Evaluation of the algorithm for automatic identification of the common carotid artery in ARTSENS.
TL;DR: The detailed algorithm and its extensive evaluation based on simulation and clinical studies are presented and it was demonstrated that the algorithm can be used in real-time with few trade-offs which do not affect the accuracy of CCA identification.
Abstract: Arterial compliance (AC) is an indicator of the risk of cardiovascular diseases (CVDs) and it is generally estimated by B-mode ultrasound investigation. The number of sonologists in low- and middle-income countries is very disproportionate to the extent of CVD. To bridge this gap we are developing an image-free CVD risk screening tool–arterial stiffness evaluation for non-invasive screening (ARTSENS™) which can be operated with minimal training. ARTSENS uses a single element ultrasound transducer to investigate the wall dynamics of the common carotid artery (CCA) and subsequently measure the AC. Identification of the proximal and distal walls of the CCA, in the ultrasound frames, is an important step in the process of the measurement of AC. The image-free nature of ARTSENS creates some unique issues which necessitate the development of a new algorithm that can automatically identify the CCA from a sequence of A-mode radio-frequency (RF) frames. We have earlier presented the concept and preliminary results for an algorithm that employed clues from the relative positions and temporal motion of CCA walls, for identifying the CCA and finding the approximate wall positions. In this paper, we present the detailed algorithm and its extensive evaluation based on simulation and clinical studies. The algorithm identified the wall position correctly in more than 90% of all simulated datasets where the signal-to-noise ratio was greater than 3 dB. The algorithm was then tested extensively on RF data obtained from the CCA of 30 human volunteers, where it successfully located the arterial walls in more than 70% of all measurements. The algorithm could successfully reject frames where the CCA was not present thus assisting the operator to place the probe correctly in the image-free system, ARTSENS. It was demonstrated that the algorithm can be used in real-time with few trade-offs which do not affect the accuracy of CCA identification. A new method for depth range selection that leads to significant performance improvements has also been demonstrated.
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TL;DR: The feasibility of calibration-free, cuffless BP measurement at an arterial site of interest was demonstrated with a level of acceptable accuracy and the potential utility of the proposed method and system in hypertension screening and local evaluation of arterial stiffness indices was demonstrated.
Abstract: Objective: We propose a calibration-free method and system for cuffless blood pressure (BP) measurement from superficial arteries. A prototype device with bi-modal probe arrangement was designed and developed to estimate carotid BP – an indicator of central aortic pressure. Methods: Mathematical models relating BP parameters of an arterial segment to its dimensions and local pulse wave velocity (PWV) are introduced. A bi-modal probe utilizing ultrasound and photoplethysmograph sensors was developed and used to measure diameter values and local PWV from the carotid artery. Carotid BP was estimated using the measured physiological parameters without any subject- or population-specific calibration procedures. The proposed cuffless BP estimation method and system were tested for accuracy, usability, and for potential utility in hypertension screening, on a total of 83 subjects. Results: The prototype device demonstrated its capability of detecting beat-by-beat arterial dimensions and local PWV simultaneously. Carotid diastolic BP (DBP) and systolic BP (SBP) were estimated over multiple cardiac cycles in real-time. The absolute error in carotid DBP was Conclusion: The feasibility of calibration-free, cuffless BP measurement at an arterial site of interest was demonstrated with a level of acceptable accuracy. The study also demonstrated the potential utility of the proposed method and system in hypertension screening and local evaluation of arterial stiffness indices. Significance: Novel approach for calibration-free cuffless BP estimation; a potential tool for local BP measurement and hypertension screening.
60 citations
Cites methods from "Evaluation of the algorithm for aut..."
...instantaneous motion [30], capturing of end-diastolic diameter and distention waveforms [31], beat-by-beat evaluation of diameter parameters, and real-time elimination of non-ideal cardiac cycles were automatically performed by the developed measurement software....
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...arterial walls by analyzing the inherent out of phase motion of the wall echoes (as the artery contracts and relaxes during each cardiac cycle) using sliding window covariance-based method [19], [30]....
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TL;DR: A novel approach using the autocorrelation of echoes from opposite walls of the artery has been discussed, to bring down the curve fitting time and facilitate processing on low-end processors.
Abstract: Over past few years, we are developing a system for facilitating large scale screening of patients for cardiovascular risk - ARTSENS. ARTSENS is an image-free device that uses a single element ultrasound transducer to obtain non-invasive measurements of arterial stiffness (AS) in a fully automated manner. AS is directly proportional to end-diastolic lumen diameter (�� �� ). Multi- layered structure of the arterial walls and indistinct characteristics of intima-lumen interface (ILI) makes it quite difficult to accurately estimate �� �� in A-Mode radio-frequency (RF) frames obtained from ARTSENS. In this paper, we propose a few methods based on fitting simple mathematical models to the echoes from arterial walls, followed by a novel method to fuse the information from curve fitting error and distension curve to arrive at an accurate measure of �� ��. To bring down the curve fitting time and facilitate processing on low-end processors, a novel approach using the autocorrelation of echoes from opposite walls of the artery has been discussed. The methods were analyzed for their comparative accuracy against reference �� �� obtained from 85 human volunteers using Hitachi-Aloka eTRACKING system. �� �� from all reported methods show strong and statistically significant positive correlation with eTRACKING and mean error of less than 7 % could be achieved. As expected, �� �� from all methods show significant positive correlation with age.
49 citations
TL;DR: This review aims to explain the biomechanical factors that are responsible for the formation and development of IH and their relationship with compliance mismatch and address the current methods used to measure compliance both in vitro and in vivo.
Abstract: Despite much effort, synthetic small diameter vascular grafts still face limited success due to vascular wall thickening known as intimal hyperplasia (IH). Compliance mismatch between graft and native vessels has been proposed to be one of a key mechanical factors of synthetic vascular grafts that could contribute to the formation of IH. While many methods have been developed to determine compliance both in vivo and in vitro, the effects of compliance mismatch still remain uncertain. This review aims to explain the biomechanical factors that are responsible for the formation and development of IH and their relationship with compliance mismatch. Furthermore, this review will address the current methods used to measure compliance both in vitro and in vivo. Lastly, current limitations in understanding the connection between the compliance of vascular grafts and the role it plays in the development and progression of IH will be discussed.
35 citations
TL;DR: The study results revealed the sensitivity of ARTSENS® Pen to detect changes in arterial stiffness with age, and the easy-to-use technology and the automated algorithms of the ARtsENS Pen make it suitable for cardiovascular risk assessment in resource-constrained settings.
Abstract: OBJECTIVE The conventional medical imaging modalities used for arterial stiffness measurement are non-scalable and unviable for field-level vascular screening. The need for an affordable, easy-to-operate automated non-invasive technologies remains unmet. To address this need, we present a portable image-free ultrasound device-ARTSENS® Pen, that uses a single-element ultrasound transducer for carotid stiffness evaluation. APPROACH The performance of the device was clinically validated on a cohort of 523 subjects. A clinical-grade B-mode ultrasound imaging system (ALOKA eTracking) was used as the reference. Carotid stiffness measurements were taken using the ARTSENS® Pen in sitting posture emulating field scenarios. MAIN RESULTS A statistically significant correlation (r > 0.80, p < 0.0001) with a non-significant bias was observed between the measurements obtained from the two devices. The ARTSENS® Pen device could perform highly repeatable measurements (with variation smaller than 10%) on a relatively larger percentage of the population when compared to the ALOKA system. The study results also revealed the sensitivity of ARTSENS® Pen to detect changes in arterial stiffness with age. SIGNIFICANCE The easy-to-use technology and the automated algorithms of the ARTSENS® Pen make it suitable for cardiovascular risk assessment in resource-constrained settings.
33 citations
TL;DR: The association of carotid stiffness with age, gender, hypertension/diabetes, smoking, and clustering of risk factors was studied and the trend persisted even after excluding hypertensives and subjects with diabetes.
Abstract: Objective: We investigate the field feasibility of carotid stiffness measurement using ARTSENS® Touch and report the first community-level data from India. Method: In an analytical cross-sectional survey among 1074 adults, we measured specific stiffness index ( $\beta $ ), pressure-strain elastic modulus ( $\text{E}_{\text {p}}$ ), arterial compliance (AC), and one-point pulse wave velocity (PWV $_{\beta }$ ) from the left common carotid artery. Data for established risk factors (waist circumference, blood pressure, plasma glucose, triglycerides, and HDL-C) were also collected. The association of carotid stiffness with age, gender, hypertension/diabetes, smoking, and clustering of risk factors was studied. Results: Measurements were repeatable with a relative difference (RD) between consecutive readings of $\sim 80$ % of arterial diameter values. The average RDs for $\beta $ , $\text{E}_{\text {p}}$ , AC, and PWV $_{\beta }$ , were 20.51%, 22.31%, 25.10%, and 14.13%, respectively. Typical range for stiffness indices among females and males were $\beta $ : 8.12 ± 3.59 vs 6.51 ± 2.78, $\text{E}_{\text {p}}$ : 113.24 ± 56.12 kPa vs 92.33 ± 40.65 kPa, PWV $_{\beta }$ : 6.32 ± 1.38 ms−1 vs 5.81 ± 1.16 ms−1, and AC: 0.54 ± 0.36 mm2 kPa−1 vs 0.72 ± 0.38 mm2 kPa−1. Mean $\beta $ , $\text{E}_{\text {p}}$ , and PWV $_{\beta }$ increased (and mean AC decreased) across decades of age; the trend persisted even after excluding hypertensives and subjects with diabetes. The odds ratio of presence of multiple risk factors for $\text{E}_{\text {p}} \ge93.71$ kPa and/or PWV $_{\beta } \ge6.56$ ms−1 was ≥ 2.12 or above in males. In females, it was just above 2.00 for $\text{E}_{\text {p}} \ge91.21$ kPa and/or PWV $_{\beta } \ge5.10$ ms−1 and increased to ≥ 3.33 for $\text{E}_{\text {p}} \ge143.50$ kPa and ≥ 3.25 for PWV $_{\beta } \ge7.31$ ms−1. Conclusion: The study demonstrated the feasibility of carotid stiffness measurement in a community setting. A positive association between the risk factors and carotid artery stiffness provides evidence for the device’s use in resource-constrained settings. Clinical Impact: The device paves the way for epidemiological and clinical studies that are essential for establishing population-level nomograms for wide-spread use of carotid stiffness in clinical practice and field screening of ‘at-risk’ subjects.
25 citations
References
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TL;DR: In this paper, the reduction in speckle that can be obtained with a compound scan with maximum amplitude writing is computed and the condition for the independence of two amplitude values is derived.
Abstract: Ultrasound images obtained with a simple linear or sector scan show a granular appearance, called "speckle." This speckle is analyzed. The reduction in speckle that can be obtained with a compound scan with maximum amplitude writing is computed. The reduction in speckle is almost as large as can be obtained with averaging. It depends on the number of independent amplitude values that are measured. The condition for the independence of two amplitude values is derived, and thus a limit is given for the possible reduction in speckle.
1,096 citations
TL;DR: In non-Western countries, deaths due to cardiovascular disease tend to occur a decade or two earlier than in Western countries, and the trends are similar to that in the West.
Abstract: In non-Western countries, deaths due to cardiovascular disease tend to occur a decade or two earlier than in Western countries. Dr. K. Srinath Reddy explains the trends.
437 citations
TL;DR: Common carotid IMT anddistensibility are clear markers of cardiovascular risk in patients who already have vascular disease or atherosclerotic risk factors and IMT appears to discriminate between low- and high-risk patients better than distensibility.
Abstract: Background—Common carotid intima-media thickness (IMT) and distensibility are markers of structural and functional vessel wall properties. Both parameters have been found in population-based studies to be associated with cardiovascular risk factors and prevalent cardiovascular disease. We investigated cross-sectionally whether IMT and distensibility are associated with cardiovascular risk in patients who already have vascular disease or atherosclerotic risk factors and evaluated the diagnostic ability of IMT and distensibility to discriminate between low- and high-risk patients. Methods and Results—IMT and distensibility (change of diameter) of the left and right common carotid arteries were measured in the first 570 patients (537 for distensibility) enrolled in the Second Manifestations of ARTerial disease (SMART) study, a cohort study among patients with a manifestation of vascular disease or cardiovascular risk factors. Three risk scores were used to classify each patient’s vascular risk. Areas under t...
378 citations
Journal Article•
TL;DR: Recent evidence indicating that the burden of coronary heart disease in the Indian subcontinent is largely explained on the basis of traditional risk factors challenges the common thinking that South Asian ethnicity per se is a strong independent risk factor for coronaryHeart disease.
Abstract: Ischaemic heart disease and stroke are among the most common causes of death and disability in the world. The Indian subcontinent (including India, Pakistan, Bangladesh, Sri Lanka, and Nepal) has among the highest rates of cardiovascular disease (CVD) globally. Previous reports have highlighted the high CVD rates among South Asian immigrants living in Western countries, but the enormous CVD burden within the Indian subcontinent itself has been underemphasized. In this review, we discuss the existing data on the prevalence of CVD and its risk factors in the Indian subcontinent. We also review recent evidence indicating that the burden of coronary heart disease in the Indian subcontinent is largely explained on the basis of traditional risk factors, which challenges the common thinking that South Asian ethnicity per se is a strong independent risk factor for coronary heart disease. Finally, we suggest measures to implement in policy, capacity building, and research to address the CVD epidemic in the Indian subcontinent.
303 citations
TL;DR: Knowledge of the arterial wall elastic modulus and the parameters required for its determination can provide important insight into structural changes occurring within the arterIAL wall with age and sex, and possibly with the onset of very early arterial disease.
Abstract: The Atherosclerosis Risk in Communities Study is a prospective investigation of the etiology and natural history of atherosclerosis and the etiology of clinical disease in four US communities. Noninvasive ultrasonic methods were used to determine mean wall thickness (WT), radius (R), and circumferential arterial strain (CAS) in the left common carotid artery of 3,321 white male and female study participants between the ages of 45 and 64 years. The mean and standard deviation of Young9s elastic modulus (Y) in 5-year age groups were determined for each sex by combining the ultrasonic data with concurrent noninvasive measurements of pulse pressure (PP) in the right brachial artery using the equation Y = (R/WT) x (PP/CAS). Significant (p = 0.0001) age group differences in Y were observed in both sexes, with the mean value increasing from 701 kPa in women and 771 kPa in men in the 45-49-year-old age group to 965 and 983 kPa, respectively, in the 60-64-year-old age group. Significant (p = 0.0001) age group differences were also observed for WT, the WT/R ratio, PP, CAS, and the PP/CAS ratio in both sexes. A sex difference in Y was detected (male greater than female, p = 0.0006) only in the 45-49-year-old age group. Significant (p less than 0.0001) sex differences were found, with men having a greater lumen diameter calculated as 2 x (R - WT), a greater WT, and a greater 2R in all age groups. The WT/R ratio did not differ in both sexes in all age groups. Knowledge of the arterial wall elastic modulus and the parameters required for its determination can provide important insight into structural changes occurring within the arterial wall with age and sex, and possibly with the onset of very early arterial disease.
196 citations