Browsing by Author "Wang, Yak-Nam"

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    Comparison of Tissue Injury from Focused Ultrasonic Propulsion of Kidney Stones Versus Extracorporeal Shock Wave Lithotripsy
    (Elsevier, 2014-01) Connors, Bret A.; Evan, Andrew P.; Blomgren, Philip M.; Hsi, Ryan S.; Harper, Jonathan D.; Sorensen, Mathew D.; Wang, Yak-Nam; Simon, Julianna C.; Paun, Marla; Starr, Frank; Cunitz, Bryan W.; Bailey, Michael R.; Lingeman, James E.; Department of Anatomy & Cell Biology, IU School of Medicine
    Purpose Focused ultrasonic propulsion is a new non-invasive technique designed to move kidney stones and stone fragments out of the urinary collecting system. However, the extent of tissue injury associated with this technique is not known. As such, we quantitated the amount of tissue injury produced by focused ultrasonic propulsion under simulated clinical treatment conditions, and under conditions of higher power or continuous duty cycles, and compared those results to SWL injury. Materials and Methods A human calcium oxalate monohydrate stone and/or nickel beads were implanted (with ureteroscopy) into 3 kidneys of live pigs (45–55 kg) and repositioned using focused ultrasonic propulsion. Additional pig kidneys were exposed to SWL level pulse intensities or continuous ultrasound exposure of 10 minutes duration (ultrasound probe either transcutaneous or on the kidney). These kidneys were compared to 6 kidneys treated with an unmodified Dornier HM3 Lithotripter (2400 shocks, 120 SWs/min and 24 kV). Histological analysis was performed to assess the volume of hemorrhagic tissue injury created by each technique (% functional renal volume, FRV). Results SWL produced a lesion of 1.56±0.45% FRV. Ultrasonic propulsion produced no detectable lesion with the simulated clinical treatment. A lesion of 0.46±0.37% FRV or 1.15±0.49% FRV could be produced if excessive treatment parameters were used while the ultrasound probe was placed on the kidney. Conclusions Focused ultrasonic propulsion produced no detectable morphological injury to the renal parenchyma when using clinical treatment parameters and produced injury comparable in size to SWL when using excessive treatment parameters.
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    Effect of Carbon Dioxide on the Twinkling Artifact in Ultrasound Imaging of Kidney Stones: A Pilot Study
    (Elsevier, 2017-05) Simon, Julianna C.; Wang, Yak-Nam; Cunitz, Bryan W.; Thiel, Jeffrey; Starr, Frank; Liu, Ziyue; Bailey, Michael R.; Biostatistics, School of Public Health
    Bone demineralization, dehydration and stasis put astronauts at increased risk of forming kidney stones in space. The color-Doppler ultrasound "twinkling artifact," which highlights kidney stones with color, can make stones readily detectable with ultrasound; however, our previous results suggest twinkling is caused by microbubbles on the stone surface which could be affected by the elevated levels of carbon dioxide found on space vehicles. Four pigs were implanted with kidney stones and imaged with ultrasound while the anesthetic carrier gas oscillated between oxygen and air containing 0.8% carbon dioxide. On exposure of the pigs to 0.8% carbon dioxide, twinkling was significantly reduced after 9-25 min and recovered when the carrier gas returned to oxygen. These trends repeated when pigs were again exposed to 0.8% carbon dioxide followed by oxygen. The reduction of twinkling caused by exposure to elevated carbon dioxide may make kidney stone detection with twinkling difficult in current space vehicles.
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    Focused Ultrasonic Propulsion of Kidney Stones
    (Mary Ann Liebert, Inc., 2013-12-09) Sorensen, Mathew D.; Bailey, Michael R.; Hsi, Ryan S.; Cunitz, Bryan W.; Simon, Julianna; Wang, Yak-Nam; Dunmire, Barbrina L.; Paun, Marla; Starr, Frank; Lu, Wei; Evan, Andrew P.; Harper, Jonathan D.; Anatomy and Cell Biology, School of Medicine
    Introduction: Our research group is studying a noninvasive transcutaneous ultrasound device to expel small kidney stones or residual post-treatment stone fragments from the kidney.1-3 The purpose of this study was to evaluate the efficacy and safety of ultrasonic propulsion in a live porcine model. Materials and Methods: In domestic female swine (50-60 kg), human stones (calcium oxalate monohydrate) and metalized glass beads (2-8 mm) were ureteroscopically implanted.4 Target stones and beads were placed in the lower half of the kidney and a reference bead was placed in the upper pole. Ultrasonic propulsion was achieved through a single ultrasound system that allowed targeting, stone propulsion, and ultrasound imaging using a Philips HDI C5-2 commercial imaging transducer and a Verasonics diagnostic ultrasound platform. Stone propulsion was achieved through the delivery of 1-second bursts of focused, ultrasound pulses, which consist of 250 finely focused pulses 0.1 milliseconds in duration. Stone propulsion was then observed using fluoroscopy, ultrasound, and visually with the ureteroscope. The kidneys were then perfusion-fixed with glutaraldehyde, embedded in paraffin, sectioned, and stained. Samples were histologically scored for injury by a blinded independent expert. Using the same pulsing scheme, while varying acoustic intensities, an injury threshold and patterns of injury were determined in additional pigs.5,6 Results: Stones were successfully implanted in 14 kidneys. Overall, 17 of 26 (65)% stones/beads were moved the entire distance to the renal pelvis, ureteropelvic junction (UPJ), or proximal ureter. The average procedure time for successfully repositioned stones was 14.2±7.9 minutes with 23±16 push bursts. No gross or histologic damage was identified from the ultrasound propulsion procedure. Under this pulsing scheme, a maximum exposure of 2400 W/cm2 was delivered during each treatment. An intensity threshold of 16,620 W/cm2 was determined at which, above this level, tissue injury consistent with emulsification, necrosis, and hemorrhage appeared to be dose dependent. Conclusions: Ultrasonic propulsion is effective with most stones being relocated to the renal pelvis, UPJ, or proximal ureter in a timely fashion. The procedure appears safe with no evidence of injury. The acoustic intensities delivered at maximum treatment settings are well below the threshold at which injury is observed. The angle and alignment of directional force are the most critical factors determining the efficacy of stone propulsion. We are now pursuing FDA approval for a human feasibility study. No competing financial interests exist. Runtime of video: 5 mins 44 secs.
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    An in vivo demonstration of efficacy and acute safety of burst wave lithotripsy using a porcine model
    (Acoustical Society of America, 2019-02-06) Wang, Yak-Nam; Kreider, Wayne; Hunter, Chris; Cunitz, Bryan W.; Thiel, Jeff; Starr, Frank; Dai, Jessica C.; Nazari, Yasser; Lee, Donghoon; Williams, James C.; Bailey, Micheal R.; Maxwell, Adam D.; Anatomy and Cell Biology, School of Medicine
    Burst wave lithotripsy (BWL) is a new non-invasive method for stone comminution using bursts of sub-megahertz ultrasound. A porcine model of urolithiasis and techniques to implement BWL treatment has been developed to evaluate its effectiveness and acute safety. Six human calcium oxalate monohydrate stones (6–7 mm) were hydrated, weighed, and surgically implanted into the kidneys of three pigs. Transcutaneous stone treatments were performed with a BWL transducer coupled to the skin via an external water bath. Stone targeting and treatment monitoring were performed with a co-aligned ultrasound imaging probe. Treatment exposures were applied in three 10-minute intervals for each stone. If sustained cavitation in the parenchyma was observed by ultrasound imaging feedback, treatment was paused and the pressure amplitude was decreased for the remaining time. Peak negative focal pressures between 6.5 and 7 MPa were applied for all treatments. After treatment, stone fragments were removed from the kidneys. At least 50% of each stone was reduced to <2 mm fragments. 100% of four stones were reduced to <4 mm fragments. Magnetic resonance imaging showed minimal injury to the functional renal volume. This study demonstrated that BWL could be used to effectively fragment kidney stones with minimal injury.
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    Update on clinical trials of kidney stone repositioning and preclinical results of stone breaking with one system
    (Acoustical Society of America, 2018-12-21) Bailey, Michael R.; Wang, Yak-Nam; Kreider, Wayne; Dai, Jessica C.; Cunitz, Bryan W.; Harper, Jonathan D.; Chang, Helena; Sorensen, Mathew D.; Liu, Ziyue; Levy, Oren; Dunmire, Barbrina; Maxwell, Adam D.; Biostatistics, School of Public Health
    Our goal is an office-based, handheld ultrasound system to target, detach, break, and/or expel stones and stone fragments from the urinary collecting system to facilitate natural clearance. Repositioning of stones in humans (maximum 2.5 MPa, and 3-second bursts) and breaking of stones in a porcine model (maximum 50 cycles, 20 Hz repetition, 30 minutes, and 7 MPa peak negative pressure) have been demonstrated using the same 350-kHz probe. Repositioning in humans was conducted during surgery with a ureteroscope in the kidney to film stone movement. Independent video review confirmed stone movements (≥ 3 mm) in 15 of 16 kidneys (94%). No serious or unanticipated adverse events were reported. Experiments of burst wave lithotripsy (BWL) effectiveness on breaking human stones implanted in the porcine bladder and kidney demonstrated fragmentation of 8 of 8 stones on post mortem dissection. A 1-week survival study with the BWL exposures and 10 specific-pathogen-free pigs, showed all findings were within normal limits on clinical pathology, hematology, and urinalysis. These results demonstrate that repositioning of stones with ultrasonic propulsion and breaking of stones with BWL are safe and effective.