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. Author manuscript; available in PMC: 2014 Sep 11.
Published in final edited form as: Stroke. 2013 Aug 6;44(9):2650–2663. doi: 10.1161/STROKEAHA.113.001972

Table 4.

American Society of Interventional and Therapeutic Neuroradiology Collateral Grading System

ACG Grades Definitions
Grade 0 No collaterals visible to the ischemic site
Grade 1 Slow collaterals to the periphery of the ischemic site, with
persistence of some of the defect
Grade 2 Rapid collaterals to the periphery of the ischemic site, with
persistence of the defect, and only to a portion of the ischemic
territory
Grade 3 Collaterals with slow but complete angiographic blood flow of
the ischemic bed by the late venous phase
Grade 4 Complete and rapid collateral blood flow to the vascular bed in
the entire ischemic territory by retrograde perfusion
N/A Not applicable based on the territory or injections available

ACG indicates the American Society of Interventional and Therapeutic Neuroradiology collateral grading.