Gradient-induced acoustic and magnetic field fluctuations in a 4T whole-body MR imager
Bibliographic record
Abstract
Both the acoustic and magnetic fluctuation frequency response functions for a Siemens AS25 body gradient coil inside a 4 Tesla whole-body MR system were measured and analyzed in this study. In an attempt to correlate the acoustic noise inside the gradient coil with magnetic field oscillations, triangular and trapezoidal gradient impulses of varying amplitudes and widths were used to excite the gradient coil. The acoustic and magnetic responses to these inputs were measured. The results show the existence of discrete resonances in both acoustic and uniform magnetic field fluctuation spectra, while gradient magnetic field fluctuation spectra show no such resonances. In addition, the dominant amplitude peaks in spectra fluctuate similarly with respect to trapezoidal gradient impulse flat-top widths. This implies that these phenomena are correlated, and that the trapezoidal impulse flat-top width may be used as a way to suppress both acoustic noise and uniform magnetic field oscillations.
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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 | 0.002 |
| 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) | 0.001 | 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".