Transcranial Doppler imaging: state of the art

Initially introduced in the early 1980's, transcranial Doppler followed by transcranial Doppler sonography were used in neurosurgical units for manage ment and follow-up of intracranial vasospasm in patients with subarachnoid hemorrhage. This imaging technique, more sensitive and less invasive than c atheter angiography, also proved to be of value for diagnosis of intracrani al atherosclerosis, management of patients with head trauma, and evaluation of collateral flow through the circle of Willis. Doppler US would also all ow prediction of the risk of symptomatic embolic events through monitoring of HITS. Evaluation of the middle cerebral arteries during carotid occlusio n testing is useful for evaluating the need for particular revascularizatio n techniques. Finally, Doppler imaging is useful to assess patients with po ssible brain death. A recent advance in Doppler imaging is the ability to p rovide a three-dimensional projection (3D Doppler) of the intracranial arte ries enabling improved detection and evaluation of stenoses involving the c ircle of Willis and improved characterization of intracranial aneurysms. Th ese new applications benefit from the use of US contrast agents and harmoni c US imaging.