MRI scan

Magnetic resonance imaging (MRI) is a noninvasive imaging technique that enables the observation of anatomic structures, physiological functions, and molecular composition of tissues. MRI is based on the absorption and emission of energy in the radiofrequency (RF) range of the electromagnetic spectrum. It produces images based on spatial variations in the phase and frequency of the RF energy being absorbed and emitted by the imaged object. MRI is able to produce cross-sectional images of the body with excellent soft tissue contrast, and does not have any harmful ionizing radiation.

The basis of MRI is that certain atomic nuclei, typically those of hydrogen present in fat and water of human body, become magnetized when placed in an external magnetic field. By applying RF pulses, images can then be created based on the differences in signal from hydrogen atoms in different types of tissue. The versatility of MRI consists on several of many possible types of images that can be produced, where each type of image has a different image contrast or ‘weighting.’ Each contrast mechanism offers some unique information for the noninvasive detection, diagnosis, and characterization of disease.

The advantages of MRI over other imaging modalities include absence of ionizing radiation, superior soft tissue contrast resolution, high-resolution imaging, and multiplanar imaging capabilities. The time to acquire an MRI image has been a major weakness. Advanced imaging techniques used in medical imaging include MR angiography (MRA), diffusion-weighted imaging, chemical shift imaging (fat suppression), functional imaging of the brain, and MR spectroscopy (MRS). Patients in whom MRI is contraindicated include those who have the following: cardiac pacemaker, implanted cardiac defibrillator, aneurysm clips, carotid artery vascular clamp, neurostimulator, insulin or infusion pump, implanted drug infusion device, bond growth/fusion stimulator, and a cochlear or ear implant.