A method for reducing thermal injury during the ureteroscopic holmium laser lithotripsy

Objective:Many studies have demonstrated the heat effect from the holmium laser lithotripsy can cause persistent thermal injury to the ureter.The purpose of this study was to elucidate the use of a modified ureteral catheter with appropriate firing and irrigation to reduce the thermal injury to the“ureter”during the ureteroscopic holmium laser lithotripsy in vitro.Methods:An in vitro lithotripsy was performed using a modified catheter(5 Fr)as the entrance for the irrigation and the holmium laser fiber while using the remaining space in the ureteroscopic channel as an outlet.Different laser power settings(10 W,20 W,and 30 W)with various firing times(3 s,5 s,and 10 s)and rates of irrigation(15 mL/min,20 mL/min,and 30 mL/min)were applied in the experiment.Temperature changes in the“ureter”were recorded with a thermometer during and after the lithotripsy.Results:During the lithotripsy,the local highest mean temperature was 60.3℃ and the lowest mean temperature was 26.7℃.When the power was set to 10 w,the temperature was maintained below 43℃ regardless of laser firing time or irrigation flow.Regardless of the power or firing time selected,the temperature was below 43℃ at the rate of 30 mL/min.There was a significant difference in temperature decrease when continuous 3 s drainage after continuous firing(3 s,5 s,or 10 s)compared to with not drainage(p<0.05)except for two conditions of 0.5 J×20 Hz,30 mL/min,firing 5 s,and 1.0 J×10 Hz,30 mL/min,firing 5 s.Conclusion:Our modified catheter with timely drainage reducing hot irrigation may significantly reduce the local thermal injury effect,especially along with the special interrupted-time firing setting during the simulated holmium laser procedure.

Thulium fiber laser lithotripsy:Is it living up to the hype?

Objective:The holmium:yttrium-aluminium-garnet laser(Ho:YAG)has been the gold standard for laser lithotripsy over the last three decades.After demonstrating good in vitro efficacy,the thulium fiber laser(TFL)has been recently released in the market and the initial clinical results are encouraging.This article aims to review the main technology differences between the Ho:YAG laser and the TFL,discuss the initial clinical results with the TFL as well as the optimal settings for TFL lithotripsy.Methods:We reviewed the literature focusing on the technological aspects of the Ho:YAG laser and TFL as well as the results of in vitro and in vivo studies comparing both technologies.Results:In vitro studies show a technical superiority of TFL compared to the Ho:YAG laser and encouraging results have been demonstrated in clinical practice.However,as TFL is a new technology,limited studies are currently available,and the optimal settings for lithotripsy are not yet established.Conclusion:TFL has the potential to be an alternative to the Ho:YAG laser,but more reports are still needed to determine the optimal laser for lithotripsy of urinary tract stones when considering all parameters including effectiveness,safety,and costs.

Bouveret syndrome masquerading as a gastric mass-unmasked with endoscopic luminal laser lithotripsy:A case report

BACKGROUND Bouveret syndrome,also known as gallstone ileus,is a rare form of gastric outlet obstruction accounting for 1%-3%of cases.This condition is most often reported in females.The diagnosis can be challenging and is often missed due to atypical presentations,which occasionally mimic gastric outlet obstruction symptoms such as nausea,vomiting,loss of appetite and hematemesis.The symptoms vary with stone size.Larger stones are managed with a surgical approach,but this carries increased morbidity and mortality.Over the past decade,the endoscopic approach has emerged as an alternative mode of treatment,but it is generally unsuccessful in the management of larger-sized stones.A literature review revealed cases of successful endoscopic treatment requiring multiple sessions for stone sizes measuring up to about 4.5 cm.Here we present a unique case of an elderly patient with Bouveret syndrome with a 5 cm stone mimicking a gastric mass and causing gastric outlet obstruction,who was successfully managed in a single session using a complete endoscopic approach with laser lithotripsy.CASE SUMMARY An 85-year-old female patient presented with 1-month history of intermittent abdominal pain,vomiting,decreased appetite and weight loss.An abdominal computed tomography showed a 4.5 cm×4.7 cm partially calcified mass at the gastric pylorus causing gastric outlet obstruction.Endoscopy showed an ulcerated fistulous opening and a large 5 cm impacted gallstone in the duodenal bulb.Endoscopic nets and baskets were used in an attempt to remove the stone,but this approach was unsuccessful.Given her advanced age,poor physical condition and underlying comorbidities,she was deemed to be high-risk for surgery.Thus,a minimally invasive approach using endoscopic laser lithotripsy was attempted and successfully treated the stone.Post-procedure,the patient experienced complete resolution of her symptoms with no complications and was able to tolerate her diet.She was subsequently discharged home at 48 h,with an uneventful recovery.CONCLUSION In our paper we describe Bouveret syndrome and highlight its management with a novel endoscopic approach of laser lithotripsy in addition to various other endoscopic approaches available to date and its success rates.

Management hepatolithiasis with operative choledochoscopic FREDDY laser lithotripsy combined with or without hepatectomy

BACKGROUND: Hepatolithiasis is very common in East Asia. It is benign in nature, but has a high recurrence rate. It is likely to lead to biliary cirrhosis and increase the risk of cholangiocarcinoma. Hence, the treatment of hepatolithiasis is difficult but vital. In this report, we present a novel approach to manage hepatolithiasis using the choledochoscopic Frequency-Doubled Double pulse Nd:YAG (FREDDY) laser lithotripsy combined with or without hepatectomy. METHODS: Between July 2009 and October 2012, 45 patients underwent choledochoscopic FREDDY laser lithotripsy combined with or without hepatectomy (laser lithotripsy group). Fortyeight patients underwent a traditional operation (traditional method group) from January 2009 to June 2009. Comparative analysis was made of demographic and clinical characteristics of the two groups. RESULTS: The final stone clearance rate of the laser lithotripsy group was 93.3%, whereas that of the traditional method group was 85.4% (P=0.22). In the laser lithotripsy group, 2 patients experienced hemobilia and 3 patients had acute cholangitis. In the traditional method group, 3 patients had intraoperative hemorrhage, 1 patient had bile leakage, 6 patients had acute cholangitis, and 1 patient died of liver failure. Moreover, the operative time in the traditional method group was significantly longer than that in the laser lithotripsy group (P=0.01). The mean hospital stay of the patients in the traditional method group was longer than that in the laser lithotripsy group (9.8 vs8.2 days, P=0.17). Recurrent intrahepatic bile duct stones were not found during the follow-up period in the two groups. CONCLUSION: Operative choledochoscopic FREDDY laser lithotripsy combined with or without hepatectomy may be an effective and safe treatment for hepatolithiasis.

Ureteroscopic Holmium:YAG Laser Lithotripsy for Managing Ureteral Calculi (A Report of 168 Cases)

Summary: The effectiveness and safety of ureteroscopic holmium:YAG laser lithotripsy for managing ureteral calculi was evaluated. Ureteroscopic holmium:YAG laser lithotripsy was performed in 168 ureteral calculi (upper 27 cases, middle 33 cases and lower 108 cases). The results showed that the stone-free rate was 92.6 % in the upper ureteral calculi, 93.9 % in the middle ureteral calculi and 94.4 % in the lower ureteral calculi, respectively. The complication rate was 4.8 % (8 cases). It was suggested that ureteroscopic holmium:YAG laser lithotripsy is a highly effective and safe treatment modality for managing ureteral calculi.

Successful endoscopic treatment of a large impacted gallstone in the duodenum using laser lithotripsy,Bouveret’s syndrome:A case report

BACKGROUND Bouveret´s syndrome is defined as a gastric outlet obstruction after passage of a gallstone through a fistula into the duodenum.Due to its rarity,the diagnosis of Bouveret’s syndrome is often delayed and causes a high morbidity and mortality rate.CASE SUMMARY A 93-year-old female presented with worsening pain in the right upper abdomen and vomiting.A gastroscopy revealed fluid retention caused by a massive obstructive stone in the bulbus.Endoscopic laser lithotripsy of the impacted stone was planned after multidisciplinary consultation.A Dornier Medilas H Solvo lithotripsy 350μm laser fiber(10 Hz,2 Joules)was used to disintegrate the stone into smaller pieces.The patient recovered completely.CONCLUSION A mechanical obstruction due to a gallstone that has entered the gastrointestinal tract is a complication that appears in 0.3%-0.5%of patients who have cholelithiasis.Stones larger than 2 cm can become impacted in the digestive tract,which occurs mostly in the terminal ileum.In approximately 1%-3%of cases,the stones cause obstruction in the duodenum.This phenomenon is called Bouveret’s syndrome.As this condition is mostly observed in elderly individuals with multiple comorbidities,treatment by an open surgical approach is unsuitable.Endoscopic removal is the preferred technique.The benefit of using laser lithotripsy is the precise targeting of energy onto the stone with minimal tissue injury.Endoscopic laser lithotripsy is a safe and feasible treatment option for Bouveret’s syndrome.

Ureteroscopic Management of Ureteral Calculi: Pneumatic versus Holmium: YAG Laser Lithotripsy

Background: Among various intracorporeal lithotripters, pneumatic lithotripter 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. Purpose: Compare the effectiveness and complications of treatment for ureteric stones between holmium laser lithotripsy and pneumatic lithotripsy. Material and Methods: Comparison of 100 patients presented with ureteric stones, group one (50) of whom were treated with pneumatic lithotripsy and group two (50) with holmium laser was done and the effectiveness and complications of both were analyzed. Results: There was no difference in patient age, sex, stone size and location of stones between the two groups. The immediate stone free rates were 88% in the holmium: YAG group and 66% in the pneumatic lithotripsy group (p < 0.05). The four weeks stone free rates were 98% and 94% respectively (p = 0.07). The mean ± SD operative time in the holmium: YAG group (40 ± 26 min) was shorter than those with pneumatic lithotripsy group (60 ± 40 min). Postoperative stay in hospital was less than 24 hours in holmium: YAG group (70.4%) and shorter than those for pneumatic group (29.6%) (p < 0.002). Post treatment complications such as ureteral perforation were encountered in only two patients who underwent pneumatic lithotripsy. Other complications, such as mucosal injury, ureteral perforation and postoperative fever;there was no statistically significant difference between the two groups. While light hematuria was found more frequently in the pneumatic group (14%) in comparison to laser group (12%) (p = 0.02). On the other hand, the overall complication rates between the two groups was statistically significant (8%) laser group vs. (32%) pneumatic group (p = 0.003). Conclusions: Holmium: YAG laser lithotripsy was associated with shorter operation time and postoperative hospitalization period. These data suggest that holmium: YAG lithotripsy was safe and more effective than Pneumatic lithotripsy in the aspect of immediate stone free rate. We believe that holmium: YAG is an excellent treatment modality for managing ureteral calculi.

Systematic evaluation of a holmium:yttrium-aluminum-garnet laser lithotripsy device with variable pulse peak power and pulse duration

Objective:The Holmium:yttrium-aluminum-garnet(Ho:YAG)laser is the standard lithotrite for ureteroscopy.This paper is to evaluate a Ho:YAG laser with a novel effect function in vitro,which allows a real-time variation of pulse duration and pulse peak power.Methods:Two types of phantom calculi with four degrees of hardness were made for fragmentation and retropulsion experiments.Fragmentation was analysed at 5(0.5 J/10 Hz),10(1 J/10 Hz),and 20(2 J/10 Hz)W in non-floating phantom calculi,retropulsion in an ureteral model at 10(1 J/10 Hz)and 20(2 J/10 Hz)W using floating phantom calculi.The effect function was set to 25%,50%,75%,and 100%of the maximum possible effect function at each power setting.Primary outcomes:fragmentation(mm^3),the distance of retropulsion(cm);
5 measurements for each trial.Results:An increase of the effect feature(25%vs.100%),i.e.,an increase of pulse peak power and decrease of pulse duration,improved Ho:YAG laser fragmentation.This effect was remarkable in soft stone composition,while there was a trend for improved fragmentation with an increase of the effect feature in hard stone composition.Retropulsion increased with increasing effect function,independently of stone composition.The major limitations of the study are the use of artificial stones and the in vitro setup.Conclusion:Changes in pulse duration and pulse peak power may lead to improved stone fragmentation,most prominently in soft stones,but also lead to increased retropulsion.This new effect function may enhance Ho:YAG laser fragmentation when maximum power output is limited or retropulsion is excluded.

Mid-Infrared Pulsed Laser Lithotripsy with a Tunable Laser Using Difference-Frequency Generation

A novel technique of lithotripsy was investigated with a mid-infrared tunable pulsed laser using difference-frequency generation (DFG). Human gallstone samples obtained from 24 patients were analyzed with their infrared absorption spectra. It was found that the principal components of the gallstones were different for the different patients and that the gallstone samples used in this research could be classified into four groups, i.e., mixed stones, calcium bilirubinate stones, cholesterol stones, and calcium carbonate stones. In addition, some gallstone samples had different compositions within the single stone. The mid-infrared laser tunable within a wavelength range of 5.5 - 10 μm was irradiated to the cholesterol stones at two different wavelengths of 6.83 and 6.03 μm, where the cholesterol stones had relatively strong and weak absorption peaks, respectively. As the result, the cholesterol stones were more efficiently ablated at the wavelength of 6.83 μm with the strong absorption peak. Therefore, it is suggested that the gallstones could be efficiently ablated by tuning the wavelength of the laser to the strong absorption peak of the gallstones. The higher efficiency of the ablation using the characteristic absorption peaks should lead to the safer treatment without damage to the surrounding normal tissues. In order to identify the composition of the gallstones in the patients, endoscopic and spectroscopic diagnosis using the DFG laser and an optical fiber probe made with two hollow optical fibers and a diamond attenuation total reflection prism should be useful. The absorption spectrum of the gallstones in the patients could be measured by measuring the energy of the DFG laser transmitted through the optical fiber probe and by scanning the wavelength of the DFG laser.

Appropriate kidney stone size for ureteroscopic lithotripsy:When to switch to a percutaneous approach

Flexible ureteroscopy(f URS) has become a more effective and safer treatment for whole upper urinary tract stones. Percutaneous nephrolithotomy(PNL) is currently the first-line recommended treatment for large kidney stones ≥ 20 mm and it has an excellent stone-free rate for large kidney stones. However, its invasiveness is not negligible considering its major complication rates. Staged f URS is a practical treatmentfor such large kidney stones because f URS has a minimal blood transfusion risk, short hospitalization and few restrictions on daily routines. However, as the stone size becomes larger, the stone-free rate decreases, and the number of operations required increases. Therefore, in our opinion, staged f URS is a practical option for kidney stones 20 to 40 mm. Miniaturized PNL combined with f URS should be considered to be a preferred option for stones larger than 40 mm. Moreover, URS is an effective treatment for multiple upper urinary tract stones. Especially for patients with a stone burden < 20 mm, URS is a favorable option that promises a high stone-free rate after a single session either unilaterally or bilaterally. However, for patients with a stone burden ≥ 20 mm, a staged operation should be considered to achieve stone-free status.

Flexible ureteroscopic treatment of kidney stones: How do the new laser systems change our concepts?

Objective: Flexible ureteroscopy (fURS) has become a widely accepted and effective technique for treating kidney stones. With the development of new laser systems, the fURS approach has evolved significantly. This literature review aims to examine the current state of knowledge on fURS treatment of kidney stones, with a particular focus on the impact of the latest laser technologies on clinical outcomes and patient safety.Methods: We conducted a search of the PubMed/PMC, Web of Science Core Collection, Scopus, Embase (Ovid), and Cochrane Databases for all randomized controlled trial articles on laser lithotripsy in September 2023 without time restriction.Results: We found a total of 22 relevant pieces of literature. Holmium laser has been used for intracavitary laser lithotripsy for nearly 30 years and has become the golden standard for the treatment of urinary stones. However, the existing holmium laser cannot completely powder the stone, and the retropulsion of the stone after the laser emission and the thermal damage to the tissue have caused many problems for clinicians. The introduction of thulium fiber laser and Moses technology brings highly efficient dusting lithotripsy effect through laser innovation, limiting pulse energy and broadening pulse frequency.Conclusion: While the holmium:yttrium-aluminum-garnet laser remains the primary choice for endoscopic laser lithotripsy, recent technological advancements hint at a potential new gold standard. Parameter range, retropulsion effect, laser fiber adaptability, and overall system performance demand comprehensive attention. The ablation efficacy of high-pulse-frequency devices relies on precise targeting, which may pose practical challenges.

Comparison of GUF and Monte Carlo methods to evaluate task-specific uncertainty in laser tracker measurement

Measurement uncertainty plays an important role in laser tracking measurement analyses. In the present work, the guides to the expression of uncertainty in measurement(GUM) uncertainty framework(GUF) and its supplement, the Monte Carlo method, were used to estimate the uncertainty of task-specific laser tracker measurements. First, the sources of error in laser tracker measurement were analyzed in detail, including instruments, measuring network fusion, measurement strategies, measurement process factors(such as the operator), measurement environment, and task-specific data processing. Second, the GUM and Monte Carlo methods and their application to laser tracker measurement were presented. Finally, a case study involving the uncertainty estimation of a cylindricity measurement process using the GUF and Monte Carlo methods was illustrated. The expanded uncertainty results(at 95% confidence levels) obtained with the Monte Carlo method are 0.069 mm(least-squares criterion) and 0.062 mm(minimum zone criterion), respectively, while with the GUM uncertainty framework, none but the result of least-squares criterion can be got, which is 0.071 mm. Thus, the GUM uncertainty framework slightly underestimates the overall uncertainty by 10%. The results demonstrate that the two methods have different characteristics in task-specific uncertainty evaluations of laser tracker measurements. The results indicate that the Monte Carlo method is a practical tool for applying the principle of propagation of distributions and does not depend on the assumptions and limitations required by the law of propagation of uncertainties(GUF). These features of the Monte Carlo method reduce the risk of an unreliable measurement of uncertainty estimation, particularly in cases of complicated measurement models, without the need to evaluate partial derivatives. In addition, the impact of sampling strategy and evaluation method on the uncertainty of the measurement results can also be taken into account with Monte Carlo method, which plays a guiding role in measurement planning.

Developing a highly scalable synthetic strategy for 5-amino-4-nitrobenzo[1,2-c:3,4-c']bis([1,2,5]oxadiazole)1,b-dioxide(CL-18)and investigating the influence of crystal engineering and positional isomerization on its safety and laser ignition performance

5-amino-4-nitrobenzo[1,2-c:3,4-c']bis([1,2,5]oxadiazole)1,6-dioxide(CL-18)exhibits significant potential as an initiating explosive.However,its current synthesis process remains non-scalable due to low yields and safety risks.In this study,we have developed a simple and safe synthetic route for CL-18.It was synthesized from 3,5-dihaloanisole in a four-step reaction with an overall yield exceeding 60%,surpassing all reported yields in the literature.Subsequently,recrystallization of CL-18 was successfully achieved by carefully selecting appropriate solvents and antisolvents to reduce its mechanical sensitivity.Ultimately,when DMF-ethanol was employed as the recrystallization solvent system,satisfactory product yield(>90%)and reduced mechanical sensitivity(IS=15 J;FS=216 N)were obtained.Additionally,CL-18 is derived from the rearrangement of oxygen atoms on i-CL-18 furoxan,and a comparative analysis of their physicochemical properties was conducted.The thermal stability of both compounds is similar,with onset decomposition temperatures recorded at 186 and 182℃respectively.Similarly,they exhibit 5 s breaking point temperatures of 236 and 237℃.Additionally,we present novel insights into the positional-isomerization-laser-ignition performance of CL-18 and its isomer i-CL-18 using laser irradiation for the first time.Remarkably,our findings demonstrate that i-CL-18 exhibits enhanced laser sensitivity,as it can be directly ignited by a 1064 nm wavelength laser,whereas CL-18 lacks this characteristic.

Optimized air-ground data fusion method for mine slope modeling

Refined 3D modeling of mine slopes is pivotal for precise prediction of geological hazards.Aiming at the inadequacy of existing single modeling methods in comprehensively representing the overall and localized characteristics of mining slopes,this study introduces a new method that fuses model data from Unmanned aerial vehicles(UAV)tilt photogrammetry and 3D laser scanning through a data alignment algorithm based on control points.First,the mini batch K-Medoids algorithm is utilized to cluster the point cloud data from ground 3D laser scanning.Then,the elbow rule is applied to determine the optimal cluster number(K0),and the feature points are extracted.Next,the nearest neighbor point algorithm is employed to match the feature points obtained from UAV tilt photogrammetry,and the internal point coordinates are adjusted through the distanceweighted average to construct a 3D model.Finally,by integrating an engineering case study,the K0 value is determined to be 8,with a matching accuracy between the two model datasets ranging from 0.0669 to 1.0373 mm.Therefore,compared with the modeling method utilizing K-medoids clustering algorithm,the new modeling method significantly enhances the computational efficiency,the accuracy of selecting the optimal number of feature points in 3D laser scanning,and the precision of the 3D model derived from UAV tilt photogrammetry.This method provides a research foundation for constructing mine slope model.

Highly Defective Dark TiO_(2) Modified with Pt: Effects of Precursor Nature and Preparation Method on Photocatalytic Properties

The study focused on the modification with platinum of dark defective titania obtained via pulsed laser ablation. Both the method of Pt introduction and the nature of the Pt precursor were varied. All samples exhibited similar phase compositions, specific surface areas, and Pt contents. High-resolution transmission electron microscopy coupled with pulsed CO adsorption revealed increased dispersity when photoreduction and the hydroxonitrate complex (Me _(4) N) _(2) [Pt _(2) (OH) _(2) (NO _(3) ) _(8) ] were used. The sample featured a high content of single-atom species and subnano-sized Pt clusters. The X-ray photoelectron spectroscopy results showed that the photoreduction method facilitated the appearance of a larger number of Pt ^(2+) states, which appeared owing to the strong metal-support interaction (SMSI) eff ect of the transfer of electron density from the electron-saturated defects on the TiO _(2) surface to Pt ^(4+) . In the hydrogen evolution reaction, samples with a significant fraction of the Pt ^(2+) ionic component, capable of generating short-lived Pt^(0) single-atom sites under irradiation due to the SMSI eff ect, exhibited the highest photocatalytic activity. The 0.5Pt(C)/TiO_(2) -Ph sample exhibited the highest hydrogen yield with a quantum efficiency of 0.53, retaining its activity even after 8 h of operation.

Which treatment protocol, among classical methods and/or various laser applications is the most effective in root canal disinfection, <i>in vitro</i>? A systematic review

Purpose: The aim of this systematic review was to answer the question “Which treatment protocol, am- ong classical methods and/or various laser applica- tions is the most effective in root canal disinfection, in vitro”. Materials and Methods: A MEDLINE, a Co- chrane and an Embase search (three specified search- es) were conducted to identify randomized controlled trials (RCT) until June 2010, conducted on human teeth and published in English, German or French language, examining the root canal disinfection after the use of lasers with or without mechanical instru-mentation. Additionally, hand search was conducted and contact with authors, when needed. Results: The MEDLINE, the Cochrane and the EMBASE search identified 240, 28, and 35 published articles, respec-tively. Ten articles from the MEDLINE and 5 articles from the Cochrane search (that were also identified in the MEDLINE search) met the inclusion and va-lidity assessment criteria. In E. faecalis elimination, instrumentation of the root canal and diode laser/665 nanometer/1 Watt (diode laser/665 nm/1 W) irradia-tion with the combined effect of Methylene Blue (MB) as photosensitizing agent (logCFU/ml = 1636) seemed to be the best method. In P. aeruginosa and in A.naeslundii elimination, instrumentation of the root canal followed by irrigation with 5, 25% NaOCl (log-CFU/ml = 0) seemed to be the best method. In gen-eral, instrumentation of the root canal followed by irrigation with 5, 25% NaOCl (logCFU/ml = 0) and instrumentation of the root canal and Er: YAG laser/ 2940 nm/0.8 W irradiation (logCFU/ml = 1924) seemed to be the best (polymicrobial studies). Conclusions: There are treatment protocols with the assistance or not of laser irradiation that can eliminate E. faecalis, E. coli and S. aureus inside the root canal. However, there is a serious number of S. anginosus, F. nuclea-tum, A. naeslundii and P. aeruginosa that remain in-side the root canal even after laser irradiation. New research is needed in order to set a treatment proto-col effective in the root canal disinfection from all bac-teria that are related to endodontic origin pathology.

Ureteroscopic lithotripsy using holmium laser for 187 patients with proximal ureteral stones

Background Improving the success rate of ureteroscopic lithotripsy for proximal ureteral stones is the hot issue in this field. Here we reported our experience on the treatment of proximal ureteral stones.Methods From 2005 to 2010, 187 consecutive patients with proximal ureteral stones who underwent ureteroscopic lithotripsy were enrolled. The initial 52 patients treated by semi-rigid ureteroscope alone were classified as group 1. The subsequent 135 patients treated by semi-rigid ureteroscope with the aid of stone basket and flexible ureteroscope were classified as group 2.Results In group 1, the overall stone-free rate was 67.3%. By a single procedure of ureteroscopic lithotripsy using a semi-rigid instrument, patients with ureteral stones below the 4th lumbar vertebra level achieved 91.7% stone-free rate, which was only 50% in patients with stones above the 4th lumbar vertebra level. Conversion to open surgery occurred in two patients since ureteral perforation was observed. In group 2, the stone-free rate achieved 93.2% with the aid of an N-Trap basket, which was significantly higher than that of patients without the aid of the basket （51.6%）. Flexible ureteroscope was subsequently used in patients with fragment migration, thus making the overall success rate in group 2 increases to 97.0%.Conclusions Ureteroscopic lithotripsy is a safe and efficacious treatment for proximal ureteral stones. A single procedure of ureteroscopic lithotripsy using semi-rigid ureteroscope could achieve a satisfactory stone-free rate in patients with proximal ureteral stones below the 4th lumbar vertebra level. However, patients with ureteral stones above the 4th lumbar vertebra level experienced higher stone-migration rate, which would decrease the success rate. Fortunately, the stone-free state could possibly be achieved with the aid of an N-trap basket and flexible ureteroscope.

Thermal effect of holmium laser lithotripsy under ureteroscopy

To the Editor: Ureteral calculus is a common urological disease. In recent years, one of the main treatment methods is ureteroscopy with holmium laser lithotripsy. However, with the extensive application of holmium laser lithotripsy, the increasing incidence of postoperative ureteral stricture or even occlusion has attracted the attention of clinicians to its etiology. The issue of the intraoperative holmium laser thermal effect has also gradually gained attention. The holmium laser is a long-wavelength pulsed laser, which crushes calculi by an optomechanical/photoacoustic mechanism as well as a photothermal mechanism, and it is mainly based on the photothermal mechanism.[1] Currently, multiple in vitro studies worldwide have confirmed that the holmium laser did increase the water temperature in the working area. However, these studies only simulated the lithotripsy process of the holmium laser in vitro, which did not completely reflect the thermal effect of the holmium laser during an actual operation. Accordingly, this study monitored the temperature changes of the lavage fluid in the operative field during the actual holmium laser lithotripsy process under an ureteroscope, with the aim of providing more information for the etiology study of ureteral stricture after ureteroscopy with holmium laser lithotripsy.

Determination of energy coupling to material in laser welding by a novel “sandwich” method

A mathematical energy coupling model was developed to analyze the light transmission in the keyhole and energy distribution on the keyhole wall.The main characteristics of the model include：1） a prototype of the keyhole and the inverse Bremsstrahlung absorption coefficient in the keyhole plasma are obtained from the experiments;2） instead of using a parallel incident beam,a focused laser beam with real Gaussian intensity distribution is implemented;3） both Fresnel absorption and inverse Bremsstrahlung absorption during multiple reflections are considered.The calculation results show that the distribution of absorbed laser intensity by the keyhole wall is not uniform.The maximum laser energy is absorbed by the bottom of the keyhole,although no rays irradiate directly onto the bottom.According to analysis of beam focusing characteristics,the location of the focal plane plays a more important role in the laser energy absorption by the front wall than by the rear wall.

Supervised descent method for weld pool boundary extraction during fiber laser welding process

In order to obtain a high-quality weld during the laser welding process, extracting the characteristic parameters of weld pool is an important issue for automated welding. In this paper, the type 304 austenitic stainless steel is welded by a 5 kW high-power fiber laser and a high-speed camera is employed to capture the topside images of weld pools. Then we propose a robust visual-detection approach for the molten pool based on the supervised descent method. It provides an elegant framework for representing the outline of a weld pool and is especially efficient for weld pool detection in the presence of strong uncertainties and disturbances. Finally, welding experimental results verified that the proposed approach can extract the weld pool boundary accurately, which will lay a solid foundation for controlling the weld quality of fiber laser welding process.