POWER DOPPLER - AN ADVANCE OVER COLOR DOPPLER FOR TRANSCRANIAL IMAGING

The aim of this study is to compare the ability of mean frequency-base d colour Doppler (CD) and power Doppler (PD) to identify the basal cer ebral arteries in normal subjects. Fifty volunteers were recruited int o the study. The temporal acoustic window was used to image the basal cerebral arteries bilaterally. The number of positively identified ves sels was recorded, first using CD and then with PD. Our results show t hat both modalities were equally effective at demonstrating the anteri or cerebral artery (ACA), the middle cerebral artery mainstream (MCA M 1) and the precommunicating segment of the posterior cerebral artery ( PCA P1; ACA: 82% and 83%; MCA M1: 84% and 89%; PCA P1: 81% and 83%; CD and PD, respectively). However, the M2 portion of the MCA (CD: 25%, P D: 54%; difference 29% [95% CI 20-38%]), the P2 portion of the PCA (CD : 67%, PD: 75%; difference 8% [95% CI 3-13%]) and the posterior commun icating artery (CD: 15%, PD 32%; difference 17% [95% CI 10-24%]) were all identified in a significantly greater proportion of subjects using PD. Although its clinical value remains undetermined, PD offers signi ficant advantages over colour-coded sonography in imaging small-calibr e and low-flow arteries and those which run at unfavourable angles to the ultrasound beam.