ObjectivesFluorescence spectroscopy of human urine is a method with the potential to gain importance as a diagnostic tool in the medical field, e.g., for measuring Coproporphyrin III (CPIII) as an indicator of cancer and acute types of porphyria. Food can change human urine's color, which could influence the urine fluorescence spectrum and the detection of CPIII in urine. To determine if there is a noticeable influence on the urine fluorescence spectrum or on the detection of CPIII in urine, 16 vitamin supplements, and three food items were tested. Such investigation may also prevent false interpretation of measured data.MethodsUrine samples were collected before and after (overnight, ca. 8 h) intake of each test substance. Samples were investigated by fluorescence spectrum analysis. At excitation wavelengths from 300 to 500 nm and emission wavelengths from 400 to 700 nm excitation-emission-matrices were measured. Data obtained from urine before intake were compared to the data from overnight urine. Furthermore, the investigation of any interference with the CPIII concentration was performed at an excitation wavelength of 407 +/- 3 nm and emission wavelengths of 490-800 nm.ResultsOnly vitamin B2, but none of the other tested substances, showed noticeable influence on the urine fluorescence spectrum. None of the tested substances showed noticeable interference with the recovery rate of CPIII.ConclusionsThe correct interpretation of measured data by fluorescence spectroscopy is possible with the exception if vitamin B2 supplementation was performed; thus, the consumption of vitamin B2 supplements before fluorescence testing of the patient's urine should be avoided and/or must be requested. CPIII concentrations could reliably be measured in all cases.

Brain tumor treatment via interstitial photodynamic therapy (iPDT) needs precise treatment light delivery, which is essential for the conduction of the therapy [1]. The light delivery and the resulting light dosimetry are highly dependent on the optical tissue properties of the tumor tissue and the surrounding brain tissue. Employing intraoperative spectral online monitoring (SOM), it looks possible to assess the treatment light transmittance between the used light applicators and monitor potential changes during therapy [2]. Changes have been observed during clinical iPDT-illumination and can be interpreted as changes in the optical tissue properties [2, 3]. In vitro experiments mimicking the clinical iPDT-illumination situation using liquid optical tissue phantoms, including blood, showed SOM intensity changes in transmittance. Due to simultaneous remission spectroscopy, this can be related to the deoxygenation of hemoglobin and its oxidation to methemoglobin (MetHb) [4]. The analysis of data from clinical iPDT-procedures confirmed this interpretation. Based on intraoperative SOM data, changes in the optical absorption coefficient have been calculated and correlated with newly diagnosed early visible intrinsic T1-hyperintensity in the treatment volume [3]. The intrinsic T1 hyperintensity is clinically an indicator of the formation of MetHb after silent hemorrhages, which may occur during iPDT. As the T1 hyperintensity was early visible in the MRI, the corresponding early appearance of MetHb was in context with the iPDT and consistent with the in vitro experiments. Further in vitro experiments showed that changes in optical tissue properties and hemoglobin oxidation is not only possible due to ROS production during iPDT but also due to a slight temperature increase during iPDT by 4°C [5]. These results give more insight into mechanisms occurring during iPDT irradiation, but the impact on treatment outcome has still to be assessed.

Existing optical tissue phantoms are usually designed for wide field imaging systems and not readily usable for microscopic or endoscopic systems, especially such without any z-stage. Therefore a fs-laser microstructured artificial tissue phantom with adaptable geometric, tissue-optical and localized fluorescence properties enabling comparison and testing of different microscopic/endoscopic systems was designed, characterized and tested.

Introduction: 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. Methods: 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 p value of p ≤ 0.05 was defined as statistically significant. Results: 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 (p = 0.31). We identify stability of visibility, irrigation flow, and satisfaction were equal in all cohorts (p = 0.73; p = 0.20; p = 0.20). We report a significant difference in visibility, with 100% rated excellent in the digital URS group (p = 0.028). Discussion/Conclusions: 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.

Objectives For the development and validation of diagnostic procedures based on microscopic methods, knowledge about the imaging depth and achievable resolution in tissue is crucial. This poses the challenge to develop a microscopic artificial phantom focused on the microscopic instead of the macroscopic optical tissue characteristics. Methods As existing artificial tissue phantoms designed for image forming systems are primarily targeted at wide field applications, they are unsuited for reaching the formulated objective. Therefore, a microscopy- and microendoscopy-suited artificial tissue phantom was developed and characterized. It is based on a microstructured glass surface coated with fluorescent beads at known depths covered by a scattering agent with modifiable optical properties. The phantom was examined with different kinds of microscopy systems in order to characterize its quality and stability and to demonstrate its usefulness for instrument comparison, for example, regarding structural as well as fluorescence lifetime analysis. Results The analysis of the manufactured microstructured glass surfaces showed high regularity in their physical dimensions in accordance with the specifications. Measurements of the optical parameters of the scattering medium were consistent with simulations. The fluorescent beads coating proved to be stable for a respectable period of time (about a week). The developed artificial tissue phantom was successfully used to detect differences in image quality between a research microscope and an endoscopy based system. Plausible causes for the observed differences could be derived based on the well known microstructure of the phantom. Conclusions The artificial tissue phantom is well suited for the intended use with microscopic and microendoscopic systems. Due to its configurable design, it can be adapted to a wide range of applications. It is especially targeted at the characterization and calibration of clinical imaging systems that often lack extensive positioning capabilities such as an intrinsic z-stage.

The temperature dependency (25°C – 50°C) of optical tissue properties was investigated on artificial and animal tissue samples. An increase of optical properties with temperature was found for all tissue phantoms and most tissue samples.

Abstract Spectroscopic methods for quantitative detection of molecules of the heme synthesis and heme metabolism are presented. This can be used to diagnose disease patterns such as iron deficiency, porphyria or free hemoglobin. This article combines an overview of clinical conditions associated with disorders of heme biosynthesis and presents selected laboratory findings in the development of portable diagnostic devices. An iron deficiency measurement device has already been validated as a portable device in clinical trials, two other methods have been tested according to EMA guidelines and are available for use in clinical validation studies. The presented rapid, low‐cost and low‐effort methods can support diagnosis in everyday clinical practice and initiate more targeted therapies, even for rare disease conditions.

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.

To investigate the fragmentation capacity, clearance time, and drilling speed of combined ultrasonic with impact dual-energy and single energy ultrasonic lithotripter devices. Stone fragmentation and clearance tests were performed under direct view in an underwater layered hemisphere by four different operators using artificial stones (n = 10/operator). Time for complete clearance was measured. Drilling tests were performed using an underwater setup, consisting of a mounting rack for fixing the lithotripter handpiece with the probe in vertical position and in contact with the stone phantom placed on one side of a balance for defined and constant contact application pressure equivalent to 450 g load. Time until complete perforation or in case of no perforation, the penetration depth after 60 s into the stone sample was recorded. Four devices, one single energy device (SED), one dual-energy dual probe (DEDP), two dual-energy single probe (DESP-1, DESP-2), with different parameters were tested. Stone fragmentation and clearance speed were significantly faster for dual-energy device DESP-1 compared to all other devices (p < 0.001). Using DESP-1, the clearance time needed was 26.0 ± 5.0 s followed by DESP-2, SED and DEDP requiring 38.4 ± 5.8 s, 40.1 ± 6.3 s and 46.3 ± 11.6 s, respectively. Regarding the drilling speed, DESP-1 was faster compared to all other devices used (p < 0.05). While the drilling speed of DESP-1 was 0.69 ± 0.19 mm/s, compared to 0.49 ± 0.18 mm/s of DESP-2, 0.47 ± 0.09 mm/s of DEDP, and 0.19 ± 0.03 mm/s of SED. The dual-energy/single-probe device combining ultrasonic vibrations with electromechanical impact was significantly faster in fragmentation and clearing stone phantoms as well as in drilling speed compared to all other devices.

AbstractThis manuscript summarizes the laser‐induced method for the destruction of kidney stones. Special emphasis is placed on laser‐induced lithotripsy, and a historical overview is given from the early beginnings in 1968 to the current developments. New laser parameter settings have to be tested in order to characterize novel laser devices for best clinical results and to meet demanding medical needs. At present, the stones are usually dusted, which makes it possible to flush these tiny fragments out of the urinary system without having to remove larger fragments additionally. Two in vitro setups were used to quantitatively evaluate the dust content and stone movement (propulsion) in a defined laboratory environment. The autofluorescence of stones can be used either to verify a stone‐free environment or to introduce safety measures such as differentiation between stone and tissue. In addition to describing these state‐of‐the‐art methods, a historical overview is given from the early beginnings in 1968 to the current developments.

Die laserinduzierte Lithotripsie ist eine endoskopische Methode zur Behandlung von Harnsteinleiden. Sie steht in direkter Konkurrenz zur extrakorporalen Stoswellenlithotripsie (ESWL) und der perkutanen Nephrolitholapaxie (PCNL). Bei der laserinduzierten Lithotripsie wird gepulstes Laserlicht uber einen Lichtwellenleiter im Arbeitskanal eines Endoskops direkt auf den Harnstein geleitet und sorgt dort aufgrund photothermischer und mechanischer Effekte fur die Zerkleinerung des Steines. Der Ho:YAG Laser (λ: 2.1 μm) gilt aufgrund der hohen Absorption dieser Wellenlange in Wasser (α: 2.78 mm-1) und der guten Transmission der mittleren-Infrarotstrahlung in Low-OH Glasfasern als Goldstandard fur diese Vorgehensweise in der Steintherapie. Die eingebrachte Laserenergie bewirkt aber auch eine Krafteinwirkung auf den Stein und umliegende Fragmente was zu einer Steinbewegung fuhrt (Propulsion). Durch die Propulsion konnen zuruckgestosene Fragmente schwer auffindbar sein oder die Operation aufgrund zeitintensiven Nachfuhrens des Endoskops erschweren. Dies kann einerseits zu einer erhohten Rezidivrate durch Fragmentreste oder zu insgesamt langeren Operationszeit fuhren. Daher wurde ein modellhafter Aufbau zur Quantifizierung von Fragmentierungsraten und Propulsionseinflussen durch Variation der Laserparameter (Energie pro Puls, Repetitionsrate und optische Pulslange) bei der Ho:YAG laserinduzierten Lithotripsie entwickelt. Des Weiteren wurden die Fluoreszenzeigenschaften von humanen Nierensteinen mittels spektraler Fluoreszenzmikroskopie bei unterschiedlichen Anregungswellenlangen betrachtet, mit dem Ziel das Auffinden von Steinen und Fragmenten technisch zu vereinfachen. Zur Quantifizierung der Abtragsraten wurde ein Messaufbau konstruiert und im Rahmen von Untersuchungen systematisch verschiedene Laserparameter (Energie (E): 0.5 J/Puls - 2.5 J/Puls, Repetitionsraten (f): 10 Hz - 80 Hz, optische Pulsdauer (t) 0.3 ms - 4 ms an kunstlichen Steinen (Bego, Mischverhaltnis 15:4, Kantenlange 5 mm) bewertet. Bei der Fragmentierung (Ablation) wurde insbesondere das sogenannte “Dusting” untersucht. Hierbei ist das Ziel den Stein aufgrund geschickt gewahlter Laserparameter zu zerstauben (Fragmente < 1 mm) und direkt mit den Spulstrom auszuwaschen. Die Untersuchung der Propulsion erfolgte mit einem Messaufbau, bestehend aus einem Plexiglasrohrchen mit einer konisch zulaufenden Innenbohrung (O: 8 mm), welches als Fuhrung fur den durch bodenseitige Laserapplikation nach oben beschleunigten kunstlichen Stein dient. Aufgrund von Hydrodynamik und Schwerkraft wird der Stein in seine Ausgangsposition zuruckgebracht. Diese Steinbewegung wird mit einer High-Speed-Kamera (1000 Bilder/s) aufgenommen und per Software in ein Bewegungsprofil umgewandelt. Durch Bestimmung der Steigung fur jede der aufsteigenden Flanken, respektive der mittleren Geschwindigkeit in diesem Zeitintervall, kann eine Quantifizierung der Propulsion erreicht werden. Von Patienten stammende Harnsteine wurden mit einem Fluoreszenzmikroskop in vitro fur die Anregungswellenlangen (400±5) nm, (450±10) nm und (550±5) nm auf ihre Fluoreszenz untersucht. Das remittierte Fluoreszenzlicht durchlief vor der spektralen Detektion je nach Anregungslicht verschiedene Langpassfilter (λ > 470 nm, λ > 520 nm, λ > 590 nm). Zusatzlich wurde in vivo die Fluoreszenzantwort zweier Nierensteine wahrend einer OP bei gruner Anregung (λ = 500- 570 nm) im Spektralbereich oberhalb 610 nm mit einem Endoskopkamerasystem beobachtet. Die optischen Gewebeeigenschaften, Absorption und reduzierte Streuung, wurden am Schweinemodell (Leber, Lunge, Gehirn, Muskel) uber ortsaufgeloste Remissions- und Ulbrichtkugelmessungen bestimmt. Die Bestimmung der optischen Eigenschaften von sezierten und homogenisierten Gewebeproben am Schweinemodell fokussierte sich auf die Vergleichbarkeit und Reproduzierbarkeit der Messergebnisse fur diese beiden Praparationsmethoden. Neue Ho:YAG Lasersysteme mit vier Laserkavitaten bieten eine grose Variation an Laserparametern: Repetitionsraten bis zu 100 Hz, Pulsenergien bis 6 J und Pulslangen von bis zu 4 ms. Durch die hohen eingebrachten mittleren optischen Leistungen (bis zu 120 W) konnen Kollateralschaden an umliegenden Geweben entweder durch direkten Laserbeschuss oder durch die Erhitzung des Gemisches aus Harn und Spulflussigkeit kommen. Die durchgefuhrten Experimente zur Bestimmung der optischen Eigenschaften sind auch fur Laserlicht den mittleren Infrarotbereich anwendbar, bilden die Basis fur Untersuchungen zu moglichen Kollateralschaden bei medizinischen Laseranwendungen und konnen somit wichtige Anhaltspunkte fur zukunftige technische Entwicklung von medizinischen Lasergeraten mit sich bringen.

Thermography is a widespread non-contact imaging method for determining temperature. Its application in medicine, however, has so far been limited and its significance h as n ot b een e xtensively r eviewed i n t his field. Hence the applicability of thermography in laser medicine has been evaluated by determining the corresponding essential parameters. This includes the emissivity of biological tissue, tissue phantoms and cylindrical light diffusers used for interstitial photodynamic therapy (iPDT). The time-dependent surface temperature of light diffusers for iPDT was thermographically recorded in air and compared to thermocouple measurements. Furthermore, laser light was applied via surface-parallel cylindrical light diffusers for iPDT to a tissue phantom and to porcine brain tissue in an iPDT-like setup. In case of the tissue phantom, four light diffusers were positioned at different lateral positions and depths below the surface, in case of the porcine tissue, only one diffuser was used. The temperature distribution at the surface was recorded thermographically and by a thermocouple. The results were compared to Monte Carlo based simulations of the temperature distribution at the surface. In the context of laser medicine, thermography seems useful for the inspection of components for laser light application. To protect tissue from unwanted thermal effects, the surface temperature of light applicators can be examined to localize potential temperature hot spots. Nevertheless limitations of thermography have to be considered, especially the fact that this method provides information exclusively about the temperature distribution at the surface.

Interstitial photodynamic therapy (iPDT) is currently being investigated as a light-based treatment option for highly malignant brain tumours (glioblastomas/GBM). To obtain a sufficient irradiation of the tumour, quantitative knowledge about the light propagation in the tissue is required for the light dosimetry calculations underlying the clinical treatment planning. To individualize the light dosimetry calculations, the optical properties of the irradiated tissue need to be determined in-vivo. A novel approach for this purpose is based on the direction-resolved light detection within the tissue, using a rotating optical side-view probe. During measurement, the tissue is irradiated via a separate interstitially placed light applicator, and from the angular dependence of the recorded signal the optical tissue properties are calculated, based on a solution of the radiative transfer equation (RTE). Measurements were performed on liquid tissue phantoms and biological tissue samples. As a result, an over- and underestimation of the calculated optical absorption and scattering coefficients may arise in some situations, but the effective attenuation coefficient remains largely unaffected and corresponds well with literature values.

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.

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.

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.

Knowledge of tissue optical properties, in particular the absorption mu(a) and the reduced scattering coefficient mu(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 preparation-dependent 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 mu(s)' regardless of the preparation procedure, whereas mu(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. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)

OBJECTIVES:Ureteroscopic laser lithotripsy is an important and widely used method for destroying ureter stones. It represents an alternative to ultrasonic and pneumatic lithotripsy techniques. Although these techniques have been thoroughly investigated, the influence of some physical parameters that may be relevant to further improve the treatment results is not fully understood. One crucial topic is the propulsive stone movement induced by the applied laser pulses. To simplify and speed up the optimization of laser parameters in this regard, a video tracking method was developed in connection with a vertical column setup that allows recording and subsequently analyzing the propulsive stone movement in dependence of different laser parameters in a particularly convenient and fast manner. MATERIALS AND METHODS:Pulsed laser light was applied from below to a cubic BegoStone phantom loosely guided within a vertical column setup. The video tracking method uses an algorithm to determine the vertical stone position in each frame of the recorded scene. The time-dependence of the vertical stone position is characterized by an irregular series of peaks. By analyzing the slopes of the peaks in this signal it was possible to determine the mean upward stone velocity for a whole pulse train and to compare it for different laser settings. For a proof of principle of the video tracking method, a specific pulse energy setting (1 J/pulse) was used in combination with three different pulse durations: short pulse (0.3 ms), medium pulse (0.6 ms), and long pulse (1.0 ms). The three pulse durations were compared in terms of their influence on the propulsive stone movement in terms of upward velocity. Furthermore, the propulsions induced by two different pulse energy settings (0.8 J/pulse and 1.2 J/pulse) for a fixed pulse duration (0.3 ms) were compared. A pulse repetition rate of 10 Hz was chosen for all experiments, and for each laser setting, the experiment was repeated on 15 different freshly prepared stones. The latter set of experiments was compared with the results of previous propulsion measurements performed with a pendulum setup. RESULTS:For a fixed pulse energy (1 J/pulse), the mean upward propulsion velocity increased (from 120.0 to 154.9 mm · s-1 ) with decreasing pulse duration. For fixed pulse duration (0.3 ms), the mean upward propulsion velocity increased (from 91.9 to 123.3 mm · s-1 ) with increasing pulse energy (0.8 J/pulse and 1.2 J/pulse). The latter result corresponds roughly to the one obtained with the pendulum setup (increase from 61 to 105 mm · s-1 ). While the mean propulsion velocities for the two different pulse energies were found to differ significantly (P < 0.001) for the two experimental and analysis methods, the standard deviations of the measured mean propulsion velocities were considerably smaller in case of the vertical column method with video tracking (12% and 15% for n = 15 freshly prepared stones) than in case of the pendulum method (26% and 41% for n = 50 freshly prepared stones), in spite of the considerably smaller number of experiment repetitions ("sample size") in the first case. CONCLUSION: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.