MRI take home point (3)

• Longitudinal and transverse relaxation times are determined largely by the macromolecular environment of hydrogen nuclei. T1 > T2
• The more macromolecules of the correct size, the shorter T1.
• The more slowly water molecules move and the longer they spend in the vicinity of larger molecules, the shorter T2 > T2*
• Diseased tissues tend to have longer T1 and T2 values, and higher spin-densities, than normal tissues.