Patent ID: 7101337
Filing Date: 2006-09-05
Classification: A61B,G01S

Abstract:
1. A noninvasive method for focusing acoustic waves in a dissipative heterogeneous medium ( 2 , 3 ) comprising a substantially homogeneous medium ( 2 ) surrounded at least partially by a dissipative aberrating layer ( 3 ) which generates aberrations in the propagation of the acoustic waves, the acoustic waves being emitted from outside the aberrating layer ( 3 ) and focused in the substantially homogeneous medium ( 2 ), characterized in that it includes the following steps: (a) an initial positioning step during which a number t greater than 2 of acoustic transducers (T an imaging array (T and a target array (T′ (b) a learning step itself comprising the following substeps: (b11) impulse responses hri(t) of the dissipative heterogeneous medium are determined, respectively between each transducer i of the imaging array and a plurality of focusing points r lying on the aberrating layer ( (b12) on the basis of these impulse responses, for each focusing point r corresponding to a transducer of the imaging array, a set of n reference time signals e′i(t,r) is calculated, i varying between 1 and n, such that if the aberrating wall were removed in the vicinity of the focusing point r, the emission of these reference signals by the various transducers i of the imaging array would generate a predetermined signal focused on the focusing point r, (b2) a substep of focusing at a number R of predetermined focusing points lying in the substantially homogeneous medium, with indices q between m+1 and m+R, this substep consisting in determining for each of these focusing points q, moving step-by-step away from the focusing points (b21) a first estimate of e′i(t,q), for i ranging from 1 to n, is calculated on the basis of at least one reference signal e′i(t,q (b22) the transducers of the imaging array are made to emit, by iterations, the estimates previously obtained of the reference signals e′i(t,q), then signals s  where the values α (b3) the reference signals e′i(t,q) are stored, at least for q between m+1 and m+R, (c) and a focusing step during which, for at least one of said focusing points q, the transducers of the imaging array are made to emit said reference signals e′