Question

In MRI whats the function of static coil, gradiant coil , shim coil and radiofrequency coil?

what is t1 relaxation, t2 relaxation and t2* relaxation?

Answer 1

In MRI,

• The shim coils are used prior to the operation of the magnet to eliminate inhomogeneities in its field.
• The gradient coils are used to produce gradient fields. Those fields slightly distorts the main magnetic field in a predictable pattern, which causes the resonance frequency of protons to vary as a function of position. So, gradient coils are used to allow spatial encoding of the MR signal.
• Radiofrequency coils are used as both transmitters and receivers. When used as transmitters, these coils trasmit RF-pulses. And when used as receivers, they detect the MR signals.
• Static coil is used to produce the steady, static magnetic field.
• T1 relaxation is the process by which the net magnetization grows or returns to its initial maximum value parallel to .
• T2 relaxation is the process by which the transverse components of magnetization () dephase.

The transverse magnetization dephases much faster than that is predicted by natural atomic and molecular mechanisms; this rate is denoted as T2*. T2* is considered an "effective" value of T2, whereas T2 is considered the "natural" T2 of the tissue being imaged.