Combined Assessment of Myocardial Perfusion and Regional Left Ventricular Function by Analysis of Contrast-Enhanced Power Modulation Images

Abstract

Background-Echocardiographic contrast media have been used to assess myocardial perfusion and to enhance endocardial definition for improved assessment of left ventricular (LV) function. These methodologies, however, have been qualitative or have required extensive offline image analysis. Power modulation is a recently developed imaging technique that provides selective enhancement of microbubble-generated reflections. Our goal was to test the feasibility of using power modulation for combined quantitative assessment of myocardial perfusion and regional LV function in an animal model of acute ischemia. Methods and Results-Coronary balloon occlusions were performed in 18 anesthetized pigs. Transthoracic power modulation images (Agilent 5500) were obtained during continuous intravenous infusion of the contrast agent Definity (DuPont) at baseline and during brief coronary occlusion and reperfusion and were analyzed with custom software. At each phase, myocardial perfusion was assessed by calculation, in 6 myocardial regions of interest, of mean pixel intensity and the rate of contrast replenishment after high-power ultrasound impulses. LV function was assessed by calculation of regional fractional area change from semiautomatically detected endocardial borders. All ischemic episodes caused detectable and reversible changes in perfusion and function. Perfusion defects, validated with fluorescent microspheres, were visualized in real time and confirmed by a significant decrease in pixel intensity in the left anterior descending coronary artery territory after balloon inflation and reduced rate of contrast replenishment. Fractional area change decreased significantly in ischemic segments and was restored with reperfusion. Conclusions-Power modulation allows simultaneous online assessment of myocardial perfusion and regional LV wall motion, which may improve the echocardiographic diagnosis of myocardial ischemia.

Simultaneous quantitative assessment of myocardial perfusion and function using analysis of color-encoded contrast-enhanced images

“…The notion of extracting information on myocardial perfusion from ultrasound images is highly attractive, and many times has been referred to as the "holy grail" of contrast echocardiography [8]. This goal stimulated multiple technological developments, including new imaging techniques targeted at increased sensitivity for the detection of intramyocardial contrast, such as pulse inversion [9] and power modulation [1].…”

“…Although it is agreed that information on myocardial perfusion would be an important adjunct to wall motion, quantification of perfusion with ultrasound contrast has not yet become a standard clinical technique. We have recently described semi-automated, off-line analysis of contrast-enhanced power modulation images for combined quantitative assessment of myocardial perfusion and regional LV function [1]. Regional LV function was evaluated from endocardial borders automatically detected frame-by-frame using depth-dependent thresholding.…”

“…Regional LV function was evaluated from endocardial borders automatically detected frame-by-frame using depth-dependent thresholding. Myocardial perfusion was assessed using high-energy ultrasound impulses and calculating indices of contrast replenishment in hand-drawn myocardial regions of interest (ROIs) with manual frame-by-frame realignment [1].…”

Clinical usefulness of SonoVue contrast echocardiography: the Thoraxcentre experience

“…6 Power modulation uses this assumption by transmitting repeated pulses of different intensities in the same direction (figure 2). Two consecutive pulses of identical shape but twofold difference in amplitude would result in identical reflections from the heart, other than the expected twofold difference in amplitude.…”

Ultrasound contrast agents : dynamics of coated bubbles

“…Moreover, unlike tissue, the contrast agents scatter at harmonic frequencies of the driving ultrasound frequency f , mainly at the second harmonic frequency 2 f , which opens up improved imaging modalities in ultrasound, termed harmonic imaging [61]. Power modulation imaging [62] and pulse inversion imaging [5], including many of its derivatives are now standard pulse-echo techniques found on ultrasound scanner equipment. These imaging modalities all exploit the nonlinear behavior of the ultrasound contrast agents.…”