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

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.

Laser lithotripsy of a brushite crystalline aggregate stone model: fragment distribution vs. BegoStone and human stones

Laser research is hampered by a lack of accurate stone models that replicate fragmentation during laser lithotripsy. We sought to assess the distribution of stone fragments from laser ablation of new brushite crystalline powder and brushite crystalline aggregate stone models and compare with human stones and BegoStone. Samples of 15:3 and 15:5 BegoStone, powder, and aggregate model stones were tested alongside human CHPD and COM stone samples. All samples were secured and hydrated before Ho: YAG laser energy was delivered (Lumenis P120H) using a 200-micron D/F/L fiber. Lithotripsy was performed by repeatedly translating the fiber automatically through a predetermined grid of points (MATLAB program) until > 50% of each sample was ablated. Fragments were separated by sieving. For each stone type, 70.2-96.9% of the mass of fragments consisted of particles smaller than 0.25 mm. The percentage by mass of fragments greater than 1 mm in trials with 0.8 J x 10 Hz settings was 0.5%, 0.0%, 1.1% and 5.1% for BegoStone 15:3, BegoStone 15:5, powder model, and aggregate model respectively, compared to 5.5% for CHPD and 16.2% for COM. Only the aggregate model, CHPD and COM samples produced fragments > 2 mm. The new aggregate model stone better replicates the fragment distribution of human stones after laser lithotripsy. The method of producing the aggregate model stone - incorporating crystal and chemical components found in urinary stones - holds promise for developing better stone models needed to address a range of important lithotripsy research questions.

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.

Development of an Alginate Gel Composite with Antibacterial Properties Capable of Binding Calcium-Based Residual Stone Fragments in Endoscopic Stone Surgery

Background: Complete removal of urinary stones remains a challenge, as residual fragments can contribute to recurrence and postoperative urinary tract infections. This study presents an initial laboratory investigation into the development of an alginate gel composite designed to bind calcium-based stone remnants and exhibit antibacterial properties. Methods: To evaluate gel formation, calcium oxalate powder reagent and sodium alginate (SA) powder reagent were mixed in a Becker glass and stirred on a hot plate. Stones from 17 patients who underwent stone surgery were crushed, and gel formation was confirmed using the same experimental conditions with SA powder reagent. A gel composite material containing silver nitrate and vancomycin was prepared, and antibacterial activity against Staphylococcus aureus and Escherichia coli was tested over a 5-minute period. A mixture of 0.5 g alginic acid and 0.05 g calcium oxalate monohydrate powder reagent with 50 mL distilled water formed a gel after 30 minutes. Results: Sandy stones composed of calcium oxalate formed a better gel composite when mixed with SA than those composed of uric acid. In the antibacterial test of the alginate gel composite containing silver nitrate and vancomycin against S. aureus and E. coli, the number of live bacteria in the control and alginate gel composite was 3.5 × 103 and <10, respectively. Conclusion: This study represents a preliminary laboratory investigation into the development of an alginate gel composite for potential use in urinary stone management. Further preclinical studies are necessary to evaluate its efficacy and safety before clinical translation.

Direct-in-scope suction with a 5.1Fr large working channel ureteroscope: what stone dust size for effective evacuation during laser lithotripsy? An in vitro analysis by PEARLS and section of EAU Endourology

PURPOSE

A novel larger 5.1Fr working channel flexible ureteroscope for Direct-In-Scope Suction (DISS) has recently been introduced. However, the optimal stone dust size for successful evacuation without working channel blockage is currently unknown.

METHODS

In vitro assessment of the PU400A 9.2Fr ureteroscope (Zhuhai Pusen Medical Technology Co., Ltd, China) was performed with BegoStone particle sizes ≤ 2000 μm (size range 1000-2000 μm), ≤ 1000 μm (500-1000 μm), ≤ 500 μm (250-500 μm), ≤ 250 μm (125-250 μm) and ≤ 125 μm (63-125 μm), in a kidney calyx model. This was conducted with an empty working channel, and with occupancy by 150 μm Olympus, 200 μm Quanta, 270 μm Dornier laser fibers. Primary outcome was complete suction-evacuation without working channel blockage. Secondary outcome was evacuation speed for particle sizes that did not have blockage.

RESULTS

A stone particle size upper limit of 250 μm was found to achieve complete suction-evacuation without blockage, across all working channel occupancy situations. For stone particle size of range 125-250 μm, evacuation speeds were 35, 26, 13, 11 mm3/s across empty, 150 μm Olympus, 200 μm Quanta, 270 μm Dornier laser fiber occupancy, respectively (ANOVA = p < 0.001). For stone particle size range 63-125 μm, evacuation speeds were 19, 14, 9, 8 mm3/s respectively (ANOVA = p < 0.001).

CONCLUSION

The 5.1Fr working channel DISS ureteroscope allows a stone particle size limit of 250 μm to be suction-evacuated without blockage, even with laser fiber occupancy. With a laser fiber, a smaller 150 μm fiber size allows better particle evacuation speeds. Urologists should therefore aim for a dust particle size of ≤ 250 μm in routine DISS with the 5.1Fr working channel ureteroscope, for effective intraoperative stone evacuation.

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.

Kidney Stones as Minerals: How Methods from Geology Could Inform Urolithiasis Treatment

Despite the recent advances in minimally invasive surgery, kidney stones still pose a significant clinical challenge due to their high recurrence rate of 50% in 5-10 years after the first stone episode. Using the methods of geosciences and biology, the GeoBioMed approach treats kidney stones as biogenic minerals, offering a novel perspective on their formation and dissolution processes. In this review, we discuss kidney stones' structural and mechanical properties as emerging biomarkers of urolithiasis, emphasizing the importance of a comprehensive stone analysis in developing personalized treatment strategies. By focusing on unexplored properties like crystalline architecture, porosity, permeability, cleavage, and fracture, alongside the conventionally used composition and morphology, we show how these stone characteristics influence the treatment efficacy and the disease recurrence. This review also highlights the potential of advanced imaging techniques to uncover novel biomarkers, contributing to a deeper understanding of stone pathogenesis. We discuss how the interdisciplinary collaboration within the GeoBioMed approach aims to enhance the diagnostic accuracy, improve the treatment outcomes, and reduce the recurrence of urolithiasis.

Thulium fiber laser versus pulsed Thulium:YAG for laser lithotripsy during flexible ureteroscopy

To compare the pulsed-Thulium: YAG(p-Tm: YAG) and Thulium Fiber(TFL) lasers in terms of efficiency and safety profiles during flexible ureteroscopy(fURS) and endocorporeal laser lithotripsy(ELL). A prospective single-center open-label comparative study included consecutive patients with ureteral and renal stones who underwent fURS using Thulio(p-Tm: YAG, Dornier©,Germany) or TFL Drive(TFL, Coloplast©,Danemark), with 270 μm and 150/200μm laser fibers(LF), respectively. fURS were performed by a single operator in each group. Demographics, stone size, stone density, laser-on time(LOT) and laser settings were recorded. Ablation speed(mm3/s), energy consumption(J/mm3) values for each procedure were also assessed. Stone-free rate(SFR, <3 mm fragments) and zero fragment rate(ZFR) on non-contrast computed tomography within 3 months postoperatively were also recorded. 36 and 39 patients were included in p-Tm: YAG and TFL group, respectively. Groups presented similar demographics but for high blood pressure(53vs23%,p = 0,005), anatomical abnormalities(8vs33%,p = 0,03), lower pole(8vs26%,p = 0,04) and pelvic stones(25vs13%,p = 0,04) for p-Tm: YAG and TFL, respectively. The median stone maximum diameter was higher in the p-Tm: YAG group(17.3vs13.8 mm, p = 0,001) but stone volume was similar among groups(1514vs1347mm3,p = 0,6). Laser settings were similar among groups(0,6-15 Hz,10-12 W). Shorter LOT(< 0,001) and lower UAS insertion(0,01) rates were reported for TFL compared to p-Tm: YAG. The median J/mm3 was similar(14vs17,p = 0,2) but p-Tm: YAG presented higher ablation speed(0,91vs0,73mm3/s, p = 0,04). SFR were similar among groups(75vs77%,p = 0,8) but ZFR was higher in TFL group(39vs64%,p = 0,008). No difference in complications was reported. Both p-Tm: YAG and TFL are safe and effective for ELL during fURS. SFR were similar between TFL and p-Tm: YAG but the latter presented lower ZFR, traducing its lower ability to dust. Using 200 μm laser fibers with p-Tm: YAG could nuance these findings.

In Vitro Comparison of Pulsed-Thulium:YAG, Holmium:YAG, and Thulium Fiber Laser

Objective: To characterize the pulse characteristics and risk of fiber fracture (ROF) of the pulsed-Thulium:YAG (p-Tm:YAG) laser and to compare its ablation volumes (AVs) against Holmium:Yttrium-Aluminium-Garnet (Ho:YAG) laser and Thulium fiber laser (TFL). Materials and Methods: p-Tm:YAG (100 W-Thulio, Dornier-Medtech©, Germany) was characterized using single-use 272 μm core-diameter-fibers. p-Tm:YAG characterization included pulse shape, duration, and peak power (PP) studies. ROF was assessed after 5 minutes of continuous laser activation (CLA) at five decreasing fiber bend radii (1, 0.9, 0.75, 0.6, and 0.45 cm). p-Tm:YAG, Ho:YAG (120 W-Cyber-Ho, Quanta®, USA), and TFL (60 W-TFLDrive, Coloplast®, Denmark) AVs were compared using a 20-mm linear CLA at 2 mm/second velocity in contact with 20 mm3 hard stone phantoms (HSP) and soft stone phantoms (SSP) (15:3 and 15:5 water to powder ratio, respectively) fully submerged in saline at 0.5 J-20 Hz or 1 J-10 Hz. After CLA, phantoms underwent three-dimensional (3D) micro-scanning (CT) and subsequent 3D segmentation to estimate the AVs, using 3DSlicer©. Each experiment was performed in triplicate. Results: p-Tm:YAG presents a uniform pulse profile in all of the available preset modes. PP ranged from 564 to 2199 W depending on pulse mode. No laser fiber fracture occurred at any bend radius. p-Tm:YAG achieved similar mean AVs to TFL and Ho:YAG for HSP (8.96 ± 3.1 vs 9.78 ± 1.1 vs 8.8 ± 2.8 mm3, p = 0.67) but TFL was associated with higher AVs compared with p-Tm:YAG and Ho:YAG (12.86 ± 1.85 vs 10.12 ± 1.89 vs 7.56 ± 2.21 mm3, p = 0.002) against SSP. AVs for HSP increased with pulse energy for p-Tm:YAG and Ho:YAG and (11.56 ± 1.8 vs 6.36 ± 0.84 mm3 and 11.27 ± 1.98 vs 6.34 ± 0.55 mm3, p = 0.03 and p = 0.02), whereas AVs for SSP were similar across laser settings for all laser sources. AVs with TFL were similar across laser settings for both phantom types. Conclusion: p-Tm:YAG combines intermediate PP between Ho:YAG and TFL, a uniform pulse profile, no ROF with increasing deflection and effective ablation rates. Further clinical studies are needed to confirm these in vitro results.

What is the definition of stone dust and how does it compare with clinically insignificant residual fragments? A comprehensive review

PURPOSE

During endoscopic stone surgery, Holmium:YAG (Ho:YAG) and Thulium Fiber Laser (TFL) technologies allow to pulverize urinary stones into fine particles, ie DUST. Yet, currently there is no consensus on the exact definition of DUST. This review aimed to define stone DUST and Clinically Insignificant Residual Fragments (CIRF).

METHODS

Embase, MEDLINE (PubMed) and Cochrane databases were searched for both in vitro and in vivo articles relating to DUST and CIRF definitions, in November 2023, using keyword combinations: "dust", "stones", "urinary calculi", "urolithiasis", "residual fragments", "dusting", "fragments", "lasers" and "clinical insignificant residual fragments".

RESULTS

DUST relates to the fine pulverization of urinary stones, defined in vitro as particles spontaneously floating with a sedimentation duration ≥ 2 sec and suited for aspiration through a 3.6Fr-working channel (WC) of a flexible ureteroscope (FURS). Generally, an upper size limit of 250 µm seems to agree with the definition of DUST. Ho:YAG with and without "Moses Technology", TFL and the recent pulsed-Thulium:YAG (pTm:YAG) can produce DUST, but no perioperative technology can currently measure DUST size. The TFL and pTm:YAG achieve better dusting compared to Ho:YAG. CIRF relates to residual fragments (RF) that are not associated with imminent stone-related events: loin pain, acute renal colic, medical or interventional retreatment. CIRF size definition has decreased from older studies based on Shock Wave Lithotripsy (SWL) (≤ 4 mm) to more recent studies based on FURS (≤ 2 mm) and Percutaneous Nephrolithotomy(PCNL) (≤ 4 mm). RF ≤ 2 mm are associated with lower stone recurrence, regrowth and clinical events rates. While CIRF should be evaluated postoperatively using Non-Contrast Computed Tomography(NCCT), there is no consensus on the best diagnostic modality to assess the presence and quantity of DUST.

CONCLUSION

DUST and CIRF refer to independent entities. DUST is defined in vitro by a stone particle size criteria of 250 µm, translating clinically as particles able to be fully aspirated through a 3.6Fr-WC without blockage. CIRF relates to ≤ 2 RF on postoperative NCCT.

Advances in lasers for the minimally invasive treatment of upper and lower urinary tract conditions: a systematic review

PURPOSE

Technological advancements in laser lithotripsy are expanding into numerous fields of urology, like ureteroscopy (URS), percutaneous nephrolithotomy (PCNL), and benign and malignant soft-tissue treatments. Since the amount of research regarding lasers in urology has grown exponentially, we present a systematic review of the most recent and relevant advances encompassing all lasers used in urological endoscopic treatment.

METHODS

We performed a literature search using PubMed (May 2023) to obtain information about lasers for urological purposes. We included only recent data from published articles between 2021 and 2023 or articles ahead of print.

RESULTS

Lasers are widely used in lithotripsy for ureteric, renal, and bladder stones, benign prostate surgery, and bladder and upper tract tumor ablation. While the holmium (Ho:YAG) laser is still predominant, there seems to be more emphasis on pulse modulation and newer lasers such as thulium fiber laser (TFL) and pulsed Tm:YAG laser.

CONCLUSION

The use of lasers and related technological innovations have shown increasing versatility, and over time have proven to be invaluable in the management of stone lithotripsy, treatment of benign and malignant prostate diseases, and urothelial tumors. Laser endoscopic treatment is heavily based on technological nuances, and it is essential to know at least the basics of these technologies. Ultimately the choice of laser used depends on its availability, cost, surgeon experience and expertise.

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.