Purpose: Quantitative T1ρ and T2 MR mapping are promising MRI techniques for biochemical evaluation for soft-tissue, particularly articular cartilages, brain white matter, and tumors. Both techniques suffer from long scan duration. We present a novel approach in which T1ρ and T2 MRI are acquired and reconstructed simultaneously with quadrupled spatial resolution and nearly halved scan time compared to traditional approaches.
Methods: All experiments were performed using a 3T MR scanner (Ingenia, Philips) equipped with a 1Tx/16Rx knee coil. A 3D Magnetization-Prepared Angle-Modulated Partitioned k-Space Spoiled Gradient Echo Snapshots (3D MAPSS) sequence was implemented for high resolution 3D T1ρ and T2 mapping. To improve sensitivity, reduce artifacts, and reduce total scan duration, T1ρ preparation with adiabatic RF pulses, synovial fluid suppression, unpaired RF phase cycling, optimized spin-lock time or TE sampling schemes, and combined T1ρ and T2 imaging and map generation were implemented in a novel sequence termed “FastMAPSS”. The single combined sequence had high spatial resolution of 0.3×0.5×2 mm3 with 5:55min scan duration, while the standard T1ρ and T2 sequences had 0.44×0.77×4 mm3 acquired within 5 min each.
Results: SNR efficiency was greatly improved, and artifacts were maximally suppressed in the FastMAPSS sequence when integrating T1ρ and T2 mapping in one sequence and employing synergistically complementary curve fitting in the same equation for both maps using the complex MRI data. The combined T1ρ and T2 acquisition also avoided the need to co-register T1ρ and T2 images. As a result, high-resolution MRI (0.3×0.5×2 mm3) with laminar specificity on a 3T clinical scanner was achieved by simultaneous T1ρ and T2 mapping of the whole-knee cartilage in less than 6 minutes.
Conclusion: The combined T1ρ and T2 FastMAPSS MRI sequence allowed quadrupled spatial resolution with nearly halved scan time compared to the traditional approaches.
MRI, Quantitative Imaging, Relaxation Times