Circumferential lesion formation around the pulmonary veins in the left atrium with focused ultrasound using a 2D-array endoesophageal device: a numerical study
Bibliographic record
Abstract
Atrial fibrillation (AF) is the most frequently sustained cardiac arrhythmia affecting humans. The electrical isolation by ablation of the pulmonary veins (PVs) in the left atrium (LA) of the heart has been proven as an effective cure of AF. The ablation consists mainly in the formation of a localized circumferential thermal coagulation of the cardiac tissue surrounding the PVs. In the present numerical study, the feasibility of producing the required circumferential lesion with an endoesophageal ultrasound probe is investigated. The probe operates at 1 MHz and consists of a 2D array with enough elements (114 x 20) to steer the acoustic field electronically in a volume comparable to the LA. Realistic anatomical conditions of the thorax were considered from the segmentation of histological images of the thorax. The cardiac muscle and the blood-filled cavities in the heart were identified and considered in the sound propagation and thermal models. The influence of different conditions of the thermal sinking in the LA chamber was also studied. The circumferential ablation of the PVs was achieved by the sum of individual lesions induced with the proposed device. Different scenarios of lesion formation were considered where ultrasound exposures (1, 2, 5 and 10 s) were combined with maximal peak temperatures (60, 70 and 80 degrees C). The results of this numerical study allowed identifying the limits and best conditions for controlled lesion formation in the LA using the proposed device. A controlled situation for the lesion formation surrounding the PVs was obtained when the targets were located within a distance from the device in the range of 26 +/- 7 mm. When combined with a maximal temperature of 70 degrees C and an exposure time between 5 and 10 s, this distance ensured preservation of the esophageal structures, controlled lesion formation and delivery of an acoustic intensity at the transducer surface that is compatible with existing materials. With a peak temperature of 70 degrees C, the device and setup presented here induced highly localized lesions with a lesion volume varying from 10 +/- 4 to 18 +/- 7 mm(3) for an ultrasound exposure between 5 and 10 s, respectively, while the intensity varied from 26 +/- 7 to 20 +/- 6 W cm(-2).
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".