Ultrasound is performed to: assess the status of the thyroid bed and lymph nodes in the central and lateral cervical regions of the neck. Ultrasound is highly sensitive for early detection of neck metastases in patients with DTC and is an important component of follow-up. It is recommended that the frequency of neck ultrasound during the follow-up of DTC is: every 3-6 months within the first year after surgery or 131I treatment; thereafter, every 6-12 months for disease-free survivors; if suspicious lesions are found, the examination interval should be shortened as appropriate. Puncture biopsy may be performed on suspicious cervical lymph nodes detected by ultrasound. Studies have shown that measuring the Tg level of the puncture needle rinse after puncture of the suspicious lymph nodes improves the sensitivity of detecting DTC metastases.