Abstract
PURPOSE: To propose and validate a cardiac T(1)ρ 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)ρ preparation pulses with different durations, while the last image uses a saturation pulse immediately before data acquisition. The T(1)ρ 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)ρ (T(1)ρ(Ad)) mapping in comparison with conventional continuous-wave T(1)ρ (T(1)ρ(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)ρ(CW) and T(1)ρ(Ad) mapping exhibited comparable precision. In vivo experiments on healthy volunteers showed that myocardial T(1)ρ(Ad) is higher than T(1)ρ(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)ρ(CW) and T(1)ρ(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)ρ(CW) and T(1)ρ(Ad) are promising for non-contrast detection of various cardiomyopathies at 0.55 T, but T(1)ρ(Ad) demonstrates better spatial uniformity than T(1)ρ(CW).