an-image-free-ultrasound-based-approach-for-combined-assessment-local

An Image-Free Ultrasound-Based Approach for Combined Assessment of Local and Regional Arterial Stiffness in Humans

Arterial stiffness is a cardinal marker of vascular aging, representing the cumulative impact of mechanical and biological stressors on the vessel wall ...

Indian Institute of Technology Madras

IIT Madras

The manual measurement of arterial diameter and wall thickness using imaging modalities demand expertise, and the state-of-art automated or semi-automated measurement features are seldom available in the entry-level systems. The advanced ultrasound modalities are expensive, non-scalable, and less favorable for field and resource-constrained settings. In this work, we present a novel method to measure arterial diameter (D), surrogate intima-media thickness (sIMT), and with them their intra-cardiac cycle changes by employing an affordable image-free ultrasound technology.

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

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.

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

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 (MGD) 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.The proposed model decomposes the arterial pressure waveform using weighted and shifted multi-Gaussians, which are then uniquely combined to yield the forward (()) and backward (()) pressure wave. A study using the database of healthy (virtual) subjects was used to evaluate the performance of MGDat the carotid artery and was compared against reference flow-based WSA methods.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() and() were obtained. When compared with the reference counterparts, the pulse pressures (Δand Δ), as well as reflection quantification indices, showed a statistically significant strong correlation ( > 0.96, < 0.0001) and ( > 0.83, < 0.0001) respectively, with an insignificant ( > 0.05) bias.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.

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

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.

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

Current ultrasound methods for recognition and motion-tracking of arterial walls are suited for image-based B-mode or M-mode scans but not adequately robust for single-line image-free scans. We introduce a time-warping-based technique to address this need. Its performance was validated through simulations and in-vivo trials on 21 subjects. The method recognized wall locations with 100 % precision for simulated frames (SNR > 10 dB). Clustering detections for multiple frames achieved sensitivity >98 %, while it was ∼90 % without clustering. The absence of arterial walls was predicted with 100 % specificity. In-vivo results corroborated the performance outcomes yielding a sensitivity ≥94 %, precision ≥98 %, and specificity ≥98 % using the clustering scheme. Further, excellent frame-to-frame tracking accuracy (absolute error <3 %, RMSE <2 μm) was demonstrated. Image-free measurements of peak arterial distension agreed with the image-based ones, within an error of 1.08 ± 3.65 % and RMSE of 38 μm. The method discerned the presence of arterial walls in A-mode frames, robustly localized, and tracked them even when they were proximal to hyperechoic regions or slow-moving tissue structures. Unification of delineation techniques with the proposed methods facilitates a complete image-free framework for measuring arterial dynamics and the development of reliable A-mode devices.

Time-warping for robust automated arterial wall-recognition and tracking from single-scan-line ultrasound signals.

Ethnicity impacts cardiovascular disease (CVD) risk, and South Asians demonstrate a higher risk than White Europeans. Arterial stiffness is known to contribute to CVD, and differences in arterial stiffness between ethnicities could explain the disparity in CVD risk. We compared central and local arterial stiffness between White Europeans and South Asians and investigated which factors are associated with arterial stiffness.

Central and local arterial stiffness in White Europeans compared to age-, sex-, and BMI-matched South Asians.

Sedentary behavior (SB) may affect arterial stiffness, preceding the development of cardiovascular disease. We investigated the association of objectively measured SB with arterial stiffness. We also investigated factors that affected this association. We recruited adult volunteers and measured SB with thigh-worn accelerometery for 24 hrs/day for eight consecutive days. Central (carotid-femoral pulse wave velocity, cfPWV, gold standard) and local carotid arterial stiffness (stiffness index Beta and pressure-strain elasticity E) were measured with ultrasound. Linear regression was used and adjusted for demographics, cardiometabolic factors, and moderate-to-vigorous physical activity (MVPA) volume. Effect modification was studied with interaction terms. Participants (N = 664, 64 (standard deviation: 11, range: 23-89) years, 397 (59.8%) male) demonstrated 9.1 (1.6) hrs/day of SB, and arterial stiffness was 8.6 (3.0) m/s for cfPWV, 6.4 (2.9) for Beta, and 87 (43) kPa for E. SB was not associated with cfPWV (β = 0.04 95% CI (-0.11, 0.18), p = 0.60). The association of SB with local arterial stiffness was modified by systolic blood pressure (SBP) and MVPA volume. Stratified analyses revealed positive associations of SB with Beta (β = 0.29 (0.05, 0.53), p = 0.016) and E (β = 4.83 (1.39, 8.27), p = 0.006) in participants with SBP > 134 mmHg or > 103 min/day of MVPA (β = 0.23 (0.03, 0.42), p = 0.024 and β = 3.55 (0.82, 6.29), p = 0.011, respectively). We found no association of objectively measured SB with central arterial stiffness. However, SB was positively associated with local carotid stiffness in participants with higher SBP or MVPA levels. In certain subgroups, SB may affect carotid arterial stiffening, reinforcing the relation between SB and cardiovascular disease.

Association of Objectively Measured Sedentary Behavior With Arterial Stiffness: Findings From the Nijmegen Exercise Study.

The local pulse wave velocity (PWV) from large elastic arteries and its pressure-dependent changes within a cardiac cycle are potential biomarkers for cardiovascular risk stratification. However, pulse wave reflections can impair the accuracy of local PWV measurements. We propose a method to measure pressure-dependent variations in local PWV while minimizing the influence of pulse wave reflections. The PWV is computed from the pulse transit time between two forward-traveling pulse waveforms obtained across known path length, after measured/modelled flow-based wave separation analysis (WSA). An in-vivo study of 60 participants (24 female), was conducted to compare inter- and intra-cycle variations in PWV obtained from measured and forward pulse waves. For this, proximal and distal diameter waveforms from the carotid artery, along with carotid tonometry, were recorded using a custom bi-modal arterial probe. The carotid blood flow for WSA was captured with an ultrasound imaging system. The reference PWV was derived from the Bramwell-Hill equation. After WSA, the reliability of PWV measurement improved with coefficient of variation reducing from 25% to 10% near the peak of the pulse waves and matched the reference PWV with no statistically significant difference. The average PWV at foot of the pulse wave before and after WSA were comparable to the reference PWV with no statistically significant difference. The coherence of carotid pulse pressure obtained from the mean values of PWV within a cardiac cycle after WSA with that of the carotid pulse pressure from tonometry, substantiates the results obtained for reflection-free PWV. The reliability of measuring local PWV and its pressure dependent variations within a cardiac cycle is improved by combining transit-time approach with WSA.

Measurement of pressure dependent variations in local pulse wave velocity within a cardiac cycle from forward travelling pulse waves.

Jugular venous pulse (JVP) waveform contour is directly linked to right atrial hemodynamics and is a potential tool for diagnosing various cardiovascular diseases. The reference standard, central venous line catheterization, while precise, is restricted to critical care units owing to the necessity for surgical procedures and specialized operator skills. Conventional ultrasound imaging systems can reliably measure jugular venous vessel dynamics but are hindered by low operational frame rates, large form factors, and the requirement for trained operators. In this study, we propose a portable system using single-element ultrasound technology for reliable JVP waveform acquisition and methods for quantifying the JVP contour features. The performance of the system and method was validated against a reference ultrasound imaging system in a preclinical study on 65 asymptomatic volunteers (27 female). Operating at an acquisition rate of 250 Hz, the system reliably captures JVP waveforms with a temporal resolution of 4 ms. The maximum and minimum jugular venous diameter measurements showed a statistically significant and strong correlation with the reference measurements (r = 0.93 and r = 0.86, respectively, p < 0.001). The devised algorithms effectively segmented JVP cycles and analyzed their contour features with a sensitivity and specificity of 92%. These results provide preliminary evidence for the potential use of the developed system for high-fidelity JVP waveform acquisition and pulse contour feature assessment. The ability to accurately evaluate the JVP contour characteristics can provide insights into right atrial hemodynamics, potentially facilitating the early detection and monitoring of vascular anomalies.

Article	Year
Automated measurement of compression-decompression in arterial diameter and wall thickness by image-free ultrasound. Computer methods and programs in biomedicine\| PubMed ID: 32474251	2020
High-frame-rate A-mode ultrasound for calibration-free cuffless carotid pressure: feasibility study using lower body negative pressure intervention. Blood pressure\| PubMed ID: 35014940	2022
Arterial pressure pulse wave separation analysis using a multi-Gaussian decomposition model. Physiological measurement\| PubMed ID: 35537402	2022
Image-free ultrasound for local and regional vascular stiffness assessment: the ARTSENS Plus. Journal of hypertension\| PubMed ID: 35730407	2022
Time-warping for robust automated arterial wall-recognition and tracking from single-scan-line ultrasound signals. Ultrasonics\| PubMed ID: 36031705	2022
Central and local arterial stiffness in White Europeans compared to age-, sex-, and BMI-matched South Asians. PloS one\| PubMed ID: 37616275	2023
Association of Objectively Measured Sedentary Behavior With Arterial Stiffness: Findings From the Nijmegen Exercise Study. Scandinavian journal of medicine & science in sports\| PubMed ID: 39501785	2024
Measurement of pressure dependent variations in local pulse wave velocity within a cardiac cycle from forward travelling pulse waves. Scientific reports\| PubMed ID: 39856220	2025
Single-element ultrasound system for high-resolution jugular venous pulse contour detection. Scientific reports\| PubMed ID: 40263608	2025
Author Correction: Single-element ultrasound system for high-resolution jugular venous pulse contour detection. Scientific reports\| PubMed ID: 40500306	2025

Kiran V. Raj

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