Figure 1
Top view (down) of the vault where Siemens Oncor Expression accelerator at Osijek University Hospital is placed with marked positions of measurements. (A), (B) and (D) are positions outside the vault, (C) and E are inside the vault. Position E is in isocenter.
Figure 2
Ne utron spectra in measuring positions (A), (B), (C), (D) and (E) for photon field size 10 x 10 cm2 and gantry angles 0° and 270°. (E – 1) is normalized neutron spectrum in measuring position E for simulations with and without vault.
Table 1
Total MC calculated neutron fluence in measuring positions A, B, C, D and E for gantry angles 0° and 270°. Neutron fluence is in number of neutrons per cm2 per electron impinging on target. Results are normalized to source particle
| Measuring position | |||||
|---|---|---|---|---|---|
| Gantry angle | A | B | C | D | E |
| 0° | 5.6 ∙ 10-13 | 5.3 ∙ 10-14 | 3.6 ∙ 10-10 | 8.4 ∙ 10-24 | 1.5 ∙ 10-8 |
| 270° | 6.6 ∙ 10-13 | 3.4 ∙ 10-14 | 4.2 ∙ 10-10 | 1.6 ∙ 10-22 | 1.5 ∙ 10-8 |
Figure 3
Normalized neutron fluence obtained from MC calculations according to the place of origin for all measuring positions and gantry angles 0° and 270°.
Table 2
Neutron dose equivalents in μSv per Gy photon dose in isocenter for all measuring positions and gantry angles 0° and 270°
| Gantry 0° | Gantry 270° | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| A | B | C | D | E | A | B | C | D | E | ||
| (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | (μSv/Gy) | ||
| Poje | LR 115 | 0.04 | 0.08 | 10 | 0.04 | 0.1 | 0.17 | 20 | 0.13 | ||
| et al.5 | Active detector | 0.052 | 0.1 | 14.3 | 0.052 | ||||||
| Our | 0.008 | 0.0006 | 8.2 | 1.3∙10-12 | 3297 | 0.01 | 0.004 | 10.3 | 4.21∙10-11 | 3333 | |
| results | CR-39 | (0.0006) | (0.00004) | (0.6) | (7∙10-14) | (264) | (0.008) | (0.0002) | (0.5) | (2∙10-12) | (202) |