Non-grid based elements positioning for optimal 2D array beams

2D matrix probes present a real capability for three dimensional ultrasound imaging. The main difficulties to implement these probes come from the need of using a huge number of elements and from the grating lobes linked to the element periodical disposition and from the sidelobes arising when this number is reduced. In this study, a new design technique is proposed and shown capable of considerably reducing the probe element number as well as the grating lobes and sidelobes level. The grating lobes, in particular, are reduced by placing the elements without any grid consideration. The sidelobes and the number of active elements are optimized by the simulated annealing. Using the new approach we reduce the element number by 28% (from 235 to 169) and obtain a grating lobe reduction by -10 dB and -20 dB in lateral and elevation direction, respectively.