Dosimetric characterization of a <sup>90</sup> Sr <sup>90</sup> Y Pterygium applicator with radiochromic film and Monte Carlo Simulations
Bibliographic record
Abstract
Abstract Objective . β -emitting radionuclides, such as 90 Sr 90 Y, are widely used in clinical settings for the treatment of both benign and malignant lesions, particularly as surface applicators. Despite their clinical relevance, the three-dimensional dose distributions delivered by these applicators remain inadequately characterized using Monte Carlo simulations, the current gold standard for dose calculation. This study aims to address these limitations by characterizing the three-dimensional dose distribution of a commonly used 90 Sr 90 Y Pterygium applicator. The goals include generating accurate percent-depth-dose (PDD) curves and validating a custom irradiation setup using radiochromic film and Monte Carlo simulations to enable accessible, reproducible, and highly precise radiobiology experiments. Approach . A Monte Carlo dose calculation software based on Geant4 10.02.p02 was developed, and the Amersham SIA 20 Pterygium applicator, a stacked film setup with 30 EBT-XD GafChromic ® films, and a film-cell irradiation setup (a film layer, cell monolayer, and growth media) were modeled. The dose rate was averaged over the 8.2 mm diameter active area on the surface in water in both the stacked film setup and the film-cell setup. The spectrum of the source was also calculated. An experimental PDD was generated by irradiating stacked films and was compared to the Monte Carlo simulations. Main results . The measured and computed PDDs agreed within 2% within 2.6 mm of depth. The dose rates were 28.30, 26.48, 21.23, and 22.76 cGy s −1 on the surface in water, in the film active layer, in the cell monolayer, and in the growth media, respectively, compared to the manufacturer’s nominal value of 27 cGy s −1 . Significance . A Monte Carlo-validated PDD curve of the source was generated in a stacked film setup using EBT-XD GafChromic ® film. A custom film-cell irradiation setup was characterized for future radiobiology experiments.
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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 | 0.000 | 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".