Computed tomography of the thyroid

In CT scan of the thyroid, focal and diffuse thyroid abnormalities are commonly encountered. These findings can often lead to a diagnostic dilemma, as the CT reflects nonspecific appearances. Ultrasound (US) examination has a superior spatial resolution and is considered the modality of choice for thyroid evaluation. Nevertheless, CT detects incidental thyroid nodules (ITNs) and plays an important role in the evaluation of thyroid cancer. This pictorial review covers a wide spectrum of common and uncommon, incidental and non-incidental thyroid findings from CT scans. It will also include the most common incidental thyroid findings. In addition, the role of imaging in the assessment of thyroid carcinoma (before and after treatment) and preoperative thyroid goiter is explored, as well as localization of ectopic and congenital thyroid tissue. Thyroid ultrasonography is the modality of choice for thyroid evaluation. Yet, focal and diffuse thyroid abnormalities are commonly encountered during the interpretation of computed tomography (CT) exams performed for various clinical purposes. For example, CT often detects incidental thyroid nodules (ITNs). It plays an important role in the evaluation of abnormal structures including thyroid cancer. Thyroid disorders are common and include many entities. They can be symptomatic, asymptomatic, diffuse, focal, neoplastic, or non-neoplastic processes. Neck ultrasound (US), with the prospect of proceeding to fine needle aspiration (FNA), is the first line of investigation; however, other options are available. Thyroid Uptake Scans using Tc-99 m or I-123 are typically reserved for specific clinical scenarios. Cross-sectional imaging including computed tomography (CT) and magnetic resonance imaging (MRI) detect incidental thyroid nodules (ITNs) and can be used in the evaluation of thyroid cancers and goiter. The aim of this article is to provide a pictorial review of a broad spectrum of incidental and non-incidental thyroid findings on CT scans.