MRI or the Magnetic Resonance Imaging is a technique for obtaining images of organs for medical diagnosis without having to resort to surgery. The technique uses the phenomenon of Nuclear Magnetic Resonance (NMR). Through MRI it is possible to differentiate between the various types of soft tissues. This gives it an edge over X-ray photography. For obtaining the images, the property of certain substances which selectively absorb energy when irradiated by electromagnetic radiation is used. The nuclei of certain atoms behave like tiny magnets. When substances with such atoms are placed in a magnetic field and continuously irradiated by electromagnetic waves of varying frequency, there comes a frequency called resonance frequency when a part of the electromagnetic energy is absorbed by the substances. The value of the resonance frequency is proportional to the intensity of the applied magnetic field and the nature of the substance that exhibits nuclear magnetism.
