A trans pulmonary contrast medium enhances the transcranial doppler signal in humans

Abstract

Background and Purpose: Transtemporal insonation in transcranial Doppler sonography is often impaired by an insufficient signal-to-noise ratio, especially in elderly patients. A transpulmonary stable air microbubble suspension was injected intravenously in humans as an intracranial ultrasonic contrast agent Methods: In a clinical phase II study, 20 patients (15 women, 5 men; mean age, 65.5 ±11.5 years) presenting with clinical indications for transcranial Doppler investigation were examined. A total of 97 intravenous injections with different concentrations (200, 300, and 400 mg/mL of suspension) of air microbubbles bound to galactose microparticles as a carrier were performed. The signal enhancement of color-coded pulse curves of basal cerebral arteries was evaluated off-line in comparison to an integrated color-coded decibel scale, considering quality, quantity, and time course of enhancement requiring a 3-dB level above the native signal. The overall diagnostic information was assessed according to a reliability score. Results: The first acoustic signal increase was registered after an average of 21 seconds. Time intervals for a dose-dependent peak intensity and maximal duration were 41.3±17.1 seconds and 118.0±69.8 seconds (200 mg/mL); 55.5±27.7 seconds and 237.0± 112.3 seconds (300 mg/mL); and 66.1 ±31.8 seconds and 293.0±122.0 seconds (400 mg/mL), respectively. Duration of signal enhancement increased significantly (P