Investigation of three radiation detectors for accurate measurement of absorbed dose in nonstandard fields
Bibliographic record
Abstract
PURPOSE: To establish accurate experimental dosimetry techniques for reference dose measurements in nonstandard composite fields. METHODS: A cylindrical PMMA phantom filled with water was constructed, at the center of which reference absorbed dose to water for a head and neck IMRT delivery was measured. Based on the proposed new formalism for reference dosimetry of nonstandard fields [Alfonso et al., Med. Phys. 35, 5179-5186 (2008)], a candidate plan-class specific reference (pcsr) field for a typical head and neck IMRT delivery was created on the CT images of the phantom. The absorbed dose to water in the pcsr field normalized to that in a reference 10 x 10 cm2 field was measured using three radiation detectors: Gafchromic EBT films, a diamond detector, and a guarded liquid-filled ionization chamber developed in-house (GLIC-03). Pcsr correction factors [formula in text] were determined for five different types of air-filled ionization chambers (Exradin A12, NE-2571, Exradin A1SL, Exradin A14, and PinPoint 31006) in a fully rotated delivery and in a delivery with the same MLC settings and weights but from a single gantry angle (a collapsed delivery). RESULTS: The combined standard uncertainty in measuring the correction factor [formula in text] using the three dosimetry techniques was 0.3%. For all the air-filled ionization chambers and the pcsr field tested, the correction factor was not different from unity by more than +/- 0.8%. For the fully rotated delivery, the correction factors were in a narrow range of 0.9955-0.9986, while in the collapsed delivery, they were in a slightly broader range of 0.9922-1.0048. In the collapsed delivery, the Farmer-type chambers (Exradin A12 and NE2571) had very similar correction factors (0.9922 and 0.9931, respectively), whereas the correction factors for the smaller chambers showed more distinct chamber-type dependence. CONCLUSIONS: The authors have established three experimental dosimetry techniques that allow reference measurements of nonstandard field correction factors [formula in text] for air-filled ionization chambers at the 0.3% 1sigma uncertainty level. These techniques can be used to determine criteria for the selection of plan-class specific reference fields and ultimately improve clinical reference dosimetry of nonstandard fields.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".