Real-time PET image reconstruction based on regularized pseudo-inverse of the system matrix
Bibliographic record
Abstract
The feasibility of tomographic image reconstruction by projection data filtering based on the singular value decomposition of the system matrix has recently been demonstrated in high-resolution animal positron emission tomography (PET). A regularization methodology involving truncation of the singular value spectrum based on the systematic spatial resolution analysis has been proposed and successfully applied. In the present paper, we show how realtime image reconstruction can be achieved using the regularized pseudo-inverse of the system matrix. An update of the current image estimate can be obtained using one column of the regularized pseudo-inverse matrix to account for the next registered event, thus allowing, in principle, for instant visualization of the radioactivity distribution while the object is still being scanned. Computed estimates converge to the minimum-norm least-squares solution of the regularized inverse problem when sufficient total counts are acquired to fulfill the assumption of the normal data error distribution. The computing expenses for image updating to account for the next registered event depend only on the total number of pixels in the discrete image representation. Data storage requirements are discussed. Limited angle tomography and non-traditional detection geometry may be handled using the described image reconstruction approach as well. The proposed method was tested with the list-mode PET data.
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How this classification was reachedexpand
Direct model labels (unvalidated)
Per-model category and study-design labels from the labeling rounds. They are machine output, unvalidated, and the disagreement between models ships as data. No study design here is MEDLINE-validated yet.
| Model arm | Categories | Study design | Confidence |
|---|---|---|---|
| gemma | no category Domain: not available · Genre: Methods About the Canadian research system: no · About a Canadian topic: no | Simulation or modeling | low |
| gpt | no category Domain: not available · Genre: Empirical About the Canadian research system: no · About a Canadian topic: no | Bench or experimental | low |
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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| 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 | 0.001 |
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, unvalidatedLabeled directly by 2 models reading the full record.
The models disagree on parts of this classification; every voice is preserved in the section at the end of the page.
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".