MR imaging-based grading methods
| Modality | Description | Author (No.) | Acute (<24 hr from Symptom Onset)/Nonacute | Reliability Assessed? | Prognostic Significance of Good Collateral Flow Grade in Acute Stroke |
|---|---|---|---|---|---|
| FADS | Late FADS implies collateral flow | Martel et al84 (22) | Acute | No | NS |
| QMRA | Increased flow ipsilateral to steno-occlusive disease | Ruland et al83 (16) | Nonacute | No | N/A |
| Phase-contrast MRA | Flow from posterior to anterior circulation | Schomer et al82 (29) | Nonacute | No | N/A |
| FLAIR | FLAIR hyperintensities as a marker of collateral flow | Liebeskind85 (91) | Acute | No | NS85,19,27,31,81 |
| Kamran et al27 (8) | |||||
| Noguchi et al31 (5) | |||||
| Sanossian et al19 (74) | |||||
| Lee et al81 (52) | |||||
| T2*-weighted MRI | Abnormal visualization of leptomeningeal vessels | Hermier et al80 (48) | Acute | No | NS |
| PWI | Delayed perfusion sign visualized on PWI | Hermier et al79 (29) | Acute | No | NS |
| ASL | Quantitative distal collateral flow measurement | Wu et al13 (51) | Nonacute | No | N/A |
| TASL | Collateral flow assessment based on ASPECTS | Chng et al51 (18) | Nonacute | No | N/A |
| CASL | Collateral flow inferred from delayed arterial flow | Chalela et al78 (15) | Acute | No | NS |
Note:—NS indicates not stated; N/A, not applicable; FADS, factor analysis of dynamic structures; QMRA, quantitative MRA; TASL, territorial arterial spin labelling; CASL, continuous arterial spin-labeled/labeling; ASPECTS, Alberta Stroke Program Early CT Score.