Abstract T MP4: Quality of CT Perfusion Imaging Thresholds for Infarct and Penumbra in the Acute Ischemic Stroke Setting: An Updated Systematic Review
Bibliographic record
Abstract
Background: CT Perfusion (CTP) may inform treatment decisions in acute ischemic stroke (AIS). We sought to determine extent of variability with CTP thresholds for infarct core and penumbra and reasons for such variability using an up-to-date systematic review. Methods: Search strategy combined the themes of AIS, perfusion imaging, and CT/MRI. Two independent reviewers screened at all levels; disagreements were settled through consensus. Inclusion criteria were CTP within 24hrs of stroke onset and reported perfusion thresholds for infarct core, penumbra, and/or normal/not at risk tissue for mixed grey/white matter. Study demographics, QUADAS assessment of quality, and mean thresholds of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), relative CBV (rCBV), relative CBF (rCBF), and relative MTT (rMTT) were collected. Thresholds were reported as median mean threshold (interquartile range). Results: The search resulted in a total of 11919 abstracts from EMBASE and MEDLINE. Of these, 711 studies were identified for full-text review, 134 met all eligibility criteria. 29 studies provided thresholds for CTP and were included in the review. For CBF, median mean threshold was 8.64 (7.94-13.92) ml/min/100g for core, 19.1 (17.1-31.9) ml/min/100g for penumbra and 47.4 (35.6-59.1) ml/min/100g for normal/not at risk tissue. For CBV, median mean threshold was 1.0 (0.68-1.88) ml/100g for core, 2.45 (2.0-3.0) ml/100g for penumbra, and 2.65 (2.0-3.3) ml/100g for normal/not at risk tissue. For MTT median mean threshold was 15.6 (15.3-17.7) seconds for core, 10.5 (7.1-46.2) seconds for penumbra, and 3.9 (3.65-4.15) seconds for normal/not at risk tissue. Median mean threshold for rCBF was 29% (22.5%-35.5%) for core. Sufficient TTP and Tmax data were not reported. Overall, quality was highly variable according QUADAS ranging from 20.7% to 93.1% across the 14 variables. Conclusions: Due to heterogeneity of vendor CTP algorithms, follow-up imaging to define infarct core (NCCT, DWI), unknown recanalization times/reperfusion status and differing onset to CT times, CTP thresholds for infarct core and penumbra are highly variable. As such, a single best threshold for core could not be derived from literature.
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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 | 0.017 | 0.076 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.012 | 0.010 |
| Bibliometrics | 0.021 | 0.018 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.005 | 0.005 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.003 | 0.001 |
| Insufficient payload (model declined to judge) | 0.009 | 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".