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

Abstract

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.