US elastography: Applications in tumors

Abstract

Ultrasound elastography is a new technique that generates images based on the stiffness of tissue as opposed to anatomy. Many disease states have changes in stiffness that can be detected by elastography. There are two elastography techniques presently available, strain and shear wave imaging. Breast pathology is extremely sensitive and specific for characterization using elastography. There is a unique elastography characteristic of breast masses where the lesions appear larger than on B-mode if malignant and smaller if benign. This change does not appear to occur in other organs. Focal liver masses have a mixed appearance on elastography with a large overlap in the stiffness of benign and malignant lesion making characterization of focal liver masses problematic with elastography. However, diffuse liver disease such as fibrosis can be graded and monitored with shear wave elastography. Although early in its development detection of prostate cancer in the peripheral zone by elastography appears very sensitive and specific. It has a very high negative predictive value that may limit the number of biopsies performed to detect prostate cancer. Elastography can be used in the evaluation of cystic lesions. A unique artifact occurs with strain imaging on some vendor equipment that is highly specific and sensitive for characterization of benign simple and complicated cysts. Shear waves do not propagate in simple fluid. Initial studies suggest shear wave imaging may be helpful in characterization of cystic lesion as serous or mucinous in nature. Initial results in thyroid, pancreas, lymph nodes, and testicular masses are promising. There has not been little evaluation in gynecological or musculoskeletal tumors to date.