Table 3 Contribution of primary and scattered photons in the fluence and average energy of 6 MV photons at different depths inside the water for open and grid fields of 10 × 10 and 20 × 20 cm2. The relative uncertainty in fluence calculations was kept within 1%.
From: Beam quality and the mystery behind the lower percentage depth dose in grid radiation therapy
Depth | Open field | Grid field | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Brass grid | Cerrobend grid | |||||||||
Primary | Secondary | Total | Primary | Secondary | Total | Primary | Secondary | Total | ||
Photon fluence (108/cm2/MU) | 10 × 10 cm2 treatment field | |||||||||
1.5 cm | 12.89 | 4.09 | 16.98 | 11.46 | 1.29 | 12.75 | 11.43 | 1.16 | 12.59 | |
5 cm | 9.74 | 5.67 | 15.41 | 8.67 | 1.63 | 10.30 | 8.65 | 1.47 | 10.12 | |
10 cm | 6.62 | 5.55 | 12.17 | 5.91 | 1.55 | 7.47 | 5.90 | 1.39 | 7.29 | |
Photon average energy (MeV) | ||||||||||
1.5 cm | 1.83 | 0.35 | 1.47 | 1.90 | 0.59 | 1.77 | 1.90 | 0.57 | 1.78 | |
5 cm | 1.92 | 0.47 | 1.38 | 1.99 | 0.63 | 1.78 | 1.99 | 0.62 | 1.79 | |
10 cm | 2.04 | 0.55 | 1.36 | 2.12 | 0.69 | 1.82 | 2.12 | 0.67 | 1.84 | |
Photon fluence (108/cm2/MU) | 20 × 20 cm2 treatment field | |||||||||
1.5 cm | 13.22 | 6.94 | 20.17 | 11.50 | 2.31 | 13.81 | 11.45 | 1.93 | 13.39 | |
5 cm | 10.02 | 9.80 | 19.82 | 8.71 | 2.92 | 11.63 | 8.68 | 2.50 | 11.18 | |
10 cm | 6.86 | 10.36 | 17.22 | 5.95 | 2.96 | 8.91 | 5.93 | 2.56 | 8.49 | |
Photon average energy (MeV) | ||||||||||
1.5 cm | 1.81 | 0.28 | 1.28 | 1.89 | 0.57 | 1.67 | 1.90 | 0.52 | 1.70 | |
5 cm | 1.89 | 0.35 | 1.13 | 1.99 | 0.54 | 1.62 | 1.99 | 0.51 | 1.66 | |
10 cm | 2.00 | 0.40 | 1.03 | 2.11 | 0.54 | 1.59 | 2.11 | 0.52 | 1.63 | |
