External beam irradiation angle measurement using Cerenkov emission II: Detector characterization and applications
Bibliographic record
Abstract
Due to its angular dependency, Cerenkov light has long been considered a contamination signal in plastic scintillating fiber dosimeters. In this study, we propose a novel approach designed to take advantage of this angular dependency to perform a direct measurement of an external beam radiation angle of incidence. A Cerenkov probe composed of a 10-mm long filtered sensitive volume of clear PMMA optical fiber was built. Both filtered and raw Cerenkov signals from the transport fiber were collected through a single 1-mm diameter transport fiber of 17-m long. An independent optical guide composed of 10-mm BCF12 scintillating fiber was also used for simultaneous dose measurements. Each detector signal was dose calibrated and the total signal was unmixed using a hyperspectral approach. A cylindrical phantom was then used to obtain an angular calibration curve for fixed dose irradiations and perform incident angle measurements for various doses using both electron and photon beams. The beam nominal energy was found to have a significant impact on the shapes of the angular calibration curves obtained for irradiation angle measurements. This can be linked to the electron energy spectrum dependency of the Cerenkov cone semi angle. Irradiation angle measurements exhibit an absolute mean error of 1.86 and 1.02 degree at 6 and 18 MV, respectively. Similar results were obtained with four different electron beam energies and the absolute mean error reaches 1.97, 1.66, 1.45 and 0.95 degree at 9, 12, 16 and 20 MeV, respectively. Reducing the numerical aperture of the Cerenkov probe leads to an increased angular dependency for the lowest energy while no major changes were observed at higher energy. This allowed irradiation angle measurements at 6 MeV with a mean absolute error of 4.82 degree. The detector offers promising perspectives for external beam radiotherapy and brachytherapy applications.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".