In order to evaluate the technical adaptability of a type of disposable endoscope compared to reusable flexible endoscopes, in vitro and in vivo studies were conducted. A disposable digital ureteroscope ("chip on tip") and two reusable endoscopes were investigated with respect to spatial resolution, geometric distortion in air and water the maximum. Additionally, the clinical performance of the disposable device was tested during clinical procedures (n = 20). The disposable endoscope showed an optical resolution of 6.72 lines/mm at 10 mm distance, similar to the other devices. In comparison, the disposable endoscope showed a barrel-shaped image distortion in air of −24.2%, which is in the middle range, but was best under water (−8.6%). The bendability of 297° (275 µm fiber) and 316° (empty channel, 1.5 F basket) and the maximum irrigation (1 m: 58.1 ml/min, 2 m: 91.9 ml/min) were convincing. Clinically the maneuverability was very good in (13/20), good or satisfactory in (7/20). Visibility was evaluated as very good in (11/20), just in (1/20) either satisfactory or sufficient. The consistency of visibility was not affected in (19/20). In all cases there were no adverse events. The technical examination and clinical application of the disposable endoscope are of equal quality compared to reusable devices. Disposable endoscopes can be an alternative to reusable devices, but economic aspects such as reduction of repair costs, sterilization effort and additional waste must be taken into account.

<b><i>Introduction:</i></b> Indication of ureteroscopy for the treatment of urolithiasis has expanded immensely over the last decade. Fiber-optic and digital reusable instruments present the standard in clinical practice, but various newly available single-use devices might offer an exciting alternative. To date, the evidence is limited to clinical evaluation and efficacy of single-use ureteroscopes (URS) compared to standard instruments. Therefore, we evaluate a single-use instrument’s clinical characteristics and efficacy in direct comparison with a fiber-optic and digital device. <b><i>Methods:</i></b> A prospective study was conducted for patients undergoing endoscopic therapy for urolithiasis at a tertiary care center. We evaluated the different instruments’ clinical performance in categories of visibility, the stability of visibility, irrigation flow, and surgeon’s satisfaction. Statistical analyses were performed by SPSS using the Chi-Quadrat and Kruskal-Wallis test. A <i>p</i> value of <i>p</i> ≤ 0.05 was defined as statistically significant. <b><i>Results:</i></b> A total number of 77 patients were included and distributed as follows: 35 (46.7%) single-use, 19 (25.3%) digital, and 23 (28%) fiber-optic URS. Patients’ characteristics were homogenous over the three cohorts in sex, stone amount, and localization. The stone-free rate was equal in all three cohorts (<i>p</i> = 0.31). We identify stability of visibility, irrigation flow, and satisfaction were equal in all cohorts (<i>p</i> = 0.73; <i>p</i> = 0.20; <i>p</i> = 0.20). We report a significant difference in visibility, with 100% rated excellent in the digital URS group (<i>p</i> = 0.028). <b><i>Discussion/Conclusions:</i></b> Single-use URS achieve comparable clinical outcomes with equal stone-free rates in direct comparison with fiber-optic and digital reusable instruments. Accordingly, single-use devices present an adequate alternative for endoscopic therapy of urolithiasis.

Knowledge of tissue optical properties, in particular the absorption μ a and the reduced scattering coefficient μ 0 s , is required for diagnostic and therapeutic applications in which the light distribution during treatment has to be known. As it is generally very difficult to obtain this information with sufficient accuracy in vivo, optical properties are often approximately determined on ex vivo tissue samples. In this case, the obtained optical properties may strongly depend on the sample preparation. The extent of the expectable preparationdependent differences was systematically investigated in comparative measurements on dissected and homogenized porcine tissue samples (liver, lung, brain, and muscle). These measurements were performed at wavelengths 520, 635, 660, and 785 nm, using a dual-step reflectance device and at a spectral range of 515 to 800 nm with an integrating sphere setup. In a third experiment, the density of tissue samples (dissected and homogenized) was investigated, as the characteristic of the packaging of internal tissue structures strongly influences the absorption and scattering. The standard errors of the obtained absorption and reduced scattering coefficients were found to be reduced in case of homogenized tissue. Homogenizing the tissues also allows a much easier and faster sample preparation, as macroscopic internal tissue structures are destroyed in the homogenized tissue so that a planar tissue sample with well-defined thickness can easily and accurately be prepared by filling the tissue paste into a cuvette. Consequently, a better reproducibility result was obtained when using homogenized samples. According to the density measurements accomplished for dissected and homogenized tissue samples, all types of tissues, except lung, showed a decrease in the density due to the homogenization process. The presented results are in good agreement for μ 0 s regardless of the preparation procedure, whereas μ a differs, probably influenced by blood content and dehydration. Because of faster and easier preparation and easier sample positioning, homogenization prior to measurement seems to be suitable for investigating the optical properties ex vivo. Additionally, by means of using the homogenization process, the sample size and thickness do not need to be particularly large, as is the case for most biopsies from the OR.

The fragmentation efficiency on Bego artificial stones during lithotripsy and the propulsive effect (via video tracking) was investigated for a variety of laser settings. A variation of the laser settings (pulse energy, pulse duration, repetition rate) altered the total application time required for stone fragmentation, the stone break up time, and the propulsion. The obtained results can be used to develop lithotripsy devices providing an optimal combination of low stone propulsion and high fragmentation efficacy, which can then be evaluated in a clinical setting. Additionally, the fluorescence of human kidney stones was inspected endoscopically in vivo. Fluorescence light can be used to detect stone-free areas or to clearly distinguish calculi from surrounding tissue or operation tools.

The proposed vertical column method with video tracking appears advantageous compared to the pendulum method in terms of the statistical significance of the obtained results. This may partly be understood by the fact that the entire motion of the stones contributes to the data analysis, rather than just their maximum distance from the initial position. The key difference is, however, that the pendulum method involves only one single laser pulse in each experiment run, which renders this method rather tedious to perform. Furthermore, the video tracking method appears much better suited to model a clinical lithotripsy intervention that utilizes longer series of laser pulses at higher repetition rates. The proposed video tracking method can conveniently and quickly deliver results for a large number of laser pulses that can easily be averaged. An optimization of laser settings to achieve minimal propulsive stone movement should thus be more easily feasible with the video tracking method in connection with the vertical column setup. Lasers Surg. Med. 50:333-339, 2018. © 2017 Wiley Periodicals, Inc.