Effects of pulsed ultrasound on the frog heart: II. An investigation of heating as a potential mechanism.
This study investigated heating as the possible mechanism for the reduction in aortic pressure observed as a result of exposure of frog hearts in vivo to a single, high intensity pulse of ultrasound. The threshold for producing reduced aortic pressure with 5 ms pulses of ultrasound was found to be approximately 5-10 MPa peak positive pressure (ISPPA approximately 350-1000 W/cm2) at both 1.2 MHz and 3.7 MHz. Theoretical estimates and experimental measurements of heating, though, indicate that heating rates at threshold exposures for these two frequencies differ by as much as a factor of 10. As a result, heat alone does not appear to be the primary mechanism responsible for the observed effects on the heart.
Dalecki
D
D
Department of Electrical Engineering, University of Rochester, NY 14627.
Raeman
C H
CH
Carstensen
E L
EL
D000818:Animals; D001011:Aorta / Q000502:physiology*; D004452:Echocardiography; D006321:Heart / Q000502:physiology*; D006361:Heating; D011894:Rana pipiens