Most MRI focuses on qualitative interpretation of MR data by acquiring spatial maps of relative variations in signal strength which are "weighted" by certain parameters. Quantitative methods instead attempt to determine spatial maps of accurate tissue relaxometry parameter values or magnetic field, or to measure the size of certain spatial features.

Examples of quantitative MRI methods are:

• T1-mapping (notably used in cardiac magnetic resonance imaging)
• T2-mapping
• Quantitative susceptibility mapping (QSM)
• Quantitative fluid flow MRI (i.e. some cerebrospinal fluid flow MRI)
• Magnetic resonance elastography (MRE)

Quantitative MRI aims to increase the reproducibility of MR images and interpretations, but has historically required longer scan times.

Quantitative MRI (or qMRI) sometimes more specifically refers to multi-parametric quantitative MRI, the mapping of multiple tissue relaxometry parameters in a single imaging session. Efforts to make multi-parametric quantitative MRI faster have produced sequences that map multiple parameters simultaneously, either by building separate encoding methods for each parameter into the sequence, or by fitting MR signal evolution to a multi-parameter model.

Resources used:
Quantitative_MRI on Wikipedia

See also:
DKFZ