Abstract
Non-invasive measurements of intracranial blood flow velocities can be made through the fontanel by the Doppler technique. A range gated 2 and 5 MHz instrument with a 2-4 mm long sampling volume was used in an in vitro model, simulating intracranial blood flow in newborns. The Doppler instrument measured the maximum and the cross-sectional mean frequency Doppler shifts. Calibration signals were used to transform the frequency shift to velocity. The computed time average of the mean frequency Doppler signal was the best measure of absolute flow (r=0.985, p < 0.001) in artificial blood vessels with 1.0-2.8 mm diameters, over a wide range of flows, 4-94 ml/minute. A fontanel was created surgically in newborn lambs and the blood flow velocities in the basal intracranial arteries were measured with the Doppler instrument. Simultaneous recordings of the carotid blood flow were made by electromagnetic flow cuffs. Occlusions of one or both carotid arteries induced changes in intracranial blood flow velocities, closely correlated to the carotid blood flow on the same side (r=0.89, p<0.01). The pulsatility index was not a useful indicator of changes in blood flow. The range gated Doppler instrument can measure blood flow velocities in very small arteries, at a defined depth under the fontanel. The time average of the mean frequency Doppler signal is the closest estimate of absolute blood flow, when the diameter of the blood vessel under study cannot be measured.
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Lundell, B., Lindstrom, D., Arnold, T. et al. VALIDATION OF THE PULSED DOPPLER TECHNIQUE FOR ASSESSMENT OF CEREBRAL BLOOD FLOW VELOCITY. Pediatr Res 18 (Suppl 4), 379 (1984). https://doi.org/10.1203/00006450-198404001-01717
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DOI: https://doi.org/10.1203/00006450-198404001-01717