[Focal size and shock wave pressure: a comparison of three different physical shock wave generators].
Shock-wave delivery and focal size of three different generators-electrohydraulic, electromagnetic and piezoelectric--were compared. Pressure measurements were uniformly made by needle hydrophone (piezoelectric transducer). The smallest focus, 17 x 3 x 3 mm, was achieved with the piezoelectric system (50% isobars), while the focus with the electromagnetic generator was much larger (50 x 7 x 4 mm). With the electrohydraulic generator the focal size of the 60% isobars was 20 mm in the longitudinal axis. The highest pressure, 1512 bar, was achieved with the piezoelectric lithotriptor (mean shock-wave pressure in focus: electrohydraulic 1000 + 100, electromagnetic 1000 + 25, piezoelectric 1400 + 27 bar). The rapid positive pressure rise was followed by a slower pressure fall and a small negative wave. In the focal region the negative pressure wave was between 112 and 200 bar with the electrohydraulic system, 100-146 bar with the electromagnetic one, and 134 bar with the piezoelectric one. The significance of the negative wave is not clear; perhaps it contributes to the development of the cavitation effect and facilitates stone fragmentation.
Janowitz
P
P
Abteilung Innere Medizin II, Universität Ulm.
Stuber
M
M
Meier
T
T
Steiner
R
R
Schneider
H T
HT
Ell
C
C
Neuhaus
H
H
Ott
R
R
Swobodnik
W
W
Kratzer
W
W
D055590:Electromagnetic Phenomena; D006801:Humans; D008096:Lithotripsy / Q000379:methods*; D011312:Pressure; D014159:Transducers
Fokusgrösse und Stosswellendrücke: Vergleich von drei verschiedenen physikalischen Stosswellengeneratoren.