Table 2.
Predicted exposures of stray radiation from craniospinal irradiation using passively scattered proton beams, including absorbed dose of stray radiation per therapeutic absorbed dose (DT/D), radiation weighting factor (wR) for neutrons, equivalent dose from stray radiation per therapeutic absorbed dose (HT/DT), lifetime risk of fatal or non-fatal second cancer (RT) from stray radiation corresponding to the entire three-field, 36 Gy treatment and the corresponding percentage of risk in all tissues and organs (RT/R). The values of absorbed dose and radiation weighting factor values are listed separately for the cranial, superior spinal and inferior spinal treatment fields. These data were simulated for a commercially available treatment unit at The University of Texas M D Anderson Cancer Center (Newhauser et al 2007a).
| DT/D (Gy/Gy) | wR(Sv/Gy) | HT/D (Sv/Gy) |
RT (%) |
RT/R (%) |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Organ | Cranial | Sup spine | Inf spine | Cranial | Sup spline | Inf spine | Cranial | Sup spine | Inf spine | ||
| Gonads | 2.30 × 10−5 | 3.71 × 10−5 | 5.97 × 10−5 | 6.7 | 6.7 | 7.2 | 1.54 × 10−4 | 2.49 × 10−4 | 4.30 × 10−4 | 0.00 | 0.1 |
| Bone marrow (red) | 1.06 × 10−4 | 2.76 × 10−4 | 2.27 × 10−4 | 7.8 | 7.9 | 8.1 | 8.27 × 10−4 | 2.18 × 10−3 | 1.84 × 10−3 | 0.09 | 2.6 |
| Colon | 7.06 × 10−5 | 9.36 × 10−5 | 3.72 × 10−4 | 7.8 | 8.1 | 9.2 | 5.51 × 10−4 | 7.58 × 10−4 | 3.42 × 10−3 | 0.26 | 7.8 |
| Lung | 1.45 × 10−4 | 5.80 × 10−4 | 2.40 × 10−4 | 8.0 | 8.5 | 8.1 | 1.16 × 10−3 | 4.93 × 10−3 | 1.94 × 10−3 | 0.26 | 7.6 |
| Stomach | 8.94 × 10−5 | 1.86 × 10−4 | 4.04 × 10−4 | 8.0 | 8.3 | 9.1 | 7.15 × 10−4 | 1.54 × 10−3 | 3.68 × 10−3 | 0.26 | 7.7 |
| Bladder | 3.52 × 10−5 | 4.45 × 10−5 | 1.05 × 10−4 | 7.2 | 7.2 | 7.8 | 2.53 × 10−4 | 3.20 × 10−4 | 8.19 × 10−4 | 0.03 | 0.9 |
| Breast | 1.56 × 10−4 | 3.07 × 10−4 | 2.44 × 10−4 | 8.1 | 8.4 | 8.3 | 1.26 × 10−3 | 2.58 × 10−3 | 2.03 × 10−3 | 0.08 | 2.5 |
| Liver | 8.82 × 10−5 | 1.55 × 10−4 | 4.04 × 10−4 | 8.0 | 8.2 | 9.1 | 7.06 × 10−4 | 1.27 × 10−3 | 3.68 × 10−3 | 0.03 | 0.9 |
| Esophagus | 2.00 × 10−4 | 1.08 × 10−3 | 1.20 × 10−4 | 7.9 | 9.1 | 7.5 | 1.58 × 10−3 | 9.83 × 10−3 | 9.00 × 10−4 | 0.14 | 4.1 |
| Thyroid | 2.00 × 10−4 | 1.08 × 10−3 | 1.20 × 10−4 | 7.9 | 9.1 | 7.5 | 1.58 × 10−3 | 9.83 × 10−3 | 9.00 × 10−4 | 0.35 | 10.4 |
| Skin | 1.06 × 10−4 | 2.76 × 10−4 | 2.27 × 10−4 | 7.8 | 7.9 | 8.1 | 8.27 × 10−4 | 2.18 × 10−3 | 1.84 × 10−3 | 1.74 | 51.4 |
| Bone surface | 1.06 × 10−4 | 2.76 × 10−4 | 2.27 × 10−4 | 7.8 | 7.9 | 8.1 | 8.27 × 10−4 | 2.18 × 10−3 | 1.84 × 10−3 | 0.01 | 0.4 |
| Remainder | 1.06 × 10−4 | 2.76 × 10−4 | 2.27 × 10−4 | 7.8 | 7.9 | 8.1 | 8.27 × 10−4 | 2.18 × 10−3 | 1.84 × 10−3 | 0.12 | 3.6 |