High-field MRI of the central nervous system: current approaches to clinical and microscopic imaging.

Introduction of clinical high-field MRI has raised interest in the use of clinical imaging--the efficacy of which has not yet been fully established--in daily practice. A high signal-to-noise ratio and profound susceptibility effects can improve the spatial resolution and image contrast of clinical imaging, whereas the heating effects of the radio frequency tend to prolong acquisition time. As well, inhomogeneities in the static or local magnetic fields can have a negative effect on image quality. The T(1) prolongation may affect T(1) contrast yet improve the enhancement effect of gadolinium chelate and the inflow effect of MR angiography. High-contrast imaging, such as the short inversion-time inversion recovery technique, can provide excellent intra- and extracerebral contrast comparable to microscopic or macroscopic specimens. High-field systems can also be applied to microscopic imaging. High-field MRI is expected to have an increased clinical impact in the near future. Technological advances tailored to high-field systems, as well as the accumulation of scientific evidence, will be necessary to establish its predominance over conventional MRI.