Evaluation of Intra- and Inter-fraction Motion in Breast Radiotherapy Using Electronic Portal Cine Imaging
Bibliographic record
Abstract
Breast irradiation is one of the most challenging problems in radiotherapy due to the complex shape of the target volume, proximity of radiation sensitive normal structures and breathing motion. It was the aim of the present study to use electronic portal imaging (EPI) during treatment to determine intra- and inter-fraction motion in patients undergoing radiotherapy and to correlate the magnitude of motion with patient specific parameters. EPI cine images were acquired from the medial tangential fields of twenty radiotherapy patients on a minimum of 5 days each over the course of their treatment. The treatments were administered using 10 MV X-rays and dynamic wedges on a Varian Clinac 2100CD linear accelerator. Depending on the incident dose and the angle of the wedge, between 4 and 16 images could be acquired in one session using an EPI device based on liquid ionization chambers (Varian). The border between lung and chest-wall could be easily detected in all images and quantitative measurements were taken for the amount of lung in the field and the distance of the breast tissue from the field edges. Inter-fraction variability was found to be about twice as large as intra-fraction variability. The largest variability was detected in cranio/caudal direction (intra-fraction: 1.3 +/- 0.4 mm; inter-fraction: 2.6 +/- 1.3 mm) while the lung involvement varied by 1.1 +/- 0.2 mm and 1.8 +/- 0.6 mm intra- and inter-fraction, respectively. This indicates that the effect of breathing motion on the amount of radiated lung was not of major concern in the patients studied. Of other patient specific parameters such as body weight, breast separation, field size and location of the target, only increasing age was significantly correlated with larger inter-fraction motion. Acquisition of EPI cine loops proved to be a quick and easy technique to establish the amount of patient movement during breast radiotherapy. The relatively small variability found in the present pilot study justifies considerations for more conformal dose delivery.
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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 | 0.003 |
| 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) | 0.000 | 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 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".