Sci-Thurs PM: Delivery-03: Optical imaging of microscopic radiation dose gradients using a digital microscope
Bibliographic record
Abstract
Using superior localization and immobilization methods, stereotactic radiosurgery is capable of delivering spheres of dose as small as a few millimetres in diameter to intracranial targets. For targets abutting critical structures, the most conformal treatments minimize adverse radiation side effects and it is important, therefore, to ensure proper quality assurance prior to delivering high doses of radiation to eloquent brain locations in a single fraction. This work examines the capability of a digital microscope, with translation stage and associated software, to resolve dose gradients in Gafchromic EBT™ film at the micron level. In order to validate the microscope-film system from a radiation physics approach, films were irradiated to produce very steep penumbrae by using very small fields, lower photon energies and minimal geometric penumbra contribution. Orthovoltage film irradiations were done by placing films in phantom beneath pinhole collimators. The experimentally determined off-axis dose profiles were compared with Monte Carlo computer simulations which replicated the irradiation geometry and served to validate our measured data. The measured 80% - 20% penumbral widths were 46 μm ± 26 μm (100 kVp, 2 mm field size) and 69 μm ± 27 μm (300 kVp, 2 mm field size). In the energy range covered, the measured penumbral widths agreed with Monte Carlo computer simulations within experimental uncertainty. The effects of noise originating from both the film and the microscope system are discussed and improvements to this system suggested.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.031 | 0.006 |
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".