DESTRUCTION OF CONTRAST MICROBUBBLES DURING ULTRASOUND IMAGING AT CONVENTIONAL POWER OUTPUT

Inhomogeneous opacification of cardiac chambers has been frequently ob served after intravenous administration of long-persisting echocardiog raphic contrast agents. We observed this phenomenon to be most pronoun ced at high acoustic powers with incomplete opacification of the left ventricular apex and left ventricular outflow tract. Reducing the acou stic energy to which the contrast was exposed by decreasing transmit p ower or intermittently suspending insonification resulted in homogenou s opacification of the entire left ventricular cavity. We systematical ly examined the effect of varying insonification power on the persiste nce of three investigational ultrasound contrast agents in both in vit ro and in vivo models. We found an inverse relationship between the in sonifying power and the persistence of the contrast agents. Contrast i ntensity decay could be reduced either by decreasing exposure to ultra sound by minimizing the transmit power of the system or by intermitten tly suspending ultrasound generation (triggering). Minimization of ult rasound contrast exposure to ultrasound energy thus improves echocardi ographic contrast duration and homogeneity.