Table 2.
Volumetric analysis and interobserver variation in CT and FDG-PET/CT based GTV delineations of six oesophageal cancer patients for 20 observers.
| Case | Mean volume in cm3 |
Generalized Conformity Index (CIgen) |
Cranial delineation variation 1SD (cm) |
Caudal delineation variation 1SD (cm) |
Central overall SD (RMS, cm) |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CT | FDG-PET/CT | p* | CT | FDG-PET/CT | CT | FDG-PET/CT | p** | CT | FDG-PET/CT | p** | CT | FDG-PET/CT | |
| 1 | 51.0 | 53.1 | 0.362 | 0.67 | 0.69 | 1.5 | 1.3 | 0.597 | 0.9 | 0.4 | 0.002 | 0.17 | 0.17 |
| 2 | 54.2 | 49.2 | 0.001 | 0.76 | 0.77 | 0.3 | 0.4 | 0.295 | 1.0 | 0.5 | 0.005 | 0.17 | 0.15 |
| 3 | 65.8 | 76.7 | 0.002 | 0.66 | 0.69 | 1.1 | 0.4 | <0.001 | 0.7 | 0.8 | 0.526 | 0.12 | 0.13 |
| 4 | 52.0 | 45.0 | 0.005 | 0.62 | 0.65 | 1.0 | 0.9 | 0.594 | 0.8 | 0.7 | 0.671 | 0.25 | 0.25 |
| 5 | 28.3 | 26.8 | 0.402 | 0.58 | 0.56 | 1.1 | 1.0 | 0.792 | 0.6 | 0.8 | 0.165 | 0.10 | 0.09 |
| 6 | 13.3 | 12.4 | 0.020 | 0.75 | 0.76 | 0.3 | 0.3 | 0.556 | 0.2 | 0.2 | 0.978 | 0.11 | 0.10 |
Abbreviations: CT = computed tomography; FDG-PET = fluorodeoxyglucose-positron emission tomography; SD = standard deviation; CIgen = generalized conformity index (sum of the common divided by the sum of the encompassing volumes between each pair of observers). Cranial/caudal delineation variation = SD in the position of the most cranial/caudal delineated slice over the observers. Central overall SD = quadratic mean of the local SD weighted for surface (RMS = Root Mean Square) of the central part of the median surface where 100% of the observers agreed to delineate.
p < 0.05 considered statistically significant, one-sample T-test (2-tailed).
p < 0.05 considered statistically significant, 2-sided F-test.