Dependence of calculus retropulsion on pulse duration during Ho: YAG laser lithotripsy

BACKGROUND AND OBJECTIVES: The purpose of this study was to investigate the effect of optical pulse duration on stone retropulsion during Ho:YAG (lambda = 2.12 microm) laser lithotripsy. STUDY DESIGN/MATERIALS AND METHODS: A clinical Ho:YAG laser with pulse durations was employed to fragment calculus phantoms and to evaluate stone phantom retropulsion. At a given pulse energy, optical pulse durations were divided into two discrete conditions: short pulse (tau(p): 120 to approximately 190 microseconds at FWHM) and long pulse (tau(p): 210 to approximately 350 microseconds at FWHM). Plaster of Paris calculus phantoms were ablated at different energy levels using optical fibers of varying diameters (273, 365, and 550 microm in core size). The dynamics of the recoil action of a calculus phantom was monitored using a high-speed camera; the laser-induced craters were evaluated with optical coherent tomography (OCT). Bubble formation and collapse were recorded with a fast flash photography setup, and acoustic transients were measured with a hydrophone. RESULTS: Shorter pulse durations produced more stone retropulsion than longer pulses at any given pulse energy. Regardless of pulse duration, higher pulse energy and larger fibers resulted in larger ablation volume and retropulsion (P<0.05). For shorter pulse durations, more rapid bubble expansion was observed and higher amplitudes of the collapse pressure wave were measured (P<0.05). CONCLUSION: Less retropulsion and equivalent fragmentation occurred when Ho:YAG pulse duration increased.     

输尿管结石ESWL失败后输尿管镜钬激光碎石术

目的:评价输尿管结石ESWL失败后输尿管镜钬激光碎石术的临床治疗效果。方法:回顾性分析2002年3月～2005年10月输尿管结石ESWL失败后行输尿管镜钬激光碎石术50例(52侧)临床资料。结果:输尿管镜钬激光一次碎石成功46例(48侧),成功率为92.3%(48/52),2例置镜失败,2例结石移位。46例中,结石并发息肉或肉芽40例,远端狭窄10例,输尿管扭曲8例。结论:输尿管镜钬激光碎石术,创伤小,并发症少,是治疗输尿管结石ESWL失败后的首选方法。     

输尿管软镜钬激光碎石术治疗输尿管上段结石

目的 总结输尿管软镜结合钬激光治疗输尿管上段结石的疗效及并发症,探讨手术技巧.方法 38 例输尿管上段结石患者接受输尿管软镜钬激光碎石治疗,先使用8/9.8 F 输尿管硬镜探查患侧输尿管,置入导丝后留置输尿管软镜鞘,引入输尿管软镜,钬激光碎石,并使用套石篮套取出较大的结石碎屑.结果 35 例患者一期顺利碎石,3 例因输尿管狭窄难以置入输尿管软镜鞘,留置输尿管内支架2 周后再次手术成功.手术时间31~56 min,平均42 min.术后7 例患者发热,无其他严重并发症.术后1 个月拔除内支架,2 周后复查KUB,结石清除率92.1%.结论 输尿管软镜结合钬激光是处理输尿管上段结石的有效手段,即便输尿管结石进入肾内,也可一期处理,避免了额外的体外碎石操作.     

大功率钬激光治疗膀胱结石初步临床研究

目的 研究大功率（６０Ｗ以上）钬激光粉碎结石的性能及其有效合理的碎石参数。方法：（１）体外实验，将１２枚泌尿系结石（结石成分为尿酸结石，草酸结石，磷酸结石，大小１．０～２．０ｃｍ）浸于生理盐水中，在不同钬激光参数设置下，用钬激光粉碎结石（结石粉碎至〈０．５ｍｍ）观察钬激光碎石能力，合理有效的参数设置及对不同成分结石的碎石情况等。（２）临床应用，经耻骨上穿刺，用大功率钬激光治疗膀胱结石６例，结石成分     

Ho:YAG激光治疗浅表性膀胱肿瘤的临床观察

目的 总结应用Ho:YAG激光治疗浅表性膀胱肿瘤的方法及疗效。方法 术前经膀胱镜，病理诊断为浅表性膀胱肿瘤患者52例。单发39例。多发13例，肿瘤共87个，经膀胱镜置入光纤，直视下应用脉冲式Ho:YAG激光切除，汽化膀胱肿瘤及基肿瘤基底周围膀胱粘膜。结果 52例中，9例局麻下门诊完成，术后未留置导尿管，43例留置导尿管1-3d。手术时间10-40min，平均25min，术后创面无瘤细胞残留，术中术后无出血，膀胱穿孔，闭孔神经反射等并发症，7例输尿管口肿瘤术后输尿管口无狭窄，输尿管无种植，50例术后随访3-31个月，6例复发，复发率12%。结论 Ho:YAG激光治疗膀胱肿瘤简单易行，无并发症，在治疗输尿管口肿瘤及常规电切镜不易达到的肿瘤具有优势，是治疗浅表性膀胱肿瘤的一种方法。     

Ablation of composite resins using Er:YAG laser--comparison with enamel and dentin

OBJECTIVES: The purpose of this work is to investigate comparative ablation rate between composite resins and dental hard tissues (enamel and dentin) after Er:YAG laser irradiation to verify possible development of an ultra-conservative dentistry to with minimum effect for the teeth tissue. METHODS: We have used 11 extracted or exfoliated primary anterior and posterior teeth and six extracted permanent molar teeth. Three different types of composite resin were chosen (microfiller, hybrid, and condensable) in terms of chemical and structural composition. Composite tablets and the teeth were irradiated with a Er:YAG laser at different laser beam energy level per pulse (100, 200, 300, and 400 mJ). Diameter and depth of each resulted microcavity were measured and the material removed volumes were calculated. The resulted values were plotted and fitted to allow a comparative observation of the material removed as a function of energy level per pulse. RESULTS: While the idea of ultra-conservative dentistry seems to apply well for enamel of primary and permanent teeth, at the present stage it does not apply well for primary or permanent dentin. For dentin, the composition and content of water makes the Er:YAG laser ablation equal or superior in rate compared with the three used resins. SIGNIFICANCE: This work presents of a comparative study of Er:YAG laser ablation, allowing to analyze the possible selective ablation between composite resin placed and cured and dental hard tissues, with the goal to propose a new clinical technique: differential ablation for composite resin restorations using Er:YAG laser.     

The ablation threshold of Er:YAG and Er:YSGG laser radiation in dental enamel

. The scientific investigation of fundamental problems plays a decisive role in understanding the mode of action and the consequences of the use of lasers on biological material. One of these fundamental aspects is the investigation of the ablation threshold of various laser wavelengths in dental enamel. Knowledge of the relationships and influencing factors in the laser ablation of hard tooth tissue constitutes the basis for use in patients and the introduction of new indications. The present paper examines the ablation threshold of an Er:YAG laser (λ=2.94 μm) and an Er:YSGG laser (λ=2.79 μm) in human dental enamel. To this end, 130 enamel samples were taken from wisdom teeth and treated with increasing energy densities of 2–40 J/cm². The sample material was mounted and irradiated on an automated linear micropositioner. Treatment was performed with a pulse duration of τ_P(FWHM)≈150 μs and a pulse repetition rate of 5 Hz for both wavelengths. The repetition rate of the laser and the feed rate of the micropositioner resulted in overlapping of the single pulses. The surface changes were assessed by means of reflected light and scanning electron microscopy. On the basis of the results, it was possible to identify an energy density range as the ablation threshold for both the Er:YAG and the Er:YSGG laser. With the Er:YAG laser, the transition was found in an energy density range of 9–11 J/cm². The range for the Er:YSGG laser was slightly higher at 10–14 J/cm². Paper received 15 May 2001; accepted after revision 14 January 2002. Correspondence to: Dr Christian Apel, Department of Conservative Dentistry, Periodontology and Preventive Dentistry, University of Aachen, Pauwelsstr. 30, D-52074 Aachen, Germany. Tel.: +49 241 8089088; Fax: +49 241 8888468; e-mail: capel@post.klinikum.rwth-aachen.de     

A comparison of holmium:YAG laser with Lithoclast lithotripsy in ureteral calculi fragmentation

PURPOSE: Among various intracorporeal lithotriptors, Lithoclast (EMS, Switzerland) has become the widely used tool for the treatment of urinary stones. Recently, the holmium:YAG laser has been used with a wide range of potential urological applications, including intracorporeal lithotripsy of urinary calculi. The purpose of the present study is to compare Lithoclast with holmium:YAG laser lithotripsy in ureteral calculi fragmentation. METHODS: Out of 51 patients with ureteral calculi, 26 underwent Lithoclast lithotripsy and 25 holmium:YAG lithotripsy using a 8/9.8F rigid ureteroscope. There were no changes to the ureteroscopes, video monitors, baskets or irrigation devices during the study period. RESULTS: There were no differences in patient age, sex, stone size and location of stones between these groups. The immediate stone-free rates were 96.0% in the holmium:YAG group and 73.1% in the Lithoclast group (P < 0.05). The 3-month stone-free rates were 96.0% and 84.6%, respectively (P = 0.350). The mean operation time and mean period of postoperative hospitalization in the holmium:YAG group (49.8 min and 1.0 days, respectively) were shorter than those of the Lithoclast counterpart (76.9 min and 2.5 days, respectively). Post-treatment complications, such as ureteral perforation, were encountered in only two patients who underwent Lithoclast. CONCLUSIONS: Holmium:YAG lithotripsy was associated with shorter operation time and postoperative hospitalization period. These data also suggest that holmium:YAG lithotripsy was safe and more effective than Lithoclast lithotripsy in the aspect of immediate stone free rate. We believe that holmium:YAG laser is an excellent treatment modality for managing ureteral calculi.     

提高输尿管镜钬激光治疗输尿管上段结石成功率的体会

目的：总结输尿管镜钬激光治疗输尿管上段结石时减少碎石上移和提高碎石成功率的体会。方法：用输尿管镜钬激光治疗输尿管上段结石71例,对其中35例第4腰椎横突以上结石碎石前预置金属或N—Trap网篮,对15例反流入肾盂〉0．4cm碎石辅以输尿管软镜钬激光碎石。结果：输尿管穿孔1例;原位残留碎石1例;15例〉0．4cm碎石被冲入。肾盂,用输尿管软镜钬激光辅助肾盂内碎石;失败3例。本组输尿管镜钬激光治疗输尿管上段结石一次碎石成功65／71（91．6％）。结论：在输尿管镜钬激光碎输尿管上段结石中,预置金属或N—Trap网篮可以减少碎石反流入肾盂机会,对已反流入肾盂的碎石结合输尿管软镜钬激光治疗,可以提高输尿管镜钬激光治疗输尿管上段结石的一次碎石成功率。     

Effects of Er:YAG and Nd:YAG laser irradiation on radicular dentine permeability using different irrigating solutions

BACKGROUND AND OBJECTIVES: To evaluate the effect of Er:YAG and Nd:YAG laser on radicular dentine permeability when using distilled and deionized water and 1% NaClO as irrigating solutions. STUDY DESIGN/MATERIALS AND METHODS: Thirty human maxillary canines were divided randomly into six groups. The root canals were instrumented with K files and the step-back technique. Group I, irrigation with distilled and deionized water; Group II, irrigation with 1% NaClO; Group III, irrigation with distilled and deionized water and Er:YAG laser application (140 mJ input, 61 mJ output 15 Hz, 300 pulses, and 42 J); Group IV, irrigation with 1% NaClO and Er:YAG laser application (same parameters as Group III); Group V, irrigation with distilled and deionized water and Nd:YAG laser application (150 mJ, 15 Hz, 2,25 W); Group VI, irrigation with 1% NaClO and Nd:YAG laser application (same parameters as Group V). During laser application the teeth were always filled with the irrigating solution. The tip was withdrawn gently in helicoidal movement from the apex to the cervical portion. The teeth were processed for histochemical evaluation. RESULTS: The Tukey test showed that the cervical and middle thirds were statistically similar (P > 0.05) and significantly greater than the apical third (P < 0.05). The Scheffé test showed significantly greater dentine permeability in root canals in which water and Er:YAG laser were used and were significantly different from the other treatments (P < 0.05). CONCLUSIONS: The use of distilled and deionized water and Er:YAG laser showed the greater increase of dentine permeability. The use of 1% NaClO with Nd:YAG laser, distilled, and deionized water with Nd:YAG laser and the use of water increased dentine permeability less than the other groups. The use of 1% NaClO with and without Er:YAG laser application were positioned intermediately among the treatments.     

Analysis of hyperpigmentation and hypopigmentation after Er:YAG laser skin resurfacing

BACKGROUND AND OBJECTIVES: Pigmentary disorders--such as hyperpigmentation and hypopigmentation, are devastating complications of erbium:yttrium-aluminum-garnet (Er:YAG) laser resurfacing. This study was undertaken to assess the clinical and histopathologic features of hyperpigmentation and hypopigmentation following Er:YAG laser resurfacing, especially in darker skin. STUDY DESIGN/MATERIALS AND METHODS: One hundred and ninety patients (skin phototypes III and above), treated with Er:YAG lasers--short-pulsed and modulated (variable-pulsed and dual-mode) Er:YAG lasers--for skin resurfacing were recruited. The clinical features of hyperpigmentation and hypopigmentation were evaluated retrospectively using medical charts and serial photographs. For histopathologic examinations, skin biopsies were performed in three patients at hyperpigmentation sites and in four patients at hypopigmentation sites. RESULTS: Hyperpigmentation was observed in 38.4% of the patients. Mean onset and duration were 3.5 and 7.2 weeks, and then it has faded away within 16 weeks in 93.2% of cases. Hypopigmentation was observed in 13.7% of the patients; its mean onset was 2 months after treatment, and it faded within 1 year in 85% of cases. The incidences and mean durations of these side effects were more intense and longer in patients treated with short-pulsed, variable-pulsed, and dual-mode Er:YAG lasers, in increasing order. In terms of histopathologic examinations, melanin amounts in the epidermal basal layer were observed to vary. CONCLUSIONS: Hyperpigmentation and hypopigmentation are frequent complications of Er:YAG laser resurfacing. Long pulse duration-induced thermal damage seems to be the most important factor in terms of the induction of pigmentary disorders.     

Laser induced fragmentation of salivary stones: an in vitro comparison of two different, clinically approved laser systems

BACKGROUND: Clinical laser lithotripsy in urology promises a good fragmentation combined with a minimal risk of soft tissue damage and low medical complications. This in vitro study investigates the fragmentation of salivary stones by means of two clinically used laser systems. MATERIALS AND METHODS: The effects induced by the FREDDY laser (WOM, Germany, lambda = 532 nm/1,064 nm, E(pulse) = 120-160 mJ/pulse) and the Ho:YAG (AURIGA, StarMedTec, Germany, lambda = 2,100 nm, E(pulse) = 300-800 mJ/pulse) on clinical salivary calculi (n = 15) and on salivary gland tissue were investigated using clinical laser parameter settings. All experiments were performed in an under water experimental set-up using flexible fibres (core diameter 230 microm) positioned in front of each specimen. In order to assess fragmentation efficacy, each stone was placed on a grating (rhombic mash-diameter 1-3 mm). The fragmentation rate was calculated with respect to the energy applied (mg/J), to the number of pulses (mg/pulse), and to the time needed (mg/minute). In addition the composition of the stones were analysed spectrographically. The soft tissue interaction on human salivary duct mucosa was examined histologically (HE-staining). RESULTS: Spectrographic composition of the salivary stones showed a two component ratio of protein/carbonate apatite varying between 5/95 and 25/75. Stones treated by the Ho:YAG were vaporised in a milling-like process, while using the FREDDY laser stones are cracked into pieces and fragmentation failed in two cases. The fragmentation rates achieved by the FREDDY laser were greater than those of the Ho:YAG laser, but fragments mainly bigger. A dependency on the composition of the stones could not be found. Laser pulse effects on soft tissue were found slightly beyond the mucosa. CONCLUSION: This study clearly demonstrated the different processes of destroying salivary stones using two different laser systems. While the Ho:YAG vaporises the calculi in a more milling and soft sense, the FREDDY shows a more cracking and explosive destruction. Although both laser systems showed little direct risk to the surrounding tissue, it has to be proven whether cracked and accelerated particles could cause harm to soft tissue. With respect to this, further in vitro studies and clinical treatments in selected cases are needed to proof these results.     

Effects of Er:YAG laser and Nd:YAG laser treatment on the root canal dentin of human teeth: a SEM study

The objective of the study was to observe the morphological changes on root canal dentin after Er:YAG laser and Nd:YAG laser treatment. Twenty-one teeth biomechanically prepared were divided into three groups with seven teeth of each. Group A was unlased as a control. In group B, Er:YAG laser and in group C, Nd:YAG laser was applied to the root canal dentin. The roots were split longitudinally and examined using a scanning electron microscopy for the evaluation of debris, smear layer, and recrystallization. There was no statistically significant difference between the groups. This study indicates that laser beam is not effective in removing debris and smear layer.     

经尿道前列腺汽化电切联合钬激光碎石治疗前列腺增生合并膀胱结石

目的探讨前列腺汽化电切(TUVP)和钬激光同期治疗前列腺增生合并膀胱结石的疗效及安全性。方法总结24例前列腺增生合并膀胱结石患者,应用钬激光经尿道膀胱镜粉碎膀胱结石并同期行TUVP的临床资料。结果24例患者中,膀胱结石均一次碎石成功,碎石后行TUVP,无膀胱结石残留、膀胱穿孔及水中毒发生,手术时间62~160min,平均手术时间88 min,切除前列腺质量20~120 g,平均38 g,术后平均拔除尿管时间3~6 d,平均4.75 d,平均住院时间10 d,所有患者术后均排尿通畅,无尿失禁。结论TUVP和钬激光同期治疗前列腺增生合并膀胱结石是一种安全有效的治疗方法,具有损伤小、结石清除率高、并发症少等优点。     

铒激光微剥脱治疗脂溢性角化病63例疗效观察

目的:观察铒激光微剥脱治疗脂溢性角化病的临床疗效。方法:采用铒激光微剥脱治疗脂溢性角化病63例,210个皮损,根据皮损的部位、性质及对激光的反应,选择能量10～12.5J/cm2治疗。结果:63例患者,共计210个皮损,治疗8周后随访,176个皮损痊愈,治愈率83.80%,34个皮损显效,有效率100%,未出现创面感染和瘢痕形成。结论:铒激光微剥脱治疗脂溢性角化病有效且安全。     

Comparison of Er:YAG and 9.6-microm TE CO(2) lasers for ablation of skull tissue

BACKGROUND AND OBJECTIVE: Craniotomy by using a drill and saw frequently results in fragmentation of the skull plate. Lasers have the potential to remove the skull plate intact, simplifying the reconstructive surgery. STUDY DESIGN/MATERIALS AND METHODS: Transverse-excited CO(2) lasers operating at the peak absorption wavelength of bone (lambda = 9.6 microm) and with pulse durations of 5-8 microsec, approximately the thermal relaxation time in hard tissue, produced high ablation rates and minimal peripheral thermal damage. Both thick (2 mm) and thin (250 microm) bovine skull samples were perforated and the ablation rates calculated. Results were compared with Q-switched and free-running Er:YAG lasers (lambda = 2.94 microm, tau(p) = 0.5 microsec and 300 microsec). RESULTS: The CO(2) laser produced ablation rates of up to 60 and 15 microm per pulse for thin and thick sections, respectively, and perforated thin and thick sections with fluences of less than 1 J/cm(2) and 6 J/cm(2), respectively. There was no discernible thermal damage and no need for water irrigation during ablation. Pulse durations > or =20 microsec resulted in significant tissue charring, which increased with the pulse duration. Although the free-running Er:YAG laser produced ablation rates of up to 100 microm per pulse, fluences of 10 J/cm(2) and 30 J/cm(2) were required to perforate thin and thick samples, respectively, and peripheral thermal damage measured 25-40 microm. CONCLUSIONS: In summary, the novel 5- to 8-microsec pulse length of the TE CO(2) laser is long enough to avoid a marked reduction in the ablation rate due to plasma formation and short enough to avoid peripheral thermal damage through thermal diffusion during the laser pulse. Furthermore, in vivo animal studies with the TE CO(2) laser are warranted for potential clinical application in craniotomy and craniofacial procedures.     

Treatment of ureteric lithiasis with retrograde ureteroscopy and holmium:YAG laser lithotripsy vs extracorporeal lithotripsy

OBJECTIVE

To analyse the efficiency of extracorporeal shockwave lithotripsy (ESWL) vs retrograde ureteroscopy and holmium:YAG laser lithotripsy, as ESWL is successful in 67–90% of cases but endoscopic lithotripsy with pneumatic lithotrites or lasers is successful in 90–96% of distal ureteric calculi, and holmium:YAG lithotripsy is effective in proximal ureteric calculi.

PATIENTS AND METHODS

From April 2006 to April 2008 we assessed 164 patients undergoing ureteric lithiasis in two homogeneous groups: group A included 83 treated with retrograde ureteroscopy and holmium:YAG endoscopic lithotripsy, and group B, 81 treated by ESWL. For laser lithotripsy we used 2071 mJ pulses at 3–6 Hz, with a mean of 1105 pulses and 2.5 kJ of total energy. ESWL was carried out using 37.5–87.5 mJ shock waves, a mean of 3650 shock waves and 187.6 J, with a radioscopy time of 1–4 min. The results were assessed after 3 weeks with plain films and ultrasonography, or urography. The efficiency of each procedure was assessed by calculating the relative risk, and results compared using the chi‐square or Student’s t‐test. The efficiency quotient (EQ) was determined for both procedures, and the focal applied energy quotient (FAEQ) used to assess ESWL.

RESULTS

The overall success rate for retrograde ureteroscopy and laser lithotripsy was 96.4% (80/83 patients), with an EQ of 0.52; a JJ catheter was placed in 67 patients. The success rate for the first ESWL session was 48%, and after repeat ESWL was 64% (52/81 patients), giving an EQ of 0.39. For successful treatments the FAEQ was 9.22, vs 6.47 for the failures (P < 0.005). There was a significant difference (P < 0.001) favouring laser lithotripsy, with an absolute benefit of 46% (95% confidence interval 33.8–57.9%), and number needed to treat of 2 (2–3), but no significant differences for lumbar ureteric calculi.

CONCLUSIONS

Endoscopic lithotripsy with the holmium laser is more effective than ESWL, but for lumbar ureteric calculi ESWL is therapeutically recommended as it is less invasive.