Positron Emission Tomography (PET) is a nuclear medical imaging technique that produces a three-dimensional image of functional processes in the brain. The PET device detects pairs of gamma rays emitted indirectly by a tracer, which is introduced into the body on a biologically active molecule. A CT scan is also acquired during the PET scan.

 

Fludeoxyglucose PET (FDG-PET) is the most common type of PET, which uses biologically active molecule called [18F]FDG, an analogue of glucose. The concentration of [18F]FDG indicates tissue metabolic activity. We use this technique to measure the different patterns of glucose metabolism in the brain along the recovery process from severe brain injury and to evaluate longitudinal changes in individual cases.

Raclopride PET is another kind of PET that uses a ligand that specifically binds to a subclass of dopamine receptors of the brain. [11C]raclopride-PET evaluates the bioavailability of dopamine-2 like receptors within the striatum and extrastriatal structures of the brain. Analysis of the acquired signal allows quantification of the status of the dopaminergic system at the postsynaptic level. In addition, when [11C]raclopride-PET is combined with a single dose of amphetamine, a compound that blocks the reuptake of dopamine from the synaptic cleft, it is possible to quantify the dopaminergic presynaptic response. We use this technique to measure the presynaptic and postsynaptic status of the dopaminergic system in patients with severe brain injury with the aim to improve current therapeutic approaches.