Please understand-medical imaging equipment and help me answer the following questions. . . . Thank you.

1) magnetic vibration imaging is an imaging technology that uses the signal generated by the nucleus in the magnetic field to reconstruct the image. It is also the principle of biological magnetic spin. A new generation of imaging technology, through the computer to collect magnetic vibration signals and reconstruct images, can make some CT scanning images develop lesions that cannot be displayed.

2) First of all, the human body contains a large number of hydrogen protons, which is characterized by the spin magnetic moment generated by odd protons in the spin process, also known as the nuclear magnetic moment. Hydrogen nucleus is the simplest, with only one proton, the strongest magnetic moment and the most susceptible to external magnetic field.

Normal people contain a lot of hydrogen protons, and each hydrogen can be regarded as a small magnet, and its distribution and arrangement are chaotic. At this time, if the human body enters a strong magnetic field, the spins of these small magnets must be rearranged according to the direction of the magnetic field lines. At this time, there are two kinds of magnetic moments, most of which are arranged along the magnetic field lines, with low potential energy and stable state; The number of arranged reverse magnetic lines is small, and the potential energy is high. The difference between them is the residual spin, and the resulting magnetization vector is the net magnetization vector, also known as the balanced macroscopic magnetization vector m.

In MR coordinates, the direction along the main magnetic field is the Z axis or the longitudinal axis, and the plane perpendicular to the main magnetic field is the XY plane or the horizontal plane, m. At this time, it spins around the Z axis at larmor frequency. If m is added. Larmor frequency RF pulse is applied to make it vibrate. At this point, it will precess away from the Z-axis XY plane, thus forming a transverse magnetization vector, and its angle away from the Z-axis is called flip angle. When the external RF pulse stops, it is switched on by M. Under the action of lattice magnetic field (environmental magnetic field), the generated transverse magnetization vector will gradually return from XY plane to Z axis, and at the same time, energy will be released in the form of RF signal, and the phase consistency of proton spin will gradually disappear and return to its original state. These released and three-dimensional coded RF signals are received by external coils and reconstructed into MR images after computer processing. I hope you are satisfied with my answer. I am engaged in this work.