Pulse sequence
In Fourier transform NMR spectroscopy and imaging, a pulse sequence describes a series of radio frequency pulses applied to the sample, such that the free induction decay is related to the characteristic frequencies of the desired signals. After applying a Fourier transform, the signal can be represented in the frequency domain as the NMR spectrum.
The outcome of pulse sequences is often analyzed using the product operator formalism.
MRI sequences
In magnetic resonance imaging (MRI), a particular setting of pulse sequences and pulsed field gradients constitute an MRI sequence, and results in a particular appearance.[1] For example, the MRI sequence of fluid attenuated inversion recovery (FLAIR) results in fluid suppression by setting an inversion time that nulls fluids. The images have a high signal in lacunar infarction, multiple sclerosis (MS) plaques, subarachnoid haemorrhage and meningitis.[2]
In MRI, additional gradient pulses are applied by switching magnetic fields that exhibit a space-dependent gradient which can be used to reconstruct spatially resolved images after applying Fourier transforms.[3]
See also
References
- ^ Dr Jeremy Jones and Prof Frank Gaillard. "MRI sequences (overview)". Radiopaedia. Retrieved 2017-10-15.
- ^ "Fluid attenuation inversion recoveryg". radiopaedia.org. Retrieved 2015-12-03.
- ^ Bernstein, M.A.; King, K.E.; Zhou, X.J.; Fong, W. (2004). Handbook of MRI Pulse Sequences. Retrieved 2008-04-08.
External links
- Pulse sequences in the online textbook
- The Basics of NMR (by Joseph Hornak)