MRI Fundamentals: RF Aspects of Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) is an imaging technique based on the nuclear magnetic resonance (NMR) phenomenon and provides a means of obtaining detailed, high-contrast images for use by the medical community for diagnostic purposes. MRI differs from other imaging technologies such as single-image X-ray computed tomography scans in that the technique uses nonionizing radiation, relying on static and slowly changing magnetic fields and electromagnetic (EM) energy (primarily in the high-frequency through very-high-frequency bands) to provide soft- and hard-tissue images with outstanding contrast that can be both static and dynamic in nature. High-resolution images of soft tissues from MRI can be obtained even though the wavelength of the EM energy is much larger than the feature size because the MRI process makes use of complex, spatially encoded, reradiated EM signals from the region of interest (ROI) rather than looking at the scattered energy on which other imaging techniques are based.