MRI
Magnetic resonance imaging is a kind of fault imaging, which uses the phenomenon of magnetic resonance to obtain electromagnetic signals from human body and reconstruct human information. In 1946, flelex Bloch of Stanford University and Edward Purcell of Harvard University independently found the nuclear magnetic resonance phenomenon. The magnetic resonance imaging technology is based on this physical phenomenon. In 1972 Paul Lauterbur developed a method of space coding for MRI signals, which can reconstruct human images. MRI technology has some common points with other fault imaging technologies (such as CT), for example, they can show the distribution of some physical quantity (such as density) in space; at the same time, it also has its own characteristics. MRI can get fault image, 3D image in any direction, and even four-dimensional image of spatial spectral distribution.
Like pet and SPECT, the MRI signal used for imaging comes directly from the object itself. It can be said that MRI is also a kind of emission fault imaging. But unlike pet and SPECT, MR imaging can be imaged without radioisotope injection. This also makes MRI technology safer.
From the MRI images, we can get many physical properties of the material, such as proton density, spin lattice relaxation time T1, spin spin relaxation time T2, diffusion coefficient, magnetization coefficient, chemical displacement, etc. Compared with other imaging techniques (such as CT ultrasonic pet, etc.), MR imaging methods are more diverse, imaging principle is more complex and information is more abundant. Therefore, MRI has become a hot research direction in medical imaging.
Mr also has some shortcomings. The spatial resolution of the device is not as good as that of CT. MR can not be performed in patients with pacemaker or some metal foreign bodies. In addition, it is expensive, scanning time is relatively long, and more artifacts than CT.