Computed tomography of the thyroid bone, before it loops posteriorly and inferiorly to the hyoid bone. Then it continues its descent into the infra-hyoid portion of the neck, anterior to the trachea, thyroid cartilage, and thyroid membrane. Any thyroid residual along the descent course may lead to the development of ectopic thyroid glands. Thyroid carcinomas, thyroiditis, and goiter may develop within any ectopic thyroid tissue. Thyroid scanning with technetium-99 m (Tc99m) plays an important role in detecting orthotopic and ectopic thyroid tissue. Both CT scans and US can help detect ectopic tissue when a lesion demonstrates imaging and enhancement characteristics of thyroid tissue. The absence
Computed tomography of the thyroid stage is classified by site: N1a indicates level VI nodal involvement, including paratracheal nodes; N1b indicates unilateral or bilateral lateral cervical nodal disease or superior mediastinal nodal disease (Figs. 4, ,55 and and6)6). The incidence of hematogenous spread of follicular carcinomas is 21–33 % and that of PTCs is 2–14 %. In medullary thyroid cancer and anaplastic thyroid cancer, distant metastasis was reported in 25 % and 40 % of patients, respectively. Distant metastases from DTCs tend to have a more favourable prognosis. Distant metastatic disease may appear years after the initial presentation. Therefore, imaging for distant metastases is usually