Threshold Setting for Likelihood Function for Elasticity-Based Tissue Classification of Arterial Walls by Evaluating Variance in Measurement of Radial Strain

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Red blood cell (RBC) aggregation, as one of the determinants of blood viscosity, plays an important role in blood rheology, including the condition of blood. RBC aggregation is induced by the adhesion of RBCs when the electrostatic repulsion between RBCs weakens owing to increases in protein and saturated fatty acid levels in blood, excessive RBC aggregation leads to various circulatory diseases. This study was conducted to establish a noninvasive quantitative method for assessment of RBC aggregation. The power spectrum of ultrasonic RF echoes from nonaggregating RBCs, which shows the frequency property of scattering, exhibits Rayleigh behavior. On the other hand, ultrasonic RF echoes from aggregating RBCs contain the components of reflection, which have no frequency dependence. By dividing the measured power spectrum of echoes from RBCs in the lumen by that of echoes from a posterior wall of the vein in the dorsum manus, the attenuation property of the propagating medium and the frequency responses of transmitting and receiving transducers are removed from the former spectrum. RBC aggregation was assessed by the diameter of a scatterer, which was estimated by minimizing the square difference between the measured normalized power spectrum and the theoretical power spectrum. In this study, spherical scatterers with diameters of 5, 11, 15, and 30 m were measured in basic experiments. The estimated scatterer diameters were close to the actual diameters. Furthermore, the transient change of the scatterer diameters were measured in an in vivo experiment with respect to a 24-year-old healthy male during the avascularization using a cuff. The estimated diameters (12-22 m) of RBCs during avascularization were larger than the diameters (4-8 m) at rest and after recirculation. These results show the possibility of the use of the proposed method for noninvasive assessment of RBC aggregation.

Section: Discussionmentioning

confidence: 99%

Section: Basic Experiments Using Microspheresmentioning

confidence: 99%

Estimation of Scatterer Diameter by Normalized Power Spectrum of High-Frequency Ultrasonic RF Echo for Assessment of Red Blood Cell Aggregation

Fukushima

Hasegawa

Kanai

2011

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“…Scattering [359][360][361][362][363][364] Ultrasonic transducers (piezoelectric effect) and its attachments [375][376][377][378][379][380][381] Acoustic field measurement and control [382][383][384][385][386] Blood flow measurement [394][395][396][397] Tissue characterization Velocity [125][126][127][128][129][130][131][132][133][134][406][407][408]420,422) Displacement 409,413,425) Thickness 399,418) Viscoelasticity 398,[401][402][403][404][405][410]…”

Section: General Topicmentioning

confidence: 99%

Introduction of measurement techniques in ultrasonic electronics: Basic principles and recent trends

Mizutani¹,

Wakatsuki²,

Ebihara³

2016

Measurementthe act of measuring physical properties that we performhas the potential to contribute to the successful advancement of sciences and society. To open doors in physics and other sciences, various measurement methods and related applications have been developed, and ultrasound has remained a useful probe, power source, and interesting measurement object for the past two centuries. In this paper, we first summarize the basic principles of ultrasound from the viewpoint of measurement techniques for readers who just have started studying or are interested in the field of ultrasonic electronics. Moreover, we also introduce recent studiesultrasonic properties of materials, measurement techniques, piezoelectric devices, nonlinear acoustics, biomedical ultrasound, and ocean acousticsand their trends related to measurement techniques in ultrasonic electronics to provide some ideas for related applications.

“…The change in thickness, ÁĥðtÞ, between two different depths (LIB and MAB) was obtained from the difference between the displacementsx a andx b at the LIB and MAB: wherev a andv b are the velocities at the LIB and MAB, respectively. The phased-tracking method has been used in various applications, e.g., measurements of the motion and deformation of the arterial and heart walls [17][18][19] for evaluating the viscoelastic properties and the myocardial function, [20][21][22][23] and measuring viscoelastic properties with acoustic radiation force. 24,25) 2.2 Correction of change in propagation time delay of pulse wave PWV changes with some factors such as the elasticity and diameter of the artery, and the thickness of the arterial wall.…”

Section: Measurement Of Stress-strain Relationshipmentioning

confidence: 99%

Correction of change in propagation time delay of pulse wave during flow-mediated dilation in ultrasonic measurement of arterial wall viscoelasticity

Sato

Hasegawa

Kanai

2014

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It is considered that the endothelial dysfunction occurs in the initial step of atherosclerosis. Although assessments of the endothelial function and viscoelastic properties of the intima-media region are important for the diagnosis of early-stage atherosclerosis, regional viscoelasticity has not yet been measured in vivo. Our group has developed an ultrasonic method for measuring the transient change in viscoelasticity during flow-mediated dilation (FMD). However, in this method, the stress (blood pressure) and strain of the intima-media region of the radial artery are measured in different arms, and the change in pulse wave velocity (PWV) due to FMD has not yet been considered. In the present study, we measured blood pressure waveforms using two pressure sensors, which were placed along the same radial artery for the ultrasonic measurement, to obtain blood pressure waveforms and estimate the PWV between the two sensors. Using the measured PWV, the pulse wave propagation time from the pressure sensor to the position of the ultrasound probe was corrected, and viscoelasticity was estimated from the corrected stress-strain relationship. In the basic experiment, we applied the proposed method to a silicone tube phantom and evaluated the accuracy of the estimation of viscoelasticity by comparing the ultrasonic measurement to the results of the tensile test. In the in vivo measurements, the change in the propagation time delay of the pulse wave was also corrected using the two pressure sensors and the stress-strain relationship of the radial arterial wall was then obtained to estimate viscoelasticity. Furthermore, a decrease in elasticity owing to FMD after recirculation was clearly observed, and the unstable temporal variation in viscosity was significantly reduced. These results demonstrated the improvement in the accuracy of the measurement of viscoelasticity by the proposed method.