CHARACTERISTICS OF TRANSCRANIAL DOPPLER SIGNAL ENHANCEMENT USING A PHOSPHOLIPID-CONTAINING ECHOCONTRAST AGENT

Background and Purpose Ultrasound attenuation caused by the skull is a major limitation of transcranial Doppler. Echocontrast agents (EAs) m ay solve this problem. The aim of the present study was to investigate the characteristics of a new echocontrast agent (BY963) containing ai r bubbles stabilized by phospholipids. Methods Nine healthy volunteers received three different doses (2.5, 5.0, and 10 mt) of BY963 at an i njection rate of 0.25 mL/s. The Doppler signal amplitude obtained from the middle cerebral artery was recorded with a 2-MHz pulsed-wave Dopp ler system. After complete decay of the signal enhancement, upward str oking of the veins of the upper arm was performed to evaluate the stab ility of the EA in the venous system. Results A dose-dependent increas e of at least 30 dB in the Doppler signal amplitude lasted 19 to 47, 3 5 to 64, and 48 to 126 heart cycles (68% range) after 2.5, 5.0, and 10 mt EA, respectively. In 6 cases, there was a biphasic increase in EA enhancement. Upward strolling of the forearm, in general 12 to 18 minu tes after administration, caused a Doppler signal enhancement of at le ast 30 dB in 6 cases. Conclusions Each injection of BY963 caused a dia gnostically relevant Doppler signal enhancement. A considerable amount of EA remained stable in the venous system for at least 12 minutes. T he biphasic dose-response fits to models of dilution-indicator theory and indicates free recirculation, as well as a nonlinear washout curve .