Angiographic criteria for internal carotid near-occlusion

The figures illustrate the four criteria for internal carotid near-occlusion on conventional angiography. In all figures, the intravenous contrast (gray color) is shown emanating from a catheter positioned in the CCA. 

(A) Delayed filling
(B) Evidence of intracranial collaterals when the contralateral side is examined
(C) Ipsilateral distal ICA diameter less than the contralateral distal ICA diameter
(D) Ipsilateral distal ICA diameter equal to or less than the ipsilateral ECA diameter