Magnetic Resonance Imaging

Template:Infobox medical imaging Magnetic Resonance Imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to generate images of the organs in the body.

History

MRI was developed from principles discovered in nuclear magnetic resonance (NMR), a technique used by scientists to study the properties of atomic nuclei. The development of MRI as a medical tool began in the 1970s and was credited to the work of Dr. Raymond Damadian, who created the first MRI scan in 1977.

Principles

MRI uses a powerful magnetic field to align the nuclear magnetization of (usually) hydrogen atoms in water in the body. Radio frequency fields are used to systematically alter the alignment of this magnetization, causing the hydrogen nuclei to produce a rotating magnetic field detectable by the scanner. This signal can be manipulated by additional magnetic fields to build up enough information to construct an image of the body.

Applications

MRI is widely used in hospitals and clinics for medical diagnosis, staging of disease, and follow-up without exposure to ionizing radiation. It is particularly useful for the imaging of the brain, muscles, the heart, and cancers as compared with other medical imaging techniques such as computed tomography (CT) or X-rays.

Safety and Contraindications

While MRI does not involve any ionizing radiation, its strong magnetic fields may be harmful or lethal to individuals with certain implants such as pacemakers. Patients with various implants, cochlear implants, and certain metallic foreign bodies may not be suitable candidates for MRI due to the risk of magnet-induced injury.

Advancements

Recent advancements in MRI technology include high-field MRI, with systems up to 7 Tesla, and developments in fast imaging techniques such as echo-planar imaging. Functional MRI (fMRI), which measures signal changes in the brain that are due to changing neural activity, is also a significant advancement.

See Also

• Computed Tomography
• Ultrasound Imaging
• Positron Emission Tomography