Ultrasonic imaging provides a non-invasive way to diagnose brain disease. However, due to imaging degradation effects from the phase-aberration and reverberation, it is still challenging to achieve an accurate transcranial imaging. The objective of this work is to improve the quality of transcranial imaging. To this end, a ray theory based transcranial phase correction method was proposed to correct the phase abberation induced by cranial bones. With the pre-knowledge of the shape and longitudinal velocity of the cranial bones, the corrected phases are derived by solving eikonal equation (ray-theory). The Ideal Synthetic Aperture Focusing Technique (I-SAFT) is applied for signal acquisitions in simulations and in-vitro phantom experiment with one-element transmitting and all-element receiving method. Dynamic focusing is achieved at each imaging position with I-SAFT and the transcranial imaging distortion is modified with the proposed phase correction method. Simulations and experiments show that the imaging distortion of target circular phantoms was corrected, and the imaging quality is improved after the phase correction. With the proposed method, the average error of the central position of target phantoms decreases from 1.98 mm to 0.21 mm, the eccentricity of fitted ellipse averagely decreases from 0.63 to 0.19, and the average maximum luminance contrast of phantoms improves from 37.36dB to 42.41dB. It is illustrated that the proposed ray-theory based phase correction method might be useful for intracranial imaging.

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Wireless technologies based on electromagnetic wave are crucial in the modern industry but nonoptimal in electromagnetic-restricted conditions such as underwater applications, where acoustic wave has been proposed as an indispensable approach. However, most of the current acoustic wireless methods could support single wireless function and control single device. A converged wireless infrastructure that simultaneously supports the mainstream wireless functions remains inaccessible for acoustics. The difficulty lies in constructing the dynamic control network consisting of multiple nodes with acoustic method. Here, we develop the converged wireless infrastructure based on the acoustic holographic array, which serves as the central hub of the system. The holographic array allows for simultaneous control of multiple targets and integrates multiple mainstream wireless functions. We experimentally present the acoustic version of the converged wireless system that realizes a series of functions, including (i) selective wireless power transfer, (ii) stable remote monitoring, (iii) dynamic programmable logic control, and (iv) wireless acoustic communication. The wireless system is capable of powering and controlling free-moving devices. The unique immunity against electromagnetic and biological interferences is further demonstrated. The acoustic-based wireless infrastructure provides a route to wireless technologies, especially for those in electromagnetic-restricted conditions.

Three-dimensional (3D) ultrafast imaging is important for ultrasound technology development. The traditional 3D imaging method based on fully sampled two-dimensional (2D) matrix often requires a large number of electronic channels with high density which limits the aperture size and imaging resolution in application. Recently developed row-column addressing (RCA) matrix effectively reduces the number of electronic channels from N×N to N×N by addressing the row and column elements. The beamforming strategy designed for 3D ultrasound imaging was based on the coherent compounding of orthogonal plane waves (OPW). Such a multi-angle OPW compounding strategy achieves virtual transmit focusing in both directions by transmitting a set of plane waves in one direction and receiving along the orthogonal direction, which finally leads to an isotropic point spread function (PSF). In this paper, multi-angle OPW method was investigated for 3D blood flow imaging using an RCA matrix with 128 rows and 128 columns, centered at 6×MHz. The delay and sum (DAS) beamforming was developed for coherent OPW compounding, and the singular value decomposition (SVD) filtering method was used for separating the dynamic blood flow signals from the static tissue signals and low-amplitude noise. The Doppler velocity was computed by the autocorrelation method, and finally the 3D power Doppler and color Doppler imaging of the blood flow were realized. To evaluate the imaging quality and investigate the effect of different OPW tilting angles, quantitative analysis was carried out using multiple parameters, including -6dB resolution measurements of the PSF, SNR of the power Doppler images and velocity distribution of the color Doppler. The -6dB resolution is improved from 0.986 mm to 0.493 mm with the number of angles increasing from 5 to 33. With 17 plane wave angles, the SNR of the power Doppler image reaches 30 dB, and the average deviation between the velocity distribution along the diameter of the blood flow phantom and the actual value is about 26.0 %. In conclusion, results show that the ultrafast 3D imaging method based on RCA matrix can obtain 3D B-mode, power Doppler and color Doppler images. Increasing the number of tilting angles and enlarging the angle range can significantly improve the imaging quality. The proposed method can be helpful for developing 3D ultrafast ultrasound Doppler imaging and functional ultrasound imaging based on neuro-vascular coupling.