Research on the Efficiency and Safety of the Pulse Thulium Fiber Laser Lithotripsy through model Experimental

Research on the Efficiency and Safety of the Pulse Thulium Fiber Laser Lithotripsy through model Experimental | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Research on the Efficiency and Safety of the Pulse Thulium Fiber Laser Lithotripsy through model Experimental Yucheng Yao, Jie Zhou, Haoyong Li, Kaizhi Zhang, Xiaofeng Zhu, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7798044/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective This study aims to investigate the physical interaction characteristics of thulium fiber laser (TFL) lithotripsy, to elucidate the influence of laser parameters on stone ablation efficiency and clinical safety, and thereby to guide the clinical application. Methods The experiment was established to investigate the laws of laser penetration depth and environmental water temperature rise under different condition. The potential for radiation and thermal damage to surrounding tissues was analyzed based on these laws. Concurrently, lithotripsy efficiency of different laser parameters was investigated by experiment. Results The laser penetration depth exceeding 5 mm in water if the long pulse width is over 1 ms, which poses a risk of radiative damage to surrounding tissues. When the TFL average power exceeds 30 W with insufficient irrigation its rate being lower than 40 mL/min, a rapid temperature rise surpassing 47℃ occurs and creating a risk of thermal injury to adjacent tissues. Furthermore, a pulse width greater than 500 µs is generally required to achieve high lithotripsy efficiency. Conclusion The lithotripsy efficiency of TFL is directly influenced by pulse width and power. However, since both long pulse widths and high average power can pose risks of damage to surrounding tissues, parameter optimization is important during TFL procedures. thulium fiber laser lithotripsy thermal injury penetration depth clinical safety Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 1. Introduction The development of flexible ureteroscopy has enabled laser lithotripsy for ureteral and renal calculi, significantly reducing invasive trauma, as demonstrated with Ho:YAG lasers [ 1 – 5 ] . The pulsed thulium fiber laser (TFL), operating at 1940 nm, is a promising technology which offers advantages over Ho:YAG lasers, including higher pulse rates and improving lithotripsy efficiency [ 4 , 6 – 8 ] . However, recent clinical studies raise concerns about its safety profile, reporting a higher incidence of postoperative complications and ureteral strictures comparing to Ho:YAG laser lithotripsy [ 9 – 11 ] . Notably, a study conducted in 2024 found the stricture rate of 11% with manufacturer-preset parameters without improving stone-free rates [ 11 ] , this concern has corroborated by other findings [ 12 ] . The mechanisms underlying these tissue injuries is need to be studied. This study aims to investigate the physical principles of TFL lithotripsy, specifically evaluating the thermal and laser radiation damage mechanisms [ 13 , 14 ] . It can guide the control of injury risk and the optimization of laser parameters in lithotripsy [ 15 , 16 ] . 2. Materials and Methods The primary mechanism of TFL lithotripsy involves laser-induced vapor bubble formation and micro-explosions, which generate shockwaves for stone fragmentation [ 17 – 19 , 20 ] . The direct water penetration of 1940 nm laser is minimal (< 0.2 mm) because of high absorption in water (129 cm⁻¹). However, with long pulse durations (1–6 ms), laser can propagate through vapor cavities, potentially reaching surrounding tissues. Nearly all laser energy is deposited as heat, which risks thermal injury to periureteral tissues if it is not dissipated [ 13 , 21 – 23 ] . Enhancing lithotripsy efficiency per unit energy can reduce the total energy requirement, thereby reducing the temperature rise. The working process of TFL lithotripsy are intrinsically determined by laser parameters, such as pulse width and peak power density. It is ideal that the laser energy acting on water within or on the surface of the stone is much as possible with suitable parameters. The temperature rise of the water environment and the laser radiation in soft tissues through vapor bubbles were identified as primary risk factors for tissue injury. An experimental apparatus was designed to measure the transmission of TFL pulses in water and the associated temperature rise during lithotripsy. The system was utilized to investigate fragmentation patterns under different conditions for the purpose of laser parameter optimization and safety assessment. As shown in Fig. 2 , the experimental setup included a pulsed TFL source, medical optical fibers and systems for temperature measurement and thermal imaging. The TFL was characterized by the peak power of 800W and continuously adjustable pulse width and repetition rate. Low-hydroxyl medical quartz fibers with core diameters of 400 µm and 600 µm were employed. A thermostatic circulator was used to maintain a constant temperature of the water in the beaker. Temperature signals of the water in the test tube were acquired and recorded using the data acquisition system, while the temperature field distribution was simultaneously monitored using the thermal imaging camera. Artificial calcium sulfate stone samples were fabricated to evaluate the lithotripsy efficiency and performance under different TFL parameters. The preparation protocol of the samples was as follows: Calcium Sulfate, gypsum powder, and deionized water were mixed at a mass ratio of 1:2:1.5 in a container; the mixture was stirred until homogeneous, then carefully poured into a cubic mold and allowed to solidify, yielding reproducible Calcium Sulfate stone phantoms. Ethical Statement: This article does not contain any studies with human participants or animals performed by any of the authors. The use of de-identified human stone samples for this in vitro study was in accordance with the ethical standards of the institution. 3. Results 3.1 Penetration Depth of TFL Pulses in the water environment The penetration depth of TFL pulses in water dictates the laser radiation area from the fiber tip. In the experiment, a layer of silicone material was embedded at the base of the beaker to simulate compliant soft tissue. A black light-absorbing material was attached to the silicone surface. The distance from the fiber tip to the aqueous boundary was carefully adjusted. Laser irradiation caused ablation and discoloration of the absorbing material, which was used to determine the laser pulse penetration depth in water. The fibers with the diameters of 400 μm and 600 μm were utilized. The results are presented in Fig.3. For a single TFL pulse at a peak power of 800 W, the penetration depth increased rapidly with increasing pulse width. At a pulse width of 1 ms, the penetration depth for the 600 μm and 400 μm fibers was measured to be 4.23 mm and 5.29 mm respectively. As the pulse width was further increased, the penetration depth increased continuously but the its rate was slow. At a pulse width of 6 ms, the penetration depth reached 7.52 mm and 7.89 mm respectively. It is concluded that the cavitation effect induced by long-duration TFL pulses significantly extends the effective penetration distance in water, it posing a potential threat to the safety of adjacent soft tissues. 3.2 Temperature Rise Effects During TFL Lithotripsy Under different Conditions A constant-temperature water environment at 37°C was maintained by means of a bath with recirculating warm water. A 10 mL test tube was immersed in the warm water to simulate the renal pelvis environment during lithotripsy. Irrigation with saline for cooling was administered within the tube using a flow-adjustable micro-peristaltic pump. A temperature probe was positioned approximately 10 mm from the fiber tip to record the water temperature, while the overall temperature field was captured by an infrared camera. At a laser power of 50 W and in the absence of irrigation cooling, the temperature of the water near the fiber tip increased rapidly, reaching 62℃ instantaneously (Fig. 4a). With an irrigation flow rate of 10 mL/min and a laser power of 50 W, the water temperature still kept over 54℃ (Fig. 4b). At the laser power of 50 W, without irrigation, temperature near the fiber tip rose rapidly, exceeding 60℃ within 10 seconds (Fig. 5), and with irrigation at 10 mL/min, temperature still exceeded 54℃(Fig. 6). The homeostasis temperature surpassed the 43℃ safety threshold at all power, reaching 45℃ at 20 W and 51℃ at 40 W. The water temperature will decline under 40℃ within 3 seconds if the laser stopping. The experiments shown that the irrigation flow rate was the predominant factor. As shown in Fig.7b, a laser power of 20W required over 30 mL/min irrigation to stabilize near the safety threshold. It could be seen from Fig.7c that a flow rate of 40-50 mL/min was necessary to maintain safe temperatures when the laser was 40W. Fig. 6 shows the temperature rise with different laser powers and an irrigation flow fixed at 10 mL/min. Due to the inherent flow dynamics, temperature fluctuations on the order of 3°C were observed. At this flow rate, a laser power of 10 W elevated the water temperature to the 43°C safety threshold. If the irrigation flow was 50 mL/min, a laser power of 40 W was also found to be operable within safe thermal limits (Fig. 7d). Higher flows increased temperature fluctuations due to enhanced turbulence. 3.3 Lithotripsy Efficiency of Pulsed TFL with Different Parameters Human urinary calculi exhibit substantial heterogeneity in morphology and composition, which complicates the assessment of TFL lithotripsy efficacy, so artificial samples were utilized for studding the efficacy rules in the experiment. Stones were positioned in water within a beaker, and the moving worktable was adjusted to maintain suitable distance of 0.5-1 mm between the stone surface and the fiber tip (Fig. 1). when the worktable was moving the laser beam would scan across the stone surface. Laser lithotripsy was performed for a duration of 1 minute, and the mass of ablated material was quantified using an analytical balance with different parameters. Upon laser irradiation, a substantial quantity of white powder generated instantaneously. Then they dispersed into the surrounding aqueous medium. A portion of the powder was drawn back towards the fiber tip due to recoil effects. With the TFL average power set to 10 W, the pulse width and repetition rate were modulated to measure the lithotripsy efficiency, as shown in Fig. 8. Effective lithotripsy was initiated only when the pulse width exceeded 200 μs (pulse energy of 0.16 J), and the lithotripsy efficiency increased precipitously with the pulse width increasing. For the 400 μm fiber, the lithotripsy efficiency reached a maximum at a pulse width of about 500 μs, being a slight decrease when the pulse width was further increased. The 600 μm fiber exhibited an analogous efficiency trend, but the peak efficiency occurred at a larger pulse width, and it was in the range of 1500-2000 μs. The fragmentation efficiency achieved by using the 400 μm fiber was 18% higher than that obtained with the 600 μm fiber. It is consistent with previous study [24] . The TFL lithotripsy physical process is complex and intimately linked to parameters such as pulse width and peak power density. The ablation morphology of the stones is presented in Fig.9. features indicative of thermal melting and ablation craters would be seen with larger pulse width. In the working process, the initial portion of the laser pulse interacts with water, generating shockwaves which cause mechanical fracture and spallation of the stone. Once the water was displaced, subsequent laser energy was deposited directly into the stone matrix, resulting in thermal ablation. A comparison of lithotripsy speeds at different repetition rates is shown in Fig.10. As the average power was increased, the lithotripsy speed increased rapidly, but the high lithotripsy efficiency appeared with suitable laser parameters. As shown in Fig.10, the lithotripsy efficiency was high under the condition of the repetition rate of 20 Hz and pulse width of 500-1000 μs. Human stones frequently exhibit porous structures. Moreover, during clinical lithotripsy, the smaller fragmented particles can be expelled spontaneously through the ureter. Consequently, laser lithotripsy does not invariably produce fine dust. Porous stone samples measuring 10 mm 3 were placed in a mesh bag with 3 mm squares suspended in water (Fig.11). Lithotripsy was performed by guiding the fiber manually. The procedure was deemed complete when all stone fragments had passed through the mesh. The efficiency under this simulation condition was analyzed. Under the condition of the laser power of 20 W and single pulse energies ranging from 0.15 J to 2 J, the lithotripsy efficiency is plotted in Fig.12. When the single pulse width exceeded 250 μs, further increase in pulse width did not significantly alter the lithotripsy efficiency, which stabilized around 156 mg/min. The fragmentation morphology was predominantly characterized by coarse fragments, with a maximum fragment size of 2.8 mm. If only larger stone fragments were crushed, the crushing efficiency of 1 ms pulse width exceeded 40% than it of 250 μs pulse width. Microscopic examination under different conditions confirmed that no thermal ablation features were produced in porous stones. The TFL lithotripsy validation experiment was conducted using a porous calcium oxalate human kidney stone sample (Fig.13), and the experimental results followed similar patterns. The pulsed laser frequency was set at 10 Hz in the experiment. The laser pulse width of 500 μs already showed a certain ability to fragment stones, while the laser with 1 ms pulse width had a stronger ability to break larger stones. 3.4 Retropulsion and Traction Dynamics in TFL Lithotripsy The generation and collapse of vapor bubbles during TFL lithotripsy can induce retropulsion and traction forces on the stone. The traction effect can limit the dispersion of larger fragments, facilitating the procedure and mitigating the need for additional anti-retropulsion devices [2] . Stone samples (3×3×3 mm³) were prepared, and the traction characteristics with different laser parameters were recorded in the experiment. Notable traction was observed only when the pulse energy exceeded 0.3J and the repetition rate was higher than 5 Hz. The most effective traction was achieved within the parameter range of 0.5 J and 40 Hz. However, the stone rotated at the fiber tip when the repetition rate over 30 Hz in the experiment. it makes the laser difficult to align the stone and is unable to effectively break stones in surgery, so during lithotripsy, only selecting appropriate parameters can improve the crushing stones really. 4. Discussion Ureteral mucosal tissue can suffer irreversible damage if exposed to an environment of 45°C for more than 8 minutes, and higher temperatures can cause damage more quickly, leading to complications such as strictures. During stone surgery, the cooling water needs to flow through the gaps of the inserted ureteral sheath and flexible ureteroscope, which imposes significant flow limitations and cannot ensure a consistently unobstructed state. It results in high risk of burns. Based on the experimental results, it can be seen that when perfusion is not smooth, such as the flow rate is less than 10 ml/min, the water temperature rises to above 53°C within 10 seconds with high laser power of 50 W, which can cause significant damage to soft tissues. Synthesis of the data presented in Figs.5 and Figs.6 indicates that TFL lithotripsy with an average output power below 20 W is associated with a relatively high safety margin. If higher power is clinically necessary, the irrigation flow rate must be meticulously monitored during the procedure to ensure that the heat is carried away in time. The unit energy lithotripsy efficiency is important for surgery and high efficiency can reduce heat deposition effectively and lower the risk of burns. Experimental results show that when using a 400 μm optical fiber, the efficiency of stone pulverization no longer changes significantly with increasing pulse width once the laser pulse width exceeds 300 μs (energy of 0.24 J). The similar patterns are observed in experiments on the particulate fragmentation of porous stone models, but for large stones, the ability of long-pulse-width lasers to break them is significantly enhanced. Additionally, experiments on the dynamics of stone fragmentation show that when the pulse frequency exceeds 30 Hz, small stones, such as size of 3 mm 3 , tend to rotate rapidly around the fiber tip, it making the laser aim at the stone more difficultly and reducing effective fragmentation ability. To ensure the necessary fragmentation speed, the average power cannot be too low, so in actual stone fragmentation procedures, doctors usually prefer to use a relatively long pulse width, typically reaching or exceeding 1 ms. According to the experimental results in Figs.3, the penetration depth of the laser pulse in water exceeds 5 millimeters under this condition. Meanwhile, it is difficult to determine whether it has irradiated soft tissue because of the 1940 nm wavelength laser being invisible in the stone-fragment environment. It is easy to cause radiation damage to the surrounding soft tissues. In summary, the lithotripsy effect and safety mainly depend on laser parameters, such as pulse width and average power [25] . In TFL lithotripsy surgery, special attention should be paid to laser radiation and high-temperature damage to surrounding tissues when using high pulse energy and high-power. In terms of parameter optimization, when the stone is large, using high pulse energy can improve lithotripsy efficiency, as the large stone may block the laser and have low laser leakage. When the stone is small, the pulse width should be reduced promptly to ensure safe lithotripsy. Declarations Conflicts of Interest: The authors declare that they have no conflicts of interest. Funding: This work was supported by the project " Laser Ablation System (No. 2020BED021) " Author Contribution Dr. Haoyong Li provided supervision; Yucheng Yao, Jie Zhou, and Kaizhi Zhang performed the experiments and drafted the main manuscript text; Xiaofeng Zhu, Jianjun Liu, and Hongwei Xiang provided laser technical support and prepared the figures. All authors reviewed the manuscript. References Andreeva V, Vinarov A, Yaroslavsky I, Kovalenko A, Vybornov A, Rapoport L, Enikeev D, Sorokin N, Dymov A, Tsarichenko D, Glybochko P, Fried N, Traxer O, Altshuler G, Gapontsev V (2020) Preclinical comparison of superpulse thulium fiber laser and a holmium: YAG laser for lithotripsy. World J Urol 38(2):497–503. https://doi.org/10.1007/s00345-019-02785-9 Vejdani K, Eisner BH, Pengune W, et al (2009) Effect of laser insult on devices used to prevent stone retropulsion during ureteroscopic lithotripsy. 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The heat is on: the impact of excessive temperature increments on complications of laser treatment for ureteral and renal stones. World J Urol 41, 3853–3865 (2023). https://doi.org/10.1007/s00345-023-04652-0 Hardy LA, Wilson CR, Irby PB, Fried NM (2014) Thulium fiber laser lithotripsy in an in vitro ureter model. J Biomed Opt 19(12):1280014 Dymov A, Glybochko P, Alyaev Y, Vinarov A, Altshuler G, Zamyatina V, Sorokin N, Enikeev D, Lekarev V, Proskura A et al (2017) Thulium lithotripsy: from experiment to clinical practice. J Urol 197(4):e1285 Li, Z., Wu, S., Liu, T. et al. Optimal parameter settings of thulium fiber laser for ureteral stone lithotripsy: a comparative study in two different testing environments. Urolithiasis 52, 78 (2024). https://doi.org/10.1007/s00240-024-01585-0 Additional Declarations No competing interests reported. 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1","display":"","copyAsset":false,"role":"figure","size":50156,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the experimental setup.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/9f1d60c01441861a90595d79.jpg"},{"id":95621456,"identity":"d0d062a2-5d44-4a41-b1df-4a87855825f4","added_by":"auto","created_at":"2025-11-11 09:43:56","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":65822,"visible":true,"origin":"","legend":"\u003cp\u003ePhotograph of the experimental setup.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/ffcfd586b108b8ac4322706c.jpg"},{"id":95657457,"identity":"1d2283cb-d215-42c9-bb4d-4a0c0ed8beab","added_by":"auto","created_at":"2025-11-11 16:20:54","extension":"jpg","order_by":3,"title":"Figure 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(b) With an irrigation flow rate of 10 mL/min.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/b215716e22c7427559a64f08.jpg"},{"id":95656254,"identity":"a1eddc27-600d-469c-911a-fd1daed3cf09","added_by":"auto","created_at":"2025-11-11 16:18:09","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":102964,"visible":true,"origin":"","legend":"\u003cp\u003eWater temperature change in the lithotripsy without irrigation cooling.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/89b5ff21bb3361806731ee06.jpg"},{"id":95656410,"identity":"9a9393a0-acaa-4e63-965e-1437d66cd7d6","added_by":"auto","created_at":"2025-11-11 16:18:37","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":106502,"visible":true,"origin":"","legend":"\u003cp\u003eDynamic water temperature in the lithotripsy with irrigation cooling at 10 mL/min.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/067ed631212caabb3a2d0965.jpg"},{"id":95621463,"identity":"ccc8e124-fb77-4d6e-9a34-331b877e1af3","added_by":"auto","created_at":"2025-11-11 09:43:56","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":324963,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature profiles under different irrigation flow rates and laser powers. Each subplot corresponds to a fixed irrigation flow rate: (a) 20, (b) 30, (c) 40, (d) 50 mL/min. Different curves within each subplot represent different laser powers (10-40 W).\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/722cd74b07f906af092baa98.png"},{"id":95657511,"identity":"bbd0260b-e80e-482b-a968-eb4a1433124b","added_by":"auto","created_at":"2025-11-11 16:21:01","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":86590,"visible":true,"origin":"","legend":"\u003cp\u003elithotripsy efficiency as a function of pulse width.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/d59c2e54dd757d1f75fa491e.jpg"},{"id":95621487,"identity":"7b5176cd-eb78-4f99-b2f0-553847c5f182","added_by":"auto","created_at":"2025-11-11 09:43:57","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":26849,"visible":true,"origin":"","legend":"\u003cp\u003eMorphology of ablated calculi.\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/3f9a3c2fee4c2c447e4aca93.jpg"},{"id":95621492,"identity":"1c2483cd-8f7d-4a01-b9aa-78e909932f71","added_by":"auto","created_at":"2025-11-11 09:43:57","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":60218,"visible":true,"origin":"","legend":"\u003cp\u003elithotripsy speeds with different laser parameters.\u003c/p\u003e","description":"","filename":"10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/637a226aaaa8e250ed3a1bf3.jpg"},{"id":95621499,"identity":"7f80ba5e-a603-48b1-a65c-430d467f2a41","added_by":"auto","created_at":"2025-11-11 09:43:58","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":74388,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of the net bag setup for fragment collection.\u003c/p\u003e","description":"","filename":"11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/94f92665e6654e1357cd4424.jpg"},{"id":95621467,"identity":"bc3c37a4-11ef-4624-a7f9-acea35902438","added_by":"auto","created_at":"2025-11-11 09:43:57","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":50431,"visible":true,"origin":"","legend":"\u003cp\u003elithotripsy efficiency with error bars indicating variability.\u003c/p\u003e","description":"","filename":"12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/4c431712d004a4bd99a71389.jpg"},{"id":95621475,"identity":"7f96aff3-5ba9-4d6e-9b87-4ee2a0e69843","added_by":"auto","created_at":"2025-11-11 09:43:57","extension":"jpg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":53909,"visible":true,"origin":"","legend":"\u003cp\u003elithotripsy experiment with human calcium oxalate stone\u003c/p\u003e","description":"","filename":"13.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/88d193bd67a23261e873a353.jpg"},{"id":104402472,"identity":"3c069829-2125-44e4-a534-73b3e81aa564","added_by":"auto","created_at":"2026-03-11 12:15:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1577031,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7798044/v1/8d568e5e-94fa-4203-845a-20fad4567ba2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Research on the Efficiency and Safety of the Pulse Thulium Fiber Laser Lithotripsy through model Experimental","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe development of flexible ureteroscopy has enabled laser lithotripsy for ureteral and renal calculi, significantly reducing invasive trauma, as demonstrated with Ho:YAG lasers \u003csup\u003e[\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. The pulsed thulium fiber laser (TFL), operating at 1940 nm, is a promising technology which offers advantages over Ho:YAG lasers, including higher pulse rates and improving lithotripsy efficiency \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. However, recent clinical studies raise concerns about its safety profile, reporting a higher incidence of postoperative complications and ureteral strictures comparing to Ho:YAG laser lithotripsy \u003csup\u003e[\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Notably, a study conducted in 2024 found the stricture rate of 11% with manufacturer-preset parameters without improving stone-free rates \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e, this concern has corroborated by other findings \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe mechanisms underlying these tissue injuries is need to be studied. This study aims to investigate the physical principles of TFL lithotripsy, specifically evaluating the thermal and laser radiation damage mechanisms \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. It can guide the control of injury risk and the optimization of laser parameters in lithotripsy\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eThe primary mechanism of TFL lithotripsy involves laser-induced vapor bubble formation and micro-explosions, which generate shockwaves for stone fragmentation \u003csup\u003e[\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. The direct water penetration of 1940 nm laser is minimal (\u0026lt;\u0026thinsp;0.2 mm) because of high absorption in water (129 cm⁻\u0026sup1;). However, with long pulse durations (1\u0026ndash;6 ms), laser can propagate through vapor cavities, potentially reaching surrounding tissues. Nearly all laser energy is deposited as heat, which risks thermal injury to periureteral tissues if it is not dissipated \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. Enhancing lithotripsy efficiency per unit energy can reduce the total energy requirement, thereby reducing the temperature rise. The working process of TFL lithotripsy are intrinsically determined by laser parameters, such as pulse width and peak power density. It is ideal that the laser energy acting on water within or on the surface of the stone is much as possible with suitable parameters.\u003c/p\u003e\u003cp\u003eThe temperature rise of the water environment and the laser radiation in soft tissues through vapor bubbles were identified as primary risk factors for tissue injury. An experimental apparatus was designed to measure the transmission of TFL pulses in water and the associated temperature rise during lithotripsy. The system was utilized to investigate fragmentation patterns under different conditions for the purpose of laser parameter optimization and safety assessment. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the experimental setup included a pulsed TFL source, medical optical fibers and systems for temperature measurement and thermal imaging. The TFL was characterized by the peak power of 800W and continuously adjustable pulse width and repetition rate. Low-hydroxyl medical quartz fibers with core diameters of 400 \u0026micro;m and 600 \u0026micro;m were employed. A thermostatic circulator was used to maintain a constant temperature of the water in the beaker. Temperature signals of the water in the test tube were acquired and recorded using the data acquisition system, while the temperature field distribution was simultaneously monitored using the thermal imaging camera.\u003c/p\u003e\u003cp\u003eArtificial calcium sulfate stone samples were fabricated to evaluate the lithotripsy efficiency and performance under different TFL parameters. The preparation protocol of the samples was as follows: Calcium Sulfate, gypsum powder, and deionized water were mixed at a mass ratio of 1:2:1.5 in a container; the mixture was stirred until homogeneous, then carefully poured into a cubic mold and allowed to solidify, yielding reproducible Calcium Sulfate stone phantoms.\u003c/p\u003e\n\u003cp\u003eEthical Statement: This article does not contain any studies with human participants or animals performed by any of the authors. The use of de-identified human stone samples for this in vitro study was in accordance with the ethical standards of the institution.\u003c/p\u003e"},{"header":"3. Results","content":"\u003cp\u003e3.1 Penetration Depth of TFL Pulses in the water environment\u003c/p\u003e\n\u003cp\u003eThe penetration depth of TFL pulses in water dictates the laser radiation area from the fiber tip. In the experiment, a layer of silicone material was embedded at the base of the beaker to simulate compliant soft tissue. A black light-absorbing material was attached to the silicone surface. The distance from the fiber tip to the aqueous boundary was carefully adjusted. Laser irradiation caused ablation and discoloration of the absorbing material, which was used to determine the laser pulse penetration depth in water. The fibers with the diameters of 400 \u0026mu;m and 600 \u0026mu;m were utilized. The results are presented in Fig.3. For a single TFL pulse at a peak power of 800 W, the penetration depth increased rapidly with increasing pulse width. At a pulse width of 1 ms, the penetration depth for the 600 \u0026mu;m and 400 \u0026mu;m fibers was measured to be 4.23 mm and 5.29 mm respectively. As the pulse width was further increased, the penetration depth increased continuously but the its rate was slow. At a pulse width of 6 ms, the penetration depth reached 7.52 mm and 7.89 mm respectively. It is concluded that the cavitation effect induced by long-duration TFL pulses significantly extends the effective penetration distance in water, it posing a potential threat to the safety of adjacent soft tissues.\u003c/p\u003e\n\u003cp\u003e3.2 Temperature Rise Effects During TFL Lithotripsy Under different Conditions\u003c/p\u003e\n\u003cp\u003eA constant-temperature water environment at 37\u0026deg;C was maintained by means of a bath with recirculating warm water. A 10 mL test tube was immersed in the warm water to simulate the renal pelvis environment during lithotripsy. Irrigation with saline for cooling was administered within the tube using a flow-adjustable micro-peristaltic pump. A temperature probe was positioned approximately 10 mm from the fiber tip to record the water temperature, while the overall temperature field was captured by an infrared camera. At a laser power of 50 W and in the absence of irrigation cooling, the temperature of the water near the fiber tip increased rapidly, reaching 62℃ instantaneously (Fig. 4a). With an irrigation flow rate of 10 mL/min and a laser power of 50 W, the water temperature still kept over 54℃ (Fig. 4b).\u003c/p\u003e\n\u003cp\u003eAt the laser power of 50 W, without irrigation, temperature near the fiber tip rose rapidly, exceeding 60℃ within 10 seconds (Fig. 5), and with irrigation at 10 mL/min, temperature still exceeded 54℃(Fig. 6). The homeostasis temperature surpassed the 43℃ safety threshold at all power, reaching 45℃ at 20 W and 51℃ at 40 W. The water temperature will decline under 40℃ within 3 seconds if the laser stopping.\u003c/p\u003e\n\u003cp\u003eThe experiments shown that the irrigation flow rate was the predominant factor. As shown in Fig.7b, a laser power of 20W required over 30 mL/min irrigation to stabilize near the safety threshold. It could be seen from Fig.7c that a flow rate of 40-50 mL/min was necessary to maintain safe temperatures when the laser was 40W. Fig. 6 shows the temperature rise with different laser powers and an irrigation flow fixed at 10 mL/min. Due to the inherent flow dynamics, temperature fluctuations on the order of 3\u0026deg;C were observed. At this flow rate, a laser power of 10 W elevated the water temperature to the 43\u0026deg;C safety threshold. If the irrigation flow was 50 mL/min, a laser power of 40 W was also found to be operable within safe thermal limits (Fig. 7d). Higher flows increased temperature fluctuations due to enhanced turbulence.\u003c/p\u003e\n\u003cp\u003e3.3 Lithotripsy Efficiency of Pulsed TFL with Different Parameters\u003c/p\u003e\n\u003cp\u003eHuman urinary calculi exhibit substantial heterogeneity in morphology and composition, which complicates the assessment of TFL lithotripsy efficacy, so artificial samples were utilized for studding the efficacy rules in the experiment. Stones were positioned in water within a beaker, and the moving worktable was adjusted to maintain suitable distance of 0.5-1 mm between the stone surface and the fiber tip (Fig. 1). when the worktable was moving the laser beam would scan across the stone surface. Laser lithotripsy was performed for a duration of 1 minute, and the mass of ablated material was quantified using an analytical balance with different parameters. Upon laser irradiation, a substantial quantity of white powder generated instantaneously. Then they dispersed into the surrounding aqueous medium. A portion of the powder was drawn back towards the fiber tip due to recoil effects. With the TFL average power set to 10 W, the pulse width and repetition rate were modulated to measure the lithotripsy efficiency, as shown in Fig. 8. Effective lithotripsy was initiated only when the pulse width exceeded 200 \u0026mu;s (pulse energy of 0.16 J), and the lithotripsy efficiency increased precipitously with the pulse width increasing. For the 400 \u0026mu;m fiber, the lithotripsy efficiency reached a maximum at a pulse width of about 500 \u0026mu;s, being a slight decrease when the pulse width was further increased. The 600 \u0026mu;m fiber exhibited an analogous efficiency trend, but the peak efficiency occurred at a larger pulse width, and it was in the range of 1500-2000 \u0026mu;s. The fragmentation efficiency achieved by using the 400 \u0026mu;m fiber was 18% higher than that obtained with the 600 \u0026mu;m fiber. It is consistent with previous study \u003csup\u003e[24]\u003c/sup\u003e. The TFL lithotripsy physical process is complex and intimately linked to parameters such as pulse width and peak power density.\u003c/p\u003e\n\u003cp\u003eThe ablation morphology of the stones is presented in Fig.9. features indicative of thermal melting and ablation craters would be seen with larger pulse width. In the working process, the initial portion of the laser pulse interacts with water, generating shockwaves which cause mechanical fracture and spallation of the stone. Once the water was displaced, subsequent laser energy was deposited directly into the stone matrix, resulting in thermal ablation.\u003c/p\u003e\n\u003cp\u003eA comparison of lithotripsy speeds at different repetition rates is shown in Fig.10. As the average power was increased, the lithotripsy speed increased rapidly, but the high lithotripsy efficiency appeared with suitable laser parameters. As shown in Fig.10, the lithotripsy efficiency was high under the condition of the repetition rate of 20 Hz and pulse width of 500-1000 \u0026mu;s.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHuman stones frequently exhibit porous structures. Moreover, during clinical lithotripsy, the smaller fragmented particles can be expelled spontaneously through the ureter. Consequently, laser lithotripsy does not invariably produce fine dust. Porous stone samples measuring 10 mm\u003csup\u003e3\u003c/sup\u003e were placed in a mesh bag with 3 mm squares suspended in water (Fig.11). Lithotripsy was performed by guiding the fiber manually. The procedure was deemed complete when all stone fragments had passed through the mesh. The efficiency under this simulation condition was analyzed.\u003c/p\u003e\n\u003cp\u003eUnder the condition of the laser power of 20 W and single pulse energies ranging from 0.15 J to 2 J, the lithotripsy efficiency is plotted in Fig.12. \u0026nbsp;When the single pulse width exceeded 250 \u0026mu;s, further increase in pulse width did not significantly alter the lithotripsy efficiency, which stabilized around 156 mg/min. The fragmentation morphology was predominantly characterized by coarse fragments, with a maximum fragment size of 2.8 mm. If only larger stone fragments were crushed, the crushing efficiency of 1 ms pulse width exceeded 40% than it of 250 \u0026mu;s pulse width. Microscopic examination under different conditions confirmed that no thermal ablation features were produced in porous stones.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe TFL lithotripsy validation experiment was conducted using a porous calcium oxalate human kidney stone sample (Fig.13), and the experimental results followed similar patterns. The pulsed laser frequency was set at 10 Hz in the experiment. The laser pulse width of 500 \u0026mu;s already showed a certain ability to fragment stones, while the laser with 1 ms pulse width had a stronger ability to break larger stones.\u003c/p\u003e\n\u003cp\u003e3.4 Retropulsion and Traction Dynamics in TFL Lithotripsy\u003c/p\u003e\n\u003cp\u003eThe generation and collapse of vapor bubbles during TFL lithotripsy can induce retropulsion and traction forces on the stone. The traction effect can limit the dispersion of larger fragments, facilitating the procedure and mitigating the need for additional anti-retropulsion devices \u003csup\u003e[2]\u003c/sup\u003e. Stone samples (3\u0026times;3\u0026times;3 mm\u0026sup3;) were prepared, and the traction characteristics with different laser parameters were recorded in the experiment. Notable traction was observed only when the pulse energy exceeded 0.3J and the repetition rate was higher than 5 Hz. The most effective traction was achieved within the parameter range of 0.5 J and 40 Hz. However, the stone rotated at the fiber tip when the repetition rate over 30 Hz in the experiment. it makes the laser difficult to align the stone and is unable to effectively break stones in surgery, so during lithotripsy, only selecting appropriate parameters can improve the crushing stones really.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eUreteral mucosal tissue can suffer irreversible damage if exposed to an environment of 45\u0026deg;C for more than 8 minutes, and higher temperatures can cause damage more quickly, leading to complications such as strictures. During stone surgery, the cooling water needs to flow through the gaps of the inserted ureteral sheath and flexible ureteroscope, which imposes significant flow limitations and cannot ensure a consistently unobstructed state. It results in high risk of burns. Based on the experimental results, it can be seen that when perfusion is not smooth, such as the flow rate is less than 10 ml/min, the water temperature rises to above 53\u0026deg;C within 10 seconds with high laser power of 50 W, which can cause significant damage to soft tissues. Synthesis of the data presented in Figs.5 and Figs.6 indicates that TFL lithotripsy with an average output power below 20 W is associated with a relatively high safety margin. If higher power is clinically necessary, the irrigation flow rate must be meticulously monitored during the procedure to ensure that the heat is carried away in time.\u003c/p\u003e\n\u003cp\u003eThe unit energy lithotripsy efficiency is important for surgery and high efficiency can reduce heat deposition effectively and lower the risk of burns. Experimental results show that when using a 400 \u0026mu;m optical fiber, the efficiency of stone pulverization no longer changes significantly with increasing pulse width once the laser pulse width exceeds 300 \u0026mu;s (energy of 0.24 J). The similar patterns are observed in experiments on the particulate fragmentation of porous stone models, but for large stones, the ability of long-pulse-width lasers to break them is significantly enhanced. Additionally, experiments on the dynamics of stone fragmentation show that when the pulse frequency exceeds 30 Hz, small stones, such as size of 3 mm\u003csup\u003e3\u003c/sup\u003e, tend to rotate rapidly around the fiber tip, it making the laser aim at the stone more difficultly and reducing effective fragmentation ability. To ensure the necessary fragmentation speed, the average power cannot be too low, so in actual stone fragmentation procedures, doctors usually prefer to use a relatively long pulse width, typically reaching or exceeding 1 ms. According to the experimental results in Figs.3, the penetration depth of the laser pulse in water exceeds 5 millimeters under this condition. Meanwhile, it is difficult to determine whether it has irradiated soft tissue because of the 1940 nm wavelength laser being invisible in the stone-fragment environment. It is easy to cause radiation damage to the surrounding soft tissues.\u003c/p\u003e\n\u003cp\u003eIn summary, the lithotripsy effect and safety mainly depend on laser parameters, such as pulse width and average power\u003csup\u003e\u0026nbsp;\u003c/sup\u003e\u003csup\u003e[25]\u003c/sup\u003e. In TFL lithotripsy surgery, special attention should be paid to laser radiation and high-temperature damage to surrounding tissues when using high pulse energy and high-power. In terms of parameter optimization, when the stone is large, using high pulse energy can improve lithotripsy efficiency, as the large stone may block the laser and have low laser leakage. When the stone is small, the pulse width should be reduced promptly to ensure safe lithotripsy.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflicts of Interest:\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no conflicts of interest.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e\u003cp\u003eThis work was supported by the project \" Laser Ablation System (No. 2020BED021) \"\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eDr. Haoyong Li provided supervision; Yucheng Yao, Jie Zhou, and Kaizhi Zhang performed the experiments and drafted the main manuscript text; Xiaofeng Zhu, Jianjun Liu, and Hongwei Xiang provided laser technical support and prepared the figures. All authors reviewed the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAndreeva V, Vinarov A, Yaroslavsky I, Kovalenko A, Vybornov A, Rapoport L, Enikeev D, Sorokin N, Dymov A, Tsarichenko D, Glybochko P, Fried N, Traxer O, Altshuler G, Gapontsev V (2020) Preclinical comparison of superpulse thulium fiber laser and a holmium: YAG laser for lithotripsy. World J Urol 38(2):497\u0026ndash;503. https://doi.org/10.1007/s00345-019-02785-9\u003c/li\u003e\n\u003cli\u003eVejdani K, Eisner BH, Pengune W, et al (2009) Effect of laser insult on devices used to prevent stone retropulsion during ureteroscopic lithotripsy. J Endourol 23(4):705\u0026ndash;707. https://doi.org/10.1089/end.2008.0390\u003c/li\u003e\n\u003cli\u003ePanthier F, Chicaud M, Doizi S, et al (2024) How much energy do we need to ablate 1 cubic millimeter of stone during Thulium Fiber Laser lithotripsy? An in vitro study. World J Urol 42:57. https://doi.org/10.1007/s00345-023-04761-w\u003c/li\u003e\n\u003cli\u003eSierra A, Ventimiglia E, Corrales M, et al (2024) A historical comparison of thulium fiber laser systems for stone lithotripsy: navigating toward safe and effective parameters. World J Urol 42:145. https://doi.org/10.1007/s00345-024-04789-6\u003c/li\u003e\n\u003cli\u003eGao X, Zhang HB, Zhang DK, et al (2025) Efficacy and safety of flexible ureteroscopic Ho:YAG lithotripsy for upper urinary tract stones of different sizes and locations. J Clin Surg 33(5):523\u0026ndash;526. https://doi.org/10.3969/j.issn.1005-6483.20241701\u003c/li\u003e\n\u003cli\u003eHein S, Petzold R, Suarez-Ibarrola R, M\u0026uuml;ller PF, Schoenthaler M, Miernik A (2019) Thermal effects of Ho: YAG laser lithotripsy during retrograde intrarenal surgery and percutaneous nephrolithotomy in an ex vivo porcine kidney model. World J Urol. https://doi.org/10.1007/s00345-019-02808-5 \u003c/li\u003e\n\u003cli\u003eRico, L., Blas, L., Ramos, L.B. et al. Thulium Fiber Laser versus Vapor Tunnel HO:YAG laser in retrograde intrarenal surgery: which one has better laser ablation performance?. World J Urol 43, 472 (2025). https://doi.org/10.1007/s00345-025-05852-6\u003c/li\u003e\n\u003cli\u003eJones P, Beisland C, Ulvik \u0026Oslash;, et al (2021) Current status of thulium fibre laser lithotripsy: an up-to-date review. BJU Int 128(5):531\u0026ndash;538. https://doi.org/10.1111/bju.15410\u003c/li\u003e\n\u003cli\u003eXu LW, Yu CH, Hu HY, et al (2023) Comparison of thulium fiber laser lithotripsy and Ho:YAG laser lithotripsy for upper urinary tract stones. Natl Med J China 103(30):2307\u0026ndash;2313\u003c/li\u003e\n\u003cli\u003eAhmad Para S, Saleem Wani M, Hamid A, Ahmad Malik S, Rouf Khawaja A, Mehdi S. Incidence of Ureteric strictures Following Ureteroscopic Laser Lithotripsy: Holmium:YAG Versus Thulium Fiber Laser. Urol Res Pract. 2023 May;49(3):198-204. doi: 10.5152/tud.2023.22264. PMID: 37877870; PMCID: PMC10346094.\u003c/li\u003e\n\u003cli\u003eTang, X., Wu, S., Li, Z. et al. Comparison of Thulium Fiber Laser versus Holmium laser in ureteroscopic lithotripsy: a Meta-analysis and systematic review. BMC Urol 24, 44 (2024). https://doi.org/10.1186/s12894-024-01419-6\u003c/li\u003e\n\u003cli\u003eVillani, R., Liernur, T.D., Windisch, O.L. et al. With great power comes great risk: High ureteral stricture rate after high-power, high-frequency Thulium fiber laser lithotripsy in ureteroscopy. World J Urol 43, 232 (2025). https://doi.org/10.1007/s00345-025-05553-0\u003c/li\u003e\n\u003cli\u003eHyams ES, Monga M, Pearle MS, Antonelli JA, Semins MJ, Assimos DG, et al. A Prospective, Multi-Institutional Study of Flexible Ureteroscopy for Proximal Ureteral Stones Smaller than 2 cm. Journal of Urology [Internet]. 2015 Jan 1 [cited 2025 Sep 10];193(1):165\u0026ndash;9. Available from: https://doi.org/10.1016/j.juro.2014.07.002\u003c/li\u003e\n\u003cli\u003eVogel A, Venugopalan V (2003) Mechanisms of pulsed laser ablation of biological tissues. Chem Rev 103(2):577\u0026ndash;644. https://doi.org/10.1021/cr010379n\u003c/li\u003e\n\u003cli\u003eHe X, et al (2017) Thermal damage threshold of ureteral tissue during laser lithotripsy. Lasers Surg Med 49(5):471\u0026ndash;477. https://doi.org/10.1002/lsm.22625\u003c/li\u003e\n\u003cli\u003eKraft, L., Petzold, R., Suarez-Ibarrola, R. et al. In vitro fragmentation performance of a novel, pulsed Thulium solid-state laser compared to a Thulium fibre laser and standard Ho:YAG laser. Lasers Med Sci 37, 2071\u0026ndash;2078 (2022). https://doi.org/10.1007/s10103-021-03495-8\u003c/li\u003e\n\u003cli\u003eWollin DA, et al (2021) In vivo porcine evaluation of ureteral thermal injury thresholds during laser lithotripsy. 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J Mod Urol 28(11):993\u0026ndash;997\u003c/li\u003e\n\u003cli\u003eTonyali, S., von Bargen, M.F., Ozkan, A. et al. The heat is on: the impact of excessive temperature increments on complications of laser treatment for ureteral and renal stones. World J Urol 41, 3853\u0026ndash;3865 (2023). https://doi.org/10.1007/s00345-023-04652-0 \u003c/li\u003e\n\u003cli\u003eHardy LA, Wilson CR, Irby PB, Fried NM (2014) Thulium fiber laser lithotripsy in an in vitro ureter model. J Biomed Opt 19(12):1280014\u003c/li\u003e\n\u003cli\u003eDymov A, Glybochko P, Alyaev Y, Vinarov A, Altshuler G, Zamyatina V, Sorokin N, Enikeev D, Lekarev V, Proskura A et al (2017) Thulium lithotripsy: from experiment to clinical practice. J Urol 197(4):e1285\u003c/li\u003e\n\u003cli\u003eLi, Z., Wu, S., Liu, T. et al. Optimal parameter settings of thulium fiber laser for ureteral stone lithotripsy: a comparative study in two different testing environments. Urolithiasis 52, 78 (2024). https://doi.org/10.1007/s00240-024-01585-0\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"thulium fiber laser lithotripsy, thermal injury, penetration depth, clinical safety","lastPublishedDoi":"10.21203/rs.3.rs-7798044/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7798044/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e\u003cp\u003eThis study aims to investigate the physical interaction characteristics of thulium fiber laser (TFL) lithotripsy, to elucidate the influence of laser parameters on stone ablation efficiency and clinical safety, and thereby to guide the clinical application.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eThe experiment was established to investigate the laws of laser penetration depth and environmental water temperature rise under different condition. The potential for radiation and thermal damage to surrounding tissues was analyzed based on these laws. Concurrently, lithotripsy efficiency of different laser parameters was investigated by experiment.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThe laser penetration depth exceeding 5 mm in water if the long pulse width is over 1 ms, which poses a risk of radiative damage to surrounding tissues. When the TFL average power exceeds 30 W with insufficient irrigation its rate being lower than 40 mL/min, a rapid temperature rise surpassing 47℃ occurs and creating a risk of thermal injury to adjacent tissues. Furthermore, a pulse width greater than 500 \u0026micro;s is generally required to achieve high lithotripsy efficiency.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eThe lithotripsy efficiency of TFL is directly influenced by pulse width and power. However, since both long pulse widths and high average power can pose risks of damage to surrounding tissues, parameter optimization is important during TFL procedures.\u003c/p\u003e","manuscriptTitle":"Research on the Efficiency and Safety of the Pulse Thulium Fiber Laser Lithotripsy through model Experimental","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-11 09:43:51","doi":"10.21203/rs.3.rs-7798044/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0b4a0883-902a-4c70-8a6f-ed3531646ab9","owner":[],"postedDate":"November 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-05T20:54:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-11 09:43:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7798044","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7798044","identity":"rs-7798044","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}