Parallel transmit beamforming by means of orthogonal frequency division multiplexing: Implementation on an open research platform

Parallel receive beam forming is not optimal for harmonic imaging, as employing a wide beam or plane wave in transmission results in the generation of lower absolute pressure values, when compared to focused ultrasound beams, and conflicts with the demand for high-amplitude pressure wave fields necessary to generate the harmonic components. On the contrary, parallel transmit beam forming can be more easily applied to harmonic imaging, as focusing may be utilized to increase the amplitude of the pressure wave fields. However, interbeam interference represents an issue. To overcome these shortcomings and exploit the benefit of combining harmonic imaging and a high data acquisition rate, a new approach has been recently presented which relies on orthogonal frequency division multiplexing (OFDM) to perform parallel beamforming in transmission. Here, this technique is implemented for the first time on an advanced open platform for ultrasound research (ULA-OP) and the achievable resolution and interbeam interference have been investigated.