ABSTRACT
Magnetic resonance imaging is a technique to obtain images based on nuclear magnetic resonance (NMR) signals generated by nuclei under a strong magnetic field. Hemoglobin magnetic properties depend upon bonding with oxygen. Superconducting magnets are advantageous in that they can generate a strong magnetic field approaching a maximum of 10 T and the generated magnetic field is highly stable over time. Because permanent magnets do not require cooling, they are easy to maintain and are used in low magnetic field devices. Immediately after the strength of the external magnetic field applied to the nuclear spin changes abruptly or when the nuclear spin moves between Zeeman levels due to NMR, the magnetization temporarily deviates from the state of thermal equilibrium. The local magnetic field strength is different for each nucleus and varies with time. This acts in a direction to disassemble the orientation of the magnetic moments of the nuclei.
