Initial experience of cardiac T1? mapping at 0.55 T: Continuous wave versus adiabatic spin-lock preparation pulses

Abstract

Purpose: To propose and validate a cardiac T-1 rho mapping sequence at 0.55 T comparing continuous-wave and adiabatic spin-lock (SL) preparation pulses. Methods: The proposed 2D sequence acquires four single-shot balanced SSFP readout images with differing contrasts in a single breath-hold. The first three images are prepared with T-1 rho preparation pulses with different durations, while the last image uses a saturation pulse immediately before data acquisition. The T-1 rho map is calculated using a 3-parameter fitting method. Bloch equation simulations were performed to optimize the parameters of the adiabatic-SL pulses. Phantom studies and in vivo experiments in 10 healthy volunteers, a porcine myocardial infarction model, and a patient with suspected hypertrophic cardiomyopathy were performed to validate the performance of the proposed adiabatic T-1 rho (T-1 rho(Ad)) mapping in comparison with conventional continuous-wave T-1 rho (T-1 rho(CW)) mapping. Results: The adiabatic-SL pulse with simulation-optimized parameters demonstrated robust performance despite B-0 and B-1 field inhomogeneities. Phantom T-1 rho(CW) and T-1 rho(Ad) mapping exhibited comparable precision. In vivo experiments on healthy volunteers showed that myocardial T-1 rho(Ad) is higher than T-1 rho(CW) (106.1 +/- 7.1 vs. 47.0 +/- 5.1 ms, p < 0.01) with better precision (11.4% +/- 2.6% vs. 14.5% +/- 2.1%, p < 0.01) and less spatial variation (10.9% +/- 3.0% vs. 14.4% +/- 3.4%, p < 0.01). Both T-1 rho(CW) and T-1 rho(Ad) mapping agreed with late gadolinium enhancement findings in the porcine model and the patient, and exhibited improved contrast compared to T-1 and T-2 mapping. Conclusion: Both T-1 rho(CW) and T-1 rho(Ad) are promising for non-contrast detection of various cardiomyopathies at 0.55 T, but T-1 rho(Ad) demonstrates better spatial uniformity than T-1 rho(CW).