Computed tomography of the thyroid ,88 and and9).9). CT scans are also the most sensitive diagnostic tool for the detection of pulmonary micro-metastases. Many of the neck US features that are considered as suggestive signs of disease recurrence are also applicable to CT examination. These signs might include sizable rounded nodules in the thyroid bed, fine calcifications, or cystic change. In cases of elevated thyroglobulin with negative neck US and iodine whole body scintigraphy (WBS), fluorodeoxyglucose (FDG) positron emission tomography (PET) is the next modality of choice. Dedifferentiated thyroid carcinoma usually has avid FDG-PET uptake and a negative radioiodine scan, typically does not respond to
Computed tomography of the thyroid of normally sited thyroid gland in US and CT scans also supports the diagnosis. In addition, US can guide FNA for cytological confirmation of a thyroid lesion. Ectopic thyroid tissue appears as a well-circumscribed, homogeneous, highly attenuating mass relative to adjacent muscles. Normally, it enhances avidly following the administration of iodinated contrast. Ectopic thyroid tissue may be detected in the tongue near the foramen cecum (90 %) and along the midline between the thyroid isthmus and posterior tongue, lateral neck, mediastinum, and oral cavity. The most frequent location is the base of the tongue (Figs. 16, ,1717 and and18).18). In