TH‐C‐BRB‐06: Advanced Dosimetry Techniques for Accurate Dose Measurement of Small and Nonstandard Fields
Bibliographic record
Abstract
Purpose: To establish reference dosimetry techniques for accurate dose measurement of small and nonstandard fields and application to nonstandard field deliveries. Methods and Materials: A cylindrical PMMA phantom filled with water was constructed in the center of which reference absorbed dose to water was measured. Two candidate plan‐class specific reference (pcsr) fields for (i) linac‐based and (ii) TomoTherapy®‐based typical head and neck IMRT deliveries were created on the CT images of the phantom. The absorbed dose in each pcsr field normalized to that in a 10×10 cm2 was measured using four reference detectors: Gafchromic® EBT films a diamond detector and an in‐house developed guarded liquid ionization chamber (GLIC‐03) for the linac‐based IMRT delivery and a PTW microLion chamber for the TomoTherapy®‐based IMRT delivery. Based on the new dosimetry formalism pcsr correction factors kQpcsr,Qfpcsr,fref were determined for five air‐filled ionization chambers: Exradin A12 NE2571 Exradin A1SL Exradin A14 and PinPoint® 31006. The correction factor measurements were carried out in fully‐rotated and collapsed deliveries for the linac‐based IMRT delivery and only in a fully‐rotated delivery for the TomoTherapy®‐based IMRT delivery. Results: For the linac‐based IMRT delivery the evaluated overall uncertainty in measuring kQpcsr,Qfpcsr,fref was 0.3 %. The kQpcsr,Qfpcsr,fref is chamber independent within uncertainty (0.9955–0.9986) and systematically smaller than unity in the fully‐rotated delivery. In the collapsed delivery the correction factor was more dependent on the chamber type (0.9922–1.0048). For the TomoTherapy®‐based IMRT delivery kQpcsr,Qfpcsr,fref was above unity (1.0037–1.0076) with a 0.3 % measurement uncertainty. However the correction factor was different by 0.33 % between the Farmer‐type chambers and the smaller ionization chambers. Conclusions: The demonstrated dosimetry techniques carried out the relative dose measurements in the pcsr fields to within 0.3 % 1 uncertainty level. These dosimetry techniques will be helpful to improve dosimetric accuracy of other nonstandard field deliveries.
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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 | 0.003 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".