Assessment of Intracranial Collateral Flow by Using Dynamic Arterial Spin Labeling MRA and Transcranial Color-Coded Duplex Ultrasound

Background and Purpose—To evaluate the potential of a new dynamic MRA sequence (DynAngio) based on arterial spin labeling for the assessment of intracranial collateral flow. Methods—Twelve patients with unilateral internal carotid artery obstruction were investigated. Different patterns of collateral flow were compared between DynAngio, transcranial color-coded duplex ultrasound, and time-of-flight MRA. Results—There was a good agreement between the methods, with sensitivities between 80 % and 90%. Small collateral vessels were detected more frequently with DynAngio compared to time-of-flight MRA. Conclusion—DynAngio provides anatomic and similar to transcranial color-coded duplex ultrasound functional informa-tion on collateral flow for the assessment of intracranial hemodynamics. (Stroke. 2008;39:000-000.) Key Words: carotid stenosis collateral circulation diagnostic imaging magnetic resonance angiography transcranial ultrasound The first pathoanatomical description of the intracranialarterial circle by Fallopius and Johann Jakob Wepfer1 dates back to 1561 and 1658, whereas its anastomotical function was discovered by Sir Thomas Willis2 in 1664. To date, it is still of high relevance to study collateral function of the circle of Willis, because this may allow the estimation o