When a nodule appears in the thyroid gland, it is necessary to determine whether the nodule is benign or malignant. Routine ultrasound examination of the thyroid gland can be used to make a preliminary determination of benign or malignant. The size of the nodule can be directly described by ultrasound, so the longitudinal and transverse diameters of the nodule are measured to determine the size. Nodules are graded into 6 levels, with grades 1-3 suggesting benign lesions, grades 5-6 suggesting malignant lesions, and grade 4 between benign and malignant lesions, which require further investigation, either through follow-up or fine-needle aspiration for pathologic examination. The grading of the nodule is based on the texture, echogenicity, border, the presence of punctate calcification and abnormal blood flow signal, and the aspect ratio of the nodule.