Howtosignalprocessing
- What is the effect of RF pulses used in MRI?
- Why is a 180 RF pulse applied in spin echo imaging in MRI after a 90 RF pulse?
- What is the consequence of repetitive RF pulses?
- What is the purpose of the 90 degree pulse in the spin echo pulse sequence?
What is the effect of RF pulses used in MRI?
RF pulse is applied for a few milliseconds disturbs or flips the protons at the same time and out of alignment from the main magnetic field. The amount of this rotation or flip depends on the strength and duration of the RF pulse. 90 RF pulse rotates the net magnetization vector to transverse plane .
Why is a 180 RF pulse applied in spin echo imaging in MRI after a 90 RF pulse?
A 180° RF pulse can rephase spins and reverse static field inhomogeneities. After a 90° RF pulse, spins dephase and transverse magnetization decreases. If we apply a 180° RF pulse, spins rephase and transverse magnetization reappears.
What is the consequence of repetitive RF pulses?
Rapidly repeated rf pulses, such as those used in turbo or fast spin echo techniques, can have the effect of reducing J-coupling, resulting in an increased T2 relaxation time and higher signal intensity from fat [6].
What is the purpose of the 90 degree pulse in the spin echo pulse sequence?
In summary, after a 90-degree pulse, the tissue magnetization is rotated so that all of it lies in the xy-plane. This transverse magnetization is what the MRI scanner detects.
