Development of a water calorimetry-based standard for absorbed dose to water in HDR I192r brachytherapy
Bibliographic record
Abstract
PURPOSE: The aim of this article is to develop and evaluate a primary standard for HDR 192Ir brachytherapy based on 4 degrees C stagnant water calorimetry. METHODS: The absolute absorbed dose to water was directly measured for several different Nucletron microSelectron 192Ir sources of air kerma strength ranging between 21,000 and 38,000 U and for source-to-detector separations ranging between 25 and 70 mm. The COMSOL MULTIPHYSICS software was used to accurately calculate the heat transport in a detailed model geometry. Through a coupling of the "conduction and convection" module with the "Navier-Stokes incompressible fluid" module in the software, both the conductive and convective effects were modeled. RESULTS: A detailed uncertainty analysis resulted in an overall uncertainty in the absorbed dose of 1.90% (1 sigma). However, this includes a 1.5% uncertainty associated with a nonlinear predrift correction which can be substantially reduced if sufficient time is provided for the system to come to a new equilibrium in between successive calorimetric runs, an opportunity not available to the authors in their clinical setting due to time constraints on the machine. An average normalized dose rate of 361 +/- 7 microGy/(h U) at a source-to-detector separation of 55 mm was measured for the microSelectron 192Ir source based on water calorimetry. The measured absorbed dose per air kerma strength agreed to better than 0.8% (1 sigma) with independent ionization chamber and EBT-1 Gafchromic film reference dosimetry as well as with the currently accepted AAPM TG-43 protocol measurements. CONCLUSIONS: This work paves the way toward a primary absorbed dose to water standard in 192Ir brachytherapy.
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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) | 0.001 | 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 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".