Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter.

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2014-04-01

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Abstract

The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The -6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters.

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electromagnetic lithotripter, lens modification, stone fragmentation, Animals, Electromagnetic Phenomena, Equipment Design, Female, Lenses, Lithotripsy, Motion, Respiration, Skin, Sus scrofa

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https://hdl.handle.net/10161/8403

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10.1073/pnas.1319203111

Publication Info

Neisius, Andreas, Nathan B Smith, Georgy Sankin, Nicholas John Kuntz, John Francis Madden, Daniel E Fovargue, Sorin Mitran, Michael Eric Lipkin, et al. (2014). Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter. Proc Natl Acad Sci U S A, 111(13). pp. E1167–E1175. 10.1073/pnas.1319203111 Retrieved from https://hdl.handle.net/10161/8403.

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Scholars@Duke

Madden

John Francis Madden

Associate Professor of Pathology
Lipkin

Michael Eric Lipkin

Cary N. Robertson, MD, Associate Professor
Simmons

Walter Neal Simmons

Gendell Family Professor of the Practice
Preminger

Glenn Michael Preminger

James F. Glenn, M.D. Distinguished Professor of Urology
  1. Minimally invasive management of urologic diseases
    2. Minimally invasive management of renal and ureteral stones
    3. Medical management of nephrolithiasis
    4. Bioeffects of shock wave lithotripsy
    5. Basic physics of shock wave lithotripsy
    6. Intracorporeal lithotripsy for stone fragmentation
    7. Minimally invasive management of urinary tract obstruction, including ureteropelvic junction obstruction and ureteral strictures
    8. Enhanced imaging modalities for minimally invasive surgery
    9. Digital video imaging during endoscopic surgery
    10. 3-D imaging modalities for minimally invasive surgery
    11. Holmium laser applications in urology
Zhong

Pei Zhong

Professor in the Thomas Lord Department of Mechanical Engineering and Materials Science

My research focuses on engineering and technology development with applications in the non-invasive or minimally invasive treatment of kidney stone disease via shock wave and laser lithotripsy, high-intensity focused ultrasound (HIFU) and immunotherapy for cancer treatment, acoustic and optical cavitation, and ultrasound neuromodulation via sonogenetics. 

We are taking an integrated and translational approach that combines fundamental research with engineering and applied technology development to devise novel and enabling ultrasonic, optical, and mechanical tools for a variety of clinical applications. We are interested in shock wave/laser-fluid-bubble-solid interaction, and resultant mechanical and thermal fields that lead to material damage and removal.  We also investigate the stress response of biological cell and tissue induced by cavitation and ultrasound exposure, mediated through mechanosensitive ion channels, such as Piezo 1. Our research activities are primarily supported by NIH and through collaborations with the medical device industry.

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