Improved test-retest reliability of R^?₂ and susceptibility quantification using multishot multi-echo 3D EPI

This study aimed to evaluate the potential of 3D echo-planar imaging (EPI) for improving the reliability of T-2*-weighted (T-2*w) data and quantification of R-2* decay rate and susceptibility (chi) compared to conventional gradient echo (GRE)-based acquisition. Eight healthy subjects in a wide age range were recruited. Each subject received repeated scans for both GRE and EPI acquisitions with an isotropic 1 mm resolution at 3 T. Maps of R-2* and chi were quantified and compared using their inter-scan difference to evaluate the test-retest reliability. Inter-protocol differences of R-2* and chi between GRE and EPI were also measured voxel by voxel and in selected ROIs to test the consistency between the two acquisition methods. The quantifications of R-2* and chi using EPI protocols showed increased test-retest reliability with higher EPI factors up to 5 as performed in the experiment and were consistent with those based on GRE. This result suggested multi-shot multi-echo 3D EPI can be a useful alternative acquisition method for T-2*w MRI and quantification of R-2* and chi with reduced scan time, improved test-retest reliability and similar accuracy compared to commonly used 3D GRE.