Parkinson's disease and PET tracer studies

Although the cause of Parkinson's disease is still unknown it has become clear that dopaminergic cell loss in the substantia nigra is a prominent feature of the disease. The study of cerebral dopaminergic function-dominated by the nigrostriatal system-in relation to motor abnormalities and their response to treatment has been in the centre of research for many years. However, until recently it was not possible to approach metabolism or neurotransmitter function in brain directly in vivo. To be able to do so seems highly necessary since Parkinson's disease is a slowly progressive condition and one wishes to know how cerebral functions are deranged in the beginning of the disease. Positron emission tomography (PET) using specific tracers (labelled with short-lived radionuclides like oxygen-15, carbon-11 or fluorine-18) can measure certain physiological or biochemical functions focally in brain directly in patients or healthy volunteers (for an extensive overview, see Phelps, 1986).