Elastographic techniques of thyroid gland: current status

Abstract

Thyroid nodules are very common with malignancies accounting for about 5 %. Fine-needle biopsy is the most accurate test for thyroid cancer diagnosis. Elastography, a new technology directly evaluating the elastic property of the tissue, has been recently added to the diagnostic armamentarium of the endocrinologists as noninvasive predictor of thyroid malignancy. In this paper, we critically reviewed characteristics and applications of elastographic methods in thyroid gland. Elastographic techniques can be classified on the basis of the following: source-of-tissue compression (free-hand, carotid vibration, ultrasound pulses), processing time (real-time, off-line), stiffness expression (qualitative, semi-quantitative, or quantitative). Acoustic radiation force impulse and aixplorer shear wave are the newest and most promising quantitative elastographic methods. Primary application of elastography is the detection of nodular lesions suspicious for malignancy. Published data show a high sensitivity and negative predictive value of the technique. Insufficient data are available on the possible application of elastography in the differential diagnosis of indeterminate lesions and in thyroiditis. Elastography represents a noninvasive tool able to increase the performance of ultrasound in the selection of thyroid nodules at higher risk of malignancy. Some technical improvements and definition of more robust quantitative diagnostic criteria are required for assigning a definite role in the management of thyroid nodules and thyroiditis to elastography.

Ultrasound elastography in thyroid disease

“…These areas should be included in the differential diagnosis of carcinoma. They are harder than the ones encountered in chronic thyroiditis [10]. The appearance is significantly different from multinodular goiter, but not from cancer.…”

“…The recently published guidelines of EFSUMB [8] provide an orderly approach to the understanding of various elastographic techniques. Some of the reviews on thyroid USE provided own classifications [9,10] while others complied with the guidelines [11].…”

“…Basically, two main approaches for elastography of the thyroid are used in clinical practice: strain and shearwave elastography [8][9][10][11] (fig 1). Most of the times, offline analysis of the information is performed in experimental, work-in-progress models or on prototypes while machines for clinical applications use online signal processing.…”

“…In a low risk case with indeterminate or nondiagnostic FNAB, a negative elastographic result may represent a reassuring information to avoid FNAB or surgery and institute follow-up, freeing resources for patients with suspicious nodules [121]. The constantly high negative predictive values of the elastography techniques infer that elastography is useful in determining which nodule may be followed up without FNAB [10]. On the other hand, hard nodules need to be biopsied, even if some of them will show no malignancy [7].…”

“…On the other hand, hard nodules need to be biopsied, even if some of them will show no malignancy [7]. The combination grey scale and elastography is useful for the selection of the nodules that will undergo puncture, as it lowers the risk of overlooking nonsuspicious grey-scale appearing nodules [10].…”