Computed tomography of the thyroid gland.

Many imaging modalities are used in the investigation of the thyroid gland. In this multitude of methods, none of the applied modalities per se is able to discriminate between the benign or malignant nature of a thyroid lesion with absolute certitude. In this thesis, CT-imaging in various conditions of the thyroid gland is described. At the same time, the advantages and the risks of the application of free iodine as selective contrast agent for thyroid imaging in selective cases is studied. In chapter II a review of imaging modalities is described. A survey is given of the value of each imaging modality for the daily routine practice. In chapter III, relevant technical aspects of CT scanning with respect to the thyroid investigation are highlighted. These include technical possibilities typical for CT-scanning, dosimetric aspects and the patient preparation protocol. The CT-scan procedure is described for the neck region and the mediastinum. Chapter IV summarizes some important aspects of the iodine metabolism of which the radiologist should be aware. Chapter V describes the advantages of our scanning method in different patient groups. Evidence is obtained that CT-investigation of patients with a MEN 2-syndrome in the early assessment of tumor localization is of value. Application of CT in patients with a scintigraphically demonstrated cold nodule is shown to have consequences. Refinement of this diagnosis is possible and of additional value. The appearance of a multinodular goiter on CT is shown to be characteristic. Typical CT-features of this lesion are described which makes a strong indication in the direction of the histological diagnosis possible. With respect to the mediastinal masses of unknown origin, CT-signs of these lesions are considered. CT-examination can differentiate between goiters, benign cysts, infiltrative lesions and enlarged lymph nodes. Some attention is paid to future technical developments of CT, i.e., dual energy scanning. Early experiences are promising, especially in the field of thyroid imaging.