PurposeThe aim of this study was to introduce and implement a noninvasive method to derive the carotid artery pressure waveform directly by processing diagnostic sonograms of the carotid artery.MethodsUltrasound image sequences of 20 healthy male subjects (age, 36±9 years) were recorded during three cardiac cycles. The internal diameter and blood velocity waveforms were extracted from consecutive sonograms over the cardiac cycles by using custom analysis programs written in MATLAB. Finally, the application of a mathematical equation resulted in time changes of the arterial pressure. The resulting pressures were calibrated using the mean and the diastolic pressure of the radial artery.ResultsA good correlation was found between the mean carotid blood pressure obtained from the ultrasound image processing and the mean radial blood pressure obtained using a standard digital sphygmomanometer (R=0.91). The mean absolute difference between the carotid calibrated pulse pressures and those measured clinically was -1.333±6.548 mm Hg.ConclusionThe results of this study suggest that consecutive sonograms of the carotid artery can be used for estimating a blood pressure waveform. We believe that our results promote a noninvasive technique for clinical applications that overcomes the reproducibility problems of common carotid artery tonometry with technical and anatomical causes.

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Clarifying the complex interaction between mechanical and biological processes in healthy and diseased conditions requires constitutive models for arterial walls. In this study, a mathematical model for the displacement of the carotid artery wall in the longitudinal direction is defined providing a satisfactory representation of the axial stress applied to the arterial wall. The proposed model was applied to the carotid artery wall motion estimated from ultrasound image sequences of 10 healthy adults, and the axial stress waveform exerted on the artery wall was extracted. Consecutive ultrasonic images (30 frames per second) of the common carotid artery of 10 healthy subjects (age 44 ± 4 year) were recorded and transferred to a personal computer. Longitudinal displacement and acceleration were extracted from ultrasonic image processing using a block-matching algorithm. Furthermore, images were examined using a maximum gradient algorithm and time rate changes of the internal diameter and intima-media thickness were extracted. Finally, axial stress was estimated using an appropriate constitutive equation for thin-walled tubes. Performance of the proposed model was evaluated using goodness of fit between approximated and measured longitudinal displacement statistics. Values of goodness-of-fit statistics indicated high quality of fit for all investigated subjects with the mean adjusted R-square (0.86 ± 0.08) and root mean squared error (0.08 ± 0.04 mm). According to the results of the present study, maximum and minimum axial stresses exerted on the arterial wall are 1.7 ± 0.6 and -1.5 ± 0.5 kPa, respectively. These results reveal the potential of this technique to provide a new method to assess arterial stress from ultrasound images, overcoming the limitations of the finite element and other simulation techniques.

Cross-sectional area (CSA) measurement obtained from transverse ultrasound images is the general method used for carotid artery stenosis calculation which assumes a circular CS, however, atherosclerotic stenosis may change the CSA geometry and lead to miscalculation. This study aims to determine the accuracy of circular or elliptical approximation of the normal and stenosed carotid artery CSA. Sixty transverse B-mode ultrasound images (30 from healthy and 30 from stenosed carotid arteries) were recorded. Contours of the internal lumen of the arteries were segmented and the encompassed lumen area was calculated. Based on the fitting accuracy and computational cost effectiveness, pattern search (PS) optimization algorithm was selected by which the parameterized equations of the circular and elliptical geometries were fitted to the segmented point clouds. Goodness of fit analysis of two geometries was carried out using root mean square error (RMSE) and the relative deviation of the approximated CSA. Results of this study showed that elliptical approximation better fits to the artery CS of carotid arteries, with the average RMSE of [Formula: see text] and [Formula: see text] pixels in healthy and [Formula: see text] and [Formula: see text] pixels in stenosed carotid arteries, respectively, for circle and ellipse approximation. Mean values of the relative deviation of the approximated CSA by circle and ellipse geometries were 5.14%[Formula: see text]±[Formula: see text]4.53% and 3.89%[Formula: see text]±[Formula: see text]4.19% in normal arteries; and 12.18%[Formula: see text]±[Formula: see text]10.94% and 4.59%[Formula: see text]±[Formula: see text]3.75% in stenosed arteries, respectively. This study represented that elliptical approximation provides increased accuracy for carotid artery CSA for both normal and stenosed carotid arteries.

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