The formulation of virtual sources are no less important than other parts in the Beamforming formulation, as they are fundamental to compute a valid delay time and select the correct samples for the interpolation. Not all the samples are valid, and so we must interpolate just between the indexes of samples that are considered valid. Let us recall that this process is fundamental to increase the investigation depth and a high signal quality thanks to the higher SNR generated. One third of the beamforming process consists in the selection of the samples, and so it has been important to detail the aspects which regards this process.