Usefulness of acceleration time for assessment of stenosis in the extracranial internal carotid artery

The aim of this study was to investigate the usefulness of acceleration time (AcT) determined by sonography for evaluation of severe stenosis in the internal carotid artery (iCA). We evaluated 127 ICAs and common carotid arteries (CCAs). Linear- and convex-array probes were used for sonographic assessment, and the peak systolic flow velocity (PSV) at the carotid bulb was evaluated by the pulsed Doppler method. The linear-array probe was set in the CCA 2cm above the carotid sinus, and the convex-array probe was set in the ICA 3cm above its origin to measure the Doppler waveform. The Act ratio was calculated as ICA/AcT of the ipsilateral CCA and correlated with the PSV. Simple regression analysis and the receiver operating characteristic curve were used to examine the relationship between the AcT ratio and PSV. There was a significant relationship between the PSV and AcT ratio. Based on the receiver operating characteristic curve, the sensitivity and specificity of the AcT ratio using a cutoff level of 2.0 were 90.0% and 96.6%, respectively, for diagnosis of a PSV exceeding 200cm/s. These results suggest that an AcT ratio of 2.0 reflects a degree of stenosis exceeding 70%.