Search

Introduction and Objectives: We sought to compare the effectiveness and efficiency of the superpulse thulium fiber laser (sTFL to the holmium: yttrium–aluminum–garnet [Ho:YAG] laser for ureteroscopic "dusting" of implanted renal stones in an in vivo porcine model. Methods: Twenty-four porcine kidneys (12 juvenile female Yorkshire pigs) were randomized to Ho:YAG or sTFL treatment groups. Canine calcium oxalate stones were scanned with computed tomography to calculate stone volume and stone density; the stones were randomized and implanted into each renal pelvis via an open pyelotomy. In all trials, a 14F, 35 cm ureteral access sheath was placed. With a 9.9F dual lumen flexible ureteroscope, laser lithotripsy was performed using dusting settings: Ho:YAG 200 μm laser fiber at 16 W (0.4 J, 40 Hz) or sTFL 200 μm laser fiber at 16 W (0.2 J, 80 Hz). Lithotripsy continued until no fragments over 1 mm were observed. No stone basketing was performed. Throughout the procedures, intrarenal and renal pelvis temperatures were measured using two percutaneously positioned K-type thermocouples, one in the upper pole calyx and one in the renal pelvis. After the lithotripsy, the ureteropelvic junction was occluded, the kidneys were bivalved, and all residual fragments were collected, dried, weighed, and then measured with an optical laser particle sizer. Results: Implanted stones were similar in volume and density in both groups. Intraoperative collecting system temperatures were similar for both groups (all <44°C). Compared to Ho:YAG, sTFL ablated stones faster (9 vs 27 minutes, p < 0.001) with less energy expenditure (8 vs 26 kJ, p < 0.001), and a greater stone clearance rate (73% vs 45%, p = 0.001). After sTFL lithotripsy, 77% of the remaining fragments were ≤1 mm vs 17% of fragments ≤1 mm after Ho:YAG treatment (p < 0.001). Conclusions: In an in vivo porcine kidney, using dusting settings, sTFL lithotripsy resulted in shorter ablation times, higher stone clearance rates, and markedly smaller stone fragments than Ho:YAG lithotripsy. [ABSTRACT FROM AUTHOR]

We monitor the up-converted fluorescence from the pumped distributed-feedback (DFB) fiber laser in Erbium-doped fiber to find the intra-cavity power distribution. The intense spatial hole burning (SHB) effect in uniform DFB fiber laser is investigated theoretically and experimentally. For the laser performance optimization, we employ the phase-shifted grating apodization to suppress the SHB effect. Through the proposed apodization structure, the effective reduction in SHB of the DFB fiber laser is achieved. [ABSTRACT FROM AUTHOR]

An all-single-mode fiber intracavity displacement sensor based on U-shaped single-mode fiber interferometer (U-SMFI) is demonstrated theoretically and experimentally. The theoretical model for a cavity-loss-modulated Er-doped fiber ring laser is proposed to analyze the linewidth-narrowing and signal-to-noise ratio (SNR) enhancement mechanism. The evolutionary process of the spectra is calculated through solving the rate equations to investigate the role that the intracavity spectroscopy plays in narrowing the linewidth and reducing the bandwidth-broadening effect theoretically for the first time. Experimental setup for intracavity displacement sensing via a U-SMFI is established to verify the above principle. According to the experimental results, the linewidth and SNR characteristics have been improved a lot compared with the passive U-SMFI. Moreover, it is indicated that the sensitivity of the intracavity displacement-sensor can be optimized through adjusting the bending radius of the U-SMFI. The mode-hopping phenomenon is investigated and eliminated to make the wavelength stability of the output laser comparable to the highest resolution of the optical spectrum analyzer. When the displacement applied to the U-SMFI with a radius of 5.95 mm is changed from 0 to 200 μm, the sensitivity of the proposed intracavity-sensor is 52.92 pm/μm, which can be enhanced through a further optimization to the radius of the U-SMFI. Our proposed sensor design is expected to emerge as a new and promising alternative approach to achieve high-resolution displacement sensor. [ABSTRACT FROM AUTHOR]

Introduction and Objectives: Conventional renal stone dusting is challenging; the holmium (Ho:YAG) laser and holmium with MOSES effect (Ho:YAG-MOSES) fail to uniformly produce fragments ≤100 μm (i.e., dust). The superpulse thulium fiber laser (sTFL) may more effectively render uroliths into "dust," and may thus improve stone-free rates. Accordingly, we performed ex vivo evaluations with all three laser modalities, assessing stone fragments and stone clearance. Methods: Seventy-two ex vivo porcine kidney-ureter models were divided into 12 groups of 6: laser type (Ho:YAG, Ho:YAG-MOSES, sTFL), ureteroscope with and without applied suction, and the presence or absence of a 14F ureteral access sheath (UAS). Calcium oxalate stones were preweighed and implanted into each kidney via a pyelotomy. Stones were treated at 16W using dusting settings of 0.4J × 40Hz (Ho:YAG), 0.2J × 80Hz (Ho:YAG-MOSES), and 0.2J × 80Hz (sTFL) for up to 20 minutes. No stone basketing was performed. Kidneys were bivalved and residual fragments were collected, dried, weighed, and sieved to determine fragment size and stone clearance. Results: Initial stone mass (mg), procedure time (seconds), and laser energy expenditure (kJ) were similar in all 12 groups. The greatest stone clearance was seen with sTFL + suction + UAS (94%) compared with a conventional technique (Ho:YAG + no suction + no UAS) (65%, p < 0.01). The use of sTFL provided greater stone clearance than Ho:YAG or Ho:YAG-MOSES. Aspiration improved stone clearance for sTFL (p = 0.01), but not for Ho:YAG or Ho:YAG-MOSES, consistent with the creation of smaller fragments with sTFL. Presence of a 14F UAS improved stone clearance in all scenarios (p < 0.01). Conclusions: In this ex vivo study, stone clearance was optimized under the following conditions: sTFL, 14F UAS, and aspiration. This combination resulted in 94% of stone fragments being cleared; the 6% remaining fragments were all <2 mm. In all scenarios, deployment of a 14F UAS improved stone clearance. [ABSTRACT FROM AUTHOR]

Introduction: We sought to examine the intrarenal fluid and tissue temperature alterations during dusting and fragmentation with the thulium fiber laser (TFL) in an in vivo porcine kidney. Materials and Methods: In two female Yorkshire pigs, temperature was continuously measured within the upper, interpolar, and lower calices along with the renal pelvis using multipoint thermal sensor probes; another temperature probe was situated at the tip of the ureteroscope. Four experimental protocols were performed for each animal: dual lumen ureteroscope with both warmed (37°C) irrigation and room temperature (20°C–22°C) irrigation and single lumen ureteroscope with warmed and room temperature irrigation. Of note, in each pig, one kidney underwent ureteroscopy (URS) with a 14F ureteral access sheath (UAS) in place, whereas the other kidney had no UAS placed. A 200-μm TFL fiber was fired at three laser settings: (1) dusting at 0.5 J, 80 Hz (40 W) with continuous activation until 5 minutes expired or a temperature of 44°C was reached, (2) low-power fragmentation 1 J, 10 Hz, (10 W), and (3) high-power fragmentation at 1.5 J, 20 Hz (30 W). In all cases, the pulse width was 1 ms. For fragmentation, the laser was activated for 10 seconds with a 2-second intermission for a 1-minute period (five cycles). Results: In the absence of a UAS, in all but one circumstance, temperatures reached or exceeded 44°C at all laser settings with the use of either warm or room temperature irrigation fluid, regardless of the type of ureteroscope used. Of concern, temperatures recorded at the tip of the URS were 4°C to 22°C less than the temperatures recorded in the renal calices. In contrast, with a 14F UAS in place, six distinct groups had temperatures that did not exceed 44°C, 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 recorded at the tip of the ureteroscope with the deployment of a UAS yielded temperature differences ranging from 17°C less to 19°C more than the renal calices. Conclusions: TFL is a novel laser technology for lithotripsy. In the absence of a UAS, high-power TFL fragmentation settings in particular may create temperatures within the collecting system that could result in urothelial tissue injury. Of note, peak temperatures recorded at the tip of the ureteroscope may misrepresent the actual intrarenal temperature during TFL laser lithotripsy. [ABSTRACT FROM AUTHOR]

Introduction: The advent of single-use disposable flexible ureteroscopes allows for rapid prototyping of novel endoscopes. In this regard, we sought to develop a female-specific ureteroscope, with a shorter working length, to account for the female anatomy. We hypothesized that the shorter, female-specific single-use flexible ureteroscope would engender higher irrigation flow at a given pressure than that of the standard-length ureteroscope. Methods: An in vitro analysis of a standard 65 cm Dornier Axis™ ureteroscope and a shorter, 45 cm female-specific Dornier Axis ureteroscope was performed. All other aspects of the endoscopes were identical. Each ureteroscope was oriented vertically and connected to a Thermedx® irrigation system to provide uniform pressurized flow. The average flow rate was computed over five, 2-minute periods at pressure settings of 50, 100, 150, and 200 mm Hg. Data were collected with the working channel unoccupied, after placement of a 200 μm (0.6F) holmium laser fiber and after passage of a 1.7F stone basket. The procedure was then repeated with the endoscopes at maximum deflection. Results: The female gender ureteroscope had significantly higher irrigation flow rates than the standard-length ureteroscope under all conditions by an average of 11% (p < 0.02). The highest average percent increase, 17% (p < 0.001), was seen with the 1.7F NGage® basket in the working channel with the endoscope straight. The maximum angle of deflection was not significantly different between the female gender and standard ureteroscopes with an open working channel (314° vs 315°, p = 0.86), with the 1.7F NGage basket in place (314° vs 315°, p = 0.15), and with the 200 μm holmium laser in place (316° vs 309°, p = 0.09). Conclusions: A 45 cm female gender ureteroscope allows for a higher irrigation flow rate than the standard-length ureteroscope under all test conditions. There is no added benefit with regard to deflection capabilities. [ABSTRACT FROM AUTHOR]

An actively Q-switched all-solid-state YVO4 Raman laser, which used a 885-nm side-pumped Nd:YAG laser as the fundamental wavelength and delivered yellow output, is demonstrated. An in-band pump scheme is adopted to mitigate the thermal effects in the laser crystal and a Z-shaped laser cavity is used to compensate thermal lensing further. By intracavity frequency doubling of the Stokes wave with KTP crystal, 13.7-W yellow output at a wavelength of 588 nm, with a pulse repletion frequency of 10 kHz, was obtained under a diode pump power of 233 W. Additionally, single-pulse energy was 1.37 mJ with the pulse-width of 12.5 ns, corresponding to a peak power of 110 kW. [ABSTRACT FROM AUTHOR]

An analytical model for analyzing multi-channel intracavity spectroscopy technology (ICST) is established based on rate equations of Er-doped fiber laser. With the consideration of the amplified spontaneous emission, how the mode competition influences the iterative process for a stable output is analyzed. From the perspective of iterative times, the sensitivity-enhanced mechanism of the ICST is explained. Moreover, the theoretical modeling is employed to analyze the role that the mode-competition effect plays in switching the sensing channel automatically. It is demonstrated that, owing to the mode-competition effect in the laser cavity, the modulation of the cavity loss can be used to tune the sensing channel automatically. Furthermore, our proposed theoretical modeling is verified using a multi-channel ICST sensing system. It is indicated that the calculated estimates agree well with those data from the experimental absorption spectra. The principle will play a significant role in realizing the multiplexing of ICST. [ABSTRACT FROM AUTHOR]