There are no special requirements for how often MRI exams should be done at intervals, because although MRI is an imaging test, it is different from diagnostic techniques that use radiographic imaging. Magnetic resonance examinations mainly use the nuclei of hydrogen atoms in human tissue cells, which change in motion within a powerful magnetic field, and then complete the images for diagnosis through a series of processing by magnetic resonance instruments. The MRI is not like CT, which can produce ionizing radiation to the human body through radiation imaging. Therefore, from a health perspective, there is no problem with how often MRI is done.