The effects of a soft tissue mimicking medium and increased power settings on the location and magnitude of lithotripter peak positive pressure.
In vitro experiments showed that a tissue mimicking medium alters the peak positive pressure (p+), focal zone properties and frequency content of shockwaves compared with their behavior in water. The reduction in (p+) ranged from 5% at 10 kV. to 19% at 18.1 kV., when measured at the geometric focus with the tissue mimicking medium present. As power settings were increased, the relative gain in pressure was damped by attenuation. A 2 mm. shift in the acoustic focus was seen both axially and laterally with the tissue mimicking medium. While the former is probably not significant, the latter may be clinically significant given the narrow lateral beam width at the acoustic focus. These attenuation experiments suggest that clinical targeting through tissue may not be as precise or result in as high peak pressures as the clinician expects. Especially at high power settings, the depth of tissue traversed should be minimized to limit attenuation effects.
Davros
W J
WJ
Department of Radiology, Georgetown University Medical Center, Washington, DC 20007.
Garra
B S
BS
Pahira
J J
JJ
Zeman
R K
RK
D055592:Biophysical Phenomena; D001703:Biophysics; D008096:Lithotripsy; D008954:Models, Biological; D011312:Pressure