Optimization of Frequency and Plane- Wave Compounding by Minimum Variance Beamforming

We previously proposed a beamformer that adaptively compounds echoes for different subbands and transmission angles. This methodology requires the transmission and reception of multiple plane waves. The present paper thus examines a method that approximates the previous method with one transmission and reception. By assigning different subbands to each transmission direction and simultaneously transmitting one shot as a chirp signal, echoes for all subbands can be received at the same time. Then, through pulse-compression, the received echo is separated into each sub-band, and by applying our previously proposed compound procedure, imaging by one-shot beamforming is realized. The evaluation of the performance of this method using a finite element simulator confirmed that the resolution was almost the same as that of our original beamformer, although the contrast was worse. We report results for the causes and solutions of this contrast deterioration.

Section: Fpwc-mvdr Beamformermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

One-shot beam-forming with adaptively weighted compound of multiple transmission angles and subbands

Saito

憲男

2022

“…Inspired by DCR-MVDR, we also proposed the FPWC-MVDR method, 19) in which multiple transmissions and receptions are performed within different frequency bands.…”

Section: Frequency Compounding With Adaptive Weightsmentioning

confidence: 99%

“…We then proposed the frequency and plane-wave compounding MVDR (FPWC-MVDR) method, which was integrated with the spatial compounding, and confirmed that the axial resolution was improved significantly by using frequency weights when summing the echoes for all subbands. 19) However, this method has the disadvantage that the number of transmission and reception operations required increases based on the number of subbands used. Therefore, in this study, we propose the filtered-FPWC-MVDR method, which transmits and receives the entire effective band simultaneously and then extracts and weights the multiple narrow subbands via frequency filtering.…”

Section: Introductionmentioning

confidence: 99%

Plane wave beamforming with adaptively weighted frequency compound using bandpass filtering

Zheng

Tagawa

Yoshizawa

et al. 2021

Self Cite

We previously proposed the frequency and plane-wave compounding minimum variance distortion-free response (FPWC-MVDR) beamformer for ultrasonic reception beamforming, which weights the transmission angle and frequency band adaptively. This method required multiple subband transmissions and receptions for each transmission angle, reducing the frame rate. Here, we propose a filtered-FPWC-MVDR method that extracts and uses subband components via signal processing from the echo received after a single wideband pulse transmission. After confirming that this method provides the same performance as the original FPWC-MVDR, we experimentally investigate the subband conditions required, i.e. the bandwidth and number of subbands, when using this method. As a result, to improve the point target resolution, we find that there is an appropriate subbandwidth condition involving a trade-off between ensuring echo localization and increasing the degrees of freedom for frequency weight determination. Additionally, for improved contrast, the subbands were arranged appropriately to cover the entire usable frequency band.

“…[20][21][22] This method confirmed that by adjusting the bandwidth of the subband, not only is the range and azimuth resolution greatly improved, but also the speckle level is effectively lowered. 23) In addition, this method allows the subband components to be freely extracted from the echo; their amplitudes are then normalized and used, making it applicable to low-amplitude harmonics. 24) Here we also proposed a method that transmits high-voltage short pulse signals, and then adaptively uses the band for each pixel by dividing the harmonic band into subbands and compounding them.…”

Section: Introductionmentioning

confidence: 99%

Subband compound with fundamental wave and harmonics in focus wave beamforming

Zheng¹,

憲男²,

Yoshizawa³

et al. 2022

Self Cite

The use of harmonics offers high resolution and low artifact imaging. However, the image intensity depends on the depth of field and is significantly weaker than the fundamental echo. The simultaneous use with the fundamental echo is therefore desirable. However, the frequency bands corresponding to the fundamental and harmonics are different, and the difference in value between their amplitudes is large. Imaging them simultaneously is difficult. Therefore, we propose a method that employs a single short-period transmission of a low-frequency pulse signal so that the fundamental and the harmonic meet. Then we use the subband compound method which treats the fundamental and harmonic bands as a single frequency band. Several regularized subbands of different frequencies are subsequently extracted from the entire frequency band. In effect, this method uses the phase information of the frequency band and improves the spatial resolution and signal-to-noise ratio through sub-band amplitude modulation while suppressing artifacts.