11C-6 New Observations on the Anisotropy of Ultrasound Blood Backscatter as a Function of Frequency and Shear Rate
Bibliographic record
Abstract
It is recognized that biological tissues with orientated structures show an angular dependence in echogenicity. Previous works on ultrasound (US) blood backscattering have pointed out that red blood cell (RBC) aggregates (or rouleaux) had privileged orientations in a tubular flow inducing measurable US anisotropic behaviours, but results are scarce. The non Newtonian blood velocity profile in tube flow may however be seen as an obstacle to the understanding of the anisotropic spatial organization of RBC aggregates. In this study, whole blood was circulated in a Couette flow apparatus, which allowed to predictably modulate the RBC aggregate sizes and orientations, and to quantify their respective effects on the angle dependent backscatter coefficient (BSC). Anticoagulated porcine bloods were adjusted to 40% hematocrit and inserted into the Couette flow apparatus, at 37degC. US data were acquired and analyzed using two broadband focused transducers at 20 MHz and 35 MHz. The BSC was measured at ten different insonification angles from 30deg to 150deg with respect to the direction of the blood flow, for shear rates of 2 s-1and 10 s-1. A control experiment was also conducted on porcine RBCs suspended in a saline solution (no aggregation). The results indicate no anisotropic effect for the saline suspension and a significant angular dependence for whole blood. At an incident frequency of 20 MHz, the anisotropy was 4.3 dB for a shear rate of 2 s-1, while it was 4.6 dB for a shear rate of 10 s"1. Similarly, at an incident frequency of 35 MHz, the anisotropy was 5.1 dB for a shear rate of 2 s-1and 6.2 dB for a shear rate of 10 s-1. Thus, the higher anisotropic variation at 35 MHz may indicate a better US sensitivity to the rouleaux orientation at that frequency. Furthermore, at a shear rate of 2 s-1, the maximum BSC was measured at an angle of 75deg, whereas at a shear rate of 10 s-1, it was maximum at an angle of 90deg. These last results suggest that the RBC aggregate orientation is shear rate dependent. In conclusion, the Couette flow system that was employed is a good strategy to predictably control the orientation of RBC aggregates as a function of the shear rate.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 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".