A PC based system for non-invasive measurement of carotid artery compliance
05 May 2009-pp 680-685
TL;DR: A PC based system for non-invasive, in-vivo measurement of carotid artery compliance is proposed here and the accuracy and resolution has been found to meet the requirements of the application.
Abstract: A PC based system for non-invasive, in-vivo measurement of carotid artery compliance is proposed here. The equipment is a low cost and reliable alternative to the expensive B-mode scanner for vessel wall tracking and stiffness measurement of the artery. The system gives an accurate recording of the distensibility waveform of the carotid artery that could then be used to estimate the various measures of arterial compliance. The system is tested with phantom models of the carotid artery and the accuracy and resolution has been found to meet the requirements of the application. Results obtained from human trials have also been presented to illustrate the capability of the instrument to accurately measure carotid artery compliance.
Citations
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TL;DR: The feasibility of the novel ARTSENS device in performing accurate in vivo measurements of arterial stiffness is verified, a device for image free, noninvasive, automated evaluation of vascular stiffness amenable for field use.
Abstract: Vascular stiffness is an indicator of cardiovascular health, with carotid artery stiffness having established correlation to coronary heart disease and utility in cardiovascular diagnosis and screening. State of art equipment for stiffness evaluation are expensive, require expertise to operate and not amenable for field deployment. In this context, we developed ARTerial Stiffness Evaluation for Noninvasive Screening (ARTSENS), a device for image free, noninvasive, automated evaluation of vascular stiffness amenable for field use. ARTSENS has a frugal hardware design, utilizing a single ultrasound transducer to interrogate the carotid artery, integrated with robust algorithms that extract arterial dimensions and compute clinically accepted measures of arterial stiffness. The ability of ARTSENS to measure vascular stiffness in vivo was validated by performing measurements on 125 subjects. The accuracy of results was verified with the state-of-the-art ultrasound imaging-based echo-tracking system. The relation between arterial stiffness measurements performed in sitting posture for ARTSENS measurement and sitting/supine postures for imaging system was also investigated to examine feasibility of performing ARTSENS measurements in the sitting posture for field deployment. This paper verified the feasibility of the novel ARTSENS device in performing accurate in vivo measurements of arterial stiffness. As a portable device that performs automated measurement of carotid artery stiffness with minimal operator input, ARTSENS has strong potential for use in large-scale screening.
53 citations
Cites methods from "A PC based system for non-invasive ..."
...VALIDATION OF ARTSENS The performance of the signal processing algorithms, the repeatability and reproducibility of the instrument and ARTSENS usability in controlled laboratory settings have already been validated and reported [19]–[22]....
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TL;DR: A simple instrument for noninvasive in vivo evaluation of arterial compliance using a single element ultrasound transducer that can measure arterial distension with a precision better than 5 and the end-diastolic arterial diameter with an accuracy of 1%.
Abstract: Measurement of arterial distensibility is very important in cardiovascular diagnosis for early detection of coronary heart disease and possible prediction of future cardiac events. Conventionally, B-mode ultrasound imaging systems have been used along with expensive vessel wall tracking systems for estimation of arterial distension and calculation of various estimates of compliance. We present a simple instrument for noninvasive in vivo evaluation of arterial compliance using a single element ultrasound transducer. The measurement methodology is initially validated using a proof of concept pilot experiment using a commercial ultrasound pulser-receiver. A prototype system is then developed around a PXI chassis using LABVIEW software. The virtual instrument employs a dynamic threshold algorithm to identify the artery walls and then utilizes a correlation based tracking technique to estimate arterial distension. The end-diastolic echo signals are averaged to reduce error in the automated diameter measurement process. The instrument allows automated measurement of the various measures of arterial compliance with minimal operator intervention. The performance of the virtual instrument was first analyzed using simulated data sets to establish the maximum measurement accuracy achievable under different input signal to noise ratio (SNR) levels. The system could measure distension with accuracy better than 10 μm for positive SNR. The measurement error in diameter was less than 1%. The system was then thoroughly evaluated by the experiments conducted on phantom models of the carotid artery and the accuracy and resolution were found to meet the requirements of the application. Measurements performed on human volunteers indicate that the instrument can measure arterial distension with a precision better than 5%. The end-diastolic arterial diameter can be measured with a precision better than 2% and an accuracy of 1%. The measurement system could lead to the development of small, portable, and inexpensive equipment for estimation of arterial compliance suitable in mass screening of "at risk" patients. The automated compliance measurement algorithm implemented in the instrument requires minimal operator input. The instrument could pave the way for dedicated systems for arterial compliance evaluation targeted at the general medical practitioner who has little or no expertise in vascular ultrasonography.
37 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 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.
25 citations
03 Jul 2013
TL;DR: The ability of ARTSENS to detect artery anatomy and measure compliance was verified by in-vivo measurements conducted on 106 subjects, and the accuracy of compliance estimates were evaluated by comparison with a state of art imaging system.
Abstract: Evaluation of arterial compliance is significant in cardiovascular diagnosis for early detection of coronary heart disease. We present ARTSENS, an image-free system for non-invasive evaluation of arterial compliance in-vivo. The system utilizes a single element ultrasound probe with intelligent measurement algorithms to ensure accurate evaluation of local arterial compliance without an image. The ability of the system to detect artery anatomy and measure compliance was verified by in-vivo measurements conducted on 106 subjects. The accuracy of compliance estimates were evaluated by comparison with a state of art imaging system. The measurements made using ARTSENS showed strong correlation with those made using the imaging system. The ability of ARTSENS to detect age-related trends in arterial compliance was also investigated.
20 citations
Cites background from "A PC based system for non-invasive ..."
...We had previously demonstrated the utility of a single element ultrasound transducer to non-invasively measure arterial distension and end-diastolic diameter [5]....
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References
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TL;DR: Carotid artery stiffness is no independent risk factor for vascular events in patients with manifest arterial disease, however, in patients who differ with respect to baseline vascular risk, arterial stiffness, or systolic blood pressure, decreased stiffness may indicate a decreased risk of vascular events.
Abstract: Aims To study whether arterial stiffness is related to risk of new vascular events in patients with manifest arterial disease and to examine whether this relation varies between patients who differ with respect to baseline vascular risk, arterial stiffness, or systolic blood pressure (SBP).
Methods and results The study was performed in the first consecutive 2183 patients with manifest arterial disease enrolled in the SMART study (Second Manifestations of ARTerial disease), a cohort study among patients with manifest arterial disease or cardiovascular risk factors. Common carotid distension (i.e. the change in carotid diameter in systole relative to diastole) was measured at baseline by ultrasonography. With the distension, several stiffness parameters were determined. In the entire cohort, none of the carotid artery stiffness parameters was related to the occurrence of vascular events. However, decreased stiffness was related to decreased vascular risk in subjects with low baseline SBP. The relation of carotid stiffness with vascular events did not differ between tertiles of baseline risk and carotid stiffness.
Conclusion Carotid artery stiffness is no independent risk factor for vascular events in patients with manifest arterial disease. However, in patients with low SBP, decreased carotid stiffness may indicate a decreased risk of vascular events.
132 citations
"A PC based system for non-invasive ..." refers methods in this paper
...The system could be used along with statistical databases for mass screening of “at risk” individuals for atherosclerosis [6] and in predicting the risk of coronary heart disease....
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TL;DR: RCCA diameter is an important correlate of cardiac events, independent of IMT, but adds little to overall risk discrimination after risk factor adjustment.
Abstract: Arterial diameters enlarge in response to wall thickening, plaques, and many atherosclerotic risk factors. We hypothesized that right common carotid artery (RCCA) diameter would be independently associated with cardiac disease and improve risk discrimination. In a middle-aged, biracial population (baseline n = 11225), we examined associations between 1 standard deviation increments of baseline RCCA diameter with prevalent myocardial infarction (MI) and incident cardiac events (MI or cardiac death) using logistic regression and Cox proportional hazards models, respectively. Areas under the receiver operator characteristic curve (AUC) were used to estimate model discrimination. MI was present in 451 (4%) participants at baseline (1987–89), and incident cardiac events occurred among 646 (6%) others through 1999. Adjusting for IMT, RCCA diameter was associated with prevalent MI (female OR = 2.0, 95%CI = 1.61–2.49; male OR = 1.16, 95% CI = 1.04–1.30) and incident cardiac events (female HR = 1.75, 95% CI = 1.51–2.02; male HR = 1.27, 95% CI = 1.15–1.40). Associations were attenuated but persisted after adjustment for risk factors (not including IMT) (prevalent MI: female OR = 1.73, 95% CI = 1.40–2.14; male OR = 1.14, 95% CI = 1.02–1.28, and incident cardiac events: female HR = 1.26, 95% CI = 1.08–1.48; male HR = 1.19, 95% CI = 1.08–1.32). After additional adjustment for IMT, diameter was associated with incident cardiac events in women (HR = 1.18, 95% CI = 1.00–1.40) and men (HR = 1.17, 95% CI = 1.06–1.29), and with prevalent MI only in women (OR = 1.73; 95% CI = 1.37–2.17). In women, when adjustment was limited, diameter models had larger AUC than other models. RCCA diameter is an important correlate of cardiac events, independent of IMT, but adds little to overall risk discrimination after risk factor adjustment.
72 citations
"A PC based system for non-invasive ..." refers background in this paper
...The measurement of the common carotid artery diameter could help in improved diagnosis of cardiac events [5]....
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TL;DR: All available non-invasive methods focus on the quantification of a number of surrogate parameters that are related to the degree of arterial stiffness, and these derived parameters can often be quantified through use of specific parameters.
Abstract: Over the years, a number of methods have been proposed to assess arterial compliance (or its reverse, i.e. arterial stiffness) in humans. The growing interest towards such an evaluation is due to the relevant impact that altered compliance has on buffering the vascular consequences of continuous pulse amplitude changes. Several non-invasive approaches have been developed to make this evaluation suitable for a clinical setting [2]. The terms involved in these different calculations and methods are summarized in Table 1 [3], and should be referred to the general theory underlying these techniques [4,5]. All available non-invasive methods focus on the quantification of a number of surrogate parameters that are related to the degree of arterial stiffness. Three types of arterial stiffness can be considered: (i) systemic arterial stiffness (formerly explored by the ratio of pulse pressure and stroke volume, and now more and more frequently assessed by methods based on pulse contour analysis; (ii) regional or segmental arterial stiffness [commonly assessed by measuring pulsewave velocity (PVW)]; and (iii) local arterial stiffness of superficial arteries (measured by echo-tracking techniques) [6]. However, some of the devices or methods used in this field can explore more than one type of arterial stiffness. For this reason, their classification is often based not on the type of arterial stiffness explored, but on their methodological features, with the identification of three main groups of techniques: (i) methods based on the analysis of arterial pressure pulse waveform; (ii) methods based on the quantification of pulse transit time; and (iii) methods based on a direct estimation of arterial stiffness through the assessment of arterial diameter and of the corresponding distending pressure [7]. The derived parameters can often be quantified through use of specific
27 citations
"A PC based system for non-invasive ..." refers methods in this paper
...These are then used to calculate the various measures of carotid artery compliance such as elastic modulus, arterial distensibility, compliance and stiffness index [2, 3]....
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TL;DR: The arterial stiffening increases with the heart failure severity and shows a parallelism with the reduced ability of the heart to relax in response to transmural pressure, which may play a role in this alteration of arterial mechanical properties.
Abstract: Background Heart failure is accompanied by large artery wall stiffening. Aim of the present study was to see whether the stiffening correlates (1) with the severity of the disease, (2) with the concomitant diastolic dysfunction and (3) with plasma aldosterone concentration, i.e. the concentration of a substance stimulating vessel fibrosis.
Patients and methods We measured diameter ( D ) and distensibility (Dist) of a common carotid artery (CA) and abdominal aorta (AO) by an echotracking technique in 34 patients with mild to moderate congestive heart failure under diuretic, digitalis and ace-inhibitors treatment.
Results AO Dist correlated with the E/A or Dec time obtained by an echocolordoppler examination ( r 0.62 and – 0.42, respectively, p <0.02) while showing an inverse relationship with the V O2 max obtained by cardiopulmonary stress test ( r −0.47, p <0.01) and with the plasma concentration of aldosterone ( r 0.39, p <0.04). Similar findings were obtained for CA Dist.
Conclusions Thus the arterial stiffening increases with the heart failure severity and shows a parallelism with the reduced ability of the heart to relax in response to transmural pressure. The increased plasma levels of aldosterone (even in patients under ace-inhibitor) may play a role in this alteration of arterial mechanical properties.
13 citations
"A PC based system for non-invasive ..." refers background in this paper
...It is well established that the carotid artery serves as an indicator to the overall health of the cardiovascular system [1]....
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14 Oct 2008
TL;DR: The instrument gives a display of the variation of carotid diameter in real time and calculates the various estimates of arterial compliance from the analyzed data.
Abstract: A new virtual instrument for real time, non invasive measurement of carotid artery compliance is proposed. The instrument is a reliable, compact and low cost alternative to the conventional ultrasound scanner and wall tracking system for carotid artery compliance measurement. The measurement system uses an ultrasound pulse echo method to probe the carotid artery. The reflected echoes are processed using Hilbert transform techniques. Peak detection and echo tracking are implemented in LabVIEW. A comparison is done between manual and automatic method of echo identification. The instrument gives a display of the variation of carotid diameter in real time and calculates the various estimates of arterial compliance from the analyzed data. The capability of the instrument to accurately determine arterial compliance measures is demonstrated by experiments performed on human subjects.
12 citations
"A PC based system for non-invasive ..." refers background or methods in this paper
...We have already demonstrated a non-invasive system for carotid artery compliance measurement, based on a commercial pulser receiver, using a single transducer element [2]....
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...diastolic blood pressure values are fed into the virtual instrument to calculate the various arterial compliance parameters [2]....
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...These are then used to calculate the various measures of carotid artery compliance such as elastic modulus, arterial distensibility, compliance and stiffness index [2, 3]....
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...A detailed explanation of the signal processing chain has been given elsewhere [2]....
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