Table 4.
Reductions in normal tissue dose volume parameters using online CBCT image guidance and ABC for SBRT of three GTV (16 cc) location
| Normal tissue parameter | Dose absolute reduction value | Dose reduction % | ||||
|---|---|---|---|---|---|---|
| PTV1 | PTV2 | PTV3 | from PTV1 to PTV2 |
from PTV1 to PTV3 |
from PTV2 to PTV3 | |
| Mean lung dose(Gy) | ||||||
| central location | 5.42 | 2.42 | 2.91 | 55.4 | 46.3 | 9.1 |
| peripheral location | 5.05 | 2.47 | 3.22 | 51.1 | 36.3 | 14.8 |
| inferior lobe of lung | 11.46 | 6.07 | 7.47 | 47.0 | 34.8 | 12.2 |
| Lung V20 (%) | ||||||
| central location | 11 | 2.5 | 3.7 | 77.3 | 66.7 | 10.6 |
| peripheral location | 8 | 2.5 | 4 | 68.8 | 50.0 | 18.8 |
| inferior lobe of lung | 21 | 10 | 12 | 52.4 | 42.9 | 9.5 |
| Spinal cord Maximum dose(Gy) | ||||||
| central location | 59.34 | 24.64 | 26.58 | 58.5 | 55.2 | 3.3 |
| peripheral location | 6.91 | 5.99 | 6.32 | 13.3 | 8.4 | 4.9 |
| inferior lobe of lung | 22.50 | 18.67 | 20.00 | 17.0 | 11.1 | 5.9 |
Abbreviations: PTV1 = precorrection margins with ABC; PTV2 = postcorrection margins with ABC; PTV3 = posttreatment residual margin with ABC+CBCT-correction; V20 = volume of both lungs receiving ≥ 20 Gy.