Hardware considerations for functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) techniques based on changes in blood oxygenation or regional cerebral blood flow or volume have had great impact in mapping the regions of the brain that are activated by specific stimuli. The basic strategy of fMRI paradigms is to acquire data during two different brains states: one state usually comprises a resting condition, while in the other state the subject is performing a specific sensory or cognitive task. The signal difference between the activated and resting signals is on the order of only a few percent, and therefore the reliability and reproducibility with which it can be detected limit both the temporal and spatial resolution of fMRI experiments. The era of fMRI has significantly contributed to advancing the state of the art of MRI scanners. Every hardware component in modern MRI scanners, from the magnet itself to the gradient, shim, and RF coils to peripheral stimulus delivery equipment, has been (re)designed to perform to the limit of currently available technology and to improve the quality of MRI data, particularly fMRI data. The current state of the art of MRI scanners is described in light of their use in fMRI experiments. (C) 2003 Wiley Periodicals, Inc.