Table 1.

T1 mapping measures available for assessment of myocardial fibrosis

Measure	Unit	Calculation	Advantages	Limitations
Native T1	ms	T1 relaxation curve	No gadolinium requirement (can use in severe renal failure)	T1 signal represented a composite of myocardium and extracellular space
Post-contrast T1	ms	T1 relaxation curve following gadolinium administration	Improved sensitivity in identifying myocardial fibrosis	Significant variability due to individual variation in gadolinium kinetics and time to imaging post-contrast injection
Partition coefficient (λ)	Ratio	Ratio of T1 signal change (pre- and post-contrast) in myocardium and blood pool	Excellent scan-rescan reproducibility	Does not account for plasma volume of distribution of gadolinium contrast
Extracellular volume fraction (ECV)	%	ECV = λ × (1—haematocrit)	Excellent scan-rescan reproducibility. Conceptually attractive measure	Gives a measure of relative fibrosis which may not best track changes in aortic stenosis
Fibrosis volume	ml	ECV × end-diastolic volume	Quantitative measure of absolute fibrosis volume	Limited evidence at current time May require indexing to body size to enable comparison between individuals