Clinical experience with echo-enhanced transcranial Doppler and duplex imaging.

Transcranial Doppler (TCD) and transcranial color-coded duplex sonography (TCCD) are ultrasound neuroimaging modalities that can provide useful diagnostic information on the intracranial vasculature with a high degree of safety. However, the skull can serve as an effective bone barrier, reducing reflected ultrasound signal by up to 100% in some patients and thereby challenging both technical quality and clinical interpretation of TCD and TCCD. Levovist is an IV ultrasound echo-enhancement agent that withstands passage through the heart and lung, increasing signal throughout the entire vascular pool. As part of European phase II and III clinical trials, this agent has been studied for utility of enhancement for TCD and TCCD studies in patients with signs and symptoms of cerebrovascular disease. All patients had either highly insufficient or nonexistent native signal on baseline transcranial ultrasound studies before administration of Levovist. The agent was administered at concentrations of 200, 300, or 400 mg/ml, and studies were repeated. In all studies, 300 to 400 mg/ml was sufficient for enhancement, although in several phase II studies 300 mg/ml Levovist was the preferred dosage in terms of superior imaging with a low level of side effects. In a phase III study, Levovist improved diagnostic utility of TCD and TCCD without compromising safety. Reviews of clinical phase II and III studies show that echo enhancement with Levovist facilitates routine clinical investigation of intracranial vascular anatomy in patients with signs and symptoms of intracranial vascular disease. In patients with no native signal, Levovist-enhanced imaging permits visualization of small peripheral vessels, venous circulation, tissue characteristics, and perfusion data, with no significant loss of safety.