Explain the basic principles of MR image production Essay

Explain the basic principles of MR image production - Essay representativeThe frequencies absorbed in magnetic resonance are in the megahertz (million cycles per second) and gigahertz (billion cycles per second) ranges. The absorption frequencies for any particular substance are directly proportionate to the strength of the magnetic field. This characteristic is unique to magnetic resonance.There are two distinct subcategories of magnetic resonance. One of these, for which the absorbing particles are electrons, is known by either of two interchangeable names electron spin resonance (ESR) or electron paramagnetic resonance (EPR). The other category, in which the absorbing particles are atomic nuclei, is called nuclear magnetic resonance (NMR).2The resonances are actually the absorptions of particular frequencies and are found in EPR and NMR arises from some of the most fundamental properties of matter. A general theory of EPR and NMR must be derived from quantum mechanics, but a cla ssical analogy provides some insight. In the familiar model, every atom has a massive nucleus containing N positively charged protons and a number of uncharged neutrons. Outside the nucleus are N negatively charged electrons in various orbits or distributions. The number N, called atomic number, identifies the atom in the periodic table. 3Every electron and proton possesses, in addition to charge and mass, an indestructible enumerate of angular momentum or spin, the property that keeps a gyroscope spinning after the driving force is removed. Because moving charge always has magnetic effects, the cabal of charge and spin makes every electron and proton a spinning permanent magnet, the strength or magnetic moment being several hundred multiplication greater for electrons. A spinning electron can be compared to the spinning wheel of a toy gyroscope. When the gyroscopes spin axis is off vertical, and the bottom terminate of the axis rests loosely on a support, the unexpected happens. Instead of falling farther from the vertical under the force of the wheels weight, the spin axis rotates steadily some the vertical at a fixed angle from it, a motion known as precession. In EPR the electron is spinning and a microscopic magnet. The outwardly applied magnetic field supplies the extra force, and the electrons spin axis precesses. Resonant absorption occurs when the source frequency is synchronous with the precession frequency. A similar accounting applies to NMR. 4Magnetic Resonance Image ProductionFigure 1 illustrates the a simplified block diagram of generic MR imaging mechanism demonstrating the elements natural for the recognition and creation of MR signals and the demonstration of MR images. These components are as follows1) The RF mechanism (a) for the production of the magnitude of the RF magnetic field with the help of a spin for transmitting mode, amplifier and a transmitter, b) for the detection of the free induction decay (FID), which is the result of the net magnetization to an RF pulse this is done by the help of a signal demodulator, a coil for