Maximum RBE change in <sup>192</sup> Ir, <sup>125</sup> I, and <sup>169</sup> Yb brachytherapy and the corresponding effect on treatment planning
Bibliographic record
Abstract
Abstract Purpose: The purpose of this study was to examine RBE variation as a function of distance from the radioactive source, and the potential impact of this variation on a realistic prostate brachytherapy treatment plan. Methods: Three brachytherapy sources ( 125 I, 192 Ir, and 169 Yb) were modelled in Geant4 Monte Carlo code, and the resulting electron energy spectrum in water in 3D space around these sources was scored (voxel size of 2 mm 3 ). With this energy spectrum, microdosimetric techniques were used to calculate the maximum RBE, RBE M , as a function of distance from the source. RBE M of 125 I relative to 192 Ir was calculated in order to validate simulations against literature; all other RBE M calculations were done by normalizing electron fluence at various distances to the source position. In order to examine the impact of RBE M variation in treatment planning, a realistic 192 Ir prostate plan was re-evaluated in terms of RBE instead of absorbed dose. Results: The RBE M of 125 I, 192 Ir, and 169 Yb at 8 cm away from the source was 0.994 (+/−0.002), 1.030 (+/−0.003), and 1.066 (+/−0.008), respectively. RBE M in the HDR prostate treatment plan exhibited several hot (+3.6% in RBE M ) spots. Conclusions: The large increase RBE M observed in 169 Yb has not yet been described in the literature. Despite the presence of radiobiological hotspots in the HDR treatment, these variations are likely nominal and clinically insignificant.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".