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Results for “pulsed field ablation”

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At least 19 recordsLinked to original sources

PubMed2026

Incidence of silent cerebral lesions during pulsed field ablation for paroxysmal atrial fibrillation.

BACKGROUND: Radiofrequency catheter ablation (RFCA) is a first-line treatment for paroxysmal atrial fibrillation (PAF). Complications such as silent cerebral lesion (SCL) may occur during ablation. Pulsed field ablation (PFA) is a non-thermal method thatablates cardiac tissue via irreversible electroporation. Limited studies have reported the incidence of SCL during PFA, with highly variable results. However, randomized controlled trials (RCTs) remain scarce. The objective of this study was to compare perioperative SCL incidence between PFA and RFCA, and to identify risk factors for SCL during PFA. METHODS: In this prospective pilot RCT (ChiCTR2400088774), 62 patients with PAF were randomized 1:1 to undergo PFA or RFCA. Cerebral MRI (3.0 T) was performed preoperatively and 24-48h postoperatively. SCL was defined as a new acute brain lesion on MRI without neurological deficits. Baseline and surgical data of the patients were collected. RESULTS: SCL was detected post-procedure in 6.45% (2/31) in the RFCA group, 12.90% (4/31) in the PFA group. No statistically significant difference in the incidence of postoperative SCL was detected between the two groups (p = 0.67). Left atrium dimension (LAD), left atrial operation time (LAOT), left ventricular end-diastolic dimension (LVEDD), and total operation time (TOT) were significantly higher in SCL group than those in no-SCL group (p < 0.05) through univariate analyses. CONCLUSIONS: SCL incidence was 12.90% in the PFA group versus 6.45% in the RFCA group. While no statistically significant difference was detected between two groups, the numerically higher rate in the PFA group warrants larger studies to evaluate cerebral safety associated with PFA.

Humans↗

PubMed2001

Nanoscale atmospheric pressure laser ablation-mass spectrometry.

We describe an atmospheric pressure nanosampling interface for mass spectrometry based on near-field laser ablation. Pulsed laser radiation is delivered to the sample surface through a near-field optical probe, and the ablation plume is sampled through a capillary orifice and analyzed by standard MS methods. A spatial resolution of less than 200 nm and a sensitivity below 2 amol is demonstrated.

Journal Article↗

PubMed1991

Selectivity, efficiency, and surface characteristics of hard dental tissues ablated with ArF pulsed excimer lasers.

Lasers are finding expanding applications in the field of dentistry. Cutting in soft tissue, hard dental material ablation, caries removal, and root canal therapy are only a few examples of dental laser uses. In this article, the application of short pulse ArF excimer laser to ablation of dentin and enamel is investigated. In particular, the effect of laser pulse repetition rates (PRR) and fluence levels on the efficiency of the ablation process and on the average thermal response of ablated surfaces is investigated. Ablation of dentin was found to be considerably more efficient than the ablation of enamel and depends exponentially on the laser fluence. Both dentin and enamel surfaces showed an increase in surface temperature with repetition rate. At lower PRR, however, temperature increases are very small. Surface temperature was also found to increase with laser fluence, although this increase is very small at laser PRR of 5 Hz or less. Tissue ablation rates were found to be comparable to or better than other nanosecond lasers, and left smooth surfaces, free of thermal damage. Microscopic examination of the ablated surface shows no crack formation, charring, discoloration, or any other thermal damage. The ablated surfaces appear to be very smooth, highly polished, and glossy looking as if they were subjected to thermal melting. This observation is indeed confirmed under scanning electron microscopy (SEM), where evidence of localized melting of the tissue is observed. Furthermore, a close SEM examination of the dentin surface reveals a selectively ablated intertubular dentin, while the remaining pillar-like dentin tubules are sealed off with fused peritubular dentin. At all fluence levels and PRR, the first three to four pulses impinging on an untreated enamel surface produced unusually large plumes of debris which were different in size, texture, and fluorescence emission characteristics from the ablation products of subsequent pulses. It is believed that these different ablation characteristics are a consequence of the pulsed ArF laser's ability to selectively remove residual matter from the more resistant enamel surface.

Acid Etching, Dental↗

PubMed1988

Percutaneous, in vivo excimer laser angioplasty: results in two experimental animal models.

Pulsed ultraviolet light from an excimer laser was successfully transmitted via conventional fused silica optical fibers and used to accomplish recanalization of stenotic or totally occluded arteries in an intact, flowing blood field of two atherosclerotic animal models. The fibers, 300-600 micron in diameter, were delivered percutaneously in wire-guided multilumen catheters and then used to transmit wavelengths of 308 or 351 nm from excimer lasers with pulse durations of 12 nsec or less. Lesions from 70-100% diameter narrowing, and 0.6 to 5.5 cm in length were successfully recanalized (less than 50% residual diameter narrowing) in eight animals, using 3-4 J/cm2/pulse, 10-50 Hz, and 48-370-sec cumulative exposure. Necropsy examination in six of the eight animals disclosed no signs of thermal injury. Perforations were observed in four of eight animals. Thus, while use of an excimer laser power source did not obviate vascular perforation as a complication of laser angioplasty, these preliminary results indicate that energies of pulsed ultraviolet light sufficient to ablate atherosclerotic plaque can be both transmitted via conventional fused silica optical fibers and used successfully within an intact, flowing blood field. It may therefore be possible to use pulsed ultraviolet light from an excimer laser to accomplish percutaneous ablation of atherosclerotic arterial obstructions in humans.

Angiography↗

PubMedDate not supplied

Thermal and non-thermal laser dissection.

Conventional cw-(continuous wave) laser systems such as the CO2- and Nd:YAG-laser are well established in medical therapy for tumour resection, tissue cutting, vaporisation and coagulation. The argon-ion laser is also a "classic" laser type with applications in ophthalmology, dermatology and for micro-surgery. New lasers in the IR-range of the optical spectrum appear on the market as pulsed lasers for tissue ablation searching for their specific fields of application. There is some confusion about laser applications at the moment until the new techniques and methods have proven to be really superior to other techniques. But knowing more about the laser tissue interactions one can estimate the potential of a new laser source. This article gives a short overview over the actual laser systems and the reaction processes with soft and hard tissue.

Dissection↗

PubMedDate not supplied

A systematic histologic analysis of nonablative laser therapy in a porcine model using the pulsed dye laser.

BACKGROUND: To our knowledge, no systematic analysis of nonablative laser therapy has been performed. OBJECTIVE: To alter the parameters (fluence, spot size, pulse duration, and use of cooling spray) for the pulsed dye laser to determine the precise settings that would yield the most favorable dermal remodeling in a porcine model. METHODS: Research was conducted in an animal laboratory at Albany Medical College. An anesthetized Yucatan miniature pig was subjected to a pulsed dye laser at various parameters. After 10 weeks, the laser-treated areas were harvested and processed for blinded, randomized, histologic evaluation. Negative (nontreated skin) and positive (ablative carbon dioxide laser-treated skin) controls were compared with the nonablative pulsed dye laser-treated areas. MAIN OUTCOME MEASURES: Quantitative assessment of collagen band width and cells per high-power field and qualitative assessment of epidermal and dermal changes. RESULTS: A significant difference (P<.001) in collagen band width was evident when nonablative laser-treated skin and carbon dioxide ablative laser-treated skin specimens were compared with untreated skin specimens, but no significant (P =.18) difference existed between the nonablative and ablative modalities. Similarly, cellular hypertrophy, as measured by high-power field, corroborated the previous findings. Furthermore, a higher fluence, a larger spot size, and a longer pulse duration proved statistically significant for increased collagen band width (P =.01, P<.001, and P<.001, respectively), and a larger spot size and a longer pulse duration exhibited significance for cells per high-power field (P =.02 and P =.009, respectively), with a trend toward significance for higher fluence (P =.09). Overall, the dermis was considerably thicker for nonablative and ablative laser-treated areas compared with untreated skin, but this could not be quantified because the depth exceeded the punch biopsy instrument. The epidermis remained unchanged. CONCLUSIONS: The nonablative pulsed dye laser has demonstrated favorable histologic evidence of dermal remodeling, and its effects were similar to histologic changes seen with the carbon dioxide ablative laser, both of which were statistically significant compared with untreated skin, as seen in this preliminary animal model.

Animals↗

PubMed2003

Facial rhytides--subsurfacing or resurfacing? A review.

UNLABELLED: STUDY DESIGN/BACKGROUND AND OBJECTIVES: Currently, ablative laser therapy (with CO2/Er:YAG lasers) is considered an effective and promising method of skin rejuvenation. The induction of collagen synthesis was observed after treatments with the CO2 laser and with the long-pulsed Er:Yag laser. In past years, the undesirable side effects and risks of these methods have led to intensified research efforts in the fields of non-ablative facial rejuvenation as well as subsurfacing by means of non-ablative laser systems and intense pulsed light systems. The objective is to achieve selective, heat-induced denaturalization of dermal collagen that leads to subsequent reactive synthesis of neocollagen but does not damage the epidermis. This article reviews the use of different types of lasers and intense pulsed light sources for the non-ablative treatment of facial rhytides. RESULTS: The results of numerous clinical and histological investigations have recently indicated that these new technologies are successful. Some studies demonstrated remarkable effects with non-ablative systems; others, however, showed only limited cosmetic improvement or none at all. CONCLUSIONS: After critical review and assessment of current literature on the treatment of rhytides, we have found that non-ablative methods do not appear to be a comparable alternative to ablative skin resurfacing in terms of their efficacy and side effects.

Face↗

PubMed2006

High-performance high-TC superconducting wires.

We demonstrated short segments of a superconducting wire that meets or exceeds performance requirements for many large-scale applications of high-temperature superconducting materials, especially those requiring a high supercurrent and/or a high engineering critical current density in applied magnetic fields. The performance requirements for these varied applications were met in 3-micrometer-thick YBa2Cu3O(7-delta) films epitaxially grown via pulsed laser ablation on rolling assisted biaxially textured substrates. Enhancements of the critical current in self-field as well as excellent retention of this current in high applied magnetic fields were achieved in the thick films via incorporation of a periodic array of extended columnar defects, composed of self-aligned nanodots of nonsuperconducting material extending through the entire thickness of the film. These columnar defects are highly effective in pinning the superconducting vortices or flux lines, thereby resulting in the substantially enhanced performance of this wire.

Journal Article↗

PubMed1998

Microscopically controlled surgical excision combined with ultrapulse CO2 vaporization in the management of a patient with the nevoid basal cell carcinoma syndrome.

Nevoid basal cell carcinoma syndrome is an autosomal dominant condition characterized by multiple basal cell carcinomas, skeletal abnormalities and sometimes mental retardation. The large number of tumors, which are often disfiguring, presents extreme difficulties in the treatment of these patients. Microscopically controlled excision, compared to other modalities (radiation therapy, photodynamic therapy, intralesional interferon alpha-2b) offers the highest cure rate. However, because of the large size and involvement of wide areas of the skin, this approach is sometimes impractical. The ultrapulse CO2 laser with high energy and short pulses achieves char-free ablation of the tumors, bloodless surgical field, minimal nonspecific thermal damage, rapid healing and diminished postoperative pain. Also, a number of lesions can be removed in a single session. We present a 48-year-old man with a 6.5 x 4.5 cm large basal cell carcinoma involving the anterior abdomen and navel area. The central thick portion of the tumor was resected by microscopically controlled excision with 3 stages, and wide thinner peripheral crescentic plaque vaporized with ultrapulse CO2 laser. The laser settings were 300 mJ energy/pulse and 100 W average power, which corresponds to the fluence of 7.5 J/cm2. Computerized pattern generator (ultrascan handpiece) was adjusted to patterns of 3 (circle) and 1 (square) with sizes varying from 5 to 7, and density of 9 (60% overlapping). The tumor was vaporized with 6 passes, all the way to deep reticular dermis. A fifteen month-follow up disclosed no recurrent disease. Subsequent biopsies revealed only a scar with postinflammatory hyperpigmentation. Our experience indicates that combined treatment with microscopically controlled excision and ultrapulse CO2 laser ablation is a suitable modality for the large tumor plaques involving concave and convex areas of the skin respectively. Microscopically controlled excision of thicker, concave portions of basal cell carcinoma plaques, where CO2 laser surgery is less feasible, presents an effective addition that renders this combined modality a successful method for the treatment of nevoid basal cell carcinoma syndrome.

Abdominal Neoplasms↗

PubMed1997

Hydroxyapatite coatings: a comparative study between plasma-spray and pulsed laser deposition techniques.

A comparative study between hydroxyapatite coatings produced by two different techniques, plasma spray (PS) and pulsed-laser deposition (PLD) was carried out. Plasma spray is currently commercially used for coating dental and orthopaedical implant devices, and pulsed-laser deposition (or laser-ablation deposition) gave good results in the field of high critical temperature superconductive thin films, and is being applied to produce calcium phosphate coatings for biomedical purposes. X-ray diffraction was used to control the crystallinity of the coatings, scanning electron microscopy for the surface and cross-sectional morphology, and the pull test to determine the tensile strength of the coatings. This study reveals that the pulsed-laser deposition technique appears to be a very good candidate to replace the plasma spray in many biomedical applications, because it overcomes most of the drawbacks of the plasma spray.

Journal Article↗

PubMed2001

Er:YAG laser skin resurfacing using repetitive long-pulse exposure and cryogen spray cooling: II. Theoretical analysis.

BACKGROUND AND OBJECTIVE: To analyze the effects of laser pulse duration and cryogen spray cooling (CSC) on epidermal damage and depth of collagen coagulation in skin resurfacing with repetitive Er:YAG laser irradiation. STUDY DESIGN/MATERIALS AND METHODS: Evolution of temperature field in skin is calculated using a simple one-dimensional model of sub-ablative pulsed laser exposure and CSC. The model is solved numerically for laser pulse durations of 150 and 600 microsec, and 6 msec cryogen spurts delivered just prior to ("pre-cooling"), or during and after ("post-cooling") the 600 microsec laser pulse. RESULTS: The model indicates a minimal influence of pulse duration on the extent of thermal effect in dermis, but less epidermal damage with 600 microsec pulses as compared to 150 microsec at the same pulse fluence. Application of pre- or post-cooling reduces the peak surface temperature after laser exposure and accelerates its relaxation toward the base temperature to a different degree. However, the temperature profile in skin after 50 msec is in either example very similar to that after a lower-energy laser pulse without CSC. CONCLUSIONS: When applied in combination with repetitive Er:YAG laser exposure, CSC strongly affects the amount of heat available for dermal coagulation. As a result, CSC may not provide spatially selective epidermal protection in Er:YAG laser skin resurfacing.

Burns↗

PubMed1996

Saline infusion in excimer laser coronary angioplasty.

While the effects of high-intensity laser energy on tissue were studied early in the development of the laser, the interactions of laser radiation with immersion media have been the subject of more recent investigations. Prompted by reports of severe, morphologically unusual dissections occurring during 308 nm excimer laser angioplasty, several investigators have now demonstrated that both blood (haemoglobin) and angiographic contrast media strongly absorb excimer laser light at 308 nm. Upon absorption, this light energy is converted into rapidly expanding and imploding cavitation bubbles that generate intense pressure pulses. Subsequently, several techniques to remove contrast and dilute blood in the ablation field were evaluated. The application of saline infusion has resulted in improvements in both angiographic and clinical outcomes. The purpose of this paper is to review the development and application of the technique of saline infusion in the clinical practice of excimer laser coronary angioplasty.

Angioplasty, Balloon, Laser-Assisted↗

PubMed2002

Plume dynamics and shielding by the ablation plume during Er:YAG laser ablation.

Free-running Er:YAG lasers are used for precise tissue ablation in various clinical applications. The ablated material is ejected into the direction perpendicular to the tissue surface. We investigated the influence of shielding by the ablation plume on the energy deposition into an irradiated sample because it influences the ablation dynamics and the amount of material ablated. The investigations were performed using an Er:YAG laser with a pulse duration of 200 micros for the ablation of gelatin with different water contents, skin, and water. Laser flash photography combined with a dark field Schlieren technique was used to visualize gaseous and particulate ablation products, and to measure the distance traveled by the ablating laser beam through the ablation plume at various times after the beginning of the laser pulse. The temporal evolution of the transmission through the ablation plume was probed using a second free running Er:YAG laser beam directed parallel to the sample's surface. The ablation dynamics was found to consist of a vaporization phase followed by material ejection. The observation of droplet ejection during water ablation provided evidence that a phase explosion is the driving mechanism for material ejection. The laser light transmission was only slightly reduced by the vapor plume, but decreased by 25%-50% when the ejected material passed the probe beam. At radiant exposures approximately 10 times above the ablation threshold, the laser energy deposited into the sample amounted to only 61% of the incident energy for gelatin samples with 90% water content and to 86% for skin samples. For free-running Er:YAG laser pulses shielding must therefore be considered in modeling the ablation dynamics and determining the dosage for clinical applications.

Animals↗

PubMed2002

["Skin rejuvenation" by non-ablative laser and light systems. Literature research and overview].

Currently, ablative laser therapy (with CO2/Er:YAG lasers) and deep chemical peeling are effective and promising methods of skin rejuvenation. The induction of collagen synthesis was observed after peelings with trichloroacetic acid or phenol as well as after treatments with the CO2 laser. In past years, the undesirable side effects and risks of these methods have led to intensified research in the fields of non-ablative facial rejuvenation and subsurfacing by means of ablative laser systems and intense pulsed light systems. The objective is to achieve selective, heat-induced denaturalisation of dermal collagen that leads to subsequent reactive synthesis but does not damage the epidermis. Recently, the results of numerous clinical and histological studies have indicated that these new technologies are successful. After critical review and assessment of current literature, we can say that in terms of their efficacy, non-ablative methods are not a comparable alternative to ablative skin resurfacing.

Female↗

PubMed1996

Two-lasers assisted ablation: a method for enhancing conventional laser ablation of materials.

A new method for enhanced ablation by pulsed laser radiation has been demonstrated. The method utilizes an "impulse" ablation laser in conjunction with cyclical heating of the tissue by an auxiliary source: the "primer." In this study we use an auxiliary laser as the "primer" heat source, which sets up a thermal and stress field modulation in the target material. The cyclical stress associated with the thermal modulation reduces material strength thus enhancing ablation (larger mass removed per pulse) by the "impulse" laser. Ablation rate enhancement of more than twice the single-laser value is demonstrated.

Hot Temperature↗

PubMed1998

Comparison of high-energy pulsed carbon dioxide laser resurfacing and dermabrasion in the revision of surgical scars.

BACKGROUND: Both dermabrasion and high-energy pulsed carbon dioxide (CO2) laser resurfacing can improve the appearance of surgical scars. Although the results of these two procedures have been compared using historical data, a prospective evaluation has never been performed in humans. OBJECTIVE: To prospectively compare the clinical effects of dermabrasion and high-energy pulsed CO2 laser resurfacing in the revision of surgical scars. METHODS: Facial surgical scars in four patients were prospectively revised using a split scar model. One half of the scar was dermabraded and the other half was resurfaced with the high-energy pulsed CO2 laser. Comparisons of the two treatment modalities were performed through clinical assessment, photographic evaluation, and textural analysis of the scars. RESULTS: The high-energy pulsed CO2 laser-resurfaced halves of the scar were bloodless with less postoperative crusting in comparison with the dermabraded halves. Reepithelialization time and degree and duration of postoperative erythema were similar for both treatment halves. Photographic evaluation and textural analysis showed comparable improvement in the clinical appearance and surface texture of the scars with both treatment modalities. CONCLUSIONS: Both the high-energy pulsed CO2 laser and dermabrasion can achieve comparable clinical improvement in the revision of surgical scars. The high-energy pulsed CO2 laser offers the advantage of a bloodless field and a more precise method of tissue ablation. Postoperative erythema, however, is an expected finding with both treatment modalities.

Aged↗

PubMedDate not supplied

Near-field optical photomask repair with a femtosecond laser.

We present a high-resolution near-field optical tool designed for repair of opaque defects in binary photomasks. Both instrument design and near-field imaging and patterning results will be presented. Designed for ablative processing of thin metal films, the MR-100 incorporates an industrial amplified femtosecond laser, third harmonic generator and built-in autocorrelator. The ultrashort duration of the femtosecond pulses enables the tool to remove chrome layers with negligible damage to the surrounding metal or the underlying quartz substrate. The micropipette based near-field writing head can deliver power densities of hundreds of GW/cm2 to spots of several hundred nanometres and below. Repairs on sample masks will be presented and the repair quality will be discussed.

Journal Article↗

PubMed2002

[Endocavitary ablation for arrhythmias. New modalities of radiofrequency applications. New energy types].

Radiofrequency remains the reference energy type for catheter ablation of rhythm disorders. In the classic indications, which are atrial flutter or tachycardia, nodal re-entry and Wolff-Parkinson-White syndrome, this energy source has the best cost-efficiency-safety ratio, subject to strict conditions of use. Some new modalities of application have further improved performance, especially active irrigation of the electrode which allows induction of deeper lesions which is very useful for the ablation of difficult atrial flutters, epicardial fascicles of Kent and ischaemic ventricular tachycardias. The only emerging alternative energy type, in the framework of classical ablation, is cold, for which the principal advantages are the homogenous and slightly thrombogenic character for the lesion involved, and the possibility of reversible applications tests which are especially useful in the ablation of structures at risk. The situation is more open-ended concerning research on ablation for atrial fibrillation or the so-called new energy types, such as ultrasound and laser, whilst recognising a renewal in interest, especially for circumferential ablation of the pulmonary veins to isolate the ectopic venous foci. Mechanical energy such as luminous energy is emitted across a catheter balloon deployed at the orifice of the vein, perpendicular to its axis, aiming to reach a continuous circumferential lesion with a minimum of applications. Equally radiofrequency has been undergoing significant evolution for this application, such as by the development of porous catheter balloons with a liquid electrode, as well as by the development of deployable circumferential catheters. Ablation is use for atrial fibrillation, by endocavity atrial segmentation remains a field of research in which radiofrequency retains an important place. It is delivered via multi-electrode catheters according to the new application modalities, either pulsed or by phase interval, which secure better efficacy by better continuity of the line of block. Research is equally underway on the use of microwaves and cold in this application.

Atrial Fibrillation↗