Staff

Abstract:
Background. Blood flow-mediated dilation (FMD) is a noninvasive assessment of vascular endothelial function in humans. The study of the FMD in hypertensive (HT) patients is an important factor supporting the recognition of the early mechanisms of cardiovascular pathologies, and also of the pathogenesis related to hypertension. Objectives. To investigate whether FMD measured on the radial artery (FMD-RA) using high-requency ultrasounds can be used asan alternative to FMD assessed with the lower frequency system onthe brachial artery in patients with HT. Materials and methods. The simultaneous measurements of FMD-RA and FMD measurements in the brachial artery (FMD-BA) were performed on 76 HT patients using 20 MHz and 7–12 MHz linear array probes, and were compared to the FMD measured in healthy groups. All quantitative data are presented as mean ± standard deviation (SD); the p-values of the normality and tests for variables comparisons are listed. The agreement of the FMD-RA and FMD-BA in HT patients was assessed with the Bland–Altman method, and using the intraclass correlation coefficient (ICC). In some statistical calculations, the FMD-RA values were rescaled by dividing them by a factor of 2. Results. The mean FMD-RA and FMD-BA in HT patients were 5.16 ±2.18% (95% confidence interval (95% CI): [4.50%, 5.82%]) and 2.13 ±1.12% (95% CI: [1.76%, 2.49%]), respectively. The FMD-RA and FMD-BA values of HT patients were significantly different than those in respective control groups. The p-values of Mann–Whitney–Wilcoxon tests were less than 0.05. The Bland–Altman coefficient for both measurement methods, FMD-RA and FMD-BA, was 3%, and the ICC was 0.69. Conclusions. Our findings show that FMD-RA, supplementary to FMD-BA measurements, can be used to assess endothelial dysfunction in the group of HT patients. In addition, the FMD-RA measurements met the criteria of high concordance with the FMD-BA measurements.

Keywords:
hypertension, brachial artery, radial artery, endothelial function

Abstract:
The article presents a new normalization of flow-mediated dilation (FMD) in the radial artery, taking into account the parameter BSSR being equal to the ratio of the basal shear rate (BS) measured before the cuff inflation and post occlusive shear rate (SR). The in vivo usefulness of the new normalization algorithm wasevaluated in two groups of patients. In group I, comprising 15 healthy volunteers, the normalized FMD/SR was(3.19 ± 1.4)*10^-4, while in group II, comprising 13 patients with stable coronary artery disease (CAD), it was(1.02 ± 0.76)*10^-4. We calculated almost 50% larger difference between the average values after normalizing FMD/BSSR. Specifically, the FMD/BSSR was equal to 28 ± 9.40 in group I and 6.01 ± 3.74 in group II. The prediction of CAD patients based on FMD/SR values had a sensitivity of 83.3% and a specificity of 84.6%, whereas the prediction of CAD patients based on the FMD/BSSR values revealed 100% sensitivity and specificity. These results confirm the usefulness of the novel normalization algorithm of the FMD in differentiation of normal patients from those with stable CAD.

Keywords:
flow-mediated vasodilation, radial artery, shear rate, pulsed Doppler, ultrasonography, coronary artery disease

Abstract:
In the article we describe the new, high frequency, 20 MHz scanning/Doppler probe designed to measure the flow mediated dilation (FMD) and shear rate (SR) close to the radial artery wall. We compare two US scanning systems, standard vascular modality working below 12 MHz and high frequency 20 MHz system designed for FMD and SR measurements. Axial resolutions of both systems were compared by imaging of two closely spaced food plastic foils immersed in water and by measuring systolic/diastolic diameter changes in the radial artery. The sensitivities of Doppler modalities were also determined. The diagnostic potential of a high frequency system in measurements of FMD and SR was studied in vivo, in two groups of subjects, 12 healthy volunteers and 14 patients with stable coronary artery disease (CAD). Over three times better axial resolution was demonstrated for a high frequency system. Also, the sensitivity of the external single transducer 20 MHz pulse Doppler proved to be over 20 dB better (in terms of a signal-to-noise ratio) than the pulse Doppler incorporated into the linear array. Statistically significant differences in FMD and FMD/SR values for healthy volunteers and CAD patients were confirmed, p-values < 0:05. The areas under Receiver Operating Characteristic (ROC) curves for FMD and FMD/SR for the prediction CAD had the values of 0.99 and 0.97, respectively. These results justify the usefulness of the designed high-frequency scanning system to determine the FMD and SR in the radial artery as predictors of coronary arterial disease.

Keywords:
low mediated dilation, shear rate, axial resolution, elevation resolution, pulsed Doppler, ultrasonic imaging

Abstract:
A high-frequency scanning system consisting of a 20-MHz linear array transducer combined with a 20-MHz pulsed Dopplerprobe was introduced to evaluate the degree of radial artery flow-mediated dilation (FMD [%]) in two groups of patients after5 min of controlled forearm ischemia followed by reactive hyperemia. In group I, comprising 27 healthy volunteers, FMD (mean ± standard deviation) was 15.26 ± 4.90% (95% confidence interval [CI]: 13.32%–17.20%); in group II, comprising 17 patients with chronic coronary artery disease, FMD was significantly less at 4.53 ± 4.11% (95% CI: 2.42%–6.64%). Specifically, the ratio FMD/SR (mean ± standard deviation),wasequalto5.36×10−4±4.64×10−4 (95%CI:3.54×10−4 to7.18×10−4)ingroupIand1.38×10−4±0.89×10−4 (95% CI: 0.70 × 10−4 to 2.06 × 10−4) in group II. Statistically significant differences between the two groups were confirmed by a Wilcoxon–Mann–Whitney test for both FMD and FMD/SR (p < 0.01). Areas under receiver operating characteristic curves for FMD and FMD/SR were greater than 0.9. The results confirm the usefulness of the proposed measurements of radial artery FMD and SR in differentiation of normal patients from those with chronic coronary artery disease. (E-mail: ) © 2018 World Federation for Ultrasound in Medicine & Biology. All rights reserved.

Keywords:
Flow-mediated vasodilation, Radial artery, Shear rate, Reactive hyperemia, Endothelium, Pulsed doppler, Ultrasonography

Abstract:
Background:
There is a growing interest in the application of non-invasive clinical tools allowing one to assess the endothelial function, preceding atherosclerosis. The precision in estimating of the artery Flow Mediated Vasodilation (FMD) using standard 10-12 MHz linear array probes does not exceed 0.2 mm, far beyond that required.

Methods:
We have introduced a wide-band, high frequency 25-30 MHz, Golay encoded wobbling type imaging to measure dilation of the radial artery instead of the brachial one. 18 young volunteers, and 4 volunteers with cardiac events history, were examined. In the second approach 20 MHz linear scanning combined with 20 MHz pulsed Doppler attached to the linear array was used. The radial artery FMD was normalized using shear rate at the radial artery wall.

Results and Conclusions:
For the “healthy” group, the FMD resulting from reactive hyperemia response was over 20%; while in the “atherosclerotic” group, the FMD was at least twice as small, not exceeding 10%. The shear rate (SR) normalized FMDSR was in the range from 7.8 to 9.9 in arbitrary units, while in patients with minor cardiac history FMDSR was clearly lower, 6.8 to 7.6. The normalized FMDSR of radial artery RARR can be an alternative to the brachial FMD where the precision of measurements is lower and the diameter dilation does not exceed 7-10%.

Keywords:
thick film transducers, atherosclerosis, flow mediated vasodilation

Abstract:
The main aim of this study was to verify the suitability of the hydrogel sonographic model of the left ventricle (LV) in the computed tomography (CT) environment and echocardiography and compare the radial strain calculations obtained by two different techniques: the speckle tracking ultrasonography and the multislices computed tomography (MSCT). The measurement setup consists of the LV model immersed in a cylindrical tank filled with water, hydraulic pump, the ultrasound scanner, hydraulic pump controller, pressure measurement system of water inside the LV model, and iMac workstation. The phantom was scanned using a 3.5 MHz Artida Toshiba ultrasound scanner unit at two angle positions: 0° and 25°. In this work a new method of assessment of RF speckles’ tracking. LV phantom was also examined using the CT 750 HD 64-slice MSCT machine (GE Healthcare). The results showed that the radial strain (RS) was independent on the insonifying angle or the pump rate. The results showed a very good agreement, at the level of 0.9%, in the radial strain assessment between the ultrasound M-mode technique and multislice CT examination. The study indicates the usefulness of the ultrasonographic LV model in the CT technique. The presented ultrasonographic LV phantom may be used to analyze left ventricle wall strains in physiological as well as pathological conditions. CT, ultrasound M-mode techniques, and author's speckle tracking algorithm, can be used as reference methods in conducting comparative studies using ultrasound scanners of various manufacturers.

Keywords:
Computed tomography, Echocardiography, Left ventricle, Speckles tracking, Strain, Ultrasound phantoms

Abstract:
The present work concerns the sonographic model of the left ventricle (LV) examined in the Computed Tomography (CT) environment and compare radial strain calculations obtained by two different techniques: the speckle tracking ultrasonography and the Multislices Computed Tomography (MSCT). The Left Ventricular (LF) phantom was fabricated from 10% solution of the poly(vinyl alcohol) (PVA). Our model of the LV was driven by the computer- controlled hydraulic piston Super -Pump (Vivitro Inc., Canada) with adjustable fluid volumes. The stroke volume was set at of 24ml. The fluid pressure was changed within range of 0- 60 mmHg, and the pulse rate was of 60 cycles/per minute. The relationships between computer controlled left ventricular wall deformations and its visual izations of the echocardiographic and CT imaging, both in the normal and pathological conditions were examined. The difference of assessment the Radial Strain between two methods was not exceeding 1.1%.

Abstract:
Two different tissue phantoms of the left ventricle to imitate a beating left ventricle were developed: first was prepared using a sponge material and second phantom was constructed using a polyvinyl alcohol material modeled into a homogeneous hollow cylinder: approximately 10 cm and 12 cm in length for the first and second phantom, respectively. Both phantoms were 5 cm in diameter, with a wall thickness of 1.0 cm. Additionally, a small part of the wall of the second phantom was processed to simulate the stiffness of myocardial infarction. The phantoms were connected at the end to an adjustable external pump. The pulse volume inside the cylinder was set between 12 to 50 ml at rates of 40, 60, 100, 120 beats/minute. The phantoms were immersed in water for ultrasound scanning with two different insonation angles (90 and 65 degrees). Strain and strain rate were measured with different combinations of angles and pulse rates. The main aim of this work was to develop the new method for validation of the human infarct wall strain calculation procedures using the speckles tracking.

Keywords:
soft tissue, phantom, ultrasound

Abstract:
The purpose of this work was to evaluate ultrasound modality as a non-invasive tool for determination of impact of the degree of the atherosclerotic plaque located in human internal carotid arteries on the values of the parameters of the pulse wave. Specifically, the applicability of the method to such arteries as brachial, common, and internal carotid was examined. The method developed is based on analysis of two characteristic parameters: the value of the mean reflection coefficient modulus |Γ|a of the blood pressure wave and time delay Δt between the forward (travelling) and backward (reflected) blood pressure waves. The blood pressure wave was determined from ultrasound measurements of the artery’s inner (internal) diameter, using the custom made wall tracking system (WTS) operating at 6.75 MHz. Clinical data were obtained from the carotid arteries measurements of 70 human subjects. These included the control group of 30 healthy individuals along with the patients diagnosed with the stenosis of the internal carotid artery (ICA) ranging from 20% to 99% or with the ICA occlusion. The results indicate that with increasing level of stenosis of the ICA the value of the mean reflection coefficient measured in the common carotid artery, significantly increases from |Γ|a = 0.45 for healthy individuals to |Γ|a = 0.61 for patients with stenosis level of 90–99%, or ICA occlusion. Similarly, the time delay Δt decreases from 52 ms to 25 ms for the respective groups. The method described holds promise that it might be clinically useful as a non-invasive tool for localization of distal severe artery narrowing, which can assist in identifying early stages of atherosclerosis especially in regions, which are inaccessible for the ultrasound probe (e.g. carotid sinus or middle cerebral artery).

Keywords:
Pulse wave, Ultrasound, Vascular impedance, Stenosis

Abstract:
The main objective of this study is to develop an echocardiographic model of the left ventricular and numerical modeling of the speckles- markers tracking in the ultrasound (ultrasonographic) imaging of the left ventricle. The work is aimed at the creation of controlled and mobile environment that enables to examine the relationships between left ventricular wall deformations and visualizations of these states in the form of echocardiographic imaging and relations between the dynamically changing distributions of tissue markers of studied structures.

Keywords:
left ventricle, echocardiography, speckle modeling, ultrasound phantoms, strain, strain rate

Abstract:
The aim of this paper is to describe a non-invasive method of examination of the local pulse wave velocity. The measurements were carried out in the model of the artery immersed in a water tank. Two synchronized ultrasonic apparatus VED with the ultrasonic radio frequency echoes acquisition system were used for evaluation of the arterial elasticity. The zero-crossing method was used for determination of the diameter changes of the artery model. The transit time between the waveforms of instant artery diameter was measured at two points of the artery model, separated by the distance of 5 cm. The transit time was determined using the criteria of similarity of the first derivatives of the raising slopes of the curves describing instant vessel's diameter changes. The pulse wave velocity obtained by the proposed two-point method was compared with the results obtained by the one-point method based on the modified Bramwell-Hill relation.

Keywords:
ultrasound, local pulse wave velocity, model of artery

Abstract:
The aim of this paper is to present the new method for relative changes measurements of intima-media thickness in the common carotid artery wall. The numerical solver was created for calculation of the fields of ultrasonic beams and scattered fields under different boundary conditions and different angles of penetration of ultrasonic beams with respect to the position of the arterial wall. The cylindrical model of the artery was changing the radius and thickness of the wall under cyclic variation of blood pressure. The presented method was verified on a pipe made of latex. The paper describes also the initial results of examinations of the intima-media thickness. The good agreement for the angle dependence and the perpendicular ultrasonic beam displacement from the longitudinal axis of the artery segment between the numerical calculation and experimental results was obtained for different artery diameters.

Abstract:
The aim of this paper is to compare the results of the mathematical modeling and experimental results of the ultrasonic waves scattering in the inhomogeneous dissipative medium. The research was carried out for an artery model (a pipe made of a latex), with internal diameter of 5 mm and wall thickness of 1.25 mm. The numerical solver was created for calculation of the fields of ultrasonic beams and scattered fields under different boundary conditions, different angles and transversal displacement of ultrasonic beams with respect to the position of the arterial wall. The investigations employed the VED ultrasonic apparatus. The good agreement between the numerical calculation and experimental results was obtained.

Keywords:
Model of the artery, scattering, numerical solver

Abstract:
The aim of this paper is to describe a non-invasive method of examination of the local pulse wave velocity. The measurements were carried out in the elastic silicon model of the artery immersed in water tank. Two synchronized ultrasonic apparatus VED with the ultrasonic radio frequency echoes acquisition for evaluation of the arterial elasticity, developed by the author, were used. The zerocrossing method was used for evaluating the pulse wave by measurements of the diameter changes of the model of the artery. The transit time between the waveforms of instant artery diameter at two measurement points, 5cm along the model of the artery was measured. The transit time was determined using the criteria of similarity of the first derivatives of the raising slopes of curves describing the instant vessel’s diameter changes in two measurement points of the model of the artery. The pulse wave velocity obtained by proposed two-point method was referred to the one-point method based of the modified Bramwell-Hill relation.

Keywords:
ultrasound, local pulse wave velocity, model of artery

Abstract:
The aim of this paper is to compare the results of examinations of the intima-media thickness (IMT) in the wall of the carotid artery model by means of zero-crossing and correlation methods. The research was carried out on the elastic artery model (a pipe made of latex), with the internal diameter of 3, 5 and 8 mm and the wall thickness of 0.75, 1.25 and 2 mm. A numerical solver was created for the purpose of calculating the fields of ultrasonic beams and scattered fields under different boundary conditions, different angles and transversal displacements of ultrasonic beams in respect of the position of the arterial wall. A VED ultrasonic apparatus was used during the investigations. The frequency of the transmitted ultrasound was 6.75 MHz. The numerical solver was used for the creation of ultrasonic RF reference signals. A good conformity was obtained between changing the numerical reference of the IMT and the results of determining the IMT by both the zero-crossing method and the correlation method.

Keywords:
ultrasound, carotid artery, intima-media thickness, numerical model

Abstract:
The aim of this paper is to compare the results of the mathematical modeling and experimental results of the ultrasonic waves scattering in the inhomogeneous dissipative medium. The research was carried out for an artery model (a pipe made of a latex), with internal diameter of 3, 5 and 8 mm and wall thickness of 0.75, 1.25 and 2 mm. The numerical solver was created for calculation of the fields of ultrasonic beams and scattered fields under different boundary conditions, different angles and transversal displacement of ultrasonic beams with respect to the position of the arterial wall. The investigations employed the VED ultrasonic apparatus. The frequency of the transmitted ultrasound was 6.75 MHz. The good agreement between the numerical calculation and experimental results was obtained. The numerical solver is used for verified proposed methods for determining of the IMT in the artery walls.

Keywords:
ultrasound, scatering, artery model, numerical calculations, eksperimental results, Comparison

Abstract:
This paper presents results of examinations of the intima-media thickness (IMT) in human common carotid arteries. Ultrasonic examinations were carried out on healthy volunteers with the use of the apparatus Vascular Echo Doppler (VED), designed in IFTR-PAS to measure the elasticity of arteries. Application of the PDA-14 PC-card (Signatec) allowed for the acquisition of ultrasonic RF signal from the output of the apparatus VED and for further analysis of dynamic changes of the IMT during a heart cycle. Changing of the IMT in time as a difference between the instantaneous position of the two tracking slopes of RF echoes was obtained. For this purpose the zero-crossing method, for tracking phase changes of two characteristic rising slopes of the RF ultrasonic echo, was used.

Abstract:
The developed solver of acoustic field was used for simulation of the artery wall thickness examination. It is capable of describing spatial and time-dependent distribution of an ultrasonic beam, that is emitted by a piezoelectric ring transducer and then backscattered on cylindrical surfaces of the walls in artery models. The electrical signal received corresponds closely with the actual RF signal that is obtained during measurements at the output of the ultrasonicVED apparatus. The theoretical model of the artery for creating the ultrasonic reflected echoes was used. The internal radius of the artery model was 3mm for the diastolic pressure and 3.3mm for the systolic pressure. The intima- media thicknes (IMT) of the artery wall was changed from 0.48mm to 0.44mm respectively. The echoes-tracking solver based on the zero-crossing and correlation methods was used for detecting changes of the IMT.

Keywords:
ultrasound, common carotid artery, elasticity, intima-media thickness, numerical solver

Abstract:
The paper describes the initial results of examinations of the intima-media thickness (IMT) in the common carotid artery wall. The examinations of the IMT enable the assessment of elastic properties of the arterial wall. Ultrasonic examinations were carried out on healthy volunteers with the use the apparatus Vascular Echo Doppler (VED), designed by the authors to measure the elasticity of arteries. Application of the PDA-14 PC-card (Signatec) allowed for the acquisition of ultrasonic RF signal from the output of the apparatus VED and further analysis of dynamic changes of the IMT during a heart cycle. Changing of the IMT in time as a difference between the instantaneous position of the two tracking slopes of RF echoes was obtained. For this purpose, the zero-crossing method for tracking the phase changes of the two rising slopes of the RF ultrasonic echo was used.

Keywords:
ultrasound, common carotid artery, elasticity, intima-media thickness

Abstract:
The aim of the study was the elaboration of a mathematical model to describe the process of acoustic wave propagation, generated by an ultrasonic probe in a inhomogenous loosing medium. Numerical calculations make it possible to define waveforms for electric signals that are generated when ultrasonic waves, being reflected and backscattered by an artery model, are then received by the ultrasonic probe. It is the signal that pretty well corresponds with the actual RF signal that is obtained during measurements at the output of anultrasonic apparatus. The developed solver of acoustic field was used for simulation of the artery wall tickness examination. The theoretical model of the atrery for the creating the simulated ultrasonic reflected echoes was used. The internal radiusof the artery model was 3mm for the diastolic pressure and and 3.3mm for the systolic pressure. The intima-media thicknes (IMT) of the artery wall was changed from o.48 to 0.44 respectively. The solver based on zero-crossing method was used for detecting changes of the IMT.

Keywords:
ultrasound, mathematical model, scatering, inhomogenous loosing medium, numerical simulations, intima-media changes

Abstract:
The study was aimed at elaboration of a mathematical model to describe the process of acoustic wave propagation in an inhomogeneous and absorbing medium, whereas the wave is generated by an ultrasonic probe. The modelling proces covered the phenomenon of ultrasonic wave backscattering on an elastic pipe with dimensions similar to the artery section. Later on the numerical codes were determined in order to calculate the fields of ultrasonic waves, as well as backscattered fields for various boundary conditions. Numerical calculations make it possible to definethe waveforms for electric signals that are produced when ultrasonic waves, being reflected and backsvattered by an artery model, are then received by the ultrasonic probe. It is the signalwhich pretty well corresponds with the actual RF signal that is obtained during measurements at the output of anultrasonic apparatus.

Keywords:
ultrasound, backscattering, artery, numerical model

Abstract:
The paper describes the initial results of numeric analysis of plane-strain of a model of the human common carotid artery. The results of computer modeling were compared with the experimental data obtained by means of ultrasonic measurements of the changes in the thickness of the common carotid artery wall. The ultrasonic examination was carried out on a 34 years old healthy male using the VED apparatus designed by the authors to measure the elasticity of arteries. The numeric analysis was made by means of the finite element method (FEM) using the MARC K7 programming of the Analysis Research Corporation based on the operating system UNIX. As a model of the common carotid artery the authors used a hollow cylinder made of the isotropic, homogeneous, almost incompressible material (Poisson’s constant ν=0.4999) having the Young’s module E=159.2 kPa and the combined thickness of the internal and middle layer IMT = 0.52 mm. The modeling of plane-strain concerned the effect of the change in the internal radius and the change in the cylinder wall thickness as a result of the static change of pressure inside the cylinder within the values of 0–45 mmHg. The study obtained satisfactory results in the computer simulation of the changes in the artery walls thickness.

Keywords:
ultrasound, elasticity of the common carotid artery wall, wall thickness

Abstract:
The article attempts to select an ultrasound system to assess of endothelium dysfunction-dependent flow mediated dilation (FMD) and shear rate (SR) in radial artery after several minutes of hyperaemia. Methods: We compare the effective axial resolution and Doppler sensitivity of the standard US working below 12 MHz and high frequency (close to 20 MHz) scanning systems measuring the vessel diameter and blood flow measurements in radial arteries. FMD and FMD and SR were measured in Control group of 14 healthy volunteers, and in 13 with stable coronary artery diseases (CAD). Results: In a laboratory experiment of imaging two closely spaced food plastic foils, over three times better axial resolution was demonstrated for the 20 MHz ultrasound system in which the resolution was close to 0.1 mm. Also the sensitivity of the external single 20 MHz pulse Doppler transducer proved to be over 20 dB better (in terms of signalto-noise ratio) than the pulse Doppler incorporated into the L14-5 linear array. FMD in Control group was in the range of 8÷16% with mean±sd equal to 12.13 ± 2.34%; in CAD group FMD was in the range of 0.1÷7 % with mean±sd equal to 3.01±2.18% which was significantly less. FMD/SR was equal to 3.08 ± 1.34 × 10–4 in Control group and 1.01 ± 0.76 × 10–4 in CAD group with ranges equal to 1.66 ÷ 7.8× 10–4 and 0.4 ÷ 2.4× 10–4, respectively. Conclusions: Increasing scanning and Doppler mode frequency to 20 MHz improved the precision of FMD and SR measurements. Statistically significant differences between the two groups were confirmed by statistical tests for FMD and FMD/SR with p-values < 0.05. The results obtained suggest the usefulness of the proposed ultrasonic system for measurements of FMD and SR in the radial artery to differentiate normal subjects from those with CAD.

Keywords:
radial artery, shear rate, reactive hyperaemia, endothelium, pulsed Doppler

Abstract:
A novel high-frequency scanning system, with a 20-MHz linear array transducer combined with 20-MHz pulsed Doppler, was introduced to evaluate the degree of radial artery flow-mediated dilation (FMD) and shear rate (SR)-normalized FMD (FMD/SR) after 5 min of reactive hyperaemia. In group I, comprising 27 healthy volunteers, FMD was 15 ± 4.8%, and in group II, comprising 17 patients with coronary artery disease, FMD was significantly smaller, being equal to 4.6 ± 4%. FMD/SR was equal to 5.365 ± 4.835·10-4 in group I and 1.3 ± 0.89·10-4 in group II. Statistically significant differences between the two groups were confirmed by Wilcoxon-Mann-Whitney test for FMD and FMD/SR (p-values < 0.01). AUCs of ROC curves for FMD and FMD/SR were greater than 0.9. The results confirm the usefulness of the proposed measurements of radial artery FMD and SR in differentiation of normal subjects from those with atherosclerotic lesions.

Keywords:
flow mediated vasodilation, radial artery, shear rate, reactive hyporaemia, endothelium, pulsed Doppler, ultrasonography.

Abstract:
Preceding atherosclerosis is endothelial dysfunction. There is therefore interest in the application of non-invasive clinical tools to assess endothelial function. There are commercially available ultrasound scanners to estimate Brachial Artery Reactive Response BARR by measuring the flow-mediated vasodilatation (FMD) of the brachial artery using 10–12 MHz linear array probes; however the precision in estimating of artery dilation does not exceeds 0.2 mm, far beyond the required one. We have introduced a high frequency scanning schemes; 25–35 MHz encoded (Golay) wobbling type imaging with- out Doppler (uScan developed in our lab, thick film wide bandwidth transducer, 50 microns axial resolution). In the second approach we have used 20 MHz linear scanning with 20 MHz pulsed Doppler attached to the linear array. Instead of brachial artery we have examined the radial artery where Radial Artery Reactive Response RARR was measured. The radial artery FMD were normalized using AUC of shear rate at the radial artery wall. The precision of the radial artery diameter measurements is over two times better using 20 MHz US instead of 7.5 MHz used for brachial artery FMD. The measured initial internal radial artery diameter was in range of 1.59–2.35 mm, the maximum diameter 2.01–2.60 mm was observed 40 to 55 seconds after releasing the cuff. In a limited number (14) of examined young, healthy patients the FMDSR were in the range from 7.8
to 9.9 in arbitrary units. In older patients with minor cardiac history the normalized FMDSR was clearly lower, 6.8 to 7.6.

Keywords:
thick film transducers, atherosclerosis, flow mediated vasodilation.

Abstract:
Preceding atherosclerosis is endothelial dysfunction. There is therefore interest in the application of non-invasive clinical tools to assess endothelial function. There are commercially available ultrasound scanners to measure flow-mediated vasodilatation (FMD) of the brachial artery using 10-12 MHz linear array probes, however the attainable precision in estimating the changes in artery dilation does not exceeds 0.2 mm, far beyond the required one. We have introduced a high frequency scanning schemes 25-35MHz encoded (Golay) wobbling type imaging without Doppler (uScan developed in our lab, thick film wide bandwidth transducer, 50 microns axial resolution) and 20 MHz ultrasound (Ultrasonix) with 20 MHz pulsed Doppler attached to the linear array. The FMD results were normalized using AUC of shear rate at the radial artery wall.

Keywords:
thick-film transducers, flow-mediated vasolidation, radial artery, shear rate

Abstract:
The main goal of this study was to verify the suitability of sonographic model of the left ventricle (LV) in Computed Tomography (CT) environment and compare radial strain calculations obtained by two different techniques: speckle tracking ultrasonography and Multislices Computed Tomography (MSCT). The Left Ventricular (LF) phantom was fabricate from 10% solution of the poly(vinyl alcohol) (PVA). Our model of the LV was driven by the computer-controlled hydraulic piston Super-Pump (Vivitro Inc., Canada) with adjustable fluid volumes. During cycle of the pump, the Stroke Volume (SV) of water was pumped into the LV phantom and returned to the pump, resulting in changing the inner and outer diameters of the phantom. The stroke volume was set at of 24ml. The fluid pressure was changed within range of 0-60 mmHg, and the pulse rate was equal 60 cycles/per minute. The relationships between computer controlled left ventricular wall deformations and its visualizations of the echocardiographic and CT imaging, both in the normal and pathological conditions were examined. The difference of assessment the Radial Strain between two methods was not exceeding 1.1%.

Abstract:
Les mesures ont été effectuées dans le modèle de l'artère immergée dans un réservoir d'eau. Les deux appareils ultrasonores synchronisés, appelés Vasculaire Écho Doppler (VED), développé par l'auteur, ont été employés pour l'acquisition ultrasonore d'échos de la radiofréquence (RF). L’onde pulsatile artérielle a été déterminée par la mesure ultrasonore non envahissante du diamètre interne artérielle sur la base sur la méthode de passage à zéro. La vitesse d’onde pulsatile artérielle a été déterminée par la mesure de temps de passage de l’onde d'impulsion entre deux points de mesure séparés par la distance de 5cm le long de la section du modèle de l'artère. Le temps de passage a été déterminé en utilisant les critères de la similitude de la première des dérivés des pentes augmentant des courbes décrivant les changements dans le diamètre des vaisseaux sanguins. La vitesse de vague d'impulsion obtenue par la méthode proposée de deux-points a été comparée aux résultats obtenus par la méthode d'un-point basée sur la relation modifiée de Bramwell-Hill.

Abstract:
The input vascular impedance was determined using ultrasound continuous wave Doppler flow meter and a system for tracking arterial wall movements. The study was conducted in a control group (30 volunteers) and in four groups (10 patients in each group). Patients were grouped according to the criteria ofatherosclerotic stage, which was the degree of arterial stenosis: 20–49%, 50–69%, 70–89%, and 90–99% and occlusion, based on ultrasound or duplex tests. The results of Student's t-test showed the statistically significance of the sparation of longitudinal resistance Ro results from the control group and sequentially four groups with a defined degree of atherosclerotic carotid artery at a 95% confidence level with significance level from p < 5.2E−3 for 20–49% - for the receiver operating curve (ROC), the area under curve (AUC) = 0.76; p < 8.6E−9 for the stenosis 50-69% - for the ROC curve AUC = 0.913, p < 6.3E−9 for the stenosis 70–89% for ROC curve AUC = 0.94, to p < 8.1E−10 for stenosis above 90% and occlusion, for ROC curve AUC = 0.97. After combining data for patients with internal carotid artery stenosis from 50–89% the results of Student's t-test showed the statistical significance of the separation of the longitudinal resistance results Ro derived from the control group and the combined group with a confidence level of 95% at significance level p < 2.8E−10, for ROC curve AUC = 0.942.

Keywords:
Vascular input impedance, common carotid artery, ultrasound.

Abstract:
The aim of this study was to verify suitability of sonographic model of LV (left ventricle) in CT (computed tomography) environment and to compare in vitro radial strain calculations obtained by two different techniques: speckle tracking ultrasonography and multislice CT.