Objectives: Circle of Willis, the main collateral pathway for cerebral circulation, is complete in only a portion of the population. There are many variations in the Circle of Willis. Fetal posterior cerebral artery, which is defined as posterior cerebral artery arising from internal carotid artery, is a common variant of the Circle of Willis. Though association between the fetal posterior cere...

The circle of Willis was originally described in 1664 [1]. The circle of Willis is a structure receiving arterial blood supply from the internal carotid and basilar arteries. The circle allows for the equalization of blood flow between cerebral hemispheres allowing for anastomotic circulation [2, 3]. The circle of Willis then divides into 3 paired vascular divisions: anterior, middle and poster...

BACKGROUND AND PURPOSE Identification of the intracranial collaterals assists in identifying patients with severe occlusive disease of the internal carotid arteries who are at lower risk of transient ischemic attacks (TIAs) and stroke. We investigated the usefulness of MR angiography in identifying functional collaterals of the circle of Willis. METHODS MR angiography of the circle of Willis ...

PURPOSE To determine the direction of blood flow in the circle of Willis using a 3-D phase contrast MR angiographic (MRA) technique with high spatial resolution. SUBJECTS Fifty healthy subjects and 15 patients with occlusive disease were studied using 3-D phase contrast MRA. RESULTS In the 50 normal subjects, 39 (78%) had detectable flow in one or both posterior communicating arteries. In 2...

Background and Purpose—Wall shear stress (WSS) and pressure are important factors in the development of cerebral aneurysms. We aimed to develop a computational fluid dynamics simulator for flow in the complete circle of Willis to study the impact of variations in vessel radii and bifurcation angles on WSS and pressure on vessel walls. Methods—Blood flow was modeled with Navier-Stokes equations ...

Objective. Circulus arteriosus/circle of Willis (CW) is a polygonal anastomotic channel at the base of the brain which unites the internal carotid and vertebrobasilar system. It maintains the steady and constant supply to the brain. The variations of CW are seen often. The Aim of the present work is to find out the percentage of normal pattern of CW, and the frequency of variations of the CW an...

Background A promising technique to measure blood flow is timeresolved three-dimensional phase contrast MRI (PCMRI). In small structures as the Circle of Willis (CoW), the resolution of the measurement needs to be high (< 1 mm). Image quality may be compromised when SNR decreases with increasing resolution which leads to blood flow direction uncertainty and flow quantification inaccuracies. To ...

UNLABELLED Current assessment of visual neglect involves paper-and-pencil tests or computer-based tasks. Both have been criticised because of their lack of ecological validity as target stimuli can only be presented in a restricted visual range. This study examined the user-friendliness and diagnostic strength of a new "Circle-Monitor" (CM), which enlarges the range of the peripersonal space, i...