Evaluation of a Novel Single-Use Flexible Ureteroscope.

Introduction: A novel single-use flexible ureteroscope promises the optical characteristics and maneuverability of a reusable fourth-generation flexible ureteroscope. In this study, the LithoVue Single-Use Digital flexible ureteroscope was directly compared with contemporary reusable flexible ureteroscopes, with regard to optics, deflection, and irrigation flow. Methods: Three flexible ureteroscopes such as the LithoVue (Single Use; Boston Scientific), Flex-Xc (Karl Storz, Germany), and Cobra (Richard Wolf, Germany) were assessed in vitro for image resolution, distortion, color representation, grayscale imaging, field of view, and depth of field. Ureteroscope deflection was tested with an empty channel followed by placement of a 200 µm laser fiber and a 1.9F wire basket, a 2.0F nanoelectric pulse lithotripsy (NPL) probe, and a 2.4F NPL probe. Ureteroscope irrigation flow was measured using normal saline at 100 cm, with an empty channel followed by a 200 µm laser fiber, a 1.9F wire basket and a 2.0F NPL probe. Results: The LithoVue showed the largest field of view, with excellent resolution, image distortion, and depth of field. No substantial difference was demonstrated in color reproducibility or in the discernment of grayscales between ureteroscopes. The LithoVue maintained full deflection ability with all instruments in the working channel, although the Flex-Xc and Cobra ureteroscopes showed loss of deflection ranging from 2° to 27°, depending on the instrument placed. With an empty channel, the LithoVue showed an absolute flow rate similar to the Flex-Xc ureteroscope (p = 0.003). It maintained better flow with instruments in the channel than the Flex-Xc ureteroscope. The Cobra ureteroscope has a separate 3.3F instrument channel, keeping flow rates the same with instrument insertion. Conclusion: The LithoVue Single-Use Digital ureteroscope has comparable optical capabilities, deflection, and flow, making it a viable alternative to standard reusable fourth-generation flexible digital and fiberoptic ureteroscopes.

Let's Get to the Point: Comparing Insertion Characteristics and Scope Damage of Flat-Tip and Ball-Tip Holmium Laser Fibers.

INTRODUCTION: A ball-tip holmium laser fiber (TracTip; Boston Scientific) has been developed to theoretically reduce damaging friction forces generated within a ureteroscope working channel. We compared the insertional forces and damage with a ureteroscope inner lining when inserting standard flat-tip and ball-tip laser fibers. MATERIALS AND METHODS: A standard ureteroscope channel liner was placed in a 3D-printed plastic mold. Molds were created at four angles of deflection (30°, 45°, 90°, and 180°) with a 1 cm radius of curvature. New 200 µm ball-tip (TracTip; Boston Scientific) and 200 µm flat-tip (Flexiva; Boston Scientific) laser fibers were advanced through the liner using a stage controller. A strain gauge was used to measure force required for insertion. Each fiber was passed 600 times at each angle of deflection. The ureteroscope liner was changed every 150 passes. Leak testing was performed every 50 passes or when the insertional force increased significantly to assess damage to the liner. RESULTS: At all deflection angles, the average insertional force was significantly lower with the ball-tip laser fibers compared with flat-tip laser fibers (p < 0.001). All trials with the ball-tip lasers were completed at each angle without any leaks. Two of four trials using flat-tip fibers at 45° deflection caused liner leaks (at 91 and 114 passes). At 90° deflection, all flat-tip trials caused liner leaks on first pass. The 180° trials could not physically be completed with the flat-tip laser fiber. Within the flat- and ball-tip groups, an increasing amount of force was needed to pass the fiber as the degree of deflection increased (p < 0.001). CONCLUSIONS: The ball-tip holmium laser fiber can be safely passed through a deflected ureteroscope without causing liner perforation. The standard flat-tip fiber requires greater insertion force at all angles and can cause the ureteroscope liner to leak if it is deflected 45° or more.

Next-Generation Single-Use Ureteroscopes: An In Vitro Comparison.

INTRODUCTION: Single-use ureteroscopes have been gaining popularity in recent years. We compare the optics, deflection, and irrigation flow of two novel single-use flexible ureteroscopes-the YC-FR-A and the NeoFlex-with contemporary reusable and single-use flexible ureteroscopes. METHODS: Five flexible ureteroscopes, YC-FR-A (YouCare Tech, China), NeoFlex (Neoscope, Inc., USA), LithoVue (Boston Scientific, USA), Flex-Xc (Karl Storz, Germany), and Cobra (Richard Wolf, Germany), were assessed in vitro for image resolution, distortion, field of view, depth of field, color representation, and grayscale imaging. Ureteroscope deflection and irrigation were also compared. RESULTS: The YC-FR-A showed a resolution of 5.04 lines/mm and 4.3% image distortion. NeoFlex showed a resolution of 17.9 lines/mm and 14.0% image distortion. No substantial difference was demonstrated regarding the other optic characteristics between the two. Across all tested ureteroscopes, single-use or reusable, the digital scopes performed best with regard to optics. The YC-FR-A had the greatest deflection at baseline, but lacks two-way deflection. The NeoFlex had comparable deflection at baseline to reusable devices. Both ureteroscopes had substantial loss of deflection with instruments in the working channel. The YC-FR-A had the greatest irrigation rate. The NeoFlex has comparable irrigation to contemporary ureteroscopes. CONCLUSIONS: The YouCare single-use fiberoptic flexible ureteroscope and NeoFlex single-use digital flexible ureteroscope perform comparably to current reusable ureteroscopes, possibly making each a viable alternative in the future. Newer YouCare single-use flexible ureteroscopes with a digital platform and two-way deflection may be more competitive, while the NeoFlex devices are undergoing rapid improvement as well. Further testing is necessary to validate the clinical performance and utility of these ureteroscopes, given the wide variety of single-use devices under development.

Variable Pulse Duration From a New Holmium:YAG Laser: The Effect on Stone Comminution, Fiber Tip Degradation, and Retropulsion in a Dusting Model.

OBJECTIVE: To more clearly define the efficiency and potential benefits of variable pulse-width laser technology for ureteroscopic lithotripsy, we performed comparative in vitro evaluations assessing stone comminution, laser fiber tip degradation, and stone retropulsion. METHODS: All experiments were conducted using a Swiss LaserClast Holmium:YAG laser (Electro Medical Systems, Nyon, Switzerland) with adjustable pulse duration (300 µs-1500 µs). To assess comminution efficiency and fiber tip degradation, a "dusting" model was employed; the laser fiber tip was moved by a 3-dimensional positioning system in a spiral motion across a flat BegoStone surface submerged in water. Comminution efficiency was measured as the loss of stone mass while fiber tip degradation was measured simultaneously. The same laser and fiber were used in a pendulum model to measure stone retropulsion with a high-speed resolution camera. RESULTS: In our dusting model, comminution was significantly greater at high energy (2 J/5 Hz). At the high energy setting, comminution was significantly greater with long pulse duration than short pulse, although this difference was not seen at the high frequency setting (1 J/10 Hz). Tip degradation was increased at high energy settings and was even more pronounced with short pulse duration than long pulse. Short pulse duration caused far more retropulsion than the long pulse setting. CONCLUSION: In an in vitro dusting model, a longer laser pulse duration provides effective stone comminution with the advantage of reducing laser fiber tip degradation and stone retropulsion.

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

PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter.

The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The -6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters.

The digital flexible ureteroscope: in vitro assessment of optical characteristics.

INTRODUCTION: Recent advances in endoscope design have placed the charged coupled device chip on the tip of the endoscope. The image is instantly digitalized and converted into an electrical signal for transmission. Digital technology was first introduced into flexible cystoscopes/nephroscopes and subsequently into rigid and flexible ureteroscopes. Herein, we assess the image characteristics and advantages of a new generation of digital flexible ureteroscopes. METHODS: The Olympus URF-V flexible digital ureteroscope and the Olympus URF-P3 fiberoptic ureteroscope were assessed in vitro for image resolution, distortion, color representation, grayscale imaging, field of view, and depth of field. RESULTS: The digital ureteroscope had a higher resolution at 3, 5, 10, and 20 mm (25.2 lines/mm vs. 8.0, 14.1 vs. 5.0, 6.3 vs. 2.8, and 3.2 vs. 1.3), respectively. Distortion with the digital flexible ureteroscope was lower, though not statistically significant. Color representation was better with the digital ureteroscope, whereas contrast evaluation was comparable between both scopes. The digital flexlible ureteroscope produced a 5.3 times larger image size compared with the standard fiberoptic flexible uretersocpe with a narrower field of view. The depth of field was limited by light and not the optic or the camera for both ureteroscopes. CONCLUSIONS: The development of digital flexible ureteroscopes represents a significant technological advance in urology. These devices offer significantly improved resolution and color reproduction as compared with traditional fiberoptic flexible ureteroscopes. Future clinical trials are warranted to ultimately determine the advantages of these innovative endoscopes.

A simple method for fabricating artificial kidney stones of different physical properties.

A simple method for preparing artificial kidney stones with varying physical properties is described. BegoStone was prepared with a powder-to-water ratio ranging from 15:3 to 15:6. The acoustic properties of the phantoms were characterized using an ultrasound transmission technique, from which the corresponding mechanical properties were calculated based on elastic wave theory. The measured parameters for BegoStone phantoms of different water contents are: longitudinal wave speed (3,148-4,159 m/s), transverse wave speed (1,813-2,319 m/s), density (1,563-1,995 kg/m(3)), longitudinal acoustic impedance (4.92-8.30 kg/m(2) s), transverse acoustic impedance (2.83-4.63 kg/m(2) s), Young's modulus (12.9-27.4 GPa), bulk modulus (8.6-20.2 GPa), and shear modulus (5.1-10.7 GPa), which cover the range of corresponding properties reported in natural kidney stones. In addition, diametral compression tests were carried out to determine tensile failure strength of the stone phantoms. BegoStone phantoms with varying water content at preparation have tensile failure strength from 6.9 to 16.3 MPa when tested dry and 3.2 to 7.1 MPa when tested in water-soaked condition. Overall, it is demonstrated that this new BegoStone preparation method can be used to fabricate artificial stones with physical properties matched with those of natural kidney stones of various chemical compositions.

Dual-energy computed tomography with advanced postimage acquisition data processing: improved determination of urinary stone composition.

INTRODUCTION: The characterization of urinary calculi using noninvasive methods has the potential to affect clinical management. CT remains the gold standard for diagnosis of urinary calculi, but has not reliably differentiated varying stone compositions. Dual-energy CT (DECT) has emerged as a technology to improve CT characterization of anatomic structures. This study aims to assess the ability of DECT to accurately discriminate between different types of urinary calculi in an in vitro model using novel postimage acquisition data processing techniques. METHODS: Fifty urinary calculi were assessed, of which 44 had >or=60% composition of one component. DECT was performed utilizing 64-slice multidetector CT. The attenuation profiles of the lower-energy (DECT-Low) and higher-energy (DECT-High) datasets were used to investigate whether differences could be seen between different stone compositions. RESULTS: Postimage acquisition processing allowed for identification of the main different chemical compositions of urinary calculi: brushite, calcium oxalate-calcium phosphate, struvite, cystine, and uric acid. Statistical analysis demonstrated that this processing identified all stone compositions without obvious graphical overlap. CONCLUSION: Dual-energy multidetector CT with postprocessing techniques allows for accurate discrimination among the main different subtypes of urinary calculi in an in vitro model. The ability to better detect stone composition may have implications in determining the optimum clinical treatment modality for urinary calculi from noninvasive, preprocedure radiological assessment.