TH‐D‐L100J‐07: Practical Implications of Cone‐Beam Artifact On Edge Resolution
Bibliographic record
Abstract
Purpose: Cone‐beam CT utilizing circular trajectories fails to collect sufficient information to satisfy the inverse Radon problem. The lack of information has been characterized as a shift‐variant cone of missing frequency that scales with distance from the source trajectory plane. This cone has been previously demonstrated in localized, simple geometrical objects (spheres and disks). The aim of this study was to verify the cone in larger, clinically relevant objects and examine the relative impact of the resulting artifact on edge resolution. Methods: An excised rabbit spine with ribs and soft tissue was imaged at varying distances with respect to the source plane. Reconstructions were made using a modified Feldkamp filtered backprojection algorithm and were registered and compared for consistency. Inconsistent regions were examined with respect to surface orientation and planar extent. In addition, a section of human vertebra was similarly imaged. 3D Fourier Transforms of the vertebra were examined and regions of lacking frequency information were compared with theory. Results: In both specimens, large planar surfaces oriented such that their dominant frequencies lied within the expected null cone degraded most notably with increased distance from the source plane. In particular, upper and lower surface resolution of the rabbit vertebrae were most affected and associated with increased streaks. In contrast, cellular regions of trabecular bone, as well as bony and soft tissue with surfaces of varying orientation showed largely consistent reconstruction regardless of vertical placement. Finally, the conical region of missing frequency power predicted by theory was clearly identified in the Fourier Transforms of the human vertebra. Conclusions: Results support that cone‐beam artifact associated with circular trajectories preferentially affects a small well‐defined subset of surface orientations. In practice, cone‐beam CT using circular trajectories is expected to be largely edge preserving, since surfaces that belong to this subset are limited in extent.
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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 | 0.005 | 0.008 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".