Application Value of Contrast-enhanced Ultrasound-guided Fine-needle Aspiration Biopsy in the Evaluation of Thyroid Nodules

Thyroid nodules and thyroid cancer are common and frequently occurring diseases in China; Relevant researches reveal that the increase in the incidence of thyroid cancer is more prominent in China than that of overseas, the incidence of thyroid cancer in urban residents of Beijing increased from 1.55/100,000 in 1995 to 9.9/100,000 in 2010 (5.38 fold).

The rapid development of imaging techniques including ultrasound, CT and MRI had substantially increased the accuracy in the diagnosis of thyroid nodules, however the accuracy is still not up to 100% and a further aspiration biopsy is required. Therefore, ultrasound-guided percutaneous biopsy plays a critical role in the diagnosis of pathological lesions. Many guidelines deem fine needle aspiration (FNA) biopsy to be the most accurate and cost-effective examination method in the evaluation of thyroid nodules as it helps to reduce unnecessary thyroid nodule surgeries and it also helps the clinicians to determine the appropriate surgical treatment plan[1-4]. However according to literature reports, samples with insufficient quantity of cells can occur up to 10-15% of the cases, sometimes a second biopsy or a diagnostic operation needs to be performed[1,4].False negative results of FNA biopsy or a mismatch between ultrasound diagnosis and clinical diagnosis can occur due to a number of reasons such as the tumor being too big or too small, a poor location, presence of degenerative necrosis, inappropriate position of biopsy or be affected by the operator's experience etc.

Contrast-enhanced ultrasound (CEUS) is a new technology which is recently introduced into China, it has the ability to display the microvascular perfusion of the tissue under a low mechanical index. The serial real-time images obtained can be digitalized and dynamically stored. And this allows for retrospective analysis and also enables comparison to be made with other imaging techniques. CEUS can sensitively reflect the characteristics of blood supply and microcirculation at the site of the lesion.

Although CEUS-guided FNA of thyroid nodules has not yet been reported, a large number of studies have reported liver biopsy performed under the guidance of CEUS. Its efficacy in obtaining accurate diagnosis and in reducing the number of biopsies is clear when samples are taken from the area of rich blood supply.

Metabolic-active areas within the malignant tumor, or areas of degeneration or necrosis and also the detection of small tumors can be confirmed through the use of CEUS. Aspiration biopsy when performed under the guidance of CEUS is expected to yield decreased non-diagnostic result. The investigators intent to create a randomized controlled study to investigate the application value of CEUS in the diagnosis of space-occupying lesions of the thyroid using FNA.