TI-RADS classifies thyroid nodules into five grades according to their ultrasound characteristics. Grade 1 to 3 are generally benign thyroid lesions, such as thyroid cysts and nodular goiters. Except for nodules that are too large and produce pressure symptoms, follow-up is usually recommended. For nodules of grade 4 or above, thyroid aspiration is usually recommended for nodules with a diameter of 0.5 cm or more to clarify the nature of the nodule.