ULTRASONIC CHARACTERIZATION OF ALBUNEX, A NEW CONTRAST AGENT

A new, promising ultrasound contrast agent, Albunex® (Molecular Biosystems, Inc., San Diego, California), is increasingly being used in experimental myocardial contrast echocardiography. Albunex® is a suspension of stable microencapsulated air bubbles prepared from 5% albumin. Contrast agents like Albunex® have been used to estimate regional myocardial perfusion. Current methods that use contrast media to assess myocardial perfusion in vivo from ultrasonic images are neither reliable nor absolute. The primary reason is that the fundamental relationship between ultrasonic properties and physical properties of the contrast media is unknown. Ultrasonic backscatter, acoustic velocity, and attenuation of Albunex® as a function of its concentration, size, and temperature at 7.5 and 5 MHz were measured. The backscatter coefficient, which is an absolute measure of ultrasonic backscatter, was found to be approximately linearly proportional to the number of microspheres in Albunex® (r = 0.86) at low concentrations. The attenuation coefficient was found to be linearly proportional to the number of microspheres (r = 0.96). An understanding of the relationship between the physical and ultrasonic properties of Albunex® is essential if it is to be used to quantify myocardial perfusion. © 1990, Acoustical Society of America. All rights reserved.