This PDF file contains the front matter associated with SPIE Proceedings Volume 10468, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Cystoscope cleaning and sterilization are one of the most important procedures to prevent infection in urological surgery. The current cleaning techniques have demonstrated lengthy process times or insufficient decontamination of flexible cystoscopes. Thus, high-level disinfection and sterilization are still needed to enhance cleaning efficacy. The current study demonstrated the feasibility of a combination of 405-nm laser and infrared (IR) lights to inactivate bacterial biofilms inside the working channels. Staphylococcus strains in suspension (concentration ~ 108 CFU/mL) were incubated in 24 hours at 37 0C to form biofilms on multi-well plates. Each sample initially experienced 5-minute IR dehydration (intensity = 1.5 W/cm2), and 405-nm laser system was then used for bacterial disinfection at various conditions: 19.1, 38.2, 57.3, and 76.4 J/cm2. An IR camera was deployed for real-time monitoring temperature on the biofilm surface. MTT assay was employed to assess cell viability after the treatment. The results showed that staphylococcus bacteria in liquid suspension were more resistant to 405-nm laser light than those in hard surfaces. In addition, the 405-nm laser treatment resulted in less decontaminating effectiveness while the 405-nm laser in conjunction with IR light could induce bacterial reduction up to 75% possibly due to effect low temperature dehydration. The proposed technique can be a useful modality for cystoscope cleaning and sterilization to prevent any secondary infection in the urinary tract during urological procedures. Further experiments will be conducted to validate reprocessing efficacy on various types of bacterial biofilm models along with high-level disinfectants to find the optimal cleaning doses.

Objective: To design a durable holmium laser fiber with high power, good transmission efficiency, flexible, and tight bend for holmium YAG laser lithotripsy. The new design has improved the common issues for existing Ho: YAG laser fibers including fiber fracture at bend, fiber burnt, and connector over heat. Methods and Materials: We developed fiber modeling including ray-tracing optical simulation and CFD thermal modeling. Utilizing optical simulation, we find the over-fill and offset laser light leaking into the glass capillary was effectively absorbed by the fiber and SMA connector. The connector and fiber temperature increases were calculated using CFD thermal modeling based on the optical absorption from the ray-tracing. We introduced dimpled surfaces on the glass capillary tube to strip off the un-wanted rays to prevent the fiber from burning and the connector from overheating. We built and tested several small core (242 um) Super fiber samples for testing on different holmium laser systems (Lumenis P120H and VersaPulse® 100W). We evaluated the fiber durability under high power and tight bend conditions. The % transmission, fiber flexibility, and connector temperature were all measured under these conditions. Results: We observed good agreement between our fiber test results and our optical and thermal modeling. These results help to illuminate the root cause of the holmium fiber failure modes. Indeed, the test results show the SuperFiber is very durable. For example, it delivered more than 1,000,000 joules under several stringent operating conditions including high power (50- 60W) in air, high frequency (25- 80 Hz), and 180° bend diameters from 16 mm down to 6 mm. One SuperFiber still survived after being tested at 60W (60Hz*1J) and 48W (80Hz*0.6J) while being bent to an 8 mm diameter for 30 minutes in air. This fiber has also showed a low transmission change after bending from 16mm down to 6 mm diameter (low bending induced loss).

This study characterizes laser-induced vapor bubbles for five distal fiber optic tip configurations, to provide insight into stone retropulsion experienced during laser ablation of kidney stones. A TFL with 1908-nm wavelength delivered 34 mJ energy per pulse at 500-μs pulse duration through five different fibers: 100-μm-core/170-μm-OD bare fiber tip, 150-μm- to 300-μm-core tapered fiber tip, 100-μm-core/300-μm-OD ball tip fiber, 100-μm-core/340- μm-OD hollow steel tip fiber, and 100-μm-core/560-μm-OD muzzle brake fiber tip. A high speed camera with 10- μm spatial and 9.5-μs temporal resolution imaged vapor bubble dynamics. A needle hydrophone measured pressure transients in forward (0°) and side (90°) directions while placed at a 6.8 ± 0.4 mm distance from fiber tip. Maximum bubble dimensions (width/length) averaged 0.7/1.5, 1.0/1.6, 0.5/1.1, 0.8/1.9, and 0.7/1.5 mm, for bare, tapered, ball, hollow steel, and muzzle tips, respectively (n=5). The hollow steel tip exhibited the most elongated vapor bubble shape, translating into increased forward pressure in this study and consistent with higher stone retropulsion in previous reports. Relative pressures (a.u.) in (forward/side) directions averaged 1.7/1.6, 2.0/2.0, 1.4/1.2, 6.8/1.1, and 0.3/1.2, for each fiber tip (n=5). For hollow steel tip, forward pressure was 4× higher than for bare fiber. For the muzzle brake fiber tip, forward pressure was 5× lower than for bare fiber. Bubble dimensions and pressure measurements demonstrated that the muzzle tip reduced forward pressure by partially venting vapors through side holes, consistent with lower stone retropulsion observed in previous reports.

Laser lithotripsy is the preferred application for the destruction of ureteral and kidney stones. Clinically Ho:YAG lasers (λ=2.1µm) are used due to high absorption by water to induce thermomechanical ablation. This study focussed on the investigation of different laser parameters in relation to the stone destruction efficiency. Experiments were performed using clinical available Ho:YAG laser energy transferred via a standard fibre (Ø: 365µm) onto phantom calculi (Bego-Stones of different hardness) in an aquarium set-up. Dusting can be reached most efficient by using low energy/pulse (approx. 0.5J/pulse) and repetition rate of around 40 Hz. Higher energy/pulse showed strong repulsion and thereby increased mobility, while using lower repetition rates result in longer ablation times. For hard calculi the ablation process takes a much longer time compared to soft stones. In addition the fluorescence of human urinary stones was investigated in-vitro as well as in-vivo. In-vitro investigations (n=30) were performed using fluorescence spectrometer and fluorescence microscopy techniques. Urinary stones show broad band fluorescence emission. Inhomogeneous local fluorescence sites and homogeneous surface fluorescence can be distinguished. The shell-like structure of the stones showed difference fluorescence behavior. The impact of fluorescence guidance during endoscopic laser lithotripsy will be discussed.

Inadvertent injury to important anatomic structures including major vasculature is a significant risk in minimally invasive surgery that potentially requires conversion to open surgery and results in increased morbidity and mortality. The concern of unintended injury to important anatomic structures also potentially increases operative time, which in turn lengthens a patient’s exposure to anesthesia, and increases overall cost. Surgeons operating minimal-invasively currently do not have an easy-to-use, real-time device to aid in intraoperative identification of important anatomic structures that underlie tissue planes that must be carefully dissected in a stepwise layer-by-layer fasion to avoid injury to these structures. We demonstrate a simple method of freehand diffuse optical spectroscopy imaging (freeDOSi) for the potential of intra-operatively identifying significant anatomic structures including veins and arteries underlying the plane of dissection in minimally invasive surgery. An applicator-probe that can be adaptable to and detached from an 8mm instrument for laparoscopic or robotic-assisted DOS operation has been developed. The 10mm source-detector separation renders diffuse sampling of tissue heterogeneities a few millimeters deep. Consecutively acquired DOS spectra during freehand movement of the probe on tissue surface are displayed as a time-spectral image providing spatially-resolved identification of underlying structures presenting DOS heterogeneity. Identifications of vena cava and aorta underlying fat of up to 4mm were demonstrated repeatedly in multiple pigs in vivo.

Prostate cancer (PCa) is a heterogeneous disease with multifocal origin. In current clinical care, the Gleason scoring system is the well-established diagnosis by microscopic evaluation of the tissue from trans-rectal ultrasound (TRUS) guided biopsies. Nevertheless, the sensitivity and specificity in detecting PCa can range from 40 to 50% for conventional TRUS B-mode imaging. Tissue elasticity is associated with the disease progression and elastography technique has recently shown promise in aiding PCa diagnosis. However, many cancer foci in the prostate gland has very small size less than 1 mm and those detected by medical elastography were larger than 2 mm. Hereby, we introduce optical coherence elastography (OCE) to quantify the prostate stiffness with high resolution in the magnitude of 10 µm. Following our feasibility study of 10 patients reported previously, we recruited 60 more patients undergoing 12-core TRUS guided biopsies for suspected PCa with a total of 720 biopsies. The stiffness of cancer tissue was approximately 57.63% higher than that of benign ones. Using histology as reference standard and cut-off threshold of 600kPa, the data analysis showed sensitivity and specificity of 89.6% and 99.8% respectively. The method also demonstrated potential in characterising different grades of PCa based on the change of tissue morphology and quantitative mechanical properties. In conclusion, quantitative OCE can be a reliable technique to identify PCa lesion and differentiate indolent from aggressive cancer.

Surface diffuse reflectance spectroscopy (DRS) has the potential for real-time, bed-side evaluation of solid donor organs including liver and kidney for transplant. Nilsson et al used an applicator-probe with multiple source-detector paired with a 2.5mm source-detector separation to show that DRS of liver through the capsule represents the DRS of cross-sectional liver; however, a small but consistent difference over 600nm—850nm between DRS with capsule and without capsule was observed. Understanding the effect of the capsule on surface DRS of solid capsular organs is important to accurately resolving subcapsular tissue properties for the evaluation of organ quality. We have developed a portable lab-on-a-crater DRS system with an applicator-probe with 3mm source-detector separation for evaluating human liver and kidney specimens routinely in a pathology lab. The DRS performed on liver with capsule is consistently lower in the spectral intensity between 600-850nm when compared to DRS performed on the cross-section of liver, regardless of the pathology of subcapsular parenchyma. To model the effect of capsule on surface DRS of capsular solid organs like liver, we have implemented an analytical approach based on a master-slave dual-source configuration model (Piao and Patel, App. Opt, 56(5) 1447-1452, 2017). Under the assumption of the capsular layer having lower oxygenated hemoglobin and potentially increased elastin content and by making the location and intensity of the slave-source dependent upon the properties of the capsular layer, the surface DRS predicted by this master-slave dual-source model reveals the measured pattern over 600-850nm between with the capsule and without the capsule.

Three lasers were directly compared, including the Ho:YAG laser (λ = 2100 nm), Tm fiber laser (λ = 1940 nm) operating in 3 different modes (CW, regular pulse, and super pulse), and blue diode laser (λ = 442 nm) for vaporization and coagulation efficiency for treating blood-rich soft tissues, ex vivo, in a porcine kidney model at quasi-contact cutting in water. In addition, experimental results were compared with published data on performance of KTP laser (λ = 532 nm) at similar experimental settings (Power = 60 W and cutting speed = 2 mm/s). Tm fiber laser in pulsed mode and blue laser produced highest vaporization rates of 3.7 and 3.4 mm³/s, respectively. Tm fiber laser (in both CW and pulsed modes) also produced the largest coagulation zone among the laser sources tested. A carbonization zone was observed for Tm fiber laser in CW and pulsed modes, as well as for the blue diode laser. Tm fiber laser in super-pulse mode and Ho:YAG laser both resulted in irregular coagulation zones without carbonization. Comparison with known data for KTP laser revealed that tissue effects of the blue laser are similar to that of the KTP laser. These results suggest that the combination of the two lasers (Tm fiber and blue diode) in one system may achieve high cutting efficiency and optimal coagulation for hemostasis during surgical treatment. Ex vivo testing of the combined system revealed feasibility of this approach. The combination of the CW Tm fiber laser (120W) and the blue diode laser (60W) emitting through a combination tip were compared with CW 120 W Tm fiber laser alone and 120 W Ho:YAG laser. Vaporization rates measured 34, 28, and 6 mm³/s, and coagulation zones measured 0.6, 1.3, and 1.7 mm, respectively. A carbonization zone was only observed with CW Tm fiber laser. The vaporization rate of combined CW Tm fiber laser / blue diode laser was comparable to published data for KTP laser for equivalent total power. Thus, high-power blue diode laser, Tm fiber laser, and their combination may provide an alternative to conventional Ho:YAG and KTP lasers for applications in urology and other surgical fields.

We investigated proposed mechanisms of laser lithotripsy, specifically for the novel, experimental Thulium fiber laser (TFL). Previous lithotripsy studies with the conventional Holmium:YAG laser noted a primary photothermal mechanism (vaporization). Our hypothesis is that an additional mechanical effect (fragmentation) occurs due to vaporization of water in stone material from high absorption of energy, called micro-explosions. The TFL irradiated calcium oxalate monohydrate (COM) and uric acid (UA) stones, as well as artificial stones (Ultracal30 and BegoStone), in air and water environments. TFL energy was varied to determine the relative effect on the ablation mechanism. Scanning electron microscopy (SEM) was used to study qualitative and characteristic changes in surface topography with correlation to presumed ablation mechanisms. Laser irradiation of stones in air produced charring and melting of the stone surface consistent with a photothermal effect and minimal fragmentation, suggesting no mechanical effect from micro-explosions. For COM stones ablated in water, there was prominent fragmentation in addition to recognized photothermal effects, supporting dual mechanisms during TFL lithotripsy. For UA stones, there were minimal photothermal effects, and dominant effects were mechanical. By increasing TFL pulse energy, a greater mechanical effect was demonstrated for both stone types. For artificial stones, there was no significant evidence of mechanical effects. TFL laser lithotripsy relies on two prominent mechanisms for stone ablation, photothermal and mechanical. Water is necessary for the mechanical effect which can be augmented by increasing pulse energy. Artificial stones may not provide a predictive model for mechanical effects during laser lithotripsy.

Recently, a Thulium (Tm) fiber laser operating at a wavelength of 1940 nm and peak power up to 500 W has been introduced as a promising energy source for laser lithotripsy. Direct comparative studies have demonstrated considerable advantages of Tm fiber laser over the current industry-standard 2100 nm Holmium:YAG (Ho:YAG) device in terms of ablation rate and retropulsion effects. In this work, we investigated avenues of further improving stone ablation efficiency and reducing retropulsion. Specifically, the roles of temporal pulse structure and fiber tip preparation were studied in detail. Experiments were conducted on Bego stone phantoms in an aqueous environment using a computerized 2D stage for controlled scanning of the fiber over the stone surface. High-resolution 3D-enabled optical microscopy was employed to assess both fiber tip damage and stone ablation rate. Retropulsion effects were quantified using a high-speed video camera. Fiber burn back was evaluated as well. Fiber performance could be preserved during prolonged (up to 15 min) procedures when the fiber tip was adequately prepared. Furthermore, the results were compared with available literature for similar experiments performed with the Ho:YAG laser. The data obtained provide an important foundation for optimizing clinical performance of Tm fiber systems for lithotripsy.

Optical fibers for lithotripsy are designed to deliver the maximum energy precisely to the treatment site without a decrease in performance and without increasing the risks to patients and users. One of the obstacles to constant energy delivery is burnback of the optical fiber tip. So far, researchers identified mechanical, thermal, and optical factors as mechanisms in burnback phenomena. Among mechanical factors, the force applied by urologists against a stone is expected to play a dominant role in burnback. In this study, we introduce a novel technique to measure accurately the stone depth and volume ablation under varying force. Our results show varying burnback lengths on the optical fibers and varying stone depth and volume ablation depending on the optical fiber core size. For instance, the slope of the burnback as a function of the applied force for 273 μm fibers was more than two times higher than for the 550 μm fibers. The slope of the total volume of stone ablated as function of force for 550 μm fibers was almost twice as much as for the 273 μm fibers. The data suggest urologists can maximize the stone ablation rate and minimize fiber tip burnback by controlling the applied force on the optical fiber during a lithotripsy procedure.

A nonsurgical laser procedure is being developed for treatment of female stress urinary incontinence (SUI). Previous studies in porcine vaginal tissues, ex vivo, as well as computer simulations, showed the feasibility of using near-infrared laser energy delivered through a transvaginal contact cooling probe to thermally remodel endopelvic fascia, while preserving the vaginal wall from thermal damage. This study explores optical properties of vaginal tissue in cadavers as an intermediate step towards future pre-clinical and clinical studies. Optical clearing of tissue using glycerol resulted in a 15-17% increase in optical transmission after 11 min at room temperature (and a calculated 32.5% increase at body temperature). Subsurface thermal lesions were created using power of 4.6 - 6.4 W, 5.2-mm spot, and 30 s irradiation time, resulting in partial preservation of vaginal wall to 0.8 - 1.1 mm depth.

Previous Thulium fiber laser lithotripsy (TFL) studies were limited to a peak power of 70 W (35 mJ / 500 μs), requiring operation in dusting mode with low pulse energy (35 mJ) and high pulse rate (300 Hz). In this study, a novel, compact, air-cooled, TFL capable of operating at up to 500 W peak power, 50 W average power, and 2000 Hz, was tested. The 1940-nm TFL was used with pulse duration (500 μs), average power (10 W), and fiber (270- μm-core) fixed, while pulse energy and pulse rate were changed. A total of 23 large uric acid (UA) stones and 16 large calcium oxalate monohydrate (COM) stones were each separated into 3 modes (Group 1-“Dusting”- 33mJ/300Hz; Group 2-“Fragmentation”-200mJ/50Hz; Group 3-“Dual mode”-Fragmentation then Dusting). The fiber was held manually in contact with stone on a 2-mm-mesh sieve submerged in a flowing saline bath. UA ablation rates were 2.3±0.8, 2.3±0.2, and 4.4±0.8 mg/s and COM ablation rates were 0.4±0.1, 1.0±0.1, and 0.9±0.4 mg/s, for Groups 1, 2, and 3. Dual mode provided 2x higher UA ablation rates than other modes. COM ablation threshold is 3x higher than UA, so dusting provided lower COM ablation rates than other modes. Future studies will explore higher average laser power than 10 W for rapid TFL ablation of large stones.