Transverse NMR relaxation in biological tissues

Neuroimage. 2018 Nov 15;182:149-168. doi: 10.1016/j.neuroimage.2018.06.002. Epub 2018 Jun 7.


Transverse NMR relaxation is a fundamental physical phenomenon underpinning a wide range of MRI-based techniques, essential for non-invasive studies in biology, physiology and neuroscience, as well as in diagnostic imaging. Biophysically, transverse relaxation originates from a number of distinct scales - molecular (nanometers), cellular (micrometers), and macroscopic (millimeter-level MRI resolution). Here we review the contributions to the observed relaxation from each of these scales, with the main focus on the cellular level of tissue organization, commensurate with the diffusion length of spin-carrying molecules. We discuss how the interplay between diffusion and spin dephasing in a spatially heterogeneous tissue environment leads to a non-monoexponential time-dependent transverse relaxation signal that contains important biophysical information about tissue microstructure.

Keywords: Diffusion; MRI; Microstructure; NMR; Relaxation.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Brain / anatomy & histology*
  • Brain / cytology
  • Brain / diagnostic imaging*
  • Humans
  • Magnetic Phenomena*
  • Magnetic Resonance Imaging / methods*
  • Models, Theoretical*
  • Neuroimaging / methods*