TABLE III.
Qualitative analysis of low contrast detectability for each imaging system. The uncertainty in each measurement is half of the smallest increment of the measurement scale (number of low contrast objects visualized).
| Visual low-contrast object detection | ||||
|---|---|---|---|---|
| Nominal (20.5 cm) | With ring (30.5 cm) | |||
| Protocol | Supra 1.0% visualized | Supra 0.5% visualized | Supra 1.0% visualized | Supra 0.5% visualized |
| Varian OBI Head | 1 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| Varian OBI Pelvis | 6 ± 0.5 | 3 ± 0.5 | 1 ± 0.5 | 0 ± 0.5 |
| Varian OBI Thorax | 4 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| Varian OBI Spotlight | 5 ± 0.5 | 1 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| Elekta XVI HN S20 | 0 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| Elekta XVI Pelvis M20 | 4 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| Elekta XVI Chest M20 | 4 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| Elekta XVI PS S10 | 1 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| GE Head | 4 ± 0.5 | 2 ± 0.5 | 0 ± 0.5 | 0 ± 0.5 |
| GE Pelvis (300 mAs) | 6 ± 0.5 | 4 ± 0.5 | 2 ± 0.5 | 0 ± 0.5 |
| GE Pelvis (600 mAs) | 8 ± 0.5 | 5 ± 0.5 | 3 ± 0.5 | 0 ± 0.5 |