Table 2.
Parameters and their assumed values in the iirp risk model in our study (Shuryak et al 2009a, 2009b, 2011). Indices i and k denote the ith voxel and kth fraction. If the value column is left empty, that signifies that the value varies with voxel or fraction. If two values are listed, the first corresponds to the bladder and the second corresponds to the rectum.
| Parameter | Value | Unit | Definition |
|---|---|---|---|
| N | voxels | Number of voxels in a tissue | |
| Vi | cc | Volume of a voxel | |
| Vt | cc | Volume of a tissue | |
| Y | 0.626, 0.0717 | Sv−1 | Characterizes the dose-dependency of promotion |
| X | 0.151, 2.40 | years/Sv | Characterizes the dose-dependency of initiation |
| δ | 1.68, 0.0193 | 10−3 years−1 | Describes homeostatic regulation of the number of pre-malignant stem cells per niche |
| b | 0.282, 0.217 | years−1 | Pre-malignant niche replication rate |
| Ty | 10 | years | Time since exposure |
| Tx | 60 | years | Age at exposure |
| D(i) | Sv | Total dose for all fractions to a given voxel | |
| d(i,k) | Sv | Fraction dose to a given voxel | |
| K | 38 | fractions | Number of fractions |
| I(i,k) | Sv | Helps to describe the number of cells initiated | |
| F(i,k) | - | Clone survival probability | |
| v | 602.6, 251.2 | cells | Number of stem cells present before irradiation |
| n- or +(i,k) | cells | Normal stem cell number before (-) and after (+) fraction | |
| S(i,k) | - | Surviving fraction of cells | |
| Z | 602.6, 251.2 | cells/niche | Carrying capacity for pre-malignant stem cells per niche |
| α | 0.25 | Sv−1 | Stem cell radiation inactivation constant |
| β | 0.025 | Sv−2 | Stem cell radiation inactivation constant |
| λ | 0.05, 0.10 | time−1 | Maximum net proliferation rate (repopulation) |
| n-(K+1) | v | cells | Number of stem cells at large time after exposure |
| F(K) | 1 | - | Clone survival probability after last fraction |