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 (PTCs) (Fig. 3). Incidentally detected cancers tend to be smaller in size and less likely to have distant metastasis, as compared to clinically suspected thyroid cancers. On CT scans, a malignant lesion is suspected when the margins are ill-defined and there is extra-thyroid extension, lymph node involvement, or invasion of the surrounding structures. The absence of these features does not exclude malignant tumours, especially papillary, follicular, and medullary thyroid carcinomas (Fig. 3). Therefore, ultrasound is the modality of choice for thyroid lesion evaluation, due to its superior spatial resolution compared to CT examinations. Sonographic features of malignancy are micro-calcifications, acoustic