Temporal analysis of tissue displacement induced by a transient ultrasound radiation force.
One of the stress sources that can be used in dynamic elastography imaging methods is the acoustic radiation force. However, displacements of the medium induced by this stress field are generally not fully understood in terms of spatial distribution and temporal evolution. A model has been developed based on the elastodynamic Green's function describing the different acoustic waves generated by focused ultrasound. The function is composed of three terms: two far-field terms, which correspond to a purely longitudinal compression wave and a purely transverse shear wave, and a coupling near-field term which has a longitudinal component and a transverse component. For propagation distances in the shear wavelength range, the predominant term is the near field term. The displacement duration corresponds to the propagation duration of the shear wave between the farthest source point and the observation point. This time therefore depends on the source size and the local shear modulus of the tissue. Evolution of the displacement/time curve profile, which is directly linked to spatial and temporal source profiles, is computed at different radial distances, for different durations of force applications and different shear elastic coefficients. Experimental results performed with an optical interferometric method in a homogeneous tissue-mimicking phantom agreed with the theoretical profiles.
Callé
Samuel
S
GIP ULTRASONS-LUSSI, FRE 2448 CNRS, 2 bis boulevard Tonnellé, 37032 Tours, France. calle_s@med.univ-tours.fr
Remenieras
Jean-Pierre
JP
Matar
Olivier Bou
OB
Hachemi
Melouka Elkateb
ME
Patat
Frédéric
F
D000162:Acoustics; D000465:Algorithms; D004548:Elasticity; D008954:Models, Biological; D014463:Ultrasonography / Q000379:methods*; D014781:Viscera / Q000000981:diagnostic imaging*