MR fingerprinting for rapid quantification of myocardial T1, T2, and proton spin density
To introduce a two-dimensional MR fingerprinting (MRF) technique for quantification of T1, T2, and M0 in myocardium.Methods:
An electrocardiograph-triggered MRF method is introduced for mapping myocardial T1, T2, and M0 during a single breath-hold in as short as four heartbeats. The pulse sequence uses variable flip angles, repetition times, inversion recovery times, and T2 preparation dephasing times. A dictionary of possible signal evolutions is simulated for each scan that incorporates the subject's unique variations in heart rate. Aspects of the sequence design were explored in simulations, and the accuracy and precision of cardiac MRF were assessed in a phantom study. In vivo imaging was performed at 3 Tesla in 11 volunteers to generate native parametric maps.Results:
T1 and T2 measurements from the proposed cardiac MRF sequence correlated well with standard spin echo measurements in the phantom study (R2 > 0.99). A Bland-Altman analysis revealed good agreement for myocardial T1 measurements between MRF and MOLLI (bias 1 ms, 95% limits of agreement −72 to 72 ms) and T2 measurements between MRF and T2-prepared balanced steady-state free precession (bias, −2.6 ms; 95% limits of agreement, −8.5 to 3.3 ms).Conclusion:
MRF can provide quantitative single slice T1, T2, and M0 maps in the heart within a single breath-hold.