Free-Breathing 3 T Magnetic Resonance T2-Mapping of the Heart

OBJECTIVES This study sought to establish an accurate and reproducible T-2-mapping cardiac magnetic resonance (CMR) methodology at 3 T and to evaluate it in healthy volunteers and patients with myocardial infarct. BACKGROUND Myocardial edema affects the T-2 relaxation time on CMR. Therefore, T-2-mapping has been established to characterize edema at 1.5 T. A 3 T implementation designed for longitudinal studies and aimed at guiding and monitoring therapy remains to be implemented, thoroughly characterized, and evaluated in vivo. METHODS A free-breathing navigator-gated radial CMR pulse sequence with an adiabatic T-2 preparation module and an empirical fitting equation for T-2 quantification was optimized using numerical simulations and was validated at 3 T in a phantom study. Its reproducibility for myocardial T-2 quantification was then ascertained in healthy volunteers and improved using an external reference phantom with known T-2. In a small cohort of patients with established myocardial infarction, the local T-2 value and extent of the edematous region were determined and compared with conventional T-2-weighted CMR and x-ray coronary angiography, where available. RESULTS The numerical simulations and phantom study demonstrated that the empirical fitting equation is significantly more accurate for T-2 quantification than that for the more conventional exponential decay. The volunteer study consistently demonstrated a reproducibility error as low as 2 +/- 1% using the external reference phantom and an average myocardial T-2 of 38.5 +/- 4.5 ms. Intraobserver and interobserver variability in the volunteers were -0.04 +/- 0.89 ms (p = 0.86) and -0.23 +/- 0.91 ms (p = 0.87), respectively. In the infarction patients, the T-2 in edema was 62.4 +/- 9.2 ms and was consistent with the x-ray angiographic findings. Simultaneously, the extent of the edematous region by T-2-mapping correlated well with that from the T-2-weighted images (r = 0.91). CONCLUSIONS The new, well-characterized 3 T methodology enables robust and accurate cardiac T-2-mapping at 3 T with high spatial resolution, while the addition of a reference phantom improves reproducibility. This technique may be well suited for longitudinal studies in patients with suspected or established heart disease. (J Am Coll Cardiol Img 2012; 5: 1231-9) (C) 2012 by the American College of Cardiology Foundation