Temporal wavelet denoising of PET sinograms and images
Bibliographic record
Abstract
The level of noise in PET dynamic studies makes it difficult to provide accurate and robust kinetic parameters from time activity curves, particularly at the voxel level. Several approaches have been followed to lower noise: denoising reconstructed images with spatial wavelets, adding a priori information during reconstruction about the signal without noise, including the temporal dimension during reconstruction. In this work, we propose to use a temporal wavelet denoising approach, based on the characteristics of PET time activity curves in sinograms (or reconstructed images). This approach has recently been proposed in image processing and relies on discriminating signal from noise by including relevant “a priori” information (on the statistical distribution of the wavelet coefficient for a whole sinogram or reconstructed image), as well as appropriate noise formation model in the time domain. This approach is tested in a 2D spatial + 1D time Monte Carlo simulation mimicking brain, and compared with a standard denoising approach : SUREShrink. Preliminary results indicate that better performances are obtained for sinogram denoising with the proposed approach compared with SUREShrink, and that the resulting sinograms can be reconstructed with a weighted least-squares (WLS) algorithm for all techniques. Denoising in the reconstructed images with this approach was also investigated.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 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".