We are interested in examining how our model-based beamforming algorithm, referred to as aperture-domain model image reconstruction (ADMIRE), performs on plane wave sequences in conjunction with synthetic aperture beamforming. We also aim to identify the impact of ADMIRE applied before and after synthetic focusing. We employed simulated phantoms using Field II and tissue-mimicking phantoms to evaluate ADMIRE as applied to synthetic sequencing. We generated plane wave images with and without synthetic aperture focusing (SAF) and measured contrast and contrast-to-noise ratio (CNR). For simulated cyst images formed from single plane waves, the contrast for delay-and-sum (DAS) and ADMIRE are 15.64 and 28.34 dB, respectively, whereas the CNR are 1.76 and 3.90 dB, respectively. We also applied ADMIRE to simulated resolution phantoms having a point target at 3 cm depth on-axis. We simulated the point spread functions from data obtained from 1 plane wave and 75 steered plane waves, along with linear scans with 3 and 4 cm- focal depths. We then compared the outcome of applying ADMIRE before and after SAF using 3 and 11 steered plane waves. Finally, we applied this to an in vivo carotid artery. Based on the findings in this study, ADMIRE can be adapted to full field insonification sequences to improve image quality in plane wave imaging. Additionally, we investigated how robustly ADMIRE performs in the presence of random noise. We then address identified limitations using a conventional envelope detection method with decluttered signals.
Previous studies demonstrated that our aperture domain model image reconstruction (ADMIRE) beamforming algorithm mitigates some common ultrasound imaging artifacts, which may increase ultrasound's clinical utility and reliability. Specifically, ADMIRE can suppress clutter caused by reverberation, off-axis scattering and wavefront aberration. Along with this, we demonstrated that ADMIRE is robust to model-mismatch caused by gross sound speed deviation. These findings suggest that ADMIRE may be an effective tool to provide high quality images in real clinical applications. Many of our previous effort have occurred on research platforms, but it is thought that dedicated clinical systems have better front-end electronics and transducers compared to research oriented platforms. If this is true then it is important to perform in vivo evaluations using the highest quality data possible in order to appropriately characterize (and not overemphasize possible) algorithmic gains. To this end, we modified a Siemens ACUSON SC2000 ultrasound system to capture I/Q channel signals. We acquired channel data using a full synthetic receive sequence. We also acquired channel data in conjunction with pulse inversion sequencing to obtain harmonic images. In this study, we collected data from a tissue-mimicking phantom and a human subject's abdomen and liver. We reconstructed both fundamental and harmonic B-mode images before and after applying ADMIRE. We then measured contrast and contrast-to-noise ratio (CNR). When comparing in vivo images, ADMIRE using low and high degrees of freedom improves contrast by 12.2 ± 2.6 dB and 2.5 ± 0.5 dB, respectively, relative to fundamental delay-and-sum(DAS) B-mode, and boosts contrast by 8.7 ± 3.7 dB and 2.0 ± 0.7 dB, respectively, with harmonic B-mode images.
In our previous studies, we demonstrated that our aperture domain model-based clutter suppression algorithm improved image quality of in vivo B-mode data obtained from focused transmit beam sequences. Our approach suppresses off-axis clutter and reverberation and tackles limitations of related algorithms because it preserves RF channel signals and speckle statistics. We call the algorithm aperture domain model image reconstruction (ADMIRE). We previously focused on reverberation suppression, but ADMIRE is also effective at suppressing off-axis clutter. We are interested in how ADMIRE performs on plane wave sequences and the impact of AD- MIRE applied before and after synthetic beamforming of steered plane wave sequences. We employed simulated phantoms using Field II and tissue-mimicking phantoms to evaluate ADMIRE applied to plane wave sequencing. We generated images acquired from plane waves with and without synthetic aperture synthesis and measured contrast and contrast-to-noise ratio (CNR). For simulated cyst images formed from single plane waves, the contrast for delay-and-sum (DAS) and ADMIRE are 15.64 dB and 28.34 dB, respectively, while the CNR are 1.76 dB and 3.90 dB, respectively. Based on these findings, ADMIRE improves plane wave image quality. We also applied ADMIRE to resolution phantoms having a point target at 3 cm depth on-axis, simulating the point spread functions from data obtained from 1 and 75 steered plane waves, along with linear scan at focus of 3 and 4 cm depth. We then examined the outcome of applying ADMIRE before and after synthetic aperture processing. Finally, we applied this to an in vivo carotid artery.