Abstract:

Transient response imaging (TRI) is the increase in apparent myocardial contrast with reduced image frame rate (PRF) when perfluorocarbon-filled echo-contrast agents are infused. TRI allows improved estimation of myocardial perfusion, but its mechanism is not known. Recent work suggests that contrast microbubbles are destroyed by imaging at conventional frame rates (30--40 Hz), while less destruction occurs at cardiac-synchronized frame rates. Using a 20-MHz passive cavitation detector, acoustic emissions were recorded from within the myocardium of two anesthetized dogs in vivo during ultrasonic imaging with a clinical scanner. Strong correlations among root-mean-square detector output, videodensity, and PRF point to bubble emissions themselves as possibly responsible for the improved contrast. [Work supported by Nebraska AHA.]