P-003 Hypoattentuation on CTA Images Evaluated for Potential Acute Stroke Thrombectomy: How Timing Affects Conspicuity
Bibliographic record
Abstract
Introduction CTA is used to triage acute stroke patients for potential thrombectomy. Single, multiphase1 or dynamic2 CTA may demonstrate areas of parenchymal hypoattenuation on source images(CTASI). These areas may represent either delayed arrival of contrast or could be ischemic/infarcted tissue. The area can be variable depending on the arrival of contrast on the time-tissue attenuation curve (TAC). Areas of hypoattenuation distal to an occlusion are perceived because of differences in contrast compared to normally-perfused areas and can be objectively measured. Patients with significant hypoattenuation may be potentially excluded from thrombectomy. We evaluated conspicuity of hypoattenuation on dynamic multiphase CTASI. Specifically, we sought to determine if there is a specific time point on the TAC curve which optimizes conspicuity. Materials and methods We retrospectively identified 45 consecutive large vessel strokes between 2012–14 who had dynamic CTA and CTP. We identified ischemic areas from areas of low CBV. An ROI was drawn on the corresponding CTASI and in normally-perfused tissue. We evaluated CTASI in 7/18 points along the TAC (Figure 1). We calculated absolute and relative change in attenuation between potentially ischemic and normally-perfused tissue. Differences in conspicuity were evaluated using a Friedman test with Bonferroni correction. Results There were 22 males/23 females, age 69, ±16, median NIHSS 10.6. All occlusions were in the anterior circulation; 64% on the left. There was a significant effect of phase on the TAC for both absolute and relative conspicuity of ischemic (Figure 2) vs normally-perfused areas (P < 0.00001). The median absolute and relative conspicuity of ischemic:normally-perfused tissue was greatest at the peak arterial (8.6 HU, 1.15), notch (9.4 HU, 1.17) and peak venous phases (7 HU, 1.13) vs other portions of the TAC (2.5–3.3 HU, 1.04–1.09). Conclusion The conspicuity of ischemic areas distal to a large artery occlusion in acute stroke is dependent on the phase of contrast arrival on time-resolved dynamic CTASI. The greatest conspicuity of areas of hypoattenuation between ischemic and normally perfused tissue is in the middle of the TAC. References 1 Radiology 2015 May;275(2):510–20. 2 Stroke 2014 Sep;45(9):2683–28. Disclosures C. Lum: None. P. Dave: None. R. Thornhill: None. S. Chakraborty: None. D. Dowlatshahi: None.
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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 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| 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) | 0.002 | 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".