Temperature changes during laser lithotripsy with Ho:YAG laser and novel Tm-fiber laser: a comparative in-vitro study

Expanding urolithiasis treatment: comparison of super pulsed thulium laser and holmium:YAG laser for ureteral stone management

OBJECTIVES

The purpose of this review is to compare the effectiveness of SuperPulsed thulium fiber laser (SP TFL) and holmium:yttrium-aluminum-garnet (Ho:YAG) laser in lithotripsy, with the aim of evaluating the differences between the two in key indicators, such as lithotripsy efficiency and safety, and providing reference for clinical selection of better lithotripsy methods.

METHODS

By searching multiple authoritative medical databases (PubMed, Embase, and Web of Science databases) and including the results of relevant clinical studies and laboratory studies, the indexes involving SP TFL and Ho:YAG lasers in the included literature were analyzed.

RESULTS

We found a total of 24 relevant pieces of literature. The laser parameters, such as ablation efficiency, ablation speed, operative time, dust quality, retropulsion, visibility, temperature safety, and stone-free rate, were compared between laboratory studies and clinical outcomes. Preclinical studies have shown that SP TFL has a higher rate of stone ablation, a weaker retropulsion and a lower risk of fiber breakage. The results of clinical studies showed that the two methods were comparable in the ablation rate, laser time and operative time, stone-free rate and complication. SP TFL offered better endoscopic view quality and less retropulsion.

CONCLUSIONS

While the Ho:YAG laser remains the primary choice for endoscopic laser lithotripsy, the emergence of SP TFL offers a promising new option for the minimally invasive treatment of urinary calculi. Parameter range, retropulsion effect, laser fiber adaptability, and overall system performance demand comprehensive attention. SP TFL has a relatively short clinical application history, and further research is necessary to fully explore its long-term advantages, clinical significance, and possible limitations.

Concomitant catheter drainage alleviates the thermal effect of holmium lasers during ureteroscopic lithotripsy: a retrospective cohort study

BACKGROUND

Thermal control is pivotal for preventing ureter thermal injury during laser lithotripsy; however, patient-based studies have rarely addressed this topic. In recent years, we have employed a ureter catheter for irrigation drainage and measured temperature changes during lithotripsy. The aim of this study was to evaluate the thermal control effect of this strategy in ureteroscopic holmium laser lithotripsy.

METHODS

From September 2022 to June 2024, patients who underwent ureteroscopic holmium laser lithotripsy at our centre were included in this retrospective cohort study. Patients were divided into a drainage group and a conventional group depending on whether a ureter catheter was used for concomitant drainage during lithotripsy. The temperature was measured using a K-type thermocouple thermometer. Lithotripsy was performed at an irrigation pressure setting of 30 mmHg and a laser setting of 1.0 J × 20 Hz. Intraoperative and follow-up data were compared between the groups.

RESULTS

Sixty-seven patients were included, including 32 in the drainage group and 35 in the conventional group. lgCEM43 and the peak temperature of irrigation were significantly lower in the drainage group. The longest continuous lasing time was longer and the operation time was shorter than those in the drainage group. Compared with that in the conventional group, the quality of endoscopic vision in the drainage group during lithotripsy was significantly improved. There was no significant difference in the post-ureteroscopic lesion scale score or the 1-month stone-free rate between the groups. At the 6-month follow-up, no postoperative ureter stricture was observed in either group.

CONCLUSIONS

The current thermal control strategy is safe and feasible; it significantly reduces the intraoperative irrigation temperature and improves endoscopic vision in ureteroscopic laser lithotripsy.

Evaluating safe irrigation rates for Tm fiber laser lithotripsy to prevent thermal injury: an in vitro and numerical simulation

PURPOSE

To evaluate temperature changes and thermal injury during thulium fiber laser (TFL) lithotripsy in the urinary tract and identify the safe irrigation rate, providing a reference for optimal parameter settings in clinical practice.

METHODS

An in vitro thermal injury experiment was conducted using a home-made TFL operating at 40 W. The experiment utilized a glass tube simulating the urinary tract. A peristaltic pump circulated 25 °C saline at irrigation rates ranging from 10 to 40 mL/min. Real-time temperature measurements were recorded using thermocouples, and thermal injury was assessed by calculating the thermal dose threshold. Additionally, a validated numerical simulation model was developed to analyze temperature distributions and predict safe irrigation rates at 20 and 30 W.

RESULTS

In the in vitro experiment, at 40 W, severe thermal injury occurred in the urinary tract when the irrigation rate was below 30 mL/min, particularly in the ureter and renal calyx. The numerical simulation model demonstrated a high degree of consistency with the experimental results. According to the simulation, at 30 W, thermal injury occurred in the renal calyx when the irrigation rate was below 20 mL/min. At 20 W, thermal injury was observed in the renal calyx when the irrigation rate was below 10 mL/min.

CONCLUSIONS

The increase in temperature and the extent of thermal injury were strongly dependent on laser power and irrigation rate, with a lesser dependence on anatomical location. The accuracy of the numerical simulation was validated through experiments, demonstrating its capability to reliably predict temperature variations and thermal injury under different laser power settings and irrigation rates.

Prospective evaluation of efficacy, safety, cumulative laser energy, and stone-free rates in the post-market SOLTIVE™ SuperPulsed laser system registry: insights from team of worldwide endourological researchers' (T.O.W.E.R.) research consortium

The Thulium fiber laser (TFL) is a relatively new tool for endoscopic laser lithotripsy. The Endourological Society's T.O.W.E.R. registry sought to evaluate the stone-free rate (SFR) at 3 months following URS. A subset of the study sought to determine the association between cumulative TFL energy and SFRs. 423 patients with planned ureteroscopic lithotripsy using TFL (SOLTIVE™, Gyrus ACMI, Inc. d/b/a Olympus Surgical Technologies America) were prospectively enrolled between December 2020 and May 2023 at nine international sites. Baseline clinical characteristics and SFR data for kidney and ureteral stones were separately analyzed according to quartile cumulative TFL energy ranges. Median patient age was 58.0 (IQR: 44-67) years and maximal stone diameters were 9.9 (IQR: 7-12.9) mm and 7.4 (IQR 6.1-9.4) mm for kidney and ureteral stones, respectively. Overall SFR (no fragments) for renal and ureteral stones were 73.0% and 85.7% at 3-months. Cumulative energy levels were divided into quartiles and lower SFRs were observed with the highest quartile for kidney stones (p = 0.001), but not in ureteral stones. This correlated with kidney stone size as larger stones required more energy. The rate of adverse events related to the procedure was 1.9% (8/423). Higher stone burdens had lower stone free rates and required more cumulative laser energy. The TFL is effective in endoscopic lithotripsy. This post-marketing survey demonstrates that TFL is a safe and effective tool for endoscopic laser lithotripsy.

Evaluating temperature dynamics: a single-center prospective randomized pilot study of holmium versus thulium laser fiber for renal stones

BACKGROUND

We aimed to evaluate and compare the rise in the temperature for the safety of the kidney parenchyma on firing the Holmium: Yttrium Aluminium Garnet laser and the Thulium Fiber Laser during laser lithotripsy in humans.

METHOD

We included 30 pre-stented patients with renal calculi undergoing Retrograde intra-renal surgery. They were randomized into two groups - 15 patients underwent holmium laser lithotripsy and 15 patients underwent TFL laser lithotripsy. We used Philips paediatric esophageal probe to measure rise in temperature on firing holmium or TFL laser with irrigation at 10 ml/min and pressure at 100 mmHg. Different laser settings were used.

RESULT

The mean size of the calculi was 0.8 mm. The rise in temperature with holmium and TFL lasers depended on the firing time and irrigation flow, keeping power constant. On continuous firing for 10s, 20s, and 30s, the average rise in temperature went up to 28.67 °C, 29.70 °C, and 37.17 °C with holmium and with TFL it was 28.77 °C, 29.83 °C, and 37.62 °C, respectively. The difference in rise in temperature between two groups was statistically insignificant with p-values > 0.05. The maximum temperature reached with TFL was 39.4 °C with a 30s lasing time, and that with Ho: YAG was 38.9 °C.

CONCLUSIONS

The rise in temperature was almost equivalent with holmium and TFL. Hence, both Ho: YAG and TFL can be safely used in laser lithotripsy. Adequate irrigation is a must during the surgery. The continuous lasing time should be strictly restricted to less than 20s.

Factors affecting the thermal effects of lasers in lithotripsy: A literature review

Objective

The use of lasers has been an important part of urology in the treatment of stone and prostate disease. The thermal effects of lasers in lithotripsy have been a subject of debate over the years. The objective of this review was to assess the current state of knowledge available on the thermal effects of lasers in lithotripsy, as well as explore any new areas where studies are needed.

Methods

In August 2022, a keyword search on Google Scholar, PubMed, and Scopus for all papers containing the phrases "thermal effects" AND "laser" AND "lithotripsy" AND "urology" was done followed by citation jumping to other studies pertaining to the topic and 35 relevant papers were included in our study. The data from relevant papers were segregated into five groups according to the factor studied and type of study, and tables were created for a comparison of data.

Results

Temperature above the threshold of 43 °C was reached only when the power was >40 W and when there was adequate irrigation (at least 15-30 mL/min). Shorter lasing time divided by lithotripsy time or operator duty cycles less than 70% also resulted in a smaller temperature rise.

Conclusion

At least eight factors modify the thermal effects of lasers, and most importantly, the use of chilled irrigation at higher perfusion rates, lower power settings of <40 W, and with a shorter operator duty cycle will help to prevent thermal injuries from occurring. Stones impacted in the ureter or pelvi-ureteric junction further increase the probability of thermal injuries during laser firing.

Assessment of Holmium:YAG, Pulsed-Thulium:YAG and Thulium Fiber Lasers for Urinary Stone Ablation. In Vitro Study

Objective: To evaluate the ablation speed (AS), laser efficiency and direct thermal lesions during urinary stone lithotripsy with the current available laser technologies: Holmium:YAG (Ho:YAG), pulsed-Thulium:YAG (p-Tm:YAG) and thulium fiber laser (TFL) in vitro using different laser settings. Materials and Methods: Ho:YAG, p-Tm:YAG, and TFL laser system were used in an in vitro ureteral model with a volume of 125 mm3 Begostone. The following parameters were tested across all laser devices: 0.6J/10 Hz (6 W), 0.6 J/20 Hz (12 W), 1.5 J/10 Hz (15 W), and 1.5 J/20 Hz (30 W), employing short pulse width for all lasers and long pulse width for Ho:YAG and p-Tm:YAG. Ten participants conducted the experimental setup during 3-minutes laser on time, combining the laser technology, settings, and pulse widths, with a total of 20 different combinations. The efficiency, AS and ureteral damage resulting from each intervention were analyzed. Results: p-Tm:YAG and TFL demonstrated significantly higher efficiency compared with Ho:YAG (0.049 ± 0.02 Δgr/KJ and 0.042 ± 0.01 Δgr/KJ vs 0.029 ± 0.01 Δgr/KJ; p < 0.05). In all laser sources, as the power increases, the AS also increases (p < 0.05). Furthermore, only at high-energy settings (1.5 J) higher frequency led to increase AS (p < 0.05). Both, p-Tm:YAG and TFL exhibited higher AS compared to Ho:YAG (0.64 ± 0.33 Δgr/s and 0.62 ± 0.31 Δgr/s vs 0.44 ± 0.22 Δgr/s; p < 0.05). Regarding ureteral injuries, as the power increases, there is a higher chance of ureteral damage (p = 0.031). No differences were observed between laser technologies (p = 0.828). Conclusions: Both, p-Tm:YAG and TFL exhibited superior performances during laser lithotripsy compared with Ho:YAG, as they demonstrated higher efficiency and ablation speed. Thermal damage did not appear to be associated with specific laser equipment, but higher grades of lesions are described by increasing power.

Ablation efficiency and laser safety of a novel superpulsed thulium fiber laser: a in vitro study

PURPOSE

To assess the ablation efficiency of the Superpulsed Thulium Fiber Laser (SP-TFL) and investigate the thermal effects of SP-TFL.

METHODS

A SP-TFLwas employed to evaluate ablation efficiency. Fresh ex-vivo pig kidneys and ureters were utilized to evaluate the renal pelvis and ureter temperature changes, different irrigation rates(0, 15, 38mL/min) and a long pulse width were used.

RESULTS

The research indicated that as laser output power increased, ablation rates significantly increased. Ablation rates(mg/min) were higher and the energy per ablated mass(J/mg) was lower at lower frequencies(10-50 Hz). Under the same frequency and single pulse energy, super short and short pulse widths demonstrated higher ablation rates at higher frequencies (exceeding 100 Hz). The temperature of the renal pelvis and ureter decreased with increasing irrigation rates. In the renal pelvis, without irrigation, the temperature quickly reached the critical threshold of 43℃. The irrigation rate was 15 ml/min and power was no more than 18 W, the renal pelvis temperature did not reach 43℃. When the irrigation rate were 38 ml/min, the temperature did not risen to 43℃. In the ureter, without irrigation, the temperature also quickly reached 43℃. The temperature reached 43℃ when the power exceeded to12W with an irrigation rate of 15 ml/min. With an irrigation rate of 38 ml/min, the temperature reached 43℃ at a laser power of 30 W.

CONCLUSIONS

The SP-TFL demonstrated promising ablation effectiveness especially for lower frequencies and super short and short pulse widths model. Proper irrigation rates, single pulse energy, frequency and pulse width are crucial during lithotripsy.

Steady-state versus burst lasing techniques for thulium fiber laser

OBJECTIVE

To evaluate the stone ablation rate and direct thermal damage from thulium fiber laser (TFL) lithotripsy using continuous (C) and burst (B) lasing techniques on an in vitro ureteral model.

METHODS

The TFL Drive (Coloplast, Humlebaek, Denmark) was used in an in vitro saline-submerged ureteral model. Ten participants, including five junior and five experienced urologists, conducted the experimental setup with 7 different settings comparing two lasing techniques: steady-state lasing (0.5 J/10 Hz = 5W for 300 s and 0.5 J/20 Hz = 10W for 150 s) and burst, intermittent 5 s on/off lasing (0.5 J/20 Hz, 0.5 J/30 Hz, 0.5 J/60 Hz, 0.1 J/200 Hz, and 0.05 J/400 Hz) with a target cumulative energy of 1500 J using cubic 125 mm3 phantom BegoStonesTM. Ureteral damage was graded 1-3 based on the severity of burns and holes observed on the surface of the ureteral model.

RESULTS

The were no significant differences in stone ablation mass neither between C and B lasing techniques, nor between expertise levels. At C lasing technique had only mild ureteral lesions with no significant differences between expertise levels (p: 0.97) or laser settings (p: 0.71). At B lasing technique, different types of thermal lesions were found with no expertise (p: 0.11) or setting (p: 0.83) differences. However, B laser setting had higher grade direct thermal lesions than C (p: 0.048).

CONCLUSION

Regarding efficacy, C and B lasing techniques achieve comparable stone ablation rates. Safety-wise, B lasing mode showed higher grade of direct thermal lesions. These results should be further investigated to verify which of the lasing mode is the safest in vivo. Until then and unless proven otherwise, a C mode with low frequency should be recommended to avoid ureteral wall lesions.

Holmium:yttrium-aluminium-garnet laser with MOSES technology is more efficient than thulium fibre laser in supine mini-percutaneous nephrolithotomy

OBJECTIVES

To address the paucity of literature comparing outcomes achieved with utilisation of the high-power holmium:yttrium-aluminium-garnet (Ho:YAG) laser with MOSES technology vs those achieved with the thulium fibre laser (TFL) in mini-percutaneous nephrolithotomy (PCNL).

METHODS

A retrospective review was performed of patients undergoing supine mini-PCNL between August 2021 and May 2023. Exclusion criteria were urinary diversion, simultaneous utilisation of >1 laser platform, use of any other form of fragmentation, and ureteric stones. The Ho:YAG platform (Lumenis Pulse P120H™ with MOSES technology, 120W; Boston Scientific®) and the TFL (Soltive SuperPulsed Thulium Fibre [SPTF], 60W; Olympus®) were compared. Data on stone-free rate (SFR) were determined by computed tomography performed on the first postoperative day and presented as absence of stone fragments, no fragments larger than 2 mm, or no fragments larger than 4 mm.

RESULTS

A total of 100 patients met the inclusion criteria, 51 mini-PCNLs with the Ho:YAG laser and 49 with the SPTF laser. No significant differences in demographics or stone characteristics were detected between the two groups. The Ho:YAG laser utilised less energy and time, resulting in higher ablation efficiency (P < 0.05) and less total operating time (P < 0.05). Overall, there was no difference in SFR in any category between the Ho:YAG group and the SPTF group (no fragments: relative risk [RR] 0.81, 95% confidence interval [CI] 0.59-1.12, P = 0.21; fragments <2 mm: RR 0.86, 95% CI 0.67-1.10, P = 0.23; fragments <4 mm: RR 0.96, 95% CI 0.80-1.15, P = 0.67).

CONCLUSIONS

Although we observed an equivalent postoperative SFR, this study supports a shorter operating time and greater intra-operative laser efficiency with the Ho:YAG laser over the SPTF laser in mini-PCNL.

Successful treatment of staghorn stones with flexible ureteroscopy and thulium fiber laser (TFL) lithotripsy: initial experience with 32 cases

Purpose

To investigate the efficacy and safety of flexible ureteroscopy with thulium fiber laser lithotripsy for management of renal staghorn stones.

Materials and Methods

Thirty-two patients with staghorn stones were recruited. Stone characteristics including: width, length, volume and density were analyzed. Ablation speed, laser efficacy and laser activity were recorded. The primary outcome was to assess stone free rate after the procedure using spiral CT scan.

Results

The median stone volume was 7339 (3183–53838) mm3. Median operative and lasing time were 135 (70–200) and 117 (50–180) minutes, respectively. The mean total energy delivered was 63.9 ± 30 KJ with a median ablation speed of 1.3 (0.5–4.9) mm3/sec. Mean laser efficacy was 7.5 ± 3.6 Joules/mm3. A total of 12 complications occurred in 8 patients (25%). The median hospital stay was 7 (3.5–48) hours and 30 patients (93.7%) were discharged on the same day of surgery. After the first session, seventeen patients (53%) were stone free with no residual fragments while six (19%) patients had residuals £ 2 mm. Nine patients (28%) had residuals > 2 mm with median residual size of 4 (3–9) mm. A second intervention was required in 4 cases.The overall stone free rate after completion of treatment was 65.6%.

Conclusion

Flexible ureteroscopy with thulium fiber laser lithotripsy is a safe and effective treatment option for staghorn stones with stone free rate comparable to standard PCNL with advantages of minimal morbidity, minimal blood loss and shorter hospital stay.

Getting hot in here! Comparison of Holmium vs. thulium laser in an anatomic hydrogel kidney model

As laser technology has advanced, high-power lasers have become increasingly common. The Holmium: yttrium-aluminum-garnet (Ho:YAG) laser has long been accepted as the standard for laser lithotripsy. The thulium fiber laser (TFL) has recently been established as a viable option. The aim of this study is to evaluate thermal dose and temperature for the Ho:YAG laser to the TFL at four different laser settings while varying energy, frequency, operator duty cycle (ODC). Utilizing high-fidelity, 3D-printed hydrogel models of a pelvicalyceal collecting system (PCS) with a synthetic BegoStone implanted in the renal pelvis, laser lithotripsy was performed with the Ho:YAG laser or TFL. At a standard power (40W) and irrigation (17.9 ml/min), we evaluated four different laser settings with ODC variations with different time-on intervals. Temperature was measured at two separate locations. In general, the TFL yielded greater cumulative thermal doses than the Ho:YAG laser. Thermal dose and temperature were typically greater at the stone when compared away from the stone. Regarding the TFL, there was no general trend if fragmentation or dusting settings yielded greater thermal doses or temperatures. The TFL generated greater temperatures and thermal doses in general than the Ho:YAG laser with Moses technology. Temperatures and thermal doses were greater closer to the laser fiber tip. It is inconclusive as to whether fragmentation or dusting settings elicit greater thermal loads for the TFL. Energy, frequency, ODC, and laser-on time significantly impact thermal loads during ureteroscopic laser lithotripsy, independent of power.

Prospective Randomized Controlled Trial to Compare Dusting vs Fragmentation Using Thulium Fiber Laser in Retrograde Intrarenal Surgery

Objective: To compare the dusting vs fragmentation modes with thulium fiber laser (TFL) in retrograde intrarenal surgery (RIRS) for upper tract stones using the same fixed low-power settings in both the arms. The primary objective was to compare the stone-free rate (SFR) and secondary objectives were to compare mean operating times, hospital stay duration, complication rates, need for secondary procedures, and laser efficacy. Materials and Methods: A prospective randomized trial, with patients having proximal ureteral or renal stones of 10-20 mm and planned for RIRS was done at a single institute. A total of 60 consecutively admitted patients with signed consent were included for randomization with 30 patients in each arm of dusting and fragmentation modes. Results: Median age in dusting and fragmentation arms of 41.5 and 45.5 years, median stone size of 10.45 and 12.25 mm, median stone volume of 351.6 and 490.7 mm3, and median stone density of 1263.5 HU in both arms with comparable hospital stay of median of 2 days in both arms. Lasing time was significantly lesser in the fragmentation group (20.5 minutes; interquartile range [IQR] 15.12-31.62) than in the dusting group (34.25 minutes, IQR 26.62-38.62, p < 0.001). Higher ablation speed for fragmentation mode (0.405 mm3/sec, IQR 0.337-0.635) than for dusting mode (0.17 mm3/sec, IQR 0.135-0.325, p < 0.001). SFRs and complication rates were comparable in both the arms. Conclusion: TFL in fragmentation mode has shorter lasing times and better laser efficacy than dusting mode with comparable minimal complications, SFRs, and hospital stay duration. Clinical Trial Registration number: CTRI050827.

Laser safety, warnings, and limits in retrograde intrarenal surgery

OBJECTIVE

To analyze the current information about laser safety in retrograde intrarenal surgery (RIRS), focusing on the two main laser technologies that we use in urology, the holmium:yttrium-aluminum-garnet (Ho:YAG) laser, and the thulium fiber laser (TFL).

METHODS

Narrative overview of the most relevant articles published in MEDLINE and Scopus databases about this subject.

RESULTS

TFL and Ho:YAG laser at similar settings (0.2 J/40 Hz) have similar volume-averaged temperature increase and the average heating rate increase proportionally to laser power, especially when high frequencies are used. Recent preclinical data, comparing both laser technologies at different laser settings, agreed that when the delivered energy increases in expenses of higher frequencies, the thermal damage increases too. Higher frequencies, despite of the rise of temperature in the irrigation medium, can cause accidental thermal lasering lesions.

CONCLUSION

The use of low frequency settings and a proper irrigation is critical to avoid thermal injury in endoscopic laser lithotripsy. In addition, the use of laser safety eyeglasses is recommended in Ho:YAG and TFL ELL.

The heat is on: the impact of excessive temperature increments on complications of laser treatment for ureteral and renal stones

OBJECTIVE

Technological advancements in the field of urology have led to a paradigm shift in the management of urolithiasis towards minimally invasive endourological interventions, namely ureteroscopy and percutaneous nephrolithotomy. However, concerns regarding the potential for thermal injury during laser lithotripsy have arisen, as studies have indicated that the threshold for cellular thermal injury (43 °C) can be exceeded, even with conventional low-power laser settings. This review aims to identify the factors that contribute to temperature increments during laser treatment using current laser systems and evaluate their impact on patient outcomes.

MATERIALS AND METHODS

To select studies for inclusion, a search was performed on online databases including PubMed and Google Scholar. Keywords such as 'temperature' or 'heat' were combined with 'lithotripsy', 'nephrolithotomy', 'ureteroscopy', or 'retrograde intrarenal surgery', both individually and in various combinations.

RESULTS

Various strategies have been proposed to mitigate temperature rise, such as reducing laser energy or frequency, shortening the duration of laser activation, increasing the irrigation fluid flow rate, and using room temperature or chilled water for irrigation. It is important to note that higher irrigation fluid flow rates should be approached cautiously due to potential increases in intrarenal pressure and associated infectious complications. The utilization of a ureteral access sheath (UAS) may offer benefits by facilitating irrigation fluid outflow, thereby reducing intrapelvic pressure and intrarenal fluid temperature.

CONCLUSION

Achieving a balance between laser power, duration of laser activation, and irrigation fluid rate and temperature appears to be crucial for urologists to minimize excessive temperature rise.

Super pulsed thulium fiber laser outcomes in retrograde intrarenal surgery for ureteral and renal stones: a systematic review and meta-analysis

BACKGROUND

Laser lithotripsy using a thulium fiber laser (TFL) has become an effective treatment option for small renal stones with low complication rates. TFL has a higher absorption coefficient, smaller fibers, and better pulse rate capability.

METHODS

We conducted a systematic review and meta-analysis to evaluate the published evidence regarding TFL's lithotripsy performance in retrograde intrarenal surgery (RIRS), for which we primarily assessed the outcomes of stone-free rate, operation time, and complications. We searched different databases from inception to April 2023. We assessed the methodological quality and risk of bias using the Cochrane Risk of Bias tool for randomized trials and the ROBINS-I tool for non-randomized studies. We used a random-effects model for meta-analysis and assessed heterogeneity using the I2 statistic.

RESULTS

Twelve published studies evaluated the efficacy of RIRS using a TFL for treating renal and ureteral stones. The meta-analysis revealed a predicted stone-free rate of 89.37% (95% CI: 83.93% to 93.12%), indicating that, on average, approximately 89.37% of patients achieved a stone-free state after treatment. The substantial heterogeneity among the studies was evident, as shown by a Q-value of 33.1174 and a p-value of 0.0003. The I2 value of 69.80% (95% CI: 25.91% to 92.02%) highlighted the proportion of variability attributed to genuine heterogeneity across the studies. Moreover, the H2 value 3.31 (95% CI: 1.35 to 12.53) indicated significant heterogeneity beyond random chance. The estimated overall effect size (logit-transformed) of 2.1289 was highly statistically significant (z = 8.7648, p < 0.0001) with a confidence interval of 1.6528 to 2.6049. The reported complications varied across studies, encompassing Clavien grade I-II complications in most cases, with a subset experiencing more severe Clavien grade III-V complications. Additionally, other studies noted a range of complications, such as haematuria, fever, transient creatinine elevation, and postoperative issues like bleeding, pain, and sepsis.

CONCLUSION

This meta-analysis suggests that RIRS using TFL is an effective and safe treatment option for renal and ureteral stones, with high stone-free and low complication rates. The included studies exhibited a low risk of bias and were of high quality. However, more extensive randomized controlled trials with extended follow-up periods are needed to investigate this technique's efficacy and safety.

Ablation rates with Holmium:YAG and Thulium Fiber Laser: Influence of the stone phantom homogeneity. An in vitro study

OBJECTIVES

The lithotripsy efficiency (LE) in vitro study requires artificial or human stone samples (AS, HS). With the development of dusting lithotripsy, less ex vivo HS are available. We aimed to compare Thulium Fiber Laser (TFL) and Holmium:YAG (Ho:YAG)'s LE and define the most accurate LE parameter.

METHODS

Hard and soft homogenous- and heterogenous-AS (Ho-AS, He-AS) were made to reproduce calcium-oxalate monohydrate and uric acid stones, respectively by a rapid or slow brewing of BegostonePlus (Bego) and distilled water. One hundred and fifty and 272μm-laser fibers, connected to 50W-TFL and 30W-HoYAG generators, compared three settings for TFL (FD: 0.15J/100Hz; D: 0.5J/30Hz; Fr: 1J/15Hz) and two for Ho:YAG (D-Fr). An experimental setup consisted in immerged 10mm cubic stone phantoms with a 20 seconds' lasing spiral, in contact mode, repeated four times. Stones were dried, weighted and μ-scanned (ablation weight and volume [AW and AV]).

RESULTS

With He-AS, dusting AV were four- and three-fold higher with TFL compared to Ho:YAG against hard and soft (P<0.05). In fragmentation, AV were two-fold higher with TFL compared to Ho:YAG against hard (P<0.05) and soft (P<0.05). Experiments with Ho-AS were associated with non-significant differences when comparing TFL-150μm and TFL-272μm. The ablation weight-volume correlation coefficients was higher with Ho-AS than with He-AS (P<0.0001), and with hard than soft AS. If the LE can be estimated by the AW with hard AS, this approximation is not consistent for soft AS.

CONCLUSION

TFL presented higher ablation rates than Ho:YAG, significant with He-AS. If the AW is acceptable and less expensive for hard Ho-AS, AV are more accurate for He-AS, which are suggested to imitate closely HS.

Temperature changes of renal calyx during high-power flexible ureteroscopic Moses holmium laser lithotripsy: a case analysis study

PURPOSE

The risk of thermal damage increases with the introduction of high-power lasers during holmium laser lithotripsy. This study aimed to quantitatively evaluate the temperature change of renal calyx in the human body and the 3D printed model during high-power flexible ureteroscopic holmium laser lithotripsy and map out the temperature curve.

METHODS

The temperature was continuously measured by a medical temperature sensor secured to a flexible ureteroscope. Between December 2021 and December 2022, willing patients with kidney stones undergoing flexible ureteroscopic holmium laser lithotripsy were enrolled. High frequency and high-power settings (24 W, 80 Hz/0.3 J and 32 W, 80 Hz/0.4 J) were performed for each patient with room temperature (25 °C) irrigation. In the 3D printed model, we studied more holmium laser settings (24 W, 80 Hz/0.3 J, 32 W, 80 Hz/0.4 J and 40 W, 80 Hz/0.4 J) with warmed (37 °C) and room temperature (25 °C) irrigation.

RESULTS

Twenty-two patients were enrolled in our study. With 30 ml/min or 60 ml/min irrigation, the local temperature of the renal calyx did not reach 43 °C in any patient under 25 °C irrigation after 60 s laser activation. There were similar temperature changes in the 3D printed model with the human body under the irrigation of 25 °C. Under the irrigation of 37 °C, the temperature rise slowed down, but the temperature in the renal calyces was close to or even exceeded the 43 °C at the setting of 32 W, 30 ml/min and 40 W, 30 ml/min after continuing laser activation.

CONCLUSION

In the irrigation of 60 ml/min, the temperature in the renal calyces can still be maintained within a safe range after continuous activation of a holmium laser up to 40 W. However, continuous activation of 32 W or higher power holmium laser in the renal calyces for more than 60 s in the limited irrigation of 30 ml/min can cause excessive local temperature, in such situation room temperature perfusion at 25 ℃ may be a relatively safer option.

Thulium fibre laser vs holmium: yttrium-aluminium-garnet laser lithotripsy for urolithiasis: meta-analysis of clinical studies

OBJECTIVE

To compare and assess the clinical outcomes between thulium fibre laser (TFL) and holmium: yttrium-aluminium-garnet (Ho:YAG) laser endoscopic lithotripsy of urolithiasis through a meta-analysis of comparative clinical studies.

METHODS

A systematic literature search was performed in May 2022, grey literature search in July 2022. Comparative clinical studies were evaluated according to Cochrane recommendations. Assessed outcomes include the stone-free rate (SFR), complication rate, operative time (OT), laser utilisation time (LUT), ablation rate (stone volume/laser time), ablation efficiency (energy use/stone volume), total energy usage, degree of retropulsion, and hospital stay. Risk ratios (RRs) and standardised mean differences (SMDs) were extrapolated. Subgroup analyses, heterogeneity, publication bias, and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) assessment were performed. International Prospective Register of Systematic Reviews (PROSPERO) registration: CRD42022300788.

RESULTS

A total of 15 studies with 1698 cases were included in this review. The outcome of SFR showed no significant between-group difference (RR 1.09, 95% confidence interval [CI] 0.99-1.20). However, subgroup analysis of TFL vs Ho:YAG with no pulse modulation showed a SFR favouring TFL (RR 1.11, 95% CI 1.01-1.23). The composite postoperative complication rate was comparable between the two intervention groups (RR 0.97, 95% CI 0.66-1.43). OT, LUT and ablation rate were significantly better for TFL than Ho:YAG (SMD -1.19, 95% CI -1.85 to -0.52; SMD -1.67, 95% CI -2.62 to -0.72; SMD 0.59, 95% CI 0.15-1.03; respectively). The degree of retropulsion was significantly lower for TFL than Ho:YAG without pulse modulation (SMD -1.23, 95% CI -1.74 to -0.71). Ablation efficiency, total energy usage, and hospital stay were all comparable. Based on GRADE criteria, the evidence certainty was determined to be very low.

CONCLUSION

Overall, there was no between-group difference for the SFR. However, compared to Ho:YAG with no pulse modulation, TFL rendered a better SFR. Shorter OT and LUT, a lesser degree of retropulsion, and a better ablation rate were noted in favour of the TFL. There was no overall between-group difference for composite postoperative complication rate, ablation efficiency, total energy usage, and hospital stay. Currently, the available clinical evidence was assessed to be of very low certainty.

Thulium fiber laser in endourology: current clinical evidence

PURPOSE OF REVIEW

To review and summarize preclinical and clinical data on thulium fiber laser's (TFL) effectiveness (ablation rate, stone-free rate etc.) and safety in terms of laser injuries and thermal damage. This enables us to assess how the in-vitro evidence translates into the clinical real-life scenario.

RECENT FINDINGS

In this analysis, a total of 21 preclinical trials have been included. Most of the trials use conventional Holmium:YAG laser as a comparator, with only a few assessing lasers with pulse modulation. Most of the trials focus on the superior ablation rate and superior dusting features of TFL, as well as comparison of retropulsion (both in conventional Ho:YAG and in a pulse modulation), with a few studies assessing safety aspects. A total of 13 trials assessed TFL, clinically, in percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS). The clinical data obtained suggest that lithotripsy by TFL is safe, facilitates effective stone fragmentation, and results in a reduction of retropulsion. Unfortunately, most of the clinical trials lack a direct comparator, and so no clear-cut comparisons are possible.

SUMMARY

During in-vitro studies, TFL demonstrated to be a new energy source with a great potential for improved ablation, lower retropulsion and improved dusting. These claims are supported in contemporary clinical studies, reporting superior ablation and negligible retropulsion in both PCNL and RIRS. However, it should be noted that the data regarding clinical results compared with conventional Ho:YAG is still limited.

Temperature change during laser upper-tract endourological procedures: current evidence and future perspective

PURPOSE OF REVIEW

To examine the most recent data on temperatures produced during laser lithotripsy and to provide several strategies for maintaining lower values and reducing the risk of complications during endourological treatment.

RECENT FINDINGS

Endourologists have access to a wide range of alternatives with the help of the holmium: yttrium-aluminum-garnet (Ho:YAG), thulium: yttrium-aluminum-garnet (TM:YAG), and thulium fiber laser (TFL) that compose a robust and adaptable laser lithotripsy armamentarium. Nevertheless, the threat of thermal damage increases as the local temperature rises with high total power. Most endourologists are not familiar with normal and pathological temperature ranges, how elevated temperatures affect perioperative problems, or how to avoid them.

SUMMARY

Increased temperatures experienced during laser lithotripsy may affect the course of the healing process. All lasers display a safe temperature profile at energies below 40 W. At equal power settings, Ho:YAG, Tm:YAG, and TFL lasers change the temperature comparably. Shorter on/off laser activation intervals, chilled irrigation, open irrigation systems, and UASs all aid in maintaining acceptable temperatures.

Understanding the ablation rate of Holmium:YAG and thulium fiber lasers. Perspectives from an in vitro study

This study sought to analyze the ablation rates of Holmium:YAG (Ho:YAG) and thulium fiber laser (TFL) under different settings combinations. Lasering was carried out by a computed spiral pattern through a stepper motor bearing a laser fiber. BegoStones were placed inside a water container and lasered therein and the ablation rate was calculated. Different combinations were tested for ~12 Watts (W) for Ho:YAG and TFL lasers. Further 25 W combination for TFL were conducted testing higher frequencies. One-hundred-one experiments were conducted. Under ~12 W, the highest ablation rate for Ho:YAG was obtained with 40 Hz/0.3 J, and Virtual Basket™ (VB) emission mode [114.35 (88.30 - 126.40) mg/min] whereas for TFL, using 40 Hz/0.3 J, and long pulse [143.40 (137.40 - 146) mg/min]. A matched-comparison for 12 Hz/1 J settings showed that TFL outperformed Ho:YAG using medium pulse [63.30 (55.30 - 81.30) vs 132.00 (115.70 - 228.60) mg/min, p=0.016] and long pulse [62.90 (51.60 - 78.90) vs 134.70 (110.60 - 149.30) mg/min, p=0.016]. In the 40 Hz/0.3 J settings, TFL outperformed Ho:YAG (p=0.034). Nonetheless, Ho:YAG with VB's ablation rate increased [114.35 (88.30 - 126.40)], being comparable to that of TFL with medium pulse [127.5 (88.90 - 141.70)] (p=0.400). In TFL 25 W experiments, the ablation rate of 500 Hz / 0.05 J, was higher than those of 1000 Hz / 0.025 J (p=0.049). TFL ablation rate is higher than that of Ho:YAG. Moreover, the Virtual Basket™ emission mode, increased Ho:YAG ablation rates, resulting reaching similar to that of TFL in certain modalities.

Tissue thermal effect during lithotripsy and tissue ablation in endourology: a systematic review of experimental studies comparing Holmium and Thulium lasers

PURPOSE

We looked into the Thulium: yttrium-aluminum-garnet (TM:YAG), Thulium Fibre laser (TFL) and Holmium: yttrium-aluminum-garnet (Ho:YAG) thermal laser tissue effect during lithotripsy and tissue ablation.

METHODS

We performed a PubMed, Scopus, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) search.

RESULTS

During lithotripsy, the Ho:YAG generated temperatures from 24 to 68.7 °C at powers < 20 W, the Tm:YAG from 43.7 °C at 30 W to 68 °C at powers < 20 W, and the TFL from 33 to 40.46 °C. During ablation, the Ho:YAG and continuous wave (cw) Tm:YAG tissue incision depths ranged from 0.08 to 2.26 mm, and from 0.28 to 3.22 mm. The Ho:YAG and Tm:YAG vaporization areas ranged from 0.044 to 0.078 mm² and from 0.050 to 0.078 mm³ and their coagulation zones were 0.075 mm² and 0.125 mm³ respectively. Ho:YAG and Tm:YAG laser damage zones ranged from 0.093 to 2.6 mm³ and from 0.207 to 0.98 mm³ respectively. The TFL incision depth ranged from 0.04 to 5.7 mm. The cw and SuperPulsed (SP) vaporization volumes ranged from 8 to 28.2 mm³/s and from 4 to 11 mm³/s. TFL coagulation depth and coagulation zone ranged from zero to 1.1 mm, 2.2 to 5.1 mm³ in SP mode and from 7.7 to 18.1 mm³ in cw mode.

CONCLUSION

During lithotripsy all lasers caused similar temperature changes and had a safe temperature profile at < 40 W. During tissue ablation, Ho:YAG has a deeper incision depth, while cwTm:YAG and cwTFL have broader coagulation and total laser areas.

Laser Efficiency and Laser Safety: Holmium YAG vs. Thulium Fiber Laser

(1) Objective: To support the efficacy and safety of a range of thulium fiber laser (TFL) pre-set parameters for laser lithotripsy: the efficiency is compared against the Holmium:YAG (Ho:YAG) laser in the hands of juniors and experienced urologists using an in vitro ureteral model; the ureteral damage of both lasers is evaluated in an in vivo porcine model. (2) Materials and Methods: Ho:YAG laser technology and TFL technology, with a 200 µm core-diameter laser fibers in an in vitro saline ureteral model were used. Each participant performed 12 laser sessions. Each session included a 3-min lasering of stone phantoms (Begostone) with each laser technology in six different pre-settings retained from the Coloplast TFL Drive user interface pre-settings, for stone dusting: 0.5 J/10 Hz, 0.5 J/20 Hz, 0.7 J/10 Hz, 0.7 J/20 Hz, 1 J/12 Hz and 1 J/20 Hz. Both lasers were also used in three in vivo porcine models, lasering up to 20 W and 12 W in the renal pelvis and the ureter, respectively. Temperature was continuously recorded. After 3 weeks, a second look was done to verify the integrity of the ureters and kidney and an anatomopathological analysis was performed. (3) Results: Regarding laser lithotripsy efficiency, after 3 min of continuous lasering, the overall ablation rate (AR) percentage was 27% greater with the TFL technology (p < 0.0001). The energy per ablated mass [J/mg] was 24% lower when using the TFL (p < 0.0001). While junior urologists performed worse than seniors in all tests, they performed better when using the TFL than Ho:YAG technology (36% more AR and 36% fewer J/mg). In the in vivo porcine model, no urothelial damage was observed for both laser technologies, neither endoscopically during lasering, three weeks later, nor in the pathological test. (4) Conclusions: By using Coloplast TFL Drive GUI pre-set, TFL lithotripsy efficiency is higher than Ho:YAG laser, even in unexperienced hands. Concerning urothelial damage, both laser technologies with low power present no lesions.

Thermal Injury and Laser Efficiency with Holmium YAG and Thulium Fiber Laser-An In Vitro Study

Objective: To evaluate using an inanimate model the thermal injury and laser efficiency on high frequency, high energy, and its combination in hands of junior and experienced urologists during holmium YAG (Ho:YAG) and Thulium fiber laser (TFL) lithotripsy. Methods: A Cyber: Ho 150 WTM and Fiber Dust TFL (Quanta System) with 200 μm core-diameter laser fibers (LF) were used in a saline in vitro ureteral model. Each participant (five junior and five experienced urologists) performed 32 sessions of 5-minute lasering (125 mm³ phantom BegoStones™), comparing four modes (3 J/5 Hz [1.5 W], 0.3 J/20 Hz [6 W], 1.2 J/5 Hz [6 W], and 1.2 J/20 Hz [24 W]). Transparent tip and cleaved LF, and digital and fiberoptic ureteroscopes were also compared. Ureteral damage was classified in a scale (0-5) according to the burns and holes seen in the ureteral model's surface. Results: High-power (HP) setting (24 W) was associated with higher delivered energy and higher ablation rates (ARs) in both lasers (p < 0.001). For the same power setting (6 W), there was no difference in delivered energy or stone ARs. Regardless the settings, a higher AR was observed with TFL than with Ho:YAG (0.5Δ mg/s ± 0.33 vs 0.39 Δmg/s ± 0.31, p = 0.002) laser. Higher mean AR was found with cleaved tip vs transparent tip (p = 0.03) in TFL. For both lasers, higher ureteral damage was observed in the 24 W group (p = 0.006) and in the junior urologists (p = 0.03). Between 6 W groups, different types of lesions were found and junior urologist have more lesions when high frequency was used, for both Ho:YAG (p = 0.05) and TFL (p = 0.04). Conclusion: More stone ARs and reduced operative time are observed in HP settings; however, more ureteral thermic-related damage is produced. When comparing the same power, higher energy or frequency does not modify the AR. Nonetheless, more ureteral thermic-related thermal damage is observed in high-frequency settings in unexperienced hands.

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.

Thulium Fiber Laser Behavior on Tissue During Upper- and Lower-Tract Endourology

PURPOSE OF REVIEW

To present the latest evidence on thulium fiber laser (TFL) effects on tissue, during lithotripsy and ablation, emphasizing on generated temperatures, thermal damage thresholds, incision depths, areas of coagulation, and laser damage.

RECENT FINDINGS

Lasers are frequently utilized during endoscopic treatment of different urological conditions. The holmium:yttrium-aluminum-garnet (Ho:YAG) is most frequently used for various types of stones and soft tissue. The TFL has been recently introduced, offering several advantages. However, its activity on tissue during upper and lower tract endourology is poorly understood. At equivalent power settings, TFL and Ho:YAG generate similar temperature changes during lithotripsy. TFL has a shallow incision depth during tissue ablation. Compared to SP TFL, (cw) TFL results in a broader coagulation zone, whereas SP TFL gives of Ho:YAG-similar incision, and (cw) TFL offers a quick, precise cut with more carbonization.

Mini-track, mini-nephroscopy, mini-ultrasonic probe percutaneous nephrolithotomy and its initial clinical application

Background

To assess the outcome of the mini-track, mini-nephroscopy, mini ultrasonic probe percutaneous nephrolithotomy for upper ureteral and kidney stones.

Methods

We collected data of 53 patients (55 kidney units) who underwent mini-track, mini-nephroscopy, mini-ultrasonic probe percutaneous nephrolithotomy between September 2020 and March 2021. The study included single and upper ureteral stones from 12 kidneys, multiple stones from 28 kidneys, and staghorn stones from 15 kidneys.

Results

The mean operative duration was 50.6 min, ranging from 15 to 200 min, whereas the mean lithotripsy and stone removal time was 17.2 min (3–45 min). Moreover, the mean postoperative length of stay was 4.0 days (1–7 days). Besides, the stone-free rate (SFR) of discharge was 89.1% (49/55). The mean hemoglobin drop was 15.3 mg/dL, ranging 1–32 mg/dL. Out of the total cases, only 4 of them displayed minor complications. The outcomes of < 40 mm versus ≥ 40 mm calculi were compared by performing subgroup analysis. The results demonstrated a longer operation duration (65.2 vs. 40.2 min), higher complication rate (13.0% vs. 3.3%), and lower SFR in the ≥ 40 mm calculi subgroup.

Conclusions

In summary, mini-track, mini-nephroscopy, mini-ultrasonic probe percutaneous nephrolithotomy is an effective and safe method to treat patients with upper ureteral and kidney calculi. This is especially significant for the stone size of 20–40 mm, demonstrating excellent SFR and a lower complication rate.

Determination of Irrigation Flowrate During Flexible Ureteroscopy: Methods for Calculation Using Renal Pelvis Pressure

BACKGROUND

Proper control of irrigation flowrate during ureteroscopy is important to manage thermal and pressure risks. This task is challenging because flowrate is not directly measured by commercially available ureteroscopic or fluid management systems. However, flowrate can be calculated using a hydrodynamic relationship based on measurable values during ureteroscopy. Objectives of this in vitro study were to 1) calculate inflow resistance for different working channel conditions and then using these values 2) calculate irrigation flowrate and determine its accuracy across a range of renal pelvis pressures.

MATERIALS AND METHODS

A 16 Liter container was filled with deionized water and connected by irrigation tubing to a 9.6Fr single-use ureteroscope. Inflow resistance was determined by plotting flowrate (mass of fluid collected from ureteroscope tip in 60 seconds) versus irrigation pressure (range 0-200 cmH2O). Next, the tip of the ureteroscope was inserted into the renal pelvis of a silicone kidney-ureter model and renal pelvis pressure was measured. In conjunction with the previously determined inflow resistance and known irrigation pressure values, flowrate was calculated and compared to experimentally measured values. All trials were performed in triplicate for working channel conditions: empty, 200µm laser fiber, 365µm laser fiber, and 1.9Fr stone basket.

RESULTS

Flowrate was linearly dependent on irrigation pressure for each working channel condition. Inflow resistance was determined to be 5.0 cmH2O/(ml/min) with the 200µm laser fiber in the working channel and calculated flowrates were within 1 ml/min of measured flowrates. Similar results were seen with a 365µm laser fiber, and 1.9Fr basket.

CONCLUSIONS

Utilizing renal pelvis pressure measurements, flowrate was accurately calculated across a range of working channel conditions and irrigation pressures. Incorporation of this methodology into future ureteroscopic systems that measure intrarenal pressure, could provide a real-time readout of flowrate for the urologist and thereby enhance safety and efficiency of laser lithotripsy.

Temperature profiles during ureteroscopy with thulium fiber laser and holmium:YAG laser: Findings from a pre-clinical study

OBJECTIVE

The aim of this study was to investigate temperature profiles in both the renal pelvis and parenchyma during Thulium Fiber Laser (TFL) and Holmium:yttrium-aluminium-garnet (Ho:YAG) laser activation in an ex-vivo porcine model.

METHODS

Three porcine kidneys with intact renal pelvis and proximal ureters were used in the study. A temperature sensor was inserted through a nephrostomy tube into the renal pelvis and a second sensor was inserted directly into the renal parenchyma. Temperatures were recorded during continuous laser activation for 180 s, and for an additional 60 s after deactivation. TFL (150 μm and 200 μm) and Ho:YAG (270 μm) laser delivered power at settings of 2.4 W, 8 W, 20 W and 30 W.

RESULTS

Intrapelvic temperatures correlated directly to power settings. Higher power produced higher temperatures. For example, using a 150 μm fiber at 2.4 W resulted in a 2.6 °C rise from baseline (p = 0.008), whereas using the same fiber at 20 W produced a rise in temperature of 19.9 °C (p = 0.02). Larger laser fibers caused significantly higher temperatures compared to smaller fibers using equivalent power settings, e.g. mean temperature at 20 W using 150 μm was 39.6 °C compared to 44.9 °C using 200 μm, p < 0.001. There was a significant increase in parenchymal temperatures when applying 20 W and 30 W of laser power with the two larger fibers.

CONCLUSION

In this ex-vivo study, renal temperatures correlated directly to power settings. Higher power produced higher temperatures. Furthermore, larger laser fibers caused higher temperatures. These findings could help guide selection of safe power settings for ureteroscopic lithotripsy, but future clinical studies are needed for confirmation.

The effect of prolonged laser activation on irrigation fluid temperature: an in vitro experimental study

PURPOSE

To investigate the effect of prolonged laser activation on irrigation fluid temperature by varying the power settings flow rate (10-30 ml/min).

MATERIALS AND METHODS

An experimental study using a 20 ml syringe, 12/14 ureteral access sheath, a dual-lumen catheter and a thermocouple was performed. The laser was fired with 12 W (0.3 J × 40 Hz), 40 W (1 J × 40 Hz), 60 W (1.5 J × 40 Hz) using Quanta Ho 150 W (Quanta System, Samarate, Italy). All trials were performed with fluid outflow rate of 10, 20 and 30 ml/min with the fixed fluid volume at 10 ml.

RESULTS

Continuous laser activation for 10 min with the outflow rate of 10 ml/min using only 12 W resulted to continuous temperature rise to as high as 83 °C. Similar rise of temperatures were observed for 40 W and 60 W with 10 ml/min outflow rate with intermittent laser activation. With 20 and 30 ml/min outflow rates the maximum temperatures for all power settings were below the threshold (< 43 °C). However, the time to reach the same total emitted energy was 60% and 40% shorter 60 W and 40 W, respectively.

CONCLUSION

Our study found that continuous laser activation with as less as 12 W using 10 ml/min outflow rate increased the irrigation fluid temperature above the threshold only after 1 min. In the current experimental setup, with the fluid outflow rate of 20 and 30 ml/min safe laser activation with 60 W and 40 W (temperature < 43 °C) can be achieved reaching the same total emitted energy as with 12 W in significantly shorter time period.

Retrograde intrarenal surgery: laser showdown (Ho:YAG vs thulium fiber laser)

PURPOSE OF REVIEW

Retrograde intrarenal surgery (RIRS) has always been recommended for large stones > 20 mm, using the Ho:YAG laser. The introduction of a new technology in the urological market, the thulium fiber laser (TFL) has revolutionized the endourology world because of its characteristics and significantly shorter laser-on time (LOT) and operative time, without scarifying the champ vision. The aim of this review is to evaluate the most relevant findings of the last 2 years of each laser technology, confronting Ho:YAG vs TFL, analyzing who is more suitable for performing an efficient RIRS.

RECENT FINDINGS

Five full clinical trials using TFL for RIRS were found. Median LOT was between 2.8 and 34 min. All stones were similar in terms of stone volume, >500 mm3, and stone density, > 800 HU. Low complication rate, mostly Clavien-Dindo grade I and II and not related to the laser itself. One clinical trial only analyzed the efficacy of TFL for > 20 mm renal stones.

SUMMARY

Based on this review, TFL performs a more efficient RIRS than the Ho:YAG laser with similar safety.

New Lasers for Stone Treatment

Laser technology has been a breakthrough in urology. The new era in endocorporeal laser lithotripsy has recently begun in mid-2020, where promising technologies tested in vitro have reached their approval for clinical use and, in that way, have made it possible to confirm their safety and advantages in the real world, for the patient and for the urologist.

Superpulse thulium fiber laser lithotripsy: an in vitro comparison of 200 μm and 150 μm laser fibers

PURPOSE

To investigate the thermal effects, stone retropulsion and ablation rate of SuperPulse Thulium-fiber laser (SP TFL) with two different surgical fibers of 200 and 150 μm in diameter.

METHODS

SP TFL (NTO IRE-Polus, Fryazino, Russia) performance with 200 and 150 μm fibers (NTO IRE-Polus, Fryazino, Russia) was evaluated. Before each test, the laser fiber was cleaved, and the power measurement was taken to verify the actual laser output power. To compare the laser fibers in well-controlled environments, a number of setups were used to assess retropulsion, ablation efficacy, fiber burnback, energy transmission, and safety.

RESULTS

Power measurements performed before each test revealed a 4.7% power drop for a 200 μm fiber SP TFL (14.3 ± 0.5 W) and 7.3% power drop for a 150 μm fiber SP TFL (13.9 ± 0.5 W) versus the nominally indicated power (15.0 W). Retropulsion with the TFL was minimal and comparable between fibers. We found no clinically relevant temperature differences between SP TFL with either 200 or 150 μm fibers. The ablation efficacy tended to be comparable under most parameters. Yet, we did observe a decreased diameter of residual fragments after the ablation with a 150 μm fiber.

CONCLUSION

The smaller fiber (150 μm) is not inferior to 200 μm fiber in terms of fiber burnback, retropulsion, safety, and ablation rate. Moreover, it has the potential to decrease the diameter of fragments during lithotripsy, which may facilitate dusting during RIRS.

Managing Urolithiasis with Thulium Fiber Laser: Updated Real-Life Results-A Systematic Review

Thirty-three years ago, pulsed lasers marked the beginning of a new era in endoscopic lithotripsy, and the one that was highlighted because of its potential was the Holmium: YAG laser, which became and still is the gold standard in endourology. Recently, a new laser technology has been accepted for clinical use in lithotripsy: the thulium fiber laser (TFL), showing appealing characteristics not seen before in several preclinical studies. A review of the literature was performed and all relevant in vitro studies and clinical trials until April 2021 were selected. The search came back with 27 clinical experiences (7 full-text clinical trials and 20 peer-reviewed abstracts) and 33 laboratory studies (18 full-text articles and 15 peer-reviewed abstracts). The clinical experiences confirmed the clinical safety of using the wide parameter range of the TFL. This technology demonstrated the performance at a higher ablation speed, the higher ablation efficiency, and the better dust quality of the TFL, as well as reduced stone retropulsion, thus helping to maintain an optimal visibility. No thermal or radiation damage was found. Given the current evidence, we may be facing the future gold standard laser in endoscopic lithotripsy.

Ureteroscopic Performance of High Power Super Pulse Thulium Fiber Laser for the Treatment of Urolithiasis: Results of the First Case Series in North America

OBJECTIVE

To report the first case series of ureterorenoscopy in North America using the High Power Super Pulse Thulium Fiber Laser for the treatment of upper urinary tract stones.

METHODS

After Institutional Review Board approval, a multicentric retrospective chart review of patients treated with the High Power Super Pulse Thulium Fiber Laser from October 2019 to March 2020 was conducted. Basic demographic information, pre-operative, and peri-operative data were recorded.

RESULTS

Seventy-six patients were included with a mean age of 60.9 ± 13.3 years. 118 stones were treated including 32 within the ureter, 49 in the lower pole, 37 in mid or upper poles. Dusting technique was commonly used (67.1%) with pulse frequencies up to 2400 Hz. Mean operative time was 59.4 ± 31.5 minutes. Mean laser time and total laser energy were 10.8 ± 14.1 minutes and 12.5 ± 19.1 KJ, respectively. Intraoperative complications were limited to 7 grade 1, 3 grade 2, and 1 grade 3 ureteral injuries and one case of renal collecting system bleeding that was adequately managed with laser coagulation settings (1J-20Hz).

CONCLUSION

This initial case series in North America of the High Power Super Pulse Thulium Fiber Laser is promising for the treatment of urolithiasis. Sub-200 μm fibers and dusting settings up to 2400 Hz were utilized successfully. No specific complications related to use of the laser were seen.

Retrograde intrarenal surgery versus percutaneous nephrolithotomy in larger kidney stones. Could SuperPulsed Thulium-fiber laser change the game?

Introduction

The aim of this article was to compare retrograde intrarenal surgery (RIRS) and percutaneous nephrolithotomy (PCNL) efficacy and safety with SuperPulsed Thulium-fiber laser (SP TFL) for stones 20 mm and larger.

Material and methods

Patients with large kidney stones (20 mm and larger) were recruited to undergo PCNL or RIRS with SP TFL lithotripsy. Both groups were comparable in terms of stone size and density, operation time, laser-on time (LOT), stone-free rate, residual fragments and complication rate. Stone retropulsion and visibility were assessed based on the surgeon's feedback using Likert scales.

Results

A total of 14 and 56 patients were included in the RIRS and PCNL groups, respectively. The mean stone density was 833.8 ±298.3 HU in the RIRS group and 882.3 ±408.5 HU in the PCNL group (p = 0.072). The median LOT was 11.7 (10.0-15.5) min for RIRS and 10.0 (6.0-12.1) min for PCNL (p = 0.207). The median total energy for stone ablation was 13.8 (11.8-25.0) kJ for RIRS and 12.0 (7.0-20.1) kJ for PCNL (p = 0.508). The median ablation speed was 3.9 (3.9-5.7) mm³/sec for RIRS and 5.0 (4.6-11.3) mm³/sec for PCNL (p = 0.085). We found a significant correlation between retropulsion and the type of surgery performed: with higher retropulsion in the PCNL (r = 0.298 with p = 0.012). The stone-free rate at 3-months was 85.7% in RIRS and 89.3% in PCNL (p = 0.505).

Conclusions

SP TFL is a safe and effective modality for lithotripsy for both, RIRS and PCNL, achieving minimal retropulsion and good visibility. No discrepancies in procedure duration, complications, or LOT were identified between the different modalities.

Caveat Emptor: The Heat Is "ON": An In Vivo Evaluation of the Thulium Fiber Laser and Temperature Changes in the Porcine Kidney during Dusting and Fragmentation Modes

INTRODUCTION

We sought to examine the intrarenal fluid and tissue temperature during dusting and fragmentation with the Thulium fiber laser (TFL) in an in vivo porcine kidney.

METHODS

In two pigs, temperature was continuously measured within the upper, middle, and lower calyces and at the tip of the ureteroscope. Four experimental protocols were performed: dual lumen ureteroscope with both warmed (37°C) and room temperature (20-22ºC) irrigation and single lumen ureteroscope with warmed and room temperature irrigation. In each pig, one kidney had a 14F ureteral access sheath (UAS), other kidney had no UAS. A 200µm TFL was fired at three settings: dusting (0.5J, 80Hz, 40W) with continuous activation for 5 minutes or until a temperature reached 44⁰C; low power (1J, 10Hz, 10W) and high-power fragmentation (1.5J, 20Hz, 30W). For fragmentation, the laser was activated for 10 seconds with a 2 second intermission for 1 minute.

RESULTS

In the absence of an UAS, in all but one circumstance, temperatures exceeded 44ºC at all settings with the use of either warm or room temperature irrigation, regardless of the type of ureteroscope. Temperatures recorded at the ureteroscope tip were 4ºC - 22ºC less than the temperatures recorded in the renal calyces. In contrast, with a 14F UAS in place, 6 distinct groups had temperatures that did not exceed 44ºC, specifically at low and high-power fragmentation settings with room temperature irrigation for both sets of ureteroscopes and at dusting and low-power fragmentation settings with warm temperature irrigation solely for the single lumen ureteroscope. Temperatures at the ureteroscope tip with an UAS yielded temperature differences from 17ºC less to 19ºC more than the renal calyces.

CONCLUSIONS

Thulium fiber laser is a novel technology for lithotripsy. In the absence of a UAS, high-power TFL fragmentation settings, may create temperatures that could result in urothelial tissue injury.

High-power actively Q-switched Ho-doped gadolinium tantalate laser

In this paper, we present the acousto-optical (AO) Q-switched performance of a holmium (Ho):gadolinium tantalate (GdTaO₄) (Ho:GTO) laser pumped by a thulium (Tm)-fiber laser emitting at 1.94 µm. In the efficient continuous wave (CW) regime, a maximum output power of 30.5 W at 2068.8 nm was achieved, corresponding to a slope efficiency of 74.9% with respect to the absorbed pump power. In the Q-switching regime, pulse energies of 2.4 mJ, 1.2 mJ, and 0.9 mJ were obtained with pulse repetition frequencies of 10 kHz, 20 kHz, and 30 kHz, respectively. The minimum pulse widths were 18 ns, 23 ns, and 26 ns, corresponding to peak powers of approximately 133.3 kW, 52.2 kW, and 34.6 kW, respectively.

Minimally invasive percutaneous nephrolithotomy with SuperPulsed Thulium-fiber laser

We aimed to assess the efficacy and safety of minimally invasive percutaneous nephrolithotomy (PCNL) with SuperPulsed Thulium-fiber laser (SP TFL) using different frequency settings. 125 patients with solitary kidney calculi of up to 55 mm in the maximum diameter underwent mini-PCNL with the SP TFL. Stone-free rate, laser-on time, ablation efficacy, energy consumption, ablation speed and complications were all analyzed. Negative low-dose computed tomography scan or asymptomatic patients with stone fragments < 2 mm were the criteria for assessing the stone-free status. In 36 patients (28.8%) low frequency regimens were used (LF: 3-19 Hz-0.5-6 J), in 75 patients (60%) high frequency regimens were chosen (HF: 20-49 Hz-0.2-2 J) and in 14 (11.2%) patients higher frequency (HRF: 50-200 Hz-0.1-0.5 J) regimens were preferred. The mean age was 52 ± 1.8 years. Median stone diameter and median stone volume were larger at low frequency regimens compared to high frequency regimens. Ablation efficacy (J/mm³) was lower at low rather than at high frequency regimens. Ablation speed (mm³/sec) was higher at low compared to high frequency regimens. Surgeons reported minimal and absent retropulsion at higher frequency regimens. The best visibility was observed at high frequency regimens. The overall stone free rate (SFR) at 3 months was 85%. The majority of the postoperative complications were classified between Clavien grades I-II. SP TFL is an effective and safe tool for performing mini-PCNL regardless of the laser settings.

Endoscopic lithotripsy with a SuperPulsed thulium-fiber laser for ureteral stones: A single-center experience

OBJECTIVES

To estimate the efficacy and safety of SuperPulsed thulium-fiber laser ureteral lithotripsy and to identify optimal laser settings.

METHODS

Patients with solitary stones were prospectively included. Lithotripsy was performed with a SuperPulsed thulium-fiber laser (NTO IRE-Polus, Fryazino, Russia) using a rigid ureteroscope 7.5 Ch (Richard Wolf, Knittlingen, Germany). We analyzed the efficacy of lithotripsy by measuring total energy required for stone disintegration, "laser-on" time, ablation speed, ablation efficacy, and energy consumption. Stone retropulsion and visibility were assessed using a three-point Likert scale. Complications were assessed using the Clavien-Dindo classification system.

RESULTS

A total of 149 patients were included. The mean stone density was 985 ± 360 Hounsfield units, the median (interquartile range) stone volume was 179 (94-357) mm3 . The median (interquartile range) total energy was 1 (0.4-2) kJ, and laser-on time 1.2 (0.5-2.7) min. The median (interquartile range) stone ablation speed was 140 (80-279) mm3 /min, energy for ablation of 1 mm3 was 5.6 (3-9.9) J/mm3 and energy consumption was 0.9 (0.6-1) J/min. A correlation was found between retropulsion and the energy used (r = 0.5, P < 0.001). Multivariable analysis showed energy to be a predictor of increased retropulsion (odds ratio 65.7, 95% confidence interval 1.6-2774.1; P = 0.028). No predictors for worse visibility were identified.

CONCLUSION

The SuperPulsed thulium-fiber laser provides effective and safe lithotripsy during ureteroscopy regardless of stone density. Fiber diameter and laser frequency do not influence visibility or safety. Optimal laser settings are 0.5 J × 30 Hz for fragmentation and 0.15 J × 100 Hz for dusting.

Outcomes of thulium fibre laser for treatment of urinary tract stones: results of a systematic review

PURPOSE OF REVIEW

Lasers have become a fundamental aspect of stone treatment. Although Holmium:Yttrium-Aluminum-garnet (Ho:YAG) laser is the current gold-standard in endoscopic laser lithotripsy, there is a lot of buzz around the new thulium fibre laser (TFL). We decided to evaluate the latest data to help create an objective and evidence-based opinion about this new technology and associated clinical outcomes.

RECENT FINDINGS

Sixty full-text articles and peer-reviewed abstract presentations were included in the qualitative synthesis of this systematic review performed over the last 2 years. Current super pulsed TFL machines are capable of achieving peak powers of 500W and emit very small pulse energies of 0.025 Joules going up to 6 Joules, and capable of frequency over 2000 Hz. This makes the TFL ablate twice as fast for fragmentation, 4 times as fast for dusting, more stone dust of finer size and less retropulsion compared to the Ho:YAG laser. Because of the smaller laser fibres with the TFL, future miniaturization of instruments is also possible.

SUMMARY

Based on the review, the TFL is a potential game-changer for kidney stone disease and has a promising role in the future. However larger multicentric prospective clinical studies with long-term follow-up are needed to establish the safety and efficacy of the TFL in endourology.

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.

Temperature Assessment of a Novel Pulsed Thulium Solid-State Laser Compared with a Holmium:Yttrium-Aluminum-Garnet Laser

Purpose: To compare a novel Thulium laser device with the commonly used Holmium:Yttrium-Aluminum-Garnet (Ho:YAG) laser in terms of the in vitro temperatures generated. Methods: Our study investigated and compared an evaluation model of a solid-state Thulium laser with a Medilas H Solvo 35 Holmium laser device, both by Dornier (Dornier MedTech Laser GmbH, Wessling, Germany). Our in vitro model consisted of a 20 mL test tube placed in a 37°C water bath. Constant irrigation was set at 50 mL/minute with a Reglo Z Digital pump (Cole Parmer, Chicago, IL). Four hundred micrometers of Dornier laser fibers were used. The temperature was measured with a type K thermocouple and a real-time data logger from Pico (PICO Technology, Cambridgeshire, United Kingdom). Power settings between 2 and 30 W were investigated. Each measurement lasted 120 seconds and was repeated five times. The data were evaluated by MATLAB^® (The Mathworks, Inc., Natick, MA). Results: The resulting temperatures were directly proportional to the power supplied. When comparing Holmium with Thulium, we observed maximum deviations of ≤0.82 K in temperatures at 120 seconds. The highest investigated laser power of 30 W yielded maximum temperatures differing by 6.7 K from the initial value. Out of the five comparisons, Thulium showed marginally yet significantly lower end temperatures in four cases and slightly lower cumulative equivalent minutes at 43°C (CEM₄₃) values in three cases. Conclusion: The Thulium laser resembles the Holmium device in the temperatures generated during in vitro application. An increase in laser power, thus, leads to equivalent increases in temperature that are largely independent of frequency, pulse duration, and single pulse energy. Pulsed Thulium:Yttrium-Aluminum-Garnet (Tm:YAG), Ho:YAG, and Thulium fiber laser seem to share a similar risk profile for patients in terms of temperature development. Intrarenal power outputs exceeding 10 W during clinical application should be compensated by ensuring sufficient irrigation.

Temperature profiles of calyceal irrigation fluids during flexible ureteroscopic Ho:YAG laser lithotripsy

PURPOSE

To evaluate calyceal irrigation fluid temperature changes during flexible ureteroscopic Ho:YAG laser lithotripsy.

METHODS

Between May 2019 and January 2020, patients with kidney stones undergoing flexible ureteroscopic Ho:YAG laser lithotripsy were enrolled. A K-type thermocouple was applied for intraoperative temperature measurement. Laser was activated at different power (1 J/20 Hz and 0.5 J/20 Hz) and irrigation (0 ml/min, 15 ml/min and 30 ml/min) settings, temperature-time curve was drawn and time needed to reach 43 °C without irrigation was documented.

RESULTS

Thirty-two patients were enrolled in our study. The temperature-time curve revealed a quick temperature increase followed by a plateau. With 15 ml/min or 30 ml/min irrigation, 43 °C was not reached after 60 s laser activation at both 1 J/20 Hz and 0.5 J/20 Hz. At the power setting of 1 J/20 Hz and irrigation flow rate of 15 ml/min, the temperature rise was significantly higher than other groups. Without irrigation, the time needed to reach 43 °C at 1 J/20 Hz was significantly shorter than that at 0.5 J/20 Hz (8.84 ± 1.41 s vs. 13.71 ± 1.53 s).

CONCLUSION

Ho:YAG laser lithotripsy can induce significant temperature rise in calyceal fluid. With sufficient irrigation, temperatures can be limited so that a toxic thermal dose is not reached, when irrigation is closed, the temperature increased sharply and reached 43 °C in a few seconds.

Superpulsed Thulium Fiber Laser for Stone Dusting: In Search of a Perfect Ablation Regimen-A Prospective Single-Center Study

Objective: To compare the efficacy of the standard and higher frequency regimens for superpulsed thulium fiber laser (SP TFL) retrograde intrarenal surgery (RIRS). Materials and Methods: A prospective study of patients with renal calculi of 10-30 mm was performed. For RIRS, we used the SP TFL (NTO IRE-Polus, Russia) and a 9.5F flexible ureteroscope with 270° deflection and 3.6F working channel. Retropulsion and visibility were assessed based on the surgeon's feedback using three-point Likert scales. The stone-free rate was assessed at 3 months with CT. Results: A total of 40 patients were included in the study with a mean age of 56 years, mean stone density of 880 ± 381 HU, mean stone size of 16.5 ± 6.8 mm, and median stone volume of 883 (interquartile range 606-1664) mm³. Both ablation efficacy and speed were higher in the 200-Hz mode (2.7 J/mm³ vs 3.8 J/mm³ and 5.5 mm³/second vs 8.0 mm³/second, respectively); moreover, the higher frequency correlated with increased ablation speed (r = -0.21, p = 0.019). However, both increased energy and frequency did not lead to increase of laser-on time or intraoperative complication rates. Conclusions: SP TFL is able to effectively disintegrate stones during RIRS with minimal complication rates. The use of higher frequency regimens showed higher efficacy and ablation speed and was not associated with increased complication rates.