Destruction of contrast microbubbles during ultrasound imaging at conventional power output

Inhomogeneous opacification of cardiac chambers has been frequently observed after intravenous administration of long-persisting echocardiographic contrast agents. We observed this phenomenon to be most pronounced at high acoustic powers with incomplete opacification of the left ventricular apex and left ventricular outflow tract. Reducing the acoustic energy to which the contrast was exposed by decreasing transmit power or intermittently suspending insonification resulted in homogenous opacification of the entire left ventricular cavity. We systematically examined the effect of varying insonification power on the persistence of three investigational ultrasound contrast agents in both in vitro and in vivo models. We found an inverse relationship between the insonifying power and the persistence of the contrast agents. Contrast intensity decay could be reduced either by decreasing exposure to ultrasound by minimizing the transmit power of the system or by intermittently suspending ultrasound generation (triggering). Minimization of ultrasound contrast exposure to ultrasound energy thus improves echocardiographic contrast duration and homogeneity.