SU-E-T-88: Evaluation of the Dose-Rate Dependency of GAFCHROMIC EBT3
Bibliographic record
Abstract
Purpose: To evaluate the effect of different dose rates on the optical density (OD) for the commercially available GAFCHROMIC EBT3 film using a Novalis TX. Methods: 3×3 cm2 pieces of GAFCHROMIC EBT3 (A12141101) were placed on the surface of a 20×20×20 cm3 solid water phantom. A 2 cm thick block of solid water was placed on the film for build up. The machine output was monitored using a Farmer-type chamber located at a depth of 10 cm below the films. Chamber ion recombination as a function of dose rate was accounted for, and pressure and temperature were monitored throughout. The monitor unites were calculated such that a certain dose (50, 100, 500 cGy) was delivered at the level of the film. The dose rate was varied between 50 and 1000 cGy/min through changing both machine settings (100–600 MU/min, 1000 MU/min in SRS mode and source-to-surface distance SSD (75–135 cm). The films were scanned 24 hours post irradiation, and the resulting changes in net OD were compared against the corresponding dose rate. Results: Preliminary examination of net OD results shows a small dependence on dose rate, but within the uncertainty of the measurements. As such, within the uncertainties of clinical film dosimetry, the GAFCHROMIC EBT3 films are independent of dose rate (50–1000 cGy/min) irrespective of the total delivered dose (between 50–500 cGy). Conclusion: Results suggest GAFCHROMIC EBT3 films to be dose rate independent to within 3% for a wide range of dose rates (and total delivered doses) that are normally used in clinical settings.
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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 | 0.001 | 0.001 |
| 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".