Shear Wave Ultrasound Elastography in Noninvasive Diagnosis of Thyroid Nodules

Shear wave ultrasound elastography is a new technique of finding the softness or hardness in tissue by applying a "push" generated by the machine. This technique will help in diagnosing malignancy in the thyroid gland without biopsy and avoiding biopsy in noncancerous nodules.

Thyroid nodules are a common medical problem. With the wide use of various imaging modalities, incidentally detected thyroid nodules are becoming more common. However most of these nodules are benign with only a small proportion of 5-10% being malignant. With the increasing number of nodules detected, evaluation of these thyroid nodules presents a diagnostic challenge since the imaging modality used for evaluation at present, i.e., ultrasound (US) alone, has a low specificity of approximately 50-70%. In order to improve specificity to confidently diagnose malignancy in the thyroid nodule, a fine needle aspiration (FNA) biopsy is performed. In recent years, US elastography has been shown to have high specificity of 90- 98% in various studies in differentiating between benign and malignant nodules. US elastography works on the principle of detecting the stiffness within a tissue by applying compression which can be manual compression or by generation of a remote radiation force by focused ultrasonic beams called as shear waves. Shear Wave Ultrasound (SWUS) elastography is an objective method of US elastography that detects the stiffness within the nodule since the strength of the shear wave generated is known and can be controlled. SWUS elastography has shown promise in being able to noninvasively diagnose papillary carcinoma in previous studies involving preoperative patients. The investigators propose to perform a study to investigate the efficacy of SWUS elastography in diagnosing malignant thyroid nodules and noninvasively decreasing the number of FNAs performed by avoiding FNA in benign nodules. The Investigators will enroll patients with thyroid nodules before they undergo FNA biopsy or surgery. We also propose to compare routine US and SWUS elastography and their combined use in differentiating malignant from benign nodules. The investigators hypothesize that SWUS elastography can be used as a noninvasive screening tool, prior to an FNA, to screen out benign and malignant nodules with high level of confidence and reduce the number of biopsies in the future.

Thyroid Nodule, Thyroid Neoplasm, Differential Diagnosis, Elastography, Elasticity Imaging Technique, Sonoelastography

This is a noninvasive technique using focused ultrasonic beams (pushing beams.) Several pushing beams at increasing depths are transmitted to generate a quasi-plane shear wave frame that propagates throughout the imaging area. After generating the shear wave, an ultrafast imaging sequence is performed to acquire successive raw radiofrequency dots at a very high frame rate (up to 20,000 per second). A tissue elasticity assessment can be derived from shear wave propagation speed. A color-coded image is displayed; softer tissue in blue and stiffer tissue in red. Quantitative information is delivered by drawing regions of interest on the thyroid and surrounding tissues which is the Elasticity Index expressed in kilo-Pascal (kPa). Due to the lack of manual compression and known value of the strength of pushing beam, SWUS gives an objective number to stiffness within the nodule.

SWUS elastography can provide an objective score of stiffness, i.e., the Elasticity Index. Stiffness from the SWUS elastography will be correlated with the elasticity measured with an indentometer to validate the Elasticity Index. The Elasticity Index will also be correlated with the histopathologic diagnosis. The sensitivity and specificity of the method for the diagnosis of malignancy will be assessed.

Up to 2 months. A one-time SWUS elastography will be performed on Day 1 within 2 months prior to the patients scheduled clinical FNA or surgery.

The investigators will compare the SWUS findings to the routine US findings. This will help us develop criteria based on combined findings to decide if a thyroid nodule is suspicious enough to warrant a FNA biopsy. These criteria can then be used for future prospective studies.

Up to 2 months. A one-time SWUS elastography will be performed on Day 1 within 2 months prior to the patients scheduled clinical FNA or surgery.

Inclusion Criteria: Clinical diagnosis of thyroid nodule Referred for thyroid FNA or surgery Exclusion Criteria: Minors; age <18 Unable to provide informed consent

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