Bare Fiber Tip Research Articles

Endovenous Laser Ablation of Incompetent Anterior Accessory Saphenous Veins of Different Anatomical Patterns Using Bare-Tip Fibers: A Case Series

Endovenous Laser Ablation of Incompetent Anterior Accessory Saphenous Veins of Different Anatomical Patterns Using Bare-Tip Fibers: A Case Series

Endovenous laser ablation vs phlebectomy of foot varicose veins

ObjectiveThe aim of this study was to compare the outcomes and complications of selected patients treated with endovenous laser ablation (EVLA) or ambulatory phlebectomy for foot varicose veins. MethodsFrom October 2016 to February 2022, selected patients undergoing EVLA (using 1470-nm with radial-slim or bare-tip fibers) or phlebectomy of foot varicose veins for cosmetic indications were analyzed, and the outcomes were compared. Patients were classified according to the Clinical, Etiologic, Anatomical, and Pathophysiological (CEAP) classification. Anatomic criteria provided the basis for the decision to perform EVLA or phlebectomy. Clinical and ultrasound assessments were performed on postoperative days 7, 30, and 90 for visualization of the sapheno-femoral and sapheno-popliteal junctions and the deep venous system. Disease severity was graded with the Venous Clinical Severity Score (VCSS), and quality of life was measured with the Aberdeen Varicose Vein Questionnaire (AVVQ) before and after treatment. Treatment outcomes were evaluated based on changes in VCSS and AVVQ scores. The groups were also compared for procedure-related complications. Data were statistically analyzed in SPSS v. 20.0 using the χ2, Student t test, Mann-Whitney test, Wilcoxon test, and analysis of variance. The results were presented as mean (standard deviation or median (interquartile range). ResultsThe study included 270 feet of 171 patients. Mean patient age was 52.3 (standard deviation, 13.1) years, ranging from 21 to 84 years; 133 (77.8%) were women. Of 270 feet, 113 (41.9%) were treated with EVLA and 157 (58.1%) with phlebectomy. The median preoperative CEAP class was 2 (interquartile range, 2-3) in the phlebectomy and EVLA groups, with no statistically significant difference between the groups (P = .507). Dysesthesia was the most common complication in both groups. Only transient induration was significantly different between EVLA (7.1%) and phlebectomy (0.0%) (P = .001). The two approaches had an equal impact on quality of life and disease severity. ConclusionsTreatment complications were similar in phlebectomy and EVLA and to those previously described in the literature.

Prospects for Developing Low-Cost Optical Fiber Sensors for Liquid-Liquid Interface Detection

This work examines the prospects of a low-cost retroreflection optical sensor system for detection of the interface between two immiscible liquids, for applications in oil separation tanks. The sensor in its simplest configuration comprises a bare fiber optic tip, cleaved at an angle of 90º relative to the longitudinal fiber axis. The device tested experimentally is based on a 2x2 bidirectional coupler, which connects the sensor tip to a laser and two photodetectors, one used to measure the signal and the other as a reference. From experiments conducted in a laboratory wateroil system, the measured retro-reflected signal was very small, and of the same order as the differential signal due to low optical contrast liquids. To overcome this difficulty, the detection system was designed with an amplification stage, followed by filtering of the digitally converted signal. With this strategy, an accuracy of 99.7% was reached. On the light of the performance measured by the bare fiber tip configuration, an analysis on the potential improvement in performance obtained, by applying a thin layer of gold to the tip of the sensor, was made. Simulated results indicated that, for an optimized gold film, 13 nm thick, a 13fold improvement in the sensor detection limit is obtained.

Morphological changes of veins and perivenous tissues during endovenous laser coagulation using 2-μm laser radiation and various types of optical fibers

ObjectiveTo determine the morphological changes in veins and perivenous tissues after endovenous laser coagulation (EVLC) using laser radiation with a wavelength of 1910 nm and different types of fibers (bare tip and radial). MethodsThe EVLC procedure was carried out on 22 surface veins of six sheep. The radiation source was a diode-pumped solid-state laser, which was based on a LiYF4:Tm crystal and had an emission wavelength of 1910 nm and a maximum output power of 10 W. Two types of optical fibers were used: (1) bare tip and (2) radial or radial with two rings. Histological and morphometric methods were used, and the statistical digital data were analyzed. ResultsThe use of a linear endovenous energy density of 20 J/cm and optical bare fibers for veins with diameters of 3-4 mm resulted in a slit-shaped or wide venous wall perforation. A thermal effect was observed on the perivenous connective tissue (PVCT), which caused damage to its structures. Wide perforations were accompanied by complete destruction of the PVCT in the projection of the formed defect. The distance between the remaining vein wall fragment, located opposite to the perforation, and injured small vessels was 257.7 ± 23.6 μm. The radius of thermal damage increased to 2073.5 ± 8.0 μm near the vessel perforation. Using optical radial fibers for veins with diameters of 3.9 ± 0.5 mm did not lead to perforations. The destructive effect of the laser on small vessels of the PVCT extended to a distance of 425.7 ± 22.0 μm. ConclusionsAnalysis of thermal vessel damage in perivenous tissue after EVLC with bare-tip fiber shows that in the projection of a wide perforation, the damaged vessels of the PVCT are located at a large distance from the coagulated vein wall. On the opposite side of the perforation, the distance from the coagulated vein wall to the damaged vessels of the PVCT is significantly reduced because of the minimal output of laser radiation energy through the poorly damaged part of the wall. Using an optical radial fiber facilitates the application of a uniform distribution of thermal energy to the vein wall and damage to all its layers; at the same time, it minimizes the thermal energy that extends beyond the vein wall and damages the surrounding tissue. Clinical RelevanceThe use of radiation with a wavelength of 1910 nm will make it possible to carry out endovenous laser coagulation of varicose veins at lower power values compared with radiation in the micron and one and a half micron regions of the spectrum. Understanding of morphological changes of veins and perivenous tissues after endovenous laser coagulation with 1910-nm laser radiation and different types of optical fibers (bare-tip, radial, radial 2ring) help predict possible complications and reduce their rate.

Ten-year follow-up of a randomized controlled trial comparing saphenofemoral ligation and stripping of the great saphenous vein with endovenous laser ablation (980 nm) using local tumescent anesthesia

ObjectiveThe long-term results of saphenofemoral ligation and stripping (SFL/S) were compared with 980-nm bare fiber endovenous laser ablation (EVLA) for the treatment of great saphenous vein (GSV) incompetence. MethodsThis was a single-center, randomized, controlled trial with a follow-up time of 10 years. Patients with GSV incompetence were randomized to undergo SFL/S or EVLA under tumescent anesthesia. The primary outcome was recurrence of groin-related varicose veins seen on duplex ultrasound imaging and clinical examination. The secondary outcomes were (changes or improvement in) CEAP clinical class, venous symptoms, cosmetic results, quality of life, reinterventions, and complications. ResultsBetween June 2007 and December 2008, 122 patients (130 limbs) were included; of these, 68 limbs were treated with SFL/S and 62 limbs with EVLA. The 10-year estimated freedom from groin recurrence as seen on duplex ultrasound imaging was higher in the SFL/S group (73% vs 44% in the EVLA group; P = .002), and the same trend was seen for clinically evident recurrence (77% vs 58%, respectively; P = .034). Nine reinterventions (17%) were deemed necessary in the SFL/S group vs 18 (36%) in the EVLA group (P = .059). All reinterventions in the SFL/S group consisted of foam sclerotherapy. Reinterventions in the EVLA group included foam sclerotherapy (n = 5), crossectomy (n = 2), and endovenous procedures (n = 11). There was no significant differences in quality of life and relief of venous symptoms. Cosmetic appearance improved, with a better cosmetic rating in the SFL/S group compared with the EVLA group (P = .026). One patient in the SFL/S group had a persisting neurosensory deficit remaining at 10 years. ConclusionsThis study showed no clear long-term advantage of EVLA with a 980-nm wavelength and bare-tip fiber over high ligation and stripping of the GSV under local tumescent anesthesia.

Endovenous laser coagulation: asymmetrical heat transfer and coagulation (modeling in blood plasma)

The objective of this study was to describe the dynamics of blood plasma heating and coagulation processes carried out by continuous laser radiation with wavelengths 1.55 and 1.94 μm through bare-tip fibers and fibers with radial output (radial fibers) used for endovenous laser coagulation (EVLC). The study was performed in previously thawed frozen donor blood plasma using high-speed shooting of the heating process through the shadow optical method. It has been shown that in the case of highly water-absorbed laser radiations, convection, explosive, and small-bubble boiling play a major role in the process of heat transfer and coagulation. It has been shown that in the case of radiation with wavelength λ = 1.94 μm, effective heat transfer begins at significantly lower levels of power compared to radiations with λ = 1.55 μm. It has been established that heat transfer is sharply asymmetrical and is directed mainly upwards and forwards (bare-tip fiber) or upwards (radial fibers). For a wavelength of 1.94 μm, the effect of self-cleaning of the fiber surface from coagulated plasma fragments was found. Except for short-term acts of explosive boiling, the heat transfer is asymmetrical and directed mainly upwards. This effect should lead to uneven heating and thermal damage to the vein wall with the maximum at its upper part. For EVLC, the use of radiation with a wavelength of 1.94 μm is more efficient and safer.

Endovenous laser ablation of incompetent great saphenous veins with 1470-nm laser using bare tip and radial fibers results in similar short-term outcomes

ObjectiveThe common side effects of endovenous laser ablation (EVLA) are pain and discomfort in the treated leg. We compared the pain and outcomes after EVLA using a 1470-nm laser with bare tip or radial fibers in the treatment of incompetent great saphenous veins (GSVs). MethodsA total of 86 patients with primary varicose veins of the GSV were randomized to treatment using a 1470-nm laser and bare fiber (BF; n = 43) or radial fiber (RF; n = 43) during a 12-month period from January to December 2019. Patients were assessed clinically and using venous Doppler ultrasonography at 24 hours, 1 week, and 1 month. The periprocedural parameters and short-term outcomes of pain after the procedure, improvement in the Venous Clinical Severity Score (VCSS), and vein occlusion at 1 month were compared and analyzed. ResultsThe linear endovenous energy density (65.7 J/cm vs 65.2 J/cm), tumescent local anesthetic solution used (627.4 mL vs 661.4 mL), treated GSV length, and number of hook phlebectomies were similar in both groups. The pain score at 8 hours (2.77 vs 2.70) and 1 week (2.81 vs 2.74) were similar in the BF and RF groups, respectively. The improvement in the VCSS was significant in both groups and was slightly better in the BF group, although the difference was not statistically significant. Both fiber types had 100% efficacy in terms of closure of the treated vein at 1 month. ConclusionsEVLA using a 1470-nm laser with a BF had similar outcomes in the short term compared with a RF of the same wavelength. Both fibers were associated with significant improvement in the VCSS at 1 month.

Midterm varicose vein recurrence rates after endovenous laser ablation: comparison of radial fibre and bare fibre tips.

We evaluated and compared midterm recurrence results of our patients with great saphenous vein insufficiency who were treated with a 1470-nm diode laser using 2 different types of fibre catheter kits. A total of 61 consecutive patients were treated between 2013 and 2014 with a bare fibre (BF) tip (BF group) and 60 consecutive patients were treated with a radial fibre (RF) tip (RF group) from 2014 to 2016. First-year venous clinical severity scores (VCSSs) were compared with VCSS before endovenous laser ablation and at the first-month follow-up. Patients were examined for recurrence and classified according to the system developed by Stonebridge. There was no significant difference between the 2 groups in terms of VCSS. Examination with Doppler ultrasonography showed no recurrence in the RF group, whereas recurrences were detected in 6 patients in the BF group, which was statistically significant (P = 0.028). All of the recurrences were type 1b (incompetent tributaries) varicose vein recurrences. The VCSS of the patients with recurrence were the same as the scores of patients without recurrence (0.5 ± 0.55). Varicose vein recurrence was more often seen in the BF group than in the RF group. Recanalization-induced and neovascularization-induced recurrences were not found in either group. Saphenofemoral side branch-induced recurrence was more significant in the group treated with the BF tip.

Endovenous laser coagulation: asymmetrical heat transfer (modeling in water).

The objective of this study was to describe the dynamics of water heating carried out by continuous laser radiation with wavelengths 1.47, 1.55, and 1.94 μm with different types of fibers used for endovenous laser coagulation. The study was conducted in water using high-speed surveying of the heating process through the shadow optical method. It has been shown that in the case of highly water-absorbed laser radiations, convection and boiling play a major role in the process of heat transfer. It has been shown that in the case of radiation with λ = 1.94 μm that is heavily absorbed by water, effective heat transfer begins at significantly lower levels of power compared to the weaker-absorbed radiations with λ = 1.47 and 1.55 μm. Mathematical models based only on thermal conductivity inadequately describe the process of real heat transfer during endovenous laser coagulation. It has been established that heat transfer is sharply asymmetrical and is directed mainly up-and-forward (bare-tip fiber) or upward ("radial" and "two-ring" fibers). Heat transfer for laser light with wavelength 1.94 μm is most effective than for 1.47 and 1.55 μm.

All-fiber online Raman sensor with enhancement via a Fabry-Perot cavity.

In this Letter, a novel all-fiber online Raman sensor with significant signal enhancement via a Fabry-Perot (FP) cavity is proposed and demonstrated. The FP cavity structure is formed by inserting a long-pass coated fiber and a gold-plated capillary into a silver-lined capillary with a gap. A corroded single-mode fiber is inserted into the gold-plated capillary to guide the excitation light into the FP cavity. The multiple reflections of excitation light in the FP cavity have significantly increased the interaction volume between the light and the sample. Experiment results have demonstrated an enhancement factor of 5 times in the detected Raman signal for ethanol compared to that measured using the silver-lined hollow-core fiber-based Raman cell without FP cavity, or 86 times compared with direct detection using a bare fiber tip. The measurement results are in good agreement with theoretical analyses. This Raman sensor with signal enhancement via the FP cavity has the potential to realize rapid sample replacement and online detection with high sensitivity and high accuracy for biochemical applications.

Endovenous laser ablation: A comprehensive review.

To provide an evidence-based overview of endovenous laser ablation and describe its role as an effective and durable technique for the management of superficial venous insufficiency. The published literature on the treatment of varicose veins using endovenous laser ablation was reviewed. The literature search focused on the history of endovenous laser ablation, its safety and durability, known complications, and differences in outcomes based on the iterations of fiber type and laser wavelength. Treatment safety and efficacy of endovenous laser ablation appear to be based on the amount of energy administered over a defined distance, or the linear endovenous energy density. The ideal linear endovenous energy density varies with the laser wavelength and fiber-type. Post-operative pain and bruising may be reduced by the use of higher wavelength fibers or the use of radial or jacket-tip fibers as compared to bare-tip fibers. The incidence of endothermal heat-induced thrombosis remains low and has declined with increasing experience. Reports have demonstrated a greater than 90% technical success rate with saphenous endovenous laser ablation, long-term durability of ablation, and commensurate improvement in quality of life. Endovenous laser ablation is a safe and durable treatment option for the management of incompetent superficial and perforator veins of the lower extremities. As an endothermal technology, it remains a key component of the standard of care for the treatment of chronic venous insufficiency.

Patency of Anterior Accessory Saphenous Vein Following Endovenous Laser Ablation for Varicose Veins: Bare-Tip Versus Radial Fiber

Introduction - Anterior accessory saphenous vein (AASV) insufficiency is one of the most common causes of late recurrence after endovenous laser ablation (EVLA) for great saphenous vein (GSV) insufficiency1)2). Therefore, reduction of the AASV patency rate after EVLA can be associated with better long-term results. The aim of this study is to compare the patency rate of saphenofemoral junction tributaries after EVLA between bare-tip and radial fibers. Methods - We reviewed 375 limbs in 339 patients undergoing EVLA for GSV insufficiency. The bare-tip fiber with a 980-nm diode laser was used in 299 limbs (group B). The radial fiber with a 1470-nm diode laser was used in 76 limbs (group R). Concomitant ablation of AASV or high ligation of GSV was not included in this study. Patients who had previous EVLA, high ligation and stripping were excluded. Duplex ultrasound scanning was performed 3 months after EVLA to assess occlusion of the ablated GSV and patency of the saphenofemoral junction tributaries including the AASV, the posterior accessory saphenous vein (PASV) and the superficial epigastric vein (SEV) in both groups. Student-t tests and chi square tests were used to compare two groups. Results - The total occlusion rate of the ablated GSV at 3 months after EVLA was 100% in group R and 99% in group B, p = 0.999. The patent AASV was detected significantly (p = 0.004) less in group R (33 limbs, 43%) than in group B (184 limbs, 62%), whereas the PASV patency rate was similar (p = 0.815) in both groups (16% in group R, 15% in group B, p = 0.815). The SEV occlusion rate was 4% in group R and 1% in group B, p=0.101. There was no difference in age, gender, body mass index, CEAP classification and the proximal GSV diameter in both groups. Laser power was smaller in group R (8.9 +/- 0.9 W) than in group B (9.4 +/- 0.6 W), p < 0.001, however, linear endovenous energy density did not differ between the groups (79.9 +/- 13.6 J/cm in group R, 78.3 +/- 9.2 J/cm in group B, p = 0.198). The distance between the tip of the fiber and the common femoral vein was shorter in group R (9.7 +/- 2.4 mm) than in group B (17.5 +/- 4.9 mm), p < 0.001. Conclusion - EVLA using a radial fiber archived better occlusion rates of AASV. This result can be attributed to the position of the laser fiber tip closer to the saphenofemoral junction. Our study suggests that EVLA using a radial fiber will reduce the risk of late recurrence caused by AASV insufficiency in the treatment of GSV varicose veins. References1)J Vasc Surg. 2016; 63: 420-428.2)Eur J Vasc Endovasc Surg. 2011; 41: 685-690.

Volumetric enhancement of Raman scattering for fast detection based on a silver-lined hollow-core fiber.

Fast detection and identification of chemicals are of utmost importance for field testing and real-time monitoring in many fields. Raman spectroscopy is the predominant technique in principle, but its wide application is limited on account of weak scattering efficiency. Surface Enhanced Raman Spectroscopy (SERS) technique provides a solution for signal enhancement, but may not good at fast detection due to cross contamination and bulky instruments. Hollow-core fiber-based Raman cell with long interaction length can achieve high detection sensitivity, but it also suffers from low flow rate, bulky high-pressure equipment and light coupling structure, which also restricts its application for fast detection. In order to solve those problems, we proposed a portable Raman cell, by using metal-lined hollow-core fibers (MLHCF) with large bandwidth, good field confinement, extremely large numerical aperture and arbitrary length. With our proposed fiber inserted light coupling and light reflecting method, a Raman cell of 3.1 cm in length provides nearly 50 times of signal enhancement compared with direct detection using bare fiber tip. Furthermore, the sample exchange rate could be as fast as 1 second even under normal pressure without any cross contamination. At last, we also demonstrated the underlying general mechanism of signal enhancement and summarized it as volumetric enhancement of Raman scattering (VERS). Both the experiment results and the theoretical analysis demonstrated that our device has the potential for fast online Raman detection, which also possesses high-sensitivity and high-accuracy.

The bactericidal effect of continuous wave laser with strongly absorbing coating at the fiber tip

The bactericidal effect of laser radiation with a quartz fiber-based transmission system with a strong absorption coating converter against bacteria associated with urological stones has been studied. Gram-negative rod Escherichia coli and the Gram-positive coccus Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium were used in this study. Each bacterial species was treated by continuous-wave near infrared laser coupled with bare fiber tip or strongly absorption coating fiber tip. After treatment, the temperature of bacterial suspension was measured. In addition, the temperature distribution was analyzed. It has been shown that using laser with a strongly absorption coating fiber tip results in significant bactericidal effect. The decrease of the amount of E. coli and S. epidermidis was 100% after treatment with an output power of 6[Formula: see text]W of radiation at a wavelength of 0.97[Formula: see text][Formula: see text]m for 40[Formula: see text]s. Number of S. aureus and Ent. faecium colony-forming unit was reduced to 70% after same exposure. The peak temperature of bacterial suspension was [Formula: see text]C after treatment by laser with a strongly absorption coating fiber tip. Laser with a strongly absorption coating fiber tip provides large-scale hydrodynamic flows directed away from the fiber tip. The laser with a strongly absorption coating fiber tip has bactericidal effect. The main role is associated with the effect of high temperature, which, in the form of flow in a liquid medium, affects bacteria.

Thulium fiber laser-induced vapor bubble dynamics using bare, tapered, ball, hollow steel, and muzzle brake fiber optic tips

This study characterizes laser-induced vapor bubble dynamics for five different distal fiber optic tip configurations, to provide insight into stone retropulsion commonly experienced during laser ablation of kidney stones. A thulium fiber laser with 1908-nm wavelength delivered 34-mJ energy per pulse at 500-μs pulse duration through five different fibers such as 100-μm-core / 170-μm-OD bare fiber tip, 150- to 300-μm-core tapered fiber tip, 100-μm-core / 300-μm-OD ball tip fiber, 100-μm-core / 340-μm-OD hollow steel tip fiber, and 100-μm-core / 560-μm-OD muzzle brake fiber tip. A high-speed camera with 10-μm-spatial and 9.5-μs-temporal resolution was used to image the vapor bubble dynamics. A needle hydrophone measured pressure transients in the forward (0 deg) and side (90 deg) directions while placed at a 6.8 ± 0.4 mm distance from the distal fiber tip. Maximum bubble dimensions (width/length) averaged 0.7/1.5, 1.0/1.6, 0.5/1.1, 0.8/1.9, and 0.7 / 1.5 mm, for bare, tapered, ball, hollow steel, and muzzle brake fiber tips, respectively (n = 5). The hollow steel tip exhibited the most elongated vapor bubble shape, translating into increased forward pressure in this study and consistent with higher stone retropulsion in previous reports. Relative pressures (a.u.) in (forward/side) directions averaged 1.7/1.6, 2.0/2.0, 1.4/1.2, 6.8/1.1, and 0.3/1.2, for each fiber tip (n = 5). For the hollow steel tip, forward pressure was 4 × higher than for the bare fiber. For the muzzle brake fiber tip, forward pressure was 5 × lower than the bare fiber. Bubble dimensions and pressure measurements demonstrated that the muzzle brake fiber tip reduced forward pressure by partially venting vapors through the portholes, which is consistent with the observation of lower stone retropulsion in previous reports.

More Successful Results with Less Energy in Endovenous Laser Ablation Treatment: Long-term Comparison of Bare-tip Fiber 980 nm Laser and Radial-tip Fiber 1470 nm Laser Application

Varices and venous insufficiency are common and serious health problems in the general population which affect the quality of life. Endothermal treatment of the great saphenous vein has become the first line of treatment for superficial venous reflux, and the endovenous laser ablation (EVLA) method has been widely accepted all over the world. In this method, ablation is provided by a laser fiber inserted into the lumen of the vein. Initially, the fibers were 810nm, but today the fibers are usually 940, 980, or 1470nm. The study included 400 patients (419 procedures) who were diagnosed with venous insufficiency and underwent 980 and 1470nm EVLA. Patients were followed up for 48months. A 980-nm bare-tip laser catheter in Group A and a 1470-nm radial-tip laser catheter in Group B were inserted until they were 2cm below the saphenofemoral junction. An EVLA catheter was drawn slowly at the rate of 1-3 cm/sec (2.08±0.6). The energy applied to the saphenous vein was 60-120J/cm (84.65±13.03) and 45-120J/cm (76.95±15.06) in Group A and Group B, respectively (P<0.001), with 15W in the continuous mode. Follow-up visits included a physical examination and Doppler ultrasonography performed at the following time points: day 1, week 1, and months 1, 6, 12, 24, 36, and 48. Saphenous vein occlusion rates and postprocedure saphenous vein diameters were evaluated at each follow-up visit. Pain levels were evaluated using the Wong-Baker FACES® pain scale (0-10). Postoperative complications were recorded. Group A (980nm laser) consisted of 200 patients with a mean age of 37.84±12.2years. Group B (1470nm laser) consisted of 200 patients with a mean age of 38.38±12.1years. The mean duration of the procedure was 32.2±9.7min in Group A and 31.7±8.8min in Group B, respectively (P=0.47). Induration, ecchymosis, and paresthesia rates were significantly higher in the bare-tip laser group. The most important complication, deep vein thrombosis, was observed in 4 patients in Group A. Recanalization rates were found to be increased by prolonged follow-up periods. At the 48-month follow-up, this rate was 15.9% in Group A and 8.3% in Group B (P=0.017). This rate showed that the 1470-nm wavelength laser treatment was more successful in Group B than in Group A over the long term. Both the 980 and 1470nm wavelength laser-assisted EVLA procedures appear to be effective in treating saphenous vein insufficiency. The 1470-nm radial-tip fiber is preferred due to lower energy levels, lower complication rates, early return to daily life, and the successful long-term occlusion rate.

Moving heat source in a confined channel: Heat transfer and boiling in endovenous laser ablation of varicose veins

Motion of a moving laser light heat source in a confined volume has important applications such as in endovenous laser ablation (EVLA) of varicose veins. This light heats up the fluid and the wall volume by absorption and heat conduction. The present study compares the flow and temperature fields in a horizontal tube of 4mm inner diameter in three idealizations of the EVLA procedure: water with a bare fiber tip, water with a carbonized layer on the fiber tip, and blood. Without boiling, the convection patterns in water and blood are similar and Grashof numbers are high enough to guarantee buoyancy induced flow and axial mixing, while preserving some stratification. A carbonized layer at the fiber tip promotes boiling in water at moderate laser powers. Boiling bubbles in water rapidly detach from the tip, with or without a carbonized layer, and promote mixing and a locally homogeneous temperature field. At 15W laser power and 4mm/s pullback speed in blood, a gas bubble may be formed that sticks at the fiber tip, causing strong local heating and possibly fiber damage.

Bare Tip versus Radial Endovenous Laser Ablation for the Treatment of Primary Varicose Veins

Background: New modalities in the Endo Venous Laser Ablation (EVLA) include the new design of the laser catheter tip is claimed to distribute more effectively the laser beam to the targeted varicose vein (VV) wall and therefore to achieve better results and produce fewer complications. These favorable results support the previously suggested better outcome of the EVLA compared to the open procedure. Aim: This study was conducted to confirm this assumption. Patients and Methods: 81 patients scheduled for treatment of VV were included and were divided into 3 equal groups. EVLA was used with a bare tip fiber for the first group and compared to a second group treated with a radial fiber. The success rate and postoperative results of both groups were compared to each other, then the mean results of EVLA group as a whole were compared to a third control group treated by surgical stripping. Results: There was no statistically significant difference between both EVLA groups. One patient (3.7%), from the bare tip group, had incomplete ablation that necessitated surgical excision. Fewer complications, shorter hospital stay, early return to work, and faster reduction in venous clinical severity score (VCSS) were noted among the EVLA compared to the open group. Conclusion: EVLA using bar tip or radial fibers is effective and safe in treating vv with similar results. Their results are as effective as the open procedure with a shorter hospital stay, fewer complications, and early return to work.

Fiber type as compared to wavelength may contribute more to improving postoperative recovery following endovenous laser ablation.

To define the relative importance of fiber type as compared to laser wavelength on tissue injury depth, postoperative pain, and bruising during endovenous laser ablation. This study included 213 limbs that were treated with an 810-, 980-, or 1470-nm laser, with bare-tip (BT) or jacket-tip (JT) fibers. Pain scores (10-point scale) and bruising scores (5-point scale) were recorded. Tissue thermal injury depth (mm) was evaluated invitro for the 810- and 1470-nm wavelengths with BT and JT fibers. The JT fibers had lower pain scores as compared to the BT fibers at 810nm (1.69± 1.77 vs 3.70± 1.34; P<.0005) and at 980nm (1.14± 1.06 vs 2.71± 1.80; P<.0005). The JTfibers had lower bruising scores as compared to the BT fibersat 980nm (0.89± 1.06 vs 2.00± 1.44; P<.0005). The invitro study showed lower thermal injury depths for the JT ascompared to the BT fibers at 810nm (0.36mm± 0.26mm vs 1.05mm± 0.34mm; P<.0005) and at 1470nm (0.20± 0.16mm vs 0.71± 0.31mm; P<.0005). With regard to wavelength, 980-nm laser had lower pain scores as compared to 810-nm laser withBT fibers (2.71± 1.80 vs 3.70± 1.34; P= .015), andwith JT fibers, a similar result trended toward significance (1.14± 1.06 vs 1.69± 1.77; P= .057). The 980-nm JT fibershowed less bruising as compared to the 810-nm JT fiber (0.89± 1.06 vs 1.42± 1.19; P= .019). Similarly, the 1470-nm JT fiber showed less bruising as compared to the 810-nm JT fiber (0.94± 1.02 vs 1.42± 1.19; P= .038). The invitro study showed thermal injury depths that were less for 1470 nm as compared to 810nm, with JT fibers (0.20± 0.16mm vs 0.36± 0.26mm; P= .013) or with BT fibers (0.71± 0.31mm vs 1.05± 0.34mm; P=.001). All mean differences between JTand BTfibers were greater than between differing wavelengths. The multivariate analysis for the invitro study showed a meandifference between 1470 nm and 810 nm of 0.26mm, P<.0005 favoring 1470 nm and a mean difference between JTand BT fibers of 0.61mm, P<.0005 favoring the JT fibers. The use of a JT fiber appeared to be more significant in reducing pain and bruising as compared to a longer wavelength. Moreover, the results appeared additive, and thecohort using 1470 nm with a JT fiber produced thebest treatment outcomes. Additional study is required toconfirm the efficacy and durability of the various iterations evaluated; however, these data should be taken into consideration when undertaking treatment with endovenous laser ablation.

Photothermal ablation of liver tissue with 1940-nm thulium fiber laser: anex vivostudy on lamb liver

The purpose of this study was to investigate the ablation efficiency of 1940-nm thulium fiber laser on liver tissue, while utilizing a real-time measurement system to monitor the temperature rise in adjacent tissues. Thulium fiber laser was delivered to lamb liver tissue samples via 400-μm bare tip fiber in contact mode. Eight different laser parameter combinations [power, continuous-wave (cw)/pulsed-modulated (pm) mode, and exposure time] were used. Exposure times were chosen to give the same total applied energy of 4 J for comparative purposes. Following laser irradiations, tissues were processed and stained with hematoxylin and eosin for macroscopic evaluation of ablation areas and total altered areas, and ablation efficiencies were calculated. Temperature of the nearby tissue at a distance of 1 mm from the fiber was measured, and rate of temperature change was calculated. A strong correlation between the rate of temperature change and ablation area was noted. Thermal effects increased with increasing power for both modes. The continuous-wave mode yielded higher ablation efficiencies than the pulse-modulated mode. Histological evaluation revealed a narrow vacuolization zone and negligible carbonization for higher-power values.