Reducing the number of receiving channels using transmit-receive symmetry in synthetic transmit aperture imaging

Synthetic transmit aperture (STA) imaging has been widely studied in ultrasound imaging. Usually the number of receiving channels is the same as the number of the array elements (N). When the number of receiving channels is large, such as the matrix array for 3D imaging, the system cost will be high due to the receiving electronics for each element. Therefore, it is desirable to reduce the number of receiving channels while keeping a large number of transmit channels. In this paper, we studied with Field II Hadamard-encoded synthetic transmit aperture imaging systems with about N/2, N/4 and N/8 receiving channels. There were N Hadamard-encoded transmission events for one frame of image. The pseudoinverse was applied to the acquired RF data to estimate the equivalent signal in the traditional STA. We found that applying the transmit-receive symmetry of RF signals can reduce the receiving channels by half without compromising image quality. We also compared different methods to encode the receivers when the receiving channels were reduced to about N/4 and N/8.