PARALLEL AND SPIRAL FLOW PATTERNS OF VERTEBRAL ARTERY CONTRIBUTIONS TO THE BASILAR ARTERY

PURPOSE: To demonstrate that the in vivo flow from individual vertebra l arteries can be imaged and tracked in the basilar artery by use of s aturation planes with three-dimensional time-of-flight MR angiography. METHODS: Twenty volunteers were studied with intracranial three-dimen sional time of flight angiography MR. The MR angiography was repeated with saturation of the individual vertebral arteries, Flow voids and s ignal intensity within the basilar and posterior cerebral arteries wer e evaluated for flow patterns. RESULTS: Of 15 volunteers with a ''norm al'' vertebrobasilar anatomy, 80% demonstrated a pattern of flow withi n the basilar artery in which the contributing vertebral components re mained ipisilateral. This pattern was called ''parallel.'' A ''spiral' ' pattern of rotation of the contributing vertebral components was fou nd in 20% of studies. The inflow to the posterior cerebral arteries co uld be identified from specific vertebral contributions and was relate d to the size-dominance of the vertebral artery. CONCLUSION: There is nonadmixture of vertebral artery flows of variable duration within the basilar artery; at least two patterns of flow can be described within the basilar artery. The method presented is a simple technique for de termining vertebral artery flow components with routine software and w ithout secondary data manipulation.