TH-C-201B-05: Equivalent Doses and Secondary Malignancy Risk Estimates for Gynecological Patients Undergoing CBCT and IMRT
Bibliographic record
Abstract
Purpose: To assess risk of secondary malignancy associated with peripheral doses from kV CBCT for gynecological patients undergoing IMRT and to compare doses to organs peripheral to the treated volume from kV Cone Beam with scatter and leakage doses from MV IMRT. Method and Materials: In field and peripheral doses for kV CBCT gynecologic studies were simulated by Monte Carlo code BEAMnrc and DOSXYZnrc. Dose-mean lineal energy based quality factor for kV beam was calculated to account for the difference of relative biological effectiveness between kV CBCT beams and MV beams. Life time attributable risk of cancer incidence (LAR) and relative risk (RR) for bladder and colon for patients undergoing IMRT and daily CBCT were estimated based on the Monte Carlo simulated equivalent doses. Peripheral dose from image-guided radiation therapy (IGRT) using kV CBCT was evaluated relative to the scatter and leakage doses from the Linac delivering the IMRT treatment. Results: The estimated quality factor for CBCT is about 1.3 times that of MV beams. With daily imaging over a 25 fraction IMRT treatment regimen with prescribed dose of 4500 cGy RRs of cancer incidence for bladder and colon are 21.2 and 3.4 of which the contribution from CBCT is 1.83 and 1.20. In the peripheral region the average CBCT dose is of the same order of magnitude as the leakage dose. Scatter doses from the IMRT treatment are however a factor of 5 higher than the CBCT peripheral doses and leakage doses. Conclusion: Even with daily kV CBCT the relative risk caused by CBCT is much lower than the risk from IMRT scattering in both in field and peripheral regions. Understanding the relative risks associated with the doses from these procedures is important for designing appropriate CBCT protocols. Conflict of Interest: Research supported by Varian Medical Systems.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".