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Objective: The consequences associated with blood clots are numerous and are responsible for many deaths worldwide. The assessment of treatment efficacy is necessary for patient follow‐up and to detect treatment‐resistant patients. The aim of this study was to characterize the effect of treatment on blood clots in vitro using quantitative ultrasound parameters. Methods: Blood from 10 pigs was collected to form three clots per pig in gelatin phantoms. Clots were subjected to 1) no treatment, 2) rt‐PA (recombinant tissue plasminogen activator) treatment after 20 minutes of clotting, and 3) rt‐PA treatment after 60 minutes of clotting. Clots were weighted before and after the experiment to assess the treatment effect by the mass loss. The clot kinetics was studied over 100 minutes using elastography (Young's modulus, shear wave dispersion, and shear wave attenuation). Homodyne K‐distribution (HKD) parameters derived from speckle statistics were also studied during clot formation and dissolving (diffuse‐to‐total signal power ratio and intensity parameters). Results: Treated clots loosed significantly more mass than non‐treated ones (P <.005). A significant increase in Young's modulus was observed over time (P <.001), and significant reductions were seen for treated clots at 20 or 60 minutes compared with untreated ones (P <.001). The shear wave dispersion differed for treated clots at 60 minutes versus no treatments (P <.001). The shear wave attenuation decreased over time (P <.001), and was different for clots treated at 20 minutes versus no treatments (P <.031). The HKD intensity parameter varied over time (P <.032), and was lower for clots treated at 20 and 60 minutes than those untreated (P <.001 and P <.02). Conclusion: The effect of rt‐PA treatment could be confirmed by a decrease in Young's modulus and HKD intensity parameter. The shear wave dispersion and shear wave attenuation were sensitive to late and early treatments, respectively. The Young's modulus, shear wave attenuation, and HKD intensity parameter varied over time despite treatment. [ABSTRACT FROM AUTHOR]

Objective: Improve the characterization of mechanical properties of blood clots. Parameters derived from shear wave (SW) velocity and SW amplitude spectra were determined for gel phantoms and in vitro blood clots. Methods: Homogeneous phantoms and phantoms with gel or blood clot inclusions of different diameters and mechanical properties were analyzed. SW amplitude spectra were used to observe resonant peaks. Parameters derived from those resonant peaks were related to mimicked blood clot properties. Three regions of interest were tested to analyze where resonances occurred the most. For blood experiments, 20 samples from different pigs were analyzed over time during a 110‐minute coagulation period using the Young modulus, SW frequency dispersion, and SW attenuation. Results: The mechanical resonance was manifested by an increase in the number of SW spectral peaks as the inclusion diameter was reduced (P <.001). In blood clot inclusions, the Young modulus increased over time during coagulation (P <.001). Descriptive spectral parameters (frequency peak, bandwidth, and distance between resonant peaks) were linearly correlated with clot elasticity values (P <.001) with R2 =.77 for the frequency peak,.60 for the bandwidth, and.48 for the distance between peaks. The SW dispersion and SW attenuation reflecting the viscous behavior of blood clots decreased over time (P <.001), mainly in the early stage of coagulation (first minutes). Conclusion: The confined soft inclusion configuration favored SW mechanical resonances potentially challenging the computation of spectral‐based parameters, such as the SW attenuation. The impact of resonances can be reduced by properly selecting the region of interest for data analysis. [ABSTRACT FROM AUTHOR]

Background: There is a need for a specific atherosclerotic risk assessment for people living with HIV (PLWH). Setting: A machine learning classification model was applied to PLWH and control subjects with low-to-intermediate cardiovascular risks to identify associative predictors of diagnosed carotid artery plaques. Associations with plaques were made using strain elastography in normal sections of the common carotid artery and traditional cardiovascular risk factors. Methods: One hundred two PLWH and 84 control subjects were recruited from the prospective Canadian HIV and Aging Cohort Study (57 ± 8 years; 159 men). Plaque presence was based on clinical ultrasound scans of left and right common carotid arteries and internal carotid arteries. A classification task for identifying subjects with plaque was defined using random forest (RF) and logistic regression models. Areas under the receiver operating characteristic curves (AUC-ROCs) were applied to select 5 among 50 combinations of 4 or less features yielding the highest AUC-ROCs. Results: To retrospectively classify individuals with and without plaques, the 5 most discriminant combinations of features had AUC-ROCs between 0.76 and 0.79. AUC-ROCs from RF were statistically significantly higher than those obtained with logistic regressions (P = 0.0001). The most discriminant features of RF classifications in PLWH were age, smoking status, maximum axial strain and pulse pressure (equal weights), and sex and antiretroviral therapy exposure (equal weights). When considering the whole population, the HIV status was identified as a cofactor associated with carotid artery plaques. Conclusions: Strain elastography adds to traditional cardiovascular risk factors for identifying individuals with carotid artery plaques. [ABSTRACT FROM AUTHOR]

Objective: To study the impact of varying the external compression exerted by the ultrasound probe when performing a carotid strain elastography exam. Methods: Nine healthy volunteers (mean age 43 years ±13 years; 6 men) underwent a vascular ultrasound elastography exam using a custom made sound feedback handle embedding the probe, and allowing the sonographer to adjust the applied compression. A clinical standard practice (SP) force was first recorded, and then predetermined compression (PDC) forces were applied, ranging from 0 to 5 N for the left common carotid artery (CCA) or 2–12 N for the left internal carotid artery (ICA). Six carotid elastography features, namely maximum and cumulated axial strains, maximum and cumulated shear strains, cumulated axial translation, and cumulated lateral translation were assessed with noninvasive vascular elastography (NIVE) on near and far walls of carotids. The carotid intima media thickness (IMT) and diameter were also measured. Results: All elastography features on the near wall of both CCA and ICA decreased statistically significantly as the PDC force increased; this association was also observed for half of the features on the far wall. Three NIVE features at the lowest PDC force (out of 72 that were tested) were statistically significantly different than values at the SP force. Overall, NIVE showed some variance to probe compression with linear regression slopes revealing changes of 10.1%–45.6% in magnitude over the whole compression range on both walls. The maximum IMT for the ICA near wall, and carotid lumen diameters of both CCA and ICA were statistically significantly associated with PDC forces; these features underwent a decrease of 10.2%, 36.2%, and 17.6%, respectively, over the whole range of PDC force increase. Other IMT measurements were not statistically significantly associated with applied PDC forces. Conclusion: These results suggest the need of technical guidelines for carotid strain elastography. Using the lowest probe compression while allowing a good B‐mode image quality is recommended to improve the robustness of NIVE measurements. [ABSTRACT FROM AUTHOR]

Background: Childhood obesity is linked to higher adult mortality and morbidity from atherosclerosis. It is primordial to detect at-risk children earlier-on to prevent disease progression. Carotid intima-media thickness (IMT) is a subclinical radiological marker for early atherosclerosis. B-mode ultrasound is a known technique to assess IMT, but no gold standard technique exists in children. Non-invasive vascular elastography (NIVE) using speckle statistics is an innovative alternative to evaluate IMT and adds by providing translation, strain and shear strain measurements. Validation studies for both techniques lack in children. Purpose: Validate the reproducibility of the 2 techniques in Canadian children. Methods: We conducted a prospective study where anthropometry, blood pressure, IMT and elastography were measured. Six operators obtained 2 measurements for both carotid arteries using both techniques, for a total of 720 measurements. Inter- and intra-class correlation coefficients (ICC) were calculated for each measurement technique and elastography parameters. Results: 30 participants (13.0 ± 1.26 years, 17 girls) were recruited. Twelve were overweight. No significant difference was found in mean IMT between weight groups for either technique (P =.15 and P =.60). We found excellent inter- (ICC =.98 [95% Confidence Interval (CI):.97;.99]) and intra- (ICC =.90-.93) operator reliability for the B-mode technique, and good inter (ICC =.70 [95% CI:.47;.85]) and intra- (ICC =.71-.91) operator reliability for the NIVE-based technique. Poor reliability was found between techniques (ICC =.30 [95% CI: −.31;.65). For elastography parameters, translation was the most reliable (ICC =.94-.95). Conclusion: IMT measurement is reproducible in children but not between techniques. NIVE gives the advantage of evaluating elastography. [ABSTRACT FROM AUTHOR]

Objective: Vulnerable and nonvulnerable carotid artery plaques have different tissue morphology and composition that may affect plaque biomechanics. The objective of this study is to evaluate plaque vulnerability with the use of ultrasound noninvasive vascular elastography (NIVE)., Materials and Methods: Thirty-one patients (mean [± SD] age, 69 ± 7 years) with stenosis of the internal carotid artery of 50% or greater were enrolled in this cross-sectional study. Elastography parameters quantifying axial strain, shear strain, and translation motion were used to characterize carotid artery plaques as nonvulnerable, neovascularized, and vulnerable. Maximum axial strain, cumulated axial strain, mean shear strain, cumulated shear strain, cumulated axial translation, and cumulated lateral translations were measured. Cumulated measurements were summed over a cardiac cycle. The ratio of cumulated axial strain to cumulated axial translation was also evaluated. The reference method used to characterize plaques was high-resolution MRI., Results: According to MRI, seven plaques were vulnerable, 12 were nonvulnerable without neovascularity, and 12 were nonvulnerable with neovascularity (a precursor of vulnerability). The two parameters cumulated axial translation and the ratio of cumulated axial strain to cumulated axial translation could discriminate between nonvulnerable plaques and vulnerable plaques or determine the presence of neovascularity in nonvulnerable plaques (which was also possible with the mean shear strain parameter). All parameters differed between the non-vulnerable plaque group and the group that combined vulnerable plaques and plaques with neovascularity. The most discriminating parameter for the detection of vulnerable neovascularized plaques was the ratio of cumulated axial strain to cumulated axial translation (expressed as percentage per millimeter) (mean ratio, 39.30%/mm ± 12.80%/mm for nonvulnerable plaques without neovascularity vs 63.79%/mm ± 17.59%/mm for vulnerable plaques and nonvulnerable plaques with neovascularity, p = 0.002), giving an AUC value of 0.886., Conclusion: The imaging parameters cumulated axial translation and the ratio of cumulated axial strain to cumulated axial translation, as computed using NIVE, were able to discriminate vulnerable carotid artery plaques characterized by MRI from nonvulnerable carotid artery plaques. Consideration of neovascularized plaques improved the performance of NIVE. NIVE may be a valuable alternative to MRI for carotid artery plaque assessment.