Sci‐AM Fri ‐ 05: Shielding design for a PET‐CT simulator in a radiotherapy department
Bibliographic record
Abstract
Purpose: To design the shielding for a PET‐CT simulator in a radiation therapy department, and to verify the adequacy of shielding during acceptance testing. Method and Materials: A Discovery ST (GE Healthcare, Milwaukee, USA) PET‐CT scanner replaced a CT‐Simulator in our centre. Existing space was reconfigured to include a patient rest area for FDG uptake and a hot lab. Adjacent areas included a simulator control room, patient waiting rooms, and corridors; floors above and below contained offices and linac bunkers and control rooms. Patients were modeled as point sources; attenuation by concrete walls and lead shielding explicitly included build‐up. Design limits were set to 1 mSv per year for nuclear energy workers (NEWs), and 0.05 mSv per year for non‐NEWs. A linear 1.5‐GBq source of in scattering material was used to verify the adequacy of the shielding. Results: The control room was shielded with 6.35 mm of Pb. Two sheets of lead glass (48% Pb by weight) totaling 14 mm provided sufficient attenuation for a window. The patient uptake area and the scanner room were shielded with 4.7 mm of Pb on walls adjacent to corridors. No shielding was required on the floor and ceiling. Measurement showed that design goals were met. Conclusion: Strategic location of patients, NEWs, and low‐occupancy areas simplified design to these stringent limits. Careful consideration of workloads and occupancy factors are needed to meet the design criteria, particularly when older facilities are being redesigned. Design to such low limits unnecessarily increases construction cost.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".