Assessment of the Collateral Function of the Circle of Willis
Three-Dimensional Time-of-Flight MR Angiography Compared with Transcranial Color-Coded Duplex Sonography
Arjan W.J. Hoksbergena,
Charles B.L. Majoieb,
Frans-Jan H. Hulsmansb and
Dink A. Legematea
a Department of Surgery, Academic Medical Center, Amsterdam, the Netherlands
b Department of Radiology, Academic Medical Center, Amsterdam, the Netherlands
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FIG 1. Examples and prevalence of circle of Willis anomalies that hamper collateral function. Prevalence is derived from studies by using an external diameter of 1 mm as a threshold for hypoplasia of collateral arteries. A1 indicates the precommunicating part of the anterior cerebral artery; M1, main trunk of the middle cerebral artery; P1, precommunicating part of the posterior cerebral artery; BA, basilar artery; and VA, vertebral artery.
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FIG 2. TCCD sonogram of the circle of Willis in the left temporal window and axial scanning plane at the level of the mesencephalon. The ipsilateral (left) M1, P1 (red), and A1 (blue) are shown. The contralateral (right) M1 and P1 (blue) and A1 (red) are also shown.
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FIG 3. Doppler spectra.
A, Spectrum shows blood flow reversal in the A1 during ipsilateral carotid compression indicating functional patency of the AcoA.
B, Spectrum shows blood flow velocity increase of more than 20% in the P1 during ipsilateral carotid compression indicating functional patency of the PcoA.
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FIG 4. 3D TOF MR angiograms.
A, Angiogram of the circle of Willis with the complete anterior configuration shows the AcoA (arrow).
B, Angiogram of the circle of Willis with the complete posterior configuration shows the right and left PcoAs (arrows)
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