ENHANCEMENT OF THE ECHOGENICITY OF FLOWING BLOOD BY THE CONTRAST AGENT PERFLUBRON

RATIONALE AND OBJECTIVES. Perflubron, or perfluorooctylbromide, is an effective ultrasound and computed tomography contrast agent in a lecit hin emulsion form. The authors studied acoustical properties of perflu bron emulsion in static human and flowing porcine blood for concentrat ions from 0% to 30% weight per volume. METHODS. Propagation velocity ( c), the intensity attenuation coefficient (mu), density (rho), and par ticle size were measured directly. Because the backscatter of flowing blood is dependent on shear rate, relative echogenicity was measured a s a function of perflubron concentration in whole porcine blood, in a laminar flow system, at shear rates of 16.0 to 68.5 sec-1 for real-tim e sector scanner images obtained at 7.5 MHz. RESULTS. Neat perflubron is a colorless liquid with density of 1.93 g . mL-1 and velocity of 63 0 m . sec-1. The following values were obtained at 4.7 MHz in static h uman blood (hematocrit 44%) at expected human in vivo blood concentrat ions of 3.1% perflubron versus pure human blood: rho = 1.11 versus 1.0 5 g . mL-1, c = 1,480 versus 1,576 m . sec-1, mu = 1.00 versus 0.36 dB . cm-1. The mean echogenicity of whole porcine blood increased substa ntially with perflubron concentration and was inversely proportional t o blood shear rate. CONCLUSION. Adding 3.1% concentration of perflubro n increased image echogenicity at all shear rates studied, ranging fro m 70% at 68.5 sec-1 (16.3 cm . sec-1) up to 180% at 16.0 sec-1 (3.8 cm . sec-1). Perflubron enhancement of blood is marked and demonstrates shear rate dependence like that of whole blood.