Po‐Thur Eve General‐14: 3rd Generation Co‐60 based Megavoltage Computed Tomography
Bibliographic record
Abstract
Patient set up verification is a necessary step for high precision radiation therapy. There has been considerable work to develop such verification using megavoltage (MV) imaging on Electronic Portal Imaging Devices (EPIDs). Recently, MV image guidance has been advanced with the extension to MV computed tomography (MVCT). At the CCSEO we have been investigating MVCT with a Cobalt‐60 unit, in the context of developing Cobalt‐60 tomotherapy. The system is comprised of an automated rotary stage added to a Theratronics T780C Co‐60 unit; recently our imaging has advanced with the development of a 3rd generation imaging system using a Varian PortalVision LC250 EPID. The EPID was calibrated for relative dose‐response using a parallel‐plate ion chamber; the calibration curve follows a quadratic form. The image reconstruction is based on a generalized Feldkamp technique; executed in MATLAB. Consistent with previous 1st generation studies, results on various phantoms show that Co‐60 based EPID — MVCT is free from beam hardening and metallic artifacts. Phantoms included a variety of orthopaedic hip implants, Rando head phantom with stainless steel and tungsten inserts, and a plug phantom containing materials of known atomic number. EPID determined MVCT numbers also correspond linearly with relative electron density. The work will summarize the differences between kVp and MV CT images, while highlighting the improvements of EPID based imaging over 1st generation Cobalt MVCT.
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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 | 0.001 | 0.001 |
| 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) | 0.033 | 0.015 |
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".