Functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) is a relatively new technique for imaging changes in brain haemodynamics linked to local neuronal activity. It does not entail exposure to radioactivity and has other important technical advantages over previously available methods for mapping functional neuroanatomy, such as positron emission tomography. It is likely that fMRI will become an increasingly important and widely used technique for psychiatric research in the next 5 years; applications to clinical practice are also conceivable. Here we review the technical foundations of fMRI. We begin with a brief summary of the basic physical principles of magnetization and nuclear magnetic resonance. This is followed by a description of some commonly used procedures for magnetic resonance imaging in general; an introduction to exogenous and endogenous contrast agents; and a section on gradient echo echoplanar imaging for fMRI specifically. We describe common artefacts and essential hardware requirements. Then issues of experimental design and data analysis are discussed in conclusion. Given the rapid rate of scientific progress in this field, this review can be no more than introductory. References to some supplementary textbooks and specialist journals are provided as guides to further reading.