Magnetic resonance imaging (MRI) is a non-invasive imaging technique used in hospitals and clinics to produce detailed soft tissue anatomical images without exposing the body to radiation such as that used in X-rays and computed tomography (CT) scans. It is a medical application of nuclear magnetic resonance (NMR).
Magnetic resonance imaging can be used for diagnostic, disease staging, treatment and prognostic purposes. An MRI scanner works through emission and absorption of energy of the radiofrequency range of the electromagnetic field by employing powerful magnets that produce a strong magnetic field around the area to be imaged. People with non-removable metal implants are unable to undergo an MRI due to this reason.
Strong magnetic fields are used to align the polarity of hydrogen atoms and radio wave pulses are used to knock the atoms of axis, causing them to resonate, creating detectable radio-frequency signals can are received by detector coils placed in close proximity to the anatomy being imaged. Hydrogen atoms in MRI can are used to delineate water and fat. The MRI image reconstructions are basically maps showing concentrations of water and fat inside the body.
MRI machines require specialized technicians with extensive training including clinical experience, licensure, and certification from the American Registry of Radiologic Technologists.
An MRI with contrast is used when diagnosis requires imaging of specific tissues. Approximately 1 in 3 MRIs require contrast using gadolinium dye, administered via injection to the patient.