A new vibration theory for sonoelasticity imaging

Sonoelasticity is a new imaging technique for detection of hard tumors in tissues. In this novel diagnostic technique, a low frequency vibration at audio range is externally applied to excite internal vibrations within the tissue under inspection. Regions of different stiffness respond with different displacement. The low frequency vibration can be detected using Doppler ultrasound. By employing a properly designed scanning and detection algorithm, a real-time vibration image can be made. A theory for vibrations, or shear wave propagation in inhomogeneous elastic tissue has been developed. A tumor is modeled as an elastic inhomogeneity inside a lossy homogeneous elastic medium. The solutions take into account varying parameters such as tumor size, tumor stiffness, shape of vibration source, lossy factor of the material and vibration frequency. Computer simulations show that the vibrations around the tumor exhibit unique patterns which distinguish it from the surrounding tissue. Therefore examination of the vibration image can reveal the hard tumor inclusions. The problem of the lowest detectable change in stiffness is addressed using the theory, answering one of the most critical questions in this diagnostic technique