Sci—Wed PM: Delivery—07: Dosimetric Characterization of a New Pixel Ionization Chamber Array
Bibliographic record
Abstract
A new ionization chamber array developed by IBA Dosimetry (Germany) is evaluated at our centre. The dosimetric characteristics of this device such as dose and dose rate dependence, stability, energy dependence, profiles and error detection ability were studied. COMPASS is an array with 1600 parallel plate ion chambers. Each chamber is 3.8 mm in diameter and 2mm in height spaced 6.5 mm apart. The array is mounted onto the wedge slot of the Varian Clinac 2100iX (Varian Medical Systems, Palo Alto, CA) linear accelerator. Linearity of the detector with dose and response to dose rate were done using Clinac 2100iX 6 MV beam. The detector showed excellent linearity response with dose and a variation of <0.2% with dose rates. Short term and long term reproducibility results showed a standard deviation of 0.05%. Energy dependence of COMPASS was evaluated by response of the device to beam energies ranging from to 18 MV X‐rays. , determined by COMPASS increases with energy as opposed to a decreased response with energy of a thimble ion chamber. Profiles measured with COMPASS were similar to Markus (plane parallel) ion chamber for field sizes . The chamber array showed increased dose response off‐axis for larger fields. The penumbra measured by COMPASS was 3.14± 0.03 mm vs. 1.25± 0.02 mm for film measurements for a range of field sizes. A leaf gap error of 1 mm was detected by the device using an IMRT test field. Research partially sponsored by IBA Dosimetry.
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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) | 0.000 | 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 | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".