Comparison of myocardial T1 mapping during breath-holding and free-breathing.

We found that myocardial T1 values during free-breathing were about 3-8% lower in all cross sections than those during breath-holding. In free-breathing, it may be difficult to assess myocardial T1 values, except in the basal region, because of underestimation; thus, the findings should be interpreted with caution, especially in children.