Sci‐Thur PM Therapy‐10: Is there an optimal starting gantry angle for equiangular‐spaced beam arrangements in IMRT?
Bibliographic record
Abstract
Equiangular‐spaced beam arrangements are the standard for intensity‐modulated radiotherapy (IMRT). However, since the choice of starting gantry angle is arbitrary, the question arises of whether there exist optimal starting gantry angles which will produce clinically significant improvements. To investigate the effect of beam orientation, the starting gantry angles in a 5‐beam equiangular‐spaced arrangement were incremented by 5°. Fifteen IMRT plans were generated per patient using 6 MV photon beams with static MLC delivery for 5 prostate, 5 lung, and 5 head‐and‐neck cancer patients. The plans were compared based on Planning Target Volume (PTV) and Organ‐at‐Risk (OAR) dose‐volume histograms, PTV mean dose, OAR maximum dose, total number of segments, and total number of monitor units. A fundamental geometric PTV conformity analysis was also conducted for each increment in gantry angle. To achieve this, divergent ray tracing was performed from the beam source coordinates through the PTV Beam's‐Eye‐View to produce a 3D cone beam matrix. The geometric conformity index (ratio of beam overlap volume to PTV volume) was then calculated. Clinically insignificant variations in PTV mean dose were found for all treatment sites as the starting gantry angles were incremented. This observation was further supported by the small variation in geometric conformity index with gantry increment. The variations in rectal V 75 Gy, spinal cord DVH, and parotid V 30 Gy were clinically significant for the prostate, lung, and head‐and‐neck patients, respectively. It is evident that the choice of starting gantry angle in IMRT equiangular‐spaced beam arrangements must be chosen with care.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".