Fluor-18-deoxyglucose positron emission tomography in differentiated thyroid cancer.

Owing to the development of high resolution scanners and the new possibility of whole body scanning in recent years positron emission tomography has become more and more important in diagnostic imaging, especially for the diagnosis of malignant tumors and their metastases. Positron emission tomography (PET) is a special nuclear medical imaging technique, which is quantitative (correcting for radiation absorption by transmission measurements), and tomographic (imaging primarily a transversal body section as a tomographic field of view, i.e. a volume in time (4D) for a kinetic analysis or a sequence of fields of view to obtain whole body data sets). The radionuclides used emit a positron which is converted into a pair of photons after a short path of a few millimeters in the tissue (‘annihilation event’). The coincidence detection of the two photons, which are travelling on a line in opposite directions permits a sensitive electronic collimation as a first step in the localisation of the site of the radionuclide decay (see Fig. 1). With positron emitters of biochemically interesting elements such as carbon-11 (C), oxygen-15 (O), European Journal of Endocrinology (1998) 138 492–496 ISSN 0804-4643