Principles and Features of Magnetic Resonance Imaging

<p>Magnetic resonance imaging (MRI) is a technique based on nuclear magnetic resonance. In clinical MRI, the hydrogen nucleus, which consists of a single, positively charged proton, is the object of imaging. This allows the various signals from hydrogen nuclei in different tissues to be visualized. There is no risk of exposure to radiation during an MRI examination because ionizing radiation is not used. In addition, compared to computed tomography (CT), MRI has superior contrast resolution of soft tissues. Therefore, MRI is widely used as a non-invasive imaging method that produces excellent soft tissue contrast, and the number of MRI examinations is increasing year by year.</p><p>However, because MRI uses powerful magnetic fields, there have been numerous cases in which ferromagnetic materials, which are attracted to the magnetic fields, have led to medical accidents. Therefore, great care must be taken not to bring ferromagnetic materials into the exam room, and metals on or inside the body must always be checked for compatibility with MRI before the examination.</p><p>Recently, the use of cardiac pacemakers and defibrillators that are compatible with MRI examinations under certain conditions has been increasing. Since MRI is the most useful imaging method for the diagnosis of oral lesions such as oral tumors, salivary gland diseases, and temporomandibular joint disorders, it is desirable to use MRI-compatible materials in dental treatment. This review outlines the principles and features of MRI.</p>