Dosimetric evaluation of unlaminated radiochromic films exposed to an Americium‐241 source using measurements and Monte Carlo simulations
Bibliographic record
Abstract
Abstract Background Radiochromic GafChromic film models are widely used in clinical settings for quality assurance during cancer treatment planning. Although these films are extensively studied in photon dosimetry, research on their application in α‐particle dosimetry remains limited. With the growing use of α‐particles in cancer therapy, it is important to establish film dosimetry protocols tailored to α‐particles. Unlike photons, α‐particles are charged, have a high linear energy transfer, and induce significantly greater biological damage, highlighting the need for specialized dosimetric approaches. Purpose This study aimed to evaluate the response of various unlaminated GafChromic film models including EBT3, EBT‐XD, and HD‐V2, irradiated with an 241 Am α‐particle source, with combined experimental film irradiation and Monte Carlo (MC) simulations. Methods In this study, unlaminated EBT3, EBT‐XD, and HD‐V2 film pieces were irradiated with an 241 Am disk source at various exposure times within a dark box. A detailed comparison was performed across the three film models, focusing on uncertainties and relative dose errors. Film analysis was conducted using a custom Python script, extracting normalized pixel values from the green channel. Additionally, a MC‐based user code was developed using the Geant4 simulation toolkit to model the 241 Am source and calculate the dose rates in the active layers of the films and in water. The mean dose rates were also calculated in a 1 mm diameter region of interest. These simulated dose rates were employed to convert film exposure times into absorbed doses for both the active layers and water, establishing a reference dosimetry protocol for α‐particles across the three radiochromic GafChromic film models. Results The mean dose rates within a 1 mm diameter circular region of interest in the active layers of the three unlaminated GafChromic film models were determined to be 3.77 ± 0.002 Gy/min for EBT3, 4.04 ± 0.0022 Gy/min for EBT‐XD, and 4.25 ± 0.0017 Gy/min for HD‐V2. When the film material was changed to water, the dose rate was increased 14.3% for EBT3, 19.2% for EBT‐XD, and 15.0% for HD‐V2, with EBT3 showing the closest match to water‐equivalence. Calibration curves for each film model were generated by fitting a power function to their responses. Refinements to the dose range were necessary to achieve an uncertainty below the 5% threshold. Among the models, HD‐V2 required the most adjustments to its dose range and exhibited the highest levels of experimental, fit, and total uncertainties, along with the largest relative dose errors. Conclusions This study investigated α‐particle dosimetry protocols for unlaminated EBT3, EBT‐XD, and HD‐V2 GafChromic film models using experimental irradiations and MC simulations. Although EBT3 and EBT‐XD demonstrate strong potential for α‐particle quality assurance in treatment planning, the HD‐V2 film model requires further investigation before it can be recommended for this application.
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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 | 0.001 | 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".