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During recent years much effort has been put into detecting and classifying disease states, and MR imaging has been a very important tool in this respect. Up to now, increasing the gradient strength has been the only strategy for meeting the increasing demands of advanced diagnostic imaging applications. This strategy is limited by physical, economic, andmedical considerations: increasing gradient strength is technically difficult, and is associated with significant hardware costs and with the risk of inducing unwanted side effects such as peripheral neurostimulation. The main advantage of high-field MR is the improved signal-to-noise ratio, which scales approximately linearly with field strength from 1.5 T to 3 T. This signal can be used to generatemore accurate spatial representation or to speed up imaging times, depending on the specific application. Higher field strengths change tissue contrast parameters. T1 relaxation time is increased by approximately 30%, whereas T2 and T2* relaxation times are decreased by about 15% [37]. Increasing the field strength from 1.5 T to 3 T also doubles chemical shift and susceptibility. MR spectroscopy benefits considerably from the improved spectral resolution possible with high-field MR, and images acquired on 3 T MR demonstrate enhanced sensitivity to the blood oxygen level-dependent (BOLD) effect [77]. On the other hand, tissue heating induced by radiofrequency power is a disadvantage with the use of 3 TMR. In fact, specific RF absorption rate approximately quadruples when field strength increases from 1.5 T to 3 T. The most recent attempt to circumvent these limitations is parallel imaging MRI.

fMRI has proved to be a reliable, safe, reproducible method with which to presurgically define eloquent areas. This technique gives us the opportunity to know in advance the actual situation of a lesion so that the surgeonsmay plan their approach strategy. This technique also allows the establishment of a presurgical evaluation of risk and enables the patient to be fully aware at the moment of informed consent. Despite the increase in its clinical applications, fMRI is still underused in the clinical field and should be performed almost routinely before surgery.

The use of high magnetic field strength fMRI units has the potential for improving considerably the sensitivity and specificity of functional studies. As a result of the high-field studies, fundamental neural dynamics taking place at a very small dimensional scale in specific laminar, columnar and multicolumnar domains have become directly visible. The advantages in terms of spatial resolution, temporal resolution, BOLD signal changes and noise behaviour depend on the acquisition sequence and on the practical combination of the acquisition parameters with the local microscopic brain structure. Nevertheless, high-field units can be expected to improve significantly the quality of the fMRI results and the level of neurophysiological information it is possible to gather from the data. The concurrent use of tailored processing strategies can make even more convenient the use of high-field systems.