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A Flexible Ultrasound Array for Local Pulse Wave Velocity Monitoring

Cardiovascular diseases (CVDs) have shown a huge impact on the number of deaths in the world. Thus, common carotid artery (CCA) segmentation and intima-media thickness (IMT) measurements have been significantly implemented to perform early diagnosis of CVDs by analyzing IMT features. Using computer vision algorithms on CCA images is not widely used for this type of diagnosis, due to the complexity and the lack of dataset to do it. The advancement of deep learning techniques has made accurate early diagnosis from images possible. In this paper, a deep-learning-based approach is proposed to apply semantic segmentation for intima-media complex (IMC) and to calculate the cIMT measurement. In order to overcome the lack of large-scale datasets, an encoder-decoder-based model is proposed using multi-image inputs that can help achieve good learning for the model using different features. The obtained results were evaluated using different image segmentation metrics which demonstrate the effectiveness of the proposed architecture. In addition, IMT thickness is computed, and the experiment showed that the proposed model is robust and fully automated compared to the state-of-the-art work.

Encoder-Decoder Architecture for Ultrasound IMC Segmentation and cIMT Measurement

Objectives Absolute (ΔD) and relative (ΔD/D) arterial diameter distension, parameters related to the elasticity of the vessel, can be measured in superficial arteries using ultrasound-based vessel ‘wall tracking’ techniques. Currently available systems (e.g. the Wall Track System; WTS) measure the displacement of the media-adventitia transition (outer wall). We hypothesize that, given volume incompressibility of the vessel wall, ΔD and ΔD/D measured at the outer wall, significantly underestimate vessel distension at the lumen–intima interface (inner wall). Methods We measured ΔD and ΔD/D at both the inner and outer wall of the common carotid artery in 39 subjects (aged 18–83 years) using a new prototype ‘wall tracking’ system based on the Vivid-7 scanner (GE Vingmed Ultrasound, Horten, Norway). In addition, ΔD and ΔD/D were also measured using WTS. Results As anticipated, tracking the inner wall yielded lower diastolic diameters than when tracking the outer wall (Ddia = 5.70 ± 0.80 and 6.91 ± 0.98 mm, respectively, P < 0.0001). ΔD (0.54 ± 0.16 versus 0.49 ± 0.16 mm; P < 0.0001) and ΔD/D (0.096 ± 0.030 versus 0.071 ± 0.026, P < 0.0001) were indeed larger at the inner than at the outer wall. For WTS, Ddia, ΔD and ΔD/D were 7.04 ± 1.02 mm, 0.45 ± 0.14 mm and 0.066 ± 0.022, respectively. Conclusions On average, ΔD and ΔD/D are 10 and 25% higher on the inner than on the outer wall, respectively. Follow-up studies in larger cohort trials are mandatory to assess whether tracking the inner wall yields arterial function parameters with a higher cardiovascular prognostic potential.

Functional analysis of the common carotid artery: Relative distension differences over the vessel wall measured in vivo

Coronavirus disease 2019 (COVID-19) is reported to have long-term effects on cardiovascular health and physical functioning, even in the nonhospitalized population. The physiological mechanisms underlying these long-term consequences are however less well described. We compared cardiovascular risk factors, arterial stiffness, and physical functioning in nonhospitalized patients with COVID-19, at a median of 6 mo postinfection, versus age- and sex-matched controls. Cardiovascular risk was assessed using blood pressure and biomarker concentrations (amino-terminal pro-B-type-natriuretic-peptide, high-sensitive cardiac troponin I, C-reactive protein), and arterial stiffness was assessed using carotid-femoral pulse wave velocity. Physical functioning was evaluated using accelerometry, handgrip strength, gait speed and questionnaires on fatigue, perceived general health status, and health-related quality of life (hrQoL). We included 101 former patients with COVID-19 (aged 59 [interquartile range, 55–65] yr, 58% male) and 101 controls. At 175 [126–235] days postinfection, 32% of the COVID-19 group reported residual symptoms, notably fatigue, and 7% required post-COVID-19 care. We found no differences in blood pressure, biomarker concentrations, or arterial stiffness between both groups. Former patients with COVID-19 showed a higher handgrip strength (43 [33–52] vs. 38 [30–48] kg, P = 0.004) and less sleeping time (8.8 [7.7–9.4] vs. 9.8 [8.9–10.3] h/day, P < 0.001) and reported fatigue more often than controls. Accelerometry-based habitual physical activity levels, gait speed, perception of general health status, and hrQoL were not different between groups. In conclusion, one in three nonhospitalized patients with COVID-19 reports residual symptoms at a median of 6 mo postinfection, but we were unable to relate these symptoms to increases in cardiovascular risk factors, arterial stiffness, or physical dysfunction. NEW & NOTEWORTHY We examined cardiovascular and physical functioning outcomes in nonhospitalized patients with COVID-19, at a median of 6 mo postinfection. When compared with matched controls, minor differences in physical functioning were found, but objective measures of cardiovascular risk and arterial stiffness did not differ between groups. However, one in three former patients with COVID-19 reported residual symptoms, notably fatigue. Follow-up studies should investigate the origins of residual symptoms and their long-term consequences in former, nonhospitalized patients with COVID-19.

Long-term cardiovascular health status and physical functioning of nonhospitalized patients with COVID-19 compared with non-COVID-19 controls

Local pulse wave velocity (PWV), a metric of the target artery’s stiffness, has been emerging in its clinical value and adoption. State-of-the-art ultrasound technologies used to evaluate local PWV based on pulse waves’ features are sophisticated, non-real-time, and are not amenable for field and resource-constrained settings. In this work, we present an image-free ultrasound system to measure local PWV in real-time by employing a pair of ultrasound transducer elements. An <italic>in vitro</italic> study was performed on the arterial phantom to: 1) characterize the design aspects of the system and 2) validate its accuracy against beat-by-beat (invasive) local PWV measured by a reference dual-element catheter. Furthermore, a repeatability and reproducibility study on 33 subjects (21–52 years) investigated the in vivo measurement feasibility from the carotid artery. With the experimentally deduced optimal design (frame-rate <inline-formula> <tex-math notation="LaTeX">$=500$ </tex-math></inline-formula> Hz, RF sampling rate <inline-formula> <tex-math notation="LaTeX">$=125$ </tex-math></inline-formula> MHz, LPF cutoff <inline-formula> <tex-math notation="LaTeX">$=14$ </tex-math></inline-formula> Hz, and order <inline-formula> <tex-math notation="LaTeX">$=4$ </tex-math></inline-formula>), the system yielded repeatable beat-to-beat measurements (variability <inline-formula> <tex-math notation="LaTeX">$=1.9$ </tex-math></inline-formula>% and over 15 cycles) and achieved a high accuracy (root-mean-square-error <inline-formula> <tex-math notation="LaTeX">$=0.19$ </tex-math></inline-formula> m/s and absolute-percentage-error <inline-formula> <tex-math notation="LaTeX">$=2.4$ </tex-math></inline-formula>%) over a wide range of PWVs (2.7–11.4 m/s) from the phantom. Subsequently, on human subjects, the intra- and inter-operator PWV measurements were highly repeatable (intraclass correlation coefficient <inline-formula> <tex-math notation="LaTeX">$>0.92$ </tex-math></inline-formula>). The system does not impose a demand for special processors with high-computational power while offering real-time feedback on acquisition and measurement quality and provides local PWV online. Future large population and animal studies are required to establish the device’s clinical usability.

Image-Free Fast Ultrasound for Measurement of Local Pulse Wave Velocity: In Vitro Validation and In Vivo Feasibility

Automated measurement of compression-decompression in arterial diameter and wall thickness by image-free ultrasound.

Abstract Purpose Existing technologies to measure central blood pressure (CBP) intrinsically depend on peripheral pressure or calibration models derived from it. Pharmacological or physiological interventions yielding different central and peripheral responses compromise the accuracy of such methods. We present a high-frame-rate ultrasound technology for cuffless and calibration-free evaluation of BP from the carotid artery. The system uses a pair of single-element ultrasound transducers to capture the arterial diameter and local pulse wave velocity (PWV) for the evaluation of beat-by-beat BP employing a novel biomechanical model. Materials and methods System’s functionality assessment was conducted on eight male subjects (26 ± 4 years, normotensive and no history of cardiovascular risks) by perturbing pressure via short-term moderate lower body negative pressure (LBNP) intervention (−40 mmHg for 1 min). The ability of the system to capture dynamic responses of carotid pressure to LBNP was investigated and compared against the responses of peripheral pressure measured using a continuous BP monitor. Results While the carotid pressure manifested trends similar to finger measurements during LBNP, the system also captured the differential carotid-to-peripheral pressure response, which corroborates the literature. The carotid diastolic and mean pressures agreed with the finger pressures (limits-of-agreement within ±7 mmHg) and exhibited acceptable uncertainty (mean absolute errors were 2.4 ± 3.5 and 2.6 ± 4.0 mmHg, respectively). Concurrent to the literature, the carotid systolic and pulse pressures (PPs) were significantly lower than those of the finger pressures by 11.1 ± 9.4 and 11.3 ± 8.2 mmHg, respectively (p < .0001). Conclusions The study demonstrated the method’s potential for providing cuffless and calibration-free pressure measurements while reliably capturing the physiological aspects, such as PP amplification and dynamic pressure responses to intervention.

https://www.tandfonline.com/doi/pdf/10.1080/08037051.2021.2022453?needAccess=true

High-frame-rate A-mode ultrasound for calibration-free cuffless carotid pressure: feasibility study using lower body negative pressure intervention

Objective: The combined assessment of vascular health markers is crucial for identifying the cumulative burden of vascular risk factors early on, as well as the extent of vascular aging for effective prediction of future cardiovascular events. This work addresses the need for a currently nonexistent device or system that facilitates such combined assessment in clinical practice and large-scale screening settings. We report an image-free ultrasound device – ARTSENS Plus – developed for the measurement of local and regional arterial stiffness, central and peripheral blood pressure (BP), and vessel dimensions, all in one examination. Methods: A preclinical study on 90 asymptomatic individuals verified the device's functionality under ARTERY Society guidelines. The device's accuracy of stiffness measures was validated against the reference measures. Results: The interoperator and intraoperator variability was less than 7%. Carotid artery's lumen diameter and local stiffness indices and carotid–femoral regional pulse wave velocity showed excellent agreement with the references (absolute errors were less than 4.1, 9, and 4.1%, respectively). The carotid SBP was 10.02% lower than that of the brachial artery, as expected. Conclusion: The study demonstrated the device's ability to perform an effortless and reliable evaluation of the local and regional vascular stiffness and central BP with an accuracy that meets clinical standards.

Image-free ultrasound for local and regional vascular stiffness assessment: the ARTSENS Plus

Objective. Methods for separating the forward–backward components from blood pulse waves rely on simultaneously measured pressure and flow velocity from a target artery site. Modelling approaches for flow velocity simplify the wave separation analysis (WSA), providing a methodological and instrumentational advantage over the former; however, current methods are limited to the aortic site. In this work, a multi-Gaussian decomposition (MGD) modelled WSA (MGDWSA) is developed for a non-aortic site such as the carotid artery. While the model is an adaptation of the existing wave separation theory, it does not rely on the information of measured or modelled flow velocity. Approach. The proposed model decomposes the arterial pressure waveform using weighted and shifted multi-Gaussians, which are then uniquely combined to yield the forward (P F(t)) and backward (P B(t)) pressure wave. A study using the database of healthy (virtual) subjects was used to evaluate the performance of MGDWSA at the carotid artery and was compared against reference flow-based WSA methods. Main results. The MGD modelled pressure waveform yielded a root-mean-square error (RMSE) < 0.35 mmHg. Reliable forward–backward components with a group average RMSE <2.5 mmHg for P F(t) and P B(t) were obtained. When compared with the reference counterparts, the pulse pressures (ΔP F and ΔP B), as well as reflection quantification indices, showed a statistically significant strong correlation (r > 0.96, p < 0.0001) and (r > 0.83, p < 0.0001) respectively, with an insignificant (p > 0.05) bias. Significance. This study reports WSA for carotid pressure waveforms without assumptions on flow conditions. The proposed method has the potential to adapt and widen the vascular health assessment techniques incorporating pulse wave dynamics.

Kiran V Raj

Papers

Automated measurement of compression-decompression in arterial diameter and wall thickness by image-free ultrasound.

High-frame-rate A-mode ultrasound for calibration-free cuffless carotid pressure: feasibility study using lower body negative pressure intervention

Image-free ultrasound for local and regional vascular stiffness assessment: the ARTSENS Plus

Image-Free Fast Ultrasound for Measurement of Local Pulse Wave Velocity: In Vitro Validation and In Vivo Feasibility

Arterial pressure pulse wave separation analysis using a multi-Gaussian decomposition model