Table 3.
Predicted exposures of stray radiation from a craniospinal irradiation using scanned proton beams, including absorbed dose of stray radiation per therapeutic absorbed dose (DT/D), radiation weighting factor (wR) for neutrons, equivalent dose of 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. The dosimetric data were simulated for an idealized scanned-beam proton therapy unit from which no leakage radiation emanated, i.e. only stray radiation generated internally to the patient was considered.
| DT/D (Gy/Gy) | wR(Sv/Gy) | HT/D (Sv/Gy] |
RT (%) |
RT/R (%) |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Organ | Cranial | Sup spine | Inf spine | Cranial | Sup spine | Inf spine | Cranial | Sup spine | Inf spine | ||
| Gonads | 7.12 × 10−7 | 1.94 × 10−6 | 6.14 × 10−6 | 5.9 | 7.3 | 8.4 | 4.18 × 10−6 | 1.41 × 10−5 | 5.16 × 10−5 | 0.0004 | 0.02 |
| Bone marrow (red) | 1.66 × 10−5 | 1.26 × 10−4 | 7.66 × 10−5 | 7.6 | 9.1 | 9.5 | 1.26 × 10−4 | 1.15 × 10−3 | 7.28 × 10−4 | 0.04 | 2.3 |
| Colon | 1.65 × 10−6 | 5.12 × 10−6 | 1.19 × 10−4 | 7.1 | 9.3 | 10.9 | 1.18 × 10−5 | 4.79 × 10−5 | 1.30 × 10−3 | 0.08 | 4.9 |
| Lung | 3.43 × 10−5 | 2.16 × 10−4 | 4.79 × 10−5 | 8.5 | 10.4 | 10.1 | 2.92 × 10−4 | 2.25 × 10−3 | 4.84 × 10−4 | 0.10 | 6.3 |
| Stomach | 5.38 × 10−1 | 6.69 × 10−5 | 2.23 × 10−4 | 8.1 | 10.2 | 10.7 | 4.34 × 10−5 | 6.81 × 10−4 | 2.4 × 10−3 | 0.14 | 8.8 |
| Bladder | 5.46 × 10−7 | 1.97 × 10−6 | 2.15 × 10−5 | 7.1 | 7.8 | 9.5 | 3.90 × 10−6 | 1.53 × 10−5 | 2.05 × 10−4 | 0.00 | 0.3 |
| Breast | 1.01 × 10−5 | 1.53 × 10−4 | 8.97 × 10−5 | 8.6 | 9.6 | 9.4 | 8.68 × 10−5 | 1.47 × 10−3 | 8.46 × 10−4 | 0.03 | 2.2 |
| Liver | 3.57 × 10−6 | 5.96 × 10−5 | 5.96 × 10−4 | 7.9 | 10.3 | 10.8 | 2.82 × 10−5 | 6.14 × 10−4 | 2.12 × 10−3 | 0.02 | 1.0 |
| Esophagus | 5.22 × 10−5 | 7.73 × 10−4 | 3.37 × 10−5 | 9.3 | 10.5 | 9.4 | 4.88 × 10−4 | 8.16 × 10−3 | 3.16 10−4 | 0.11 | 6.8 |
| Thyroid | 5.22 × 10−5 | 7.73 × 10−4 | 3.37 × 10−5 | 9.3 | 10.5 | 9.4 | 4.88 × 10−4 | 8.16 × 10−3 | 3.16 × 10−4 | 0.27 | 17.3 |
| Skin | 1.66 × 10−5 | 1.26 × 10−4 | 7.66 × 10−5 | 7.6 | 9.1 | 9.5 | 1.26 × 10−4 | 1.15 × 10−3 | 7.28 × 10−4 | 0.72 | 46.3 |
| Bone Surface | 1.66 × 10−5 | 1.26 × 10−4 | 7.66 × 10−5 | 7.6 | 9.1 | 9.5 | 1.26 × 10−4 | 1.15 × 10−3 | 7.28 10−4 | 0.01 | 0.3 |
| Remainder | 1.66 × 10−5 | 1.26 × 10−4 | 7.66 × 10−5 | 7.6 | 9.1 | 9.5 | 1.26 × 10−4 | 1.15 × 10−3 | 7.28 × 10−4 | 0.05 | 3.3 |