Native myocardial T1 precision is increased by correcting for myocardial blood variation

Background Native myocardial T1 mapping with CMR has emerged as a new diagnostic tool in heart disease. However, myocardial T1 will be affected by the T1 of blood present in the myocardium. To explore this, as there is no easy way to manipulate blood in isolation, we hypothesized that the population standard deviation (SD) for myocardial T1 could be reduced by correcting the myocardial T1 for characteristics of the blood. We sought to compare methods for doing this. Methods Consecutive patients (n=100, age 53+/-17 years, 74 % male) underwent clinical CMR at 1.5T (Siemens Aera). A modified Look-Locker inversion recovery (MOLLI) sequence was used to acquire T1 and T1* maps. Native myocardial T1 values from the midmural ventricular septum were measured in a mid-ventricular short-axis T1 map. Hematocrit was acquired by venous blood sampling. T1 and T1* values of blood were measured in the blood pool of the left and right ventricle (LV and RV).