Accelerated Quantitative 3D T1ρ Dispersion Imaging of Bilateral Leg Muscles at 3T
Abstract
Purpose
T1ρ dispersion imaging is an emerging MRI technique for characterizing muscle tissue in aging, fibrosis, and metabolic conditions. However, the requirement for multiple independent repetitions at varying spin-lock frequencies (FSL) and spin-lock times (TSL) makes it clinically prohibitive due to prolonged scan times when high FSL-resolution is needed. This study demonstrates the feasibility of quantitative 3D T1ρ dispersion imaging of bilateral leg muscles at 3T within a clinically acceptable scan duration.
Methods
Imaging was performed on a 3T Philips Ingenia scanner using a modified 3D MAPSS sequence with unpaired phase cycling. To generate T1ρ dispersion curves, 20 FSLs (0–300 Hz, 15.75 Hz increments) were acquired at spin-lock times (TSL) of 20 and 30 ms, plus a shared TSL = 0 ms, totaling 41 independent 3D acquisitions (9:37 total scan time). Parameters included: FOV = 400x207x180mm3, voxel size=1.2x1.6x6mm3, TR/TE = 8.0/3.7 ms, and a Compressed SENSE factor of 4. For each acquisition, unique ky-kz undersampling patterns were applied (central size 14x8). A reference "Full Acquisition" protocol with paired phase cycling was also obtained for comparison (19:14 total scan time). Images were reconstructed via BART using l2-norm compressed sensing (λ=0.005) followed by non-linear curve fitting for dispersion map generation.
Results
The accelerated T1ρ dispersion protocol yielded values slightly lower than the full reference acquisition (average difference 4.7%). Crucially, the accelerated protocol maintained the expected increasing T1ρ trend at higher FSL, demonstrating high consistency with the reference standard despite the 50% reduction in scan time.
Conclusion
This work demonstrates that 3D T1ρ dispersion imaging of the lower extremities is feasible under regular clinical settings. The high consistency between the accelerated and reference protocols suggests that further undersampling may be possible, facilitating broader clinical research adoption.