Imaging of myocardial perfusion with SonoVue(TM) in patients with a prior myocardial infarction

Myocardial contrast echocardiography (MCE) is an evolving noninvasive imaging technique that can be used to assess regional myocardial perfusion. MCE relies upon the detection of nonlinear ultrasound signal from gas-filled microbubbles during their microvascular transit, resulting in tissue opacification. Provided that the relation between myocardial microbubble concentration and video intensity (VI) is within the linear range, VI measured from any myocardial region reflects the relative tissue concentration of microbubbles, which is influenced by three factors: (1) microbubble concentration in blood; (2) the myocardial blood volume fraction; and (3) microbubble destruction that occurs within the ultrasound beam. In this article, we discuss how these three factors may influence myocardial perfusion information provided by MCE and highlight the importance of image processing. In order to illustrate these concepts, we examine data obtained during perfusion imaging in patients with prior myocardial infarction using intermittent harmonic imaging at various ultrasound pulsing intervals (PIs) during bolus and continuous venous infusions of a second-generation microbubble agent (SonoVue(TM)). Our results suggest that evaluation of resting perfusion is most accurate when both myocardial blood volume and blood velocity are assessed. This information is provided only with continuous infusions of microbubbles during imaging protocols that vary the ultrasound PI.