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Analysis of regional cerebral blood flow in dogs, with an experimental microbubble-based US contrast agent
R S Greenberg1, G A Taylor, J C Stapleton
1Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Md, USA.
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-pixelintensity 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.