Table 2.
Volumetric index and interobserver variation of FDG-PET/CT–, T2W-MRI–, and T2W + DW-MRI–based GTV delineations
| Case | Mean volume (cm³)∗ |
Generalized conformity index |
Central overall SD (RMS, cm)† |
||||||
|---|---|---|---|---|---|---|---|---|---|
| PET/CT | T2W-MRI | T2W + DW-MRI | PET/CT | T2W-MRI | T2W + DW-MRI | PET/CT | T2W-MRI | T2W + DW-MRI | |
| 1 | 47.8 ± 7.0 | 40.6 ± 6.3 | 38.2 ± 6.1 | 0.68 | 0.72 | 0.72 | 0.13 | 0.06 | 0.07 |
| 2 | 46.3 ± 3.7 | 32.7 ± 4.2 | 32.4 ± 4.5 | 0.75 | 0.79 | 0.79 | 0.13 | 0.09 | 0.09 |
| 3 | 75.5 ± 9.7 | 63.8 ± 8.9 | 64.6 ± 6.1 | 0.74 | 0.67 | 0.67 | 0.11 | 0.14 | 0.14 |
| 4 | 39.6 ± 8.1 | 38.0 ± 16.1 | 33.1 ± 8.2 | 0.62 | 0.43 | 0.43 | 0.20 | 0.12 | 0.27 |
| 5 | 22.5 ± 8.6 | 21.9 ± 3.8 | 16.4 ± 3.6 | 0.53 | 0.62 | 0.62 | 0.08 | 0.08 | 0.10 |
| 6 | 11.2 ± 0.8 | 11.7 ± 1.4 | 11.5 ± 1.7 | 0.73 | 0.71 | 0.71 | 0.09 | 0.10 | 0.09 |
| Mean | 40.5 | 34.8 | 32.7 | 0.68 | 0.66 | 0.68 | 0.13 | 0.10 | 0.14 |
 | |||||||||
Abbreviations: DW = diffusion-weighted; FDG-PET/CT = fluorodeoxyglucose positron emission tomography/computed tomography; GTV = gross tumor volume; SD = standard deviation; T2W = T2-weighted; MRI = magnetic resonance imaging; RMS = root mean square.
∗
Mean per patient and modality ± standard deviation. P < .05 considered statistically significant; calculated between the means per modality, paired-sample t test (2-tailed).
†
Central overall SD: quadratic mean of the local SD weighted for surface (RMS) of the central part of the median surface where 100% of the observers agreed delineations.