Abstract
MRI is a medical imaging technique based on the effect that hydrogen protons in tissues exposed to an external magnetic field produce a rotating magnetic field (so called spin) detectable by the scanner. Externally, tissues show different sizes of magnetic torque, the vector of which is oriented identically with the vector of the magnetic field. To measure this magnetic torque, it must be diverted by magnetic impulse, the energy of which is absorbed by protons and a resonance can be detected. Thereby the longitudinal tissue resonance decreases and transverse tissue resonance increases. When the electrical impulse is discontinued, relaxation occurs (T1 longitudinal relaxation time, T2 transverse relaxation time). Imaging of tissues is based on the difference of these times in tissues and assigned intensity of grey (black/white scale). It does not use a noxious ionizing radiation for imaging.
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