MRI is the safest imaging clinical imaging technique that is used for a variety of medical purposes like differentiating between normal and pathological tissues for diagnosis and tracking dynamic changes in tissue properties over time.
Magnetism is physical phenomenon in which materials and moving charged particles can attract or repel other materials or moving charged particles (Ballinger, Intro to MRI, 1998). Magnetism results from moving electric charges or intrinsic spin moments of electrons or nucleis. Spin is a quantum mechanical property. This means that the available spin energy levels are constrained to specific, discrete values. A spin 1/2 particle has only two possible spin states: spin up (+ 1/2) or spin down (- 1/2). The magnetic moment is aligned with the spin. The spin-up and spin-down states are described as being equal in energy, or degenerate. However, if another magnetic field is introduced, the spin-up and spin-down states will be no longer equal in energy. The energy difference introduced by applying the external magnetic field is known as the Zeeman splitting (van Geuns, 1999). This effect is very important in such applications as magnetic resonance imaging. Magnetism can be classified as paramagnetism, diamagnetism, ferromagnetism, and antiferromagnetism (Ballinger, Intro to MRI, 1998).
Having microscopic magnetization, protons within a magnetic field produce wobbling as they spin. The rate of this wobbling or precession constitutes resonance or Larmor frequency (Intro to MRI). The application of a radio frequency pulse at the Larmor frequency causes a change in the distribution of spins with respect to their energy state and precessional phase coherence (Rodr´ıguez, 2003). Practically, it means that If individual nuclei is exposed to RF radiation at the Larmor frequency, nuclei in the lower energy state jumps to the higher energy state (Intro to MRI). Upon