Preliminary study on estimation of flow velocity vectors using focused transmit beams

The properties of echoes and transmitted waves from a fish body, in megahertz bands, were investigated to construct a fish detection method in a narrow path by a simple measurement structure using a pair of transducers. Experiments were performed in a water tank using dead Japanese jack mackerel (Trachurus japonicus). From the echoes, the outlines of fish could be observed. High amplitudes of echoes from the swim bladder and fins were observed, while relatively low amplitudes of echoes were observed from other body parts, e.g., the head, body surface, and vertebral columns. From the transmitted waves, decreased amplitudes and times-of-flight in waves transmitted from the fish body were observed. The fish could be detected using ultrasound, in megahertz bands, and the combined use of the echo and transmitted waves could increase the information obtained about fish compared with the use of echoes only.

Section: Introductionmentioning

confidence: 99%

Detection of fish passing through a narrow path using reflected and transmitted ultrasonic waves

Miyamoto

Doi

Mizutani

et al. 2023

“…On the other hand, MLTI transmits two or more focused beams at the same time to obtain a B-mode image. 26) Therefore, the number of transmissions required to reconstruct one image can be reduced. However, undesired echoes caused by interference between the beams, i.e.…”

Section: Transmission Conditionmentioning

confidence: 99%

Investigation on vector Doppler method for carotid artery wall with focused transmit beams produced from a cross-shaped probe

Yano,

Fujisawa,

Omura

et al. 2024

Self Cite

Conventional methods for estimating 1D or 2D velocities were developed for the dynamic measurement of carotid walls. However, a carotid wall moves in 3D due to a heart pulsation, and the wall motion velocity in the longitudinal-axis cross-section is affected by out-of-plane displacements that cannot be measured with a 1D array probe. To estimate the out-of-plane displacement, we proposed the crossed-shape probe. The crossed-shape probe can estimate 3D velocity vector with 256 transmit-receive channels. Single or multiple focused beams were transmitted by the main array of the crossed-shape probe, and the RF signals received all the elements were used for 3D velocity vector estimation based on the multi-angle Doppler method. Numerical simulations and basic experiments showed that out-of-plane displacements in the longitudinal-axis cross section can be estimated. Furthermore, in vivo experiments on a human common carotid artery showed that arterial wall motion during a cardiac cycle can be measured.

“…[3][4][5][6][7] Although we recently examined the estimation of blood flow velocity vectors using focused transmit beams, the frame rate was significantly lower than that in plane wave imaging. 8) Therefore, high-frame-rate ultrasound imaging using non-focused transmit beams, such as plane waves and diverging waves, has been developed, 9,10) achieving an extremely high temporal resolution exceeding several thousand frames per second. The potential of high-frame-rate ultrasound in blood flow imaging was demonstrated, 11) and coherent plane wave compounding (CPWC) 12) based on the autocorrelation method, 2) which enables the acquisition of axial velocity distribution, was developed for quantitative blood flow imaging.…”

Section: Introductionmentioning

confidence: 99%

Effects of beam steering angle and excitation frequency on blood flow imaging with plane wave imaging

Maru,

Omura,

Nagaoka

et al. 2024

Self Cite

The vector Doppler method was developed to overcome a limitation of conventional methods, which can only estimate axial velocities. Since the vector Doppler method uses steered beams, the excitation frequency is set lower than the resonance frequency of transducer elements to prevent generation of grating lobes. Although lowering the steering angle is another solution, a larger steering angle span leads to more accurate estimation of velocity vectors. We have developed a method for estimating the steering angle from received echo signals, and the method might enable accurate estimation of velocity vectors even with small steering angles. In this study, effects of steering angle and excitation frequency were investigated by numerical simulation and in vivo measurement of a carotid artery. The results showed that similar accuracies were obtained at high (6.94 MHz) and low (4.8 MHz) frequencies and better visualization of weak echoes from blood cells was achieved at 6.94 MHz.