Multiplane wave imaging increases signal-to-noise ratio in ultrafast ultrasound imaging

Abstract

Ultrafast imaging using plane or diverging waves has recently enabled new ultrasound imaging modes with improved sensitivity and very high frame rates. Some of these new imaging modalities include shear wave elastography, ultrafast Doppler, ultrafast contrast-enhanced imaging and functional ultrasound imaging. Even though ultrafast imaging already encounters clinical success, increasing even more its penetration depth and signal-to-noise ratio for dedicated applications would be valuable. Ultrafast imaging relies on the coherent compounding of backscattered echoes resulting from successive tilted plane waves emissions; this produces high-resolution ultrasound images with a trade-off between final frame rate, contrast and resolution. In this work, we introduce multiplane wave imaging, a new method that strongly improves ultrafast images signal-to-noise ratio by virtually increasing the emission signal amplitude without compromising the frame rate. This method relies on the successive transmissions of multiple plane waves with differently coded amplitudes and emission angles in a single transmit event. Data from each single plane wave of increased amplitude can then be obtained, by recombining the received data of successive events with the proper coefficients. The benefits of multiplane wave for B-mode, shear wave elastography and ultrafast Doppler imaging are experimentally demonstrated. Multiplane wave with 4 plane waves emissions yields a 5.8 ± 0.5 dB increase in signal-to-noise ratio and approximately 10 mm in penetration in a calibrated ultrasound phantom (0.7 d MHz(-1) cm(-1)). In shear wave elastography, the same multiplane wave configuration yields a 2.07 ± 0.05 fold reduction of the particle velocity standard deviation and a two-fold reduction of the shear wave velocity maps standard deviation. In functional ultrasound imaging, the mapping of cerebral blood volume results in a 3 to 6 dB increase of the contrast-to-noise ratio in deep structures of the rodent brain.

Improved Contrast-Enhanced Ultrasound Imaging With Multiplane-Wave Imaging

“…MW imaging [9] was proposed as a way to increase SNR in conventional coherent plane wave compounding [8] without sacrificing the spatial resolution or frame rate. To facilitate the concise presentation of the proposed method, herein we use an example of a two-angle MW compounding sequence as shown in Fig.…”

“…The decoded signals are re-aligned in the fast time to compensate for Δ t , and then beamformed and compounded using the classic coherent plane wave compounding approach. MW compounding provides images with improved SNR as compared with conventional plane wave compounding with a preserved frame rate and spatial resolution [9]. …”

“…Multiplane wave (MW) compounding was recently proposed as a way to increase SNR in conventional coherent plane wave compounding [8] without sacrificing the spatial resolution or frame rate [9]. In MW imaging, multiple plane waves with different steering angles are emitted quasi-simultaneously with a short interleaved time delay (a few microseconds) in each single transmission event (i.e., the pulse-echo event).…”

“…Upon receive, the RF signals are decoded through addition or subtraction and then re-aligned in fast time to recover the signals as they would have been obtained from each steering angle. The decoded and re-aligned RF signals are then beamformed and compounded using the conventional coherent compounding plane wave imaging approach to improve SNR [9]. …”

Quantitative Ultrasound Molecular Imaging in Large Blood Vessel Environments

“…Typically, multiple plane waves [25], [27] or diverging waves [28] with different steering angles are transmitted sequentially. Thanks to the coherent summation of the received backscattered echoes, contrast and signal-to-noise ratio can be regained [25], [26].…”