WE‐A‐BRB‐07: Characterization and Use of a 2D‐Array of Ion Chambers for Brachytherapy Dosimetric Quality Assurance
Bibliographic record
Abstract
Purpose: The 2D ionization chamber array MatriXX Evolution is one of the 2D ionization chamber arrays developed for megavoltage real‐time absolute 2D dosimetry and verification of IMRT. The purpose of this study is to evaluate the performance of ion chamber array for sub‐megavoltage range brachytherapy beam dose verification and quality assurance. Methods: The dose linearity and energy dependence of the 2D ion chamber array was studied using kilovoltage X‐ray beams (100 to 300 kVp). For the Ir‐192 brachytherapy HDR source dosimetric evaluation the detector response (kuser) factor was determined using 300 kVp beam. The phantom used for this measurement consists of multiple catheters, the IBA MatriXX detector and a slab of RW3 to provide full scattering conditions. The treatment planning system dose distribution was calculated on the CT scan of this phantom. The measured and TPS calculated distributions were compared in IBA Dosimetry OmniPro‐IˈmRT software. The quality of agreement was quantified by the gamma index for nine sets of plans. Using a dedicated phantom capable of receiving 5 brachytherapy intralumenal catheters a QA procedure was developed for end‐to‐end dosimetric evaluation for routine quality assurance checks. Results: The 2D ion chamber array dose dependence was found to be linear for 100 to 300 kVp and kuser showed strong energy dependence for 100 to 300 kVp energy ranges. The maximum mean difference between ion chamber array measured and TPS calculated was 3.7%. Comparisons of dose distribution for different test patterns have shown agreement with greater than 94.5 % for γ ≤ 1 (with 3% delta dose and distance criterion of 2 mm). Dosimetric QA can be performed with the 2D ion chamber array. Conclusions: The MatriXX Evolution ionization chamber array has been found to be reliable for measurement of both absolute dose and relative dose distributions for the Ir‐192 brachytherapy HDR source.
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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 | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".