Influence of Reference Volume (Whole Brain or Cerebellum) on Gray-Level Normalization Parameters
| Method | α Variations (%) (mean ± SD) |
|---|---|
| Max vs. Max-cer (operator 1) | 6 ± 2 |
| Max vs. Max-cer (operator 2) | 4 ± 4 |
| Mean vs. Mean-cer (operator 1) | 4 ± 5 |
| Mean vs. Mean-cer (operator 2) | 4 ± 4 |
| Max-cer (operator 1 vs. 2) | 2 ± 2 |
| Mean-cer (operator 1 vs. 2) | 3 ± 1 |
Reference volumes were selected automatically (whole brain) or interactively (cerebellum) by 2 different operators. For the 2 methods Max and Mean, statistics were calculated within patient population from absolute value of α discrepancies observed with different reference volumes.