Prolongation of TCD-enhanced Doppler signal by continuous infusion of levovist

This study evaluated the effects of two different rates of infusion of echo-contrast agents (ECA) on signal enhancement. A total of 15 patients with insufficient Doppler signal due to inadequate transtemporal acoustic bone window were examined. Signal from the middle cerebral artery was recorded during the IV infusion of Levovist (300 mg/mL). Increment of signal enhancement in dB, time to signal enhancement appearance, time to clinically useful signal enhancement appearance, and duration of clinically useful signal enhancement were assessed during two infusions at the rate of 1 and 0.66 mL/min, respectively. Increment of signal enhancement was similar at the rate of 1 and 0.66 mL/min (p = 0.4). Mean time to signal enhancement appearance and mean time to clinically useful signal enhancement appearance were not significantly different with the two rates of infusion (p = 0.9 and p = 0.3, respectively). Mean duration of clinically useful signal enhancement was significantly higher with the infusion rate of 0.66 mL/min as compared to 1 mL/min (p < 0.0001). Levovist injected at the infusion rate of 0.66 mL/min prolonged the mean duration of signal enhancement, maintaining its effectiveness.