title: Nonlinear viscoelastic properties of tissue assessed by ultrasound.
abstract: A technique to assess qualitatively the presence of higher-order viscoelastic parameters is presented. Low-frequency, monochromatic elastic waves are emitted into the material via an external vibrator. The resulting steady-state motion is detected in real time via an ultra fast ultrasound system using classical, one-dimensional (1-D) ultrasound speckle correlation for motion estimation. Total data acquisition lasts only for about 250 ms. The spectrum of the temporal displacement data at each image point is used for analysis. The presence of nonlinear effects is detected by inspection of the ratio of the second harmonics amplitude with respect to the total amplitude summed up to the second harmonic. Results from a polyacrylamide-based phantom indicate a linear response (i.e., the absence of higher harmonics) for this type of material at 65 Hz mechanical vibration frequency and about 100 microm amplitude. A lesion, artificially created by injection of glutaraldehyde into a beef specimen, shows the development of higher harmonics at the location of injection as a function of time. The presence of upper harmonics is clearly evident at the location of a malignant lesion within a mastectomy.
authors.affiliation: Laboratoire Ondes et Acoustique, Ecole Supérieure de Physique et de Chimie Industrielle, Université Denis Diderot-Paris 7, Centre National de la Recherche Scientifique Unité Mixte de Recherche 7587, France. ralph.sinkus@espci.fr
authors.forename: Ralph
authors.initials: R
authors.lastname: Sinkus
authors.forename: Jeremy
authors.initials: J
authors.lastname: Bercoff
authors.forename: Mickaël
authors.initials: M
authors.lastname: Tanter
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Gennisson
authors.forename: Carl
authors.initials: C
authors.lastname: El-Khoury
authors.forename: Vincent
authors.initials: V
authors.lastname: Servois
authors.forename: Anne
authors.initials: A
authors.lastname: Tardivon
authors.forename: Mathias
authors.initials: M
authors.lastname: Fink
mesh_terms: D000465:Algorithms; D000818:Animals; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D003198:Computer Simulation; D004548:Elasticity; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008954:Models, Biological; D017711:Nonlinear Dynamics; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods*; D014783:Viscosity