3D magnetic resonance fingerprinting with quadratic RF phase

Abstract

Purpose: To implement 3D magnetic resonance fingerprinting (MRF) with quadratic RF phase (qRF-MRF) for simultaneous quantification of T₁ , T₂ , ΔB₀ , and $T_2^{\ast }$ .

Methods: 3D MRF data with effective undersampling factor of 3 in the slice direction were acquired with quadratic RF phase patterns for T₁ , T₂ , and $T_2^{\ast }$ sensitivity. Quadratic RF phase encodes the off-resonance by modulating the on-resonance frequency linearly in time. Transition to 3D brings practical limitations for reconstruction and dictionary matching because of increased data and dictionary sizes. Randomized singular value decomposition (rSVD)-based compression in time and reduction in dictionary size with a quadratic interpolation method are combined to be able to process prohibitively large data sets in feasible reconstruction and matching times.

Results: Accuracy of 3D qRF-MRF maps in various resolutions and orientations are compared to 3D fast imaging with steady-state precession (FISP) for T₁ and T₂ contrast and to 2D qRF-MRF for $T_2^{\ast }$ contrast and ΔB₀ . The precision of 3D qRF-MRF was 1.5-2 times higher than routine clinical scans. 3D qRF-MRF ΔB₀ maps were further processed to highlight the susceptibility contrast.

Conclusion: Natively co-registered 3D whole brain T₁ , T₂ , $T_2^{\ast }$ , ΔB₀ , and QSM maps can be acquired in as short as 5 min with 3D qRF-MRF.

Keywords: intra-voxel frequency dispersion; iron; magnetic resonance fingerprinting; precision; quantitative susceptibility mapping.