Update on lasers in urology 2014: current assessment on holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripter settings and laser fibers

[Organ-preserving treatment for urothelial carcinoma of the upper urinary tract]

Urothelial carcinoma of the upper urinary tract is rare but the incidence is currently increasing in western countries. Radical nephroureterectomy has long been the standard treatment; however, it can lead to chronic kidney failure and also the necessity for dialysis. Therefore, organ-preserving treatment is now recommended for selected patients with low-risk tumors. The choice of treatment depends on the tumor characteristics, comorbidities and individual risk factors. Surgical options for organ preservation include ureterorenoscopy (URS), percutaneous treatment and partial ureteral resection. The URS is the most frequently used method for organ preservation. Photodynamic diagnostics (PDD) and narrow band imaging (NBI) can potentially also be used for tumor detection in the upper urinary tract. Conservative options such as topical treatment with mitomycin C or Bacillus Calmette-Guérin (BCG) and systemic treatment options are also possible.

Preconceived Impressions Regarding Holmium:YAG Laser Safety in the Urology Operating Theatre

Background

Since its introduction over two decades ago, the surgical laser has served in the lithotripsy of urinary calculi, resection of bladder tumours, bladder neck incisions, and prostate enucleation. Concerns regarding the safe use of holmium lasers have resulted in potentially excessive and overly precautious theatre regulations. We aimed to evaluate the preconceived impressions and practice patterns at a single site surrounding laser use in endourology.

Methods

We designed a three-part online questionnaire that could be accessed using a smart device or computer. This survey was distributed to all theatre staff involved in laser surgery at our single site, including surgical, nursing, and anaesthetic staff of varying seniority. It asked questions regarding holmium laser safety, provided an up-to-date summary of published literature surrounding the safe use of lasers, and finally gave participants further option to alter the answers to several previously encountered questions.

Results

A total of 54 theatre staff completed the survey, including 17 theatre nurses (31.5%), 10 urology consultants (18.5%), 8 urology registrars (14.8%), 7 anaesthetic registrars (13%), 4 anaesthetic consultants (7.4%). About 51.9% of participants believed that current laser safety protocols were adequate, with 38.9% finding them excessive. After reading recently published information on laser safety, 22.2% thought current laser safety measures were adequate (57% decrease) and 77.8% found them to be excessive (100% increase). About 74.1% of participants found that laser safety goggles impair their vision and that 79.6% would choose not to wear them if they were optional.

Conclusion

Strict laser safety guidelines reflect an overestimated risk associated with using holmium laser in operating theatres. Laser safety regulations should be re-evaluated to align with current research and potential hazards inherent to the device. In doing so, a more effective distribution of staff could enable greater access to laser surgery, thereby reducing patient morbidity and hospital wait times.

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.

Analyzing global research trends and focal points in the utilization of laser techniques for the treatment of urolithiasis from 1978 to 2022: visualization and bibliometric analysis

Laser lithotripsy is gaining global prominence and is a dynamically progressing field marked by a continual influx of new and comprehensive research each year. Recently, there has been a noticeable shift toward the adoption of various kinds of lasers, such as holmium: yttrium-aluminum-garnet (Ho:YAG) and thulium fiber (TFL) lasers. Consequently, we aim to conduct a bibliometric analysis to analyze key areas of research activity within scientific publications that center on the utilization of laser techniques in urolithiasis. A search of the literature spanning from 1978 to 2022 was carried out on 25 December 2023 using the Scopus database to explore research related to the application of laser techniques for urolithiasis treatment. Visualization analysis was performed using VOSviewer software (version 1.6.20). We examined 962 publications that met the specified criteria, 791 (82.22%) of which were original articles. The analysis of the retrieved publications indicated a consistent increase in research output from 1978 to 2022; a particularly noteworthy surge occurred after 2003. In particular, the U.S. claimed the leading position as the most productive country, contributing 211 articles (21.93%). However, India had the highest research productivity according to the adjustment index of 19.08. In the European region, 324 publications (33.68% of the total) originated from 25 countries. The Journal of Endourology contributed the most between 1978 and 2022 (n = 96, 9.98%). The most cited paper examined the effectiveness of holmium: yttrium-aluminum-garnet (Ho:YAG) lasers, while a subsequent study focused on the use of a thulium fiber laser (TFL), an emerging laser technology that has gained increased recognition. Co-occurrence analysis revealed three distinct clusters focusing on the types of laser technology, minimally invasive approaches, and success rate/postoperative complications. This comprehensive investigation delves into the global landscape of laser use for the treatment of urolithiasis. This review supports the emerging clinical concept of using various types of laser technology for urolithiasis treatment. Moreover, the hot issues that researchers should focus on based on the findings of this study are the use of different types of laser lithotripsy in view of the surgical approach, success rate and complications.

Comparison of high and low pulse energy dusting protocols using holmium: YAG laser in flexible ureteroscopy for treatment of renal stones

Objectives

The management of renal stones, particularly those less than 2 cm in diameter, has changed with the development of endourological techniques, among which flexible ureteroscopy (FURS) using laser for lithotripsy has become a cornerstone. This study aims to compare the effectiveness of high pulse energy versus low pulse energy laser settings in renal stone dusting by Holmium YAG laser.

Patients and Methods

This prospective randomized study was conducted between September 2021 and November 2023 to compare the efficacy and safety of high energy versus low-energy pulse settings using a Holmium: YAG laser dusting of renal stones less than 2 cm in diameter. A total of 174 adult patients were included, divided equally into high- and low-pulse energy groups, based on the energy settings of the laser high energy (ranged from 1.2-2.5 Joules and frequency of 8 hz) and low energy (less than 0.5 Joules and frequency ≥ 15 hz) using the dusting ‎technique with non-touch non-stop approach. The study sought to evaluate the impact of these settings on stone fragmentation efficiency, operative time, laser energy consumption, and postoperative outcomes, including stone-free rates and complications.

Results

The study involved 174 patients who underwent renal stone lithotripsy and showed that using high pulse energy laser dusting settings significantly reduced operative times and more rapid dusting compared to low pulse energy settings, without affecting the stone-free rate. The study observed no significant differences in stone size or location between both groups. Minor postoperative complications were similar between both groups, indicating high pulse energy settings for lithotripsy dusting.

Conclusion

The efficacy of high pulse energy dusting in enhancing stone removal during surgery, potentially reducing operative time. Further validation through larger-scale studies is needed to solidify these findings. This technique presents a promising solution, particularly in regions with limited resources where acquiring expensive laser equipment is challenging.

Comparison of Thulium Fiber Laser versus Holmium laser in ureteroscopic lithotripsy: a Meta-analysis and systematic review

OBJECTIVES

To compare the efficacy and safety of thulium fiber laser (TFL) to holmium: YAG (Ho: YAG) laser in ureteroscopic lithotripsy for urolithiasis.

METHODS

PubMed, Web of Science, Embase, CENTRAL, SinoMed, CNKI database, VIP and Wanfang Database were systematically searched for all relevant clinical trials until September 2023. References were explored to identify the relevant articles. Meta-analysis was carried out for the retrieved studies using RevMan5.4.1 software, and the risk ratio, mean difference and 95% confidence interval were expressed. Statistical significance was set at p < 0.05. The main outcomes of this meta-analysis were stone-free rate (SFR), perioperative outcomes and intraoperative or postoperative complications.

RESULTS

Thirteen studies, including 1394 patients, were included. According to the results of pooled analysis, TFL was associated with significantly higher stone-free rate (SFR) [0.52, 95% CI (0.32, 0.85), P = 0.009], shorter operation time [-5.47, 95% CI (-8.86, -2.08), P = 0.002], and less stone migration [0.17, 95% CI (0.06, 0.50), P = 0.001]. However, there was no significant difference in terms of the laser time, duration of hospital stay, drop of hemoglobin level, total energy, postoperative ureteral stenting, the incidence of intraoperative complications or postoperative complications between TFL and Ho: YAGs.

CONCLUSION

The findings of this study demonstrated several advantages of TFL in terms of higher SFR, shorter operative time and less stone migration.

TRIAL REGISTRATION

The protocol of this systematic review was listed in PROSPERO ( www.crd.york.ac.uk/PROSPERO ) (Protocol number: CRD42022362550).

Safety Parameters for the Use of Holmium:YAG Laser in the Treatment of Biliary Calculi: The Ex-Vivo Model

Background and Objectives: While studies have demonstrated the efficacy of cholangioscopy-guided Holmium-Yttrium aluminum garnet (Ho:YAG) laser lithotripsy for the treatment of refractory bile duct stones, data regarding the safety of the operating parameters for laser lithotripsy are lacking. The aim of this study was to determine safe, yet effective, energy settings for Ho:YAG laser in the ex-vivo model. Materials and Methods: This ex vivo experimental study utilized the Ho:YAG laser on porcine bile duct epithelium and human gallstones. Ho:YAG laser lithotripsy was applied in different power settings from 8 to 15 Watts (W) to six explanted porcine bile ducts. Settings that appeared safe were then utilized to fragment seventy-three human gallstones. Results: The median bile duct perforation times with the Ho:YAG laser between 8-15 W were: >60 s (8 W); 23 s (9 W); 29 s (10 W); 27 s (12 W); 12 s (14 W); and 8 s (15 W). Statistically significant differences in the median perforation times were noted between 8 W vs. 15 W, 9 W vs. 15 W, 10 W vs. 15 W, and 12 W vs. 15 W (p < 0.05). When using a 365 µm Ho:YAG laser probe at 8-12 W, the fragmentation rates on various size stones were: 100% (<1.5 cm); 80-100% (1.6-2.0 cm) and 0-32% (>2.0 cm). Optimal fragmentation was seen utilizing 12 W with high energy (2.4 J) and low frequency (5 Hz) settings. Using a larger 550 µm probe at these settings resulted in 100% fragmentation of stones larger than 2 cm. Conclusions: The Ho:YAG laser appears to be safe and effective in the treatment of large bile duct stones when used between 8-12 W in 5 s bursts in an ex vivo model utilizing porcine bile ducts and human gallstones.

Evaluation of a novel circulation system for ureteroscopic laser lithotripsy in vitro

PURPOSE

To evaluate the cooling effect and other advantages of a novel circulation system for ureteroscopic holmium laser lithotripsy (URSL) in a standardized in vitro model.

MATERIALS AND METHODS

The novel circulation system was assembled by connecting a 4Fr ureteral catheter and a filter. Trails were divided into a new URSL group and a conventional URSL group. First, different power settings (18-30 W) of the holmium laser and irrigation flow rates (20-50 mL/min) were used to evaluate the thermal effect on the lithotripsy site of all groups. Then, renal pelvic temperature and pressure were assessed during URSL at a power of 1.5 J/20 Hz and irrigation flow rates of (20-50 mL/min). Finally, the whole process of lithotripsy was performed at 1.5 J/20 Hz (operator duty cycle ODC: 50%) with an irrigation flow rate of 30 mL/min. The time required for lithotripsy, visual field clarity, and stone migration were observed.

RESULTS

Temperature of the lithotripsy point was significantly lower in the new URSL group than in the conventional group (P < 0.05) with irrigation rates (20, 30 mL/min). The renal pelvic pressure of the new group was significantly lower than that of the conventional group in which intrarenal hypertension developed at an irrigation rate of 50 ml/min. The new group had better visual clarity and lesser stone upward migration when lithotripsy was performed at 1.5 J/20 Hz and 30 ml/min.

CONCLUSION

The novel circulation system is more effective in reducing the thermal effects of URSL, pelvic pressure, stone upward migration, and improving the visual clarity of the operative field.

Pulsed Thulium:YAG laser - What is the lithotripsy ablation efficiency for stone dust from human urinary stones? Results from an in vitro PEARLS study

BACKGROUND

The novel pulsed thulium:yttrium-aluminum-garnet (p-Tm:YAG) laser was recently introduced. Current studies present promising p-Tm:YAG ablation efficiency, although all are based on non-human stone models or with unknown stone composition. The present study aimed to evaluate p-Tm:YAG ablation efficiency for stone dust from human urinary stones of known compositions.

METHODS

Calcium oxalate monohydrate (COM) and uric acid (UA) stones were subjected to lithotripsy in vitro using a p-Tm:YAG laser generator (Thulio®, Dornier MedTech GmbH, Germany). 200 J was applied at 0.1 J × 100 Hz, 0.4 J × 25 Hz or 2.0 J × 5 Hz (average 10W). Ablated stone dust mass was calculated from weight difference between pre-lithotripsy stone and post-lithotripsy fragments > 250 µm. Estimated ablated volume was calculated using prior known stone densities (COM: 2.04 mg/mm3, UA: 1.55 mg/mm3).

RESULTS

Mean ablation mass efficiency was 0.04, 0.06, 0.07 mg/J (COM) and 0.04, 0.05, 0.06 mg/J (UA) for each laser setting, respectively. This translated to 0.021, 0.029, 0.034 mm3/J (COM) and 0.026, 0.030, 0.039 mm3/J (UA). Mean energy consumption was 26, 18, 17 J/mg (COM) and 32, 23, 17 J/mg (UA). This translated to 53, 37, 34 J/mm3 (COM) and 50, 36, 26 J/mm3 (UA). There were no statistically significant differences for laser settings or stone types (all p > 0.05).

CONCLUSION

To our knowledge, this is the first study showing ablation efficiency of the p-Tm:YAG laser for stone dust from human urinary stones of known compositions. The p-Tm:YAG seems to ablate COM and UA equally well, with no statistically significant differences between differing laser settings.

Laser Ablation Efficiency, Laser Ablation Speed, and Laser Energy Consumption During Lithotripsy: What Are They and How Are They Defined? A Systematic Review and Proposal for a Standardized Terminology

CONTEXT

Laser performance for lithotripsy is currently reported using units of measurement such as J/mm3, mm3/J, mm3/s, s/mm3, and mm3/min. However, there are no current standardized definitions or terminology for these metrics. This may lead to confusion when assessing and comparing different laser systems.

OBJECTIVE

The primary objective was to summarize outcome values and corresponding terminology from studies on laser lithotripsy performance using stone volume in relation to time or energy. The secondary objective was to propose a standardized terminology for reporting laser performance metrics.

EVIDENCE ACQUISITION

A systematic review of the literature was conducted using the search string ("j*/mm3" OR "mm3/j*" OR "mm3/s*" OR "s*/mm3" OR "mm3/min*" OR "min*/mm3" AND "lithotripsy") on Scopus, Web of Science, Embase, and PubMed databases. Study selection, data extraction, and quality assessment were performed independently by two authors.

EVIDENCE SYNTHESIS

A total of 28 studies were included, covering holmium:yttrium-aluminum-garnet (Ho:YAG), MOSES, and thulium fiber laser (TFL) technologies. Laser energy consumption values reported for the studies ranged from 2.0 - 43.5 J/mm3in vitro and from 2.7 - 47.8 J/mm3in vivo, translating to laser ablation efficiency of 0.023 - 0.500 mm3/J and 0.021 - 0.370 mm3/J, respectively. Laser ablation speeds ranged from 0.3 - 8.5 mm3/s in vivo, translating to lasing time consumption of 0.12 - 3.33 s/mm3. Laser efficacy ranged from 4.35 - 51.7 mm3/min in vivo. There was high heterogeneity for the terminology used to describe laser performance for the same metrics.

CONCLUSIONS

The range of laser performance metric values relating stone volume to energy or time is wide, with corresponding differing terminology. We propose a standardized terminology for future studies on laser lithotripsy, including laser ablation efficiency (mm3/J), laser ablation speed (mm3/s), and laser energy consumption (J/mm3). Laser efficacy (mm3/min) is proposed as a broader term that is based on the total operative time, encompassing the whole technique using the laser.

PATIENT SUMMARY

We reviewed studies to identify the units and terms used for laser performance when treating urinary stones. The review revealed a wide range of differing units, outcomes, and terms. Therefore, we propose a standardized terminology for future studies on laser stone treatment.

Pulsed thulium:YAG laser-ready to dust all urinary stone composition types? Results from a PEARLS analysis

PURPOSE

To evaluate whether stone dust can be obtained from all prevailing stone composition types using the novel pulsed thulium:YAG (p-Tm:YAG), including analysis of stone particle size after lithotripsy.

METHODS

Human urinary stones of 7 different compositions were subjected to in vitro lithotripsy using a p-Tm:YAG laser with 270 µm silica core fibers (Thulio®, Dornier MedTech GmbH®, Wessling, Germany). A cumulative energy of 1000 J was applied to each stone using one of three laser settings: 0.1 J × 100 Hz, 0.4 J × 25 Hz and 2.0 J × 5 Hz (average power 10 W). After lithotripsy, larger remnant fragments were separated from stone dust using a previously described method depending on the floating ability of dust particles. Fragments and dust samples were then passed through laboratory sieves to evaluate stone particle count according to a semiquantitative analysis relying on a previous definition of stone dust (i.e., stone particles ≤ 250 µm).

RESULTS

The p-Tm:YAG laser was able to produce stone dust from lithotripsy up to measured smallest mesh size of 63 µm in all seven stone composition types. Notably, all dust samples from all seven stone types and with all three laser settings had high counts of particles in the size range agreeing with the definition stone dust, i.e., ≤ 250 µm.

CONCLUSION

This is the first study in the literature proving the p-Tm:YAG laser capable of dusting all prevailing human urinary stone compositions, with production of dust particles ≤ 250 µm. These findings are pivotal for the broader future implementation of the p-Tm:YAG in clinical routine.

Photonic Lithotripsy: Near-Infrared Laser Activated Nanomaterials for Kidney Stone Comminution

Near-infrared activated nanomaterials have been reported for biomedical applications ranging from photothermal tumor destruction to biofilm eradication and energy-gated drug delivery. However, the focus so far has been on soft tissues, and little is known about energy delivery to hard tissues, which have thousand-fold higher mechanical strength. We present photonic lithotripsy with carbon and gold nanomaterials for fragmenting human kidney stones. The efficacy of stone comminution is dependent on the size and photonic properties of the nanomaterials. Surface restructuring and decomposition of calcium oxalate to calcium carbonate support the contribution of photothermal energy to stone failure. Photonic lithotripsy has several advantages over current laser lithotripsy, including low operating power, noncontact laser operation (distances of at least 10 mm), and ability to break all common stones. Our observations can inspire the development of rapid, minimally invasive techniques for kidney stone treatment and extrapolate to other hard tissues such as enamel and bone.

Comparing dusting and fragmenting efficiency using the new SuperPulsed thulium fiber laser versus a 120 W Holmium:YAG laser

PURPOSE

Holmium:YAG laser lithotripsy requires high amperage power and has an upper limit of frequency and a minimal fiber size. The technology utilizing thulium-doped fiber offers low pulse energy settings and high pulse frequencies up to 2,400 Hz. We compared the novel SuperPulsed thulium fiber laser (SOLTIVE™; Olympus) to a commercially available 120 W Ho:YAG laser.

MATERIALS AND METHODS

Bench-top testing was conducted with 125 mm³ standardized BegoStones (Bego USA). Time to ablate the stone into particles <1 mm was recorded for efficiency calculations. Finite energy was delivered, and resulting particle sizes were measured to determine fragmentation (0.5 kJ) and dusting (2 kJ) efficiencies. Remaining mass or number of fragments were measured to compare efficacy.

RESULTS

SOLTIVE™ was faster at ablating stones to particles <1 mm (2.23±0.22 mg/s, 0.6 J 30 Hz short pulse) compared to Ho:YAG laser (1.78±0.44 mg/s, 0.8 J 10 Hz short pulse) (p<0.001). Following 0.5 kJ of energy in fragmentation testing, fewer particles >2 mm remained using SOLTIVE™ than Ho:YAG laser (2.10 vs. 7.20 fragments). After delivering 2 kJ, dusting (1.05±0.08 mg/s) was faster using SOLTIVE™ (0.1 J 200 Hz short pulse) than 120 W 0.46±0.09 mg/s (0.3 J 70 Hz Moses) (p=0.005). SOLTIVE™ (0.1 J 200 Hz) produced more dust particles <0.5 mm (40%) compared to 24% produced by the P120 W laser at 0.3 J 70 Hz Moses and 14% at 0.3 J 70 Hz long pulse (p=0.015).

CONCLUSIONS

The efficacy of SOLTIVE™ is superior to the 120 W Ho:YAG laser by producing smaller dust particles and fewer fragments. Further studies are warranted.

Innovations in Kidney Stone Removal

Urolithiasis is a common clinical condition, and surgical treatment is performed with different minimally invasive procedures, such as ureteroscopy, shockwave lithotripsy and percutaneous nephrolithotomy. Although the transition from open surgery to endourological procedures to treat this condition has been a paradigm shift, ongoing technological advancements have permitted further improvement of clinical outcomes with the development of modern equipment. Such innovations in kidney stone removal are new lasers, modern ureteroscopes, development of applications and training systems utilizing three-dimensional models, artificial intelligence and virtual reality, implementation of robotic systems, sheaths connected to vacuum devices and new types of lithotripters. Innovations in kidney stone removal have led to an exciting new era of endourological options for patients and clinicians alike.

First Clinical Experience of a Novel Pulsed Solid-State Thulium:YAG Laser during Percutaneous Nephrolithotomy

INTRODUCTION

Laser lithotripsy during Mini-PCNL is one treatment option in urinary stone disease. In recent years, a new era in stone treatment has been initiated with the introduction of new pulsed thulium lasers. The aim of this study was to investigate the safety and efficacy of laser lithotripsy with a new pulsed solid-state thulium:YAG laser during mini-PCNL.

MATERIALS AND METHODS

All patients, regardless of stone size, who were treated with a Mini-PCNL using the new pulsed thulium laser were prospectively enrolled. Operation times, stone size, laser time, and laser settings were noted. The stone-free rate was assessed postoperatively with sonography and either X-ray or computed tomography as a clinical standard. The complications were analyzed using the Clavien-Dindo classification.

RESULTS

A total of 50 patients with a mean age of 52 years were included. 31 (62 %) patients were male. The average stone size was 242.3 (±233.1) mm2 with an average density of 833 (±325) Hounsfield units. The mean operating time was 30.56 (±28.65) min, and the laser-on-time was 07:07 (± 07:08) min. The most commonly used settings were 0.4 J and 115 Hz (46 W). The mean total energy for stone ablation was 14,166 (±17,131) kJ. The total stone-free rate was 84 %, with an overall complication rate of 32% according to Clavien-Dindo (grade 1: n = 9, grade 2: n = 6, 3b: n = 1). In the group of patients with singular stones (n = 25), the stone-free rate was 88%.

SUMMARY

The new pulsed solid-state Thulium:YAG laser allows a safe and effective lithotripsy during Mini-PCNL. The stone-free rates were high regardless of stone size with a comparable low rate of complications.

Comparative Results of Vocal Fold Injury According to the Fiber-Based Laser in a Rabbit Vocal Fold Model

OBJECTIVES

We assessed the safety of flexible fiber-based lasers including the potassium-titanyl-phosphate (KTP), CO2, and Holmium lasers using a rabbit vocal fold model and provided the safety evidence of laser before human clinical trial.

METHODS

In all, 120 male New Zealand white rabbits were used. Each laser was used to induce acute and chronic vocal fold injuries in 40 rabbits. The same laser energy with the same intensity and frequency were used in all cases, and we evaluated outcomes via surface scanning electron microscopy (SEM) and histological examination 1 day after injury. Histological and high-speed vocal fold vibration examinations were evaluated 1 month after injury. Surface injury roughness grading was done via SEM, and the Acute injury ratio and lamina propria (LP) ratio were also calculated. The dynamic glottal gap was measured through functional analyses based on recordings from a high-speed digital camera.

RESULTS

The Holmium laser caused significantly more vocal fold damage than did the KTP and CO2 lasers as revealed by SEM and evaluation of acute and chronic injuries. Functional analysis with high-speed digital camera indicated that the holmium laser reduced dynamic glottal gap compared with the normal vocal fold, where the other lasers did not.

CONCLUSIONS

The histological and functional analyses of rabbit vocal fold experiments indicated that fiber-based laryngeal laser surgery for vocal fold lesions could be performed relatively safely using a KTP or CO2 laser.

Endoscopic Management of Upper and Lower Ureteric Stones Using Pneumatic Lithotripter: A Retrospective Medical Records Review

Background

In this study we aimed to assess and compare the rate of sem-irigid ureterorenoscope in the treatment of upper and lower ureter stones through pneumatic lithotripsy (PL).

Materials and Methods

Ninety-two patients with a mean age±SD of 45±15years who had had a surgical procedure performed by the same experienced surgeon between January 2013 and July 2015 were included in the study. The mean±SD stone size was 8.8±2.6 mm. Forty-two of the patients (45.7%) had upper ureter stones and 50 (54.3%) had lower ureter stones in order to increase the success rate and avoid stone migration. The medical files of the patients were reviewed regarding age, sex, stone size, stone location, success rate, complications, and presence of hydronephrosis. Success was operationally defined as the complete fragmentation of stone to very small parts that could pass or complete extraction of the stone.

Results

Eighty-four of the patients were stone free (91%). The success rates for patients with upper or lower ureteric stones were 93% and 90%, respectively (P=0.63). There were no complications during the operation. However, 4 patients (4.4%) had postoperative complications in terms of urinary tract infection or urosepsis. Those were accurately managed by the suitable medical treatment.

Conclusion

Semi-rigid ureterorenoscopy by using PL was a safe and practical treatment option for managing the upper and lower ureter stones. Performing the tips and tricks of ureterorenoscopy by an experienced surgeon seems to enhance the success rate, especially in upper ureter stones.

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.

The Effects of Scanning Speed and Standoff Distance of the Fiber on Dusting Efficiency during Short Pulse Holmium: YAG Laser Lithotripsy

To investigate the effects of fiber lateral scanning speed across the stone surface (v_fiber) and fiber standoff distance (SD) on dusting efficiency during short pulse holmium (Ho): YAG laser lithotripsy (LL), pre-soaked BegoStone samples were treated in water using 0.2 J/20 Hz at SD of 0.10~0.50 mm with v_fiber in the range of 0~10 mm/s. Bubble dynamics, pressure transients, and stone damage were analyzed. To differentiate photothermal ablation vs. cavitation damage, experiments were repeated in air, or in water with the fiber tip at 0.25 mm proximity from the ureteroscope end to mitigate cavitation damage. At SD = 0.10 mm, the maximum dusting efficiency was produced at v_fiber = 3.5 mm/s, resulting in long (17.5 mm), shallow (0.15 mm), and narrow (0.4 mm) troughs. In contrast, at SD = 0.50 mm, the maximum efficiency was produced at v_fiber = 0.5 mm/s, with much shorter (2.5 mm), yet deeper (0.35 mm) and wider (1.4 mm), troughs. With the ureteroscope end near the fiber tip, stone damage was significantly reduced in water compared to those produced without the ureteroscope. Under clinically relevant v_fiber (1~3 mm/s), dusting at SD = 0.5 mm that promotes cavitation damage may leverage the higher frequency of the laser (e.g., 40 to 120 Hz) and, thus, significantly reduces the procedure time, compared to at SD = 0.1 mm that promotes photothermal ablation. Dusting efficiency during short pulse Ho: YAG LL may be substantially improved by utilizing an optimal combination of v_fiber, SD, and frequency.

Advances in Ureteroscopy: New technologies and current innovations in the era of Tailored Endourological Stone Treatment (TEST)

Ureteroscopy has undergone many advances in recent decades. As a result, it is able to treat an increasing range of patient groups including special populations such as pregnancy, anomalous kidneys and extremes of age. Such advances include Holmium laser, high-power systems and pulse modulation. Thulium fibre laser is a more recent introduction to clinical practice. Ureteroscopes have also been improved alongside vision and optics. This article provides an up-to-date guide to these topics as well as disposable scopes, pressure control and developments in operating planning and patient aftercare. These advances allow for a custom strategy to be applied to the individual patient in what we describe using a new term: Tailored endourological stone treatment (TEST).

Level of evidence: 5

Evaluation of the relation between size of stone and its attenuation measured by Hounsfield units and the total laser energy required to fragment it

BACKGROUND

Anticipating the total laser energy (TLE) of Holmium YAG laser required for ureteroscopic (URS) lithotripsy is essential to guide urologists in selecting the optimal fiber size. This study aimed at evaluating the relationship between stone size and stone attenuation measured by HU as predictors for the TLE during the procedure.

METHODS

We conducted an observational prospective cohort study of patients undergoing URS lithotripsy at the Urology department of Ain Shams University Hospitals from September 2018 to September 2019 with the use of a holmium YAG laser as the lithotripsy method. Patients' demographic and clinical characteristics, stone location, stone size, stone attenuation measured by HU from the non-contrast CT, TLE, and procedure time were recorded. Data were analyzed using Jamovi software (version 2.0 for macOS).

RESULTS

Forty patients were included in the study (22 males and 18 females) with a mean age of 57.8 years. The mean stone size was 9.8 mm³, the mean HU was 858.8 units, and the mean TLE was 3.5 KJ. Both stone size and stone attenuation measured by HU were positively correlated with TLE (r = 0.81 and 0.84, respectively; p < 0.001 for both). Further, regression analysis showed that both variables could significantly predict the TLE (ß = 0.001 and 0.71, respectively).

CONCLUSIONS

Both stone attenuation, as measured by HU, and stone size positively correlate with TLE required for URS lithotripsy. Therefore, both HU and stone size can predict the TLE, which will be helpful to guide the urologist in selecting the optimal fiber size for the procedure.

New Generation Pulse Modulation in Holmium:YAG Lasers: A Systematic Review of the Literature and Meta-Analysis

(1) Background: New pulse modulation (PM) technologies in Holmium:YAG lasers are available for urinary stone treatment, but little is known about them. We aim to systematically evaluate the published evidence in terms of their lithotripsy performance. (2) Methods: A systematic electronic search was performed (MEDLINE, Scopus, and Cochrane databases). We included all relevant publications, including randomized controlled trials, non-randomized comparative and non-comparative studies, and in-vitro studies investigating Holmium:YAG lithotripsy performance employing any new PM. (3) Results: Initial search yielded 203 studies; 24 studies were included after selection: 15 in-vitro, 9 in-vivo. 10 In-vitro compared Moses with regular PM, 1 compared Quanta’s, 1 Dornier MedTech’s, 2 Moses with super Thulium Fiber Laser, and 1 compared Moses with Quanta PMs. Six out of seven comparative studies found a statistically significant difference in favor of new-generation PM technologies in terms of operative time and five out of six in fragmentation time; two studies evaluated retropulsion, both in favor of new-generation PM. There were no statistically significant differences regarding stone-free rate, lasing and operative time, and complications between Moses and regular PM when data were meta-analyzed. (4) Conclusions: Moses PM seems to have better lithotripsy performance than regular modes in in-vitro studies, but there are still some doubts about its in-vivo results. Little is known about the other PMs. Although some results favor Quanta PMs, further studies are needed.

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.

Laser accessories: surgical fibers, strippers, cleavers, and protective glasses

PURPOSE OF REVIEW

This review provides most recent findings and developments relating to surgical laser fibers, strippers, cleavers, and protective glasses.

RECENT FINDINGS

The smallest core diameter that can be used with Holmium:YAG lasers is 200 μm. Smaller core diameter fibers can be used with the Thulium fiber laser and offer better flexibility and lower risk of fracture, at the risk of greater burnback effect. Misleading discrepancies between the true diameter of laser fibers and their packaging labels must be considered. Fiber tip degradation from the burnback occurs within few minutes, thus questioning the need for time-consuming fiber tip reprocessing with fiber strippers and special cleaving tools. This shortcoming also applies to instrument-protecting ball-tip fibers. Cleavage of fiber tips through their protective jackets ('coated tips') is a cheaper alternative for instrument protection, additionally offering better visual control of the fiber tip. Third-generation side-firing greenlight laser fibers are still prone to rapid deterioration. Laser eyewear does not seem necessary for Holmium:YAG applications, whereas laser-specific protective glasses should be worn for greenlight laser applications.

SUMMARY

With better understanding of laser accessories, practicing urologists may tailor their practice to reach optimal efficacy and safety for Holmium:YAG, Thulium fiber laser and Greenlight laser applications.

Use of holmium laser for umbilical cord transection in a monoamniotic pregnancy threatened by an acardiac co-twin: a case report

Background

Twin reversed arterial perfusion sequence is a rare complication of monochorionic multifetal pregnancies. In this syndrome, the acardiac twin has a nonfunctional heart, while the other twin, the pump twin, has normal development. The pump twin perfuses the acardiac twin and is therefore at risk for cardiac decompensation. In monoamniotic cases, the normal co-twin is also at risk of sudden death due to cord entanglement. Treatment consists of coagulation and transection of the acardiac’s umbilical cord. We report the first intrauterine use in pregnancy of a Ho:yttrium aluminum garnet laser to safely and successfully transect the umbilical cord after Nd:yttrium aluminum garnet coagulation.

Case presentation

A 30-year-old Caucasian woman was referred to our fetal–maternal medicine unit at 9 weeks gestation with a monochorionic–monoamniotic twin pregnancy complicated by an acardiac twin. After counseling, she opted for an elective intervention to minimize the risks to the pump twin. At 16 weeks, fetoscopy was performed using a single 2-mm entry port. Through this port, a 1.0-mm fetoscope and a 0.365-mm laser fiber were introduced. Under fetoscopic sight and ultrasound (Doppler) guidance, the umbilical cord of the acardiac twin was first coagulated by laser energy using a Nd:yttrium aluminum garnet laser and then, using the same fiber, transected using a Ho:yttrium aluminum garnet laser. The patient underwent cesarean section at 38 weeks and delivered a healthy baby.

Conclusions

We present the first report on intrauterine use of an Ho:yttrium aluminum garnet laser in human pregnancy. Ho:yttrium aluminum garnet laser energy can be successfully and safely used for umbilical cord transection and carries fewer risks than other methods of transection.

Generated temperatures and thermal laser damage during upper tract endourological procedures using the holmium: yttrium-aluminum-garnet (Ho:YAG) laser: a systematic review of experimental studies

PURPOSE

To perform a review on the latest evidence related to generated temperatures during Ho:YAG laser use, and present different tools to maintain decreased values, and minimize complication rates during endourological procedures.

METHODS

We performed a literature search using PubMed, Scopus, EMBASE, and Cochrane Central Register of Controlled Trials-CENTRAL, restricted to original English-written articles, including animal, artificial model, and human studies. Different keywords were URS, RIRS, ureteroscopy, percutaneous, PCNL, and laser.

RESULTS

Thermal dose (t43) is an acceptable tool to assess possible thermal damage using the generated temperature and the time of laser exposure. A t43 value of more than 120 min leads to a high risk of thermal tissue injury and at temperatures higher than 43 °C Ho:YAG laser use becomes hazardous due to an exponentially increased cytotoxic effect. Using open continuous flow, or chilled irrigation, temperatures remain lower than 45 °C. By utilizing high-power (> 40 W) or shorter laser pulse, temperatures rise above the accepted threshold, but adding a ureteral access sheath (UAS) helps to maintain acceptable values.

CONCLUSIONS

Open irrigation systems, chilled irrigation, UASs, laser power < 40 W, and shorter on/off laser activation intervals help to keep intrarenal temperatures at accepted values during URS and PCNL.

Intrarenal temperature measurement associated with holmium laser intracorporeal lithotripsy in an ex vivo model

Introduction

The aim of this article was to quantify the effect of the use of holmium laser during intracorporeal lithotripsy in an ex vivo model.

Material and methods

A simulated model for laser nephro-lithotripsy was designed. Two ex vivo porcine kidneys were used. Electronic thermometer electrodes were inserted on the upper calyx. Intracorporeal lithotripsy was simulated with a holmium laser. Intrarenal temperature was recorded both at the beginning and after one minute of laser use with delta temperature (DT) defined as the difference between them. Measurements were made at different irrigation heights (30, 40, and 50 cm H₂O), frequency (Hz), and laser energy (J) in addition to the presence or absence of the access sheath. Analysis of factors associated with temperature change was performed.

Results

Thirty-eight observations were recorded. The measurement without the use of access sheath showed an average DT of 4.9, 5.1, and 6.5°C for 5, 10, and 15 Hz, respectively; however, with a sheath, DTs were 0.2, 0.5, and 1.5°C. In terms of energy, mean DTs of 4.3, 6.1, 5.2, and 13.9°C for 0.5, 0.8, 1.0, and 1.5 J were recorded; in contrast, with a sheath, averages of 0.4, 0.5, 0.5, and 3.8°C, respectively were noted. In the adjusted model, energy, frequency, and use of sheath and water height were significant.

Conclusions

The configuration of the laser significantly modifies the intrarenal temperature and height of the bladder irrigation. The use of an access sheath provides lower intrarenal temperatures regardless of laser configuration and water height.

Comparison of Different Pulse Modulation Modes for Holmium:Yttrium-Aluminum-Garnet Laser Lithotripsy Ablation in a Benchtop Model

Introduction: Manipulation of Holmium:Yttrium-Aluminum-Garnet laser parameters such as pulse energy (PE), frequency, and duration can impact laser lithotripsy ablation efficiency. In 2017, Lumenis introduced Moses™ Technology, which uses pulse modulation to enhance the delivery of energy from fiber to stone as well as to minimize stone retropulsion. Since the introduction of Moses Technology, other companies have brought additional pulse modulation concepts to market. The purpose of this in vitro study is to compare the pulse characteristics and stone ablation efficiency of Lumenis Moses Technology with Quanta's Vapor Tunnel™. Materials and Methods: Submerged BegoStone phantoms were systematically ablated using either the Lumenis Moses Pulse 120H or the Quanta Litho 100 clinical laser system. Two PEs (0.4 and 1 J), three fiber-stone standoff distances (SDs) (0.5, 1, 2 mm), and all available pulse duration and modulation modes for each laser were tested in combination. Fiber speed was adjusted to scan across the stone surface at either 1 or 10 pulses/mm to form single pulse craters or an ablation trough, respectively. Volumes of single craters and 1 mm trough segments were imaged and quantified using optical coherence tomography. Results: Ablation volumes decreased with decreasing PE and increasing SD. Statistically significant variability was seen between pulse types (PT) at every tested parameter set. Among pulse modulation modes, Moses Distance (MD) was superior at 0.5 mm in all testing and at 2 mm in trough testing. Vapor Tunnel (VT) was superior in 2 mm single crater testing. All modulated pulses performed similarly at 1 mm. Conclusions: In this benchtop model of laser lithotripsy, stone ablation was significantly impacted by PT. MD demonstrated superior or noninferior stone ablation at most tested parameters. VT maintained its efficacy the best as SD increased. Future work should focus on the mechanistic differences of these modes relative to other traditional laser pulse modes.

Assessment of Factors Involved in Laser Fiber Degradation with Thulium Fiber Laser

Objectives: To assess the effect of various factors on laser fiber tip degradation with the thulium fiber laser (Tm-fiber): fiber stripping, adjustable laser settings (energy, frequency, peak power), and stone density. Methods: Two hundred seventy-three micrometer fibers were used with a 50W Tm-fiber. First, we assessed the evolution of power transmission with stripped and unstripped fibers submerged in saline. The laser was continuously activated for 5 minutes. The influence of each laser parameter (energy, frequency, and peak power) on fiber degradation was assessed by loss of power transmission and reduction of tip length. Second, we assessed the evolution of power transmission after 150 seconds of lithotripsy in a quasicontact mode against soft and hard BegoStones. The influence of lithotripsy with different laser settings on fiber degradation was assessed by loss of power transmission. Results: Power transmission was close to 100% with stripped fibers, while a power gain appeared for unstripped fibers after 5 minutes of laser emission. Thus, only stripped laser fibers were used during the second series of experiments. Regardless of laser settings, there was a constant loss of measured power transmission after lithotripsy with a significant difference between soft and hard stones, p < 0.0001. Power transmission was 67% and 78% against hard and soft stones, respectively. While there was no influence of peak power on power output against hard stones, there was a significant one against soft stones. Conclusions: The main determinant of loss of power transmission during lithotripsy in contact mode with Tm-fiber is the stone density. Higher loss of power transmission occurs against hard stones than soft stones. All peak powers may be used against hard stones without a difference, while high peak power appears as an additional factor of power loss against soft stones, but this decrease will not the reach the one obtained with hard stones.

Stone ablation rates using innovative pulse modulation technology: Vapor tunnel, virtual basket, and bubble blast. An in vitro experimental study

INTRODUCTION AND OBJECTIVES

Virtual Basket^TM , Bubble Blast^TM , and Vapor Tunnel^TM are three laser pulse modulation technologies that modify the holmium: yttrium-aluminum-garnet (Ho:YAG) laser pulse transmission through the creation of bubbles emerging from the fiber tip with different effects on the target stone. The primary outcome of the current study was to test the stone ablation rates for the different pulse modulation modes, Virtual Basket, Bubble Blast, and Vapor Tunnel, using different power, energy, and frequency settings.

MATERIALS AND METHODS

Quanta Cyber: Ho 150 W^TM , a 365 µm Precision^TM fiber, and hard and soft phantom BegoStones^TM were used in an in vitro experimental configuration in a saline bath. In the Virtual Basket mode, the combinations of power, energy and frequency were tested; 10 W = 0.5 J × 20 Hz, 10 W = 0.5 J × 20 Hz, 60 W = 1 J × 60 Hz and 60 W = 2 J × 30 Hz. In the Bubble Blast mode, the combinations, 12 W = 1.2J × 10 Hz, 60 W = 1.2J × 50 Hz and 60 W = 2 J × 30 Hz, were tested. Similarly, the combination of 10 W = 0.5 J × 20 Hz was tested with Vapor Tunnel mode. High-speed camera captures of the bubble formation and regular photographs of the fragmentation pattern were also taken for each mode.

RESULTS

High power lithotripsy was faster and related to higher ablation rates. The Virtual Basket, Bubble Blast, and Vapor Tunnel modalities showed different ablation rates for the same energy and frequency settings. For hard stones, there was an improvement in the ablation rate using 60 W = 2 J × 30 Hz compared with 60 W = 1 J × 60 Hz and 60 W = 1.2 J × 50 Hz. The highest ablation rates were recorded using the Virtual Basket mode with the high-power settings of 2 J of energy and 30 Hz of frequency.

CONCLUSIONS

The Virtual Basket^TM pulse-modulation technology was related to the highest ablation rates for both hard and soft stones, compared to the Bubble Blast^TM and the Vapor Tunnel^TM technologies in high-power and low-power lithotripsy respectively. For the same high power settings, higher energy seems to provide higher ablation rates.

Temperature rise during ureteral laser lithotripsy: comparison of super pulse thulium fiber laser (SPTF) vs high power 120 W holmium-YAG laser (Ho:YAG)

PURPOSE

The holmium-YAG (Ho:YAG) Laser system is the current gold standard for laser lithotripsy (LL). Super Pulse Thulium Fiber Laser (SPTF) has emerged as an effective alternative. We compared the temperature profile of both the 120 W Ho:YAG and the 60 W SPTF systems during ureteral lithotripsy.

METHODS

Antegrade ureteroscopy with LL was performed in ex-vivo porcine kidneys with 3 mm Begostones. Intra-ureteral temperature was measured using one probe proximal and one distal to the site of lithotripsy. LL was performed using a 200 μm core fiber at dusting (SPTF-0.1 J, 200 Hz, SP; Ho:YAG-0.3 J, 70 Hz, LP) and fragmenting (0.8 J, 8 Hz, SP for both) settings for 5 s. Fifteen repetitions were recorded for each laser at each setting. Tissue samples of the ureter were collected for histological analysis.

RESULTS

There was a rise in temperature at the site of lithotripsy using both systems at every setting evaluated. The median temperatures were greater for the SPTF on the fragmenting setting (33.3 °C vs 30.0 °C, p = 0.004). On the dusting setting, the median temperature was not statistically greater for Ho:YAG (40.6 °C vs 35.8 °C, p = 0.064), (Graphic 1). Histological analysis did not show any signs of injury or necrosis in any of the tested settings.

CONCLUSION

Higher power settings used for dusting have a higher temperature rise in the ureter during lasering. Median ureteral intra-luminal temperature rise during LL was equivalent during dusting and higher in the SPTF during fragmentation, but neither reached the threshold for thermal injury based on the duration of exposure.

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.

Basic and advanced technological evolution of laser lithotripsy over the past decade: An educational review by the European Society of Urotechnology Section of the European Association of Urology

Laser disintegration of urinary stones is a cornerstone of urolithiasis treatment in the modern era. Despite the wide clinical use of stone lasers, basic and advanced technological achievements and developments are difficult to comprehend and interpret by the average urologist. A descriptive analysis of laser production and stone disintegration mechanisms was performed. We focused on physics of modern types of lithotripters, the construction of laser fibers, laser parameters, new modes, settings, and lithotripsy techniques. The main principle of laser emission remains the same since the first emitting laser was produced. Peak power density and short interaction time lead to photothermal effects responsible for stone disintegration. Modern lithotripters such as Holmium: YAG (low/high power, Moses technology) and thulium fiber laser show basic construction differences with the physical properties of the latter being superior, at least in in vitro studies. By adjusting lasing parameters, a wide spectrum of stone ablation from fragmentation to dusting can be achieved. New technology allows for the production of real dust. Knowledge of laser fiber construction and physical properties are useful in marketing and clinical use. Urologists should understand the physical and physiological background of the lasers used in their everyday practice for stone fragmentation.

"VirtualBasket" ureteroscopic holmium laser lithotripsy: intraoperative and early postoperative outcomes

BACKGROUND

The "VirtualBasket" technology is the result of pulse modulation during holmium laser emission: the laser emits part of the energy to create an initial bubble, and a second pulse is emitted when the vapor bubble is at its maximum expansion, so that it can pass through the previously created vapor channel. The aim of this study is to outline the outcomes of the "VirtualBasket" technology in ureteral and renal stones.

METHODS

160 Patients were randomly assigned to holmium laser lithotripsy with or without the "VirtualBasket" technology in ureteric or renal cases (40 per 4 groups). All procedures were performed by four experienced urologists. The Quanta System Cyber Ho 100W laser generator with 365 μm fibers was used for all of the ureteral cases, whereas, 272 μm fibers were used for all of the cases in the renal pelvis. Demographic data, stone parameters, perioperative complications and success rates were compared. A statistical analysis was carried out to assess patients data and outcomes. All of the reported p-values were obtained with the two-sided exact method at the conventional 5% significance level. The degree of stone retropulsion was graded on a Likert scale from zero (no retropulsion) to 3 (maximum retropulsion).

RESULTS

All groups were comparable in terms of age, and pre-operative stone size (ureter stone size: 1.2 vs. 1.1 cm; renal pelvis stone size: 1.55 vs. 1.62 cm). Compared to the regular mode, the "VirtualBasket" technology was associated with significantly lower fragmentation time (mean time for ureteral stones: 20.4 vs. 16.1 minutes, p<0.05; mean time for renal stones: 28.7 vs. 19.8 minutes, p<0.05) and total procedural time (mean time for ureteral stones 49 vs. 35.7 minutes; mean time for renal stones 67.1 vs. 52.4 minutes). There were no significant differences in terms of energy delivered to the stones, intraoperative complications and success rate at 1 month. The "VirtualBasket" technology was associated with significantly lower retropulsion.

CONCLUSIONS

The "VirtualBasket" technology is associated with significantly lower fragmentation and procedural times. The reduced fragmentation time is a result of the significantly lower retropulsion of the stones during laser lithotripsy, which improves stone fragmentation efficiency.

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.

A scoping review of the clinical efficacy and safety of the novel thulium fiber laser: The rising star of laser lithotripsy

INTRODUCTION

The holmium:yttrium-aluminum-garnet (Ho:YAG) laser is the gold standard for intracorporeal lithotripsy. Preclinical reports suggest the thulium laser fibre (TFL) may possess advantages over the Ho:YAG laser, including improved lithotripsy efficacy, enhanced safety, and lower costs. Although the TFL is well-characterized in-vitro, there are no reviews examining TFL lithotripsy in a clinical setting.

METHODS

A review of the literature was conducted using a systematic search of MEDLINE, PubMed, and Embase, yielding a total of 130 manuscripts published up to May 2020. Two independent reviewers selected studies for screening, eligibility, and inclusion into the scoping review. Following the title, abstract, and full-text review, 14 articles were analyzed.

RESULTS

Within these articles, there were 13 prospective cohort studies and one case series. The average sample size was 100 participants. Study followup durations ranged from four weeks to three months. TFL had comparable stone-free rates to Ho:YAG lasers and improved operating time. TFL was subjectively favorable in terms of stone retropulsion, stone fragmentation, endoscopic maneuverability, and endoscopic visibility. TFL appeared clinically safe and did not result in any major complications. Many studies were underpowered and non-peer-reviewed, demonstrating the need for additional research in this field.

CONCLUSIONS

The TFL has the potential to catalyze a paradigm shift in laser lithotripsy. While the objective of this scoping review was to describe the contemporary landscape of the literature, it is important to consider that inferences posed by the studies described herein must be tempered by the low quality of available evidence.

Pulsed lasers and endocorporeal laser lithotripsy

Endocorporeal laser lithotripsy (ELL) is currently the gold standard for the treatment of renal stones during retrograde intra-renal surgery (RIRS). The newly-authorised thulium fibre laser (Tm-Fibre) in now evaluated as a holmium:yttrium-aluminium-garnet (Ho:YAG) laser alternative, which is the most well-known laser source for ELL. This update aimed to present the fundamentals of pulsed lasers for EEL [technology, period, pulse characteristic (rate, duration, energy, shape), peak power, average power], and the available lithotripsy modes for both Tm-Fibre and Ho:YAG lasers.

The optimal settings of holmium YAG laser in treatment of pediatric urolithiasis

The aim of this study is to present our experience on the use of the holmium:yttrium-aluminum-garnet (Ho:YAG) laser in pediatric patients for pediatric urolithiasis and describe the optimal settings. A total of 116 children who underwent urolithiasis treatment (percutaneous nephrolithotomy (PNL), ureterorenoscopy (URS), retrograde intrarenal surgery (RIRS)) were included. The mean age of the patients was 8.4 ± 5.2 years (1-18). The mean follow-up was 26 ± 8.8 months (9-45). There was no difference between the mean stone sizes of PNL and RIRS patients (p = 0.816). Operations were performed with 200, 272, and 365-μm fibers. In mini-URS, stone fragmentation was achieved with the energy settings set between 0.5 and 1 J and frequency set to > 8 Hz. In RIRS, fragmentation was achieved with the setting of 0.5-0.8 J at 10-20 Hz. Stone fragmentation was performed with energy settings of 0.8 to 2 J between 5 and 15 Hz for PNL. There was no significant difference between the stone-free rates of the PNL and RIRS (p = 0.150). Four postoperative complications occurred (Clavien II), which included febrile urinary infections in two patients who underwent mini-URS, one patient who underwent PNL, and one patient who underwent RIRS. Our results confirmed that Ho-YAG laser can be effectively used in children for stone treatment by using low-energy high-frequency settings for URS and RIRS and a high energy setting for PNL.

Microrobotic laser steering for minimally invasive surgery

The creation of multiarticulated mechanisms for use with minimally invasive surgical tools is difficult because of fabrication, assembly, and actuation challenges on the millimeter scale of these devices. Nevertheless, such mechanisms are desirable for granting surgeons greater precision and dexterity to manipulate and visualize tissue at the surgical site. Here, we describe the construction of a complex optoelectromechanical device that can be integrated with existing surgical tools to control the position of a fiber-delivered laser. By using modular assembly and a laminate fabrication method, we are able to create a smaller and higher-bandwidth device than the current state of the art while achieving a range of motion similar to existing tools. The device we present is 6 millimeters in diameter and 16 millimeters in length and is capable of focusing and steering a fiber-delivered laser beam at high speed (1.2-kilohertz bandwidth) over a large range (over ±10 degrees in both of two axes) with excellent static repeatability (200 micrometers).

Thulium fiber laser utilization in urological surgery: A narrative review

The thulium fiber laser (TFL) is a novel technology under active investigation as an conceivable alternative to the Holmium:yttrium-aluminum-garnet (Ho:YAG) laser, which is currently the gold standard for an array of urologic procedures. The purpose of this review is to discuss the existing literature on the functionality and effectiveness of TFL in urological practice. We conducted a search of the PubMed, Medline, Web of Science Core Collection, SCOPUS, Embase (OVID), and Cochrane Databases for all full articles and systematic reviews on the TFL. We found a total of 35 relevant pieces of literature. The early research findings pertaining to the TFL exhibit numerous potential advantages over the Ho:YAG laser. In vitro and ex vivo studies have highlighted the TFL's ability to utilize smaller laser fibers, obtain faster stone ablation rates, and achieve less retropulsion when tested against the Ho:YAG laser in lithotripsy. Currently, there is limited in vivo research that investigates the utilization of the TFL. The in vivo results that are available, however, look promising both for laser lithotripsy and soft tissue ablation. Indeed, the existing literature suggests that the TFL has great potential and may possess numerous technological advantages over the Ho:YAG laser, especially in laser lithotripsy. Although these early studies are promising, randomized control trials are needed to assess the full applicability of the TFL in urology.

High-power, High-frequency Ho:YAG Lasers Are Not Essential for Retrograde Intrarenal Surgery

There is currently insufficient in vivo evidence that high-power Ho:YAG lasers improve retrograde intrarenal surgery or the ablation efficacy. While prospective trials are awaited, a low-cost, silent, low-power Ho:YAG laser that requires only a standard electrical outlet is more than sufficient for retrograde intrarenal surgery.

Laser lithotripsy for proximal ureteral calculi in adults: can 3D CT texture analysis help predict treatment success?

OBJECTIVE

To explore whether multiple 3D computed tomography texture analysis (3D-CTTA) parameters can predict the therapeutic effects of holmium: YAG laser lithotripsy (LL) on ureteral calculi.

METHODS

The files from 94 patients (102 stones) with proximal ureteral calculi treated only by LL at a single institution were retrospectively retrieved from January 2016 to March 2019. According to intra-operative observations and postoperative reexamination, samples were divided into a completely crushed and a non-crushed group. Preoperative non-contrast-enhanced computed tomography (NCCT) images obtained by multiple CT scanners were imported to MaZda software for 3D texture analysis (TA). The CT-derived value of each target stone was measured, and 15 TA parameters were extracted by delineating volumes of interest (VOIs). Receiver operating characteristic (ROC) curves were drawn to determine the optimal critical value of each parameter based on the Youden index, and univariable and multivariable logistic regression analyses determined the significant factors for LL success.

RESULTS

In univariable analysis, significant differences (p < 0.05) were observed among 7 parameters. In multivariable analysis, Perc.01 3D > 2062 (p = 0.03) and Z-fraction of image in runs (Z-Fraction) > 0.45570 (p = 0.009) were significant independent predictors, with odds ratios (ORs) of 24.204 and 60.329, respectively. In subgroup analysis based on the cutoff value of the CT-derived value (HU = 960), Perc.01 3D (OR = 44.154, 95% CI (2.379, 819.618), p = 0.011) and Z-Fraction (OR = 14.519, 95% CI (2.088, 100.953), p = 0.007) remained statistically significant.

CONCLUSIONS

The combination of 3D-CTTA parameters and the CT-derived value can be used as a quantitative reference to predict whether a target stone could be completely crushed by LL.

KEY POINTS

• Computed tomography texture analysis (CTTA) may be helpful in selecting suitable laser lithotripsy (LL) patients. • 3D-CTTA better predicts stone fragility than commonly used methods (such as the CT-derived value). • The combination of CTTA and the CT-derived value can be used as a preoperative quantitative reference.

Impact of Laser Fiber Diameter and Irrigation Fluids on Induced Bubble Stream Dynamics with Thulium Fiber Laser: An In Vitro Study

Objectives: The Thulium Fiber Laser (TFL) is studied as an alternative to the holmium:yttrium-aluminium-garnet (Ho:YAG) laser for lithotripsy, with the advantage of an induced bubble stream (IBS). This in vitro study compared the TFL's IBS with 150- and 272 μm-core-diameter laser fiber (CDF) and in four irrigant fluids. Methods: A TFL of 50 W (IPG Photonics^©) and 150 and 272 μm-CDF (Boston Scientific^©) were used, comparing nine energies (in the range from 0.025 to 4 J). An experimental setup consisted of a vertically disposed fiber in a cuvette filled with saline, iodinated contrast agent (IOA), human urine, or deionized water (DW) at ambient temperature. High-speed imaging of three consecutive IBS was performed to determine the influence of energy on their maximum length (ML; μm), width (MW; μm), and duration (MD; μs). Fibers were cleaved with ceramic scissors between each experience. Results: The IBS had higher ML and MW and MD with 150CDF than 272CDF. Maximum pulse rate for 150CDF and 272CDF was 2182 and 2000 Hz, respectively. Every maximum power was higher than the technological limit of TFL (>50 W). At equal energy density, 150CDF was associated with lower dimensions and durations. The IBS had higher maximum dimensions in IOA compared with saline solution (SS). Compared with DW and urine, IBS in IOA were longer beyond 500 mJ. Over 25 mJ, IBS were thinner in DW, urine, and SS. The IBS in DW, urine, and SS had similar maximum dimensions. The IBS's duration was higher in IOA compared with DW, urine, and SS, meaning a lower theoretical maximum pulse rate and power in IOA. Conclusion: Lasering with 150CDF fits with lower pulse energies-higher pulse rates settings than 272CDF, such as fine dusting mode. In IOA, Induced Bubbles Streams present higher dimensions and durations than in other studied fluids, related to its higher viscosity. Safety distance and pulse rate should be increased and decreased, respectively.

Influence of the laser pulse shape in the treatment of stones in the upper urinary tract

PURPOSE

Urinary stones can be successfully treated using a Holmium: Yttrium-Aluminum-Garnet (Ho: YAG) laser. Regarding success rates, laser pulse energy, frequency, and pulse width are well-known contributing factors. Whether the pulse shape might be a further factor influencing the laser efficiency is unclear. This study aimed to evaluate different modes of laser pulse shapes in a real-world setting.

MATERIALS AND METHODS

The Dornier Medilas® H Solvo (Weßling, Germany) was used in the treatment of ureter and kidney stones. Patients were randomized into standard pulse shape (SPS) and new pulse shape groups (NPS1; ureter) and (NPS2; kidney pelvis), depending on the stone localization. The primary endpoint was laser efficiency defined as mm³ stone destruction per overall operating time. Secondary endpoints encompassed number of stone recoveries and stone-free rate.

RESULTS

Altogether 145 patients (24 SPS vs. 32 NPS1; 51 SPS vs. 38 NPS2) were included. No differences in sex, age, body mass index, stone localization and stone composition were found, except for preoperative stone size (133±95 [SPS] vs. 197±139 [NPS1] mm³; p=0.023) and (348±298 [SPS] vs. 525±429 [NPS2] mm³; p=0.042). Regarding the primary endpoint, a significant increase in laser efficiency could be detected for the NPS1 and NPS2 groups compared to the SPS groups (39.9±44.9 vs. 28.8±30.2 and 51.7±61.3 vs. 22.4±24.2 mm³/min [mean±standard deviation]). No statistically significant differences were found for secondary endpoints and perioperative complication rates.

CONCLUSIONS

Efficiency of the Ho: YAG laser can be positively influenced by different pulse shapes. This adds the variable of individualized intraoperative decision making.

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.

Intraductal Lithotripsy in Sialolithiasis Using the Calculase III™ Ho:YAG Laser: First Experiences

BACKGROUND AND OBJECTIVES

To report the first experiences with a newly available Ho:YAG laser system for the treatment of salivary stones.

STUDY DESIGN/MATERIALS AND METHODS

A retrospective study in a tertiary referral center was conducted. Patients diagnosed with sialolithiasis were treated in Erlangen using the Calculase III™ Ho:YAG laser (Karl Storz, Tuttlingen, Germany). Preset parameters had a frequency of 4 Hz and energy of 0.8-1.2 J, resulting in 3.2-4.8 W. Following total fragmentation, one to two serial sialendoscopies were performed to achieve complete fragment clearance.

RESULTS

A total of 55 stones in 49 patients were treated; 17 stones in 15 submandibular glands and 38 in 34 parotids. In total, 61 laser lithotripsies (range 1-3 per stone) were performed using various modes (long, short, and burst) and with preset parameters of 4 Hz and energy of 0.8-1.2 J, resulting in effective power of 3.2-4.8 W. Complete fragmentation was achieved in all the accessible stones. Sialendoscopes, fibers, or the mode used had no significant influence on success rates. A multimodal therapy concept was employed to treat stones in 12.24% of the cases; 95.92% of the patients were ultimately stone-free, and all became symptom-free. All glands were preserved.

CONCLUSIONS

The new Calculase III™ Ho:YAG laser was effective in the treatment of sialolithiasis with no increased risk of complications in the patients or damage to the sialendoscopes. Clinical factors such as the type of gland involved, or the location and size of stones had a greater impact on success rates than the technical or preset parameters. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.