Improved gradient echo magnitude‐ and phase‐based mapping of T2$$ {\mathrm{T}}_2 $$ using multiple RF spoiling increments at 3T and 7T

Abstract

AbstractPurposeThe transverse relaxation time T holds significant relevance in clinical applications and research studies. Conventional T mapping approaches rely on spin‐echo sequences, which require lengthy acquisition times and involve high radiofrequency (RF) power deposition. An alternative gradient echo (GRE) phase‐based T mapping method, utilizing steady‐state acquisitions at one small RF spoil phase increment, was recently demonstrated. Here, a modified magnitude‐ and phase‐based T mapping approach is proposed, which improves estimations by simultaneous fitting of and signal amplitude () at three or more RF spoiling phase increments, instead of assuming a fixed value.MethodsThe feasibility of the magnitude‐phase‐based method was assessed by simulations, in phantom and in vivo experiments using skipped‐CAIPI three‐dimensional‐echo‐planar imaging (3D‐EPI) for rapid GRE imaging. , and PD estimations obtained by our method were compared to of the phase‐based method and and PD of spoiled GRE‐based multi‐parameter mapping using a multi‐echo version of the same sequence.ResultsThe agreement of the proposed with ground truth and reference values was higher than that of phase‐based in simulations and in phantom data. While phase‐based overestimation increases with actual and , the proposed method is accurate over a large range of physiologically meaningful and values. At the same time, precision is improved. In vivo results were in line with these observations.ConclusionAccurate magnitude‐phase‐based T mapping is feasible in less than 5 min scan time for 1 mm nominal isotropic whole‐head coverage at 3T and 7T.