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

ObjectivesThis study sought to establish an accurate and reproducible T2-mapping cardiac magnetic resonance (CMR) methodology at 3 T and to evaluate it in healthy volunteers and patients with myocardial infarct.BackgroundMyocardial edema affects the T2 relaxation time on CMR. Therefore, T2-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.MethodsA free-breathing navigator-gated radial CMR pulse sequence with an adiabatic T2 preparation module and an empirical fitting equation for T2 quantification was optimized using numerical simulations and was validated at 3 T in a phantom study. Its reproducibility for myocardial T2 quantification was then ascertained in healthy volunteers and improved using an external reference phantom with known T2. In a small cohort of patients with established myocardial infarction, the local T2 value and extent of the edematous region were determined and compared with conventional T2-weighted CMR and x-ray coronary angiography, where available.ResultsThe numerical simulations and phantom study demonstrated that the empirical fitting equation is significantly more accurate for T2 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 T2 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 T2 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 T2-mapping correlated well with that from the T2-weighted images (r = 0.91).ConclusionsThe new, well-characterized 3 T methodology enables robust and accurate cardiac T2-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.