2008 Annual Meeting Abstracts

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A Novel Method for Accurate Shock Wave Lithotripsy of Moving Kidney Stones; In Vitro Evaluation
Yousry Faragalla*¹, Botros Edward Semon*¹, Anton Al komos Abdel Maseeh*¹, Eman Sawires*¹, Ramez Andrawis², Thomas W Jarrett^2
1P.O. Box 1500, Lorton, VA;²The George Washington University, Washington, DC

Introduction:
Shock Wave Lithotripsy (SWL), a standard treatment for kidney stones, targets the stones most effectively when they are positioned at the shock wave’s focal point. However, kidney stones are moving targets due to respiration and thus do not remain constantly at this optimal location. Current SWL systems generate shock waves indiscriminately, with only a small fraction of the waves actually contacting the stone while it is at a wave’s focal point.
To address this problem, we developed the FTS (patent pending) software that, when used with SWL, controls the shock waves that are generated only when the kidney stones appear at the said focal point.
Methods:
We placed a gypsum stone in a net basket, then positioned the basket inside a custom-designed water container. We attached the stone to a small motor simulating respiratory motion, used a TWINHEADS TH-103 lithotripter and ultrasound imaging for stone localization. As a control, we used a comparable stone treated by SWL without FTS software.
Results:
The FTS software accurately identified the focal point of the shock waves as well as the stone was positioned movement. The software successfully limited the generation of shock waves to only those time intervals when the stone was positioned at the said focal point. Treatment using SWL and FTS software completely disintegrated the stone at 560 shocks, compared to 1,780 shocks with SWL alone.
Conclusions:
FTS software increases the accuracy of SWL in vitro. Further studies are needed to confirm this finding in clinical setting.

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