Elastography of Neck Masses

Abstract

Elasticity (hardness) is a mechanical tissue characteristic that prevents tissue displacement under pressure. It varies in different types of tissue (fat, collagen and so forth) and in the same tissue in different pathologic states (inflammatory, malignant). During the past few years, sonographic elastography, magnetic resonance elastography and some other techniques have performed digital measurements of tissue hardness. http://www.eusjournal.com/article.asp?issn=2303-9027;year=2014;volume=3;issue=1;spage=58;epage=62;aulast=Okasha - ref1 Two techniques of elastography have evolved 1) Strain elastography (SE) 2) Shear Wave elastography (SWE) US elastography Strain scoring (patterns) system for Lymph Nodes(LN) and Thyroid masses Score 1: The entire LN is red or green, i.e., soft. Score 2: 80% or more of the cross-sectional area of the LN is red or green, i.e., soft. Score 3: 50% or more and less than 80% is red or green. Score 4: 50% or more and less than 80% is blue; and Score 5: 80% or more of the cross-sectional area of the LN is blue i.e., hard. Shear Wave Elastography SWE provides quantitative elastic information on the basis of the acoustic pulse of a US probe that stimulates tissues, thereby producing a real-time elastogram. Sonographic elastography in the neck can be primarily used to evaluate pathologies involving Lymph nodes (LN), thyroid nodules and salivary gland nodules http://www.eusjournal.com/article.asp?issn=2303-9027;year=2014;volume=3;issue=1;spage=58;epage=62;aulast=Okasha - ref4. Differentiation between reactive and metastatic lymphadenopathy is vital and one of the differentiating criteria is hardness (elasticity) of the mass. LYMPH NODES LNs that have sonographic criteria suggestive of benign nature and had elastography score of 1 hence biopsy is not indicated and the diagnoses is based on follow-up with the minimum period of 12 months. In LNs with score 2, if clinical or sonographic suspicion existed the LN was subjected to histopathological examination, but in case of low suspicion a follow-up policy can be adopted to avoid unnecessary invasive procedures. All LNs with score 3 and 4 are subjected to histopathological examination either by biopsy or FNAC. Thyroid Nodules Using strain criteria in a study by Rago differentiating benign nodules from malignant ones was a mean elasticity index of 65 kPa on SWE. The sensitivity and the specificity for malignancy were 51.9% and 97% in the case of gray-scale US and 81.5% and 97.0% in the case of the combination of gray-scale US and SWE. SWE: Sebag et al.in a study of 146 thyroid nodules form 93 patients, the cut-off point for discriminating benign nodules from malignant ones was a mean elasticity index of 65 kPa on SWE. The sensitivity and specificity for malignancy were 81.5% and 97.0% in a combination of gray-scale US and SWE, respectively While elastography is a promising technique in some organs such as the breast and the liver there have been conflicting results of its additional value in predicting thyroid malignancy and Lymp Node charachterisation