Comparison of intraobserver and interobserver variability (SDDrel) in the four flow territories
| Variability | SDDrel (%) | |||||
|---|---|---|---|---|---|---|
| CBV | CBF | MTT | CBV ratio | CBF ratio | MTT ratio | |
| Intraobserver | ||||||
| ACA | 17 | 18 | 5 | 12 | 12 | 4 |
| MCA | 15 | 17 | 5 | 5 | 6 | 5 |
| Basal ganglia | 16 | 17 | 6 | 8 | 8 | 7 |
| PCA | 18 | 18 | 6 | 16 | 12 | 8 |
| P* | .730 | .884 | .210 | .249 | .029 | .090 |
| Interobserver | ||||||
| ACA | 16 | 19 | 8 | 15 | 16 | 8 |
| MCA | 11 | 15 | 6 | 11 | 9 | 6 |
| Basal ganglia | 17 | 15 | 8 | 13 | 8 | 8 |
| PCA | 18 | 15 | 9 | 23 | 17 | 10 |
| P* | .005 | .005 | .179 | .000 | .001 | .001 |
Note:—SDDrel indicates SDs of relative differences; CBV, cerebral blood volume; CBF, cerebral blood flow; MTT, mean transit time; ACA, anterior cerebral artery; MCA, middle cerebral artery; PCA, posterior cerebral artery. The test of Levine for homogeneity of variance was used to check whether variability differed between flow territories. The least variability was commonly seen for the MCA territory. For CTP ratios, the largest variability was usually found for the PCA territory.
* Test of Levine for homogeneity of variance