A comparison between calculated and experimental<i>k</i><sub><i>Q</i></sub>photon beam quality correction factors
Bibliographic record
Abstract
To validate the calculated values of kQ for high-energy photon beams given in the International Code of Practice for radiotherapy dosimetry based on water-absorbed-dose standards, a comparison with experimental values derived in standards laboratories and in clinical beams has been made. The study includes a compilation of experimental values for ionization chambers of the type NE2561/2611, NE2571, PTW30001 and PR06. The energy dependence of the G(Fe3+) ratio of high-energy x-rays to 60Co gamma-rays by Klassen et al is taken into account for all the Fricke-derived values. For three of the chamber types analysed, the comparison shows that the calculated values are a very good estimate of the average values of kQ in the entire range of photon beam qualities available for clinical use. For the NE2571 chamber type a difference which increases with energy between calculated and experimental kQ factors has been observed; however, the largest difference with a fit describing the entire set of experimental data is always smaller than 0.4%. It is concluded that if the recommendation of the Code of Practice for an individual calibration of the user's chamber at a range of photon beam qualities is not available, the use of calculated kQ factors will yield absorbed dose to water determinations accurate within the uncertainty limits of the majority of experimental data available. The good agreement between calculated and measured values, obtained for practically all the experimental data using TPR(20,10) as photon beam quality specifier, is not satisfied in some cases for two high-energy soft beams used at the Canadian NRC. There appears to be no justification for a change to a different photon beam quality specifier solely on the grounds that such a limited set of data is not described by the same distributions as the rest of the experimental data.
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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 | 0.005 | 0.017 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".