Electron beam reference dosimetry measurements obtained at multiple institutions using the Addendum to AAPM's TG‐51 protocol
Bibliographic record
Abstract
Abstract Background The TG‐51 protocol describes methods for obtaining reference dosimetry measurements for external photon and electron beams. Since the publication of TG‐51 in 1999, research on reference dosimetry has allowed revisiting the procedures and data recommended in the protocol. An Addendum to TG‐51 for electron beam reference dosimetry was published in 2024, which revises the formalism and procedures and provides updated data. Purpose To compare clinical reference dosimetry measurements in electron beams obtained using the original American Association of Physicists in Medicine's (AAPM) TG‐51 protocol and its associated Addendum (AAPM WGTG51 report 385). Methods Measurements were performed in electron beams using the data and methods prescribed by TG‐51 and its Addendum. Nine participants (eight clinics and one primary standards laboratory) provided data and measurements. Results were obtained with 18 linacs using 87 total beam energies (4–6 energies per linac) between 4–22 MeV, representing the range of electron beam energies used clinically. Various cylindrical (6 types) and parallel‐plate (4 types) ionization chamber types were employed, representing most of the chambers commonly used in modern radiation therapy clinics. An analysis was performed to determine if differences arise from the new data recommended for beam quality conversion factors or from changes to the procedure. Results Results for dose to water per monitor unit obtained using the Addendum are up to 2.3% higher in low‐energy beams and 1.3% higher in high‐energy beams compared to results obtained using the original TG‐51 protocol. These differences are consistent with what was predicted by the Addendum. Differences arise from both the changes to procedure (up to 0.7% from not requiring the correction for cylindrical chambers, 0.5% from the change in the shift of the point of measurement for parallel‐plate chambers) as well as the recommended data (0.8% from differences in , 0.5% from differences in ). Conclusion This work elucidates where differences arise in results obtained using the original TG‐51 protocol and its associated Addendum for electron beam reference dosimetry. The results presented here provide confidence in the new approach and data recommended by the Addendum. Clinical physicists can use these results to ensure that differences are as expected when implementing the Addendum.
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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 | 0.018 | 0.021 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.021 | 0.007 |
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".