SU‐E‐T‐12: Radiation Detector Responses to Applied Homogeneous Transverse and Parallel Magnetic Fields
Bibliographic record
Abstract
PURPOSE: To determine the relative dose response of a diamond detector and a ion chamber in a clinical photon beam within uniform magnetic fields, endeavoring to evaluate and refine reference dosimetry techniques for use in integrated MR-linac systems. METHODS: The Monte Carlo code PENELOPE was used to model the structure and materials of the PTW60003 diamond detector and PR06 ion chamber in a 6MV beam in the presence of a homogeneous magnetic field. The magnetic field strength was varied from 0 to 1.5T, and both the parallel and transverse magnetic field orientations with respect to the beam central axis were simulated. The long axes of the detectors were oriented both perpendicular and parallel to the radiation beam direction for each magnetic field orientation. All simulations determined the detectors' signal in air. A small electromagnet was used to experimentally determine the detectors' response in transverse magnetic fields up to 0.2T to validate the simulations. RESULTS: The simulated response of both detectors matched to the experimental data within the estimation error. The relative response of PR06 and diamond detector varied up to ±8.5% (depending on chamber orientation) and >9% respectively with increasing transverse magnetic field strength. In contrast, both detectors were found to be relatively insensitive to the increasing magnetic fields irrespective of the detector orientation in parallel magnetic field. A maximum change of 2% in PR06 response was observed at 1.5T parallel magnetic field and in the parallel orientation of chamber. CONCLUSION: This work has significant impact on dosimetry protocols for integrated MR-linac systems, where detector response may be altered by the presence of a magnetic field. The need for a magnetic field dependent correction factor is strongly indicated for the transverse magnetic field cases, while such changes in detector response can be largely ignored in parallel magnetic fields < 1T. CIHR (Canadian Institutes of Health Research) - funding support Faculty of Medicine and Dentistry, University of Alberta - funding support.
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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 | 0.001 |
| 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".