Optimization of subharmonic generation from ultrasound contrast agents at high frequency ultrasound
Bibliographic record
Abstract
The microcirculation can be differentiated from the surrounding tissue using high frequency ultrasound subharmonic imaging. This imaging technique relies on the detection of energy scattered from ultrasound contrast agents at half the transmit frequency due to their resonant oscillations. The current contrast agents and the subharmonic imaging parameters have not been optimized for high frequencies. Moreover, the origin of subharmonic generation from submicron bubbles is not well-understood. The size distribution of Definity™ phospholipid-shelled microbubbles was altered to find the optimal bubble size to be resonant over a wide range of high frequencies. The resonant behaviour of bubbles was investigated through in vitro attenuation measurements. The transmit frequency and pressure were varied to optimize the backscattered subharmonic signal. Alteration of Definity™ population significanatly improved the scattering for subharmonic imaging at 20 MHz. A peak negative pressure between 400 to 600 kPa is suggested for this frequency range.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".