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 diameters

The Effect of High- and Low-power Holmium Laser Settings for Transurethral Lithotripsy in the Management of Adults with Ureteral Stone

Since there is insufficient evidence to determine the best treatment of transurethral laser lithotripsy (TLL) in ureteral stones, this study compared the effectiveness and safety of TLL using high-power (HP) (100 W) and low-power (LP) (20 W) laser settings. All patients with maximally sized ureteral stones who were planned for transurethral holmium laser lithotripsy were enrolled in this open study. One of the two laser setting groups-LP or HP-was allocated to each alternate patient. Using IBM SPSS Statistics 24, the treatment groups were compared for operating time, intraoperative and postoperative problems (up to 1 year), and rates of stone-free recovery. Welch tests were employed to compare continuous data, whereas Fisher's exact or Chi-square tests were used to assess categorical variables. At P < 0.05, statistical significance was established. A total of 207 individuals were included and preoperative data were comparable between the two groups. The HP group had a considerably greater ablation rate and a significantly shorter procedure duration (42.61 ± 11.74 min) than the LP group (78.56 ± 25.91 min) ( P = 0.025). The Overactive Bladder Symptom Score and International Prostate Symptom Score were considerably higher in the HP group than in the LP group. Treatment effectiveness was considerably impacted by the location of the ureteral stone, according to univariate and multivariate logistic regression models. A HP laser setting of up to 100 W greatly shortens the duration of the process for treating ureteral stones without raising the risk of problems.

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.

Use of artificial stones in training and laboratory studies, have we found the right material? Outcomes of a systematic review from the European School of Urology

Objective

In this review, we investigated the current literature to find out which artificial stones (AS) are available in endourology, and in which experimental and training schemes they are used.

Materials and Methods

A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Twenty-one out of 346 studies met our inclusion criteria and are presented in the current review. The inclusion criteria were the existence of AS and their use for laboratory and training studies.

Results

There is a wide variety of materials used for the creation of AS. BegoStone powder (BEGO USA, Lincoln, Rhode Island) and plaster of Paris™ were used in most of the studies. In addition, Ultracal-30 (U. S. Gypsum, Chicago, IL) was also used. Other materials that were used as phantoms were AS created from plaster (Limbs and Things, UK), standardized artificial polygonal stone material (Chaton 1028, PP13, Jet 280; Swarovski), model stones consisting of spheres of activated aluminum (BASF SE, Ludwigshafen am Rhein, Deutschland), Orthoprint (Zhermack, Badia Polesine, Italy), and a combination of plaster of Paris, Portland cement, and Velmix (calcium sulfate powder). Many experimental settings have been conducted with the use of AS. Our research demonstrated nine studies regarding testing and comparison of holmium: yttrium-aluminum-garnet laser devices, techniques, and settings. Six studies were about extracorporeal shock wave lithotripsy testing and settings. Three experiments looked into treatment with percutaneous nephrolithotomy. Additionally, one study each investigated imaging perioperatively for endourological interventions, stone bacterial burden, and obstructive uropathy.

Conclusion

AS have been used in a plethora of laboratory experimental studies. Independent of their similarity to real urinary tract stones, they present a tremendous potential for testing and training for endourological interventions.

Holmium: Yttrium-aluminum-garnet laser lithotripsy: Is there a difference in ablation rates between short and long pulse duration?

Introduction

The high-power holmium: yttrium-aluminum-garnet lasers provide a wide variety of settings for stone disintegration. The aim of this in vitro study is to evaluate the effect of short and long pulse duration on ablation rates on urinary stones.

Materials and Methods

Two types of artificial stones were created by BegoStone™ with different compositions (15:3 and 15:6, stone/water ratio). Stones with a 15:3 and 15:6 powder-to-water ratio were defined as hard and soft stones, respectively. Lithotripsy was performed with different laser settings using a custom-made in vitro model consisting of a 60 cm long and 19 mm diameter tube. The ablation rate is defined as the final total mass subtracted from the initial total mass and divided to the time of treatment. Stone ablation rates were measured according to different laser settings with total power of 10W (0,5J-20 Hz, 1J-10 Hz, 2J-5 Hz) and 60W (1J-60 Hz, 1,5J-40 Hz, 2J-30 Hz).

Results

Higher pulse rates and higher total power settings were related to higher ablation rates. Short pulse duration was more effective on soft stones, whereas long pulse duration was more effective on hard stones. For the same power settings, the highest energy-lowest frequency combination resulted in higher ablation rate in comparison to the lowest energy-higher frequency combination. Finally, short and long pulse average ablation rates do not differ so much.

Conclusion

Regardless of the stone type and pulse duration, utilization of higher power settings with higher energies increased the ablation rates. Higher ablation rates were demonstrated for hard stones using long pulse duration, and for soft stones with short pulse duration.

Preliminary experience in endoscopic section of posterior urethral valves using the Holmium: YAG laser

INTRODUCTION

Refinements in endoscopic instrumentation, the widespread popularization of endourology and the minimal invasiveness of endoscopic approaches have led to evolving interest in expanding applications for their use and now include incision of posterior urethral valves (PUV). We aimed to report our paediatric experience of PUV incision with Holmium:YAG laser updating of the endoscopic technique, how we set parameters for the laser energy and provide some tips and tricks to increase the likelihood of completing treatment.

METHODS

A monocentric, prospective, continuous series of boys with PUV were treated endoscopically using a Holmium: YAG laser (1.2 J, 20 Hz, 800 μs). Feasibility was evaluated using operative time in minutes, spontaneous normal micturition after bladder catheter removal, and the duration of bladder catheterization in days in the absence of satisfactory micturition. Peri-operative complications were recorded. A VCUG was performed at 6 weeks postoperatively to exclude residual valves.

RESULTS

Since September 2018, 18 children with PUV were included. The median age at the time of endoscopic laser incision was 12 days (1 day-5 years). The median operative duration was 28 min (17-35). The urinary catheter was systematically removed on the first postoperative day. There were no intraoperative or anaesthesia-related complications. More specifically, no urethral injuries and no bleeding were recorded. No incomplete VUP incision was found on follow-up VCUG, and no endoscopic revision was necessary thus far, with a median follow-up of 44 months (6 months-60 months).

DISCUSSION

The use of the Holmium: YAG laser introduces new perspectives in the treatment of PUV. Its mechanism of action is considered a photothermic effect with a vapourization effect. The laser energy released by the Holmium: YAG source has a short tissue penetration distance and is strongly absorbed in an aqueous environment and therefore limits thermal tissue damage and favours early tissue re-epithelialization, reducing the risk of urethral stricture and decreasing postoperative oedema. The use of the laser in "incision" mode is the setting that most solicits the capacities of the laser (high energy, high frequency, and long pulse). The use of laser energy has the advantage of allowing tissue vapourization while ensuring maximal haemostasis and the possibility of introducing the laser fibre through the working channels of small, 6-Fr paediatric endoscopes.

CONCLUSION

In our experience, endoscopic PUV incision using the Holmium: YAG laser appears to be a safe and efficient technique.

Comparison of low power and high power holmium YAG laser settings in flexible ureteroscopy

PURPOSE

To compare the efficacy of conventional low power and high power holmium: yttrium aluminum-garnet (Ho: YAG) laser lithotripsy settings during retrograde intrarenal surgery (RIRS).  METHODS: The prospective study was conducted in patients undergoing RIRS for renal stones less than 2 cm diameter. Pulsed Ho:YAG laser (Lumenis^® Pulse TM P120 H) was used for laser lithotripsy and the patients were randomized into low power (LP) and high power (HP) laser lithotripsy settings groups. The lasing duration, total laser energy used (Joules), laser energy used to ablate 1 mm³ of stone (Joules/mm³), operative duration, stone ablation speed (mm³/s) and stone free rate were compared.

RESULTS

A total of 120 underwent RIRS with 63 and 57 patients in LP and HP group, respectively. Median stone volume and stone density were comparable between the groups. The total energy used and laser energy used to ablate 1mm³ of stone (Joules/mm³) were significantly higher in the HP group than in LP group (27.9 (16.4-46.2) J/ mm³ vs 9.7 (5.3-17.7) J/ mm³) (p < 0.01). Median (IQR) ablation speed were 0.8 (0.5-1.3) mm³/s and 0.6 (0.4-1) mm³/s in the LP and HP groups, respectively. The median lasing time, operative time and stone free rate were similar in both the groups.

CONCLUSION

The total energy used and J/mm³ were lower in the LP group than in HP group with similar lasing duration, operative duration, ablation speed and stone free rate for renal stones less than 2 cm.

Moses 2.0 for High-Power Ureteroscopic Stone Dusting: Clinical Principles for Step-by-Step Video Technique

Introduction: We present our initial experience using the Moses 2.0 system for flexible-ureteroscopy (f-URS) high-frequency renal stone dusting, including a step-by-step video guide of our clinical principles for dusting technique. Materials and Methods: Twelve consecutive patients undergoing f-URS with Moses 2.0 (Lumenis) for a single renal stone by a single surgeon at an ambulatory center were reviewed. Stone-free rates (SFRs) and Clavien grade complications were assessed. Operative steps with illustrative examples are provided in an accompanying video. Results: Mean (range) stone size and lithotripsy time were 10.4 (5.3-17.2) mm and 15.0 (5-26) minutes, respectively. Complete SFR and <2 mm residual fragments were 82% and 18%, respectively. One patient had a Clavien Grade 1 complication. Operative steps reviewed include instrumentation, stone control, laser settings, and stent omission criteria. The preferred laser settings for renal stone dusting were 0.2-0.3 J and 100-120 Hz. Limitation of this early experience study is the small sample size. Larger studies are needed to confirm our initial findings. Conclusions: Early experience of Moses 2.0 for f-URS renal stone dusting demonstrated effective and efficient laser lithotripsy in patients with renal stones <2 cm.

Efficacy of one-surgeon basketing technique for stone extraction during flexible ureteroscopy for urolithiasis

Objective: To evaluate the safety and efficacy of using one-surgeon basketing technique by a solo surgeon for stone extraction during flexible ureteroscopy (f-URS) for urolithiasis.

Patients and methods: This retrospective study enrolled patients with urinary calculus who underwent f-URS at two institutions in Japan between September 2014 and March 2020. A total of 100 patients were operated by one experienced surgeon using the one-surgeon basketing technique. With this approach, the f-URS apparatus was manipulated with the non-dominant hand and the basket catheter was manipulated with the dominant hand. We retrospectively examined the perioperative results, complications, and stone-free rate [with ‘stone free’ defined as ≤2 mm with kidney–ureter–bladder (KUB) at 1 month after f-URS] to estimate the safety and efficacy for comparison with the results of conventional retrieval basketing technique.

Results: Among our study population, the median stone size was 14 mm and median operative time was 74 min. A stone-free status was achieved in 91 patients (91%). The median stone fragmentation time was 15 min and stone retrieval time was 30 min. All included patients were treated using the one-surgeon basketing technique. Complications related to stone retrieval were identified in two patients (2%); the degree of ureteral injury was classified as Clavien–Dindo Grade IIIa.

Conclusion: The one-surgeon basketing technique is safe and effective for the extraction of stone fragments during f-URS for urolithiasis. This technique does not require assistance for basketing; therefore, f-URS with active retrieval basketing can be completed by a solo surgeon.

Abbreviations: BMI: body mass index; KUB: kidney–ureter–bladder; SFR: stone-free rate; UAS: ureteral access sheath; f-URS: flexible ureteroscopy

Impact of Pulse Mode on Dusting Effect for Holmium Laser Lithotripsy: In Vitro Evaluation With Calcium Oxalate Monohydrate Stones

OBJECTIVE

To assess the distribution of stone fragments (<0.25->2 mm) after in vitro dusting laser lithotripsy with varying pulse modes using canine calcium oxalate monohydrate (COM) stones. Recent work demonstrates that fragments <0.25 mm are ideal for dusting, and we hypothesized advanced pulse modes might improve this outcome.

METHODS

A 3D-printed bulb was used as a calyceal model containing a single COM stone. A 230-core fiber (Lumenis) was passed through a ureteroscope (LithoVue, Boston Scientific). Contact laser lithotripsy by a single operator was performed with dusting settings (0.5J x 30Hz; Moses Pulse120H) to deliver 1kJ of energy for each trial. Short pulse (SP), long pulse (LP), Moses Distance (MD) and Moses Contact (MC) modes were tested with 5 trials for each parameter. Primary outcome was mass of fragments <0.25, <0.5, <1, and <2 mm. Laser fiber tip degradation was measured using a digital caliper.

RESULTS

Mass of stone fragments <0.25 mm varied from 34.6%-43.0% depending on the pulse mode, with no statistically significant differences between modes. MC (98.5%) produced a greater mass of fragments <2 mm compared to LP (86.1%; P = .046) but not SP (92.0%). Significantly less fiber tip burnback occurred with MC (0.29 mm) and MD (0.28 mm), compared to SP (0.83 mm; P < .0005).

CONCLUSION

Regardless of pulse mode, greater than one-third of the mass of COM stone was reduced to fragments <0.25 mm following contact laser lithotripsy. MC produced a greater mass of fragments <2 mm compared to LP and demonstrated less fiber tip burnback compared to SP.

Efficacy of various laser devices on lithotripsy in retrograde intrarenal surgery used to treat 1-2 cm kidney stones: A prospective randomized study

AIMS

To compare the efficacy of different laser devices and power ranges on lithotripsy in retrograde intrarenal surgery (RIRS) for 1-2 cm kidney stones.

METHODS

A total of 223 participants undergoing RIRS for 1-2 cm kidney stones at our clinic between January 2015 and January 2017 were recruited for this prospective study (NCT02451319). Two hundred and four participants included in our study were randomly allocated into either ≤20 W with 20 W laser device (group 1) or ≤20 W with 30 W laser device (group 2) or >20 W with 30 W laser device (group 3).

RESULTS

There was no significant difference between the groups in terms of demographic and stone characteristics. Operation and fluoroscopy times were significantly longer (P = .003 and P < .001, respectively) and stone-free rate (SFR) was significantly lower in group 1 (P = .002). Complications were similar in all three groups (P = .512). However, post-operative pain scores were significantly higher in group 1 (P < .001). The multivariate analysis revealed that stone size (95% CI: 0.654-0.878, OR = 0.758, P < .001), ureteral access sheath use (95% CI: 1.003-20.725, OR = 4.560, P = .049), and lithotripsy with 30 W laser device (95% CI: 1.304-11.632, OR = 3.895, P = .015; 95% CI: 1.738-17.281, OR = 5.480, P = .004, groups 2 and 3, respectively) were independent factors predicting SFR for RIRS used in 1-2 cm kidney stones.

CONCLUSION

The 30 W laser device used in RIRS for 1-2 cm kidney stones had shorter operation times, higher SFRs, and lower post-operative pain scores compared with the 20 W device. The 30 W laser device is safe and more efficient in RIRS for treatment of 1-2 cm kidney stones.

The impact of lasers in percutaneous nephrolithotomy outcomes: results from a systematic review and meta-analysis of randomized comparative trials

Background Percutaneous nephrolithotomy (PCNL) is the first choice treatment of renal stones larger than 2 cm. We aimed to evaluate if lasers perform as equal as non-laser devices in patients with kidney stones candidate to PCNL. Materials and methods A comprehensive literature search was performed in MEDLINE via PubMed, Scopus and Cochrane Central Register of Controlled Trials (CENTRAL) to assess the differences in the perioperative course, incidence of postoperative complications, and stone free-rate (SFR) in patients with kidney stones undergoing laser versus non-laser PCNL in randomized studies. The incidences of complications were pooled using the Cochran-Mantel-Haenszel Method with the random effect model and expressed as Risk Ratios (RR), 95% Confidence Intervals (CI), and p-values. Surgical time and length of stay were pooled using the inverse variance of the mean difference (MD) with a random effect, 95% CI, and p-values. Analyses were two-tailed, with a significance set at p ≤0.05. Results Six papers including 732 patients (311 patients undergoing holmium laser and 421 non-laser PCNL) were included in meta-analysis. Surgical time and postoperative stay were shorter in the non-laser group (MD:11.14, 95% CI:2.32-19.96, p=0.002; MD:-0.81, 95%CI:-2.18-0.57 p=0.25, respectively). SFR was significantly higher in the non-laser group (RR:1.08, 95% CI:1.01-1.15, p=0.03). Patients undergoing laser PCNL had a non-significant higher risk of postoperative fever >38°C (RR:0.64, 95%CI: .31-1.30, p=0.22). Transfusion rate did not differ between the two groups (RR:1.02, 95% CI:0.50-2.11 p=0.95). The need for stent positioning due to urine extravasation was higher risk in the laser group but the difference did not reach significance (RR:0.49, 95% CI:0.17-1.41 p=0.19). Conclusions Non-laser PCNL showed better perioperative outcomes and SFR as compared to holmium laser PCNL.

Histogram of kidney stones on non-contrast computed tomography to predict successful stone dusting during retrograde intrarenal surgery

PURPOSE

To predict successful dusting of kidney stones during retrograde intrarenal surgery (RIRS) using stone density parameters and histograms measured with non-contrast computed tomography imaging.

METHODS

Medical records of 49 patients who underwent retrograde intrarenal surgery between January 2018 and January 2019 at Kyung Hee University Hospital were reviewed, and the data of 55 stones were evaluated. Patient age, sex, mean stone density, the highest and lowest measured Hounsfield unit (HU), standard deviation and range of the measured HUs, volume of the most measured HU, and success of dusting were evaluated. Histograms of the measured HUs were created and cutoff values for successful dusting were analyzed.

RESULTS

Thirty-two stones were successfully dusted during surgery. Dusted stones had a wider range of HU and higher standard deviation. The volume of the most measured HU was smaller in the dusted stones. Successful dusting could be predicted when the volume of the most measured HU was < 8.9 mm³, with range ≥ 853, or when the volume of the most measured HU was < 8.9 mm³, with range < 853, and the mean stone density was < 355. The histograms of HUs of the dusted stones were wide and rugged, while those of dusting failed stones were narrow and peaked.

CONCLUSION

Evaluation of stone HU histograms showed differences in distribution and proportion. This will help predict surgical outcomes and prepare for intraoperative complications.

Feasibility and long-term safety of Ho:YAG laser lithotripsy in broncholithiasis patients

BACKGROUND

Treatment of broncholithiasis is complex, especially in the case of a large or transbronchial broncholith. Holmium-yttrium aluminum garnet (Ho:YAG) laser lithotripsy may be a useful treatment in broncholithiasis; however, as it is not yet common practice, the optimal parameters are unknown.

METHODS

We performed a single-center retrospective analysis of the clinical data of 13 broncholithiasis patients who underwent Ho:YAG laser lithotripsy from May 2012 to October 2018.

RESULTS

For the 13 patients (2 males and 11 females), Ho:YAG laser lithotripsy was performed 17 times, in total. All procedures were performed under general anesthesia with rigid bronchoscopy. We initially set the Ho:YAG laser to a pulse frequency of 5 Hz and a pulse energy of 0.8 J, gradually increasing these as required. The pulse frequency range we employed was 5-15 Hz, and the pulse energy range was 0.8-1.6 J. All broncholiths were successfully extracted after lithotripsy, and all symptoms improved. Hemoptysis, bronchial esophageal fistula, and pneumonia were the most common complications; however, there were no long-term complications.

CONCLUSIONS

Ho:YAG laser lithotripsy is an effective and safe treatment for broncholithiasis, over a long-term follow up.

A prospective evaluation of high- and low-power holmium laser settings for transurethral lithotripsy in the management of adults with large bladder calculi

PURPOSE

To prospectively investigate the efficacy and safety of high-power (100 W) vs low-power (20 W) laser settings for transurethral laser lithotripsy in the management large vesical calculi (> 4 cm).

METHODS

All patients with vesical calculi > 4 cm in the maximum dimension and scheduled for transurethral holmium laser lithotripsy were invited to participate in the study. Every alternate patient was treated with either the low- or high-power laser settings. We used a continuous irrigation resectoscope with laser bridge or a laser working element (Karl Storz) for laser lithotripsy of bladder stones. We compared the operative time, intra-operative/post-operative complications (up to 1 year), and stone-free rates between the treatment groups using IBM SPSS Statistics 24 software. Comparisons between treatment groups for continuous variables were assessed using the Welch test, while categorical variables were compared with either the Chi-square or Fisher's exact test. A p value < 0.05 was considered statistically significant.

RESULTS

Twenty patients with ten in each cohort were recruited. Preoperative data and mean bladder stone size were comparable in both groups. The duration of surgery was significantly reduced from 70.80 ± 25.28 min in low-power cohort to 40.90 ± 15.01 min in the high-power group (p = 0.005). There were no significant intra-operative complications in either group. All patients were stone-free following the procedure.

CONCLUSION

High-power laser setting of up to 100 W results in a significant reduction in duration of surgery without any increase in the complication rate for treatment of large bladder stones.

Consultation on kidney stones, Copenhagen 2019: aspects of intracorporeal lithotripsy in flexible ureterorenoscopy

Purpose

To summarize current knowledge on intracorporeal laser lithotripsy in flexible ureterorenoscopy (fURS), regarding basics of laser lithotripsy, technical aspects, stone clearance, lithotripsy strategies, laser technologies, endoscopes, and safety.

Methods

A scoping review approach was applied to search literature in PubMed, EMBASE, and Web of Science. Consensus was reached through discussions at the Consultation on Kidney Stones held in September 2019 in Copenhagen, Denmark.

Results and conclusions

Lasers are widely used for lithotripsy during fURS. The Holmium laser is still the predominant technology, and specific settings for dusting and fragmenting have evolved, which has expanded the role of fURS in stone management. Pulse modulation can increase stone ablation efficacy, possibly by minimizing stone retropulsion. Thulium fibre laser was recently introduced, and this technology may improve laser lithotripsy efficiency. Small fibres give better irrigation, accessibility, and efficiency. To achieve optimal results, laser settings should be adjusted for the individual stone. There is no consensus whether the fragmentation and basketing strategy is preferable to the dusting strategy for increasing stone-free rate. On the contrary, different stone scenarios call for different lithotripsy approaches. Furthermore, for large stone burdens, all laser settings and lithotripsy strategies must be applied to achieve optimal results. Technology for removing dust from the kidney should be in focus in future research and development. Safety concerns about fURS laser lithotripsy include high intrarenal pressures and temperatures, and measures to reduce both those aspects must be taken to avoid complications. Technology to control these parameters should be targeted in further studies.

Lasers for stone treatment: how safe are they?

PURPOSE OF REVIEW

To update laser lithotripsy advances in regard to new laser types and technologies as well as review contemporary laser safety concerns.

RECENT FINDINGS

The high prevalence of urolithiasis and the continuing miniaturization of scopes has encouraged the growth of laser lithotripsy technology. The holmium:yttrium-aluminum-garnet (Ho:YAG) laser has been used for over 20 years in endourology and has been extensively studied. Holmium laser power output is affected by a number of factors, including pulse energy, pulse frequency, and pulse width. Several recent experimental studies suggest that the new dual-phase Moses 'pulse modulation' technology, introduced in high-power laser machines, carries a potential to increase stone ablation efficiency and decrease stone retropulsion. A newly introduced thulium fiber laser (TFL) has been adapted to a very small laser fiber size and is able to generate very low pulse energy and very high pulse frequency. Both of these technologies promise to play a larger role in laser lithotripsy in the near future. However, more experimental and clinical studies are needed to expand on these early experimental findings. Even though laser lithotripsy is considered safe, precautions should be taken to avoid harmful or even catastrophic adverse events to the patient or the operating room staff.

SUMMARY

The Ho:YAG laser remains the clinical gold standard for laser lithotripsy for over the last two decades. High-power Ho:YAG laser machines with Moses technology have the potential to decrease stone retropulsion and enhance efficiency of laser ablation. The new TFL has a potential to compete with and perhaps even replace the Ho:YAG laser for laser lithotripsy. Safety precautions should be taken into consideration during laser lithotripsy.

Effect of temporal pulse shape on urinary stone phantom retropulsion rate and ablation efficiency using holmium:YAG and super-pulse thulium fibre lasers

OBJECTIVE

To investigate the effects of laser temporal pulse shaping of the super-pulse thulium fibre laser (SPTFL) and to compare these in controlled in vitro conditions with various holmium: yttrium aluminium garnet (Ho:YAG) pulse delivery modes.

MATERIALS AND METHODS

The SPTFL (Urolase SP, IRE-Polus, Fryazino, Russia), with an emission wavelength of 1.94 μm, and a Ho:YAG laser (P120H; Lumenis, Yokneam, Israel) with Moses technology were compared. Pulse shape, stone retropulsion and ablation efficiency were evaluated using BegoStones and compared for each laser mode: short (SP), long (LP), and Moses pulse (MP) for Ho:YAG, regular pulse (RP) and dual pulse (DP) for SPTFL.

RESULTS

The Ho:YAG SP mode exhibited an asymmetrical pulse shape, with a steep leading slope and a much more gradual trailing slope, without any flat section. Pulses generated by the SPTFL were significantly longer and therefore had lower peak power than those generated by the Ho:YAG laser at equivalent energy settings. Retropulsion for the holmium:YAG LP and MP modes was similar and lower than that for the SP mode, but higher than for the SPTFL (all P ≤ 0.02), with an average stone displacement approximately four times and two times lower for SPTFL as compared to the Ho:YAG laser. Comparison of ablation volumes indicated that the SPTFL induced significantly higher (twofold) ablation than the Ho:YAG laser.

CONCLUSIONS

The magnitude and initial velocity of stone retropulsion decreased with longer pulse duration and lower pulse peak power, without sacrificing ablation efficiency. These observations are manifest when comparing the Ho:YAG laser with the SPTFL. The novel SPTFL provides greater versatility and control of pulse variables than the Ho:YAG laser. Further clinical investigation of practical benefits achievable with pulse-shaping SPTFL modes is warranted.

Optimal settings for the Holmium: YAG laser in pediatric endourology: Tips and tricks

INTRODUCTION

To the best of our knowledge, no pediatric paper has been published regarding specifically how to set the Holmium:YAG laser for multiple urologic applications.

OBJECTIVE

To provide insight into the laser parameters for pediatric applications.

STUDY DESIGN

We describe the principle and the settings of the laser.

RESULTS

The Holmium:YAG laser can produce four different biological effects: (1) fragmentation of stones in small fragments that can be retrieved with grasping instruments, thereby increasing the immediate stone-free outcome. For fragmentation lithotripsy, the laser has to be set with a high energy, low frequency and short pulse duration; (2) dusting which produces fine dust that can spontaneously evacuate, avoiding the use of basket retrieval. The dusting setting requires low energy, high frequency and long pulse duration; (3) incision of posterior urethral valves or ureterocele when all settings are maximized: high energy, high frequency and long pulse duration; (4) coagulation of urothelial tumors using high frequency, long pulse duration and slightly lower energy than required for incision.

DISCUSSION

Both dusting by painting and fragmentation with retrieval for ureteroscopic laser lithotripsy are effective. Although dusting tends to be associated with shorter operative times and a lower risk of ureteral trauma, this approach has a potential risk of recurrent stone formation from dust failing to pass. In contrast, fragmentation with extraction may provide for a more immediate postoperative stone-free result. Altering the pulse energy, frequency, width and modulation can help to optimize lithotripsy efficiency. Lower pulse energy settings result in smaller fragments, less retropulsion and reduce fiber tip degradation. A shallow depth of penetration in water and tissue allows precise energy application and provides a margin of safety.

CONCLUSION

An understanding of Ho-YAG laser settings will permit the pediatric surgeon to make a better use of the device for different urological applications.

Ho: YaG laser lithotripsy: recent innovations

PURPOSE OF REVIEW

The aim of this study was to summarize the recent innovations of the holmium laser with special respect to lithotripsy. Therefore, we reviewed and discussed the most recent and pivotal publications on this topic.

RECENT FINDINGS

The current literature underlines Holmium:yttrium-aluminium-garnet (Ho:YAG) lithotripsy as a well tolerated and efficient method to treat urinary calculi. Because of modifiable adjustments of pulse energy, pulse frequency, and pulse length, especially with newer generations of holmium lasers, urologists can accurately choose between the 'fragmentation' and 'dusting' technique with its alterations. Recently, the 'Moses mode' as a new feature incorporated in the Lumenis Pulse P120H holmium laser showed less retropulsion with higher rates of stone ablation because of an improved energy transmission from the laser fiber towards the targeted calculus in in-vitro studies.

SUMMARY

Based on technological developments, Ho:YAG laser lithotripsy has become more efficient in reducing retropulsion and increasing stone ablation volume. However, despite its widespread use as a lithotripter, a newly developed thulium fiber laser, which has already shown promising results in experimental studies, could become an alternative in future practice.

Dusting, fragmenting, popcorning or dustmenting?

PURPOSE OF REVIEW

The present review identifies the latest scientific investigations within the fields of fragmenting and dusting to discuss optimizing treatment. In addition, new settings such as 'popcorning' are scrutinized carefully.

RECENT FINDINGS

During the past years, endoscopic techniques have continuously developed and changed the management of the treatment of kidney stones using ureteroscopy (URS). The most currently used energy source for stone disintegration is holmium laser lithotripsy. This technique offers different options for the surgeons to treat their patients suffering from kidney stones.

SUMMARY

URS with the holmium laser allows surgeons to use a variety of different strategies for treating urinary stones. There are two techniques which are most frequently used within this field: firstly fragmenting, using low frequencies and high pulse energy to break stones into small fragments before removal. On the other hand, dusting has been popularized in the field of endourology in recent years. This uses high frequencies and low pulse energy to form fine dust particles which then pass spontaneously down the ureter.

Thulium fiber laser: the new player for kidney stone treatment? A comparison with Holmium:YAG laser

PURPOSE

To compare the operating modes of the Holmium:YAG laser and Thulium fiber laser. Additionally, currently available literature on Thulium fiber laser lithotripsy is reviewed.

MATERIALS AND METHODS

Medline, Scopus, Embase, and Web of Science databases were searched for articles relating to the operating modes of Holmium:YAG and Thulium fiber lasers, including systematic review of articles on Thulium fiber laser lithotripsy.

RESULTS

The laser beam emerging from the Holmium:YAG laser involves fundamental architectural design constraints compared to the Thulium fiber laser. These differences translate into multiple potential advantages in favor of the Thulium fiber laser: four-fold higher absorption coefficient in water, smaller operating laser fibers (50-150 µm core diameter), lower energy per pulse (as low as 0.025 J), and higher maximal pulse repetition rate (up to 2000 Hz). Multiple comparative in vitro studies suggest a 1.5-4 times faster stone ablation rate in favor of the Thulium fiber laser.

CONCLUSIONS

The Thulium fiber laser overcomes the main limitations reported with the Holmium:YAG laser relating to lithotripsy, based on preliminary in vitro studies. This innovative laser technology seems particularly advantageous for ureteroscopy and may become an important milestone for kidney stone treatment.

Vaporizing Effect of the Popcorn Technique for Laser Lithotripsy: Comparing the Different Settings of High Energy in a Caliceal Model

Objective: To assess the effectiveness of laser lithotripsy in different holmium:yttrium aluminum garnet (Ho-YAG) laser settings with a wide range of energies, frequencies, and power. Materials and Methods: Two types of phantom stones were utilized, including soft stone, which mimics uric acid stone, and hard stone, which mimics calcium oxalate monohydrate stone. The stones were made into a round shape measuring 10 mm in diameter. The lithotripsy settings were 1 J × 20 Hz, 2 J × 10 Hz, 1.5 J × 20 Hz, 3 J × 10 Hz, and 2 J × 20 Hz. The lithotripsy was conducted in a caliceal model with a 2-mm filter. All stone vanishing from the artificial calix was an end point of the experiment. All fragments that passed through the filter of each setting were dried and weighed to calculate the vaporizing effect as well as to compare among the different settings. Laser fiber degradation was compared by using these settings. Results: Disintegration efficiency was determined by time consumption and the amount of vaporized stone. The best time consumption was 8 min 51 sec for 2 J × 20 Hz for hard stone and 5 min 13 sec for this setting for soft stone. The most vaporizing effect for hard stone was 92.19% for 2 J × 20 Hz and 87.30% for this setting for soft stone. The most fiber tip degradation was 28 mm for 3 J × 10 Hz for hard stone and 4 mm for 1.5 J × 20 Hz for soft stone. Conclusion: The study revealed that the best setting for hard stone was 2 J × 20 Hz, which was the fastest for achieving maximum vaporization, whereas fiber degeneration was comparable to others. For soft stone, there was no difference among the settings.

Preclinical comparison of superpulse thulium fiber laser and a holmium:YAG laser for lithotripsy

PURPOSE

A superpulse (500 W peak power) thulium fiber laser operating at a 1940 nm wavelength, suitable for lithotripsy, has recently been developed. The goal of this study was to compare stone fragmentation and dusting performance of the prototype superpulse thulium fiber laser with leading commercially available, high-power holmium:YAG lithotripters (wavelength 2100 nm) in a controlled in vitro environment.

METHODS

Two experimental setups were designed for investigating stone ablation rates and retropulsion effects, respectively. In addition, the ablation setup enabled water temperature measurements during stone fragmentation in the laser-stone interaction zone. Human uric acid (UA) and calcium oxalate monohydrate (COM) stones were used for ablation experiments, whereas standard BegoStone phantoms were utilized in retropulsion experiments. The laser settings were matched in terms of pulse energy, pulse repetition rate, and average power.

RESULTS

At equivalent settings, thulium fiber laser ablation rates were higher than those for holmium:YAG laser in both dusting mode (threefold for COM stones and 2.5-fold for UA stones) and fragmentation mode (twofold for UA stones). For single-pulse retropulsion experiments, the threshold for onset of stone retropulsion was two to four times higher for thulium fiber laser. The holmium:YAG laser generated significantly stronger retropulsion effects at equal pulse energies. The water temperature elevation near the laser-illuminated volume did not differ between the two lasers.

CONCLUSIONS

Distinctive features of the thulium fiber laser (optimal wavelength and long pulse duration) resulted in faster stone ablation and lower retropulsion in comparison to the holmium:YAG laser.

Ho:YAG laser lithotripsy in non-contact mode: optimization of fiber to stone working distance to improve ablation efficiency

PURPOSE

To evaluate how variable working distances between the laser fiber and the stone influence ablation volume.

METHODS

A laser fiber was fixed on a robotic arm perpendicular to an artificial stone. A single laser pulse was triggered at different working distances (0-2.0 mm in 0.2 mm increments) between the distal fiber tip and the stone. To achieve a measurable impact, pulse energy was set to 2 and 3 J, with either short or long pulse duration. Ablation volume was calculated with an optical microscope. Experiments were repeated five times for each setting.

RESULTS

Highest ablation volume was observed with a long pulse of 3 J at a working distance of 0.4 mm between the laser fiber and the stone surface (p value < 0.05). At 2 J, the highest ablation volume was noticed with a short pulse in contact mode. However, ablation volume of the latter was not significantly greater than with a long pulse of 2 J at a working distance of 0.4 mm (p value > 0.05). Compared to lithotripsy in contact mode, triggering a single long pulse at 0.4 mm increased ablation volume by 81% (p value = 0.016) at 2 J and by 89% (p value = 0.034) at 3 J.

CONCLUSIONS

For Ho:YAG laser lithotripsy, ablation volume may be higher in non-contact mode using long pulses, rather than in direct contact to the stone. Findings of the current study support the need of further studies of lithotripsy in non-contact mode.

Study of non-contrast helical computed tomography in evaluating holmium laser lithotripsy for urinary calculus

The present study aimed to investigate the correlation between the parameters of non-contrast helical computed tomography (NCHCT) and the total energy of holmium laser lithotripsy, and establish a correlative mathematical model. From March 2016 to February 2017, 120 patients with a single urinary calculus were examined by NCHCT prior to holmium laser lithotripsy. The calculus location was confirmed, the CT value was measured and the volume of the calculus in the established three-dimensional reconstruction model was calculated. The total energy of lithotripsy (TEL) was recorded post-operatively. A significant difference in the TEL between renal calculi and ureteral calculi was identified (P<0.001) and a high and significant correlation between the volume of the calculus and the TEL was determined (Spearman r=0.827, P<0.001). A moderate correlation was identified between the CT value of the calculus and the TEL (Spearman r=0.468, P<0.001). Multivariate linear regression analysis revealed that the location, the volume and the CT value of the calculus were independently associated with the TEL (F=288.858, adjusted R²=0.879, P<0.01). A mathematical model correlating the parameters of NCHCT with the TEL was established, which may provide a foundation to guide the use of energy in holmium laser lithotripsy, and it was possible to estimate the TEL by the location, the volume and the CT value of the calculus.

Holmium:yttrium-aluminum-garnet laser induced lithotripsy: in-vitro investigations on fragmentation, dusting, propulsion and fluorescence

The fragmentation efficiency on Bego artificial stones during lithotripsy and the propulsive effect (via video tracking) was investigated for a variety of laser settings. A variation of the laser settings (pulse energy, pulse duration, repetition rate) altered the total application time required for stone fragmentation, the stone break up time, and the propulsion. The obtained results can be used to develop lithotripsy devices providing an optimal combination of low stone propulsion and high fragmentation efficacy, which can then be evaluated in a clinical setting. Additionally, the fluorescence of human kidney stones was inspected endoscopically in vivo. Fluorescence light can be used to detect stone-free areas or to clearly distinguish calculi from surrounding tissue or operation tools.

Resistance of different guidewires to laser injury: an in-vitro experiment

BACKGROUND

In urology, lasers are used in a variety of endoscopic procedures such as ureteroscopy and retrograde renal surgery for stone fragmentation of urinary calculi and ablation of urothelial tumors. To perform these procedures, guidewires are used as a preliminary safe-mainstay for referencing the urinary tract. This study aims to determine the effect of two different lasers: holmium:YAG (Ho:YAG) and thulium:YAG (Tm:YAG) lasers on metal guidewires with PTFE coating (PTFE), nitinol guidewires with hydrophilic coating (Hydrophilic) and nitinol guidewires with hydrophilic listed coating (Zebra).

METHODS

Different combinations of frequency (5, 10 and 12 Hz) and energy per pulse (0.5, 1.5, and 2.6 J) of Ho:YAG laser were applied on the three kinds of guidewires in two experiments (50 J vs. 100 J of total energy). For the Tm:YAG laser three power levels (5, 35, and 70 W) with a total energy of 100 J were applied to the guidewires. The degree of damage (0 to 5) of the guidewire was assessed after each laser application.

RESULTS

A higher degree of injury of guidewires was related to higher values of total energy used for the Ho:YAG laser (P=0.036), and to higher values of power applied with the Tm:YAG (P=0.051). The most resistant guidewire to Ho:YAG laser energy was Zebra, followed by PTFE and Hydrophilic (P<0.001). With the Tm:YAG laser, PTFE guidewire appears to be the most resistant and the Hydrophilic the most fragile, although without reaching the statistical significance (P=0.223).

CONCLUSIONS

Both lasers revealed a harmful effect on the three tested guidewires. There was an association between the degree of injury and the amount of Ho:YAG laser energy and Tm:YAG laser power. The guidewire Zebra proved to be the safest when using Ho:YAG laser and the PTFE guidewire the most resistant to laser Tm:YAG. Further studies are necessary to confirm these results.

Flexible ureteroscopy: technique, tips and tricks

During the last decades, the surgical management of kidney stones benefited of many technological advances and one of them is the development of flexible ureteroscopy (fURS). This tool, ancillary equipment such as graspers and baskets, and lithotripsy technique with Holmium:YAG laser underwent many improvements leading to a widening of its indications with diagnostic and therapeutic management of upper urinary tract pathologies such as urolithiasis and urothelial tumors. The objective of this review is to describe the surgical technique for fURS as well as tips and tricks for the treatment of renal stones.

Intracorporeal lithotripsy

Since the introduction of ESWL, PNL and URS during the early 1980s the application rate of ESWL has declined while those of PNL and URS have increased. This is mainly due to the facts that instruments and techniques for Intracorporeal Lithotripsy (IL) have made a continuous progress. This review shows that today an array of options for IL within the entire urinary tract is available to treat stones in a perfect minimal invasive way. At the same time further improvements of IL are already visible.

Ureteroscopic Laser Lithotripsy: A Review of Dusting vs Fragmentation with Extraction

INTRODUCTION

Ureteroscopic laser lithotripsy is becoming the most commonly utilized treatment for patients with urinary calculi. The Holmium:YAG (yttrium aluminum garnet) laser is integral to the operation and is the preferred flexible intracorporeal lithotrite. In recent years, there has been increasing interest in examining the effect of varying the laser settings on the effectiveness of stone treatment. Herein, we review the two primary laser treatment approaches: dusting and fragmentation with extraction.

METHODS

We reviewed PubMed and MEDLINE databases from January 1976 through January 2017. All authors participated in the development of consensus definitions of dusting and fragmentation with extraction. The review protocol adhered to preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology.

RESULTS

When the Holmium:YAG laser is used to treat stones, there are two parameters that can be adjusted: power (J) and frequency (Hz). In one treatment paradigm, which became termed "fragmentation with extraction," laser settings that relied on high energy and low frequency were used. Another paradigm, which became termed "dusting," utilized low energy and high frequency settings, which had the effect of breaking off exceedingly small fragments from the stone.

CONCLUSIONS

Both dusting and fragmentation with extraction approaches to ureteroscopic stone treatment are effective. In fact, there is little evidence that one approach is better than the other. However, each does have relative advantages and disadvantages, which should be considered. Although dusting tends to be associated with shorter procedure times and a lower risk of ureteral damage, this approach may place the patient at increased risk for future stone events should all of the resultant debris not be expelled from the collecting system. The active removal associated with fragmentation with extraction, in contrast, may provide for a more complete initial stone clearance.

Holmium Laser Lithotripsy in the New Stone Age: Dust or Bust?

Modern day holmium laser systems for ureteroscopy (URS) provide users with a range of settings, namely pulse energy (PE), pulse frequency (Fr), and pulse width (PW). These variables allow the surgeon to choose different combinations that have specific effects on stone fragmentation during URS lithotripsy. Contact laser lithotripsy can be performed using fragmentation or dusting settings. Fragmentation employs settings of low Fr and high PE to break stones that are then extracted with retrieval devices. Dusting is the utilization of high Fr and low PE settings to break stones into submillimeter fragments for spontaneous passage without the need for basket retrieval. Use of the long PW mode during lithotripsy can reduce stone retropulsion and is increasingly available in new generation lasers. During non-contact laser lithotripsy, stone fragments are rapidly pulverized in a calyx in laser bursts that result in stones breaking into fine fragments. In this review, we discuss the effect of different holmium laser settings on stone fragmentation, and the clinical implications in a very much evolving field.

Use of the Moses Technology to Improve Holmium Laser Lithotripsy Outcomes: A Preclinical Study

Objective: To evaluate in vitro and in vivo effects of Moses technology in Holmium laser and to compare it with the Regular mode in terms of lithotripsy efficiency and laser-tissue interactions.

Methods: The Lumenis^® Pulse™ P120H holmium laser system together with Moses D/F/L fibers were used to compare the Regular mode with the Moses modes in stone retropulsion by using a high-speed camera, and stone ablation efficiency. In addition, a porcine ureteroscopy model was used to assess stone fragmentation and dusting as well as laser-tissue interaction with the ureteral wall.

Results: After a laser pulse, in vitro stone displacement experiments showed a significant reduction in retropulsion when using the Moses mode. The stone movement was reduced by 50 times at 0.8 J and 10 Hz (p < 0.01). The pronounced reduction of retropulsion in the Moses mode was clearly observed during fragmentation setting (high energy) and dusting (low energy, high Hz). In addition, stone fragmentation tests showed that the Moses modes resulted in a significantly higher ablation volume when compared with the Regular mode (160% higher; p < 0.001). In vivo assessment also supported the reduction in retropulsion when treating stones in the porcine kidney. Histological analysis of the porcine ureter after direct lasing in the Moses mode suggested less damage than in the Regular mode.

Conclusions: The Moses technology resulted in more efficient laser lithotripsy, in addition to significantly reduced stone retropulsion, and displayed a margin of safety that may result in a shorter procedural time and safer lithotripsy.

Optimal Settings for the Noncontact Holmium:YAG Stone Fragmentation Popcorn Technique

PURPOSE

The purpose of this study was to evaluate the popcorn technique using a wide range of holmium laser settings and fiber sizes in a systematic in vitro assessment.

MATERIALS AND METHODS

Evaluations were done with 4 artificial stones in a collection tube. A fixed ureteroscope was inserted through a ureteral access sheath to provide constant irrigation flow and the laser was placed 1 mm from the bottom. Combinations of 0.5 to 1.5 J, 10 to 20 and 40 Hz, and long and short pulses were tested for 2 and 4 minutes. We used 273 and 365 μm laser fibers. All tests were repeated 3 times. The stones were weighed before and after the experiments to evaluate the setting efficiency. Significant predictors of a highly efficient technique were assessed.

RESULTS

A total of 144 tests were performed. Mean starting weight of the stones was 0.23 gm, which was consistent among the groups. After the experiment the median weight difference was 0.07 gm (range 0.01 to 0.24). When designating a 50% reduction in stone volume as the threshold indicating high efficiency, the significant predictors of an efficient popcorn technique were a long pulse (OR 2.7, 95% CI 1.05-7.15), a longer duration (OR 11.4, 95% CI 3.88-33.29), a small (273 μm) laser fiber (OR 0.23, 95% CI 0.08-0.70) and higher power (W) (OR 1.14, 95% CI 1.09-1.20).

CONCLUSIONS

Higher energy, a longer pulse, frequencies higher than 10 Hz, a longer duration and a smaller laser fiber predict a popcorn technique that is more efficient at reducing stone volume.

Advances in urology 2015–2016

It has become customary that a session is held at the British Association of Urological Surgeons (BAUS) annual meeting wherein the most important advances in the major urological sub-specialities are summarised by British opinion leaders for the benefit of the core urologist. It gives us pleasure to present in this paper (to which the six authors contributed equally) the topics covered at the Liverpool BAUS meeting in June 2016.

Combining ultrasonography and noncontrast helical computerized tomography to evaluate Holmium laser lithotripsy

The purpose of the study was to establish a mathematical model for correlating the combination of ultrasonography and noncontrast helical computerized tomography (NCHCT) with the total energy of Holmium laser lithotripsy.In this study, from March 2013 to February 2014, 180 patients with single urinary calculus were examined using ultrasonography and NCHCT before Holmium laser lithotripsy. The calculus location and size, acoustic shadowing (AS) level, twinkling artifact intensity (TAI), and CT value were all documented. The total energy of lithotripsy (TEL) and the calculus composition were also recorded postoperatively. Data were analyzed using Spearman's rank correlation coefficient, with the SPSS 17.0 software package. Multiple linear regression was also used for further statistical analysis.A significant difference in the TEL was observed between renal calculi and ureteral calculi (r = -0.565, P < 0.001), and there was a strong correlation between the calculus size and the TEL (r = 0.675, P < 0.001). The difference in the TEL between the calculi with and without AS was highly significant (r = 0.325, P < 0.001). The CT value of the calculi was significantly correlated with the TEL (r = 0.386, P < 0.001). A correlation between the TAI and TEL was also observed (r = 0.391, P < 0.001). Multiple linear regression analysis revealed that the location, size, and TAI of the calculi were related to the TEL, and the location and size were statistically significant predictors (adjusted r = 0.498, P < 0.001).A mathematical model correlating the combination of ultrasonography and NCHCT with TEL was established; this model may provide a foundation to guide the use of energy in Holmium laser lithotripsy. The TEL can be estimated by the location, size, and TAI of the calculus.