Color flow Doppler versus power Doppler imaging in the examination of vertebral arteries

Abstract

Objective: Power Doppler imaging (PDI) is a newly introduced ultrasound method which visualizes the integrated power of the Doppler signal instead of its frequency shift. We compared this technique with the conventional color flow Doppler (CFD) in the examination of extracranial vertebral arteries. Methods: In the present study, 195 patients with normal findings of the vertebral arteries and 35 with vertebral hypoplasia, stenosis or occlusion, who were referred because of suspected disorders of cerebral circulation, were examined. Using an electronic 7.5 MHz linear probe, the vertebral arteries were examined with conventional CFD and PDI at the V 2-segment and at the origin from the subclavian artery (V 0-segment). Results: In 286 vertebral arteries of 195 normal persons, the visualized diameter of the blood-flow signal was 3.32 ± 0.54 mm (mean ± S.D.) using CFD vs. 3.63 ± 0.55 mm using PDI (correlation 0.78; P < 0.001) on the left side and 3.23 ± 0.56 mm using CFD vs. 3.51 ± 0.64 mm using PDI (correlation 0.78; P < 0.001) on the right side. PDI revealed 9.5% larger diameter on both sides when compared to conventional CFD. In distally stenosed or occluded vertebral arteries where a signal could be obtained using both methods, the difference between diameters was similar to that of normal vertebral arteries, with 2.40 ± 0.52 mm (CFD) vs. 2.63 ± 0.71 mm (PDI; correlation 0.81; P < 0.01). In vertebral hypoplasia, CFD revealed a signal of 1.50 ± 0.52 mm vs. 1.73 ± 0.71 mm with PDI; (correlation 0.79, P < 0.01). In the proximally stenosed vessels, PDI visualized morphological details more clearly by overcoming artifacts such as aliasing and echoshadowing. In one case of distal occlusion, CFD failed to show a blood flow signal, whereas PDI demonstrated continuous perfusion. Conclusions: PDI is a useful additional color-coding technique in duplex sonographic examination, particularly of hypoplastic and stenosed vertebral arteries.