Orthogonal Frequency Division Multiplexing Combined with Multi Line Transmission for Ultrafast Ultrasound Imaging: Experimental Findings

Multi line transmission (MLT) and orthogonal frequency division multiplexing (OFDM) are techniques that have been individually applied to increase ultrasound imaging data acquisition rate. For both modalities, generating multiple beams in the transmit phase comes at the cost of image quality. In particular, interbeam cross-talk results in imaging artifacts, the intensity of which increases with the number of beams transmitted in parallel. In this study, we investigated experimentally whether and how the combination of MLT and OFDM could be used to achieve a high number of parallel beams with reduced cross-talk with respect to their individual use. Ultrasound images of wire targets and of a tissue-mimicking phantom have been acquired and analyzed for different configurations, i.e., with 2 to 6 beams transmitted in parallel. Imaging features such as the contrast ratio, contrast to noise ratio, axial resolution, and interbeam cross-talk have been evaluated. In conclusion, combining MLT and OFDM is effective to achieve a high data acquisition rate with limited cross-talk and higher CNR, with the drawback of reduced axial resolution and slightly diminished CR.