Magnetic Resonance Imaging (MRI)
MRI stands for magnetic resonance imaging. The detected signal in MRI is obtained from the protons, most often the hydrogen protons, in the various tissues within the body. These protons create a net magnetization when they are subjected to a strong static magnetic field. The static magnetic field will align protons parallel and anti-parallel to the magnetic field. Once the net magnetization is achieved, a radio frequency pulse that is emitted to the body through the coils in the magnet, will tip the protons into the transverse plane. The recovery and decay of the net magnetization is eventually observed and is the basis for the signal collected. Simply then there is resonance which the nuclei of the hydrogen atoms within the water molecules are precessing at the Larmor frequency followed by relaxation, exponential recovery (contrast is ) and exponential decay (contrast is ), and last but not least spatial encoding and reading k-space lines.