TU‐A‐BRB‐11: A New Method for the Measurement of Reference Dosimetric Quantities in Electron Beams
Bibliographic record
Abstract
Purpose: To present and confirm the accuracy of a new method to extract data for reference dosimetry in electron beams from depth‐ionization measurements. Methods: Depth‐ionization curves are measured in water using NRC reference ion chambers and several plane‐parallel chambers in 4 to 18 MeV electron beams from the Elekta Precise clinical linear accelerator. To extract useful information from depth‐ionization results, the accuracy of setting the chamber position must be established. For this purpose, differences in the depth at which the chamber's ionization reading falls to 50% of its maximum value are used to derive EPOM values relative to those of reference chambers which have been previously established (Lacroix et al., Med. Phys. 37 (2010) 4331). After validation of positioning accuracy, relative ion chamber perturbation factors are determined using the ratio of readings to those of reference ion chambers as a function of mean electron energy, which changes smoothly with depth.Results:Repeatable results for EPOM at the 0.1 mm level indicate little uncertainty from positioning. Different chambers of the same type give EPOM results that differ by less than 0.2 mm, suggesting insignificant chamber‐to‐chamber variability. Values of EPOM at I50 determined for 4 to 18 MeV beams do not exhibit significant variation with beam energy. For well‐behaved chambers, relative perturbation factors at the same mean electron energy are consistent regardless of the incident beam energy. Relative perturbation factors for the same chambers repeated using a different reference chamber after several days are unchanged within 0.3%. Relative perturbation factors for the NACP and Roos chambers agree with published data. Conclusions: These measurements show promising results for the determination of reference dosimetry data from depth‐ionization curves. Ultimately, these relative measurements will be compared against the NRC primary standard calorimeter to get absolute perturbation factors that will prove valuable for updated dosimetry protocols.
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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 | 0.004 | 0.008 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.005 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 0.004 |
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".