Endocrine Abstracts

Positron emission tomography (PET) is an imaging technique that enables direct observation of tissue radioactivity concentration over time in vivo. Unlimited number of natural substrates (e.g. glucose, fatty acid), substrate analogs can be labelled for use with PET. PET combined with tracer kinetic models measures blood flow, membrane transport, metabolism, ligand receptor interactions and recently also gene expression noninvasively and quantitatively.

An abnormal action of insulin and handling glucose and fatty acids in muscle, heart, liver, brain and visceral and subcutaneous adipose tissue have been studied in vivo in humans. This tissue specific assessment has increased the understanding of the pathophysiology of metabolic syndrome, obesity and diabetes and the differences in tissue specific action in vivo. The effects of insulin, free fatty acids, exercise and diet have been evaluated. PET is powerful tool for the assessment of tissue specific action of drugs targeted to metabolic disorders. The hybrid PET/CT scanners enable correlation of anatomic and functional information.

The clinical use of PET is rapidly expanding. In addition to (18)F-labelled deoxyglucose (FDG) which is routine used in oncology for diagnosis of cancer, many more specific tracers have been shown to improve diagnostics of neuroendocrinological tumours (NETs). The most promising of those is (18)F-fluorodihydroxyphenylalanine (FDOPA). It appears to be more useful in carcinoid tumours than scintigraphic imaging and might replace it. It is more sensitive than CT or MRI in detection of insulinomas and has quickly replaced other methods in the assessment of focal form of congenital hyperinsulinism of infancy (CHI). FDOPA-PET improves diagnostics and prediction of prognosis, and be used to assess patients’ response to treatment for NETs.