Ablation Mode Research Articles

Láser CO2 ablativo en angiofibroma facial por esclerosis tuberosa

Se presenta el caso de un paciente de 25 años con múltiples pápulas y placas de aspecto fibroso, distribuidas principalmente en cara, además de cuero cabelludo, tórax y región periungueal pedia, asintomático. Se realizó el diagnóstico clínico e histopatológico de esclerosis tuberosa, enfermedad genética poco frecuente. Se utilizó láser CO2 modo ablativo en 2 ciclos de dos sesiones cada una, en lesiones cutáneas faciales (angiofibroma facial), con el objetivo de mejorar la apariencia y promover calidad de vida. Como resultado se evidenció mejoría de la apariencia y ausencia de recidiva con un método terapéutico moderno y aún inaccesible a todas las personas en nuestro país.

Effective femtosecond laser shock peening on a Mg–3Gd alloy at low pulse energy 430 µJ of 1 kHz

In this paper, microstructure evolution and hardness of Mg-3Gd alloy treated by femtosecond (fs) laser shock peening (LSP) with direct and confined ablation modes were investigated in detail. Under a relatively low pulse energy of 430 µJ with a repetition of 1 kHz, the surface hardness of sample has been enhanced by 70% effectively. Compared with ns-LSP with pulse fluence of 71.7 J/cm2, fs-LSP with pulse fluence of 34.2 J/cm2 is superior in the hardness increment, both of which are in the same order of magnitude. A distinct grain refinement of surface layer has been discovered and results in the increase of hardness. Nonuse of absorption and confining layers and the employment of the industry commercial fs laser with high repetition can inspire big potential LSP application in special metal material.

Clinical study on combining femtosecond thin- flap and LASIK with the Triple-A profile for high myopia correction

BackgroundFemtosecond laser–assisted LASIK (FS-LASIK) can make ultra-thin corneal flap accurately. MEL 90 excimer laser provides Triple-A ablation mode, which significantly reduces the amount of corneal tissue cutting. This study aimed to investigate the visual and refractive outcomes in patients with high myopia after thin-flap FS-LASIK using the 500 Hz pulse rate of the Triple-A profile.MethodsThis prospective study included 90 eyes from 90 patients received thin-flap FS-LASIK using the 500 Hz pulse rate of the Triple-A profile. According to the pre-operative spherical equivalence (SE), the treated eyes were divided into two groups: the first group (ranged from − 9.0D to − 6.0D) and the second group (ranged from − 11.15D to − 9.0 D). The parameters evaluated pre-operatively and 6 month post-operatively included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), SE, efficacy and safety index, posterior central elevation, and corneal higher-order aberrations (HOAs).ResultsThe efficacy indexes were 1.149 ± 0.150 for the first group and 1.173 ± 0.136 for the second group (P > 0.05), whereas safety indexes were 1.135 ± 0.154 and 1.158 ± 0.137 (P > 0.05) respectively. Moreover, 93.8 and 90.6% of patients had an UDVA of 20/20, 51.2 and 49.8% had a UDVA of 20/16 for the first and second groups, respectively; yet, there were no significant differences between both groups at the 20/20 and the 20/16 levels (P > 0.05). 84 and 100% of the firse group patients had a SE within ±0.5 D and ± 1.0 D, and 82 and 100% of the second group patients. There was no significant myopia regression in both groups after 6 months follow-up. At 1, 3 and 6-month after surgery, there were no significant differences in the posterior central elevation between the two groups (P > 0.05). The induction of total HOAs, spherical aberration, and horizontal coma in the first group were significantly less than that in the second group at the 6- month follow-up (P < 0.05), while the differences of the RMS value of vertical coma between both groups were not significant (P > 0.05). The ablation was significantly associated with the post-operative increase in total HOAs, spherical aberration and horizontal coma (P < 0.05),but not with vertical coma (P > 0.05).ConclusionOur results indicate that using the Triple-A ablation profile of the MEL 90 excimer laser associated with thin-flap is a safe, efficient, and predictable method to correct SE up to − 11.15D. However, for patients with high myopia, under the premise of ensuring a certain optical zone diameter, the ablation depth should be minimized to reduce the increase of the post-operative HOAs so as to improve the visual quality.

Pulsed anodic arc discharge for the synthesis of carbon nanomaterials

Pulsed arc discharges can improve arc control and tailor the ablation process in the production of 1D and 2D nanostructures from carbon anodes. In this work, low-dimensional carbon nanoparticles have been generated by means of anodic arc discharge in helium atmosphere excited with a square-wave modulated signal (1–5 Hz, 10% duty cycle). The discharges were performed between two graphite electrodes with maximal peak current of 250 A and maximal voltage of 65 V. The erosion rates and conversion efficiency of the ablated anode are compared to reference samples grown in DC steady arc mode. Ablation rates in pulsed arcs are typically of the order of 1 mg s−1. Combination of fast Langmuir probe diagnostics and optical emission spectroscopy provided plasma parameters of the discharges at the arc column. Ranges of 1016–1017 m−3 for electron density and 0.5–2.0 eV for electron temperature are estimated. The obtained samples were characterized with Raman spectroscopy and scanning electron microscopy. The deposit on the cathode after pulsed arc consisted of carbon nanostructures such as graphene nano-platelets and carbon nanotubes. Erosion dynamics of pulsed arc discharge has been described in terms of a global model and compared to steady arc discharge. A correlation is identified among discharge regimes, optical emission patterns and ablation modes. In conclusion, pulsed anodic arc discharge is a very efficient source of carbon nanomaterials. The large control of the discharge characteristics will permit to tailor accurately the production and the properties of carbon nanotubes and graphene. This deposition method is promising for the fabrication of semiconducting nanomaterials with tuneable electrical and optical properties.

Multispecies plasma fluid simulation for carbon arc discharge

Understanding of the plasma physics in ablating carbon arcs plays an important role in the synthesis of carbon nanomaterials. In this paper, ablating carbon arc discharges in atmospheric pressure conditions are modeled using a one-dimensional fluid model. The mass and momentum conservation equations are solved for individual species in the arc, and intermolecular collisions between species are considered. Energy equations for the electrons and the heavy species are solved separately without the use of local thermodynamic equilibrium condition. The bulk plasma model is coupled with sheath models at the electrodes, which provide the sheath potential drop and electrode temperatures. A model to determine the size of the cathode deposit formation is also proposed using the principle of minimized energy loss. The numerical results show a qualitative agreement with experiments for the transition between low and high ablation modes that is observed when varying the total current or the anode diameter. While the numerical results suggest that the electron and heavy species temperatures are not in equilibrium, mainly due to the one-dimensional approximation of the model, it is shown that the radiative heat flux between the electrodes plays an important role in determining the anode temperature, which affects the ablation rate and in turn the bulk plasma.

Features of thermal effect at high-frequency laser impact on biological tissue (experiment). Technique of laser ablation of a pharyngeal tonsil

In the conditions of the experiment the peculiarities of thermal influence of Ho:YAG on biological tissue in the ablation mode were studied. In the experiment we used: surgical laser system LUMENIS VersaPulse PowerSuite 20, universal thermal imaging camera FLIR SC7000. The biological object (turkey meat) was remotely, at a distance of 5 mm, affected by a Holmium laser (E = 0.9 J and R = 12 Hz) for 6 seconds. The maximum temperature (Tmax, °C) in the ablation zone was measured in real time. As a result, it was found that laser ablation of a biological object is characterized by thermal effects, which largely depend on the state of irradiated tissue: the temperature of the irradiated object rises to critical values equal to 100.07-111.24 ° C, after which the surface layer of biological tissue is charred, and the process of laser "removal" stops; intact biological tissue reaches critical heating after 3.48 s, while under the influence of a high-frequency laser on the previously irradiated biological tissue development period It was also established that in order to continue laser ablation with controlled thermal effect it is necessary to remove charred areas of biological object. On the basis of the obtained data the method of laser ablation of pharyngeal tonsils was developed.

Optimization of Analysis Conditions by the Method of Inductively Coupled Plasma Mass Spectrometry with Laser Sampling

The effect of laser radiation parameters on the sensitivity and relative sensitivity coefficients of element determination in the analysis of various materials by inductively coupled plasma mass spectrometry in combination with laser ablation is studied. It is found that, when the power density of laser radiation is increased above 2 × 1010 W/cm2 for the samples based on silicate glass, basalt glass, and polymetallic sulfides, the laser ablation mechanism changes from thermal to “phase explosion.” It is shown that the coefficients of relative sensitivity of determination of impurity elements with respect to the matrix elements change by no more than 3–5% when the power density varies in the range of 5 × 109–1.5 × 1011 W/cm2. For most impurity elements, the coefficients of the relative sensitivity of determination in different matrices differ by no more than 10–15%, but for a number of elements, a significant difference up to 1.5–2 times is observed. A comparative study of two ablation modes is carried out: when the laser beam is moved along the surface of the sample and during ablation at a “point.” It is shown that the sensitivity of determination of the elements in the first case is 2–3 times higher, while the coefficients of the relative sensitivity of determination are the same for both cases.

Insulator ablation modes in different impact conditions of alumina droplets onto wall surfaces

Current understanding of insulator ablation modes under different alumina droplet impact conditions onto wall surfaces in solid rocket motors (SRM) is limited. This study uses theoretical analysis and numerical calculations to design a lab-scale experimental device and an ultra-high-temperature heat flow gauge. Alumina droplet/insulator wall surface impact characteristics such as erosion angle, speed, and droplets size distribution are discussed based on the resulting experimental data using the proposed design. Three ablation modes are established according to the droplet speed threshold: the weak erosion state, deposition state, and strong erosion state. On this basis, heat transfer characteristics are studied under the condition of high-density, two-phase flow and the general rules of the wall heat increment with droplet concentration, size, and velocity under different droplet/wall impact modes are obtained. Finally, discussing multi-factor variables, the coupling relationship among the thermal increment, thermal chemical ablation, and mechanical erosion under droplet/wall surface action is analysed, providing insights toward establishing an insulator ablation model.

Comparison of efficacy and safety of intralesional triamcinolone and combination of triamcinolone with 5-fluorouracil in the treatment of keloids and hypertrophic scars: Randomised control trial

The treatment of keloid and hypertrophic scar is challenging with no universally accepted mode for permanent ablation. Conventional therapies yield unpredictable results, significant complications and require elaborate hardware. ObjectiveThe objective was to establish the safety and efficacy of intralesional 5-fluorouracil (5-FU) for the treatment of keloids and hypertrophic scars. Study designRandomized controlled trial (RCT). Place and durationIt was conducted at the Jinnah Burn and Reconstructive Surgery Center/Allama Iqbal Medical College, Lahore, Pakistan from May 2012 to March 2013. Subjects and methodsWe included 120 patients divided in two groups. The group A patients received intralesional triamcinolone acetonide (TAC) and the group B patients received both 5-FU and TAC. 8 injections at a week interval were given and patients were evaluated at the start of treatment and then at 4th and at 8th week during the treatment and then 4 weeks after the end of treatment. Patents were assessed for mean reduction in scar height, efficacy and complications. ResultsTotal of 108 patients completed the study. The mean reduction in the scar height in group B (5-FU+TAC) 1.144+.4717 was markedly better than that of group A (TAC alone) 1.894+1.0751 (t=4.781, p=.000). The efficacy (defined previously as >50% reduction in initial scar height) was superior in group B 44 (77.2%) than that of group A 25 (49.0% (X2=9.260, p=.002). Recurrence was seen in 39.2% (20) of patients of the group A while in only 17.5% (10) of the cases of group B (P=0.012). Mean follow up was of 22 months. Conclusion5-FU+TAC is safe, easy to administer and effective treatment for problematic scars and has the lower rate of recurrence on larger follow up.

Progress of Frequency Ablation Technique on Atrial Fibrillation Treatment

Atrial Fibrillation(AF) and its complications are serious threat to human health and the radio frequency ablation (RFA) becomes one of the main therapies of AF. Conventionally, the RFA is performed by unipolar ablation mode. Because the unipolar ablation mode is point-to-point and incomplete linear lesion formation, the success rates of treatment on AF decline and the procedures are time consuming. In order to solve these shortcomings, the bipolar ablation mode and the multichannel frequency ablation method that facilitate the easy creation of linear lesion are presented, especially kinds of multichannel frequency ablation technique and applications are introduced in this paper.

Development, safety and efficacy of a novel circular-irrigated deca-channel mapping and ablation catheter for pulmonary vein isolation

BackgroundPulmonary vein isolation (PVI), a cornerstone for catheter ablation of atrial fibrillation (AF), remains a complex and time-consuming procedure. Present study introduces a novel, circular-irrigated, deca-channel mapping and ablation catheter (CIDMA), describes the in vitro test results on feasibility, safety, and acute efficacy of the CIDMA catheter.MethodsAn assembled CIDMA catheter was subjected to a number of in vitro tests. With this catheter, ablation procedures were first performed in a pig’s myocardial strips in vitro to determine the effects in unipolar or bipolar configuration.ResultsThree catheters were assembled. The adjustable circular diameter was changed from initial state of 32.41 ± 0.61 mm into controlled state of 28.61 ± 0.47 mm (P = 0.013). In the plastic model, the push-ability, torque-ability, and kink resistance of CIDMA catheter were shown to be satisfactory.In vitro, our findings showed that ablation could produce obvious ablation lesions, and unipolar ablation (at length, width and depth of 5.0 ± 1.3, 4.6 ± 0.7, and 4.2 ± 0.6 mm, respectively) was more effective than bipolar (at length, width and depth of 2.8 ± 0.2, 4.2 ± 0.5, and 2.3 ± 0.4 mm, respectively) (P < 0.01).ConclusionsIn vitro, our preliminary data suggest that the CIDMA catheter produced optimal ablation lesions, especially in the unipolar ablation mode. Future in vivo animal and clinical studies are warranted to test the efficacy of this catheter in real-world scenario.

The influence of material properties on highly time resolved particle formation for nanosecond laser ablation

The dynamics of aerosol particles formed during nanosecond laser ablation of glass and steel samples was studied in the Laser Ablation – Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) system. In order to follow the evolution of particle size distribution with high time resolution during the laser ablation process, two fast response aerosol spectrometers were used. Engine Exhaust Particle Sizer (EEPS) together with Optical Particle Sizer (OPS) provided Particle Size Distribution (PSD) in the range 5.6 nm – 10 μm with the integration time of 1 s. To obtain additional information about the PSD of larger particles (0.5–10 μm) in more detail, an Aerodynamic Particle Sizer (APS) recorded average PSD of each ablation (80 s). To investigate the effect of the sample matrix on aerosol dynamics and composition, glass NIST 610 and steel F4 samples were studied. Spot and line ablation mode was applied to compare the behavior of both ablation modes in time. The degree of thermal effect and fractionation was studied from the structure and size of ablation craters, the structure of particles and the LA-ICP-MS signal. The ablation process was influenced mostly by the material itself even if the ablation mode also plays an important role on the formation of aerosol. A significant correlation of ICP-MS signal with a concentration of particles >300 nm was observed.

Ablative dual-phase Erbium:YAG laser treatment of atrophy-related vaginal symptoms in post-menopausal breast cancer survivors omitting hormonal treatment

First evaluation of dual-phase vaginal Er:YAG laser to omit hormonal treatment for atrophy-related symptoms in post-menopausal breast cancer survivors following prolapse surgery. Patients with a history of breast cancer at the time of surgery for pelvic organ prolapse were offered non-hormonal vaginal Er:YAG laser treatment when complaining of atrophy-related genitourinary syndrome of menopause. A single 10-min course of dual-phase protocol of pulsed Er:YAG laser (2940nm, fractional ablative and thermal mode, fluence according to tissue thickness). Follow-up included subjective satisfaction, vaginal pH, vaginal health index (VHI), and complications after 6weeks. A total of 16 breast cancer survivors (age 71years, SD 7) had been seeking treatment for pelvic floor symptoms related to vaginal atrophy at follow-up visits after prolapse surgery. All ablative vaginal Er:YAG laser outpatient procedures were successfully completed, all patients returned to daily activities without a need for analgetic medication. Evaluation was performed after 8.3 (SD 2.5) weeks. Pre-laser VHI scored 16 (SD 4.6) and post-laser VHI 20 (SD 3) with p = 0.01. Patients were satisfied in 94% (n = 15) regarding symptom relief. Breast cancer survivors with atrophy-related complaints after pelvic floor surgery may benefit from vaginal application of this innovative dual protocol of Er:YAG laser technology as a non-hormonal treatment approach.

RF-energised intracoronary guidewire to enhance bipolar ablation of the interventricular septum: in-silico feasibility study

Purpose: Although bipolar radiofrequency (RF) ablation (RFA) is broadly used to eliminate ventricular tachycardias in the interventricular septum wall, it can fail to create transmural lesions in thick ventricular walls. To solve this problem, we explored whether an RF-energised guidewire inserted into the ventricular wall would enhance bipolar RFA in the creation of transmural lesions through the ventricular wall.Methods: We built three-dimensional computational models including two irrigated electrodes placed on opposing sides of the interventricular septum and a metal guidewire inserted into the septum. Computer simulations were conducted to compare the temperature distributions obtained with two ablation modes: bipolar mode (RF power delivered between both irrigated electrode) and time-division multiplexing (TDM) technique, which consists of activating the bipolar mode for 90% of the time and applying RF power between the guidewire and both irrigated electrodes during the remaining time.Results: The TDM technique was the most suitable in terms of creating wider lesions through the entire ventricular wall, avoiding the hour-glass shape of thermal lesions associated with the bipolar mode. This was especially apparent in the case of thick walls (15 mm). Furthermore, the TDM technique was able to create transmural lesions even when the guidewire was displaced from the midplane of the wall.Conclusions: An RF-energised guidewire could enhance bipolar RFA by allowing transmural lesions to be made through thick ventricular walls. However, the safety of this new approach must be assessed in future pre-clinical studies, especially in terms of the risk of stenosis and its clinical impact.

Laser ablation mechanism of contamination on surface of single crystal iron

The laser induced damage in high-power laser system has received much attention in the area of laser engineering. Optical components with contaminants, which are installed in the final optical assembly (FOA), can be severely damaged under the action of extremely high laser energy. So the ultra-high cleanliness inside the high-energy laser system is required for both optical and mechanical components. Research shows that a large part of the metal particulate contaminants inside the device come from the mechanical components. The metal particulate contaminants are produced when mechanical structure surface is damaged under the irradiation of stray light. However the research about the cleanliness inside the device is mostly concentrated on the surfaces of optical components currently. The laser ablation of the mechanical components absorbing contaminants is studied little, so it is quite important to investigate the ablation mechanism of mechanical components under laser irradiation. Due to the presence of contaminants on the surfaces of mechanical components, laser ablation of monocrystalline iron absorbing contaminants is investigated by using molecular dynamics simulation. The ablation process of iron material under laser irradiation is presented. The influences of loading mode and energy density of laser as well as contamination on the surface are analyzed in the ablation process of monocrystalline iron. The results indicate that the surface atoms of monocrystalline iron show different motion states under the violent collision of contaminants atoms after laser loading. Ablated iron can be divided into ablation zone, melting zone and crystal zone according to the variation of the temperature and mass density of the atoms in each region of the ablated material. The atoms in each region show macroscopic characteristics of gaseous, liquid and solid atoms respectively. Iron is damaged more easily when laser energy is instantaneously loaded. Contaminants on the surface of iron can be removed, and iron cannot be damaged when laser energy density is below 0.0064 J/cm&lt;sup&gt;2&lt;/sup&gt;. The result of the analysis shows that the presence of contaminants makes the ablation of iron easier. Different energy loading modes affect the heat transfer mode directly. Monocrystalline iron materials are more likely to be damaged in the mode of adiabatic laser ablation in the case of short laser pulse. Thermal effect can be thought as a dominant factor for the ablation in the case of long laser pulse. The research results of this paper are helpful for providing the theoretical basis for improving the cleanliness of high-power laser system.

Optimization exploration of laser ablation propulsion performance of infrared dye doped glycidyl azide polymer

The energetic polymer glycidyl azide polymer (GAP) is selected as the propellant of laser ablation micro thruster, and the effect of infrared dye doping on the propelling performance of laser ablative GAP is analyzed. By comparing the propulsion performance data with the plumes of infrared dyes doped GAP under different laser intensities, doping concentrations, target thickness and laser ablation modes, the optimization of the propulsion performance of infrared dye doped GAP is explored preliminarily. The experimental results show that the exponential attenuation characteristics of laser energy and the strong viscosity of GAP doped with infrared dye in the transmission mode lead to the existence of incomplete ablative GAP in the plume. The propulsion performances of GAP are influenced by the doping concentration of infrared dye and the thickness of propellant. Only when the target thickness is close to the laser absorption depth, can the mass of incomplete ablation along the direction of laser propagation be the least and can the laser energy be fully absorbed by the propellant to make the central ablation region reach the temperature threshold of the release of chemical energy. At the same time the optimum value of propulsion performance can be achieved. The GAP doped with infrared dyes in which laser ablation process follows the rule of absorbing laser energy first and spraying first is decomposed adequately under the reflection mode and the propelling performance is better than that in the transmission mode.

Application of 1013 ohm Faraday cup current amplifiers for boron isotopic analyses by solution mode and laser ablation multicollector inductively coupled plasma mass spectrometry.

Boron isotope ratios (δ11 B values) are used as a proxy for seawater paleo-pH, amongst several other applications. The analytical precision can be limited by the detection of low intensity ion beams from limited sample amounts. High-gain amplifiers offer improvements in signal/noise ratio and can be used to increase measurement precision and reduce sample amounts. 1013 ohm amplifier technology has previously been applied to several radiogenic systems, but has thus far not been applied to non-traditional stable isotopes. Here we apply 1013 ohm amplifier technology for the measurement of boron isotope ratios using solution mode MC-ICP-MS and laser ablation mode (LA-)MC-ICP-MS techniques. Precision is shown for reference materials as well as for low-volume foraminifera samples. The baseline uncertainty for a 0.1 pA 10 B+ ion beam is reduced to <0.1 ‰ for a typical measurement period. The external precision is better than 0.2 ‰ (2SD) for δ11 B measurements for solution samples containing as little as 0.8 ng total boron. For in situ microanalyses with LA-MC-ICP-MS, the external precision of 11 B/10 B from an in-house calcite standard was 1 ‰ (2SD) for individual spot analyses, and 0.3 ‰ for the mean of ≥10 replicate spot analyses. 1013 ohm amplifier technology is demonstrated to offer advantages for the determination of δ11 B values by both MC-ICP-MS and LA-MC-ICP-MS for small samples of biogenic carbonates, such as foraminifera shells. 1013 ohm amplifier technology will also be of benefit to other non-traditional stable isotope measurements.

Laser shock peening studies on SS316LN plate with various sacrificial layers

Laser shock peening (LSP) has been utilized to modify the surface characteristics of SS316LN plates of 6mm thickness. Laser pulse widths employed are 30ps and 7ns and the laser energy was varied in the range 5–90mJ. Peening was performed in direct ablation mode as well as with various sacrificial layers such as black paint, transparent adhesive tape and absorbing adhesive tape. The surface characteristics were greatly influenced by the type of sacrificial layer employed. The average surface roughness values are about 0.4μm when the black paint and transparent adhesive tape were used as sacrificial layers. In contrast to this, using absorbent adhesive tape as a sacrificial layer has resulted in an average surface roughness of about 0.04μm. Irrespective of pulse durations (30ps or 7ns), absorbent adhesive tape has always resulted in compressive residual stresses whereas other layers appear to be not that effective. In case of 30ps pulse, as the laser energy was increased from 5mJ to 25mJ, there was a texture observed in (111) reflection of X-ray diffractograms and the center of the peak has also gradually shifted to left. X-ray line profile analysis suggests that with the increase in laser energy, lattice microstrain also has increased. This lattice microstrain appears to be resulting from the increased dislocation density in the peened sample as evidenced during transmission electron microscopic investigations. Cross-sectional scanning electron microscopy performed on peened samples suggests that absorbing adhesive tape brings no surface damage to the samples whereas other sacrificial layers have resulted in some surface damage. Based on all these structural and microstructural details, it is recommended that absorbent tape could be used as a sacrificial layer during LSP process which induces surface residual stresses with no damage to the sample surface.

In Vitro and In Vivo Investigation of High-Intensity Focused Ultrasound (HIFU) Hat-Type Ablation Mode.

BackgroundThe aim of this study was to investigate the feasibility of the application of high-intensity focused ultrasound (HIFU) hat-type ablation mode in in vitro and in vivo models, and to compare the ablation effects of different parameter combinations.Material/MethodsHIFU hat-type ablation was performed in isolated bovine liver tissue and in the liver tissue in living rabbits, and the coagulative necrosis for different parameter combinations (plane angles and irradiation order) was investigated. We also analyzed and compared the ablation effects of traditional ablation and hat-type ablation modes. Coagulative necrosis morphology was detected with TTC staining, and the coagulative necrosis volume and energy efficiency factor (EEF) were calculated and compared.ResultsCoagulative necrosis was observed in all the ablated groups, and the coagulative necrosis volume was much larger than the irradiation area. The coagulative necrosis induced by the hat-type ablation was more regular and controllable than the traditional ablation. The angles between the ablation planes determined the coagulative necrosis morphology, but did not affect the coagulative necrosis volume. Moreover, the irradiation order significantly influenced the coagulative necrosis. Importantly, under certain conditions, hat-type ablation achieved higher efficiency compared with the traditional ablation mode.ConclusionsCompared with the traditional ablation mode, HIFU hat-type ablation effectively shortened the irradiation time, reduced the over-accumulation of energy, and increased the HIFU ablation efficiency.

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

Purpose: 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.Materials and methods: 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.Results: 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.Conclusions: Amplitude control ablation technology and bipolar ablation technology are feasible methods to create continuous lesion or discrete for pulmonary veins isolation.