Changes in Diffusion-Weighted Images During Transient Cerebral Hypoxia-Ischemia Correlate with Reductions in Extracellular Space using Electron microscopic and Impedance Techniques.
Bibliographic record
Abstract
2 Background: Experimental animal and clinical studies indicate that diffusion-weighted imaging detects early ischemic changes which are assumed to reflect reductions in extracellular space and cellular edema. In the present study, we investigate this directly by measuring intensity changes in diffusion-weighted images and alterations in extracellular space using electron microscopic and impedance techniques during and after transient cerebral hypoxia/ischemia in rats. Methods: The right carotid artery was isolated surgically (sham control) or occluded with subsequent exposure to 8% oxygen for 2 hours in 31 one-week old Wistar rats. Diffusion-weighted images were obtained prior to, during, at 1 or 24 hours post hypoxia/ischemia. Animals were decapitated after either the sham procedure, during hypoxia/ischemia or at 1 or 24 hours post hypoxia/ischemia. The rat brain was flash frozen and processed for electron microscopic quantitation of extracellular space immediately after imaging. Extracellular space was also assessed by recording impedance changes prior to, during and for 1 hour post hypoxia/ischemia. Results: Intensity on diffusion-weighted images increased 78% ipsilaterally during hypoxia/ischemia, substantially recovered at 1 hour post hypoxia/ischemia, and increased 49% again at 24 hours post hypoxia/ischemia. Stereologic analysis of extracellular space from electron micrographs of the cortex in controls was 51 ± 6% of total space. This decreased to 3 ± 1% during hypoxia/ischemia, returned to 30 ± 21% at 1 hour post hypoxia/ischemia and was 43 ± 7% at 24 hours post hypoxia/ischemia. Impedance measurements within the ischemic cortex demonstrated that extracellular space decreased 40% during hypoxia/ischemia and recovered to control levels at 1 hour post hypoxia/ischemia. Conclusions: Increased intensity on diffusion-weighted images corresponds well to a reduction in extracellular space.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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".