Browsing by Author "Traxer, O"
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- Are we all doing it wrong? Influence of stripping and cleaving methods of laser fibers on laser lithotripsy performance.Publication . Kronenberg, P; Traxer, OPURPOSE: We assessed whether stripping and cleaving the laser fiber tip with specialized tools, namely laser fiber strippers, or ceramic or metal scissors, would influence lithotripsy performance. MATERIALS AND METHODS: Laser fiber tips were stripped with a specialized laser fiber stripper or remained coated. The tips were then cleaved with metal or ceramic scissors. Laser lithotripsy experiments were performed with the 4 fiber tip combinations using an automated laser fragmentation testing system with artificial stones made of plaster of Paris or BegoStone Plus (Bego, Lincoln, Rhode Island). High frequency-low pulse energy (20 Hz and 0.5 J) and low frequency-high pulse energy (5 Hz and 2.0 J) settings were used for 30 seconds. Fissure width, depth and volume, and laser fiber tip photos were analyzed. RESULTS: Coated laser fiber tips always achieved significantly higher ablation volumes (sometimes greater than 50%) than stripped laser fiber tips (p <0.00001) regardless of cleaving scissor type, stone material or lithotripter setting. Coated fiber tips cleaved with metal scissors ablated as well as those cleaved with ceramic scissors (p = 0.16). However, stripped fibers were much less ablative when they were cut with metal scissors compared to ceramic scissors (p <0.00001). Harder stone material decreased ablation volume (p <0.00001). Low frequency-high pulse energy settings were an average of 3 times more ablative than high frequency-low pulse energy settings (p <0.00001). Stripping the fibers, a harder stone material and low frequency-high pulse energy settings were associated with increased fiber tip degradation. CONCLUSIONS: Coated laser fibers provided better lithotripsy performance and metal scissors were as good as ceramic scissors to cleave coated fibers. This knowledge may improve and simplify the way that laser lithotripsy procedures are done worldwide.
- Do We Really Need to Wear Proper Eye Protection When Using Holmium:YAG Laser During Endourologic Procedures? Results from an Ex Vivo Animal Model on Pig Eyes.Publication . Villa, L; Cloutier, J; Compérat, E; Kronemberg, P; Charlotte, F; Berthe, L; Rouchausse, Y; Salonia, A; Montorsi, F; Traxer, OPURPOSE: We sought to evaluate the effect of holmium:yttrium-aluminum-garnet (Ho:YAG) laser exposure on ex vivo pig eyes and to test the protective action of different glasses in preventing eye lesions in case of accident. MATERIALS AND METHODS: We pointed the tip of a Ho:YAG laser fiber from different distances (0, 3, 5, 8, 10, and 20 cm, respectively) toward the center of the pupil of the pig eye. The Ho:YAG laser was activated for 1 or 5 seconds at three different settings (0.5 J-20 Hz, 1 J-10 Hz, and 2 J-10 Hz, respectively). The experiment was repeated using laser safety glasses and eyeglasses. A total of 78 pig eyes were used. The effects of the Ho:YAG laser on pig eyes were assessed by histopathology. Comparable laser emission experiments were performed on thermal paper at different distances using different pulse energies. RESULTS: Ho:YAG laser-induced corneal lesions were observed in unprotected eyes, ranging from superficial burning lesions to full-thickness necrotic areas, and were directly related to pulse energy and time of exposure and inversely related to the distance from the eye. When the laser was placed 5 cm or more, no corneal damage was observed regardless of the laser setting and the time of exposure. Similar distance/energy level relationships were observed on thermal paper. No damage was observed to the lens or the retina in any of the Ho-YAG laser-treated eyes or in any of the eyes protected by laser safety and eyeglasses. CONCLUSIONS: Ho:YAG lasers can cause damage when set to high energy, but only to the cornea, from close distances (0-5 cm) and in the absence of eye protection. Eyeglasses are equally effective in preventing laser damage as laser safety glasses.
- In vitro fragmentation efficiency of holmium: yttrium-aluminum-garnet (YAG) laser lithotripsy--a comprehensive study encompassing different frequencies, pulse energies, total power levels and laser fibre diametersPublication . Kronenberg, P; Traxer, OOBJECTIVE: To assess the fragmentation (ablation) efficiency of laser lithotripsy along a wide range of pulse energies, frequencies, power settings and different laser fibres, in particular to compare high- with low-frequency lithotripsy using a dynamic and innovative testing procedure free from any human interaction bias. MATERIALS AND METHODS: An automated laser fragmentation testing system was developed. The unmoving laser fibres fired at the surface of an artificial stone while the stone was moved past at a constant velocity, thus creating a fissure. The lithotripter settings were 0.2-1.2 J pulse energies, 5-40 Hz frequencies, 4-20 W power levels, and 200 and 550 μm core laser fibres. Fissure width, depth, and volume were analysed and comparisons between laser settings, fibres and ablation rates were made. RESULTS: Low frequency-high pulse energy (LoFr-HiPE) settings were (up to six times) more ablative than high frequency-low pulse energy (HiFr-LoPE) at the same power levels (P < 0.001), as they produced deeper (P < 0.01) and wider (P < 0.001) fissures. There were linear correlations between pulse energy and fragmentation volume, fissure width, and fissure depth (all P < 0.001). Total power did not correlate with fragmentation measurements. Laser fibre diameter did not affect fragmentation volume (P = 0.81), except at very low pulse energies (0.2 J), where the large fibre was less efficient (P = 0.015). CONCLUSIONS: At the same total power level, LoFr-HiPE lithotripsy was most efficient. Pulse energy was the key variable that drove fragmentation efficiency. Attention must be paid to prevent the formation of time-consuming bulky debris and adapt the lithotripter settings to one's needs. As fibre diameter did not affect fragmentation efficiency, small fibres are preferable due to better scope irrigation and manoeuvrability.
- Lithotripsy Performance of Specially Designed Laser Fiber TipsPublication . Kronenberg, P; Traxer, OWe evaluated and compared a standard laser lithotripsy fiber to laser fibers claimed to have lithotripsy performance enhancing features. MATERIALS AND METHODS: A special AccuMax™ 200 polished tip fiber and an AccuTrac™ ball-shaped tip fiber, each with an approximately 240 μm core, were compared to a standard 272 μm core fiber (Rocamed™). The polished and ball-shaped tip fibers were used and reused without preparation. The standard fiber was stripped and cleaved according to manufacturer instructions after each experiment. An automated laser fragmentation testing system was used to perform multiple 30-second laser lithotripsy experiments. To mimic most typical lithotripsy conditions soft and hard stone materials were used with high frequency, low pulse energy (20 Hz and 0.5 J) or with low frequency, high pulse energy (5 Hz and 2.0 J) lithotripter settings. Ablation volumes and laser fiber tip photographs before and after lithotripsy were compared. RESULTS: The standard and ball-shaped tip fibers did not differ in ablation volume (p = 0.72) but they ablated 174% and 188% more stone, respectively, than the polished tip fiber (p <0.0001). The ball-shaped tip showed remarkable fiber tip degradation after short-term use at low frequency, high pulse energy settings. When high pulse energy settings were applied first even for short-term use, the ablation volume achieved by the polished and ball-shaped tip fibers at high frequency, low pulse energy settings decreased more than 20%. CONCLUSIONS: The standard laser fiber was as good as and sometimes better than the specially designed fibers. Rapid degradation of the specially designed laser fiber tips strongly limits their general usefulness but ball-shaped tip fibers may be useful in specific situations.
- The truth about laser fiber diametersPublication . Kronenberg P, P; Traxer, OOBJECTIVE: To measure the various diameters of laser fibers from various manufacturers and compare them with the advertised diameter. METHODS: Fourteen different unused laser fibers from 6 leading manufacturers with advertised diameters of 200, 270, 272, 273, 365, and 400 μm were measured by light microscopy. The outer diameter (including the fiber coating, cladding, and core), cladding diameter (including the cladding and the fiber core), and core diameter were measured. Industry representatives of the manufacturers were interviewed about the diameter of their fibers. RESULTS: For all fibers, the outer and cladding diameters differed significantly from the advertised diameter (P <.00001). The outer diameter, which is of most practical relevance for urologists, exhibited a median increase of 87.3% (range, 50.7%-116.7%). The outer, cladding, and core diameters of fibers with equivalent advertised diameters differed by up to 180, 100, and 78 μm, respectively. Some 200-μm fibers had larger outer diameters than the 270- to 273-μm fibers. All packaging material and all laser fibers lacked clear and precise fiber diameter information labels. Of 12 representatives interviewed, 8, 3, and 1 considered the advertised diameter to be the outer, the cladding, and the core diameter, respectively. Representatives within the same company frequently gave different answers. CONCLUSION: This study suggests that, at present, there is a lack of uniformity between laser fiber manufacturers, and most of the information conveyed to urologists regarding laser fiber diameter may be incorrect. Because fibers larger than the advertised laser fibers are known to influence key interventional parameters, this misinformation can have surgical repercussions.
- Update on lasers in urology 2014: current assessment on holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripter settings and laser fibers.Publication . Kronenberg, P; Traxer, OPURPOSE: The purpose of the study was to review the existing literature on holmium:yttrium-aluminum-garnet laser lithotripsy regarding lithotripter settings and laser fibers. METHODS: An online search of current and past peer-reviewed literature on holmium laser lithotripsy was performed on several databases, including PubMed, SciElo, and Google Scholar. Relevant studies and original articles about lithotripter settings and laser fibers were examined, and the most important information is summarized and presented here. RESULTS: We examine how the choice of lithotripter settings and laser fibers influences the performance of holmium laser lithotripsy. Traditional laser lithotripter settings are analyzed, including pulse energy, pulse frequency, and power levels, as well as newly developed long-pulse modes. The impact of these settings on ablation volume, fragment size, and retropulsion is also examined. Advantages of small- and large-diameter laser fibers are discussed, and controversies are highlighted. Additionally, the influence of the laser fiber is examined, specifically the fiber tip preparation and the lithotripter settings' influence on tip degradation. CONCLUSIONS: Many technical factors influence the performance of holmium laser lithotripsy. Knowing and understanding these controllable parameters allows the urologist to perform a laser lithotripsy procedure safely, efficiently, and with few complications.