EFFECT OF ULTRASOUND TRANSMIT POWER ON LIVER ENHANCEMENT WITH IMAGENT(R) US, A PFC-STABILIZED MICROBUBBLE CONTRAST AGENT

The pressure of the ultrasound wave may limit the longevity of microbu bble-based contrast agents. This study evaluated liver enhancement ove r time as a function of transmit power after the administration of AFO 145 (Imagent((R)) US; Alliance Pharmaceutical Corp., San Diego, CA). E ight rabbits with an avascular liver lesion created by percutaneous in jection of 1.0 mi of ethyl alcohol 7 days prior to scanning were image d with an Acuson 128XP/10 at 7 MHz before and after four separate intr avenous injections of 0.25 mi of AFO145 spaced at least 1 h apart. The avascular lesion served as an internal standard against which liver e nhancement could be compared. After contrast injection, scanning over the same plane was either continuous at (a) maximum or (b) minimum tra nsmit power (9 dB below maximum), or intermittent at (c) minimum power for 5 s every 15 s, or (d) for 5 s every 60 s. Each session was termi nated after 15 min or when contrast was no longer visible in the hepat ic parenchyma and blood vessels. Videodensitometry was used to assess liver-to-lesion intensity difference over time. Both the degree and du ration of liver enhancement were dependent on the transmit power. Live r enhancement with imaging at minimum power for 5 s/min was nearly two times greater and persisted nearly eight times longer (P < 0.01) than at maximum power and continuous insonation. Ultrasound transmit power affects both the peak and duration of liver enhancement. A lower powe r and shorter insonation time after AFO145 administration dramatically lengthens the imaging window for liver lesion detection. (C) 1997 Joh n Wiley & Sons, Inc.