Noble gas MRI

Article By:

Chupp, Timothy E. Department of Physics, University of Michigan, Ann Arbor, Michigan.

Swanson, Scott D. Department of Physics, University of Michigan, Ann Arbor, Michigan.

Last reviewed:2004

DOI:https://doi.org/10.1036/1097-8542.YB040550

Magnetic resonance imaging (MRI) has been a key tool in medicine and biomedical research for more than two decades. In conventional MRI, two-dimensional images of thin slices of tissue are created by measuring the nuclear magnetization of protons (the nuclei of hydrogen atoms) in tissue in the presence of static and oscillating magnetic fields. Generally, a strong static field, typically 1.5 tesla, produces the nuclear magnetization, which is due to a small excess of protons with spin-up (parallel to the static magnetic field) compared to spin-down (opposite the static magnetic field). This excess, called the nuclear polarization, is only about 10 parts per million but, combined with the high concentration of protons in tissue, produces the remarkable images used by physicians and scientists. Nuclear magnetization, the product of nuclear polarization and concentration, sufficient for MRI with much lower concentrations characteristic of gases can also be produced with lasers. This laser technique, called optical pumping, has led to new methods of imaging called laser-polarized noble gas MRI or hyperpolarized gas MRI.

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