Journal of Ultrasound in Medicine, Vol 20, Issue 12 1329-1339, Copyright © 2001 by American Institute of Ultrasound in Medicine
Pattern of Doppler flow indices at the carotid bifurcation: evaluation by hemodynamic color Doppler imaging
G. S. Lin and V. S. Naval
Advanced Imaging Associates, Fremont, CA 94555-2016, USA.
OBJECTIVE: To visualize the spatial variation of Doppler indices,
principally the pulsatility index, taken proximal to the carotid
bifurcation and to evaluate their relationship to the geometry of the
carotid bulb. METHODS: The pattern of ultrasonographic Doppler indices was
studied in healthy volunteers by using hemodynamic color Doppler imaging,
which computes and displays a Doppler index at each color pixel from a
sequence of color Doppler image frames taken over several cardiac cycles.
RESULTS: In carotid bulbs with laminar flow (n = 5), the spatial
partitioning between low-resistance internal carotid artery and
high-resistance external carotid artery flows could be followed over 5 cm
upstream in the common carotid artery. However, normal reverse or vortex
flows at the carotid bulb (n = 15) obliterated upstream flow partitioning
within 2 cm of the flow divider The pulsatility index was neither laterally
nor axially uniform in the common carotid artery. CONCLUSIONS: Localization
of "core flow" where meaningful Doppler indices may be measured is
determined by the expansion geometry of the carotid bulb and usually
requires positioning of a small sample volume in the center of the lumen at
least 3 cm upstream from the flow divider However, in the absence of
reverse or vortex flows, placement of a spectral Doppler sample volume is
best guided by hemodynamic color Doppler imaging.
