A review of thulium-fiber laser in stone lithotripsy and soft tissue surgery

Flexible ureteroscopic treatment of kidney stones: How do the new laser systems change our concepts?

Objective

Flexible ureteroscopy (fURS) has become a widely accepted and effective technique for treating kidney stones. With the development of new laser systems, the fURS approach has evolved significantly. This literature review aims to examine the current state of knowledge on fURS treatment of kidney stones, with a particular focus on the impact of the latest laser technologies on clinical outcomes and patient safety.

Methods

We conducted a search of the PubMed/PMC, Web of Science Core Collection, Scopus, Embase (Ovid), and Cochrane Databases for all randomized controlled trial articles on laser lithotripsy in September 2023 without time restriction.

Results

We found a total of 22 relevant pieces of literature. Holmium laser has been used for intracavitary laser lithotripsy for nearly 30 years and has become the golden standard for the treatment of urinary stones. However, the existing holmium laser cannot completely powder the stone, and the retropulsion of the stone after the laser emission and the thermal damage to the tissue have caused many problems for clinicians. The introduction of thulium fiber laser and Moses technology brings highly efficient dusting lithotripsy effect through laser innovation, limiting pulse energy and broadening pulse frequency.

Conclusion

While the holmium:yttrium-aluminum-garnet laser remains the primary choice for endoscopic laser lithotripsy, recent technological advancements hint at a potential new gold standard. Parameter range, retropulsion effect, laser fiber adaptability, and overall system performance demand comprehensive attention. The ablation efficacy of high-pulse-frequency devices relies on precise targeting, which may pose practical challenges.

Thulium fiber laser vs Ho:YAG in RIRS: a prospective randomized clinical trial assessing the efficacy of lasers and different fiber diameters (150 µm and 200 µm)

INTRODUCTION

The aims of the study: (1) to compare the Super Pulse Thulium Fiber Laser (SP TFL) and the holmium: yttrium-aluminium-garnet (Ho:YAG) lasers in retrograde intrarenal surgery (RIRS); (2) to compare the efficacy of SP TFL laser fibers of different diameters (150 μm and 200 μm).

METHODS

A prospective randomized single-blinded trial was conducted. Patients with stones from 10 to 20 mm were randomly assigned RIRS in three groups: (1) SP TFL (NTO IRE-Polus, Russia) with fiber diameter of 150 μm; (2) SP TFL with 200-μm fiber; and (3) Ho:YAG (Lumenis, USA) with 200-μm fiber.

RESULTS

Ninety-six patients with kidney stones were randomized to undergo RIRS with SP TFL using a 150-μm fiber (34 patients) and a 200-μm fiber (32 patients) and RIRS with Ho:YAG (30 patients). The median laser on time (LOT) in the 200-μm SP TFL group was 9.2 (6.2-14.6) min, in 150-μm SP TFL-11.4 (7.7-14.9) min (p = 0.390), in Ho:YAG-14.1 (10.8-18.1) min (p = 0.021). The total energy consumed in 200-μm SP TFL was 8.4 (5.8-15.2) kJ; 150-μm SP TFL - 10.8 (7.3-13.5) kJ (p = 0.626) and in Ho:YAG-15.2 (11.1-25.3) kJ (p = 0.005).

CONCLUSIONS

Irrespective of the density, RIRS with SP TFL laser has proven to be both a safe and effective procedure. Whilst the introduction of smaller fibers may have the potential to reduce the duration of surgery, SP TFL results in a reduction in the LOT and total energy for stone ablation in RIRS compared with Ho:YAG.

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

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

A Review of How Lasers Are Used in UTUC Surgery: Can the Choice of Laser Affect Outcomes?

Upper tract urothelial carcinoma (UTUC) is a relatively rare disease with an aggressive phenotype compared to urothelial carcinoma in the bladder. In recent years, kidney-sparing surgery (KSS) and, in particular, endoscopic surgery have become the procedure of choice among urologists where the treatment of localized UTUC is concerned. Endoscopy tends to result in satisfactory oncological disease control while lowering morbidity and minimizing complications amongst the appropriately selected cohort of patients. While endoscopic surgery for UTUC might appear to be standardized, it, in fact, differs considerably depending on the source of energy used for resection/ablation. There has been little reliable data up to now on which laser energy source is the most superior. The goal of this review is, therefore, to outline the results of endoscopic UTUC treatment using different lasers and to analyze how these laser-tissue interactions may affect the surgery. We start by pointing out that the data remains insufficient when trying to determine which laser is the most effective in the endoscopic management of UTUC. The ever-growing number of indications for minimally invasive treatment and the increasing number of centers using laser surgery will, hopefully, lead to novel randomized controlled trials that compare the performance characteristics of the lasers as well as the effects of UTUC on patients.

En bloc resection for nonmuscle-invasive bladder cancer: selecting a proper laser

PURPOSE OF REVIEW

To discuss the most recent surgical lasers that have been made available to us and to evaluate their potential in performing en bloc resection of nonmuscle invasive bladder cancer.

RECENT FINDINGS

Laser en bloc resection of bladder tumors (ERBT) can be performed with a number of laser systems including Ho:YAG, GreenLight, diode, Tm:YAG and thulium fiber lasers (TFL). The data that is currently available suggests that the water-targeting devices (utilizing water as a primary chromophore - Ho:YAG, Tm:YAG, TFL) may have a number of advantages over hemoglobin-targeting systems (potassium titanyl phosphate:YAG, lithium triborate:YAG). One recent addition to the surgical armamentarium Moses effect enhanced Ho:YAG and the TFL (being able to work both in quasi-continuous and SuperPulsed modes) necessitates careful discussion and comparison with the other available devices.

SUMMARY

The majority of available lasers have proven to be safe to use and compared to electrocautery allow for lower rates of obturator nerve reflex and result in fewer bleeding complications. The minimal penetration depth and decreased peak power of Tm:YAG and TFLs render them the devices of choice when it comes to ERBT. Unfortunately, more studies on ERBT with TFL are needed in order for us to make a sound assessment of the respective pros and cons.

In vitro fragmentation performance of a novel, pulsed Thulium solid-state laser compared to a Thulium fibre laser and standard Ho:YAG laser

The aim of this work was to compare the fragmentation efficiency of a novel, pulsed Thulium solid-state laser (p-Tm:YAG) to that of a chopped Thulium fibre laser (TFL) and a pulsed Holmium solid-state laser (Ho:YAG). During the fragmentation process, we used a silicone mould to fixate the hemispherical stone models under water in a jar filled with room-temperature water. Each laser device registered the total energy applied to the stone model to determine fragmentation efficiency. Our study examined laser settings with single pulse energies ranging from 0.6 to 6 J and pulse frequencies ranging from 5 to 15 Hz. Similar laser settings were applied to explicitly compare the fragmentation efficiency of all three devices. We experimented with additional laser settings to see which of the three devices would perform best. The fragmentation performance of the three laser devices differed statistically significantly (p < 0.05). The average total energy required to fragment the stone model was 345.96 J for Ho:YAG, 372.43 J for p-Tm:YAG and 483.90 J for TFL. To fragment the stone models, both Ho:YAG and p-Tm:YAG needed similar total energy (p = 0.97). TFL’s fragmentation efficiency is significantly lower than that of Ho:YAG and p-Tm:YAG. Furthermore, we found the novel p-Tm:YAG’s fragmentation efficiency to closely resemble that of Ho:YAG. The fragmentation efficiency is thought to be influenced by the pulse duration. TFL’s shortest possible pulse duration was considerably longer than that of Ho:YAG and p-Tm:YAG, resulting in Ho:YAG and p-Tm:YAG exhibiting better fragmenting efficiency.

Current status of thulium fibre laser lithotripsy: an up-to-date review

OBJECTIVE

To perform an up-to-date review to scope the current status of the thulium fibre laser (TFL) in the setting of stone lithotripsy and provide a guide for the clinical urologist.

METHODS

A review of world literature was performed to identify original articles on TFL for stone lithotripsy. Our clinical experiences of using the technology have also been shared.

RESULTS

To date there have been 11 clinical studies published on TFL for stone lithotripsy. Three of these have been in the setting of miniaturised percutaneous nephrolithotomy (mini-PCNL) and the remainder have been on ureteroscopy (URS). There has only been one randomised study on this technology, which has been for URS. For URS, the range of settings has been 0.1-4 J × 7-300 Hz for both URS and mini-PCNL. Stones ranging from 0.4-3.2 and 1.5-3 cm have been treated with URS and mini-PCNL, respectively. The final stone-free rate for TFL has ranged from 66.6% to 100% and 85-100% for URS and mini-PCNL, respectively. The average length of stay ranged from 0.5 to 2.4 days in the URS group, but no studies have been reported this for mini-PCNL. Operative times in all the studies (both URS and mini PCNL) were <60 min.

CONCLUSION

Initial clinical studies reveal that TFL appears to be efficacious in the setting of stone lithotripsy. However, further randomised trials are warranted to delineate its formal position, as well as determine the optimal settings for use in clinical practice.

Experimental ex-vivo performance study comparing a novel, pulsed thulium solid-state laser, chopped thulium fibre laser, low and high-power holmium:YAG laser for endoscopic enucleation of the prostate

Purpose

The aim of this study was to compare the enucleation performances of four different types of laser devices in an ex-vivo experiment: a novel, pulsed Tm:YAG solid-state laser evaluation model (p-Tm:YAG), chopped thulium fibre laser (TFL), low-power Ho:YAG laser (LP-Ho:YAG), and a high-power Ho:YAG laser (HP-Ho:YAG).

Methods

Our primary aim was to endoscopically separate the fascial layers of a porcine belly using laser fibres within a time period of 60 s. The size of a “tissue pocket” was assessed numerically. The enucleation characteristics reflecting the surgeon’s experience were evaluated via the NASA Task Load Index (TLX) questionnaire and a questionnaire based on Likert scale.

Results

HP-Ho:YAG achieved with the available laser settings the largest overall “tissue pocket” (31.5 cm²) followed by p-Tm:YAG (15 cm²), TFL (12 cm²), and LP-Ho:YAG (6 cm²). The coagulation performances of p-Tm:YAG and TFL were rated the best. In the performance evaluation by the Likert questionnaire, HP-Ho:YAG (average score of 4.06) was rated highest, followed by p-Tm:YAG (3.94), TFL (3.38), and LP-Ho:YAG (3.25). The evaluation of the NASA-TLX performance questionnaire revealed average scores for HP-Ho:YAG, LP-Ho:YAG, TFL and p-Tm:YAG of 4.38, 4.09, 3.92 and 3.90, respectively.

Conclusion

We are the first to compare different laser devices and settings in an ex-vivo study. We found that the surgeons were most satisfied with the HP-Ho:YAG laser device, followed by the p-Tm:YAG. These findings could be highly relevant for future research and for the practical utilisation of laser systems in endourology.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00345-021-03825-z.

Comparison of Holmium:YAG and Thulium Fiber Lasers on the Risk of Laser Fiber Fracture

Objectives: To compare the risk of laser fiber fracture between Ho:YAG laser and Thulium Fiber Laser (TFL) with different laser fiber diameters, laser settings, and fiber bending radii. METHODS: Lengths of 200, 272, and 365 μm single use fibers were used with a 30 W Ho:YAG laser and a 50 W Super Pulsed TFL. Laser fibers of 150 µm length were also tested with the TFL only. Five different increasingly smaller bend radii were tested: 1, 0.9, 0.75, 0.6, and 0.45 cm. A total of 13 different laser settings were tested for the Ho:YAG laser: six fragmentation settings with a short pulse duration, and seven dusting settings with a long pulse duration. A total of 33 different laser settings were tested for the TFL. Three laser settings were common two both lasers: 0.5 J × 12 Hz, 0.8 J × 8 Hz, 2 J × 3 Hz. The laser was activated for 5 min or until fiber fracture. Each measurement was performed ten times. Results: While fiber failures occurred with all fiber diameters with Ho:YAG laser, none were reported with TFL. Identified risk factors of fiber fracture with the Ho:YAG laser were short pulse and high energy for the 365 µm fibers (p = 0.041), but not for the 200 and 272 µm fibers (p = 1 and p = 0.43, respectively). High frequency was not a risk factor of fiber fracture. Fiber diameter also seemed to be a risk factor of fracture. The 200 µm fibers broke more frequently than the 272 and 365 µm ones (p = 0.039). There was a trend for a higher number of fractures with the 365 µm fibers compared to the 272 µm ones, these occurring at a larger bend radius, but this difference was not significant. Conclusion: TFL appears to be a safer laser regarding the risk of fiber fracture than Ho:YAG when used with fibers in a deflected position.

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.

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.

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.