Inter-subject variation in partition coefficient is largely due to variation in LGE blood T1

Background MRI is the only non-invasive modality capable of quantifying diffuse cardiac fibrosis using late gadolinium enhanced (LGE) cardiac T1 mapping. This pulse sequence measures LGE cardiac T1, which directly correlates with the amount of extracellular contrast agent occupying the expanded extracellular matrix containing the interstitial fibrosis, and obviates the need for a reference normal tissue. A practical limitation of the LGE cardiac T1 mapping pulse sequence is that it is sensitive to contrast agent dosage and specific delayed imaging time (i.e., two factors that affect the amount of contrast agent present in tissue). Recently, a method was proposed to address this limitation by combining blood and myocardial T1 measurements preand post-contrast agent administration to calculate an index called partition coefficient (l). However, post-contrast blood T1 can vary across subjects, due to variations in hydration and renal function. We sought to evaluate intersubject variation in blood T1, myocardial T1, and l.