Table 2 FastStroke collateral circulation scoring criteria [22]

5

Normal or increased vessels number in ischemic area, with all vessels in the ischemic area colored red

4

Normal or slightly decreased (≥ 90%) vessels number in ischemic area, with red and green vessels present in the ischemic area, but mostly red vessels

3

Normal or slightly decreased (≥ 90%) vessels number in ischemic area, with red, green, and blue vessels present in the ischemic area; or a decrease (50%~90%) in the vessels number in ischemic area, with vessels colored red and/or green

2

A decrease (50%~90%) in the vessels number in ischemic area, with red, green, and blue vessels present in the ischemic area

1

A significant decrease (< 50%) in the vessels number in ischemic area, with vessels colored red, green, and blue present in the ischemic area

0 points

No visible vessels in the ischemic area on the affected side