High frame rate imaging using parallel transmission of focused coded fields [medical ultrasound imaging applications]

We have previously presented a numerical method for calculating the excitation signals on individual elements, in order to transmit multi-focused pulsed beams in parallel. This paper shows the design of FM-coded focused fields and how these fields can yield more strongly focused fields or higher frame rate. Simulated images show the implementation of the method using only 4 emissions. Neighboring beams to be formed in parallel use different codes with a cross-correlation of 20 dB. Such a cross-correlation would be insufficient using a conventional delay-and-sum beamformer. In the proposed system, the worst-case beam interference is -46 dB, making it possible to obtain images of similar resolution to conventional imaging at very high frame rates. Additionally, coding partially compensates for the SNR loss that is due to multi-focusing using only a few emissions.