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

Effect of Pulse Modulation on Diode-Pumped Laser Lithotripsy

Introduction: This study addresses pulse modulation for kidney stone lithotripsy using diode-pumped thulium yttrium aluminum garnet (Tm:YAG, λ = 2.02 µm) and thulium fiber lasers (TFLs, λ = 1.94 µm). Three research questions were investigated: (1) What are the effects of varying pulse duration and energy of the first pulse and varying the interpulse delay in a pulse modulation sequence to increase energy transfer across saline to a stone? (2) Does an optimal pulse modulation profile exist in a single-pulse sequence to provide highest percent radiant energy transfer? (3) Does a higher effective energy transfer to the stone using pulse modulation produce greater stone volumetric removal? Materials and Methods: We measured radiant energy transmission efficiency (RETE) and ablation volumes in phantom and human stones. RETE was utilized to compare the pulse energy transmission through air and saline media. We recorded fast camera traces and vapor bubble collapse pressures. Craters were created at fiber standoff distances (SDs) of 0.0 mm, 0.5 mm, and 1.0 mm, and volumes were measured using optical coherence tomography. Results: For Tm:YAG laser irradiation, dual-pulse mode significantly increased RETE by as much as 75% at 1 mm SD compared with single-pulse mode. With the Tm:YAG laser, an optimal "dual-pulse" modulation resulted in greater volumetric removal compared with a "single-pulse" across all stone cohorts (p < 0.05) except for calcium oxalate monohydrate stones (p = 0.38) at a 1 mm SD. TFL yielded similar results, but showed heterogeneity across stone compositions. Conclusions: Pulse-modulated diode-pumped Tm:YAG and TFL can deliver higher photon count through a saline layer if the first pulse is optimized. An optimal pulse modulation profile where the second pulse is synchronized with the vapor bubble dynamics of the first pulse results in the highest percent RETE and increased stone volumetric removal.

Stone dust in endourology: a systematic review of its definition, management, and clinical impact

OBJECTIVE

To evaluate and synthesise the existing literature on stone dust (DUST) in endourology, focusing on its definition, creation methods, and removal techniques.

METHODS

A comprehensive electronic literature search was conducted using the PubMed/Medline, Web Of Science, and Embase databases to identify reports published until October 2024. The Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines were followed to identify eligible studies. The outcomes assessed included the definition of DUST, the method by which DUST was created, and how it was removed, evaluating both in vitro and in vivo studies. The review also assessed the efficacy of different laser technologies, including holmium-yttrium-aluminium-garnet (Ho:YAG) laser, thulium fibre laser (TFL), and pulsed thulium-YAG laser (p-Tm:YAG) laser, in generating DUST and their clinical relevance in stone management.

RESULTS

The systematic review identified 43 eligible studies, revealing significant variability in the definition and evaluation of DUST. Criteria for DUST ranged from sub-millimetre particle sizes to functional properties like floatability and aspiration capability. While Ho:YAG lasers remain widely used for stone dusting, emerging technologies such as TFL and p-Tm:YAG lasers have shown superior efficiency in producing finer particles and reducing retropulsion. No consensus emerged regarding the settings used by surgeons and the pre-settings provided by laser manufacturers.

CONCLUSIONS

Despite the widespread use of dusting techniques in endourology, a standardised definition of DUST remains lacking, with significant variability in laser settings, particle sizes, and evacuation methods. It must be clarified whether DUST should be defined as a noun-representing a distinct entity with a precise definition-or as the result of the dusting process, in which case clear criteria are needed to characterise it accurately. Establishing standardised definitions and protocols through international consensus is crucial to optimising clinical outcomes and ensuring consistency in future research.

Propensity Score Matched Analysis of Thulium Fiber vs Pulsed Thulium:Yttrium Aluminum Garnet Laser Lithotripsy in Flexible Ureteroscopy for Kidney Stone Disease Using a Flexible and Navigable Suction Ureteral Access Sheath: Results From a Prospective, Multicenter Study of the EAU Section of Endourology

OBJECTIVE

To evaluate outcomes after flexible ureteroscopy (F-URS) for renal stone(s) using a flexible and navigable suction ureteral access sheath (FANS-UAS) comparing Thulium fiber (TFL) vs pulsed Thulium:Yttrium aluminum garnet (p-Thulium:YAG) laser.

METHODS

Data from adults who had F-URS in 5 centers were prospectively collected (April 2023-January 2024). All patients had a preoperative and within 30days CT scan. Stone-free: grade A: zero fragments; grade B: single fragment ≤2mm; grade C: single fragment 2.1-4mm; grade D: single/multiple fragments >4 mm. One-to-one propensity score-matching for age, gender, prestenting, stone volume, stone location, and Hounsfield units was performed. Within 6months after surgery, an intravenous urography or CT urography scan was performed in all patients.

RESULTS

Of 179 included patients, TFL was employed in 115 patients. After matching, 64 patients from each group with comparable baseline characteristics were included. Median lasing time was significantly longer in the TFL group (15.5 [10,23] minutes vs 13 [10,15] minutes, P=.02), while total surgical time did not differ. There was no case of blood transfusion and sepsis. Overall stone-free rate (SFR) was significantly different between the groups with a higher proportion of patients in p-Thu:YAG laser group undergoing reintervention for residual fragments (17.2% vs 3.1%). There was no case of new-onset hydronephrosis, ureteropelvic junction/ureteral stenosis, impaired urinary drainage, or altered pelvicalyceal anatomy at a median follow-up of 13weeks.

CONCLUSION

F-URS using FANS-UAS showed negligible serious adverse events and good SFR using both lasers. p-Thu:YAG laser showed shorter lasing time, marginal better grade A+B SFR but higher reintervention rate for residual fragments.

Evaluation of pulse modulation settings for optimal pop-dusting efficiency using the Quanta Litho 150 laser: An in vitro study

Purpose

The novel Quanta Litho 150 W (Samarate, Italy) was recently introduced and incorporates new pulsed modulation settings. We sought to analyze ablation rate and efficiency in short pulse (SP), virtual basket (VB), and vapor tunnel (VT) pulsed modulations, in an in vitro pop-dusting simulation across different settings at a fixed power of 30 Watts (W) and fixed periods of time.

Materials and Methods

Seven millimeter BegoStone phantoms were subjected to lithotripsy in a simulated calyx using Holmium: yttrium:aluminum garnet Quanta System 150 W. 30 W was applied at different settings across three pulse modulation modes: SP, VB, and VT. Ablation rate and efficiency were and compared between the three groups.

Results

Maximum ablation efficiency for the VB and VT groups was achieved at VB 2J x 15 Hz and VT at 2.5 J x 12 Hz. Ablation efficiency decreased with higher Joules. VB at 1.5 J x 20 Hz and SP at 2.5 J x 12 Hz were the only settings to obtain 85% ablation at 5 min.

Conclusions

In vitro laser lithotripsy using a BegoStone phantom, VB at 2J x15 Hz and VT at 2.5 J x 12 Hz were the most efficient setting for pop-dusting with the Quanta Litho 150. The highest efficiency (mg/min) was achieved with VB at 2 J x 15 Hz and VT at 2.5 J x 12 Hz at 1:15 min.

Optimal stone density for ablation lithotripsy with vapor tunnel Ho:YAG pulse modality

INTRODUCTION

Vapor-Tunnel™ (VT) consists of a very long pulse that uses the minimum peak power, causing the energy to pass through a previously created vapor channel or tunnel. There are studies that have shown acceptable ablation lithotripsy efficiency. Nevertheless, there are no in-vivo studies that have compared the VT performance according to the stone density.

METHODS

A retrospective study of 152 patients who underwent RIRS using VT Ho:YAG laser was performed. We divided the patients according to the stone density (Group 1: < 1000UH vs. Group 2: > 1000UH). We assessed the lithotripsy efficiency (mm3/JJ) and the laser-energy consumption (JJ/mm3). The stone-free rate (SFR) was defined as the absence of stone fragments in a non-contrast abdominal computed tomography 4 weeks after the procedure.

RESULTS

Ninety three patients were included in Group 1 and 59 in Group 2. Body mass index was higher in Group 1 and the median stone volume was higher in Group 2 (846 vs. 672 mm3, p = 0.03). Total energy used (11.9 vs. 24 kj, p < 0.001), the laser emission time (19 vs. 30 min, p < 0.001), and the total operative time (60 vs. 85 min, p < 0.001) were lower in the Group 1. SFR was higher in Group 1 (96.7% vs. 57.6%, p < 0.001) with a global SFR of 81.6%. The ablation lithotripsy efficiency was higher in Group 1 (0.053 mm3/JJ vs. 0.035 mm3/JJ, p < 0.001).

CONCLUSIONS

VT Ho:YAG was associated with decreased laser time, operative time and laser-energy consumption in Group 1 than Group 2. Similarly, VT Ho:YAG increased lithotripsy efficiency and the SFR compared to hard stones with the same laser settings and pulse modality.

Renal and ureteral temperatures changes during ureteroscopic pulsed thulium: YAG laser lithotripsy: an in vitro analysis

Introduction

Promising studies have shown a high stone-free rate achieved with the pulsed solid-state thulium YAG laser. However, studies on its safety concerning temperature effects during activation remain limited. The aim of this study was to characterize temperature variations during laser activation.

Material and methods

This in vitro experimental study utilized a high-fidelity uretero-renal simulation model to assess temperature changes during intracorporeal laser lithotripsy. Temperatures reached after laser activation at 15, 20, and 30 seconds were recorded. The flow rates used were 10 ml/min and 20 ml/min. The maximum allowed temperature was set at 43°C, given its association with thermal tissue damage. A linear logistic regression model was used to analyze variations and project temperature behavior over time.

Results

In the renal model, temperature increases were correlated with the applied energy. With a 10 ml/min flow rate, no laser configuration exceeded 43°C at 15 seconds; at 20 seconds, only the 30 W (2.5 J/20 Hz) configuration exceeded this temperature. By 30 seconds, all 30 W configurations exceeded 43°C, except for 0.4 J/75 Hz. With a 20 ml/min flow rate, no laser configuration exceeded 43°C. The 20 ml/min flow rate decreased renal temperature by 1.96°C (p = 0.01). In the ureteral model, the temperature increase was not proportional to the applied energy, but in no scenario the temperatures reach the 43°C.

Conclusions

The temperature variations observed in this study with the use of the pulsed solid-state thulium YAG laser should be considered to avoid potential renal and ureteral thermal damage.

Differences in lasers and laser technologies: what does a clinician need to know?

PURPOSE OF REVIEW

This review focuses on recent advancements in laser technologies used in urology, particularly in enucleation, vaporization, lithotripsy, and focal laser ablation (FLA). The growing use of the thulium fiber laser (TFL) and the development of pulsed thulium lasers (p-Tm:YAG) highlight the relevance of this review, as these innovations aim to improve precision and outcomes in urological procedures.

RECENT FINDINGS

Recent studies have shown the advantages of TFL in achieving precise tissue ablation, reduced retropulsion offered by the Moses technology in holmium lasers, and the potential of pulsed thulium lasers for more precise control of the effects on tissues. Additionally, FLA is gaining traction for its ability to treat localized prostate cancer with minimal collateral damage. These technologies not only optimize procedural accuracy but also reduce complications, making them safer for high-risk patients, including those receiving anticoagulants.

SUMMARY

The advancements in laser technology, including TFL, Moses technology, and pulsed thulium lasers, are improving outcomes in urological surgeries by increasing precision, reducing operative time, and minimizing complications. FLA represents a promising alternative for minimally invasive cancer treatments. Ongoing research should focus on optimizing laser parameters and exploring broader clinical applications.

Harnessing magnetism: evaluation of safety, tolerance and feasibility of magnetic kidney stone retrieval in vivo in porcine models

The primary objective of urolithiasis therapy is complete stone removal and highest stone-clearance rates possible to minimize recurrence. A novel approach that employs a magnetic suspension and a magnetic probe for the passive collection and removal of small residual fragments was developed. This study assessed the feasibility of this system in porcine models. Five female domestic pigs underwent retrograde intrarenal surgery under general anaesthesia to assess the new magnetic system. Pre-analysed human calculi were endoscopically inserted and comminuted using lithotripsy. The magnetic suspension was applied, and the magnetic-stone fragment complex was extracted. After nephrectomy, independent blinded pathologists evaluated all the kidneys. Safety and tolerance assessments revealed no adverse events (i.e. no complications on the Clavien-Dindo scale > 1) or complications associated with treatment. This study revealed superficial urothelial damage in all animals, characterized by desquamation and inflammation, caused primarily by the insertion of access sheaths and laser lithotripsy. Residual magnetic particles were observed in the renal pelvis but did not show signs of toxicity even though this study is limited to the acute treatment. No pathological indicators were observed in the hemogram and urinalysis. Overall, the treatment did not cause any significant pathological changes. Preclinical in vivo evaluation of magnetic extraction of small rest fragments in porcine kidneys presents a promising, atraumatic approach for fragments removal. It demonstrated safety, tolerance, and feasibility that warrants clinical investigation. This method has the potential to increase stone-clearance rates with shorter extraction times, offering a possibility for addressing the challenge of urolithiasis in clinical practice.

Simulation of the temperature distribution of kidney stones induced by thulium fiber laser and Ho: YAG laser lithotripsy

Simulation studies on temperature distribution in laser ablation help predict ablation rates, laser settings, and thermal damage. Despite the limited number of reported numerical studies on the temperature distribution of kidney fluid, there is no simulation study for kidney stone temperature distribution. We employ a numerical approach to study the kidney stone temperature distribution and predict ablation rates, which is an important parameter for clinical lithotripsy. The study looked at how the thulium fiber laser and the Ho:YAG laser differ in terms of temperature profile and ablation depth of kidney stones like calcium oxide monohydrate. The ablation depth increased from 152.7 µm to 489.7 µm when the TFL laser (operated at 10 Hz repetition rate and 1 ms pulse width) fluence increased from 764 J/cm2 to 1146 J/cm2. Correspondingly, the depth increased from 21 µm to 68 µm for the Ho: YAG laser operated at 3 Hz and 0.22 ms pulse width. We attribute this to an increase in temperature with laser energy. We further investigated the effect of pulse width on ablation depth by considering three different TFL pulse widths: 0.5 ms, 0.75 ms, and 1 ms. There was a decrease in ablation depths from 402.5 µm to 242.6 µm when the pulse width increased from 0.5 ms to 1 ms. Because of lower water absorption coefficients, the Ho:YAG laser (70 mJ/10 Hz) produced a smaller ablation depth and temperature profile than the thulium fiber laser (70 mJ/10 Hz). Experimental results from the literature validated the simulation. We found that the Ho:YAG laser worked better for ablation when it was set to 0.2 J/100 Hz for the Ho:YAG laser and 0.4 J/50 Hz for the TFL laser, which were clinical laser settings that we found in the literature. This indicates that, in addition to laser absorption by water, the laser parameters also significantly influence temperature distribution and ablation.

Flexible Ureteroscopic Lithotripsy with the Pulsed Thulium:Yttrium Aluminum Garnet Laser Thulio: Preliminary Results from a Prospective Study

Background and objective

Recently, the new pulsed thulium:yttrium aluminum garnet (p-Tm:YAG) laser technology has been introduced in endourology for lithotripsy. The aim of this study was to assess and validate the clinical laser performance and safety profile of p-Tm:YAG laser in a series of patients with renal and ureteral stones who underwent flexible ureteroscopy (fURS).

Methods

Prospective data were collected for patients who underwent fURS with the p-Tm:YAG laser Thulio (Dornier MedTech Systems GmbH, Wessling, Germany) at our institution by using two different laser fiber core diameters (270 and 200 μm). The primary endpoint of the study was stone-free rate (SFR), and the secondary endpoints were Clavien-Dindo complications grade ≥1 and the comparison between laser fibers of different diameters in all the parameters analyzed. Descriptive statistics relied on medians and interquartile ranges for continuous covariates, and on frequencies and percentages for categorical covariates. After stratification according to fiber types, differences between groups were tested with Wilcoxon and chi-square tests as appropriate. All the analyses and graphics were performed using R software (version 4.2.2).

Key findings and limitations

The SFR was 82% at 1-mo follow-up. In six out of 50 procedures (12%), Clavien-Dindo grade I-II complications were recorded. There were no differences regarding all the laser parameters considered between patients who were treated with 270 or 200 μm laser fibers (p > 0.05). Limitations of the study include small sample size in a single center and the lack of comparative groups.

Conclusions and clinical implications

In this prospective study of 50 patients who underwent fURS for ureteral and renal stones, the p-Tm:YAG laser Thulio was both effective and safe in a short-term follow-up. More prospective randomized studies in larger populations using different laser sources are required to confirm the clinical laser performance and safety of p-Tm:YAG laser for urinary stones treatment.

Patient summary

In this report, we looked at the outcomes for the pulsed thulium:yttrium aluminum garnet laser Dornier Thulio in patients who underwent flexible ureteroscopy for ureteral and renal stones. We found that this new laser technology is effective and safe, representing a good alternative to the other laser machines available for stone lithotripsy. We need more studies with larger populations to establish the superiority of this laser technology over the others.

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.