Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) is a medical procedure used to view geometry within the body that is not observable from the exterior. MRI uses the principle of nuclear magnetic resonance to create images of the body. MRI uses strong magnetic fields to align the spin directions of the protons within hydrogen atoms.  At the same time, radio waves are used to create a varying magnetic field that can cause the protons to flip their spin direction. When the field is turned off, the protons gradually return to their natural spin directions. This produces a signal that is detectable by the MRI device.

MRI is sensitive to the spin of direction of the protons at the nucleus of hydrogen atoms. Hydrogen atoms are very common in the human body with two in every water molecule and multiple hydrogens in fats, sugars, and other hydrocarbons. This enables the MRI to differentiate between most of the tissues within the human body.  It is especially known for its sensitivity to soft tissues such as those within a joint, the brain, and other soft organs.  Furthermore, MRI is considered safe because it does not use ionizing radiation.

Despite these advantages, there are also some disadvantages of using MRI over the other technology used to generate 3D body images, computed tomography (CT). The time needed to scan the body is much higher with MRI (30–60 minutes) than CT (seconds or a few minutes).  MRI also has lower resolution than CT.  Like many competing technologies, the choice of imaging device depends on the application.