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. 2009 Mar;30(3):525–531. doi: 10.3174/ajnr.A1408

Fig 2.

Fig 2.

MTT and CTA source images (CTA-SI) of 4 different cases, each demonstrating prolonged MTT from a left MCA territory ischemia. CS grading is demonstrated for each collateral grade. A, Absence of vessels on CTA-SI is consistent with a CS of 0. B, A score of 1 indicates collateral supply filling ≤50% but >0% of the occluded MCA territory. C, A score of 2 is given for collateral supply filling >50% but <100% of the occluded MCA territory. D, A score of 3 is given for 100% collateral supply of the occluded MCA territory.