Which of the following is a functional investigation:

Ans. (d) PET scan* Positron emission tomography (PET) is a nuclearmedical imaging modality that produces a three-dimensional image of functional processes in the body* The most common indication for a PET scan is to detect cancer metastasis.* The technique operates on the principle of detecting gamma rays emitted indirectly by a positron-emitting radionuclide (tracer).* Three dimensional imaging is done with the aid of a CT X-ray scan performed on the patient during the same session.* The biologically active molecule chosen for PET is FDG (18-Fluoro deoxy glucose), an analogue of glucose, the concentrations of tracer imaged will indicate tissue metabolic activity by virtue of the regional glucose uptake.* ALSO REMEMBER: Functional magnetic resonance imaging or functional MRI (fMRI) is an imaging procedure that measures brain activity by detecting associated changes in blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled.