T1 reactivity as an imaging biomarker in myocardial tissue characterization discriminating normal, ischemic and infarcted myocardium.

To demonstrate the potential for differentiating normal and diseased myocardium without Gadolinium using rest and stress T1-mapping. Patients undergoing 1.5T magnetic resonance imaging (MRI) as part of clinical work-up due to suspicion of coronary artery disease (CAD) were included. Adenosine stress perfusion MRI and late gadolinium enhancement (LGE) imaging were performed to identify ischemic and infarcted myocardium. Patients were retrospectively categorized into an ischemic, infarct and control group based on conventional acquisitions. Patient with both ischemic and infarcted myocardium were excluded. A total of 64 patients were included: ten with myocardial ischemia, 15 with myocardial infarction, and 39 controls. A native Modified Look-Locker Inversion Recovery (MOLLI) T1-mapping acquisition was performed at rest and stress. Pixel-wise myocardial T1-maps were acquired in short-axis view with inline motion-correction. Short-axis T1-maps were manually contoured using conservative septal sampling. Regions of interest were sampled in ischemic and infarcted areas detected on perfusion and LGE images. T1 reactivity was calculated as the percentage difference in T1 values between rest and stress. Remote myocardium was defined as myocardium without defects in the ischemic and infarcted group whereas normal myocardium is found in the control group only. Native T1-values were significantly higher in infarcted myocardium in rest and stress [median 1044 ms (interquartile range (IQR) 985-1076) and 1053 ms (IQR 989-1088)] compared to ischemic myocardium [median 961 ms (IQR 939-988) and 958 ms (IQR 945-988)]. T1-reactivity was significantly lower in ischemic and infarcted myocardium [median 0.00% (IQR - 0.18 to 0.16) and 0.41% (IQR 0.09-0.86)] compared to remote myocardium [median 3.54% (IQR 1.48-5.78) and 3.21% (IQR 1.95-4.79)]. Rest-stress T1-mapping is able to distinguish between normal, ischemic, infarcted and remote myocardium using native T1-values and T1-reactivity, and holds potential as an imaging biomarker for tissue characterization in MRI.