Grading scale for collateral venous flow. Images shown are sagittal MIPs of either the left or right side of the neck from TRICKS MRV from the phase with the most venous opacification. Collateral scorings shown are: (A) none, 0, (B) mild, 1, (C) moderate, 2, and (D) severe, 3. In severe cases, prominent collaterals were sometimes seen over the posterior neck regions, as in this example.