Table 4.
Parameters to model the absorbed dose from un-attenuated leakage photon fluence.
| Symbol | Description | In-Plane | Cross-Plane | Source |
|---|---|---|---|---|
| αPC,σ | Adjustment parameter for source width for the leakage fluence attenuated by the primary collimator | 0.87 | 4.13 | This Worka |
| q | Divergence factor for the leakage photon fluence | 1.58 | 1.11 | “ |
| αSC | Adjustment factor to the μt of the secondary collimator | 1.46 | 1.85 | “ |
| αPC | Adjustment factor to the μt of the primary collimator | 0.32 | 0.28 | “ |
| SIDPC | Distance from the focus of the primary collimator cone to isocenter (cm) | 112 | “ | |
| αSID | Adjustment factor for the SIDPC in each plane | 1.09 | 0.87 | “ |
| μSC | Linear attenuation coefficient of the secondary collimator (1/cm) | 0.77 | 0.58 | (NCRP, 2005) |
| tSC | Secondary collimator thickness (cm) | 7.8 | 11.2 | Personal Communication, Elekta, Stockholm, Sweden |
| μwSC | Effective attenuation of the primary collimator | 0.64 | (NCRP, 2005), Personal Communication, Elekta, Stockholm, Sweden | |
| x̄PC | Projected location of the primary collimator in the isocentric plane (cm) | 25 | Personal Communication, Elekta, Stockholm, Sweden | |
a
From iterative fitting procedure