Endovenous laser therapy--application studies and latest investigations

Comparison between contact diode laser with 980 nm and 1470 nm wavelengths for posterior laryngofissure in pigs

To compare two different wavelengths of the surgical contact diode laser (CDL) for producing a posterior laryngofissure in in-vivo pigs. Anesthetized pigs underwent a tracheostomy and an anterior laryngofissure through a cervicotomy. They were randomly selected for the CDL wavelength and Power, according to the peak of Power set at device (980nm wavelength: Ppeak power of 10 W, 15 W, and 20 W, or 1470 nm wavelength: Ppeak 3 W, 5 W, 7 W, 10 W). At the end of the experiment, the laryngotracheal specimen was extracted and sent for histology and morphometry measurements (incision size, depth, area, and lateral thermal damage). Hemodynamic data and arterial blood gases were recorded during the incisions. Statistical analysis of the comparisons between the parameters and groups had a level of significance of p < 0.05. Twenty-six pigs were divided into CDL 980 nm (n = 11) and 1470 nm (n = 15). There was a greater incision area at the thyroid level in the 980 nm CDL and a wider incision at the trachea level, with a larger distance between mucosa borders. There were no significant differences in the area of lateral thermal damage between the two groups and neither difference among the power levels tested. Both wavelengths tested showed similar results in the various combinations of power levels without significant differences in the lateral thermal damage. The posterior laryngofissure incision can be performed by either of the wavelengths at low and medium power levels without great difference on lateral thermal damage.

Durability and efficacy of the ELVeS® Radial® 2ring slim fiber for multiple ablations

OBJECTIVES

To prove that the ELVeS® Radial® 2ring slim fiber (Biolitec AG, Wien, Austria) is safe and effective, with a reliable fiber durability.

METHODS

This prospective, non-randomized, registry recruited patients with venous incompetence of the great saphenous vein, with or without concomitant incompetence of the small, anterior accessory and posterior accessory saphenous veins. Anatomic success, clinical success and pain were assessed.

RESULTS

150 patients (410 veins) underwent endovenous laser ablation (EVLA). Mean number of veins treated was 2.7 (1-7) with a mean total length of 80.7 cm. 98.3% occlusions were observed after 12 months. Clinical improvement was significant with reduced venous clinical severity scores at 1 month (1.7 ±1.9; p < .0001) and 12 months (0.7 ±1.3; p < .0001) versus pre-operation (4.4 ± 2.2). Mean pain level after 1-week was 5.8/100. No major surgery- or device-related complications occurred.

CONCLUSIONS

1470-nm EVLA with the 2ring slim fiber is a highly effective treatment option well tolerated by patients. Despite intensive use, fiber integrity was preserved.

CLINICAL REGISTRATION

The study protocol was registered in clinicaltrials.gov (NCT03810677).

No More Venous Ulcers-What More Can We Do?

Venous leg ulcers (VLUs) are the most severe complication caused by the progression of chronic venous insufficiency. They account for approximately 70-90% of all chronic leg ulcers (CLUs). A total of 1% of the Western population will suffer at some time in their lives from a VLU. Furthermore, most CLUs are VLUs, defined as chronic leg wounds that show no tendency to heal after three months of appropriate treatment or are still not fully healed at 12 months. The essential feature of VLUs is their recurrence. VLUs also significantly impact quality of life and could cause social isolation and depression. They also have a significant avoidable economic burden. It is estimated that the treatment of venous ulceration accounts for around 3% of the total expenditure on healthcare. A VLU-free world is a highly desirable aim but could be challenging to achieve with the current knowledge of the pathophysiology and diagnostic and therapeutical protocols. To decrease the incidence of VLUs, the long-term goal must be to identify high-risk patients at an early stage of chronic venous disease and initiate appropriate preventive measures. This review discusses the epidemiology, socioeconomic burden, pathophysiology, diagnosis, modes of conservative and invasive treatment, and prevention of VLUs.

Prospects of Endovenous Laser Ablation (EVLA) Standardization-Mid-Term Results of a Four-Zone Dosimetry Guiding Tool for 1940 nm Laser

BACKGROUND

Heterogeneity regarding dosimetry and reporting of endovenous laser ablation (EVLA) mandates the development of a standardized protocol. This study presents the mid-term results of EVLA with 1940 nm-laser and radial-fibre, supported by a four-zone dosimetry tool.

MATERIALS AND METHODS

Four anatomical dosimetry zones for great saphenous veins (GSV) and two for small saphenous veins (SSV) were defined with set power levels. Zone-1G (4 W) extended from the inguinal ligament to the apex of femoral triangle, Zone-2G (4 W) from the apex of femoral triangle to the upper border of patella. Zone-3G (3 W) from the patella to the tibial tuberosity. Zone-4G (2 W) extended from the tibial tuberosity to the ankle. Zone-1S from the sapheno-popliteal junction to the tibial tuberosity. Zone-2S from the tibial tuberosity to the ankle. Power was increased by 1 W for veins >10 mm and decreased by 1 W when fibre sticking was encountered. Pullback-velocity was max. 1 mm/s.

RESULTS

A total of 152 consecutive patients (185 procedures) were recruited. Mean follow-up time was 11.9 months. Mean linear endovenous energy density for GSV was Zone-1G:42 J/cm, Zone-2G:33 J/cm, Zone-3G:27 J/cm, Zone-4G:22 J/cm, Zone-1S:34 J/cm, Zone-2S:27 J/cm. Occlusion rates were 98.9% (1-month) and 93.7% (12-months). Complications at 1 M were low, namely laser-induced paraesthesia (LIP) 2.2% and endovenous heat-induced thrombosis (EHIT) 1.6%. Persistent LIP (12 M) was observed in 0.5%.

CONCLUSION

The proposed four-zone guiding tool is a step towards standardizing dosimetry and documentation for EVLA with 1940 nm. This strategy shows good mid-term results with minimal complications. Long-term follow-up and application in further centres are necessary to prove its reproducibility. Such a guiding tool could improve the ability to analyse, compare and review different EVLA wavelengths and fibre types.

Endovenous laser ablation using laser systems emitting at wavelengths > 1900 nm: a systematic review

The aim of this systematic review was to summarize the currently available literature reporting clinical application of endovenous laser ablation (EVLA) by means of laser systems emitting at wavelengths > 1900 nm, pertaining dosimetry, intraoperative parameters, postoperative outcomes, and efficacy based on occlusion rates, recanalization, and postoperative complications. A literature search was conducted in PubMed, Cochrane Library, Embase, OVID, and Web of Science for publications since the year 2000 until December 2021. Case series, prospective trials, retrospective studies, and randomized controlled trials describing the application of a 1920/1940-nm wavelength laser for EVLA in humans with a minimum of one postoperative follow-up visit were included in the study. Four case series and one randomized controlled trial with a total of 509 EVLA procedures (396 great saphenous veins and 113 small saphenous veins) were identified, meeting the inclusion criteria. The studies were heterogenous in their documentation, EVLA, and duplex ultrasound protocol and result reporting. Overall, the applied average cumulative LEED values ranged from 17.8 to 53 J/cm. Complications observed were pigmentation (0-9.75%), paresthesia (2.5-7.3%), thrombophlebitis (0-5%), EHIT Class 2 (2.26-2.4%), and EHIT Class 1 (1.2-2.4%). Four cases of recanalizations were observed in one study cohort within the first month after treatment. Follow-up at 12 months was available for 3 studies (procedures n = 218) with recanalizations in 8 limbs. Follow-up at 24-36 months was available for 2 studies (procedures n = 126) showing recanalizations in 5 limbs. Recanalizations were asymptomatic and incidental findings on follow-up duplex ultrasound. Pooled occlusion rates were 99.2% at 1 M, 96.3% at 12 M, and 96% at 24 M. Overall, patients undergoing EVLA with long wavelength laser systems > 1900 nm show high occlusion rates, significant improvement in VCSS, low postoperative complication rate, low pain levels, low analgesic requirement, and early convalescence. Apart from persistent paresthesia, all the complications regressed spontaneously within 6 months. EVLA by means of 1920/1940 nm shows promising clinical results with high efficacy and low complication rates. Heterogeneity still exists regarding ideal protocol for duplex ultrasound examination and documentation of anatomical parameters (e.g., vein diameter, ideal stump length and status of accessory veins) and light dosimetry for EVLA.

Safety and efficacy of endovenous laser ablation (EVLA) using 1940 nm and radial emitting fiber: 3-year results of a prospective, non-randomized study and comparison with 1470 nm

OBJECTIVES

To evaluate the safety, efficacy and ≥36 months outcomes of endovenous laser ablation (EVLA) by means of 1940 nm laser with radial fiber for the treatment of truncal vein insufficiency and compare the results to a historical cohort, obtained via reviewing the literature.

METHODS

This prospective, non-randomized, single-center clinical study included 139 consecutive patients with 177 incompetent great saphenous (GSV, n = 135) and short saphenous veins (SSV, n = 42). The maximum laser power (Pmax. 10 W) and pullback velocity were adjusted individually (V_max  = 1 mm/s). The laser fiber was placed at the junction to the deep vein under duplex monitoring. Simultaneous phlebectomies were performed on all the patients. Regular follow up with clinical and duplex ultrasound examination (DUS) were carried out postoperatively at 1 month (1 M), 6 months (6 M), 12 months (12 M), 24 months (24 M), 36 months, and after that (≥36 M). The results were compared with three cohorts (total 616 EVLA procedures with 1470 nm laser and radial fiber) from literature (criteria: >100 procedures, follow-up of ≥2 years).

RESULTS

The follow-up rate was 100%, 91%, 73%, 48%, and 23% of the truncal veins at 1, 6, 12, 24, and ≥36 M, respectively. In comparison to the literature using 1470, a lower average linear endovenous energy density (LEED) (53 vs. 77-82 J/cm) resulted in 100% (6 M) and 96.5% (24 M) occlusion rates, reduced local ecchymosis (2.2% vs. 3.2%-18.7%) and reduced average postoperative pain levels (1.3 vs. 2.18). Regarding adverse events, induration (1.1% vs. 1.8%), skin burns (0% vs. 0.45%), endovenous heat-induced thrombus propagation (EHIT) in the deep veins (2.3% vs. 1.8%) and laser-induced persistent paresthesia (2.2% vs. 0.5%-2.9%) were comparable. Recanalizations observed in this study (GSV 0, SSV 3) were asymptomatic and required no treatment. At ≥36 M reflux in the accessory veins was observed in 5% versus 10.5% of patients. Reintervention was required in none (0% vs. 21%). At >36 M, short average stump lengths of 1 cm (GSV) and 0.3 cm (SSV) were observed.

CONCLUSION

EVLA with 1940 nm laser with radial emitting fiber is as safe and effective as 1470 nm laser for the treatment of truncal vein insufficiency. Lower postoperative pain, low analgesic requirements, short convalescence add to patients' comfort. EVLA with 1940 nm laser-guided by intraoperative DUS permits reproducible placement of the radial fiber at the saphenofemoral and saphenopopliteal junction, enabling further studies to assess the effect of shorter stump length on patterns and frequency of recurrence without increased risk of EHIT.

Endovenous (minimally invasive) procedures for treatment of varicose veins : The gentle and effective alternative to high ligation and stripping operations

Thermal ablation of saphenous vein varicosis has developed into a standard procedure for treatment of varicose veins. The clinical success of the endovenous thermal procedure is comparable to high ligation and stripping operations and a significant difference between these groups could not be detected in long-term analyses. The only difference is in the genesis of saphenofemoral recurrence detected by duplex ultrasound: neoangiogenesis occurs after high ligation and stripping operation and after endovenous ablation of the great saphenous vein a recurrence occurs predominantly via a residual anterior accessory saphenous vein (AASV). Reduction of costs by an increase in endovenous procedures carried out in an outpatient setting in comparison to stripping operations, which are still frequently carried out in Germany (in comparison to other countries) as an inpatient procedure, have meanwhile been confirmed. An endovenous crossectomy (i.e., high ligation) should be strived for. Nonthermal endoluminal catheter procedures are predominantly reserved for treatment of the short saphenous vein.

Homogeneously Emitting, Mechanically Stable, and Efficient fs-Laser-Machined Fiber Diffusers for Medical Applications

BACKGROUND AND OBJECTIVES

Light delivery is an essential part of therapy forms like photodynamic therapy (PDT), laser-induced thermotherapy, and endovenous laser therapy. While there are approaches to the light application for all three therapies, there is no diffuser that can be used for all three approaches. This diffuser must meet the following criteria: Homogeneous radiation profile over a length of 40 mm, efficient light extraction in the diffuser area, mechanical breakage resistance as well as thermal stability when applying high power.

STUDY DESIGN/MATERIALS AND METHODS

An ultrashort pulse laser was used to inscribe inhomogeneities into the core of a fused-silica fiber core while scanning the laser focus within a linear arrangement of cuboids centered around the fiber axis. The manufactured diffuser was optically and mechanically characterized and examined to determine the maximum power that can be applied in a tissue environment.

RESULTS

Based on the analysis of all examined diffusers, the manufactured diffuser exhibits an emission efficiency ε = (81.5 ± 5.9)%, an intensity variability of (19 ± 5)% between distal and proximal diffuser end, and a minimum bending radius R_b = (15.4 ± 1.5) mm. It was taken advantage of the fact that the outer areas of the fiber core do not undergo any structural changes due to the machining and therefore do not suffer a major loss of stability. Tissue experiments revealed that a maximal power of 15 W was deliverable from the diffuser without harming the diffuser itself.

CONCLUSIONS

It could be shown that a diffuser manufactured by ultrafast-laser processing can be used for low power applications as well as for high power applications. Further tests have to show whether the mechanical stability is still maintained after the application of high power in a tissue environment. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

[Endovenous (minimally invasive) procedures for treatment of varicose veins : The gentle and effective alternative to high ligation and stripping operations]

Thermal ablation of saphenous vein varicosis has developed into a standard procedure for treatment of varicose veins. The clinical success of the endovenous thermal procedure is comparable to high ligation and stripping operations and a significant difference between these groups could not be detected in long-term analyses. The only difference is in the genesis of saphenofemoral recurrence detected by duplex ultrasound: neoangiogenesis occurs after high ligation and stripping operation and after endovenous ablation of the great saphenous vein a recurrence occurs predominantly via a residual anterior accessory saphenous vein (AASV). Reduction of costs by an increase in endovenous procedures carried out in an outpatient setting in comparison to stripping operations, which are still frequently carried out in Germany (in comparison to other countries) as an inpatient procedure, have meanwhile been confirmed. An endovenous crossectomy (i.e. high ligation) should be strived for. Nonthermal endoluminal catheter procedures are predominantly reserved for treatment of the short saphenous vein.

Effect of spatial light distribution on the thermal response of vascular tissue

The aim of the current study is to investigate the effect of radial and cylindrical light distributions on the response of vascular tissue during 1470-nm irradiation in ex vivo models. Due to a low irradiance (5.3 W/cm²) and wide light distribution, cylindrically diffusing irradiation yielded uniform thermal coagulation while radial irradiation accompanied delamination of layers in leporine veins. Bovine foot model testing verified that the diffusing irradiation was associated with the steady maximum temperature and no tissue attachment, compared with the radial irradiation. The proposed cylindrical light application can be a feasible way to treat varicose veins in an effective manner.

Endovenous Laser Application

Introduction: Endoluminal vein treatment is a promising minimal invasive treatment option for peoples suffering from varicose veins. The basic mechanism underlying this procedure is to selectively induce heat in the vessel wall with the result of denaturation of proteins and shrinkage of collagen fibers due to energy application. So far energy could be applied either as RF-current, laser light or water steam. The different approaches to deliver such forms of energies are described.

Methods: Investigations on heat dependent vein tissue effects were performed. The degree of shrinkage and wall thickening due to heat induction was calculated. Tensile test on vein tissue were performed. Investigation using the radial emitting laser fibre in the ox-foot-model under reproducible condition were done and wavelengths dependent tissue reaction were explored.

Results: The experiments clearly demonstrate the degree of the shrinkage of length and diameter, the thickening of the vein wall, as well as the decrease of the elasticity of the tissue. The optical irradiation pattern of the radial emitting laser fiber serves for safe and reproducible energy application directly to the vein wall. Using a laser wavelength with high absorption by the tissue water needs reduced irradiation and irradiance compared to wavelengths with less water absorption. Conclusion: An experimental approach to improve laser application for endovenous varicose treatment is described. Laser parameters and treatment parameters were found which are now under clinical testing. The demonstrated tissue effects may help to find further arguments for clinical findings and sensations described by the patients during follow-up.

Concentric photothermal coagulation with basket-integrated optical device for treatment of tracheal stenosis

A basket-integrated optical device is developed to consistently treat tubular tissue by centering an optical diffuser in the lumen. Four nitinol arms in conjunction with the optical diffusing applicator are deployed to induce homogeneous circumferential light emission and concentric photothermal coagulation on tracheal tissue. A 1470-nm laser light is employed for the tissue testing at various irradiation conditions and evaluated in terms of thermal gradient and temperature evolution. Preliminary experiments on liver tissue demonstrate the concentric development of the radial thermal coagulation in the tissue (eccentric ratio = ~5.5%). The interstitial tissue temperature increases with the total amount of energy delivery (around 65°C). Ex vivo trachea testing yields up to 16.5% tissue shrinkage due to dehydration as well as uniform ablation of the cilia and goblet cells in a mucosa layer under 7-W irradiation for 10 s. The proposed optical device may be a feasible therapeutic method to entail the circumferential coagulation in the tubular tissues in a reliable manner.

Evaluation of Endovenous Laser Ablation for Varicose Veins Using a Computer Simulation Model (Secondary publication)

Background and aims

Endovenous laser ablation (EVLA) has been well-reported as a minimally invasive method to deal with varices of the lower extremities. The lasers used fall into two categories: pigment, i.e., hemoglobin-specific lasers in the visible and near-infrared (near-IR) wavebands and longer wavelength mid-infrared lasers where the chromophore is water. The fiber used to deliver the laser energy is also important, and not enough attention has been paid to this element of EVLA. The present study was therefore designed to compare EVLA delivered through two specific fiber types coupled with a near-IR laser wavelength where water was the major chromophore.

Materials and methods

A laser diode system at the wavelength of 1470 nm was used as the laser energy source near a peak in the water absorption spectrum. Laser energy was delivered with two specific types of optical fiber, a Radial™ fiber and a Radial 2ring™ fiber (CeramOptec, Germany), and EVLA was evaluated using a computer simulation model taking light transport into account based on the Monte Carlo method and temperature distribution with the heat conduction equation.

Results and conclusions

It was confirmed from both the simulation model and a previously published ex vivo experiment that carbonization and sticking during EVLA caused by excess temperature rise can be minimized by using the Radial 2ring fiber compared with the Radial fiber, coupled with the 1470 nm wavelength. In the future, lasers with different wavelengths or optical fibers with differing irradiation modes may appear as candidate systems for EVLA. It is important to evaluate safety and efficacy carefully using the methods in the present study before moving to in vivo indications in human subjects.

Endoluminal application of glass-capped diffuser for ex vivo endovenous photocoagulation

Endovenous laser ablation (EVLA) has frequently been used to treat varicose veins for 20 years. In spite of 90˜95% occlusion rates, clinical complications such as burn and ecchymosis still occur due to excessive thermal injury to perivenous tissue. In the current study, a glass-capped diffusing applicator is designed to validate the feasibility of EVLA as an effective therapeutic device by applying circumferential light distribution. The proposed device is evaluated with a flat fiber as a reference in terms of temperature elevation, fiber degradation, and degree of coagulative necrosis after 532 nm-assisted EVLA at 100 J/cm. The diffusing fiber generates a 40% lower maximum temperature with a 90% lower transient temperature change in blood, compared to the flat fiber. Due to low irradiance (13.5 kW/cm² ) and wide light distribution, the diffuser tip experiences no significant thermal degradation while severe carbonization occurs at the flat fiber tip. Ex vivo tissue tests verify that the diffusing fiber induces circumferential and consistent tissue denaturation to the vein wall (107.8 ± 7.8 µm) along with 19% vessel shrinkage. The proposed glass-capped diffusing applicator can be a feasible therapeutic device for EVLA with minimal complications by entailing low maximum temperatures and uniform tissue denaturation in the venous tissue.

[Endovenous ablation versus open surgery for varicose veins : An attempt at an evaluation]

Open and endovenous surgery of varicose veins provides an excellent way to treat varicose veins. However, there are great differences in the how the techniques are performed. No matter which procedure is carried out, there are standards that should be observed. The state of the art of open venous surgery with radical crossectomy is well-known, but unfortunately is still not always performed correctly nowadays. The state of the art of endovenous surgery has unfortunately not yet been sufficiently documented, but should be based on open-surgical techniques. How the standard of both methods today is (or should be) is described in detail in this work. A recurrence definition which applies to both techniques, is set up.

Investigation of endovenous laser ablation of varicose veins in vitro using 1.885-μm laser radiation

This paper presents the results of endovenous laser ablation (EVLA) of varicose veins in vitro using radiation of a solid-state laser based on the crystal LiYF4:Tm, with a wavelength of 1.885 μm and power output of around 3 W. An experimental series with saline solution and red blood cell (RBC) suspension in the venous lumen was performed to identify the impact of a heated carbonized layer precipitated on the fiber end face versus the efficiency of EVLA. Results of these experiments confirmed that the presence of a heated carbonized layer on the fiber end face increases the efficiency of EVLA.

Comparison of 1470 nm Laser and Radial 2ring Fiber with 980 nm Laser and Bare-Tip Fiber in Endovenous Laser Ablation of Saphenous Varicose Veins: A Multicenter, Prospective, Randomized, Non-Blind Study

OBJECTIVE

The aim of this study is to compare the clinical efficacy and safety of two laser wavelengths and fiber types in endovenous laser ablation (EVLA) of saphenous varicose veins of the lower limb.

DESIGN

Multi-center prospective randomized non-blind clinical trial.

PATIENTS AND METHODS

From January 2007 to December 2011, 113 patients (113 limbs) with primary varicose veins were randomized into two groups. They were treated with radial 2ring fiber and 1470 nm laser in Group I (57 limbs) and bare-tip fiber and 980 nm laser in Group E (56 limbs) in order to ablate the saphenous vein. Vein occlusion rates at 12 weeks and pain in treated region were recorded as primary endpoint. Visual analogue scale (VAS) for assessment of pain, rates of bruising, complications and equipment failure were recorded as secondary endpoint of safety.

RESULTS

Occlusion rates at 12 weeks were 100% in both groups. Rates of pain (0% vs. 25.0%) and bruising (7.0% vs. 57.1%) were significantly lower in Group I (p <0.0001). VAS of pain was significantly lower on postoperative day 1, day 5 and 2nd week in Group I.

CONCLUSION

Treatment of saphenous varicose veins by EVLA using a 1470 nm laser and a radial 2ring fiber resulted in comparable occlusion rates at 12 weeks and less postoperative pain and bruising than EVLA with a 980 nm laser and a bare-tip fiber. (This article is a translation of Jpn J Vasc Surg 2014; 23: 964-971.).

Comparison of Bare-Tip and Radial Fiber in Endovenous Laser Ablation with 1470 nm Diode Laser

OBJECTIVE

Major side effects after endovenous laser ablation (EVLA) are pain and bruising. The aim of this study was to compare outcome and side effects after EVLA for primary varicose veins with 1470 nm diode laser using bare-tip orradial fiber.

METHODS

From October 2007 to December 2010, 385 patients (453 limbs) with primary varicose veins treated with 1470 nm laser were studied. Bare-tip fiber was used in 215 patients (242 limbs) (BF group) and radial fiber (ELVeS(TM)Radial, Biolitec AG, Germany) was used in 177 patients (211 limbs) (RF group). This study is a retrospective study and radial fiber was started for use from November 2008. Laser energy was administered at 6-12 W of power in the BF group and 10 W of power in the RF group with constant pullback of laser fiber under tumescent local anesthesia. The patients were assessed by clinical examination and venous duplex ultrasonography at 24-48 h, one week, one month, 4 months and one year follow-up postoperatively.

RESULTS

Mean operating time, length of treated vein and linear endovenous laser energy of all cases were 42.6 min, 36.2 cm and 83.4 J/cm, respectively. Major complications such as deep vein thrombosis and skin burns were not noted. Bruising (1.9% vs. 19.4%) and pain (0.9% vs. 7.4%) were significantly lower in the RF group. Cumulative occlusion rates by Kaplan-Meier method were 100% at 32 months in the RF group and 99.5% at 4 years in the BF group.

CONCLUSION

EVLA using 1470 nm laser with the radial fiber minimized adverse effects compared with bare-tip laser fiber. (English translation of Jpn J Vasc Surg 2013; 22: 615-621).

Diode laser-induced tissue effects: in vitro tissue model study and in vivo evaluation of wound healing following non-contact application

INTRODUCTION

The basic difference between the various common medical laser systems is the wavelength of the emitted light, leading to altered light-tissue interactions due to the optical parameters of the tissue. This study examines laser induced tissue effects in an in vitro tissue model using 1,470 nm diode laser compared to our standard practice for endonasal applications (940 nm diode laser) under standardised and reproducible conditions. Additionally, in vivo induced tissue effects following non-contact application with focus on mucosal healing were investigated in a controlled intra-individual design in patients treated for hypertrophy of nasal turbinate.

METHODS

A certified diode laser system emitting the light of λ = 1470 nm was evaluated with regards to its tissue effects (ablation, coagulation) in an in vitro setup on porcine liver and turkey muscle tissue model. To achieve comparable macroscopic tissue effects the laser fibres (600 µm core diameter) were fixed to a computer controlled stepper motor and the laser light was applied in a reproducible procedure under constant conditions. For the in vivo evaluation, 20 patients with nasal obstruction due to hyperplasia of inferior nasal turbinates were included in this prospective randomised double-blinded comparative trial. The endoscopic controlled endonasal application of λ = 1470 nm on the one and λ = 940 nm on the other side, both in 'non-contact' mode, was carried out as an outpatient procedure under local anaesthesia. The postoperative wound healing process (mucosal swelling, scab formation, bleeding, infection) was endoscopically documented and assessed by an independent physician.

RESULTS

In the experimental setup, the 1,470 nm laser diode system proved to be efficient in inducing tissue effects in non-contact mode with a reduced energy factor of 5-10 for highly perfused liver tissue to 10-20 for muscle tissue as compared to the 940 nm diode laser system. In the in vivo evaluation scab formation following laser surgery as assessed clinically on endonasal endoscopy was significantly reduced on 1,470 nm treated site compared to 940 nm diode laser treated site.

CONCLUSIONS

Diode laser system (1,470 nm) induces efficient tissue effects compared to 940 nm diode laser system as shown in the tissue model experiment. From the clinical point of view, the healing process following non-contact diode laser application revealed to be improved using 1,470 nm diode laser compared to our standard diode laser practise with 940 nm.

Endovenous Laser Application

Introduction: Endovenous laser ablation is becoming a common procedure in clinical routine. Although technical improvements and certain laser parameters are available there is demand to improve the situation by developing feedback-systems, thus getting online information for the clinical outcome and preventing for under- and over-treatment.

Methods: By means of Monte Carlo simulation the potential of detecting signals due to heat induced shrinkage of the vessel was investigated. Remission spectra of native and coagulated vein tissue were compared to identify potential parameters for signalling the physiological change of the tissue due to the heating process. A miniaturized temperature sensor was developed for intraluminal measurements during laser energy application.

Results: Monte Carlo simulation shows that the detection of remitted light from the vessels wall is possible for small vessel calibres of less than 6 mm in diameter. Remission spectra of native compared to coagulated vein tissue differ. While native tissue relates more to the content of deoxy-hemoglobin, the spectra of coagulated tissue relates more to the oxy-hemoglobin state. Based on the principle of temperature dependent fluorescence emission a miniaturized sensor was developed which can be used in the light field of radial emitting fibres.

Conclusion: Several optical changes for online-monitoring of signals during endovenous laser ablation showed potential to serve as feedback mechanism. Up to now, only the measurement of the endoluminal temperature could be realized. Further investigations are needed to find suitable technical realization to prevent for under- or overheating during endovenous laser ablation.

Current standards and recent progress in minimally invasive phlebo surgery

Venous disorders are among the most frequent disease patterns in the Western world. Still at the turn to the 21st century there was no alternative available to the surgical treatment of varicosis. Meanwhile the endoluminal treatment methods have established and have demonstrated their efficiency while having lower side effects in comparison to the traditional treatment, even though conservatively oriented surgeons are still skeptically eyeing these methods. In the US, according to the latest MRG report of 2011, about 95% of all venous surgeries are already done endoluminally. This paper offers an overview of prevailing treatment standards of the most important endoluminal therapy techniques and shows current trends.