Response to letter regarding article, "Comprehensive validation of cardiovascular magnetic resonance techniques for the assessment of myocardial extracellular volume".

We acknowledge that with 6 subjects, the power of our study to assess the significance of between-subject correlation is limited and cannot rule out an underlying significant relationship.1 However, the small observed value of correlation (−0.21), outwith its significance, certainly provides no evidence of a meaningful relationship between postcontrast myocardial T1 and histological collagen volume fraction. Requiring a large number of patients for a correlation to become significant is not the hallmark of a good biomarker. Indeed, we are somewhat surprised by the line of argument taken by Iles and Taylor in their letter. There is great interest and impetus in this field and a major aim within the T1 mapping community is to develop a technology that may be able to help with not only …