An inductive method to measure mechanical excitation spectra for MRI elastography
Bibliographic record
Abstract
Abstract Harmonic MR elastography (MRE) monitors the propagation of acoustic waves in tissues in the audio regime. Oscillatory motions with large amplitudes can induce nonlinear wave propagation effects resulting in harmonics that evolve over space. In order to understand these effects, knowledge of the motions of applied mechanical motion is needed to rule out the presence of harmonic motion arising from the mechanical source. We propose a simple technique to measure the spectral content of mechanical excitation based on the use of a set of detection coils mounted on the elastography excitation system. The motion of these coils causes a small signal to be induced from the applied static magnetic field of the MRI system. A detailed analysis shows that quantitative assessment of excitations is possible with correct geometrical arrangement of the detector coils. However, it shows that nonlinear effects can also occur depending on the alignment of the detection coils with respect to Bo. The system is easy to operate and allows for the time resolved observation of the actuator motion for each experimental setup. The system is intended to be used before and after MRE experiments to determine excitation spectral content and repeatability. We demonstrate its use in a one‐dimensional elastography experiment and show that this information is an essential prerequisite for studying material nonlinear elastic properties using MRE. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 21B: 32–39, 2004
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".