Mototaka Arakawa

Abstract To establish an evaluation index for vascular endothelial function, we developed an ultrasonic probe that can measure changes in blood pressure and blood vessel diameter at the same position in the radial artery. Based on phantom experiments, the pressure waveforms measured using the piezoelectric effect of the ultrasonic probe element and those using a pressure sensor exhibited a high correlation (correlation coefficient: r = 0.979 – 0.999). We confirmed the continuous measurement of t

Abstract Noninvasive measurement of the degree of red blood cell (RBC) aggregation is useful for evaluating blood properties. In the present paper, we proposed a method to estimate the size of RBC aggregates without using the power spectrum of the posterior wall by introducing a reference scattering spectrum. The reference power spectra were calculated using the power spectrum measured for an ultrafine wire with a hemispherical tip. They were applied to the size estimation of microparticles simu

We obtained an accurate relationship between the leaky surface acoustic wave (LSAW) velocities and TiO2 concentrations. Such a relationship is needed for the line-focus-beam ultrasonic material characterization (LFB-UMC) system as a new technology for evaluating the coefficient of thermal expansion (CTE) of ultra-low-expansion glasses with extremely high precision. Using commercially available TiO2–SiO2 glass with periodic striae, averaged velocities for LSAW propagation parallel to the striae p

Biomechanics of the cell has been gathering much attention because it affects the pathological status in atherosclerosis and cancer. In the present study, an ultrasound microscope system combined with optical microscope for characterization of a single cell with multiple ultrasound parameters was developed. The central frequency of the transducer was 375 MHz and the scan area was 80 × 80 μm with up to 200 × 200 sampling points. An inverted optical microscope was incorporated in the design of the

Abstract An estimation of anisotropic viscoelasticity is important for evaluating muscle lesions. In the previous study, we proposed a method for estimating viscoelasticity in a local region by exciting a phantom specimen from both directions. In the present study, we observed the acoustic field having the locality and directivity generated by dual ultrasound excitation. In addition, the displacement distributions for the isotropic and anisotropic viscoelastic phantoms were measured, and the loc

Abstract We developed a single ultrasound probe to simultaneously measure blood pressure and changes in the diameter of the radial artery to estimate the wall viscoelasticity during flow-mediated dilatation (FMD). This probe can be used for the early diagnosis of arteriosclerosis. This paper introduces the pulse transit time method to accurately measure changes in blood pressure during FMD. Using the single ultrasound probe and the proposed method, in vivo experiments involving three subjects we

Abstract The propagation of myocardial contraction caused by the conduction of electrical excitation in the heart has been visualized in our previous study. However, it was assumed that the contraction propagated parallel to the heart wall and the propagation speed was constant within the measurement area. In the present study, we estimated the two-dimensional propagation speed of contraction at each local area by ultrasonic measurement, and examined the mechanism of the contraction propagation