Ablation Parameters Research Articles

Study of Laser Ablative Destruction of Composites with Nanoscale Coatings of Hafnium and Zirconium Dioxides

An experimental study of laser ablation on the samples that comprise nanofilms of hafnium and zirconium dioxides on the surface of glass and silicon, and obtaining parameters of pulsed laser ablation in this work, provide new data describing the ablation mechanism. The samples were exposed to pulsed radiation from an Nd3+:YAG laser in order to measure the threshold energy density of laser ablation and determine the parameters used in the simulation of statistical distributions. Based on these data, the dependences of the parameters of laser ablation on the optical and thermophysical characteristics of these oxides were obtained.

Kinetic simulations of piston-driven collisionless shock formation in magnetized laboratory plasmas

Laboratory laser experiments offer a novel approach to studying magnetized collisionless shocks, and a common method in recent experiments is to drive shocks using a laser-ablated piston plasma. However, current experimental capabilities are still limited to spatiotemporal scales on the order of shock formation, making it challenging to distinguish piston and shock dynamics. We present quasi-1D particle-in-cell simulations of piston-driven, magnetized collisionless shock formation using the code PSC, which includes a model of laser-driven plasmas that can be well-matched to experimental conditions. The simulations cover a range of upstream and ablation parameters and yield several robust signatures of shock formation, which can provide a reference for experimental results.

The Influence of Laser Ablation Parameters on the Holes Structure of Laser Manufactured Graphene Paper Microsieves

The graphene paper microsieves can be applied in the filtration of biological fluids or separation of solid particles from exploitation fluids. To produce graphene paper microsieves for specific applications, good control over fabrication should be achieved. In this study, a laser ablation method using a picosecond laser was applied to fabricate graphene paper microsieves. Holes in the microsieves were drilled using pulsed laser radiation with a pulse energy from 5 to 100 µJ, a duration of 60 ps, a wavelength of 355 nm, and a repetition rate of 1 kHz. The impact method was applied using 10 to 100 pulses to drill one hole. To produce holes of a proper diameter which could separate biological particles of a certain size (≥10 µm), optimum parameters of graphene paper laser ablation were defined using the MATLAB software taking into account laser pulse energy, repetition rate, and a desired hole diameter. A series of structural tests were carried out to determine the quality of an edge and a hole shape. Experimental results and Laguerre–Gauss calculations in MATLAB were then compared to perform the analysis of the distribution of diffraction fringes. Optimum experimental parameters were determined for which good susceptibility of the graphene paper to laser processing was observed.

Investigation the effect of laser ablation parameters in a liquid in order to reduce the pulse energy during laser shock peening

The features of laser shock peening technology was studied in relation to the physical processes occurring during and after laser treatment. The effect of laser parameters on the results of the process was investigated. It was shown that the reduce of the diameter of the laser spot while maintaining the intensity leads to a decrease in the effect of LSP. This phenomenon was studied from the point of view of the features of plastic deformation at various sizes of the treatment zone using the standard model for the LSP process. Besides the features of the development of a plasma plume during laser ablation in a liquid are considered. It was shown that the liquid determines the geometry of the plume evolution and the shock wave caused by it. The process parameters used and the results obtained are important for the development of low-energy LSP technology.

Simultaneous optimization of nanosecond laser ablation and frictional characteristics of tantalum carbide coated graphite substrates

Tantalum carbide (TaC) is a potential candidate for high temperature applications such as rocket nozzles and thrust petals. Laser surface modification of such transition metal carbides imposes challenges in the selection of laser parameters to achieve controlled microstructure, reduction in porosity, surface roughness and higher wear resistance. The present research focuses on investigating the effects of laser ablation parameters such as pulse energy, scanning speed, line spacing and their interactions on surface roughness and CoF of tantalum carbide coated graphite substrates. Regression models were developed to establish a correlation between surface roughness and coefficient of friction along with laser parameters. The contribution of pulse energy was found to be more significant on CoF, whereas line spacing had a greater influence on the surface roughness of the TaC coatings. The optimal condition to obtain minimum surface roughness and CoF was achieved at a higher pulse energy of 250 μJ, lower scanning speed of 100 mm/s and lower line spacing of 10 μm.

Cryoballoon ablation dosing: From the bench to the bedside and back

To date, multiple modes of research have been leveraged to study the optimal cryoballoon ablation parameters to safely, effectively, and efficiently isolate the pulmonary veins for the treatment of atrial fibrillation. Basic scientific investigation, preclinical studies, clinical observations, trials, and, more recently, computational modeling have helped to generate and test new hypotheses for the advancement of cryoballoon treatment in patients with atrial fibrillation. In this review, we examine the data and evidence that have contributed to the development of patient-tailored dosing strategies that are currently used for pulmonary vein isolation by using the Arctic Front series of cryoballoon ablation catheters.

Imaging and Image-Guided Thermal Ablation for Oligometastatic Colorectal Cancer Liver Disease.

Colorectal cancer affects more than 1 million people worldwide, and half of this population develops liver metastases. Image-guided thermal ablation is an acceptable local therapy for the management of oligometastatic colorectal cancer liver disease, in patients who are noneligible for surgery, or present with recurrence after hepatectomy. Continuous technological evolutions, understanding of tumor variability through disease biology and genetics, and optimization of ablation parameters with ablation margin assessment have allowed patients with resectable small-volume disease to be treated by thermal ablation with curative intent. The growing role of imaging and image guidance in thermal ablation for patient selection, procedure planning, tumor targeting, and assessment of technical success is discussed in this article.

3:45 PM Abstract No. 37 Microwave ablation zones for the treatment of hepatocellular carcinoma compared with ex vivo bovine liver data

The purpose of this study was to compare the ex vivo bovine liver ablation zone volume data provided by the manufacturer with measured ablation zone volumes on post procedure CT scans following hepatocellular carcinoma ablation with the Solero Microwave Tissue Ablation System (AngioDynamics). All CT-guided microwave ablations of the liver for hepatocellular carcinoma from September 1, 2017, through October 1, 2018, using the Solero system (AngioDynamics) were reviewed. All patients with previous embolization to the ablated segment of the liver, overlapping ablations, ablations that abutted prior ablation zones, and ablation energies or times without ex vivo correlates were excluded. The ablation zone volumes and measurements were made from a multiphase abdominal CT, including a late arterial phase, within the same day following the procedure. The ex vivo volumes were calculated based on an ellipsoid volume formula with the diameters provided by AngioDynamics in the ablation measurement guide. The data was analyzed using a T-test. 43 patients with 51 ablations were included in the analysis. The ablation zone volumes were an average of 54% of the calculated ex vivo volume. The most commonly performed ablation parameters were 100W for 4 min, 100W for 6 min, and 140W for 6 min with 22, 8, and 6 ablations, respectively. The measured ablation volumes were significantly smaller than that predicted by the ex vivo measurements in all three groups (P <0.05). In evaluating 51 liver ablations without prior treatments with embolization or overlapping ablation zones, the ablation zones on immediate post procedure CT scans were significantly smaller by volume than that predicted by ex vivo bovine liver measurements provided for the corresponding wattage and time.Tabled 1100W, 4 min100W, 6 min140W, 6 minNumber of ablations2286Average volume (cc)13.123.625.2Median volume (cc)13.122.421.3Predicted volume (cc)28.245.354.7Average difference (%)544854 Open table in a new tab

Laser ablation split-stream analysis of the Sm-Nd and U-Pb isotope compositions of monazite, titanite, and apatite – Improvements, potential reference materials, and application to the Archean Saglek Block gneisses

Continued improvements in both ICPMS (inductively-coupled plasma mass spectrometry) and laser ablation technologies are fueling advancements in accessory mineral investigations and their related isotope systems of interest, and are now being applied to a wide range of geological applications. In this contribution we present an updated methodology for laser ablation split-stream (LASS) analysis of the light rare earth element (LREE) enriched minerals monazite, titanite, and apatite for simultaneous analysis of the U-Th-Pb age (or trace element content) and the Sm-Nd isotope system. The data were collected with the current generation of high-sensitivity ICPMS and laser systems (ThermoFinnigan NeptunePlus MC-ICPMS and Element XR SF-ICPMS- coupled to a RESOlution 193 nm ArF excimer laser system). The increased sensitivity of these ICPMS instruments allows for improved spatial resolution and the ability to target minerals which previously contained insufficient concentrations of elements of interest (e.g., Sm-Nd in apatite), making their analysis difficult, if not impossible, using less sensitive instruments. Furthermore, the higher sensitivity allows less aggressive ablation parameters that facilitate thin section sampling and reduces inter-element and isotopic fractionation.To assess and improve the accuracy, precision, and efficiency of the technique, three new potential LASS reference materials (RMs) are evaluated for dual U-Pb and Sm-Nd analysis (Tory Hill apatite, Tory Hill titanite, and Steenskralkamp monazite). The homogeneity of these materials was first assessed using reconnaissance laser ablation analyses, with final characterization of U-Pb age and Sm-Nd isotope composition using isotope-dilution thermal ionization mass spectrometry (ID-TIMS). The precision and accuracy of the LASS method is explored using secondary mineral reference materials of known age and Sm-Nd isotope composition. The utility of the technique is evaluated with a case study of monazite and apatite from the Eoarchean Uivak Gneiss complex of Labrador, Canada. Finally, we suggest that there is a wide variety of geological applications for this methodology, such as multi-mineral detrital provenance, crustal growth, and petrogenic studies.

Contact Force-Guided Ablation Reduced Poor Contact Segments and Improved Acute Reconnection in Patients with Atrial Fibrillation.

There is a paucity of information regarding whether contact force (CF)-guided ablation improves the outcomes of pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF) by achieving more optimal contact. We sought to assess whether real time CF-guided ablation has an impact on ablation parameters and acute pulmonary vein reconnection (PVR). Left or right PVs were randomized to either CF-guided or blinded groups, and the order of CF blindness: CF-guided left PV/CF-blinded right PV, CF-blinded left PV/CF-guided right PV, CF-guided right PV/CF-blinded left PV, and CF-blinded right PV/CF-guided left PV groups. We compared CF parameters and acute PVR between segments ablated by CF-guided and CF-blinded strategies. Sixty patients with drug refractory symptomatic AF were included (paroxysmal AF 73%). CF-guided segments did not show significant differences in CF parameters compared to CF-blinded segments. However, CF-guided segments showed fewer segments with mean CF value <5 g than CF-blinded segments (4.3% vs. 12.4%, p<0.001). Forty-two patients showed acute PVR in 92 segments (8.5%). CF-guided PV segments showed lower acute PVR rate than CF-blinded segments (5.9% vs. 11.1%, p=0.011). CF-guided ablation could reduce acute PVR after PVI by decreasing the number of segments with poor contact rather than increasing the mean CF during ablation. Better contact guided by CF information might help in improving the results of PVI. Further investigation will be needed to identify the association between the difference in acute reconnection and the long-term outcomes.

3D visualization ablation planning system assisted microwave ablation for hepatocellular carcinoma (Diameter >3): a precise clinical application

BackgroundThe aim of this retrospective study was to compare the feasibility and efficiency of ultrasound-guided percutaneous microwave ablation (US-PMWA) assisted by three-dimensional visualization ablation planning system (3DVAPS) and conventional 2D planning for hepatocellular carcinoma (HCC) (diameter > 3 cm).MethodsOne hundred thirty patients with 223 HCC nodules (5.0 ± 1.5 cm in diameter, [3.0–10.0 cm]) who met the eligibility criteria divided into 3D and 2D planning group were reviewed from April 2015 to August 2018. Ablation parameters and oncological outcomes were compared, including overall survival (OS), recurrence-free survival (RFS), and local tumor progression (LTP). Multivariate analysis was performed on clinicopathological variables to identify the risk factors for OS and LTP.ResultsThe median follow-up period was 21 months (range 3–44). Insertion number (5.4 ± 1.2 VS. 4.5 ± 0.9, P = 0.034), ablation time (1249.2 ± 654.2 s VS. 1082.4 ± 584.7 s, P = 0.048), ablation energy (57,000 ± 11,892 J VS. 42,600 ± 10,271 J, P = 0.038) and success rate of first ablation (95.0% VS. 85.7%, P = 0.033) were higher in the 3D planning group compared with those in 2D planning group. There was no statistical difference in OS, and RFS between the two groups (P = 0.995, P = 0.845). LTP rate of 3D planning group was less than that of 2D planning group (16.5% VS 41.2%, P = 0.003). Multivariate analysis showed tumor maximal diameters (P < 0.001), tumor number (P = 0.003) and preoperative TACE (P < 0.001) were predictors for OS and sessions (P = 0.024), a-fetoprotein level (P = 0.004), and preoperative planning (P = 0.002) were predictors for LTP, respectively.Conclusions3DVAPS improves precision of US guided ablation resulting in lower LTP and higher 5 mm-AM for patients with HCC lesions larger than 3 cm in diameter.

Ablation Approaches and Imaging Modalities to Lower Risk of Atrioesophageal Injury During Catheter Ablation for Atrial Fibrillation

Atrioesophageal fistula (AEF) is a rare yet catastrophic complication of atrial fibrillation (AF) ablation. Limited data exists on measures to prevent AEF. This review focuses on AF ablation approaches, esophageal protective strategies, and imaging modalities that can be utilized to reduce the risk of AEF. AEF has been reported to occur in less than 0.1% of AF ablation cases. Left untreated, it is associated with 100% mortality. Diagnosing AEF requires a high index of suspicion as symptoms are usually nonspecific. Several AF ablation techniques might reduce the risk of esophageal thermal injury (ETI): high-power short-duration radiofrequency ablation, implementation of time-to-isolation ablation strategy with cryoablation, and electroporation. Various esophageal protective approaches have been investigated. Although luminal esophageal temperature monitoring is widely used, data on its efficacy is conflicting. Esophageal cooling and esophageal deviation strategies have been shown to be effective in reducing the risk of ETI. Late gadolinium enhancement magnetic resonance imaging (LGE-MRI) is a noninvasive imaging modality that seems to have high sensitivity for detecting and quantifying the degree of ETI. Variable approaches have been reported to reduce the risk of esophageal injury. These approaches focus mainly on modulating ablation parameters and esophageal luminal temperature. Imaging modalities such as LGE-MRI can potentially identify early signs of ETI. Electroporation is a promising ablation technique that exhibits high tissue selectivity and can potentially reduce risk of esophageal injury.

Ablation and functionalization of flexographic printing forms using femtosecond lasers for additively manufactured polymer-optical waveguides

An efficient and low-cost approach to manufacture Opto-Mechatronic Interconnect Devices will be obligatory to handle the strongly increasing amount of data. The presented approach is based on a flexographic printing process. To adjust the transferred material the printing form is functionalized by means of laser-induced structures using an ultrashort-pulsed laser. The long-term goal is to adjust the printing result through microstructures in the printing form in order to create spatially resolved material transfer.In this work, first the ablation parameters are investigated at different repetition rates using a femtosecond laser. Further, a line structure is inserted in the material transferring areas of the printing form, which is consequently widened. Its influence on the printing result is presented.

Feature-Aware Trilateral Filter With Energy Minimization for 3D Mesh Denoising

Sharp edges and corners are crucial features for high-quality and fine-detailed 3D meshes, which we tend to treat as noises in previous tasks of mesh denoising mistakenly. A challenge arises on how to handle both surfaces and features simultaneously in 3D mesh denoising. Classical works mainly focused on surfaces, whereas features also reasonably need proper processes. In this paper, we propose a feature-aware trilateral filter under the framework of energy minimization for 3D mesh denoising and address the above challenge. Concretely, we treat the challenge as an energy minimization model, where the data and smooth terms are both carefully designed. Apart from this, we introduce a feature-aware trilateral filter for high-quality mesh guidance to the model. In this filter, features are detected and distinguished from surfaces for consequent guidance. With the help of the model and filter, more priors are involved, and we can make global optimization for better denoising performance. We perform experiments on both synthetic and scanned meshes, where both subjective and objective evaluations are displayed to show the superior performance of our method to state-of-the-art methods. Furthermore, two experiments, including ablation tests and parameter sensitivities tests, are conducted to show the robustness and efficiency of our method thoroughly. All these results demonstrate that our method is suitable for robust and efficient performance in future mesh-oriented applications.

Surface ablation variability of mountain glaciers of West Spitsbergen

Measurements of surface ablation in 2016–2018 on the neighboring glaciers Aldegondabreen, Austre and Vestre Grønfjordbreen (West Spitsbergen) revealed significant differences in its magnitude both within the same altitude zones for one year, and on an interannual scale. Comparison of the region’s common variations in climatic conditions (air temperature, rainfall) and ablation data showed a significant contribution of the following additional factors of melting: aspect, size, altitude range, surface slope, the rocky bordering of glaciers. The maximum ablation were measured on the Aldegondabreen (with the smallest area and altitude range), which has a northeastern aspect; the average value over three years of observations was 1947 mm w.e. Austre Grønfjordbreen and Vestre Grønfjordbreen had in 2016–2018 average ablation values 1512 and 1385 mm w.e., respectively. The largest Vestre Grønfjordbreen has the lowest values of average ablation also because it lies higher then neighboring glaciers. Interannual variations of mean ablation in the same altitudinal zones show: the minimum scatter of values for the Aldegondabreen (130–370 mm w.e.); higher scatter of values for the Austre Grønfjordbreen (200–450 mm w.e.); the maximum scatter of values for the Vestre Grønfjordbreen (from 400–600 mm w.e. in most altitude zones to 1000 mm w.e. at altitudes of 250–350 m). Due to the influence of additional factors, the maximum average ablation was observed on the Aldegondabreen in 2016, on the Vestre Grønfjordbreen in 2017, and on the Austre Grønfjordbreen in 2017 and 2018. The results of the study indicate the need to take into account the contribution of these factors to the ablation parameters of the region’s glaciers in model calculations, as well as the relevance of a detailed study of the distribution of solar radiation on glaciers.

Esophageal Thermal Injury FollowingCryoballoon Ablation forAtrialFibrillation.

This study evaluated the rate and predictors of endoscopically detected esophageal thermal lesions (EDEL) in patients who underwent cryoballoon atrial fibrillation (AF) ablation (CBA). EDEL is a known complication of catheter ablation for AF and is the inciting factor for atrial esophageal fistula formation. An observational study was conducted of patients with AF presenting for CBA. Pre-procedural magnetic resonance imaging was used to retrospectively evaluate the distance between the atrial endocardium and the esophageal lumen (AED). Intraprocedural esophageal luminal temperature and balloon temperatures were recorded. All patients underwent upper endoscopy (EGD) 24h post-ablation. Clinical, anatomical, and ablation parameters were analyzed using logistic regression for association with thermal injury. A total of 95 patients (37% women; 71% paroxysmal AF) were included in the study. Esophageal thermal injury was detected on EGD in 21 patients (22%). EDEL was mostly mild (20 of 21 patients) and severe in only 1 of 21 patients. Univariate logistic regression identified gastroesophageal reflux disease to be associated with increased risk of thermal injury (odds ratio [OR]: 3.2; 95% confidence interval [CI]: 1.00 to 10.46; p=0.04), whereas a wider AED was protective (OR: 0.16; 95%CI: 0.05 to 0.515; p=0.002). Esophageal wall thickness was also protective (OR: 0.04; 95%CI: 0.002 to 0.864; p=0.04). In multivariate analysis, only AED (OR: 0.22; 95%CI: 0.06 to 0.77; p=0.018) and obesity (OR: 4.63; 95%CI: 1.13 to 18.97; p=0.033) were associated with EDEL. Esophageal luminal temperature, number, and duration of cryoballoon applications and balloon temperature were not predictors of EDEL. EDEL following CBA occurred in 22% of patients and was mostly mild. Obesity and atrioesophageal distance were independently associated with increased risk.

Planar and ridge waveguides formed by proton implantation and femtosecond laser ablation in fused silica

This work reports on the fabrication of optical planar and ridge waveguides in the fused silica glass by combining the proton implantation and the femtosecond laser ablation. The conditions for the ion implantation are an energy of 400 keV and a fluence of 8 × 1016 ions/cm2. The experimental parameters of the femtosecond laser ablation are a pulse energy of 5.0 mW and a scanning speed of 200 μm/s. The nuclear energy loss of the implanted hydrogen ions was derived by using the SRIM 2013 code. The optical properties of fabricated optical waveguides were studied by using the prism coupling method (at 632.8 nm) and the reflectivity calculation method. The light intensity distribution of the ridge waveguide at 976 nm was experimentally measured to validate its effect on two dimensions confinement.

Influence of Aluminum Laser Ablation on Interfacial Thermal Transfer and Joint Quality of Laser Welded Aluminum–Polyamide Assemblies

Laser assisted metal–polymer joining (LAMP) is a novel assembly process for the development of hybrid lightweight products with customized properties. It was already demonstrated that laser ablation of aluminum alloy Al1050 (Al) prior to joining with polyamide 6.6 (PA) has significant influence on the joint quality, manifested in the joint area. However, profound understanding of the factors affecting the joint quality was missing. This work investigates the effects of laser ablation on the surface properties of Al, discusses their corresponding impact on the interfacial thermal transfer between the joining partners, and evaluates their effects on the joint quality. Samples ablated with different parameters, resulting in a range from low- to high-quality joints, were selected, and their surface properties were analyzed by using 2D profilometry, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX). In order to analyze the effects of laser ablation parameters on the interfacial thermal transfer between metal and polymer, a model two-layered system was analyzed, using laser flash analysis (LFA), and the thermal contact resistance (TCR) was quantified. Results indicate a strong influence of laser-ablation parameters on the surface structural and morphological properties, influencing the thermal transfer during the laser welding process, thus affecting the joint quality and its resistance to shear load.

Ultraviolet Laser Patterning of Fluorine-Doped Tin Oxide with Different Radiation Directions

Selective laser patterning of thin films in a multilayered structure is an emerging technology for fabricating optoelectronics and microelectronics devices. As the application of ultraviolet (UV) lasers is more and more popular in electronics manufacturing, in this study, we compare UV laser patterning of fluorine-doped tin oxide (FTO) films from the front and back sides. We summarize a formula for calculating the focus offset in back-side ablation (BSA) and analyze systematically the relationships between the laser ablation crater size, the damage on glass substrate, and the laser ablation parameters. In addition, the laser ablation process and mechanisms of the BSA and the front-side ablation (FSA) are also elaborated in this paper.

P2431Stay on the safe side: in-silico assessment of ablation protocols to prevent steam pops during radiofrequency ablation

Abstract Background Steam pops (SP) are among the most serious complications of radiofrequency ablation (RFA) due to its potential to cause myocardial tear or tamponade. SP occur when the tissue overheats, causing its water content to transform into steam and explode. Ablation parameters are critical in order to obtain an optimal lesion size while avoiding the occurrence of SP. However, the interaction between ablation settings and the physical parameters that predispose to SP occurrence during irrigated RFA are not fully understood. Purpose To characterize regularly used ablation protocols by means of a computational model, in order to achieve optimal lesion size while avoiding SP occurrence. Methods The in-silico evaluation is performed using our previously developed computational irrigated RFA model. Our model takes into account the blood-saline interaction as well as the mechanical deformation of the tissue due to the contact with the catheter tip. We test the effects of applied power and contact force on two catheter tip designs (spherical and cylindrical) and two substrates, simulated human atrium and ventricle, during 30 sec applications. A fixed blood flow and catheter-tip saline irrigation (0.5m/s and 17mL/min, respectively) are considered. We simulate human tissue by using the biophysical, mechanical and physiological properties found in the literature. SP occurrence is predicted when the temperature within the tissue reaches 100°C. Results Based on the interaction of power and contact force, four risk maps are constructed encompassing the two catheter-tip designs and the two simulated tissues. The maps allow the identification of those ablation protocols (contact force and delivered power) that can potentially result on SP. They correspond to that area of critical temperature values where the temperature within the tissue reach the established criteria for SP occurrence. We also present the lesion size dimensions of ablation protocols that avoid the formation of steam pops. Conclusion Our results indicate that the applied power has a strong impact in the formation of SP for a cylindrical catheter, while a combination of contact force and power is important to avoid risks in the case of the spherical catheter tip. The tissue characteristics do not affect significantly the SP occurrence, in agreement with experimental literature. However, the resulting lesion size appears to be larger in the simulated human atrium in comparison to the simulated human ventricle. Acknowledgement/Funding BERC 2018-2021, SEV-2017-0718