Table 1.

Clinically useful qMRI techniques for assessment of the biochemical composition of tissues

MRI Technique	Biostructural Property Evaluated	Strengths	Limitations
T1ρ mapping	PG/GAG content and distribution	Sensitive to early PG depletion; does not necessitate use of contrast agent	Optimal at 3T; not available at all institutions
dGEMRIC	PG/GAG content and distribution	Well validated as an indirect measurement of PG/GAG content (high sensitivity and specificity)	Requires use of Gd contrast agent (contraindicated in patients with renal impairments); long delay (≈1.5 hours) between Gd administration and postcontrast MRI
T2 mapping	Collagen orientation and water content	Well validated; does not necessitate use of contrast agent; compatible with most MRI systems and field strengths	Susceptible to magic angle effects; cannot evaluate deeper (calcified) cartilage layers or other short T2 species (tendon, bone, ligaments, etc)
T2* mapping	Collagen orientation and water content	Does not necessitate use of contrast agent; can be faster than T2 mapping; UTE sequences allow for evaluation of short T2 species (calcified cartilage layer, tendon, ligament, etc)	Susceptible to magnetic field inhomogeneities and magic angle effects

dGEMRIC, delayed gadolinium-enhanced magnetic resonance imaging of cartilage; GAG, glycosaminoglycan; Gd, gadolinium; MRI, magnetic resonance imaging; PG, proteoglycan; qMRI, quantitative magnetic resonance imaging; UTE, ultrashort echo time.