Spatial coherence of backscattered signals in multi-line transmit ultrasound imaging and its effect on short-lag Filtered-Delay Multiply and Sum beamforming

In Multi-Line Transmission (MLT), high frame-rate ultrasound imaging is achieved by the simultaneous transmission of multiple focused beams along different directions, which unfortunately generates unwanted artifacts in the image due to inter-beam crosstalk. The Filtered-Delay Multiply and Sum (F-DMAS) beamformer, a non-linear spatial-coherence (SC)-based algorithm, was demonstrated to successfully reduce such artifacts, improving the spatial resolution at the same time. In this paper, we aim to provide further insights on the working principle and performance of F-DMAS beamforming in MLT imaging. First, we carry out an analytical study to analyze the behavior and trend of backscattered signals SC in MLT images, when the number of simultaneously transmitted beams and/or their angular spacing change. We then reconsider the F-DMAS algorithm proposing the “short-lag F-DMAS” formulation, in order to limit the maximum lag of signals used for the SC computation on which the beamformer is based. Therefore, we investigate in simulations how the performance of short-lag F-DMAS varies along with the maximum lag in the different MLT configurations considered. Finally, we establish a relation between the obtained results and the signals SC trend

Development of novel ultrasound techniques for imaging and elastography. From simulation to real-time implementation

Ultrasound techniques offer many advantages, in terms of ease of realization and patients’ safety. The availability of suitable hardware and software tools is condicio sine qua non for new methods testing. This PhD project addresses medical ultrasound signal processing and seeks to achieve two scientific goals: the first is to contribute to the development of an ultrasound research platform, while the second is introducing and validating, through this platform, non-standard methods. During the thesis, the capabilities of the system were improved by creating advanced software tools, such as acoustic field simulators, and by developing echo-signals elaboration programs. In particular, a novel technique for quasi-static elastography was developed, in-vitro tested and implemented in real-time

Experimental validation of a novel technique for ultrasound imaging of cardiac fiber orientation

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