Improvement of penetration of modified amplitude and phase estimation beamformer

Omura

et al. 2023

Jpn. J. Appl. Phys.

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In medical ultrasound systems, receive beamforming is necessary to produce an ultrasonic image. Although minimum variance (MV) beamforming was developed to achieve higher image quality than commonly used delay-and-sum (DAS) beamforming, it is computationally expensive. Therefore, in this study, we investigated a method to learn the relationship between DAS-beamformed signals and MV-beamformed ones using deep learning. The results showed that a fully convolutional network (FCN) could produce an image with comparable quality to that in MV beamforming in a shorter time than the conventional MV beamformer.

Section: Methodsmentioning

confidence: 99%

Beamspace-domain learning of minimum variance beamformer with fully convolutional network

Hiki

Omura

et al. 2023

Jpn. J. Appl. Phys.

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“…However, when the proposed method is performed without sub-aperture beamforming, the dimension of the covariance matrix becomes large and high computational cost is required to calculate the inverse matrix of the covariance matrix. The sub-aperture beamforming can reduce the dimension of the covariance matrix, and accordingly, the computation time becomes shorter [27].…”

Section: Discussionmentioning

confidence: 99%

“…Blomberg et al proposed the amplitude and phase estimation (APES) beamformer [25], which eliminates the desired signal from the spatial covariance matrix by DAS beamforming, where the desired signal means the signal which is coherent with the echo from the focal point. We modified the APES beamforming for more accurate estimation of the desired signal by considering the directivity of the array transducer element to discard sub-array averaging [26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Adaptive Beamformer Combined with Phase Coherence Weighting Applied to Ultrafast Ultrasound

Hasegawa

2018

Applied Sciences

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Ultrafast ultrasound imaging is a promising technique for measurement of fast moving objects. In ultrafast ultrasound imaging, the high temporal resolution is realized at the expense of the lateral spatial resolution and image contrast. The lateral resolution and image contrast are important factors determining the quality of a B-mode image, and methods for improvements of the lateral resolution and contrast have been developed. In the present study, we focused on two signal processing techniques; one is an adaptive beamformer, and the other is the phase coherence factor (PCF). By weighting the output of the modified amplitude and phase estimation (mAPES) beamformer by the phase coherence factor, image quality was expected to be improved. In the present study, we investigated how to implement the PCF into the mAPES beamformer. In one of the two examined strategies, the PCF is estimated using element echo signals before application of the weight vector determined by the adaptive beamformer. In the other strategy, the PCF was evaluated from the element signals subjected to the mAPES beamformer weights. The performance of the proposed method was evaluated by the experiments using an ultrasonic imaging phantom. Using the proposed strategies, the lateral full widths at half maximum (FWHM) were both 0.288 mm, which was better than that of 0.348 mm obtained by the mAPES beamformer only. Also, the image contrasts realized by the mAPES beamformer with the PCFs estimated before and after application of the mAPES beamformer weights to the element signals were 5.61 dB and 5.32 dB, respectively, which were better than that of 5.14 dB obtained by the mAPES beamformer only.

“…The performance of the proposed method was evaluated by the phantom experiments. [25][26][27][28][29][30][31] The output of the MV beamformer is expressed as…”

Section: Introductionmentioning

confidence: 99%

Investigation on improving performance of adaptive beamformer by statistical analysis of ultrasonic echoes

Akamatsu

Omura

et al. 2022

Jpn. J. Appl. Phys.

Self Cite

Minimum variance (MV) beamformers have been introduced in medical ultrasound imaging to improve image quality. In most cases, the MV beamformers have been investigated in terms of resolution improvement. However, the contrast-to-noise ratio (CNR) is also a clinically important metrics and gathers attention recently. In this study, we examined the diagonal loading parameter σ in MV beamforming and determined its appropriate value by evaluating image quality evaluation metrics including CNR. In order to further improve the image quality, a method for determining the value of σ based on the difference in statistical properties of received ultrasonic echo signals was also investigated. The phantom experimental results showed that the proposed method achieved a better CNR than the conventional MV beamformer while keeping resolution significantly better than that in delay-and-sum (DAS) beamforming.