Evaluation of EBT‐2 model GAFCHROMIC™ film performance in water
Bibliographic record
Abstract
PURPOSE: The authors present results of the measurements on the impact of radiochromic film immersion in water. The impact of film piece size, initial optical density, postimmersion waiting time prior to scanning, and the time film was kept in water has been investigated. The authors also investigated the pathways of water penetration into the film during the film immersion in water. METHODS: To study the impact of water immersion on change in optical density, the authors used various sizes of the latest EBT-2 model GAFCHROMICTM film: 2 x 2, 4 x 4, and 8 x 8 in.2. In addition, to test any existing dependence of the film's optical density on water diffusion, the authors used two sets of films: Unexposed (0 Gy) and film pieces exposed to a dose of 3 Gy. Times that film pieces were left in water ranged from 30 min to 24 h, and once the film was permanently removed from water, the authors also studied the impact of the scanning time (deltat) that ranged from 0 (films scanned right after removal from water) to 72 h postimmersion. RESULTS: While the penetration depth can reach as much as 9 mm around the edges of the EBT-2 GAFCHROMIC film, the anticipated dose error due to the change in optical density due to the water immersion appears to be negligible for the short immersions of the order of 30 min. However, as the immersion time increases, the anticipated dose error may reach 22 cGy on a 2 x 2 in.2 piece of film, which corresponds to 7% dose error at 3 Gy of measured dose. CONCLUSIONS: In this work, the authors report on an undoubted impact of radiochromic film immersion in water on the measured change in optical density, which may lead to systematic errors in dose measurements if the film is kept in water for longer periods of time. The magnitude of the impact depends on many parameters: Size of the film piece, initial optical density, postimmersion waiting time prior to scanning (defined by the current radiochromic film dosimetry protocol in. place), and the time film was kept in water. The authors also suggested various approaches in correcting for the change in netOD due to water penetration into the film, but the authors believe that the use of the control film piece would be the most appropriate.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".