Improved test–retest reliability of R₂^* and susceptibility quantification using multishot multi-echo 3D EPI

Purpose: This study aimed to evaluate the potential of 3D EPI for improving the reliability of (Formula presented.) -weighted data and quantification of (Formula presented.) decay rate and susceptibility (χ) compared with conventional gradient-echo (GRE)-based acquisition. Methods: 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 (Formula presented.) and χ were quantified, and their interscan differences were used to evaluate the test–retest reliability. Interprotocol differences of (Formula presented.) and χ between GRE and EPI were also measured voxel by voxel and in selected regions of interest to test the consistency between the two acquisition methods. Results: The quantifications of (Formula presented.) and χ 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. Conclusion: The result suggests that multishot multi-echo 3D EPI can be a useful alternative acquisition method for (Formula presented.) -weighted MRI and quantification of (Formula presented.) and χ with reduced scan time, improved test–retest reliability, and similar accuracy compared with commonly used 3D GRE.