Quantitative Spatially Modulated Ultrasound Radiation Force Elastography

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DESCRIPTION (provided by applicant): Quantification of tissue stiffness is needed assist in diagnosis of disease. Ultrasound and MRI techniques exist for in vivo quantification of tissue stiffness, but these methods are complicated by additional equipment and can be time consuming to perform. Here we propose to develop a method we have invented called Spatially Modulated Ultrasound Radiation Force (SMURF) imaging. The principle of SMURF imaging is to use acoustic radiation force to generate a shear wave of known wavelength in tissue of unknown shear modulus and measure the frequency of the propagating shear wave to determine the shear modulus of the tissue. In a linear elastic material of density rho and shear modulus G, a shear wave's frequency f and wavelength lambda are related by G=(lambda*f)2rho. Therefore, by inducing a shear wave of known wavelength and measuring the resulting vibration frequency tissue shear modulus may be estimated. In contrast to existing methods, which apply a known frequency and estimate the wavelength of the resulting shear wave, SMURF imaging uses array beamforming techniques to produce a shear wave of a desired wavelength. A key innovation in the SMURF imaging method is that the difficult problem of wavelength estimation is replaced by the much simpler task of frequency estimation, which is routinely performed by Doppler ultrasound instruments. SMURF requires no extra apparatus and can be performed on modern ultrasound scanners with only software modifications. In contrast to Acoustic Radiation Force Impulse (ARFI) imaging, which uses a focused beam of ultrasound to displace tissue, SMURF uses a spatially varying radiation force to create a definite shear wavelength and allow for quantification. We present an integrated research plan to develop beamforming techniques needed to generate spatially varying radiation force, to show that SMURF imaging is capable of quantifying tissue stiffness with sufficient precision to be diagnostically useful, and to show that SMURF imaging can be used to estimate viscoelastic parameters of tissue. PUBLIC HEALTH RELEVANCE We have created a new technique called Spatially Modulated Ultrasound Radiation Force (SMURF) imaging for tissue stiffness estimation. SMURF uses specially shaped ultrasound beams to generate shear waves in tissue; the frequency of these waves reveals the tissue stiffness. We propose studies to develop suitable implementation techniques for a clinical ultrasound scanner and to determine the accuracy of this method.