Oblique incidence effects in direct x‐ray detectors: A first‐order approximation using a physics‐based analytical model
Bibliographic record
Abstract
PURPOSE: The authors describe the modifications to a previously developed analytical model of indirect CsI:Tl-based detector response required for studying oblique x-ray incidence effects in direct semiconductor-based detectors. This first-order approximation analysis allows the authors to describe the associated degradation in resolution in direct detectors and compare the predictions to the published data for indirect detectors. METHODS: The proposed model is based on a physics-based analytical description developed by Freed et al. ["A fast, angle-dependent, analytical model of CsI detector response for optimization of 3D x-ray breast imaging systems," Med. Phys. 37(6), 2593-2605 (2010)] that describes detector response functions for indirect detectors and oblique incident x rays. The model, modified in this work to address direct detector response, describes the dependence of the response with x-ray energy, thickness of the transducer layer, and the depth-dependent blur and collection efficiency. RESULTS: The authors report the detector response functions for indirect and direct detector models for typical thicknesses utilized in clinical systems for full-field digital mammography (150 microm for indirect CsI:Tl and 200 microm for a-Se direct detectors). The results suggest that the oblique incidence effect in a semiconductor detector differs from that in indirect detectors in two ways: The direct detector model produces a sharper overall PRF compared to the response corresponding to the indirect detector model for normal x-ray incidence and a larger relative increase in blur along the x-ray incidence direction compared to that found in indirect detectors with respect to the response at normal incidence angles. CONCLUSIONS: Compared to the effect seen in indirect detectors, the direct detector model exhibits a sharper response at normal x-ray incidence and a larger relative increase in blur along the x-ray incidence direction with respect to the blur in the orthogonal direction. The results suggest that the oblique incidence effect in direct detectors can be considered to be caused mostly by the geometry of the path where the x-ray beam and its secondary particles deposit energy in the semiconductor layer.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".