Inversion recovery timing (TI nulling: STIR/FLAIR)
A graph of longitudinal magnetisation Mz against time after a 180 degree inversion pulse. Both fat and CSF start at minus M0 and recover along Mz = M0(1 minus 2 exp(minus TI over T1)) toward plus M0. Fat has a short T1 so it crosses zero early, at a short inversion time (about 150 to 180 ms) used by STIR to null fat. CSF has a long T1 so it crosses zero late, at a long inversion time (about 2000 to 2500 ms) used by FLAIR to null CSF. Imaging at a tissue's null point, where Mz equals zero, suppresses its signal.
More in MRI Physics
- Chemical shift misregistration artefact
- Diffusion-weighted imaging & ADC maps
- Fat suppression: STIR vs spectral vs opposed-phase
- General MRI artefacts (motion, aliasing, susceptibility, Gibbs)
- k-space filling & trajectories (FSE, EPI)
- Magnet types & field homogeneity (permanent/resistive/superconducting)
Practice the Physics paper
FRCRX is a Part 1 Physics question bank: true/false items with explanations, timed mocks and topic analytics.