![]() ![]() Using PVDF, the pressure values recorded are "smaller" compared to old Piezoelectric Crystal sensors, but obviously this is are more accurate and "real" values. Some confusion existed in the past regarding the numerical value of this Pressure at F2.ĭue to specific conditions of the Shock Waves, the measurements done with the older Piezoelectric Crystal sensors lead to erroneous high values of pressure (above thousand bars).ĭuring the last years a new precise sensor made of a membrane of Poly Vinyl Duo Fluoride (PVDF) was developed and adopted by FDA as the only one to be used in Pressure measurements (Ref 2). Traditionally the Peak Bar Pressure at F2 is the first parameter considered as an indicator of the available energy of a lithotripter and, therefore, has served as a first indicator of the efficiency of the system. In order to compare the various systems offered, Urologists analyze their technical specifications to evaluate their performance. Various lithotripters using different Shock Wave technologies are currently offered to treat stones in the urinary tract. This may help to explain why usually the electromagnetic lithotripters require much more shocks to break stones and have larger retreatment rates. The Average Truncated Area is 2.35 times bigger and the Average Truncated Volume is 5 times bigger in Big Focus Lithotripters compared to Small Focus ones. The Average Focal Cross Section for Large Focus lithotripters is 5 times bigger than the small ones. The results show two categories of Lithotripters:Ī) Large Focus: Dornier HM-3, Medstone STS-T, Direx Tripter Compact and Medispec Econolith.ī) Small Focus: All electromagnetic lithotripters, plus Edap Praktis and the Healthronics Lithotron. The Focal Cross Section at F2, the Truncated Focal Area and Volume are 3 new tools which allow a more accurate evaluation of the Shock Wave characteristics and efficiency of different lithotripters.Įleven currently used lithotripters including the Dornier HM-3 were compared: This fact may lead to believe that they are more efficient than the traditional spark gap systems.Īt the same time all electromagnetic systems have very thin focal areas, much smaller than the typical stone size, and therefore the available energy is not optimized for stone fragmentation, usually requiring much more shocks compared to a traditional Electrohydraulic lithotripter. Lately, new electromagnetic lithotripters were introduced, some with higher Focal Peak Pressure. The Peak Pressure at F2 and the Focal Area are the traditional parameters used to compare the performance and effectiveness of the Shock Wave produced by different lithotripters. EE.Direx Systems Corporation, Natick, MAįocal Cross-Section, the Truncated Focal Area and the Truncated Volume: Beth Israel-Deaconess Medical Center Harvard Medical School, Boston, MA. ![]()
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