While MRI and X-ray are both imaging techniques for organs of the body, the difference is that MRI images provide a 3D representation of organs, which X-Rays usually cannot.
X-Rays are beams of high frequency (has a wavelength between 10 and 0.1 nanometers) of the electromagneticspectrum that can easily pass through low density (atomic number) material but not through materials that have high density. Therefore, solid objects like kidney stones and bones come out very clear in the X-Ray image.
MRI makes use of an oscillating magnetic field that is perpendicular to an extremely strong principle magnetic field along which the organ that needs to be scanned is placed. This oscillating field makes the hydrogen atoms within the organ to get magnetized in a direction that is perpendicular to the principle magnetic field.
X-Ray technology is used to employ radiography and other techniques for diagnostic imaging. X-Rays are useful to detect pathology of the skeletal system and to detect certain diseases in the soft tissue. For e.g. identification of pneumonia, pulmonary edema, lung cancer or abdominal X-ray are all effective. They are helpful in detecting gallstones or kidney stones.
MRIs are used for distinguishing pathologic tissue from the normal tissue. Unlike traditional X-Rays that use ionizing radiation, MRIs use non-iodizing radiation. MRIs offer excellent image clarity and different types of MRIs scans enable taking different images with a great clarity.