SU-D-105-03: Developing QA Procedures for Gated VMAT SABR Treatments
Bibliographic record
Abstract
Purpose: To develop a QA procedure for gated VMAT SABR liver cancer treatments and investigate the gating parameters for acceptable plan delivery in terms of the dose to a moving volume and treatment delivery time. Methods: 10 patient plans for VMAT SABR liver were created using the Eclipse™ TPS. The verification plans were then transferred to a CT-scanned Quasar™ phantom and delivered on a TrueBeam™ linac using a 10FFF beam and Varian's RPM system for respiratory gating. Two kinds of breathing patterns were used: free breathing (FB) and an interrupted (∼5s pause) end of exhale coached breathing (CB) pattern. Ion chamber and Gafchromic™ film measurements were acquired for a gated delivery while the phantom moved under the described breathing patterns and a non-gated, stationary phantom delivery. The gate window was set to obtain a range of residual target motion from 2–10 mm. Results: Preliminary chamber measurements indicate that the dose to the center of the PTV can vary considerably under gated delivery compared to the static case. The effect can be significant for free breathing; ∼4–12% over the selected range of residual target motion. The agreement was more consistent with CB pattern at ∼1–4%. Gamma analysis (3%, 3mm) showed an agreement above 99.74% for all gated deliveries compared to the static delivery. The treatment time with a gate width of 2 mm was ∼265s for the CB pattern compared to ∼740s under a typical FB pattern. A non-gated delivery of the same plan took ∼100s. Conclusion: Gated VMAT treatments have been delivered successfully to a motorized phantom. FB patterns contain considerable variability and it is difficult to achieve acceptable results even with very small gate windows. However, a CB pattern combined with a sufficiently small gate, resulted in acceptable dose distributions that can be delivered in a reasonable amount of time. Francis Viel received funding from the Natural Sciences and Engineering Research Council of Canada. This work has been supported by the Varian Research Collaborations Program.
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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 | 0.003 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.003 |
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".