2D matrix array optimization by simulated annealing for 3D hepatic imaging

In this paper we present a preliminary study of a 2D sparse array design technique. The probe is intended to be suitable for needle tacking during hepatic biopsy and therapy applications. It can also be used in other micro-tools or internal organs operations. The probe is composed of 1024 elements (64x16). Due to this huge number of elements, the sparse array technique is used to reasonably reduce this number and to make possible its connection to the recent scanners. The simulated annealing algorithm permits to optimize elements coefficients and their positions to have a better beam pattern. The features of the probe must satisfy the geometrical constraints imposed by the targeted applications as well as some users defined imaging characteristics. Several simulations are made to know the acoustical characteristics of the array and its convenience to needle detection operations. Combining sparse array and optimization algorithm we reduce the initial element number to 267 with good imaging features: the sidelobes level is maintained to - 40 dB, the lateral main lobe width at -6 dB is 1.1 mm and the elevation main lobe width is 4.4 mm.