A Novel Method for GreenLight MoXy Laser Fiber Irrigation System to Improve Performance and Durability: A New Standard of Care?

Introduction and Objectives: The GreenLight™ MoXy® laser fiber has been used since 2010 for benign prostatic hyperplasia procedures. We tested a novel principle to increase the saline irrigation flow rates beyond the current standard of gravity drip (∼22 cc/minutes) within the fiber-attached cooling system to potentially prevent excessive tissue adherence and to eliminate the likelihood of degradation due to abnormal overheating. The objective was to assess differences between the ordinary and active pumping methods with ≥2 times flow rate after conditioning of the laser fiber. Materials and Methods: A controllable full, tissue-contact system was utilized for conditioning in a porcine model, applying 180 W of vaporization mode of GreenLight XPS console for 30 continuous minutes. Four groups were evaluated using different saline flow rates; the nominal flow rate (control group, 22 mL/minute), digital pump set (35 mL and 50 mL/minute), and a manual pressure cuff with hand pump set using a 3-L saline bag with pressure of 300 mmHg (35-80 mL/minute). At the end of the conditioning process, a mechanical pull force test was executed on the fiber metal cap to evaluate the bonding strength. A failed event was defined as the natural detachment of the metal cap during the conditioning process or a cap pull force smaller than 22.24 N resulting in detachment. Additional physical parameters, including fiber tip temperature information and laser beam power transmission efficiency, were analyzed. Results: Detachment of the cap occurred less frequently when using the 300 mmHg pressure cuff saline bag compared to the nominal flow rate (6.67% vs 50%, respectively). The average operating fiber tip temperatures were lower in the higher flow rate groups compared to nominal, measured at 315°C and 305°C. compared to 442°C. Moreover, a significantly lower FiberLife Event count and an ∼5% increase of the average final laser transmission efficiency were observed in the higher flow rate groups. Conclusions: Our study demonstrates superior results when using active pumping or high-pressure systems to increase saline flow rates in terms of laser fiber durability without any additional cost. More specifically, use of a manual pressure cuff with starting pressure at 300 mmHg, a system that is readily available in most operating rooms, increases MoXy fiber durability. Further studies are required to assess if this technique will improve user experience, clinical outcomes, and procedure costs.

In Vivo Investigation of Noncontact Rapid Photothermal Hemostasis on Venous and Arterial Bleeding.

OBJECTIVE: Endoscopic surgical procedures rigorously underscore the significance of rapid hemostasis for unavoidable intraoperative bleeding, requiring advancement of the immediate hemostatic interventions for favorable clinical outcomes. Here, we report the efficacy of a new optical treatment with dual-wavelengths to develop an endoscopic hemostasis method. METHODS: we combine visible (20-W 532 nm at 1.1 kW/cm2) and near-infrared (40-W 980 nm at 2.2 kW/cm2) wavelengths for facilitating noncontact thermal hemostasis on venous and arterial bleeders in in vivo leporine models. RESULTS: Simultaneous irradiation of 60-W dual-wavelengths allows for an increased irradiance of 3.3 kW/cm2, involving both rapid light absorption by hemoglobin and deep thermal penetration. The collective thermal effects from the combined wavelengths contribute to a significant reduction in coagulation time and a high success rate of complete hemostasis for both venous and arterial bleeders. The enhanced hemostatic potential of the dual-wavelengths treatment accompanies minimal hemorrhage, reduces inflammatory responses, and facilitates re-epithelialization. CONCLUSION: The proposed dual-wavelengths method can achieve rapid and complete hemostasis for endoscopic procedures. SIGNIFICANCE: We present the high-irradiance photothermal treatment using the dual-wavelengths as a novel method to regulate venous and arterial bleeding and potentially as a rapid noncontact hemostasis option to mitigate the risk associated with significant blood loss.

Surface modifications of optical fiber ferrule for diffusive optical-thermal transport.

The current study aimed to develop surface modifications of a capillary ferrule to avoid misalignment-related thermal damage in the fiber connector and the eventual fiber failure during high-power laser lithotripsy. Numerical analysis showed that the modified surface diffused leaking rays (high-order modes) from the misalignment. The light diffusion subsequently confined absorption-induced heat accumulation to the stainless steel connector tip (used as heat sink). Light-offset experiments validated minimal transient and steady-state heating of the modified connector surface with no thermal damage in the connector due to diffusive optical-thermal transport. The ferrule surface modifications may prevent fiber failure during the lithotripsy.

Enhanced photothermal hemostasis using dual wavelengths in an in vivo leporine kidney model.

The current study investigated the hemostatic effect of dual wavelengths on in vivo leporine kidney tissue using 532-nm and 980-nm laser systems. Three irradiation modes, 532 nm, 980 nm, and dual (532 and 980 nm) modes, were compared to test non-contact photothermal hemostasis on 36 bleeders in the kidney models. Each bleeder was flushed with saline during the irradiation. The dual mode achieved complete hemostasis more rapidly than the single modes (4.0 ± 1.4 s for dual vs. no hemostasis for 532 nm and 10.0 ± 1.3 s for 980 nm; p < 0.001). Application of 60 W from the dual wavelengths expanded the surface area of the thermal lesion (up to 60%). In vivo dual-wavelength irradiation achieved more rapid and complete hemostasis with ∼2 mm coagulation depth than the single-wavelength irradiation.

Numerical Response Surfaces of Volume of Ablation and Retropulsion Amplitude by Settings of Ho:YAG Laser Lithotripter.

Objectives: Although laser lithotripsy is now the preferred treatment option for urolithiasis due to shorter operation time and a better stone-free rate, the optimal laser settings for URS (ureteroscopic lithotripsy) for less operation time remain unclear. The aim of this study was to look for quantitative responses of calculus ablation and retropulsion by performing operator-independent experiments to determine the best fit versus the pulse energy, pulse width, and the number of pulses. Methods: A lab-built Ho:YAG laser was used as the laser pulse source, with a pulse energy from 0.2 J up to 3.0 J and a pulse width of 150 µs up to 1000 µs. The retropulsion was monitored using a high-speed camera, and the laser-induced craters were evaluated with a 3-D digital microscope. The best fit to the experimental data is done by a design of experiment software. Results: The numerical formulas for the response surfaces of ablation speed and retropulsion amplitude are generated. Conclusions: The longer the pulse, the less the ablation or retropulsion, while the longer pulse makes the ablation decrease faster than the retropulsion. The best quadratic fit of the response surface for the volume of ablation varied nonlinearly with pulse duration and pulse number.

Dual-wavelength-assisted thermal hemostasis for treatment of benign prostate hyperplasia.

Laser treatment on a large size of prostate gland often encounters significant bleeding that can prolong the entire procedure and cause urinary complications. The current study investigates the feasibility of dual-wavelength (532 and 980 nm) application to achieve rapid hemostasis for 532-nm laser prostatectomy. Porcine kidney and bleeding phantom models were tested to quantify the degree of the irreversible tissue coagulation and to estimate the time for the complete hemostasis, respectively. The ex vivo kidney testing verifies that the dual-wavelength created up to 40% deeper and 25% wider coagulation regions than a single wavelength does. The bleeding phantom testing demonstrates that due to the enhanced thermal effects, the simultaneous irradiation yields the complete photocoagulation (~11 seconds) whereas 532 or 980 nm hardly stops bleeders. Numerical simulations validate that the combined optical-thermal characteristics of both the wavelengths account for the augmented thermal coagulation. The dual-wavelength-assisted coagulation can be a feasible treatment to entail the rapid hemostasis and to facilitate the laser prostatectomy in an effective manner.

Calculus migration characterization during Ho:YAG laser lithotripsy by high-speed camera using suspended pendulum method.

Calculus migration is a common problem during ureteroscopic laser lithotripsy procedure to treat urolithiasis. A conventional experimental method to characterize calculus migration utilized a hosting container (e.g., a "V" grove or a test tube). These methods, however, demonstrated large variation and poor detectability, possibly attributed to the friction between the calculus and the container on which the calculus was situated. In this study, calculus migration was investigated using a pendulum model suspended underwater to eliminate the aforementioned friction. A high-speed camera was used to study the movement of the calculus which covered zero order (displacement), first order (speed), and second order (acceleration). A commercialized, pulsed Ho:YAG laser at 2.1 µm, a 365-µm core diameter fiber, and a calculus phantom (Plaster of Paris, 10 × 10 × 10 mm3) was utilized to mimic laser lithotripsy procedure. The phantom was hung on a stainless steel bar and irradiated by the laser at 0.5, 1.0, and 1.5 J energy per pulse at 10 Hz for 1 s (i.e., 5, 10, and 15 W). Movement of the phantom was recorded by a high-speed camera with a frame rate of 10,000 FPS. The video data files are analyzed by MATLAB program by processing each image frame and obtaining position data of the calculus. With a sample size of 10, the maximum displacement was 1.25 ± 0.10, 3.01 ± 0.52, and 4.37 ± 0.58 mm for 0.5, 1, and 1.5 J energy per pulse, respectively. Using the same laser power, the conventional method showed <0.5 mm total displacement. When reducing the phantom size to 5 × 5 × 5 mm3 (one eighth in volume), the displacement was very inconsistent. The results suggested that using the pendulum model to eliminate the friction improved sensitivity and repeatability of the experiment. A detailed investigation on calculus movement and other causes of experimental variation will be conducted as a future study.