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What is MRI?

What is MRI?

Since its inception in 1946, MRI techniques have been dramatically improved. What started out as largely an analytical tool, improvements to static magnetic fields; gradient magnetic fields; and radio frequency (RF) transmitter and receiver capabilities, have contributed to our ability to perform biological imaging with the technique.

The four major processes that are needed for the creation of in-vivo biological imaging are: (1) familiarity of elements of interest to possess spin and abundance (2) a very strong magnetic field (typically to the order of 0.5 Tesla to 3.0 Tesla in field strength), which is used to align spinning element orientation with that of the magnetic field direction (3) the ability to deliver a radio frequency pulse (RF) at the frequency appropriate for the element that it's designed to disturb from equilibrium (4) appropriate receiving devices in order to collect the signal as the elements return to their positions of equilibrium.

Most of the clinical imaging is done with the hydrogen proton (which has the ability to spin) largely because of its abundance. To the left is an example of a cross section (transaxial slice) of a human liver. Below the liver image is a longitudinal cross section (sagitlal slice) of a human knee. Some things that can change the dynamic range of pixel intensities in MRI are determined by: population density of protons, biological environment conditions, pulse sequence selection and settings, and utilization of MRI contrast agents.

The greatest successes have come from environments where the complementary nature of different imaging approaches has been realized. The Magnetic Resonance Imaging & Spectroscopy Center (MRISC) at the University of Kentucky represents a multidisciplinary team of clinicians, physicists, engineers, computer scientists, and technologists to advance in technical aspects of diagnostic imaging, applications to patient care, and applications for fundamental medical science. For an introduction to them, visit them in research and faculty/staff sections of this website.