Poster — Wed Eve—11: Pinhole Image Characterization of X‐Ray Tube Focal Spots using Storage Phosphor Imaging Technology
Bibliographic record
Abstract
The x‐ray tube focal spot is a key determinant of the resolution of an imaging system. Although system resolution can be assessed using bar pattern test objects, a pinhole image provides the point‐spread function due to the focal spot and complete information on the radiation source distribution. The NEMA standard protocol specifies no‐screen film for pinhole imaging, but in the digital age this is problematic. We investigated use of a medium‐resolution storage phosphor imaging system, similar to a hospital CR system. An x‐ray tube with 15° target angle and nominal 1.0 and 2.0 mm focal spots was assessed using a 0.075 mm diameter commercial pinhole and a storage phosphor system. The screen resolves nearly . Its blur of about 0.2 mm is comparable to the pinhole aperture size projected onto the image receptor by the radiographic magnification, , used. A simple expression is obtained which corrects a distance measured in the digital image of the focal spot for both pinhole blur and screen blur to yield the true focal spot dimension. For the x‐ray tube assessed, focal spot size was independent of current, and decreased very slightly with increased potential. A second tube, mounted for research purposes to foreshorten the focal spot to an effective angle of 2.2°, was also assessed. In both tubes, the two focal spots superimposed but were not centered on each other. A medium‐resolution storage phosphor imaging system can adequately replace no‐screen film in pinhole imaging and is much more convenient.
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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 | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.022 | 0.003 |
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".