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At the time the article was created J. Ray Ballinger had no recorded disclosures.View J. Ray Ballinger's current disclosures
At the time the article was last revised Andrew Murphy had no recorded disclosures.View Andrew Murphy's current disclosures
Relaxation is the process in which spins release the energy received from a radiofrequency pulse. MRI signal is influenced, among other factors, by different types of relaxation:
- T1 relaxation (spin-lattice or longitudinal relaxation)
- T2 relaxation (spin-spin or transverse relaxation)
- T2* relaxation (reflecting both T2 relaxation and magnetic field inhomogeneities)
Relaxation causes MR signal to recover in the longitudinal direction according to the time constant T1 (Figure 1) or decay in the transverse plane according to the time constant T2 (Figure 2).
The differences in relaxation between different tissues form the basis of image contrast (signal to noise ratio) in MRI.