Analysis of regional cerebral blood flow in dogs, with an experimental microbubble-based US contrast agent

PURPOSE: To evaluate a perfluorochemical stabilized microbubble-based ultrasound (US) contrast agent (Imagent US, formulation AF0145) create regional cerebral blood flow (CBF) maps. MATERIALS AND METHODS: Intravenous injections of the contrast agent (0.16-0.20 mL/kg) were performed in four anesthetized dogs (9-14 kg). Serial coronal color-Doppler-amplitude and gray- scale US scans were obtained through a cranial window during injection of contrast material. Mean pixel intensity was analyzed on digitized images. Regional CBF was varied by modifying arterial partial pressure of carbon dioxide (PaCO₂). Color-Doppler-amplitude and gray-scale mean pixel intensity and percentage change in mean pixel intensity after injection of contrast material were analyzed, by means of a bolus injection curve that plotted color mean pixel intensity per unit area versus time. RESULTS: Contrast material injection resulted in a statistically significant difference in color-Doppler-amplitude and gray-scale enhancement of brain. Color mean pixel intensity increased from 1.4 units ± 1 (standard error) to 122 units ± 6 in thalamus and from 9.7 units ± 4.0 to 107 units ± 9 in cortex (P < .0001). Gray-scale mean pixel intensity increased from 0.55 units ± 0.20 to 33 units ± 11 in thalamus and from 0.42 units ± .06 to 10.5 units ± 2.0 in cortex (P < .005). Correlation between the area under the color-Doppler-amplitude mean-pixel-intensity curve and regional CBF in thalamus and cortex was significant (r = .815, P < .0001). CONCLUSION: Color-Doppler-amplitude US can be used to create regional CBF maps and shows potential for noninvasive evaluation of CBF in the critically ill newborn.