Browsing by Author "Schaefer, Ray B."

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    Evaluation of an experimental electrohydraulic discharge device for extracorporeal shock wave lithotripsy: Pressure field of sparker array
    (Acoustical Society of America, 2017-11) Li, Guangyan; Connors, Bret A.; Schaefer, Ray B.; Gallagher, John J.; Evan, Andrew P.; Anatomy and Cell Biology, School of Medicine
    In this paper, an extracorporeal shock wave source composed of small ellipsoidal sparker units is described. The sparker units were arranged in an array designed to produce a coherent shock wave of sufficient strength to fracture kidney stones. The objective of this paper was to measure the acoustical output of this array of 18 individual sparker units and compare this array to commercial lithotripters. Representative waveforms acquired with a fiber-optic probe hydrophone at the geometric focus of the sparker array indicated that the sparker array produces a shock wave (P+ ∼40-47 MPa, P- ∼2.5-5.0 MPa) similar to shock waves produced by a Dornier HM-3 or Dornier Compact S. The sparker array's pressure field map also appeared similar to the measurements from a HM-3 and Compact S. Compared to the HM-3, the electrohydraulic technology of the sparker array produced a more consistent SW pulse (shot-to-shot positive pressure value standard deviation of ±4.7 MPa vs ±3.3 MPa).
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    Preliminary Report on Stone Breakage and Lesion Size Produced by a New Extracorporeal Electrohydraulic (Sparker Array) Discharge Device
    (Elsevier, 2018) Connors, Bret A.; Schaefer, Ray B.; Gallagher, John J.; Johnson, Cynthia D.; Li, Guangyan; Handa, Rajash K.; Evan, Andrew P.; Anatomy and Cell Biology, School of Medicine
    Objective To determine if an innovative extracorporeal electrohydraulic shock wave device (sparker array) can effectively fracture artificial stones in vitro and in vivo, and if sparker array treatment produces a renal lesion in our pig model of lithotripsy injury. Results of these experiments will be used to help evaluate the suitability of this device as a clinical lithotripter. Methods Utracal-30 artificial stones were placed in a holder at the focus of the sparker array and treated with 600 shock waves (21.6 kV, 60 shocks/min). Stone fragments were collected, dried and weighed to determine stone breakage. In vivo stone breakage entailed implanting stones into pigs. These stones were treated with 600 or 1200 shock waves and the fragments collected for analysis. Lesion analysis consisted of treating the left kidney of pigs with 1200 or 2400 shock waves and quantitating the hemorrhagic lesion. Results In vitro, 71±2% of each artificial stone was fractured to < 2 mm in size. In vivo stone breakage averaged 63%. Renal injury analysis revealed that only 1 out of 7 kidneys showed evidence of hemorrhagic injury in the treated area. Conclusions The sparker array consistently comminuted artificial stones demonstrating its ability to fracture stones like other lithotripters. Also, the sparker array caused little to no renal injury at the settings used in this study. These findings suggest further research is warranted to determine the potential of this device as a clinical lithotripter.