Non-linear scattering from microbubble contrast agents in the 14-40 MHz range
Bibliographic record
Abstract
The non-linear scattering properties of microbubble contrast agents in the 14-40 MHz frequency range are investigated. Experiments were conducted as a function of pressure for two agents (Definity/sup TM/ and Optison/sup TM/) and polystyrene microbeads as control scatterers. For Definity/sup TM/, subharmonic (0.5f/sub 0/) and ultraharmonic (1.5f/sub 0/) scattering was substantial and strongly dependent on pressure up to 26 MHz. Optison/sup TM/ also exhibited sub- and ultraharmonic scattering, but these effects were weaker and found to persist up to 22 MHz. Second harmonic (2f/sub 0/) scattering for Definity/sup TM/, Optison/sup TM/ and the microbeads was strong and increased with pressure suggesting a significant component of 2f/sub 0/ agent signal was due to non-linear propagation. However, the ratio of 2f/sub 0/ to f/sub 0/ scattering was higher for agent than for microbeads (20 dB for Definity/sup TM/) after correcting for frequency dependent microbead scattering. A test for bubble destruction at 20 MHz revealed that a significant subpopulation of bubbles could be disrupted. We conclude that non-linear scattering can be produced with high frequency ultrasound technology and currently available agents. This suggests the possibility of implementing non-linear detection and destruction techniques at high frequencies.
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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 | 0.000 | 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".