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Elastographic imaging

2000; Elsevier BV; Volume: 26; Linguagem: Inglês

10.1016/s0301-5629(00)00156-3

1879-291X

J. Ophir, Brian S. Garra, F. Kallel, Elisa E. Konofagou, Thomas A. Krouskop, Raffaella Righetti, Tomy Varghese,

Ultrasound and Hyperthermia Applications

The mechanical attributes of soft tissues depend on their molecular building blocks (fat, collagen etc.), on the microscopic and macroscopic structural organization of these blocks (Fung 1981), and on the boundary conditions involved. These mechanical attributes may include the shear or elastic moduli (Young's modulus), the Poisson's ratio, or any of the longitudinal or shear strains that occur in tissues as a response to an applied load. In the normal breast, for example, the glandular structure may be firmer than the surrounding fibrous connective tissue, which in turn is firmer than the subcutaneous adipose tissue. Pathological changes are generally correlated with changes in tissue stiffness as well. Many cancers, such as scirrhous carcinomas of the breast, seem much stiffer and less mobile than benign (fibroadenoma) tumors (Anderson 1953). In many cases, in spite of the difference in stiffness or mobility, the small size of a pathological lesion and/or its location deep in the body impede its detection and/or evaluation by palpation. Moreover, lesions may or may not possess echogenic attributes that make them ultrasonically detectable. Because the echogenicity and the mechanical attributes of tissue are generally uncorrelated, it is expected that imaging some of the latter will provide new information that is related to tissue structure and/or pathology. For example, tumors of the prostate or the breast may be invisible or barely visible in standard ultrasound examinations, yet are much stiffer than the embedding tissue. Diffuse diseases such as cirrhosis of the liver are known to increase the stiffness of the liver tissue significantly (Anderson 1953), yet they may seem normal in conventional ultrasound examination. A clear understanding of tissue stress/strain relationships is necessary for the interpretation of any of these imaged mechanical attributes.