Cobalt radiation therapy treatments with opposed plain fields and beam flattening filter
Bibliographic record
Abstract
Low LET radiations such as cobalt (1.25 MeV) and 6 MV linac megavoltage gamma/x radiations continue to be a basic facility in a busy radiation therapy department. When the beam profiles in water are carefully scrutinized, linac beams have flattened isodose curves compared to slightly rounded curves in Co-60 beams at all depths. It was speculated that to overcome slight non-uniformity in the edges, as well as slight variations inside the planning target volume (PTV), a beam flattening filter may be preferable to be used along with plain radiotherapy fields. A pilot study of clinical use of beam flattener in cobalt beam is reported. A flattening filter (FF) was locally made out of dental wax, for 20 x 20cm field, in the 780E Telecobalt machine (M/s MDS Nordian, Canada). Beam profiles with and without FF were measured using water phantom, to confirm the filter efficiency. Both manual and Radiation Field (RFA) methods in water phantom confirmed efficacy of wax filter. This flattened beam was used in the treatments of Uterine Cervix and Oesophagus cancers, (25 patients each) with a measured filter transmission factor 0.805 in treatment plans. All the patients completed the prescribed dose of 50Gy in 25 fractions for Ca Cervix and 50Gy/25 fractions or 50.4Gy/28 fractions for Ca Oesophagus; at 5 fractions/ week treatment regimens. Case records of these patients retrospectively verified did not reveal any untoward associated morbidity on routine clinical follow ups during treatment or immediate follow up. As multi-leaf collimated cobalt beam also has built in rounded beam profiles, outcome of this work implemented in clinical applications add to new research knowledge. As cervix, head and neck, oesophagus malignancies form significant percentage of radiation oncology treatments, results of this present work will benefit many conventional treatments. It is strongly recommended that the clinical efficacy of FF Cobalt treatments be investigated in a controlled clinical trial, by random allotments with FF plain fields, with output corrections.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 0.002 |
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".