IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL, . 59, . 4, APRIL 2012 703 0885–3010/$25.00 © 2012 IEEE Application of 1-D Transient Elastography for the Shear Modulus Assessment of Thin-Layered Soft Tissue: Comparison With Supersonic Shear Imaging Technique Javier Brum, Jean-Luc Gennisson, Thu-Mai Nguyen, Nicolas Benech, Mathias Fink, Mickael Tanter, and Carlos Negreira Abstract—Elasticity estimation of thin-layered soft tissues has gained increasing interest propelled by medical applica- tions like skin, corneal, or arterial wall shear modulus assess- ment. In this work, the authors propose one-dimensional tran- sient elastography (1DTE) for the shear modulus assessment of thin-layered soft tissue. Experiments on three phantoms with different elasticities and plate thicknesses were performed. First, using 1DTE, the shear wave speed dispersion curve in- side the plate was obtained and validated with finite difference simulation. No dispersive effects were observed and the shear wave speed was directly retrieved from time-of-flight measure- ments. Second, the supersonic shear imaging (SSI) technique (considered to be a gold standard) was performed. For the SSI technique, the propagating wave inside the plate is guid- ed as a Lamb wave. Experimental SSI dispersion curves were compared with finite difference simulation and fitted using a generalized Lamb model to retrieve the plate bulk shear wave speed. Although they are based on totally different mechanical sources and induce completely different diffraction patterns for the shear wave propagation, the 1DTE and SSI techniques resulted in similar shear wave speed estimations. The main ad- vantage of the 1DTE technique is that bulk shear wave speed can be directly retrieved without requiring a dispersion model. I. I E  is the common name for many tech- niques developed within the past two decades for non- invasive assessment of the mechanical properties of bio- logical soft tissues with application to medical diagnosis. These techniques can mainly be divided into two groups: static and dynamic elastography. In static elastography [1], [2] a compression is applied by pressing an ultrasonic probe on the tissue. A strain map is obtained by compar- ing the displacements before and after each compression. However, because of the lack of information on the stress to which the tissue is subjected, this method does not pro- vide a quantitative elasticity estimation. To overcome this limitation, a set of techniques based on shear wave propa- gation inside the tissue has been developed during the past decade. These techniques can be categorized under the name dynamic elastography. They consist basically of three steps: first, the tissue is mechanically stressed, resulting in shear wave generation; second, the induced displacements are imaged; and, finally, the tissue’s elastic properties are deduced from the measured displacement field. Because shear waves are used, and their speed is related to the tissue’s shear modulus, the dynamic ap- proach provides a quantitative estimation of the tissue’s elasticity. There are several ways to image the displacement field (e.g., ultrasound [3], [4] or MRI [5]) and to generate the shear waves (e.g., mechanical vibrator [6]–[8] or ultra- sound radiation force [9]–[11]). One-dimensional transient elastography (1DTE) [6] uses a low-frequency vibrator as an external shear wave source, whereas the supersonic shear imaging (SSI) [11] technique consists of generating broadband shear waves inside the sample by using the radiation force created by a focused ultrasonic beam. For both techniques, the shear wave propagation is tracked using an ultrafast ultrasound scanner. The shear wave speed (c T ) is retrieved by applying a time of flight algo- rithm to the acquired displacement field. The shear modu- lus (μ) of the medium is then retrieved through the well- known relationship: μ = ρ c T 2 , where ρ is the medium’s density. Both techniques have been successfully applied to noninvasively determine the mechanical parameters of liv- ing tissues such as breast [12], liver [13], [14], or muscle [15], [16]. The applicability of the SSI technique to viscoelastic assessment of thin soft tissues has recently been demon- strated in the cornea [17] and the arterial wall [18]. In these specific cases, the wavelength of the propagating wave is of the order of the cornea/arterial wall thickness, leading to a propagation which is related to the leaky Lamb wave theory of guided waves. The bulk shear wave speed, and thus the shear modulus, are retrieved from the Lamb wave dispersion curve using a specific model [18], [19]. The applicability of 1DTE for arterial shear modulus assessment was tested on one arterial phantom at a fixed excitation frequency of 150 Hz [20]. In the present work, the authors propose and validate the use of 1DTE for the quantitative assessment of the Manuscript received November 4, 2011; accepted December 27, 2011. J. Brum, N. Benech, and C. Negreira are with the Laboratorio de Acústica Ultrasonora, Instituto de Física, Facultad de Ciencias, Monte- video, Uruguay (e-mail: jbrum@fisica.edu.uy). J.-L. Gennisson, T.-M. Nguyen, M. Fink, and M. Tanter are with the Institut Langevin Ondes et Images, Ecole Supérieure de Physique et de Chemie Industrielles (ESPCI, ParisTech), Centre National de la Recher- che Scientifique (CNRS) UMR 7587, Inserm ERL U979, Paris, France. DOI: http://dx.doi.org/10.1109/TUFFC.2012.2248