Adaptive Field-of-View Imaging for Efficient Phase Rotation Beamforming

Digital quadrature demodulation (QD)-based phase rotation beamforming (PRBF) is commonly used in ultrasound machines due to its low sensitivity to phase delay errors. However, it is very expensive computationally. To alleviate this high computational requirement during the QD, we have previously developed two efficient methods, two-stage demodulation (TSD) and multi-stage uniform coefficient (MSUC) filter. In this paper, we present an adaptive field-of-view (FOV) imaging method, which dynamically varies the beamforming frequency based on the FOV of display. When the number of channels is 32 and the number of beamforming points is 512, the proposed method lowers the complexity of the MSUC- and the TSD-based PRBF by 26.2% and 65.3%, respectively, in terms of the number of operations. The image quality with adaptive FOV imaging has been evaluated using simulation and in vivo data. Adaptive FOV imaging with the MSUC-based PRBF provides comparable contrast resolution (CR) to the QD-based PRBF for various FOV sizes (e.g., CR degradation of 0.4% and 0.01% was obtained for the FOV size of 160 mm and 85 mm, respectively). Adaptive FOV imaging with the TSD-based PRBF suffers from some degradation in image quality for the large FOV (i.e., 4.3% degradation in CR). On the other hand, it provides comparable image quality for the smaller FOV (i.e., 0.5% degradation in CR). These preliminary results indicate that the adaptive FOV imaging method has good potential to further reduce the hardware complexity of the PRBF based on MSUC and TSD.