New Direct Pixel Beamforming based on Phase Rotation

초록

Direct pixel beamforming (DPB) where receive focusing is directly performed on each display pixel in Cartesian coordinates using the raw radio-frequency (RF) data can improve spatial and contrast resolutions in medical ultrasound imaging. However, the DPB suffers from the increased computational complexity compared to the conventional delay-and-sum focusing (CON) method since it requires additional focusing points for envelop detection. In this paper, a new DPB method, in which phase rotation (PR) is adopted for reducing the number of the additional focusing points, is presented. In the proposed DPB-PR method, the complex baseband data for each display pixel is directly obtained for envelop detection, so that the unnecessary focusing points can be avoided. To evaluate the performance of the DPB-PR method, in vitro raw RF data were captured from a tissue mimicking phantom using the SonixTouch research platform connected with the SonixDAQ parallel data acquisition system. The hardware saving from the DPB-PR method was compared with the DPB method with interpolation filtering (DPB-INT) method by analyzing the number multiplications. Compared to CON, the proposed DPB-PR method shows enhanced image quality (clear shape and boundaries of masses) under visual assessment and comparable results with the DPB-INT method. Furthermore, the proposed DPB-PR method significantly reduces the number of multiplications by a factor of 3.1 (i.e., 9.0x10(9) vs 2.9x10(9)) over the DPB-INT method. This result indicates that the DPB-PR method can be implemented on a modern ultrasound imaging system while improving image quality.

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