Stone Motion Research Articles

Numerical analysis of an obstacle motion in the human ureter using the dynamic mesh approach.

Peristalsis is a common motion in various biological systems, especially the upper urinary tract, where it plays a pivotal role in conveying urine from the kidneys to the bladder. Using computational fluid dynamics, this study aims to investigate the effect of various peristaltic parameters on the motion of an obstacle through a two-dimensional ureter. Methodologically, Incompressible Navier-Stokes equations were utilized as the fluid domain's governing equations, and the Dynamic Mesh method (DM) was employed to simulate the peristaltic and obstacle motion. The peristaltic motion was modeled by a sinusoidal contraction wave propagating alongside the ureter at the physiological speed, and the motion of the obstruction through the ureter, which is caused by the fluid forces applied on its surface, was explored using the equation of Newton's second law. Various test cases of different shapes and sizes were supposed as kidney stones to understand the influence of the peristalsis properties on the stone removal process. The results show that the motion of the kidney stone is highly influenced by the gradient pressure force applied to its surface in the fluid domain. Moreover, investigating the effects of the peristaltic physical properties on the obstacle's motion indicates that the stone's motion is dependent on these parameters. Furthermore, this analysis provides insight into the peristaltic motion effects, assisting physicians in developing new medicines to facilitate the kidney stone removal process based on its shape and size.

Research on Evaluation Indicator of Ice Rink and Curling Stone Motion for the 2022 Beijing Winter Olympic Games Based on Video Recognition Method

During curling sports, the movement of the stone is affected by the quality of the ice. Therefore, the delivery team led by the ice maker hopes that the quality of the ice surface will be stable and that the athletes will always ‘read the ice’ and pay attention to the small changes in the ice surface. This phenomenon is the charm of curling. Many friction models have been proposed to describe the regularity of the curling motion. In the curling competitions of the 2022 Beijing Winter Olympic Games, the 2021 World Wheelchair Curling Championships, and the warm-up competition before, the research team installed a video image capture system in the arena to capture and record the data of the curling motion by using the depth neural network and object tracking algorithm. Further motion data research verifies the relationship between the friction coefficient and the speed. The quality control parameter of ice rink α is proposed, which is related to the influencing factors of the ice surface temperature, the ice hardness, the size of the pebble point, and the width of the curling friction band. The quality of the curling ice rink can be evaluated accurately and comprehensively by using parameter α. Based on the relationship between the friction coefficient and the speed, a physical model of horizontal sliding of the curling stone is established, which agrees well with the results of data obtained from video acquisition. Therefore, the movement distance along the rink can be accurately predicted. This paper analyzes the relationship between the long-time (the time it takes for the curling stone to travel between the two hog lines) and the stop position and that between the long-time and the split-time (the time it takes for the curling stone to travel from the back line to the hog line). Based on this result, a ruler can be established to assist athletes in estimating the sliding distance of the stone before curling throwing. This research also studies the relationship between three factors (the sliding speed in the x-direction, the angular speed, and a tiny lateral deflection speed in the y-direction) and the deviation of the stone. At the same time, there are also some interesting phenomena of the lateral deflection of the stone, such as the relationship between the lateral deflection angle tanθ and the initial lateral speed. As a result, the prediction of the curling stone’s exact final location can be realized. In summary, this article proposes an indicator for evaluating the quality of ice rinks and a physical model of curling based on the curling friction model, which is validated by data obtained from a video capture system of the 2022 Beijing Winter Olympics. The results described above have been applied in the post-match operation of the National Aquatics Center to guide the production of Olympic-grade ice surfaces and to guide athletes to “read ice” accurately during training.

First Series Using Ultrasonic Propulsion and Burst Wave Lithotripsy to Treat Ureteral Stones.

Our goal was to test transcutaneous focused ultrasound in the form of ultrasonic propulsion and burst wave lithotripsy to reposition ureteral stones and facilitate passage in awake subjects. Adult subjects with a diagnosed proximal or distal ureteral stone were prospectively recruited. Ultrasonic propulsion alone or with burst wave lithotripsy was administered by a handheld transducer to awake, unanesthetized subjects. Efficacy outcomes included stone motion, stone passage, and pain relief. Safety outcome was the reporting of associated anticipated or adverse events. Twenty-nine subjects received either ultrasonic propulsion alone (n = 16) or with burst wave lithotripsy bursts (n = 13), and stone motion was observed in 19 (66%). The stone passed in 18 (86%) of the 21 distal ureteral stone cases with at least 2 weeks follow-up in an average of 3.9±4.9 days post-procedure. Fragmentation was observed in 7 of the burst wave lithotripsy cases. All subjects tolerated the procedure with average pain scores (0-10) dropping from 2.1±2.3 to 1.6±2.0 (P = .03). Anticipated events were limited to hematuria on initial urination post-procedure and mild pain. In total, 7 subjects had associated discomfort with only 2.2% (18 of 820) propulsion bursts. This study supports the efficacy and safety of using ultrasonic propulsion and burst wave lithotripsy in awake subjects to reposition and break ureteral stones to relieve pain and facilitate passage.

Optimization of Patient Positioning for the Sonographic Evaluation of Gallstone Impaction: Analysis of Gallbladder Orientation Based on Computed Tomography.

An important sonographic sign of cholecystitis is stone impaction in the gallbladder neck. Demonstration of stone mobility excludes impaction. The purpose of this study is to analyze the orientation of the gallbladder on computed tomography and determine the patient position most likely to facilitate stone mobility. ImageJ processing software was used to determine the x (transverse), y (anterior-posterior), and z (craniocaudal) coordinates for the gallbladder neck and fundus in 544 consecutive computed tomography examinations. The differences in the fundal and neck coordinates were used to determine the likelihood of moving a stone from the neck to the fundus for the left and right lateral decubitus positions ( x coordinates), the prone position ( y coordinates), and the upright position ( z coordinates). The coordinate with the largest difference was considered to predict the position most likely to facilitate stone motion. The difference in position of the fundus and neck was greatest in the y -, z -, and x -axis in 232 (42.6%), 194 (35.7%), and 118 (21.7%) of patients, respectively. For body mass index (BMI) less than 25 kg/m 2 , the difference was greatest in the z -axis (59.8%). For BMI greater than 25 kg/m 2 , the difference was greatest in the y -axis (47.1%). Based on their relative location, the optimal position to facilitate gallstone mobility from the gallbladder neck to fundus was most often prone (especially in high BMI patients), followed by upright (especially in low BMI patients), followed by right lateral decubitus. The left lateral decubitus position was never optimal.

Hydraulic Tests and Interpretation of Test Data for Reno Mattresses in Open Channel Flow

The efficacy of erosion control systems depends on preventing soil loss underneath and maintaining its integrity under the effects of the water flow. The paper presents the research results at the Colorado State University on the performance of double twisted wire mesh products, known as Reno Mattresses, used as soil erosion control systems. Mattresses were subjected to various flow conditions on a 10 m long flume placed on a soil layer. The performance against erosion was evaluated by assessing the effect of the stone motion inside the mattress combined with the condition of incipient soil erosion underneath, in relationship to the mattress thickness, the filling stone properties, and under variable hydraulic flow regimes. At the same time, confirming the stability obtained using the conventional tractive force design approach, the research results allowed to introduce a new performance limit based on incipient soil erosion underneath the revetment. Based on the research results, the authors propose to express the shear resistance of mattresses used as soil erosion control systems as a function of the filling stones’ size, uniformity, unit weight, mattress thickness, and the presence of vertical strengthening elements.

MP18-07 ULTRASOUND TO REPOSITION AND ACCELERATE PASSAGE OF DISTAL URETERAL STONES

You have accessJournal of UrologyStone Disease: Surgical Therapy II (MP18)1 Sep 2021MP18-07 ULTRASOUND TO REPOSITION AND ACCELERATE PASSAGE OF DISTAL URETERAL STONES M. Kennedy Hall, Jeff Thiel, Patrick C. Samson, Ross Kessler, Peter Sunaryo, Robert M. Sweet, Ian S. Metzler, Martin L. Gunn, Layla Anderson, Barbrina Dunmire, Christina Popchoi, Ravi Managuli, Bryan W. Cunitz, Barbara Burke, Adam D. Maxwell, Michael R. Bailey, Mathew D. Sorensen, Hunter Wessells, and Jonathan D. Harper M. Kennedy HallM. Kennedy Hall More articles by this author , Jeff ThielJeff Thiel More articles by this author , Patrick C. SamsonPatrick C. Samson More articles by this author , Ross KesslerRoss Kessler More articles by this author , Peter SunaryoPeter Sunaryo More articles by this author , Robert M. SweetRobert M. Sweet More articles by this author , Ian S. MetzlerIan S. Metzler More articles by this author , Martin L. GunnMartin L. Gunn More articles by this author , Layla AndersonLayla Anderson More articles by this author , Barbrina DunmireBarbrina Dunmire More articles by this author , Christina PopchoiChristina Popchoi More articles by this author , Ravi ManaguliRavi Managuli More articles by this author , Bryan W. CunitzBryan W. Cunitz More articles by this author , Barbara BurkeBarbara Burke More articles by this author , Adam D. MaxwellAdam D. Maxwell More articles by this author , Michael R. BaileyMichael R. Bailey More articles by this author , Mathew D. SorensenMathew D. Sorensen More articles by this author , Hunter WessellsHunter Wessells More articles by this author , and Jonathan D. HarperJonathan D. Harper More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002003.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The feasibility of ultrasonic propulsion and burst wave lithotripsy (BWL) to noninvasively reposition distal ureteral stones to facilitate passage and relieve pain was tested. METHODS: Patients presenting to the kidney stone clinic or emergency department (ED) with a distal ureteral stone were recruited after standard of care pain management. To attempt to move the stone, 10 subjects underwent ultrasonic propulsion (lower amplitude, longer duration bursts) alone, and 10 subjects also received intermittent BWL (higher amplitude, shorter duration bursts). All participants were awake without anesthesia and underwent:· a screening ultrasound to ensure the stone was visible· a pain assessment pre- and post-procedure · contact once a week for three weeks to assess for adverse events· follow-up imaging and chart review within 12 weeksSubjects were sub-categorized based on whether their stone was acute or chronic (≤10 days or >10 days from their ED visit, respectively). RESULTS: Demographic data and effectiveness outcomes are presented in Tables 1 and 2. Overall, 93% of acute stones passed in an average of 3.6 days post-procedure. There was no control group, but Table 2 includes published passage rates and times for potentially similar untreated groups as reference. Stone motion was observed in 16 of 20 cases, including a stone pushed into the bladder, ureteral jets were observed following propulsion bursts in 9 of 20 cases and fragmentation was observed in 3 of 10 BWL cases. Pain reduced post-procedure in 10 of 20 subjects, while pain increased in only one subject; although, the average score was low prior to treatment, and the average decrease was not statistically significant (p=0.13). Adverse events were limited to slight reddening of the skin (N=6), hematuria on only the initial urination post-procedure (BWL only, N=3), and a mild sensation, akin to a pinprick, on fewer than 10 of 620 propulsion bursts among 3 subjects. CONCLUSIONS: This feasibility study showed the potential for facilitating stone passage of distal ureteral stones and relieving pain with ultrasonic propulsion and BWL. Source of Funding: Work supported by NASA, NIH P01 DK043881, and NIH K01 DK104854 © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e320-e320 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information M. Kennedy Hall More articles by this author Jeff Thiel More articles by this author Patrick C. Samson More articles by this author Ross Kessler More articles by this author Peter Sunaryo More articles by this author Robert M. Sweet More articles by this author Ian S. Metzler More articles by this author Martin L. Gunn More articles by this author Layla Anderson More articles by this author Barbrina Dunmire More articles by this author Christina Popchoi More articles by this author Ravi Managuli More articles by this author Bryan W. Cunitz More articles by this author Barbara Burke More articles by this author Adam D. Maxwell More articles by this author Michael R. Bailey More articles by this author Mathew D. Sorensen More articles by this author Hunter Wessells More articles by this author Jonathan D. Harper More articles by this author Expand All Advertisement Loading ...

Quantitative Assessment of Effectiveness of Ultrasonic Propulsion of Kidney Stones.

Purpose: Ultrasonic propulsion is an investigative modality to noninvasively image and reposition urinary stones. Our goals were to test safety and effectiveness of new acoustic exposure conditions from a new transducer, and to use simultaneous ureteroscopic and ultrasonic observation to quantify stone repositioning. Materials and Methods: During operation, ultrasonic propulsion was applied transcutaneously, whereas stone targets were visualized ureteroscopically. Exposures were 350 kHz frequency, ≤200 W/cm2 focal intensity, and ≤3-second bursts per push. Ureteroscope and ultrasound (US) videos were recorded. Video clips with and without stone motion were randomized and scored for motion ≥3 mm by independent reviewers blinded to the exposures. Subjects were followed with telephone calls, imaging, and chart review for adverse events. Results: The investigative treatment was used in 18 subjects and 19 kidneys. A total of 62 stone targets were treated ranging in size from a collection of "dust" to 15 mm. Subjects received an average of 17 ± 14 propulsion bursts (per kidney) for a total average exposure time of 40 ± 40 seconds. Independent reviewers scored at least one stone movement ≥3 mm in 18 of 19 kidneys (95%) from the ureteroscope videos and in 15 of 19 kidneys (79%) from the US videos. This difference was probably because of motion out of the US imaging plane. Treatment repositioned stones in two cases that would have otherwise required basket repositioning. No serious adverse events were observed with the device or procedure. Conclusions: Ultrasonic propulsion was shown to be safe, and it effectively repositioned stones in 95% of kidneys despite positioning and access restrictions caused by working in an operating room on anesthetized subjects.

“Sometimes a Bee Can Move an Ox”: Biblical Epics and One Man's Quest to Promote Jewish Values in Blacklist-Era Hollywood

In the 1950s, the top American Jewish organizations chose a single man, John Stone, to represent their collective interests in Hollywood. Over the course of the decade, Stone's Motion Picture Project sought to prevent antisemitism on film and to inspire the creation of positive Jewish characters. Negotiating the cultural politics of the era, however, resulted in an increasing tendency to favor depictions of biblical Jews over contemporary American ones. In a strange twist, Stone endorsed no film with as much zeal asBen-Hur, a New Testament celebration of Jesus. By following Stone's tortuous attempts to navigate Cold War controversies, and by casting new light on the phenomenal success of biblical epics in the 1950s, this essay suggests that at the heart of postwar popular culture was a shift toward a particular discourse of liberal humanism.

Quantification of the Range of Motion of Kidney and Ureteral Stones During Shockwave Lithotripsy in Conscious Patients.

Effective shockwave lithotripsy requires accurate targeting of the stone throughout the course of treatment. Stone movement secondary to respiratory movement can make this more difficult. In vitro work has shown that stone motion outside the focal region reduces the efficacy of stone fragmentation; however, there are few clinical data on the degree of stone movement in patients during treatment. To investigate this, X-ray fluoroscopic images of the kidney and ureteral stones at the upper and lower limits of the normal respiratory cycle were acquired during shock wave lithotripsy of 58 conscious patients, and stone excursion was calculated from these images. In addition, the respiration rate and patient perceived pain were recorded during the course of the treatment. It was found that stone motion secondary to respiration was 7.7 ± 2.9 mm for kidney stones and 3.6 ± 2.1 mm for ureteral stones-less than has been reported in studies with anesthetized patients. There was no significant change of motion over the course of treatment although pain was found to increase. These data suggest that stone motion in conscious patients is less than in anesthetized patients. Furthermore, it suggests that lithotripters with focal regions of 8 mm or greater should not suffer from a marked drop in fragmentation efficiency due to stone motion.

Bubble Dynamics in Laser Lithotripsy

Laser lithotripsy is a medical procedure for fragmentation of urinary stones with a fiber guided laser pulse of several hundred microseconds long. Using high-speed photography, we present an in-vitro study of bubble dynamics and stone motion induced by Ho:YAG laser lithotripsy. The experiments reveal that detectable stone motion starts only after the bubble collapse, which we relate with the collapse-induced liquid flow. Additionally, we model the bubble formation and dynamics using a set of 2D Rayleigh-Plesset equations with the measured laser pulse profile as an input. The aim is to reduce stone motion through modification of the temporal laser pulse profile, which affects the collapse scenario and consequently the remnant liquid motion.

A non-axisymmetric, elongated pressure distribution in the lithotripter focal plane enhances stone comminution in vitro during simulated respiratory motion

A challenge in clinical shock wave lithotripsy (SWL) is stone translation due to a patient’s respiratory motion, in a direction perpendicular to shockwave propagation, which may negatively affect stone comminution while increasing the risk of tissue injury. We have developed a method using external masks and a modified lens geometry to transform the axisymmetric pressure distribution in the focal plane of an electromagnetic lithotripter into a non-axisymmetric elliptical distribution. At equivalent acoustic pulse energy (46 mJ), the peak pressure was reduced from 44 MPa to 38 MPa while the −6 dB focal width was increased from 7.4 mm for the original to 11.7 mm (major axis) and 7.9 mm (minor axis) of the modified field. In vitro stone comminution was performed in a tube holder (d = 14 mm) using a translation pattern with 12 breaths per minute and 15 mm in excursion distance. Stone comminution after 1000 shocks are 71.2 ± 4.4% and 65.2 ±8.3% (p < 0.05) along the major- and minor-axis of the modified field, respectively, compared to 62.6 ± 7.2% for the original axisymmetric field. These results suggest that an elongated pressure field aligned along the direction of stone motion may enhance stone comminution in SWL. [Work supported by the NIH and the NSF GRFP.]

Comparative study of the effect of several trains on the rotation motion of ballast stones

The ballast pick-up (or ballast train-induced-wind erosion (BTE)) phenomenon is a limiting factor for the maximum allowed operational train speed. The determination of the conditions for the initiation of the motion of the ballast stones due to the wind gust created by high-speed trains is critical to predict the start of ballast pick-up because, once the motion is initiated, a saltation-like chain reaction can take place. The aim of this paper is to present a model to evaluate the effect of a random aerodynamic impulse on stone motion initiation, and an experimental study performed to check the capability of the proposed model to classify trains by their effect on the ballast due to the flow generated by the trains. A measurement study has been performed at kp 69 + 500 on the Madrid – Barcelona High Speed Line. The obtained results show the feasibility of the proposed method, and contribute to a technique for BTE characterization, which can be relevant for the development of train interoperability standards.

E70 Kidney stone motion is less than 10 mm during shockwave lithotripsy

E70 Kidney stone motion is less than 10 mm during shockwave lithotripsy

Quantitative Assessment of Shockwave Lithotripsy Accuracy and the Effect of Respiratory Motion

Effective stone comminution during shockwave lithotripsy (SWL) is dependent on precise three-dimensional targeting of the shockwave. Respiratory motion, imprecise targeting or shockwave alignment, and stone movement may compromise treatment efficacy. The purpose of this study was to evaluate the accuracy of shockwave targeting during SWL treatment and the effect of motion from respiration. Ten patients underwent SWL for the treatment of 13 renal stones. Stones were targeted fluoroscopically using a Healthtronics Lithotron (five cases) or Dornier Compact Delta II (five cases) shockwave lithotripter. Shocks were delivered at a rate of 1 to 2 Hz with ramping shockwave energy settings of 14 to 26 kV or level 1 to 5. After the low energy pretreatment and protective pause, a commercial diagnostic ultrasound (US) imaging system was used to record images of the stone during active SWL treatment. Shockwave accuracy, defined as the proportion of shockwaves that resulted in stone motion with shockwave delivery, and respiratory stone motion were determined by two independent observers who reviewed the ultrasonographic videos. Mean age was 51 ± 15 years with 60% men, and mean stone size was 10.5 ± 3.7 mm (range 5-18 mm). A mean of 2675 ± 303 shocks was delivered. Shockwave-induced stone motion was observed with every stone. Accurate targeting of the stone occurred in 60% ± 15% of shockwaves. US imaging during SWL revealed that 40% of shockwaves miss the stone and contribute solely to tissue injury, primarily from movement with respiration. These data support the need for a device to deliver shockwaves only when the stone is in target. US imaging provides real-time assessment of stone targeting and accuracy of shockwave delivery.

Acoustic radiation force applied to the treatment of lower pole kidney stones

Lower pole kidney stones have lower rates of clearance after shock wave lithotripsy or ureteroscopy compared to other stone locations. Residual stone fragments, post treatment, often lead to additional morbidity and secondary surgery. We describe the use of acoustic radiation force created by transcutaneous focused ultrasound to manipulate the location of stone fragments within the collecting system in order to facilitate their passage. Artificial and human stones were placed in the lower pole of kidneys of a porcine animal model. An open architecture, software based diagnostic ultrasound system and scanhead were modified to produce roughly 100 μs pulses of up to 16 MPa peak positive pressure in water. Stone motion was observed in real-time with simultaneous imaging through the same scanhead and with fluoroscopy. All stones were seen to move. Stone velocities were on the order of 1 cm/s. Stone displacement distance was up to 3 cm, and operators could generally control the direction of stone movement. No evidence of thermal necrosis or mechanical damage of renal tissue was observed. Thus acoustic radiation force can be used to facilitate lower pole stone fragment clearance. [Work supported by NIH DK43881, DK086371, DK092197, and NSBRI through NASA NCC 9-58.]

Real‐time tracking of renal calculi displaced by the radiation force of focused ultrasound.

An area of active research involves using the radiation force of ultrasound to expel small kidney stones or fragments from the kidney. The goal of this work is real‐time motion tracking for visual feedback to the user and automated adaptive pushing as the stone moves. Algorithms have been designed to track stone movement during patient respiration but the challenge here is to track the stone motion relative to tissue. A new algorithm was written in MATLAB and implemented on an open‐architecture, software‐based ultrasound system. The algorithm was first trained then implemented in real‐time on B‐mode IQ data recorded from phantom experiments and animal studies. The tracking algorithm uses an ensemble of image processing techniques (2‐D cross‐correlation, phase correlation, and feature‐edge detection) to overlay color on the stone in the real‐time images and to assign a color to indicate the confidence in the identification of the stone. Camera images as well as ultrasound images showed that the system was able to locate a moving stone, re‐target, and apply a new focused push pulse at that location. [Work supported by NIH DK43881, NIH DK086371, and NSBRI through NASA NCC 9‐58].

Clinical assessment of shockwave lithotripsy accuracy.

Kidney stone movement primarily due to patient respiration compromises shock wave lithotripsy (SWL) targeting and efficacy. The objective of this study is to describe the use of B‐mode ultrasound to evaluate the accuracy of targeting during SWL. Patients undergoing electrohydraulic SWL were enrolled into this institutionally approved research study. A commercial diagnostic ultrasound imaging system, either Philips HDI 5000 or iU‐22, was used to intermittently visualize and detect any shockwave‐induced motion of the stone during 1–3 min periods. Four patients (mean age 52.7) underwent treatment of seven renal stones with mean individual stone size of 10.41 ± 4.5 mm. A mean of 2937 shocks (range 2750–3000) were delivered at a rate of 1–2 Hz and charging voltage of 14–26 kV. Stone oscillation or jumping at the exact time of individual shock delivery was visualized with ultrasound: no stones completely failed to move. Accurate alignment, as interpreted by positive stone motion, occurred in a mean of 50 ± 20.4% of shockwaves. Ultrasound imaging represents a method of real‐time assessment of accuracy in SWL and may provide the basis for devices to control targeting so that shockwaves are only delivered when the stone is in focus. [Work supported by NIH DK43881 and DK086371.]

1826 PROTOTYPE FOR ULTRASONIC EXPULSION OF KIDNEY STONES

You have accessJournal of UrologyStone Disease: New Technology/SWL, Ureteroscopic or Percutaneous Stone Removal1 Apr 20111826 PROTOTYPE FOR ULTRASONIC EXPULSION OF KIDNEY STONES Anup Shah, Jonathan D. Harper, Bryan W. Cunitz, John C. Kucewicz, Yak-Nam Wang, Julianna Simon, Peter J. Kaczkowski, and Michael R. Bailey Anup ShahAnup Shah Seattle, WA More articles by this author , Jonathan D. HarperJonathan D. Harper Seattle, WA More articles by this author , Bryan W. CunitzBryan W. Cunitz Seattle, WA More articles by this author , John C. KucewiczJohn C. Kucewicz Seattle, WA More articles by this author , Yak-Nam WangYak-Nam Wang Seattle, WA More articles by this author , Julianna SimonJulianna Simon Seattle, WA More articles by this author , Peter J. KaczkowskiPeter J. Kaczkowski Seattle, WA More articles by this author , and Michael R. BaileyMichael R. Bailey Seattle, WA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.1845AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Residual fragments remain in up to 65% of patients post shockwave lithotripsy and 50% post ureteroscopic treatment for lower pole stones and require intervention in 10% of patients within 1 year. A 2nd-generation device has been developed to improve residual stone detection using diagnostic ultrasound and non-invasively expel residual fragments from the kidney. METHODS A Verasonics ultrasound imager (A) equipped with a standard imaging probe was reprogrammed to detect stones. An algorithm was invented to specifically detect stones and display them as colored objects (B). A graphical interface allowed the user to select the stone on the image and apply focused ultrasound to move the stone via generation of an acoustic radiation force. Focused ultrasound was applied to a bead on string in a water tank as well as to human stones (<5 mm) implanted in the lower pole of a live porcine model via retrograde ureteroscopy. Threshold for thermal and mechanical injury was measured by blinded histological analysis. RESULTS Comparison images to B-mode ultrasound and fluoroscopy show excellent accuracy and clear contrast of the newly patented coloring imaging algorithm. The in-vitro bead was visually observed to move under focused ultrasound. Even with progressive manual displacement of the bead, the Verasonics system continuously tracked and caused bead movement in real time. In the live porcine model stones were expelled from the lower pole to the ureteropelvic junction in seconds to minutes using pulses at 1% duty cycle and 8W total acoustic power (C). Neither full power (80W) nor 100% duty cycle alone for 10 minutes caused injury. 80W at 10% duty cycle was the threshold for mechanical injury, disrupted vessels, and extravasation. 10W at 100% duty cycle was the threshold for thermal coagulation. CONCLUSIONS A new stone repositioning prototype allows for improved stone detection, real time stone motion tracking, and stone expulsion from the lower pole. The system moved stones transcutaneously within live porcine kidneys using an exposure significantly below the measured threshold levels for injury. These are significant advances from our discovery of the capability to reposition stones previously reported and set the stage for clinical trials. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e732-e733 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Anup Shah Seattle, WA More articles by this author Jonathan D. Harper Seattle, WA More articles by this author Bryan W. Cunitz Seattle, WA More articles by this author John C. Kucewicz Seattle, WA More articles by this author Yak-Nam Wang Seattle, WA More articles by this author Julianna Simon Seattle, WA More articles by this author Peter J. Kaczkowski Seattle, WA More articles by this author Michael R. Bailey Seattle, WA More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Empirical design of scour protections around monopile foundations: Part 1: Static approach

Together with new opportunities, offshore wind farms raise new engineering challenges. An important aspect relates to the erosion of bottom material around the foundation of the wind turbines, caused by the local increase of the wave and current induced flow velocities by the pile's presence. Typically, the expected scour has a considerable impact on the stability and dynamic behavior of the wind turbine and a scour protection is placed to avoid erosion of the soil close to the foundation. Although much experience exists on the design of scour protections around bridge piers (which are placed in a current alone situation), at present, little design guidelines exist for the specific case of a scour protection around a monopile foundation subjected to a combined wave and current loading. This paper describes the derivation of a static design formula to calculate the required stone size for a scour protection around a monopile foundation in a combined wave and current climate. Due to the difficult physical processes involved in flow disturbance and displacement of bed protection material at the base of a foundation, the formula is based on the results of an experimental model study which is described in this paper. A linear relationship was found between the critical bed shear-stress τ cr and the bed shear-stress caused by current τ c and waves τ w , respectively. When applying the formula for a typical situation in the North Sea, a significant reduction of the required stone size is obtained, compared to existing design criteria. In part 2, following this paper ( De Vos et al., in preparation), an optimization of the design procedure is obtained by allowing limited stone motion for top layer stones. This is obtained by adding a damage factor to the design formula, which leads to significantly smaller stone diameters and thus a more economical approach.

Novel ultrasound method to reposition kidney stones

The success of surgical management of lower pole stones is principally dependent on stone fragmentation and residual stone clearance. Choice of surgical method depends on stone size, yet all methods are subjected to post-surgical complications resulting from residual stone fragments. Here we present a novel method and device to reposition kidney stones using ultrasound radiation force delivered by focused ultrasound and guided by ultrasound imaging. The device couples a commercial imaging array with a focused annular array transducer. Feasibility of repositioning stones was investigated by implanting artificial and human stones into a kidney-mimicking phantom that simulated a lower pole and collecting system. During experiment, stones were located by ultrasound imaging and repositioned by delivering short bursts of focused ultrasound. Stone motion was concurrently monitored by fluoroscopy, ultrasound imaging, and video photography, from which displacement and velocity were estimated. Stones were seen to move immediately after delivering focused ultrasound and successfully repositioned from the lower pole to the collecting system. Estimated velocities were on the order of 1 cm/s. This in vitro study demonstrates a promising modality to facilitate spontaneous clearance of kidney stones and increased clearance of residual stone fragments after surgical management.