Abstract 5960: Implementation of Noninvasive Subharmonic Pressure Estimation on a Commercial Ultrasound Scanner
Bibliographic record
Abstract
This project aims to monitor and quantify intra-cardiac pressures via contrast-enhanced subharmonic imaging. We have proposed subharmonic aided pressure estimation (SHAPE; U.S. Patent 6,302,845) utilizing microbubble-based contrast agent signals for the noninvasive estimation of hydrostatic blood pressures in the heart cavities and in this study implemented real-time SHAPE on a commercial US scanner. An experimental pulse-echo system for SHAPE was constructed based on two single element transducers assembled confocally at a 60° angle to each other. A transducer with a bandwidth of 38% and a center frequency of 2.2 MHz (Staveley, East Hartford, CT) was used as the transmitter and a second transducer with a bandwidth of 86% and a center frequency of 3.6 MHz (Etalon Inc., Lebanon, IN) was the receiver. Changes in first, second, and subharmonic amplitudes of 6 different US contrast agents were measured in vitro at hydrostatic pressures from 0 –186 mmHg, acoustic pressures from 0.35– 0.60 MPa and frequencies of 2.5– 6.6 MHz. The optimal parameters for SHAPE were determined using linear regression analysis and implemented on a Sonix RP scanner (Ultrasonix Medical Corp, Richmond, Canada). The real-time implementation of SHAPE was tested in vitro. Over the pressure range studied the 1st and 2nd harmonic amplitudes reduced ~2 dB for all US contrast agents. Over the same pressure range, the subharmonic amplitudes decreased by 10 –14 dB and excellent linear regressions were achieved with the hydrostatic pressure variations (r 2 >0.98, p < 0.001). The optimal sensitivity for SHAPE was achieved at a transmit frequency of 2.5 MHz (i.e., receiving at 1.25 MHz) at a 0.35 MPa acoustic pressure using Sonazoid (GE Healthcare, Oslo, Norway) which declined ~14.4 dB in vitro. A Sonix RP scanner was modified to implement SHAPE on a phased array transducer PA4 –2 with a frequency range from 1.5– 4.5 MHz. A pulse inversion technique was used and the subharmonic signals are displayed in real-time and can also be stored for off-line analysis. SHAPE offers the possibility of allowing pressure gradients in the heart to be obtained noninvasively. Future studies will include in vivo pressure measurements. Supported by AHA grant no 06554414 and NIH HL081892. This research has received full or partial funding support from the American Heart Association, AHA Great Rivers Affiliate (Delaware, Kentucky, Ohio, Pennsylvania & West Virginia).
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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 | 0.001 | 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 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".