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. 2009 Nov;5(4):279–288. doi: 10.2174/157340309789317887

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© 2009 Bentham Science Publishers Ltd.

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.5/), which permits unrestrictive use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Fig. (4). Transcranial Doppler Ultrasound demonstrating patterns of collateral circulation. — Panel A. Normal flow velocities and direction of flow in the internal (ICA), middle (MCA), and anterior cerebral arteries (ACA), and ophthalmic artery. Panels B and C. Example of recruitment of collateral circulation through the anterior cerebral artery (Panel B) and ophthalmic artery (Panel C) in a patient with right internal carotid occlusion below the level of the ophthalmic artery origin. Note that there is inversion of flow direction in the ACA (dotted arrow), compared to the normal side (arrow head). Panel C shows retrograde flow through the ophthalmic artery (solid arrow), demonstrating collateral circulation.