Time-resolved MR fingerprinting for T₂* signal extraction: MR fingerprinting meets echo planar time-resolved imaging

This study leverages the echo planar time-resolved imaging (EPTI) concept in MR fingerprinting (MRF) framework for a new time-resolved MRF (TRMRF) approach, and explores its capability for fast simultaneous quantification of multiple MR parameters including T₁, T₂, T₂*, proton density, off resonance, and B₁ ⁺.

The proposed TRMRF method uses the concept of EPTI to track the signal change along the EPI echo train for T₂* weighting with a k-t Poisson-based sampling order designed for acquisition. A two-dimensional decomposition algorithm was designed for the image reconstruction, enabling fast and precise subspace modeling. The accuracy of proposed method was evaluated by a T₁/T₂ phantom. The feasibility was demonstrated through 5 healthy volunteer brain studies.

In the phantom studies, T₁, T₂, and T₂* maps of TRMRF correlated strongly with gold-standard methods. The concordance correlation coefficients are 0.9999, 0.9984 and 0.9978, and R²s are 0.9998, 0.9971, and 0.9983. In the in vivo studies, quantitative maps were acquired with 5 healthy volunteers. TRMRF was demonstrated to have comparable results with spiral MRF and gradient-echo EPTI. TRMRF scans using 16, 10, and 6 s per slice were also evaluated to demonstrate the capability of shorter scan times.

A new approach is proposed to exploit the advantage of EPTI in the MRF framework. We demonstrate in phantom and in vivo experiments that T₁, T₂, T₂*, proton density, off resonance, and B₁ ⁺ can be simultaneously quantified within 6 s/slice by TRMRF.