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., 9.0×109
vs 2.9×109 ) 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.