IC‐P‐125: Altered macromolecule signal in the hippocampus in Alzheimer patients measured by 1H magnetic resonance spectroscopy
Bibliographic record
Abstract
Short echo-time 1H magnetic resonance spectroscopy is commonly used to measure metabolite levels in the human brain. Suppression of metabolite signals by inversion-nulling methods may be used to measure the contribution of broader macromolecule resonances. The hippocampus is known to be involved early in the pathophysiology of Alzheimer disease. Objective: The purpose of this study was to compare the macromolecule content in the hippocampus in subjects with Alzheimer disease (AD) and mild cognitive impairment (MCI) to normal elderly controls (NEC). Short echo-time 1H spectra were acquired from the right hippocampus of 23 subjects with probably AD (mean ± standard deviation; age 74 ± 7 years; MMSE 23 ± 4), 12 subjects with MCI (age 72 ± 10 years; MMSE 28 ± 2), and 15 NEC (age 78 ± 6 years; MMSE 29 ± 1) using a 4 Tesla MRI. Spectra were localized by adiabatic selective refocusing (LASER, TE/TR = 46/4200 ms, 128 averages) preceded by two inversion pulses (TI1 = 2.2s, TI2 = 0.7s) for metabolite nulling. Voxel dimensions were chosen to maximize voxel volume while staying largely within the hippocampus of each subject and ranged from 1.8 cc to 5.1 cc (mean ± SD, 3.7 ± 0.8 cc). Spectra were line shape corrected using an unsuppressed water spectrum (8 averages, TR = 2.2s) and summed for each diagnostic group following amplitude normalization. The average group spectra were subtracted to reveal group differences. Macromolecule spectra were successfully scaled and summed. The difference between the average macromolecule spectra from the Alzheimer patients and NEC subjects showed notable peaks at 4.0 ppm (increased in AD), 1.87 ppm (decreased in AD), and 1.57 ppm (decreased in AD). Differences between the average AD spectrum and average MCI spectrum were less remarkable. The macromolecule baseline in short echo-time 1H spectra is normally not carefully scrutinized. This preliminary study shows potential differences between macromolecule signals in AD subjects compared to normal elderly controls in the right hippocampus. Further study is required to identify the biological significance of these resonances.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| 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".