Plane Wave Formulation - 2023.2 English

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2023.2 English

In the previous paragraph we have seen the basic formulation of SA. It is very important to underline that PW is a different imaging technique but with the same expected outcome from the process of Beamformation. PW imaging, in contrast with respect to SA imaging, excites all the transducers in the same moment to emit a plane wave, whose echos are registered by the whole number of transducers in our probe. In PW we call emission a single process of excitement of the whole transducers in the probe. As it happens in SA, every emission produces a LRI by the process of beamformation. An HRI could be obtained by compounding a set of LRIs, as it happens in SA. To have multiple emissions, we use a parameter called span which represents an “aperture” angle and the directions in which we want to emit our plane waves. The span represent the total aperture of the investigation, and to determine the number of emission and the directions we use an increment parameter, which represent how many areas with respect to the total angle we want to explore. Let be clearer by providing a practical example. Let us suppose we want to perform 8 emissions with a spanning angle of 30 degrees. The investigations would be then be 8, starting from emitting a plane wave with direction of 0 degrees (or -15, depending on the system coordinates) and creating a LRI from the Beamformer. The second investigation would be an emission at 3.75 degrees direction (or -11.25, depending on the system coordinates) which is 0+3.75, where 3.75 represent our increment with respect to the emission made. We obtain then a second LRI from the Beamformer. This process is repeated until the 8th emission, and then the 8 LRIs obtained compounded in a single HRI, as it happens in SA. PW is, in terms of frame rate, the best choice for the process of beamformation. Opposite to SA, which needs a high number of emissions, PW could be performed by a single emission (at the cost of having an enormous load in terms data processing), because of the fact that it excites all (or nearly all) the transducers at the same moment. Following an image of summary of PW Imaging.