Thyroid Ultrasonography—A Review

Abstract

To review the major applications of ultrasonography in studies of the thyroid gland by clinical endocrinologists. The techniques for performance of thyroid ultrasonography and ultrasound-guided fine-needle aspiration biopsy are outlined, and the settings for their use are discussed. Characteristic findings and limitations are described. In two situations--the assessment of thyroid nodules and the postoperative follow-up of thyroid cancer--ultrasonography and ultrasound-guided fine-needle aspiration biopsy have proved to be clinically useful when used in combination. On ultrasonography, a hyperechoic nodule with a sharp "halo" is associated with a low risk of malignancy and a hypoechoic nodule with microcalcifications is associated with a high risk of a malignant lesion, but performance of a biopsy is recommended. Ultrasonography coupled with ultrasound-guided fine-needle aspiration biopsy can detect >90% of recurrent cases of thyroid carcinoma. In general, normal lymph nodes appear flattened on ultrasonography, whereas malignant nodes appear more rounded or bulging. Thyroid ultrasonography and fine-needle aspiration biopsy are complementary diagnostic procedures in the evaluation of thyroid nodules and for detection of recurrent or metastatic thyroid carcinoma.