Measurements on the timing stability of the MicroPET R4 animal PET scanner
Why this work is in the frame
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Bibliographic record
Abstract
The MicroPET R4 and P4 small animal PET scanners have detectors consisting of an array of 64 2.1times2.1times10 LSO crystals coupled via light guides to Hamamatsu R5900-C12 position sensitive PMTs. These have energy resolutions in the range of 25% and timing resolutions <3 nsec. The calibration software allows users to set up the crystal identification maps and voltage to keV conversion gain for each crystal in a mostly automated and highly interactive way. However until recently there was no provision for making adjustments to the inter-detector timing alignment. Our preliminary evaluation of this instrument showed that reasonable normalization sinograms could only be obtained with a timing window of 10 nsec or more in spite of a timing resolution of <3 nsec. We performed sham transmission scans with nothing in the field of view, and a range of timing windows from 2 to 14 nsec and used a 14 nsec timing blank scan to generate effective attenuation sinograms as a function of timing window. These showed trues count-rates which fit well to a ERF(tau) function. However, the effective attenuation value, which should be 1.0, changes from block to block becomes very high (<3.5 at 6 nsec.) in some blocks suggesting the need for timing alignment. In the latest software release, V5.2.2.8, timing alignment is permitted, and the timing is much better aligned and much more stable
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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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 it