Evaluation and application of transcranial colour-coded sonography.

Since 1982, transcranial Doppler sonography (TCD) has been used for the measurement of blood flow velocities in the basal cerebral arteries. Transcranial colour-coded sonography (TCCS) is a recent development which overcomes certain limitations of conventional TCD. Using TCCS, the brain parenchyma can be imaged with B-mode ultrasound, the basal cerebral arteries can be imaged using colour-coded Doppler ultrasound, and simultaneous haemodynamic interrogation of the imaged vessel segments can be performed. The present study was undertaken in order to define its value in cerebrovascular disorders. The "Spectra" system (Diasonics Inc.) with a dedicated 2.25 MHz transcranial transducer was used to gather reference data from normal subjects (n=115), to determine intraobserver (n=16) and interobserver reproducibility (n=16), and to compare haemodynamic parameters with those gathered using a conventional TCD device (n=20). Patients with acute stroke (n=68), extracranial carotid artery disease (n=76), arteriovenous malformations (n=14) and intracranial aneurysms (n=5) were also studied. In normal subjects, blood flow velocities showed a significant decline with age, and females showed significantly greater velocities than males below the age of 60 years. Intraobserver reproducibility was better than interobserver reproducibility although both appeared reasonable for clinical purposes. TCCS provided systematically and significantly greater blood flow velocities than TCD (due to correction for the angle of insonation with the former technique). Stroke patients with major vessel occlusion and evidence of multiple intracranial branch occlusion could be identified using TCCS and extracranial carotid ultrasound. TCCS enabled the detection of middle cerebral artery stenosis (n=6) prior to carotid endarterectomy, and identified Willisian collateral pathways (n=29) in patients with occlusive carotid artery disease. Twelve intracranial arteriovenous malformations could be imaged and principal feeder arteries were identified in 13 cases. TCCS was unable to image small (<5 mm diameter) intracranial aneurysms. TCCS allows rapid, noninvasive haemodynamic assessment of the basal cerebral arteries in normal subjects and patients with cerebrovascular disorders. The imaging facility aids vessel identification and blood flow velocity data should be closer to the "true" values than those determined using conventional TCD.