Ultrasound elastonography of thyroid nodules

Abstract

Purpose/aim: the different techniques, suggesting how we can improve accuracy, and reduce interobserver variability. We will present our personal experience and review the literature Content organization: Thyroid gland examination by palpation is a basic method in the assessment of thyroid nodules, as firm and anelastic lesions should be suspected being of malignant nature. On the other hand, US, despite its high sensitivity for the detection of thyroid lesion, has limited accuracy to differentiate benign and malignant lesions. Hypervascularity, irregularity of margins, microcalcifications and hypoechogenicity are the most prominent features of malignancies however also CDUS has variable accuracy. To date, FNAC is still considered the gold standard for optimal characterization of thyroid lesions, but still in 15% to 25% of cases FNAC findings can be suspicious and in 5% to 15% of cases inconclusive. Elastography is a new imaging modality where elastic tissue parameters related to the structural organization of normal and pathological tissues are imaged. New tools allowing non-invasive real-time evaluation of these lesions thus needed. Thyroid elastosonography 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: Elastosonography – 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. Elastography has showed good diagnostic values both with qualitative and quantitative modalities. However, still some issues may be. How accurate is it? How reproducible is it? Which role may have in the 3 nodule characterization? We will discuss the different techniques, suggesting how we can improve accuracy, and reduce interobserver variability. We will present our personal experience and review of the literature.