SU‐E‐T‐22: Is the Residual Range a Universal Quantity to Specify the Quality of Modulated Proton Beams?
Bibliographic record
Abstract
Purpose: To investigate the validity of using the residual range as a universal quantity to specify the quality of modulated proton beams. Methods: We used TOPAS (Tool for Particle Simulation), an application of the Geant4 toolkit, to simulate absorbed dose and stopping‐power distributions from a commercial passive scattering nozzle. We used the standard physics lists from Geant4 in the simulations. All particles were included, as well as physics models for nuclear interactions. No variance reduction techniques were used. Dose and averaged stopping‐power as functions of depth were scored in a water box with 320 scoring volumes of 15 × 15 × 0.1 cm3. Stopping‐power spectra were scored in a15 × 15 × 0.1 cm3 volume located in the middle of SOBPs. All particles were considered in the dose scoring. Only protons (primary and secondary) were considered in the scoring of stopping‐power. Results: For the same residual range, differences in averaged stopping‐power values of up to 13% were observed for a 200 MeV beam with modulations of 4 cm and 8 cm, respectively. Simulations of four modulated proton energies with the same SOBP of 8 cm showed differences of up to 13% in the averaged stopping‐power values even in the SOBP region. We also simulated stopping power spectra in the middle of 8 cm SOBPs for four modulated proton energies. The averaged stopping‐power values calculated from the spectra were within 3%, however, their distributions were very different with full width at half‐maximum 150% larger for the 250 MeV beam compared to that of the 140 MeV beam. Conclusion: Large differences in the averaged stopping‐power values and stopping‐power spectra were observed for the same residual range. Determining whether these differences have a significant effect on the response of radiation detectors exposed to proton beams requires further investigation. Natural Sciences and Engineering Research Council of Canada and Ontario Graduate Scholarship Program, Ontario Ministry of Training, Colleges and Universities
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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 | 0.002 | 0.011 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".