 60 (50%) of the PV pairs; 10 +/- 4 additional RF lesions were necessary to fully achieve loss of pace capture. After ablation, the electrogram amplitude was lower at unexcitable sites (0.25 +/- 0.15 mV vs. 0.42 +/- 0.32 mV, P < .001), but there was substantial overlap with pace capture sites, suggesting that electrogram amplitude lacks specificity for identifying pace capture sites. Complete loss of pace capture directly along the circumferential ablation line correlates with entrance block in 95% of vein pairs and can be achieved without circular mapping catheter guidance. Thus, pace capture along the ablation line can be used to identify conduction gaps. Interestingly, more RF ablation energy was required to achieve loss of pace capture along the ablation line than for entrance block into PVs. Further study is warranted to determine whether this method results in more durable ablation lesions that reduce recurrence of AF. Copyright 2010 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Optimization of the generator settings for endobiliary radiofrequency ablation.

PubMed

Barret, Maximilien; Leblanc, Sarah; Vienne, Ariane; Rouquette, Alexandre; Beuvon, Frederic; Chaussade, Stanislas; Prat, Frederic

2015-11-10

To determine the optimal generator settings for endobiliary radiofrequency ablation. Endobiliary radiofrequency ablation was performed in live swine on the ampulla of Vater, the common bile duct and in the hepatic parenchyma. Radiofrequency ablation time, "effect", and power were allowed to vary. The animals were sacrificed two hours after the procedure. Histopathological assessment of the depth of the thermal lesions was performed. Twenty-five radiofrequency bursts were applied in three swine. In the ampulla of Vater (n = 3), necrosis of the duodenal wall was observed starting with an effect set at 8, power output set at 10 W, and a 30 s shot duration, whereas superficial mucosal damage of up to 350 μm in depth was recorded for an effect set at 8, power output set at 6 W and a 30 s shot duration. In the common bile duct (n = 4), a 1070 μm, safe and efficient ablation was obtained for an effect set at 8, a power output of 8 W, and an ablation time of 30 s. Within the hepatic parenchyma (n = 18), the depth of tissue damage varied from 1620 μm (effect = 8, power = 10 W, ablation time = 15 s) to 4480 μm (effect = 8, power = 8 W, ablation time = 90 s). The duration of the catheter application appeared to be the most important parameter influencing the depth of the thermal injury during endobiliary radiofrequency ablation. In healthy swine, the currently recommended settings of the generator may induce severe, supratherapeutic tissue damage in the biliary tree, especially in the high-risk area of the ampulla of Vater.

Limitations of dormant conduction as a predictor of atrial fibrillation recurrence and pulmonary vein reconnection after catheter ablation.

PubMed

Lin, Frank S; Ip, James E; Markowitz, Steven M; Liu, Christopher F; Thomas, George; Lerman, Bruce B; Cheung, Jim W

2015-05-01

Adenosine (ADO) can uncover dormant conduction following pulmonary vein (PV) isolation. We sought to identify the value of dormant conduction for predicting atrial fibrillation (AF) recurrence and chronic PV reconnection. One hundred fifty-two patients (80 male; age 60 ± 11 years) undergoing PV isolation for AF were studied. After PV isolation, sites of ADO-induced PV reconnection were recorded and targeted with additional ablation. In patients undergoing repeat ablation for recurrent AF, chronic PV reconnection was assessed. Forty-five (30%) patients had ADO-induced PV reconnection following PV isolation. Dormant conduction was successfully eliminated with additional ablation in 41 (91%) of these patients. After follow-up of 598 ± 270 days, 60 (39%) patients had recurrent AF. Dormant PV conduction was not a significant predictor of AF recurrence (hazard ratio 1.51; 95% confidence interval: 0.89-2.56; P = 0.12) although three of four (75%) patients with residual dormant conduction following initial ablation developed recurrent AF. Twenty-six patients with recurrent AF underwent repeat ablation with 52 of 99 (53%) PVs found to have chronic reconnection. Nine of 11 (82%) PVs with dormant conduction and 43 of 88 (49%) PVs without dormant conduction at initial procedure had chronic reconnection at repeat ablation. When additional ablation is performed to eliminate ADO-induced PV reconnection after PV isolation, dormant conduction is not a significant predictor of recurrent AF. Although PVs with dormant conduction at initial procedure may develop chronic reconnection, the majority of PVs that show conduction recovery at repeat ablation occur in nondormant PVs. © 2015 Wiley Periodicals, Inc.

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

PubMed

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

2017-03-01

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

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

PubMed

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

2010-01-01

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

Remodeling of sinus node function after catheter ablation of right atrial flutter.

PubMed

Daoud, Emile G; Weiss, Raul; Augostini, Ralph S; Kalbfleisch, Steven J; Schroeder, Jason; Polsinelli, Georgia; Hummel, John D

2002-01-01

The purpose of this study was to investigate the effect of ablation of right atrial flutter upon sinus node function in humans. This study enrolled 35 patients. Twenty-four patients (16 men and 8 women; age 68 +/- 11 years) were referred for ablation of persistent atrial flutter (duration 8 +/- 11 months). After ablation, there was abnormal sinus node function defined as a corrected sinus node recovery time (CSNRT) > or = 550 msec. The control group consisted of 11 patients who were undergoing pacemaker implantation for sinus node disease but did not have a history of atrial dysrhythmias or ablation. Within 24 hours of ablation or pacemaker implantation, baseline maximal CSNRT was measured through a permanent pacemaker by AAI pacing at six cycle lengths: 600, 550, 500, 450, 400, and 350 msec. CSNRT then was measured in the same manner at 48 hours, 14 days, and 3 months after ablation/pacemaker implantation. P wave amplitude and duration, and percent atrial sensing also were assessed at the same intervals. For patients undergoing atrial flutter ablation, there was progressive temporal recovery of CSNRT (1,204 +/- 671 msec at baseline vs 834 +/- 380 msec at 3 months; P < 0.001) and a significant increase in the percent atrial sensing and P wave amplitude at 3 months compared with baseline (P < 0.001). In control subjects, there was no change in the CSNRT, percent atrial pacing, or P wave amplitude. After ablation of persistent atrial flutter, there is temporal recovery of CSNRT and increase in spontaneous atrial activity. These findings suggest that atrial flutter induces reversible changes in sinus node function.

High-intensity focused ultrasound ablation of myocardium in vivo and instantaneous biological response.

PubMed

Zheng, Minjuan; Shentu, Weihui; Chen, Dingzhang; Sahn, David J; Zhou, Xiaodong

2014-10-01

This study aimed to evaluate the instantaneous biological response of canine myocardium in vivo to high-intensity focused ultrasound (HIFU) ablation, and thereby determine the feasibility of this method. Left ventricle myocardium HIFU ablation was performed on six dogs at four levels of HIFU energy (acoustic intensity was 3000 W/cm2 ; ablation durations were 1.2, 2.4, 3.6, and 4.8 sec, respectively). Gross lesion volumes were confirmed and assessed by tetrazolium chloride (TTC) staining, hematoxylin-eosin (HE) staining, and electron microscopy. Global cardiac function and focal wall motion were evaluated by echocardiography. Blood enzymes and cardiac troponin T (CTnT) were tested after ablation. HIFU ablation was repeated on another set of six fresh canine hearts in vitro at the same four energy levels. Focal maximum temperatures were detected both in vivo and in vitro. Different sizes of ablation via HIFU can be created in beating hearts using controlled energy emission. Focal maximum temperatures varied from 62 ± 4.8 °C to 81 ± 12.9 °C. The lesion sizes were significantly smaller in vivo than in vitro, as verified by TTC and HE staining. Focal wall motion immediately decreased after ablation (P < 0.05), although the ejection fraction (EF) and E/A ratio were unchanged (P > 0.05). Enzymes and CTnT immediately increased. HIFU can be used for the controllable ablation of myocardial tissue, with instantly increased serum markers, decreased regional wall motion, and unaffected left ventricular global function. © 2014, Wiley Periodicals, Inc.

Comparison of separation performance of laser-ablated and wet-etched microfluidic devices

PubMed Central

Baker, Christopher A.; Bulloch, Rayford; Roper, Michael G.

2010-01-01

Laser ablation of glass allows for production of microfluidic devices without the need of hydrofluoric acid and photolithography. The goal of this study was to compare the separation performance of microfluidic devices produced using a low-cost laser ablation system and conventional wet etching. During laser ablation, cracking of the glass substrate was prevented by heating the glass to 300°C. A range of laser energy densities was found to produce channel depths ranging from 4 – 35 μm and channel widths from 118 – 162 μm. The electroosmotic flow velocity was lower in laser-ablated devices, 0.110 ± 0.005 cm s−1, as compared to wet-etched microfluidic chips, 0.126 ± 0.003 cm s−1. Separations of both small and large molecules performed on both wet- and laser-ablated devices were compared by examining limits of detection, theoretical plate count, and peak asymmetry. Laser-induced fluorescence detection limits were 10 pM fluorescein for both types of devices. Laser-ablated and wet-etched microfluidic chips had reproducible migration times with ≤ 2.8% RSD and peak asymmetries ranging from 1.0 – 1.8. Numbers of theoretical plates were between 2.8- and 6.2-fold higher on the wet-etched devices compared to laser-ablated devices. Nevertheless, resolution between small and large analytes was accomplished, which indicates that laser ablation may find an application in pedagogical studies of electrophoresis or microfluidic devices, or in settings where hydrofluoric acid cannot be used. PMID:20827468

Assessing the accuracy of Greenland ice sheet ice ablation measurements by pressure transducer

NASA Astrophysics Data System (ADS)

Fausto, R. S.; van As, D.; Ahlstrøm, A. P.

2012-04-01

In the glaciological community there is a need for reliable mass balance measurements of glaciers and ice sheets, ranging from daily to yearly time scales. Here we present a method to measure ice ablation using a pressure transducer. The pressure transducer is drilled into the ice, en-closed in a hose filled with a liquid that is non-freezable at common Greenlandic temperatures. The pressure signal registered by the transducer is that of the vertical column of liquid over the sensor, which can be translated in depth knowing the density of the liquid. As the free-standing AWS moves down with the ablating surface and the hose melts out of the ice, an increasingly large part of the hose will lay flat on the ice surface, and the hydrostatic pressure from the vertical column of liquid in the hose will get smaller. This reduction in pressure provides us with the ablation rate. By measuring at (sub-) daily timescales this assembly is well-suited to monitor ice ablation in remote regions, with clear advantages over other well-established methods of measuring ice ablation in the field. The pressure transducer system has the potential to monitor ice ablation for several years without re-drilling and the system is suitable for high ablation areas. A routine to transform raw measurements into ablation values will also be presented, including a physically based method to remove air pressure variability from the signal. The pressure transducer time-series is compared to that recorded by a sonic ranger for the climatically hostile setting on the Greenland ice sheet.

Characteristics of laparoscopic microwave ablation with renal tissue: Experimental in vivo study using a porcine model.

PubMed

Hong, Baoan; Du, Xin; Zhao, Yuan; Chen, Guowei; Zhang, Xiaodong; Zhang, Ning; Yang, Yong

2015-01-01

A model of in vivo porcine kidneys is used to clarify the characteristics of laparoscopic microwave ablation (MWA) of renal tissue. Six pigs were utilised for the experiment using 18G water circulating-cooling microwave needles. The operating frequency was 2450 MHz, and the independent variables were power (50-60 W) and time (300-600 s). The kidneys were dissociated laparoscopically and ablated with a single or double needle at different power/time combinations and depths of puncture. Changes in the kidneys were carefully observed. Specimens of the ablated lesions were stained with haematoxylin-eosin (H&E) to evaluate the pathological features. Thirty-four thermoablations were applied. The effective ablation shape was similar to a chestnut. The ablated lesions could be divided into three zones: carbonization zone, coagulation zone, and inflammatory reaction zone. The ablation zone enlarged with increasing power and time. When combined with two needles, the maximum diameter of the ablated lesions significantly increased. Pathological results indicated that renal tissues of the carbonisation zone were thoroughly necrotic. Coagulative necrosis was observed in the coagulation zone. No 'skipped' areas were noted in any ablation zone. The structure of the inflammatory reaction zone was integrated, and interstitial small blood vessels were highly expanded and congested with infiltrated inflammatory cells. MWA achieved excellent effects in this porcine model. It can be safely and effectively used in renal tissue. For patients with poor physical condition or small renal masses (<4 cm), we can refer to these data and select the appropriate combinations to obtain satisfactory therapeutic efficacy.

Slow pathway radiofrequency ablation in patients with AVNRT: junctional rhythm is less frequent during magnetic navigation ablation than with the conventional technique.

PubMed

Ricard, Philippe; Latcu, Decebal Gabriel; Yaïci, Khelil; Zarqane, Naima; Saoudi, Nadir

2010-01-01

The occurrence of accelerated junctional rhythm (JR) during radiofrequency ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT) is frequent. The aim of the present study was to compare the occurrence of JR during magnetic remote catheter ablation to the conventional manual ablation. Twenty six patients (males: seven; age: 51 + or - 15 years) underwent slow pathway ablation with magnetic navigation (MN) system (Niobe, Stereotaxis Inc., St. Louis, MO, USA) and were compared to a control group of 11 patients (males: three; age: 53 + or - 16 years) treated with conventional manual ablation. A 4-mm nonirrigated tip catheter was used in both groups with a maximum of 30 W and 60 degrees C. Acute success was obtained in all patients. In the MN group, three patients out of 24 had no junctional beat (JB) at all and seven patients had 10 or less JB. In contrast, in the conventional group no patient had less than 10 JB. The mean number of JB in the MN group was 66 + or - 94.9 (0-410) and 200 + or - 243.1 (43-914) in the control group (P = 0.019). In the MN group one patient had a first-degree atrioventricular block. No other complication occurred. Magnetic remote catheter ablation of AVNRT is effective and is associated with less JB than the manual conventional technique. Therefore, JB may not be considered as a mandatory indicator for successful AVNRT ablation with MN system.

Right atrium positioning for exposure of right pulmonary veins during off-pump atrial fibrillation ablation.

PubMed

Suwalski, Grzegorz; Emery, Robert; Mróz, Jakub; Kaczejko, Kamil; Gryszko, Leszek; Cwetsch, Andrzej; Skrobowski, Andrzej

2017-06-01

Concomitant surgical ablation of atrial fibrillation (AF) is recommended for patients undergoing off-pump coronary revascularization in the presence of this arrhythmia. Achievement of optimal visualization of pulmonary veins while maintaining stable haemodynamic conditions is crucial for proper completion of the ablation procedure. This study evaluates the safety and feasibility of right atrial positioning using a suction-based cardiac positioner as opposed to compressive manoeuvres for exposure during off-pump surgical ablation for AF. Thirty-four consecutive patients underwent pulmonary vein isolation, ganglionated plexi ablation and left atrial appendage occlusion during off-pump coronary artery bypass grafting. Right atrial suction positioning was used to visualize right pulmonary veins. Safety and feasibility end points were analysed intraoperatively and in the early postoperative course. In all patients, right atrial positioning created optimal conditions to complete transverse and oblique sinus blunt dissection, correct placement of a bipolar ablation probe, detection and ablation of ganglionated plexi and conduction block assessment. In all patients, this entire right-sided ablation procedure was completed with a single exposure manoeuvre. Feasibility end points were achieved in all study patients. This report documents the safety and feasibility of right atrial exposure using a suction-based cardiac positioner to complete ablation for AF concomitant with off-pump coronary revascularization. This technique may be widely adopted to create stable haemodynamic conditions and optimal visualization of the right pulmonary veins. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

On the role of snow cover ablation variability and synoptic-scale atmospheric forcings at the sub-basin scale within the Great Lakes watershed

NASA Astrophysics Data System (ADS)

Suriano, Zachary J.

2018-02-01

Synoptic-scale atmospheric conditions play a critical role in determining the frequency and intensity of snow cover ablation in the mid-latitudes. Using a synoptic classification technique, distinct regional circulation patterns influencing the Great Lakes basin of North America are identified and examined in conjunction with daily snow ablation events from 1960 to 2009. This approach allows for the influence of each synoptic weather type on ablation to be examined independently and for the monthly and inter-annual frequencies of the weather types to be tracked over time. Because of the spatial heterogeneity of snow cover and the relatively large geographic extent of the Great Lakes basin, snow cover ablation events and the synoptic-scale patterns that cause them are examined for each of the Great Lakes watershed's five primary sub-basins to understand the regional complexities of snow cover ablation variability. Results indicate that while many synoptic weather patterns lead to ablation across the basins, they can be generally grouped into one of only a few primary patterns: southerly flow, high-pressure overhead, and rain-on-snow patterns. As expected, the patterns leading to ablation are not necessarily consistent between the five sub-basins due to the seasonality of snow cover and the spatial variability of temperature, moisture, wind, and incoming solar radiation associated with the particular synoptic weather types. Significant trends in the inter-annual frequency of ablation-inducing synoptic types do exist for some sub-basins, indicating a potential change in the hydrologic impact of these patterns over time.

Highly efficient nonthermal ablation of bone under bulk water with a frequency-doubled Nd:YVO4 picosecond laser

NASA Astrophysics Data System (ADS)

Tulea, C.; Caron, J.; Wahab, H.; Gehlich, N.; Hoefer, M.; Esser, D.; Jungbluth, B.; Lenenbach, A.; Noll, R.

2013-03-01

Several laser systems in the infrared wavelength range, such as Nd:YAG, Er:YAG or CO2 lasers are used for efficient ablation of bone tissue. Here the application of short pulses in coaction with a thin water film results in reduced thermal side effects. Nonetheless up to now there is no laser-process for bone cutting in a clinical environment due to lack of ablation efficiency. Investigations of laser ablation rates of bone tissue using a rinsing system and concerning bleedings have not been reported yet. In our study we investigated the ablation rates of bovine cortical bone tissue, placed 1.5 cm deep in water under laminar flow conditions, using a short pulsed (25 ps), frequency doubled (532 nm) Nd:YVO4 laser with pulse energies of 1 mJ at 20 kHz repetition rate. The enhancement of the ablation rate due to debris removal by an additional water flow from a well-directed blast pipe as well as the negative effect of the admixture of bovine serum albumin to the water were examined. Optical Coherence Tomography (OCT) was used to measure the ablated volume. An experimental study of the depth dependence of the ablation rate confirms a simplified theoretical prediction regarding Beer-Lambert law, Fresnel reflection and a Gaussian beam profile. Conducting precise incisions with widths less than 1.5 mm the maximum ablation rate was found to be 0.2 mm3/s. At depths lower than 100 μm, while the maximum depth was 3.5 mm.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Dong; Brace, Christopher L., E-mail: clbrace@wisc.edu

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

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

PubMed

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.

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

PubMed Central

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

2017-01-01

Background: Treatment of adrenal metastasis from lung carcinoma may prolong survival in the selected patients. However, not all patients can undergo surgery; thus, minimally invasive ablation procedures such as radiofrequency ablation (RFA) and microwave ablation (MWA) have gained acceptance as alternative treatment methods. This study summarized a 5-year single-center experience regarding the evaluation of safety and efficacy of computed tomography (CT)-guided thermal ablation in the management of adrenal metastasis originating from non-small cell lung cancer (NSCLC). Methods: The data of NSCLC patients ablated for adrenal metastasis at the Department of Diagnostic Imaging and Interventional Radiology, General Hospital Sotiria, were retrospectively analyzed. Patients were divided into two groups: RFA group and MWA group according to the therapeutic approaches. Preprocedural blood tests included measurement of international normalized ratio, partial thromboplastin time, and platelet enumeration. A dual-phase contrast-enhanced spiral CT was performed immediately after the procedure to assess the immediate response after ablation and to screen for related complications. Follow-up was performed with CT or magnetic resonance imaging at 1, 3, 6 months and 1 year after ablation and every 6 months thereafter. Results: A total of 99 ablation sessions in 71 patients with adrenal metastasis originating from NSCLC were included in the final analysis. Self-limited, postablation syndrome occurred in 16/99 (16.1%) of ablation sessions. All procedures were technically successful. Immediate postablation imaging showed no contrast enhancement of the ablated tumor in all patients. Follow-up imaging at 3 months revealed local tumor progression in 8 (22.8%) patients of the RFA group and 7 (19.4%) patients of MWA group, all of them underwent a second session successfully. The 1-year assessment revealed local recurrence of the ablated tumor in six patients (17.1%) of RFA group and seven patients (19.4%) of MWA group. Among these 71 patients, those with tumor size >3.5 cm had a higher local recurrence rate (65.2%, 15/23) than those with tumors ≤3.5 cm (16.7%, 8/48; P = 0.012). There was no significant difference in the median survival time between RFA (14.0 months) and MWA (14.6 months) groups (P > 0.05). Conclusions: RFA and MWA showed comparable efficacy and safety in adrenal metastasis treatment. PMID:28707652

Radiofrequency catheter ablation of Type 1 atrial flutter using a large-tip electrode catheter and high-power radiofrequency energy generator.

PubMed

Feld, Gregory K

2004-11-01

Recent studies have demonstrated a high degree of efficacy of 8 mm electrode-tipped or saline-irrigated-tip catheters for ablation of atrial flutter (AFL). These catheters have a theoretical advantage as they produce a large ablation lesion. However, large-tip ablation catheters have a larger surface area and require a higher power radiofrequency (RF) generator with up to 100 W capacity to produce adequate ablation temperatures (50-60 degrees C). The potential advantages of a large-tip ablation catheter and high-power RF generator include the need for fewer energy applications, shorter procedure and fluoroscopy times, and greater efficacy. Therefore, the safety and efficacy of AFL ablation using 8 or 10 mm electrode catheters and a 100-W RF generator was studied using the Boston Scientific, Inc., EPT-1000 XP cardiac ablation system. There were 169 patients, aged 61 +/- 12 years involved. Acute end points were bidirectional isthmus block and no inducible AFL. Following ablation, patients were seen at 1, 3 and 6 months, with event monitoring performed weekly and for any symptoms. Three quality of life surveys were completed during follow-up. Acute success was achieved in 158 patients (93%), with 12 +/- 11 RF energy applications. The efficacy of 8 and 10 mm electrodes did not differ significantly. The number of RF energy applications (10 +/- 8 vs. 14 +/- 8) and ablation time (0.5 +/- 0.4 vs. 0.8 +/- 0.6 h) were less with 10 mm compared with 8 mm electrodes (p < 0.01). Of 158 patients with acute success, 42 were not evaluated at 6 months due to study exclusions. Of the 116 patients evaluated at 6 months, 112 (97%) had no AFL recurrence. Of those without AFL recurrence at 6 months, 95 and 93% were free of symptoms at 12 and 24 months, respectively. Ablation of AFL improved quality of life scores (p < 0.05) and reduced anti-arrhythmic and rate control drug use (p < 0.05). Complications occurred in six out of 169 patients (3.6%) but there were no deaths. It was concluded that ablation of AFL with 8 or 10 mm electrode catheters and a high-power RF generator was safe, effective and improved quality of life. The number and duration of RF applications was lower with 10 mm compared with 8 mm electrode catheters.

Method and apparatus for guiding ablative therapy of abnormal biological electrical excitation

NASA Technical Reports Server (NTRS)

Armoundas, Antonis A. (Inventor); Feldman, Andrew B. (Inventor); Sherman, Derin A. (Inventor); Cohen, Richard J. (Inventor)

2001-01-01

This invention involves method and apparatus for guiding ablative therapy of abnormal biological electrical excitation. In particular, it is designed for treatment of cardiac arrhythmias. In the method of this invention electrical signals are acquired from passive electrodes, and an inverse dipole method is used to identify the site of origin of an arrhytmia. The location of the tip of the ablation catheter is similarly localized from signals acquired from the passive electrodes while electrical energy is delivered to the tip of the catheter. The catheter tip is then guided to the site of origin of the arrhythmia, and ablative radio frequency energy is delivered to its tip to ablate the site.

Phrenic nerve protection via packing of gauze into the pericardial space during ablation of cristal atrial tachycardia in a child.

PubMed

Takahashi, Kazuhiro; Fuchigami, Tai; Nabeshima, Taisuke; Sashinami, Arata; Nakayashiro, Mami

2016-03-01

The success of catheter ablation of focal atrial tachycardia is limited by possible collateral damage to the phrenic nerve. Protection of the phrenic nerve is required. Here we present a case of a 9-year-old girl having a history of an unsuccessful catheter ablation of a focal atrial tachycardia near the crista terminalis (because of proximity of the phrenic nerve) who underwent a successful ablation by means of a novel technique for phrenic nerve protection: packing of gauze into the pericardial space. This method is a viable approach for patients with a failed endocardial ablation due to the proximity of the phrenic nerve.

Analysis on ultrashort-pulse laser ablation for nanoscale film of ceramics

NASA Astrophysics Data System (ADS)

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

2017-06-01

This paper uses the dual-phase-lag model to study the ablation characteristics of femtosecond laser processing for nanometer-sized ceramic films. In ultrafast process and ultrasmall size where the two lags occur, a dual-phase-lag can be applied to analyse the ablation characteristics of femtosecond laser processing for materials. In this work, the ablation rates of nanometer-sized lead zirconate titanate (PZT) ceramics are investigated using a dual-phase-lag and the model is solved by Laplace transform method. The results obtained from this work are validated by the available experimental data. The effects of material thermal properties on the ablation characteristics of femtosecond laser processing for ceramics are also discussed.

Selective material ablation by the TEA CO2 laser

NASA Astrophysics Data System (ADS)

Sumiyoshi, Tetsumi; Shiratori, Akira; Ninomiya, Yutaka; Obara, Minoru

1995-03-01

This paper reports two topics in the material processing using TEA CO2 lasers. We demonstrated selective ablation of hydrogenated amorphous silicon (a-Si:H) thin layer on a quartz substrate by the second harmonic (SH) radiation of TEA CO2 laser generated by AgGaSe2 nonlinear crystal. Si-H bonds contained in a-Si:H strongly absorb the 5 micrometers SH radiation and resulted in the selective ablation of the a-Si:H layer. The successful ablation processing of ethylenetetrafluoroethylene (ETFE) copolymer by the 9.6 micrometers fundamental wavelength TEA CO2 laser is also reported. Only ETFE thin film adhered to an aluminum substrate can be ablated by the TEA CO2 laser.

Microwave Tissue Ablation: Biophysics, Technology and Applications

PubMed Central

2010-01-01

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

Massive hematemesis after radiofrequency ablation of metastatic liver tumor with successful hemostasis achieved through transarterial embolization.

PubMed

Liu, Chien-An; Chiu, Nai-Chi; Chiou, Yi-You

2018-03-03

Hemorrhagic complications are the most common major complications that occur after radiofrequency ablation, but hematemesis as a complication after radiofrequency ablation for hepatic tumor has not been mentioned before. A hepatogastric fistula as a delayed complication is also rare. We present the case of a 77-year-old man with severe hematemesis that occurred 2 months after radiofrequency ablation of a liver metastasis of gastric cancer. A ruptured hepatic artery pseudoaneurysm and a hepatogastric fistula were confirmed through serial imaging examinations. The current case is reported in combination with 2 rare major complications after radiofrequency ablation of a liver tumor. Copyright © 2018. Published by Elsevier Inc.

Aerodynamic Evidence Pertaining to the Entry of Tektites into the Earth's Atmosphere

NASA Technical Reports Server (NTRS)

Chapman, Dean R.; Larson, Howard K.; Anderson, Lewis A.

1962-01-01

Evidence is presented which shows that the Australian and Java tektites entered the earth's atmosphere and experienced ablation by severe aerodynamic heating in hypervelocity flight. The laboratory experiments on hypervelocity ablation have reproduced ring-wave flow ridges and coiled circumferential flanges like those found on certain of these tektites. Systematic striae distortions exhibited in a thin layer beneath the front surface of australites also are reproduced in the laboratory ablation experiments, and are shown to correspond to the calculated distortions for aerodynamic ablation of a glass. About 98 percent of Australian tektites represent aerodynamically stable configurations during the ablative portion of an entry trajectory. Certain meteorites exhibit surface features similar to those on tektites.

Thermal Ablation Modeling for Silicate Materials

NASA Technical Reports Server (NTRS)

Chen, Yih-Kanq

2016-01-01

A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

Optical ablation/temperature gage (COTA)

NASA Astrophysics Data System (ADS)

Cassaing, J.; Balageas, D.

ONERA has ground and flight tested for heat-shield recession a novel technique, different from current radiation and acoustic measurement methods. It uses a combined ablation/temperature gage that views the radiation optically from a cavity embedded within the heat shield. Flight measurements, both of temperature and of passage of the ablation front, are compared with data generated by a predictive numerical code. The ablation and heat diffusion into the instrumented ablator can be simulated numerically to evaluate accurately the errors due to the presence of the gage. This technology was established in 1978 and finally adopted after ground tests in arc heater facilities. After four years of flight evaluations, it is possible to evaluate and criticize the sensor reliability.

Preparation of starch stabilized silver nanoparticles with spatial self-phase modulation properties by laser ablation technique

NASA Astrophysics Data System (ADS)

Zamiri, Reza; Azmi, B. Z.; Darroudi, Majid; Sadrolhosseini, Amir R.; Husin, M. S.; Zaidan, A. W.; Mahdi, M. A.

2011-01-01

Silver nanoparticles inside the starch solution have been successfully fabricated by laser ablation of a silver plate immersed in starch solution. The ablation has been done using a Q-switched Nd:YAG laser at 10 Hz repetition rate. The starch solution allows for the formation of silver nanoparticles with uniform particle diameters and well dispersed. The ablation was performed at different time durations to study the influence of the laser ablation time on efficiency of particle formation and sizes. The Spatial Self-phase modulation phenomena which can determine the nonlinear optical property of the samples were also investigated for starch solutions containing silver nanoparticles.

Successful Radiofrequency Catheter Ablation for Wolff-Parkinson-White Syndrome Within the Neck of a Coronary Sinus Diverticulum

PubMed Central

Jang, Sung-Won; Kim, Dong-Bin; Kwon, Bum-Jun; Cho, Eun-Joo; Shin, Woo-Seung; Kim, Ji-Hoon; Jin, Seung-Won; Oh, Yong-Seog; Lee, Man-Young; Kim, Jae-Hyung

2009-01-01

Posteroseptal accessory pathways are often associated with coronary sinus diverticula. These diverticula contain myocardial coats which serve as a bypass tract. We report a 54-year-old woman who underwent radiofrequency (RF) catheter ablation for Wolff-Parkinson-White (WPW) syndrome. The surface electrocardiography (ECG) demonstrated pre-excitation, indicating a posteroseptal accessory pathway. A catheter ablation via a transaortic approach failed to ablate the accessory pathway. Coronary sinus venography revealed the presence of a diverticulum near the ostium. An electrogram in the neck of the diverticulum showed the coronary sinus myocardial extension potential, which was successfully ablated by delivery of RF energy. PMID:19949625

Multiple target laser ablation system

DOEpatents

Mashburn, Douglas N.

1996-01-01

A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film.

Ablation of a resistant right atrial appendage tachycardia using a magnetic navigation system.

PubMed

Khan, Mohsin K; Elmouchi, Darryl

2013-01-01

The right atrial appendage is an uncommon site of origin for ectopic atrial tachycardia. Right atrial appendage tachycardia (RAAT) has been noted to be prevalent in young males and responds well to radiofrequency ablation. We report a case of RAAT resistant to multiple attempts of ablation that responded to ablation using Stereotaxis Niobe™ Magnetic Navigation System (RMN, Stereotaxis, St. Louis, MO, USA). ©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.

EF5 PET of Tumor Hypoxia: A Predictive Imaging Biomarker of Response to Stereotactic Ablative Radiotherapy (SABR) for Early Lung Cancer

DTIC Science & Technology

2014-09-01

Predictive Imaging Biomarker of Response to Stereotactic Ablative Radiotherapy ( SABR ) for Early Lung Cancer PRINCIPAL INVESTIGATOR: Billy W...CONTRACT NUMBER Response to Stereotactic Ablative Radiotherapy ( SABR ) for Early Lung Cancer 5b. GRANT NUMBER W81XWH-12-1-0236 5c...NOTES 14. ABSTRACT Purpose and scope: Stereotactic ablative radiotherapy ( SABR ) has become a new standard of care for early stage lung

Improvements In AF Ablation Outcome Will Be Based More On Technological Advancement Versus Mechanistic Understanding.

PubMed

Jiang Md, Chen-Yang; Jiang Ms, Ru-Hong

2014-01-01

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias. Catheter ablation has proven more effective than antiarrhythmic drugs in preventing clinical recurrence of AF, however long-term outcome remains unsatisfactory. Ablation strategies have evolved based on progress in mechanistic understanding, and technologies have advanced continuously. This article reviews current mechanistic concepts and technological advancements in AF treatment, and summarizes their impact on improvement of AF ablation outcome.

Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation.

PubMed

Al-Hadeethi, Y; Al-Jedani, S; Razvi, M A N; Saeed, A; Abdel-Daiem, A M; Ansari, M Shahnawaze; Babkair, Saeed S; Salah, Numan A; Al-Mujtaba, A

2016-01-01

Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased.

Dual 8-plate technique is not as effective as ablation for epiphysiodesis about the knee.

PubMed

Stewart, Daniel; Cheema, Asad; Szalay, Elizabeth A

2013-12-01

Lower extremity length inequality can be problematic in children and is often addressed surgically. Several techniques have traditionally been utilized for epiphysiodesis, the goal being physeal ablation. Recently, 8-plates, initially developed for hemiepiphysiodesis, have been extended to epiphysiodesis by placing the plates on both medial and lateral sides of the physis. No prior studies have compared 8-plates with physeal ablation techniques. Between January 2003 and August 2009, 27 patients underwent epiphysiodesis surgery using either physeal ablation or 8-plate technique. Sixteen patients had physeal ablation and 11 had dual 8-plates. A retrospective chart review sought demographic data, outcomes, and complications. Radiographs were reviewed to measure pretreatment and posttreatment limb lengths. The median improvement in limb length discrepancy was 15.5 mm in the physeal ablation group and 4 mm in the 8-plate group (P<0.001). This difference was maintained following linear regression factoring out the effect of time (10.78 mm for ablation vs. 5.62 mm for 8-plates; P=0.016). There was no statistically significant difference in complication rate between the groups (P=0.112). Our study demonstrated physeal ablation to be a significantly superior treatment compared with dual 8-plates for epiphysiodesis. Despite theoretical advantages of 8-plates to perform epiphysiodesis about the knee, this study does not recommend the use of medial and lateral 8-plates to effect epiphysiodesis. Therapeutic III.

Outcomes of Cryoballoon Ablation in High- and Low-Volume Atrial Fibrillation Ablation Centres: A Russian Pilot Survey

PubMed Central

Mikhaylov, Evgeny N.; Lebedev, Dmitry S.; Pokushalov, Evgeny A.; Davtyan, Karapet V.; Ivanitskii, Eduard A.; Nechepurenko, Anatoly A.; Kosonogov, Alexey Ya.; Kolunin, Grigory V.; Morozov, Igor A.; Termosesov, Sergey A.; Maykov, Evgeny B.; Khomutinin, Dmitry N.; Eremin, Sergey A.; Mayorov, Igor M.; Romanov, Alexander B.; Shabanov, Vitaliy V.; Shatakhtsyan, Victoria; Tsivkovskii, Viktor; Revishvili, Amiran Sh.; Shlyakhto, Evgeny V.

2015-01-01

Purpose. The results of cryoballoon ablation (CBA) procedure have been mainly derived from studies conducted in experienced atrial fibrillation (AF) ablation centres. Here, we report on CBA efficacy and complications resulting from real practice of this procedure at both high- and low-volume centres. Methods. Among 62 Russian centres performing AF ablation, 15 (24%) used CBA technology for pulmonary vein isolation. The centres were asked to provide a detailed description of all CBA procedures performed and complications, if encountered. Results. Thirteen sites completed interviews on all CBAs in their centres (>95% of CBAs in Russia). Six sites were high-volume AF ablation (>100 AF cases/year) centres, and 7 were low-volume AF ablation. There was no statistical difference in arrhythmia-free rates between high- and low-volume centres (64.6 versus 60.8% at 6 months). Major complications developed in 1.5% of patients and were equally distributed between high- and low-volume centres. Minor procedure-related events were encountered in 8% of patients and were more prevalent in high-volume centres. Total event and vascular access site event rates were higher in women than in men. Conclusions. CBA has an acceptable efficacy profile in real practice. In less experienced AF ablation centres, the major complication rate is equal to that in high-volume centres. PMID:26640789

Frozen cultured sheets of epidermal keratinocytes in reepithelialization and repair of the cornea after photorefractive keratectomy.

PubMed

Castro-Muñozledo, Federico; Ozorno-Zarate, Jorge; Naranjo-Tackman, Ramon; Kuri-Harcuch, Walid

2002-09-01

To determine whether frozen cultured sheets of human allogeneic epidermal keratinocytes (CEAK) improved wound repair after experimental corneal ablation by photorefractive keratectomy (PRK). Hospital "Luis Sanchez Bulnes" de la Asociación para Evitar la Ceguera en Mexico, I.A.P, and Department of Cell Biology, CINVESTAV-IPN, Mexico City, Mexico. Transepithelial PRK was performed in the right eye of male albino rabbits to obtain a 112 microm deep and 6.0 mm diameter ablation zone. In 17 eyes, the ablations were covered with frozen CEAK; in 11 eyes, the ablations were covered with a disposable contact lens without the cultured sheets; and in the control group (13 eyes), the ablations were not covered. Subepithelial fibrosis and reepithelialization of the ablated zone were evaluated in serial paraffin-embedded tissue sections from all wounds. Treatment with CEAK reduced fibroblast proliferation and the inflammatory response beneath the ablated zone and produced better organization of the newly formed epithelium by eliminating significant hyperplasia or discontinuities in the periodic acid Shiff-stained basement membrane. It also led to accelerated reepithelialization. The use of frozen CEAK as a biologically active wound dressing improved tissue repair at 1 month in corneas ablated by transepithelial PRK in the male albino rabbit model. Treatment with CEAK could improve the outcome of PRK in humans.

Role of near-field enhancement in plasmonic laser nanoablation using gold nanorods on a silicon substrate.

PubMed

Harrison, R K; Ben-Yakar, Adela

2010-10-11

We present experimental results for the plasmonic laser ablation of silicon with nanoscale features as small as 22 x 66 nm using single near-infrared, femtosecond laser pulses incident on gold nanorods. Near the ablation threshold, these features are photo-imprints of gold nanorod particles positioned on the surface of the silicon and have feature sizes similar to the nanorods. The single rod-shaped ablation pattern matches the enhancement patterns of the Poynting vector magnitude on the surface of silicon, implying that the ablation is a result of the plasmonic enhancement of the incident electromagnetic waves in the near-field of the particles. Interestingly, the ablation pattern is different from the two separated holes at the ends of the nanorod, as would be expected from the electric field--|E|(2) enhancement pattern. We measured the plasmonic ablation threshold fluence to be almost two orders of magnitude less than the femtosecond laser ablation threshold of silica, present in the thin native oxide layer on the surface of silicon. This value also agrees with the enhancement of the Poynting vector of a nanorod on silicon as calculated with electromagnetic simulations. We thus conclude that plasmonic ablation with plasmonic nanoparticles depends directly on the polarization and the value of the near-field enhancement of the Poynting vector and not the square of the electric field as previously suggested.

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

NASA Astrophysics Data System (ADS)

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

2009-06-01

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

Microwave ablation of the liver: a description of lesion evolution over time and an investigation of the heat sink effect.

PubMed

Bhardwaj, N; Dormer, J; Ahmad, F; Strickland, A D; Gravante, G; West, K; Dennison, A R; Lloyd, D M

2011-12-01

Microwave ablation has been successfully used to treat unresectable liver tumours for many years. However, despite its widespread use, there seems to be a relative paucity of experimental data regarding lesion evolution and the effects of any surrounding vasculature on ablation morphology. The aim of this study was to investigate the principal pathological changes in the liver following microwave ablation, in particular the heat sink effect. In addition we carefully reviewed the available literature to provide an overview of all relevant pathological studies. Microwave ablation was carried out on male rats at various distances from the hilum. Histological (H&E) and immunocytochemical (caspase 3) analyses of the lesion were performed at various time points; 0, 4, 24, 48  hours, 2 weeks and 1 month. A literature review was carried out using Medline, Embase and the Cochrane database to identify all relevant histological studies. The lesion underwent complete coagulative necrosis and was extremely regular at the ablation edge with no evidence of any influence from surrounding blood vessels at all time points. H&E and caspase 3 results were consistent and microwave caused little collateral damage outside the intended ablation zone. This study suggests that microwave ablation is extremely concise and is minimally affected by the heat sink effect. Comparative investigations with other treatment modalities are required.

Non-ablative hyperthermic mesenchymal regeneration: a proposed mechanism of action based on the Vivev model

NASA Astrophysics Data System (ADS)

Vos, Jeffrey A.; Livengood, Ryan H.; Jessop, Morris; Coad, James E.

2011-03-01

Novel non-ablative hyperthermic medical devices are currently being developed, in association with cryogen surface cooling, to rejuvenate tissues without collagen scarring. These devices have been designed to remodel skin, manage urinary stress incontinence, and more recently, treat vaginal laxity. In contrast to the thermal injury and reparative healing associated with higher energy ablation systems, these lower energy non-ablative systems are designed to subtly modify the collagen, stimulate the fibroblasts, and maintain a functional tissue architecture that subsequently promotes tissue rejuvenation and restoration. While these devices have primarily relied on clinical outcome questionnaires and satisfaction surveys to establish efficacy, a physiologic explanation for the induced tissue changes and tightening has not been well documented. Recent histology studies, using the Viveve ovine vaginal treatment model, have identified changes that propose both a mechanism of action and a tissue remodeling timeline for such non-ablative hyperthermic devices. The Viveve model results are consistent with subtle connective tissue changes leading to fibroblast stimulation and subsequent collagen replacement and augmentation. Unlike tissue ablation devices that cause thermal necrosis, these non-ablative devices renew the targeted tissue without dense collagenous scarring over a period of 3 or more months. The spectrum of histologic findings, as illustrated in the Viveve ovine vaginal model, further support the previously documented safety and efficacy profiles for low-dose non-ablative hyperthermic devices that rejuvenate and tighten submucosal tissues.

Dynamic behavior of photoablation products of corneal tissue in the mid-IR: a study with FELIX

NASA Astrophysics Data System (ADS)

Auerhammer, J. M.; Walker, R.; van der Meer, A. F. G.; Jean, B.

The properties of pulsed IR-laser ablation of biological soft tissue (porcine cornea) were studied in vitro systematically and quantitatively with a free-electron laser in the wavelength range 6<=λ<=20 μm at fluences ranging from 3.1 to 9.4 J/cm2. Dynamic parameters such as the extension of the ablation cloud, the initial velocity and momentum of the ablated particles as well as the ablation threshold, the ablated mass, and the particle size were investigated. The ablation plume was made visible with a stroboscopic technique. For a fluence of 3.1 J/cm2 the average initial velocity of the ejected particles was deduced from the extension of the plume to range from 120-400 m/s. Measurements of the recoil momentum using a sensitive pendulum led to values between 0.5 and 2.0 mmg/s. All measured properties were related to the spectroscopically determined absorption coefficient of cornea αcornea. Where absorption due to proteins is high (at λ=6.2 and 6.5 μm), ablated mass, velocity and recoil momentum behave according to αcornea. For the first time, variations of the ablation plume from pulse to pulse were observed. Those, as well as the particle size, not only depend on the absorption coefficient, but also on the predominant absorber.

Ablative Fractional 10 600 nm Carbon Dioxide Laser Versus Non-ablative Fractional 1540 nm Erbium-Glass Laser in Egyptian Post-acne Scar patients.

PubMed

Elsaie, Mohamed L; Ibrahim, Shady M; Saudi, Wael

2018-01-01

Introduction: Non-ablative fractional erbium-doped glass 1540 nm and fractional ablative 10600 nm carbon dioxide lasers are regarded as effective modalities for treating acne atrophic scars. In this study, we aimed to compare the effectiveness of fractional CO 2 laser and fractional nonablative 1540 nm erbium doped glass laser in treating post acne atrophic scars in Egyptian patients. Methods: Fifty-eight patients complaining of moderate and severe acne atrophic scars were randomly divided into 2 groups of 29 patients each. Both groups were subjected to 4 treatment sessions with 3 weeks interval and were followed up for 3 months. In group A, enrolled patient sreceived C2 laser, while in group B, patients were treated with 1540 nm erbium glass fractional laser. Results: Clinical assessment revealed that the mean grades of progress and improvement were higher with fractional 10600 nm CO2 laser but with non-significant difference between both treatments ( P = 0.1). The overall patients' satisfaction with both lasers were not significantly different ( P = 0.44). Conclusion: Both fractional ablative CO2 and fractional non-ablative erbium glass lasers are good modalities for treating acne scars with a high efficacy and safety profile and good patient satisfaction. The fractional ablative laser showed higher efficacy while non-ablative laser offered less pain and shorter downtime.

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

PubMed

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

PubMed

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

2017-10-01

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

Impact of spatial variation in snow water equivalent and snow ablation on spring snowcover depletion over an alpine ridge

NASA Astrophysics Data System (ADS)

Schirmer, Michael; Harder, Phillip; Pomeroy, John

2016-04-01

The spatial and temporal dynamics of mountain snowmelt are controlled by the spatial distribution of snow accumulation and redistribution and the pattern of melt energy applied to this snowcover. In order to better quantify the spatial variations of accumulation and ablation, Structure-from-Motion techniques were applied to sequential aerial photographs of an alpine ridge in the Canadian Rocky Mountains taken from an Unmanned Aerial Vehicle (UAV). Seven spatial maps of snow depth and changes to depth during late melt (May-July) were generated at very high resolutions covering an area of 800 x 600 m. The accuracy was assessed with over 100 GPS measurements and RMSE were found to be less than 10 cm. Low resolution manual measurements of density permitted calculation of snow water equivalent (SWE) and change in SWE (ablation rate). The results indicate a highly variable initial SWE distribution, which was five times more variable than the spatial variation in ablation rate. Spatial variation in ablation rate was still substantial, with a factor of two difference between north and south aspects and small scale variations due to local dust deposition. However, the impact of spatial variations in ablation rate on the snowcover depletion curve could not be discerned. The reason for this is that only a weak spatial correlation developed between SWE and ablation rate. These findings suggest that despite substantial variations in ablation rate, snowcover depletion curve calculations should emphasize the spatial variation of initial SWE rather than the variation in ablation rate. While there is scientific evidence from other field studies that support this, there are also studies that suggest that spatial variations in ablation rate can influence snowcover depletion curves in complex terrain, particularly in early melt. The development of UAV photogrammetry has provided an opportunity for further detailed measurement of ablation rates, SWE and snowcover depletion over complex terrain and UAV field studies are recommended to clarify the relative importance of SWE and melt variability on snowcover depletion in various environmental conditions.

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

PubMed Central

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

2016-01-01

Background Radiofrequency ablation (RFA) and microwave ablation (MWA) are the most frequently used thermal ablation methods for the treatment of liver cancer. Liver abscess is a common and severe complication of thermal ablation treatment. Objectives The objective of this study was to determine the incidence and risk factors of liver abscess formation after thermal ablation of liver cancer. Materials and Methods The clinical data of 423 patients who underwent 691 thermal ablation procedures for liver cancer were collected in order to retrospectively analyze the basic characteristics, incidence, and risk factors associated with liver abscess formation. Patients with multiple risk factors for liver abscess formation were enrolled in a risk factor group, and patients with no risk factors were enrolled in a control group. The chi-square test and multiple logistic regression analysis were used to analyze the relationship between the occurrence of liver abscesses and potential risk factors. Results Two hundred and eight patients underwent 385 RFA procedures, and 185 patients underwent 306 MWA procedures. The total incidence of liver abscesses was 1.7%, while the rates in the RFA group (1.8%) and MWA groups (1.6%) were similar (P > 0.05). The rates of liver abscesses in patients who had child-pugh class B and class C cirrhosis (P = 0.0486), biliary tract disease (P = 0.0305), diabetes mellitus (P = 0.0344), and porta hepatis tumors (P = 0.0123) were 4.0%, 6.7%, 6.5%, and 13.0%, respectively. There was a statistically significant difference between these four groups and the control group (all P < 0.05). The incidence of liver abscesses in the combined ablation and percutaneous ethanol injection (PEI) group (P = 0.0026) was significantly lower than that of the ablation group (P < 0.05). Conclusions The incidence of liver abscesses after liver cancer thermal ablation is low. Child-Pugh Class B and Class C cirrhosis, biliary tract disease, diabetes mellitus, and porta hepatis tumors are four significant risk factors. Combined ablation and PEI reduces the rate of liver abscesses. PMID:27642345

The Influence of Ablation on Radiative Heating for Earth Entry

NASA Technical Reports Server (NTRS)

Johnston, Christopher O.; Gnoffo, Peter A.; Sutton, Kenneth

2008-01-01

Using the coupled ablation and radiation capability recently included in the LAURA flowfield solver, this paper investigates the influence of ablation on the shock-layer radiative heating for Earth entry. The extension of the HARA radiation model, which provides the radiation predictions in LAURA, to treat a gas consisting of the elements C, H, O, and N is discussed. It is shown that the absorption coefficient of air is increased with the introduction of the C and H elements. A simplified shock layer model is studied to show the impact of temperature, as well as the abundance of C and H, on the net absorption or emission from an ablation contaminated boundary layer. It is found that the ablation species reduce the radiative flux in the vacuum ultraviolet, through increased absorption, for all temperatures. However, in the infrared region of the spectrum, the ablation species increase the radiative flux, through strong emission, for temperatures above 3,000 K. Thus, depending on the temperature and abundance of ablation species, the contaminated boundary layer may either provide a net increase or decrease in the radiative flux reaching the wall. To assess the validity of the coupled ablation and radiation LAURA analysis, a previously analyzed Mars-return case (15.24 km/s), which contains significant ablation and radiation coupling, is studied. Exceptional agreement with previous viscous shock-layer results is obtained. A 40% decrease in the radiative flux is predicted for ablation rates equal to 20% of the free-stream mass flux. The Apollo 4 peak-heating case (10.24 km/s) is also studied. For ablation rates up to 3.4% of the free-stream mass flux, the radiative heating is reduced by up to 19%, while the convective heating is reduced by up to 87%. Good agreement with the Apollo 4 radiometer data is obtained by considering absorption in the radiometer cavity. For both the Mars return and the Apollo 4 cases, coupled radiation alone is found to reduce the radiative heating by 30 60% and the convective heating by less than 5%.

Sprayable lightweight ablative coating

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

A novel integration of spectral-domain optical-coherence-tomography and laser-ablation system for precision treatment.

PubMed

Fan, Yingwei; Zhang, Boyu; Chang, Wei; Zhang, Xinran; Liao, Hongen

2018-03-01

Complete resection of diseased lesions reduces the recurrence of cancer, making it critical for surgical treatment. However, precisely resecting residual tumors is a challenge during operation. A novel integrated spectral-domain optical-coherence-tomography (SD-OCT) and laser-ablation therapy system for soft-biological-tissue resection is proposed. This is a prototype optical integrated diagnosis and therapeutic system as well as an optical theranostics system. We develop an optical theranostics system, which integrates SD-OCT, a laser-ablation unit, and an automatic scanning platform. The SD-OCT image of biological tissue provides an intuitive and clear view for intraoperative diagnosis and monitoring in real time. The effect of laser ablation is analyzed using a quantitative mathematical model. The automatic endoscopic scanning platform combines an endoscopic probe and an SD-OCT sample arm to provide optical theranostic scanning motion. An optical fiber and a charge-coupled device camera are integrated into the endoscopic probe, allowing detection and coupling of the OCT-aiming beam and laser spots. The integrated diagnostic and therapeutic system combines SD-OCT imaging and laser-ablation modules with an automatic scanning platform. OCT imaging, laser-ablation treatment, and the integration and control of diagnostic and therapeutic procedures were evaluated by performing phantom experiments. Furthermore, SD-OCT-guided laser ablation provided precision laser ablation and resection for the malignant lesions in soft-biological-tissue-lesion surgery. The results demonstrated that the appropriate laser-radiation power and duration time were 10 W and 10 s, respectively. In the laser-ablation evaluation experiment, the error reached approximately 0.1 mm. Another validation experiment was performed to obtain OCT images of the pre- and post-ablated craters of ex vivo porcine brainstem. We propose an optical integrated diagnosis and therapeutic system. The primary experimental results show the high efficiency and feasibility of our theranostics system, which is promising for realizing accurate resection of tumors in vivo and in situ in the future.

Laser dissection sampling modes for direct mass spectral analysis [using a hybrid optical microscopy/laser ablation liquid vortex capture/electrospray ionization system

DOE PAGES

Cahill, John F.; Kertesz, Vilmos; Van Berkel, Gary J.

2016-02-01

Here, laser microdissection coupled directly with mass spectrometry provides the capability of on-line analysis of substrates with high spatial resolution, high collection efficiency, and freedom on shape and size of the sampling area. Establishing the merits and capabilities of the different sampling modes that the system provides is necessary in order to select the best sampling mode for characterizing analytically challenging samples. The capabilities of laser ablation spot sampling, laser ablation raster sampling, and laser 'cut and drop' sampling modes of a hybrid optical microscopy/laser ablation liquid vortex capture electrospray ionization mass spectrometry system were compared for the analysis ofmore » single cells and tissue. Single Chlamydomonas reinhardtii cells were monitored for their monogalactosyldiacylglycerol (MGDG) and diacylglyceryltrimethylhomo-Ser (DGTS) lipid content using the laser spot sampling mode, which was capable of ablating individual cells (4-15 m) even when agglomerated together. Turbid Allium Cepa cells (150 m) having unique shapes difficult to precisely measure using the other sampling modes could be ablated in their entirety using laser raster sampling. Intact microdissections of specific regions of a cocaine-dosed mouse brain tissue were compared using laser 'cut and drop' sampling. Since in laser 'cut and drop' sampling whole and otherwise unmodified sections are captured into the probe, 100% collection efficiencies were achieved. Laser ablation spot sampling has the highest spatial resolution of any sampling mode, while laser ablation raster sampling has the highest sampling area adaptability of the sampling modes. In conclusion, laser ablation spot sampling has the highest spatial resolution of any sampling mode, useful in this case for the analysis of single cells. Laser ablation raster sampling was best for sampling regions with unique shapes that are difficult to measure using other sampling modes. Laser 'cut and drop' sampling can be used for cases where the highest sensitivity is needed, for example, monitoring drugs present in trace amounts in tissue.« less

Screening Magnetic Resonance Imaging-Based Prediction Model for Assessing Immediate Therapeutic Response to Magnetic Resonance Imaging-Guided High-Intensity Focused Ultrasound Ablation of Uterine Fibroids.

PubMed

Kim, Young-sun; Lim, Hyo Keun; Park, Min Jung; Rhim, Hyunchul; Jung, Sin-Ho; Sohn, Insuk; Kim, Tae-Joong; Keserci, Bilgin

2016-01-01

The aim of this study was to fit and validate screening magnetic resonance imaging (MRI)-based prediction models for assessing immediate therapeutic responses of uterine fibroids to MRI-guided high-intensity focused ultrasound (MR-HIFU) ablation. Informed consent from all subjects was obtained for our institutional review board-approved study. A total of 240 symptomatic uterine fibroids (mean diameter, 6.9 cm) in 152 women (mean age, 43.3 years) treated with MR-HIFU ablation were retrospectively analyzed (160 fibroids for training, 80 fibroids for validation). Screening MRI parameters (subcutaneous fat thickness [mm], x1; relative peak enhancement [%] in semiquantitative perfusion MRI, x2; T2 signal intensity ratio of fibroid to skeletal muscle, x3) were used to fit prediction models with regard to ablation efficiency (nonperfused volume/treatment cell volume, y1) and ablation quality (grade 1-5, poor to excellent, y2), respectively, using the generalized estimating equation method. Cutoff values for achievement of treatment intent (efficiency >1.0; quality grade 4/5) were determined based on receiver operating characteristic curve analysis. Prediction performances were validated by calculating positive and negative predictive values. Generalized estimating equation analyses yielded models of y1 = 2.2637 - 0.0415x1 - 0.0011x2 - 0.0772x3 and y2 = 6.8148 - 0.1070x1 - 0.0050x2 - 0.2163x3. Cutoff values were 1.312 for ablation efficiency (area under the curve, 0.7236; sensitivity, 0.6882; specificity, 0.6866) and 4.019 for ablation quality (0.8794; 0.7156; 0.9020). Positive and negative predictive values were 0.917 and 0.500 for ablation efficiency and 0.978 and 0.600 for ablation quality, respectively. Screening MRI-based prediction models for assessing immediate therapeutic responses of uterine fibroids to MR-HIFU ablation were fitted and validated, which may reduce the risk of unsuccessful treatment.