CODED EXCITATION METHODS FOR ULTRASOUND HARMONIC IMAGING
Bibliographic record
Abstract
Coded excitation methods offer the potential for improving the SNR without increasing the peak transmitted power and without sacrificing resolution.Our study examines the potential application o f coded waveforms, specifically FM chirps, in harmonic imaging.Such a system, in which nonlinear echoes from tissue are used to form the image, requires the extraction and compression o f the second harmonic portion of the echo signal.Our objective is to obtain the second harmonic using just one transmission, thereby avoiding problems of frame rate reduction and movement artifacts associated with multiple transmission schemes.With the help o f an efficient method for predicting the transient nonlinear field from a focused transducer, design issues such as waveform and bandwidth selection, as well as filters for second harmonic extraction and compression are examined.Simulations reveal the presence of axial sidelobes in the compressed echo waveform as the bandwidth of the transmitted chirp is increased.These sidelobes, resulting from the overlap o f the fundamental and third harmonic bands with the second harmonic, cannot be removed using conventional Fourier filtering.Alternative filtering techniques which utilize the separation o f the harmonic bands o f a backscattered chirp in the joint time-frequency domain are suggested. s o m m a i r eLes méthodes d'excitation codée ont le potentiel d 'améliorer le ratio signal-bruit sans augmenter la puissance maximale transmise et sans sacrifier la résolution.Notre étude examine l'application potentielle de formes d'onde codées, plus spécifiquement de compression d 'impulsions FM pour imagerie harmonique.Dans un tel système, les échos non-linéaires provenant du tissu sont utilisés afin de former l'image, ce qui requiert l 'extraction et la compression de la deuxième portion harmonique du signal d'écho.Notre objectif est d 'obtenir le deuxième harmonique en utilisant seulement une transmission, évitant ainsi des problèmes de réduction du temps d 'image et d 'artefacts de mouvement associés avec de multiples schémas de transmission.En utilisant une méthode efficace de prédiction du champs nonlinéaire transitoire provenant d'un transducteur focalisé, des problèmes de conception tels que la sélection de forme d 'onde et de la largeur de bande, ainsi que de filtres pour l'extraction et la compression du deuxième harmonique sont examinés.Les simulations révèlent la présence de lobes latéraux axiaux dans la forme d'onde compressée au fur et a mesure que la largeur de bande de la compression d 'impulsion transmise est augmentée.Ces lobes latéraux, dus au chevauchement de la bande harmonique fondamentale et de la troisième bande avec la deuxième bande harmonique ne peuvent pas être enlevés en utilisant le filtrage conventionnel de Fourier.En tant qu'alternative, des techniques de filtrage utilisant la séparation de bandes harmoniques de compressions d 'impulsions rétrodiffusés dans le domaine commun de temps-fréquence sont suggérées.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.011 | 0.003 |
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".