Working Channel Of Ureteroscope Research Articles

Clinical Evaluation of Miniature Flexible Scope for Diagnosis of Ureteroscope Working Channel Defects.

Introduction: To evaluate flexible ureteroscope working channels with a 1.06 mm digital borescope (Clarus Medical, Minneapolis, MN) and identify factors contributing to ureteroscope damage over time. Materials and Methods: We performed a single institutional prospective study of patients undergoing stone surgery using a nondisposable flexible ureteroscope. A 1.06 mm borescope was used to evaluate ureteroscopes before and after surgery. Borescope videos were reviewed by two independent researchers to quantify average pre- and postprocedural damage. Results: Twenty-five procedures were performed with pre- and postprocedural borescope assessment between August 2021 and February 2022. All patients received preoperative CT imaging depicting a mean axial stone size of 14.1 ± 8.4 mm and density of 923.4 ± 458.1 HU. Mean operative time was 63.8 ± 34.0 minutes. The average number an instrument passes through the working channel was 2.1 ± 1.6. Laser was used in 11 cases with mean laser time of 18.8 ± 19.7 minutes and mean total energy of 5.8 ± 4.2 KJ. On preoperative assessment, all ureteroscopes had some form of defect (24% shave, 32% pinhole, 96% dents and scratches, and 28% discolorations). During postoperative assessment, 23/25 (92%) ureteroscopes showed additional damage with an average of 3.7 ± 2.8 imperfections acquired after one use. Significant differences were seen in acquired shavings (p = 0.028) and scratches or dents (p = 0.018). Of the 355 imperfections seen on postoperative evaluation, 0.4% were shave, 3% were pinhole, 85.8% were dents and scratches, and 10.8% were discolorations. Conclusion: The Clarus borescope observed defects after the majority of flexible ureteroscopy procedures for nephrolithiasis. Although such disruptions may not immediately render ureteroscopes nonfunctional, they are more common than previously described and could increase maintenance costs. Further studies are needed to investigate the burden of unit damage per procedure to raise operator awareness and reduce preventable ureteroscope imperfections.

SC47 - Clinical evaluation of miniature flexible scope for diagnosis of ureteroscope working channel defects

SC47 - Clinical evaluation of miniature flexible scope for diagnosis of ureteroscope working channel defects

Thulium Fiber Laser's Dust for Stone Composition Analysis: Is It Enough? A Pilot Study.

Introduction: We aimed to evaluate if the biochemical composition of urinary stones can be determined by analyzing the stone dust only, and whether a photo taken during the surgery could be useful for completing the morpho-constitutional analysis. Materials and Methods: Twenty patients went through a retrograde intrarenal surgery for renal stone treatment with thulium fiber laser (Fiber Dust; Quanta, 2020) using 150 μm silica core laser fibers. After laser lithotripsy, residual fragments (RF) were removed with a basket (ZeroTip; Boston Scientific) and spontaneously floating stones particles were considered stone dust and were aspirated through the working channel. Pairs of RF and stone dust were labeled and sent to analysis by scanning electron microscopy and Fourier transform infrared spectroscopy. Photos of the stone (surface and section) were taken from videos recorded during the surgery. Results: A total of 20 patients were included in this study. Mean age was 49.8 years with metabolic and genetic disorders. Mean stone volume was 750 mm3 for ureteral stones and 2334 mm3 for renal stones. Mean stone density was 1187 HU. Positive urine culture was found in 25% patients. In 2/20 (10%), the biochemistry differed only in the relative proportions of each constituent, while in 5/20 (25%), only one component was missing. Laser crystalline conversion was found in 3/20 (15%). Whewellite and weddellite layers were found in photos, thus adding missing information from dust stone analysis. Conclusion: By analyzing aspirated dust through the ureteroscope's working channel with physical techniques, we can understand the lithogenic process of the urinary stone, without needing to analyze the stone fragment. Morphologic analysis, given by a proper stone picture, adds missing information in specific cases.

An irrigation system for noninvasively estimating intrarenal pressure during flexible ureteroscopy.

High intrarenal pressure (IRP) during flexible ureteroscopy (FURS) may lead to severe complications. Reported methods for measuring IRP are often inconvenient to use, expensive and involve instruments that occupy the narrow ureter. We proposed an irrigation system, which can noninvasively estimate IRP based on the principle of fluid mechanics. To determine the feasibility of our system, we conducted irrigation experiments on a kidney phantom and a porcine kidney. The estimated IRPs were compared with the ground truth IRPs. When no surgical instrument was inserted into the flexible ureteroscope's working channel, our system can estimate IRP with high accuracy. When a surgical instrument was inserted, our system can approximately estimate the level of IRP. Our proposed irrigation system can noninvasively estimate IRP, presenting a new thought for clinical practice. In future studies, in vivo experiments are needed to further validate and improve the system.

Simulations and testing of the mechanical properties of small core optical fibers for ureteroscopy

Thulium fiber laser (TFL) lithotripsy has recently been introduced for clinical use. Previous TFL laboratory studies demonstrated high-power delivery through small (50- to 150-μm core) optical fibers. This preliminary study simulates forces on fibers during insertion into a flexible ureteroscope and determines mechanical feasibility of small fibers for a clinical setting. Simulations were conducted with commercially available fiber (core/cladding) sizes of 50/70, 72/108, 100/140, 150/165, 150/180, and 200 / 240 μm. Solidworks software integrating Euler’s buckling equation was used to calculate fiber buckling thresholds as a function of typical manual forces (0.15 to 2.0 N) applied near the proximal end of a ureteroscope. Forces on fibers were modeled assuming support from saline flow and resistance by the working channel wall. Simulation results were categorized based on force values previously reported in the literature, with smaller forces (<0.4 to 0.8 N) buckling fibers, mid-range forces (0.8 to 1.6 N) optimal for fiber manipulation, and higher forces (>1.6 to 2.0 N) at risk of damaging the ureteroscope working channel. Fiber sizes were simulated with two different types of holdings on each end to find a range of possible values that most closely simulate clinical behavior. Simulation results were confirmed using a force meter and a benchtop experimental setup. Numerical simulations predicted that optical fibers for TFL lithotripsy should be equal to or larger than 150 / 190 μm (core/cladding), for effective manual manipulation within flexible ureteroscopes.

Characterization of intracalyceal pressure during ureteroscopy.

To provide the first report of measuring intracalyceal pressures during ureteroscopy (URS). A prospective single-center clinical study using a cardiac pressure guidewire to measure intracalyceal pressure during flexible URS was performed. Eight patients (45 calyces) undergoing URS for nephrolithiasis were included. A Verrata® pressure guide wire was passed through the working channel of a dual lumen flexible ureteroscope and into the calyces while irrigation was maintained at 150mmHg. Pressure was measured in the renal pelvis, upper pole, interpolar, and lower pole calyces both with and without a ureteral access sheath (UAS). The pressure in each location with and without a UAS was compared. The correlation between calyceal pressure and infundibular dimensions (width, length) was determined. Intracalyceal pressure was significantly lower in each region when a UAS was used. Compared to patients with a 12/14Fr UAS, those with a 14/16Fr UAS had significantly lower pressure in the interpolar (25.3 ± 13.1 vs. 44.0 ± 27.5mmHg, p = 0.03) and lower pole (16.2 ± 3.5 vs. 49.2 ± 40.3mmHg, p = 0.004) calyces. Interpolar calyceal pressure in the presence of a UAS was significantly higher than the renal pelvis pressure (RPP) (30.8 ± 19.6 vs. 17.9 ± 11.0mmHg, p = 0.004). During flexible URS, RPP strongly correlates with, but does not uniformly represent, the intracalyceal pressure. With a 14/16Fr UAS and an inflow pressure of 150mmHg, RPP and intracalyceal pressure never exceed the threshold for renal backflow.

Fluoroscopy-free double-J stent placement through ureteroscope working channel postuncomplicated ureteroscopic laser lithotripsy: A novel technique.

Objectives:To report a technique for ureteroscopic laser lithotripsy (URSL) and retrograde placement of a double-J (DJ) stenting through the ureteroscope working channel without the use of a fluoroscope compared to the conventional technique.Patients and Methods:Between June 2015 and December 2017, 170 patients selected for URSL for treatment of ureteral stones and DJ insertion was evaluated. Patients are divided into two groups according to the use of fluoroscopy. In Group A (100 patients), fluoroscope is used and group B (70 patients) without fluoroscopy guidance. In group B, URSL is performed first and followed by DJ insertion by the semi-rigid ureteroscope 8.5-11 Fr under vision without fluoroscopy.Results:Stone free rate in 96% versus 94.3% for groups A and B respectively. This technique was successful in all the included patients: 166 retrograde DJ stenting post URSL for ureteric calculi and 4 cases for anuria. Group A are exposed to radiation with mean 26.6 seconds in URSL procedure and 4.8 seconds for DJ stenting. Group B was exposed to zero dose. For group A, the stents size was 6 Fr for 70% of patients and 15 % for 4.7 Fr and 15% for 7 Fr stenting. In Group B, stents of 4.7 Fr and length 24-26 cm were used in all patients. Failure of DJ insertion is reported in 9% for group A and 13 (18.5%) patients for group B.Conclusions:This study report the feasibility and efficacy of the completely fluoroscopy free URSL and DJ stenting to treat ureteric stones.

18] Fluoroscopy free JJ stent placement through ureteroscope working channel after uncomplicated ureteroscopic laser lithotripsy: A novel technique

ObjectiveTo report a technique for ureteroscopic laser lithotripsy (URSL) and retrograde placement of a JJ stent through the ureteroscope working channel without the use of a fluoroscope compared to the conventional technique.

Extraction of trapped double J in ureteroscope: a novel technique.

Urological endoscopes and percutaneous devices are expensive and their maintenance and cleaning need special attention. Sometimes urologists can help repairing their devices. During taking out a Double J, Double J was trapped in the working channel of ureteroscope unintentionally. It was not possible to take it out by pushing methods. Finally, Double J was pulled out by a changed nephrostomy needle to a small curve hook. Using the hand-made hook to pull out a trapped Double J from ureteroscope does not destroy the device.

Fluid Dynamic Analysis of Hand-Pump Infuser and UROMAT Endoscopic Automatic System for Irrigation Through a Flexible Ureteroscope.

To evaluate the flow characteristics produced by a manual and automated-pump irrigation system connected to a flexible ureteroscope. An in vitro analysis of a manual hand-pump infuser (HP) and the UROMAT Endoscopic Automatic System for Irrigation® (E.A.S.I.) pump was performed. Standard irrigation tubing was used to connect a three-way valve to a flexible ureteroscope, the irrigation system, and a digital manometer. Flow rate and irrigation pressure measurements were recorded over a 15-minute period using pressure settings of 150 and 200 mm Hg for both irrigation pump systems. Once the HP was inflated to the initial pressure, it was not reinflated over the course of the trial. Data were collected with the working channel unoccupied and with placement of a 200 μm (0.6F) holmium laser fiber, 1.7F nitinol stone retrieval basket, or 2.67F guidewire. The difference in pressure measured at the site of inflow of irrigation to the ureteroscope was significantly greater using the HP compared to the E.A.S.I. pump at pressure settings of 150 mm Hg with and without the use of ureteroscopic instrumentation (p < 0.001), and at 200 mm Hg with instrumentation in the working channel (p < 0.01). There was no significant difference in the flow rate of irrigation through the open-channel ureteroscope over the course of 5 minutes between the two pump systems. The flow rates of irrigation produced by the HP and the E.A.S.I. pump are similar at pressures of 150 and 200 mm Hg irrespective of the occupancy of a ureteroscope's working channel during the first 5-minutes of irrigation. Irrigation pressure at the entry site of the ureteroscope is subject to significant variability with use of the HP compared to the E.A.S.I. pump irrigation system.

Thermal Response to High-Power Holmium Laser Lithotripsy.

The aim of this study was to investigate "caliceal" fluid temperature changes during holmium laser activation/lithotripsy using settings up to 40 W power output with different irrigation flow rates. The experimental system consisted of a glass test tube (diameter 10 mm/length 75 mm) filled with deionized water, to mimic a calix. Real-time temperature was recorded using a thermocouple (Physitemp, NJ) positioned 5 mm from the bottom of the tube. A 200 μm laser fiber (Flexiva; Boston Scientific, MA) was introduced through the working channel of a disposable ureteroscope (LithoVue; Boston Scientific) and the laser fiber tip was positioned 15 mm above the bottom of the test tube. Deionized water irrigation (room temperature) through the working channel of the ureteroscope was delivered at flow rates of 0, 7-8, 14-15, and 38-40 mL/minute. A 120-W holmium laser (pulse 120; Lumenis, CA) was used. The following settings were explored: 0.5 J × 10 Hz, 1.0 J × 10 Hz, 0.5 J × 20 Hz, 1.0 J × 20 Hz, 0.5 J × 40 Hz, 1.0 J × 40 Hz, and 0.5 J × 80 Hz. During each experiment, the laser was activated continuously for 60 seconds. Temperature increased with increasing laser power output and decreasing irrigation flow rate. The highest temperature, 70.3°C (standard deviation 2.7), occurred with laser setting of 1.0 J × 40 Hz and no irrigation after 60 seconds of continuous laser firing. None of the tested laser settings and irrigation parameters produced temperature exceeding 51°C when activated for only 10 seconds of continuous laser firing. High-power holmium settings fired in long bursts with low irrigation flow rates can generate high fluid temperatures in a laboratory "caliceal" model. Awareness of this risk allows urologist to implement a variety of techniques (higher irrigation flow rates, intermittent laser activation, and potentially cooled irrigation fluid) to control and mitigate thermal effects during holmium laser lithotripsy.

Defining the Costs of Reusable Flexible Ureteroscope Reprocessing Using Time-Driven Activity-Based Costing.

Careful decontamination and sterilization of reusable flexible ureteroscopes used in ureterorenoscopy cases prevent the spread of infectious pathogens to patients and technicians. However, inefficient reprocessing and unavailability of ureteroscopes sent out for repair can contribute to expensive operating room (OR) delays. Time-driven activity-based costing (TDABC) was applied to describe the time and costs involved in reprocessing. Direct observation and timing were performed for all steps in reprocessing of reusable flexible ureteroscopes following operative procedures. Estimated times needed for each step by which damaged ureteroscopes identified during reprocessing are sent for repair were characterized through interviews with purchasing analyst staff. Process maps were created for reprocessing and repair detailing individual step times and their variances. Cost data for labor and disposables used were applied to calculate per minute and average step costs. Ten ureteroscopes were followed through reprocessing. Process mapping for ureteroscope reprocessing averaged 229.0 ± 74.4 minutes, whereas sending a ureteroscope for repair required an estimated 143 minutes per repair. Most steps demonstrated low variance between timed observations. Ureteroscope drying was the longest and highest variance step at 126.5 ± 55.7 minutes and was highly dependent on manual air flushing through the ureteroscope working channel and ureteroscope positioning in the drying cabinet. Total costs for reprocessing totaled $96.13 per episode, including the cost of labor and disposable items. Utilizing TDABC delineates the full spectrum of costs associated with ureteroscope reprocessing and identifies areas for process improvement to drive value-based care. At our institution, ureteroscope drying was one clearly identified target area. Implementing training in ureteroscope drying technique could save up to 2 hours per reprocessing event, potentially preventing expensive OR delays.

Elevated Renal Pelvic Pressures during Percutaneous Nephrolithotomy Risk Higher Postoperative Pain and Longer Hospital Stay.

Renal pelvic pressure may vary during percutaneous nephrolithotomy. We sought to determine the relationship of postoperative pain to endoscope caliber, renal pelvic pressure and hospital stay. We reviewed the records of 20 percutaneous nephrolithotomies done under ureteroscopic guidance with renal pelvic pressure monitoring. The ureteroscope working channel was connected to a pressure transducer and used to determine renal pelvic pressure at baseline, when irrigating with a 26Fr rigid nephroscope and a 16Fr flexible nephroscope, and during suction. Patient demographics, operative characteristics, Likert pain scores and length of hospital stay were compared as stratified by average renal pelvic pressure. The Mann-Whitney U and Fisher exact tests were used with p<0.05 considered significant. A total of 220 measurements were recorded in 20 patients undergoing single access percutaneous nephrolithotomy. Mean patient age was 55.2 years (range 20 to 77) and mean body mass index was 32.4 kg/m2 (range 18 to 53.3). Rigid nephroscopy resulted in significantly higher average renal pelvic pressure than flexible nephroscopy (30.3 vs 12.9 mm Hg, p = 0.007). Average renal pelvicpressure was 30 mm Hg or greater in 7 patients (35%) undergoing rigid nephroscopy and in none (0%) undergoing flexible nephroscopy (p <0.01). Patients exposed to an average renal pelvic pressure of 30 mm Hg or greater during rigid nephroscopy had significantly higher average pain scores (p = 0.004) and longer hospital stays (p = 0.04) than patients with renal pelvic pressure less than 30 mm Hg. Average renal pelvic pressure 30 mm Hg or greater during rigid nephroscopy was also associated with a longer skin to calyx distance (105.5 vs 79.7 mm, p = 0.03). Knowledge of the factors that influence renal pelvic pressure and methods to control pressure extremes may improve patient outcomes during percutaneous nephrolithotomy.

Fiber optic muzzle brake tip for reducing fiber burnback and stone retropulsion during thulium fiber laser lithotripsy.

The experimental thulium fiber laser (TFL) is being explored as an alternative to the current clinical gold standard Holmium:YAG laser for lithotripsy. The near single-mode TFL beam allows coupling of higher power into smaller optical fibers than the multimode Holmium laser beam profile, without proximal fiber tip degradation. A smaller fiber is desirable because it provides more space in the ureteroscope working channel for increased saline irrigation rates and allows maximum ureteroscope deflection. However, distal fiber tip burnback increases as fiber diameter decreases. Previous studies utilizing hollow steel sheaths around recessed distal fiber tips reduced fiber burnback but increased stone retropulsion. A “fiber muzzle brake” was tested for reducing both fiber burnback and stone retropulsion by manipulating vapor bubble expansion. TFL lithotripsy studies were performed at 1908 nm, 35 mJ, 500 ?? ? s , and 300 Hz using a 100 - ? m -core fiber. The optimal stainless steel muzzle brake tip tested consisted of a 1-cm-long, 560 - ? m -outer-diameter, 360 - ? m -inner-diameter tube with a 275 - ? m -diameter through hole located 250 ?? ? m from the distal end. The fiber tip was recessed a distance of 500 ?? ? m . Stone phantom retropulsion, fiber tip burnback, and calcium oxalate stone ablation studies were performed ex vivo. Small stones with a mass of 40 ± 4 ?? mg and 4-mm-diameter were ablated over a 1.5-mm sieve in 25 ± 4 ?? s

Miniature ball-tip optical fibers for use in thulium fiber laser ablation of kidney stones.

Optical fibers, consisting of 240-μm-core trunk fibers with rounded, 450-μm-diameter ball tips, are currently used during Holmium:YAG laser lithotripsy to reduce mechanical damage to the inner lining of the ureteroscope working channel during fiber insertion and prolong ureteroscope lifetime. Similarly, this study tests a smaller, 100-μm-core fiber with 300-μm-diameter ball tip during thulium fiber laser (TFL) lithotripsy. TFL was operated at a wavelength of 1908 nm, with 35-mJ pulse energy, 500-μs pulse duration, and 300-Hz pulse rate. Calcium oxalate/phosphate stone samples were weighed, laser procedure times were measured, and ablation rates were calculated for ball tip fibers, with comparison to bare tip fibers. Photographs of ball tips were taken before and after each procedure to track ball tip degradation and determine number of procedures completed before need for replacement. A high speed camera also recorded the cavitation bubble dynamics during TFL lithotripsy. Additionally, saline irrigation rates and ureteroscope deflection were measured with and without the presence of TFL fiber. There was no statistical difference (P>0.05) between stone ablation rates for single-use ball tip fiber (1.3±0.4 mg/s) (n=10), multiple-use ball tip fiber (1.3±0.5 mg/s) (n=44), and conventional single-use bare tip fibers (1.3±0.2 mg/s) (n=10). Ball tip durability varied widely, but fibers averaged greater than four stone procedures before failure, defined by rapid decline in stone ablation rates. Mechanical damage at the front surface of the ball tip was the limiting factor in fiber lifetime. The small fiber diameter did not significantly impact ureteroscope deflection or saline flow rates. The miniature ball tip fiber may provide a cost-effective design for safe fiber insertion through the ureteroscope working channel and into the ureter without risk of instrument damage or tissue perforation, and without compromising stone ablation efficiency during TFL lithotripsy.

Evaluation of Novel Ball-Tip Holmium Laser Fiber: Impact on Ureteroscope Performance and Fragmentation Efficiency

A novel ball tip (BT) holmium laser fiber has recently been developed, which features a modified rounded tip. The modification is purported to aid in insertion and minimize damage to the ureteroscope working channel. We evaluated this laser fiber with regard to stone comminution, tip degradation, insertional force into the ureteroscope, and impact on ureteroscope deflection. A 242 μm BT fiber and a standard flat tip (SF) fiber were compared. Four kilojoules was delivered to a BegoStone over a constant surface area using settings of 0.2/50, 0.6/6, 0.8/8, and 1 J/10 Hz. Fiber tip degradation was measured at 1 and 4 kJ. Ureteroscope deflection was measured with the Olympus URF-P5, URF-P6, and URF-V. Insertion force into a 270° angled ureteroscope sheath model was measured. A sample size of five fibers was used for each comminution energy setting. Comminution increased with pulse energy without significant difference between fibers. No significant differences in tip degradation were observed. Both fibers reduced deflection (10°-30°) in all ureteroscopes without significant differences between fibers. Four new fibers paired with new sheath models were used to test insertion force. The BT insertion forces were approximately one-third of the SF. One SF fiber caused significant damage to the sheath and could not be advanced completely. The BT fiber has comparable comminution, tip degradation, and ureteroscope deflection performance compared with the SF fiber while exhibiting reduced insertion force within an aggressively deflected working sheath. The new tip design is likely protective of the working channel without loss of performance.

A Pilot Study of In Vivo Confocal Laser Endomicroscopy of Upper Tract Urothelial Carcinoma.

Tissue diagnosis of upper tract urothelial carcinoma (UTUC) is limited by variance in tumor sampling by standard ureteroscopic biopsy. Optical imaging technologies can potentially improve UTUC diagnosis, surveillance, and endoscopic treatment. We previously demonstrated in vivo optical biopsy of urothelial carcinoma of the bladder using confocal laser endomicroscopy (CLE). In this study, we evaluated a new 0.85-mm imaging probe in the upper urinary tract and demonstrated feasibility and compatibility with standard ureteroscopes to achieve in vivo optical biopsy of UTUC. Fourteen patients scheduled for ureteroscopy of suspected upper tract lesions or surveillance of UTUC were recruited. After intravenous (IV) administration of fluorescein, CLE was performed using a 0.85-mm-diameter imaging probe inserted through the working channel of standard ureteroscopes. Acquired confocal video sequences were reviewed and analyzed. A mosaicing algorithm was used to compile a series of images into a single larger composite image. Processed CLE images were compared with standard histopathologic analysis. Optical biopsy of the UTUC using CLE was effectively achieved during standard ureteroscopy. There were no adverse events related to IV fluorescein administration or image acquisition. Confocal imaging of UTUC showed characteristic features similar to urothelial carcinoma of the bladder, including papillary structure, fibrovascular stalks, and pleomorphism. Lamina propria in normal areas of the renal pelvis and ureter was also identified. We report an initial feasibility of CLE of UTUC. Pending further clinical investigation, CLE may become a useful adjunct to ureteroscopic biopsy, endoscopic ablation, and surveillance of UTUC.

A Miniaturized, 1.9F Integrated Optical Fiber and Stone Basket for Use in Thulium Fiber Laser Lithotripsy.

The thulium fiber laser (TFL) is being explored as an alternative laser lithotripter to the standard holmium:yttrium-aluminum-garnet laser. The more uniform beam profile of the TFL enables higher power transmission through smaller fibers. In this study, a 100-μm core, 140-μm outer-diameter (OD) silica fiber with 5-mm length hollow steel tip was integrated with 1.3F (0.433-mm OD) nitinol wire basket to form a 1.9F (0.633-mm OD) device. TFL energy of 30 mJ, 500 μs pulse duration, and 500 Hz pulse rate was delivered to human uric acid stones, ex vivo. Stone ablation rates measured 1.5 ± 0.2 mg/s, comparable to 1.7 ± 0.3 mg/s using bare fiber tips separately with stone basket. With further development, this device may minimize stone retropulsion, allowing more efficient TFL lithotripsy at higher pulse rates. It may also provide increased flexibility, higher saline irrigation rates through the ureteroscope working channel, reduce fiber degradation compared with separate fiber and basket manipulation, and reduce laser-induced nitinol wire damage.

Thulium fiber laser ablation of kidney stones using a 50-μm-core silica optical fiber

Our laboratory is currently studying the experimental thulium fiber laser (TFL) as a potential alternative laser lithotripter to the gold standard, clinical Holmium:YAG laser. We have previously demonstrated the efficient coupling of TFL energy into fibers as small as 100-μm-core-diameter without damage to the proximal end. Although smaller fibers have a greater tendency to degrade at the distal tip during lithotripsy, fiber diameters (≤200 μm) have been shown to increase the saline irrigation rates through the working channel of a flexible ureteroscope, to maximize the ureteroscope deflection, and to reduce the stone retropulsion during laser lithotripsy. In this study, a 50-μm-core-diameter, 85-μm-outer-diameter, low-OH silica fiber is characterized for TFL ablation of human calcium oxalate monohydrate urinary stones, ex vivo. The 50-μm-core fiber consumes approximately 30 times less cross-sectional area inside the single working channel of a ureteroscope than the standard 270-μm-core fiber currently used in the clinic. The ureteroscope working channel flow rate, including the 50-μm fiber, decreased by only 10% with no impairment of ureteroscope deflection. The fiber delivered up to 15.4±5.9 W under extreme bending (5-mm-radius) conditions. The stone ablation rate measured 70±22 μg/s for 35-mJ-pulse-energy, 500-μs-pulse-duration, and 50-Hz-pulse-rate. Stone retropulsion and fiber burnback averaged 201±336 and 3000±2600 μm, respectively, after 2 min. With further development, thulium fiber laser lithotripsy using ultra-small, 50-μm-core fibers may introduce new integration and miniaturization possibilities and potentially provide an alternative to conventional Holmium:YAG laser lithotripsy using larger fibers.

Fiber-optic manipulation of urinary stone phantoms using holmium:YAG and thulium fiber lasers

Fiber-optic attraction of urinary stones during laser lithotripsy may be exploited to manipulate stone fragments inside the urinary tract without mechanical grasping tools, saving the urologist time and space in the ureteroscope working channel. We compare thulium fiber laser (TFL) high pulse rate/low pulse energy operation to conventional holmium:YAG low pulse rate/high pulse energy operation for fiber-optic suctioning of plaster-of-paris (PoP) stone phantoms. A TFL (wavelength of 1908 nm, pulse energy of 35 mJ, pulse duration of 500 μs, and pulse rate of 10 to 350 Hz) and a holmium laser (wavelength of 2120 nm, pulse energy of 35 to 360 mJ, pulse duration of 300 μs, and pulse rate of 20 Hz) were tested using 270-μm-core optical fibers. A peak drag speed of ~2.5 mm/s was measured for both TFL (35 mJ and 150 to 250 Hz) and holmium laser (210 mJ and 20 Hz). Particle image velocimetry and thermal imaging were used to track water flow for all parameters. Fiber-optic suctioning of urinary stone phantoms is feasible. TFL operation at high pulse rates/low pulse energies is preferable to holmium operation at low pulse rates/high pulse energies for rapid and smooth stone pulling. With further development, this novel technique may be useful for manipulating stone fragments in the urinary tract.