A Pilot Study Evaluating Real-Time Shear Wave Ultrasound Elastography of Miscellaneous Non-Nodal Neck Masses in a Routine Head and Neck Ultrasound Clinic

Abstract

A pilot study was performed to evaluate shear wave ultrasound elastography (SWE) for miscellaneous non-nodal/salivary/thyroid neck lesions. Forty-six lesions undergoing conventional sonography also underwent SWE. Elastic moduli from the stiffest areas in lesions were correlated with diagnosis. Forty lesions were benign (9 lipomas, 8 lymphatic/venous vascular malformations, 7 thyroglossal duct cysts, 4 branchial cleft cysts, 4 abscesses/phlegmons, 3 neurogenic tumors and 1 each of paraganglioma, sebaceous cyst, pseudotumor, hypertrophic scar, ranula) and 6 were malignant (1 malignant fibrous histiocytoma, 2 primary squamous cell carcinomas and 3 intramuscular metastases [2 squamous cell carcinomas, 1 malignant melanoma]).Median stiffness of malignant lesions (226.4 kPa, range 55.6 to 300.0) was higher than benign lesions (28.3 kPa, range 4.0 to 300.0) (p < 0.001). SWE cut-off with highest accuracy (174.4 kPa) achieved 83.3% sensitivity and 97.5% specificity, and the cut-off with 100% sensitivity (55.6kPa) achieved 75% specificity. All malignant lesions were suspected on conventional sonography. The preliminary data indicate that SWE is feasible for miscellaneous neck lesions. SWE would not have altered management in terms of detecting undisclosed malignancies, although as a quantitative technique, it may increase the diagnostic confidence of less experienced operators performing head and neck ultrasound.

Introduction

Non-nodal, nonsalivary and nonthyroid neck lesions most commonly present as painless neck masses. Because of their superficial location, high-resolution ultrasound (US) is an ideal initial imaging modality, and characteristic grey scale and Doppler ultrasound features of many of these lesions often permit an accurate diagnosis. Nevertheless, some lesions may be indeterminate on conventional US, and under these circumstances guided needle aspiration or biopsy or additional imaging investigations are required. Ultrasound elastography is a noninvasive technique to estimate tissue stiffness, and in the last few years has appeared as a research application on commercial clinical US systems. Most of these systems have used a method termed strain elastography, although more recently a newer method termed shear wave elastography has emerged.

Shear wave ultrasound elastography (SWE) uses acoustic radiation impulses (pushing pulses) to stress tissues and ultrafast US tracking techniques to measure the speed of induced shear waves (Bercoff et al., 2004, Tanter et al., 2008). From these data, Young’s elastic modulus (stiffness) is estimated (stiffness is proportional to the square of shear wave speed) and displayed in real-time as color-coded elastograms. In principle, SWE is superior to strain elastography because it allows more direct and quantitative estimation of Young’s modulus and is not dependent on external compressions by the operator or other mechanical or physiologic sources (Bercoff et al., 2004, Tanter et al., 2008, Athanasiou et al., 2010).

The oncological application of elastography uses the general observation that malignant tissues are stiffer than benign tissues. Medical literature reports on the use of ultrasound elastography in differentiating malignant from benign lesions in the breast, prostate, lymph nodes, liver, gastrointestinal tract, cervix and thyroid (Alam et al., 2008, Asteria et al., 2008, Bae et al., 2007, Garra, 2007, Hong et al., 2009, Itoh et al., 2006, Janssen et al., 2007, Lyshchik et al., 2005, Lyshchik et al., 2007, Rago et al., 2007, Saftoiu et al., 2006, Taylor et al., 2005, Thomas et al., 2007, Zhi et al., 2007). Nononcological applications of ultrasound elastography are also being evaluated in the liver, kidney, uterus and vascular and musculoskeletal systems (De Zordo et al., 2009, De Zordo et al., 2010, Garra, 2007, Takahashi et al., 2010). Preliminary findings show that SWE may help in the detection of malignancy in the breast and thyroid (Athanasiou et al., 2010, Evans et al., 2010, Sebag et al., 2010, Tanter et al., 2008). We previously reported on real-time qualitative US strain elastography of miscellaneous non-nodal neck masses (Bhatia et al. 2010). The aim of the present study was to assess the feasibility of performing SWE on non-nodal, nonthyroid, nonsalivary neck masses; document the range of SWE values according to lesion type; and evaluate its potential use in routine clinical practice, including for detection of malignancy. It was not the purpose of this study to document conventional sonographic appearances of miscellaneous neck lesions because this is already well documented in the literature.