Transcranial Color-Coded Duplex Sonography in Arterial Cerebrovascular Disease

Transcranial color-coded duplex sonography (TCCD) is a new ultrasound technique that adds color-coding of the frequency- or power-based Doppler signal and B-mode imaging to conventional transcranial Doppler sonography (TCD). As conventional TCD this technique identifies stenoses, occlusions and vasospasm of the major basal cerebral arteries. The additions visualize the anatomy and flow direction of the basal cerebral arteries, the ventricular system, parenchymal and bony structures. Thus potentially hazardous compression tests to identify cerebral arteries are rarely necessary, and ultrasonic assessment of cross-flow through the circle of Willis becomes more reliable. Moreover, estimates of insonation angles and measurements of angle-corrected flow velocities become feasible. TCCD may visualize larger (>1 x 1 cm) supratentorial hematomas with subcortical location, and provide incidental diagnosis of cerebral arteriovenous malformations, aneurysms, and hydrocephalus, but is inferior to neuroradiological techniques. The main limitation of TCCD is the acoustic window that may prevent transtemporal insonation in up to 30% of cases. Transpulmonary contrast agents may permit the examination of such patients. Power-based TCCD, used alone or in combination with echo contrast agents or three-dimensional ultrasound imaging, represent important future developments of TCCD.