Regional cerebral blood flow estimates in newborn lamb using amplitude-mode color Doppler ultrasound

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Abstract
Purpose. To establish the feasibility of determining changes in regional cerebral blood flow using amplitude-mode color Doppler ultrasound in the newborn lamb.Methods. Regional cerebral blood flow was modified by intrastriatal injection ofN-methyl-D-aspartic acid (NMDA) in two newborn lambs and compared with that in a control animal receiving only intrastriatal saline. Serial color Doppler ultrasound energy images were obtained in coronal projection at the level of the foramen of Monro, before and at 20, 40, and 60 min after NMDA or saline injection using a 7.0-MHz linear transducer. Real-time images were obtained and transferred onto a computer workstation. Regions of interest were drawn over each striatum and cerebral hemisphere and were analyzed for mean pixel intensity (MPI) at each interval. Paired regional cerebral blood flow (r-CBF) determinations (radiolabeled microsphere technique) were also obtained in every animal. MPI and r-CBF for each anatomic region were compared using linear regression.Results. Mean color pixel intensities increased significantly in the ipsilateral basal ganglia and cerebral hemisphere (p < 0.0001) in both animals injected with NMDA, but not in the animal injected with normal saline (p < 0.63). A strong and significant linear correlation was found between MPI and r-CBF for striatum (r = 0.89,p < 0.0001) and cerebral hemisphere (r = 0.85,p < 0.0001).Conclusions. Amplitude-mode color Doppler ultrasound shows potential for technically simple determination of serial changes in regional cerebral blood flow in infants.