Purpose: To present the main features, the accuracy and the main recognized limitations of the different elastographic techniques and suggesting how we can improve accuracy and reduce interobserver variability.
Content organization: US-Elastography (USE) is a new imaging modality where elastic tissue parameters related to the structural organization of normal and pathological tissues are imaged. Clearly, not all nodules found at physical examination or at any imaging method should undergo fine needle biopsy. New tools allowing non-invasive real-time evaluation of these lesions are thus needed. Any technique used to determine which nodules can be safely monitored without biopsy should have a sensitivity close to 100%, and this is not the case of CDUS. Thyroid USE has been developed owing to such a need of a more accurate method than CDUS. The relationship of tissue elasticity and hardness to palpability follows the basic principle that to be palpable, the object must be harder than the surrounding tissue. Several methods have been proposed, such as USE. USE is based upon the principle that malignancies have stiff tissues and that, under compression, the softer parts of tissues deform easier than the harder parts . The force of compression can be provided either directly by the operator's hand or by the carotid artery pulsation or by using shear waves. The evaluation of stiffness can be qualitative with a color coding system or quantitative with off line measurements. A review of the basic clinical (palpation) and ultrasound features (hypervascularity, irregularity of margins, microcalcifications and hypoechogenicity) will be provided, with their limitations and the unsolved issues, together with a brief discussion of FNAC.
An explanation of the various types of USE techniques will be then discussed, together with their diagnostic performances, and limits. A review of the literature and our personal experience will try to address the discussion so as to answer to the subsequent questions:
How accurate it is? How reproducible is it? Which role may have in the areas still considered "grey area” Thy3 nodule characterization? How can we improve the accuracy? Can the interobserver variability be reduced? Is it too early to employ USE to address the clinical management?
