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FIG 2. 37-year-old man with progressive bitemporal visual field defect.
A, CT scan of the midcranial skull base in the axial plane shows a transsphenoidal encephalocele (white arrows) and a narrow right carotid canal (black arrow).
B and C, MR angiograms obtained using the 3-D time-of-flight technique with 40/7/1, flip angle of 15°, 64 sections, and 1.2-mm section thickness.
B, Axial source image shows the narrow diameter of the right ICA within the carotid canal (arrow).
C, Maximum-intensity projection reconstruction in the anteroposterior view shows signal loss of the right distal ICA (curved arrow). The large left ICA (straight solid arrow) and anterior cerebral artery (open arrow) caused by the collateral blood supply to the right middle cerebral artery and to the right anterior cerebral artery provided by the left carotid system via the anterior communicating artery can be seen.
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