title: Evaluation of EPI distortion correction methods for quantitative MRI of the brain at high magnetic field.
abstract: High field MRI has been applied to high-resolution structural and functional imaging of the brain. Echo planar imaging (EPI) is an ultrafast acquisition technique widely used in diffusion imaging, functional MRI and perfusion imaging. However, it suffers from geometric and intensity distortions caused by static magnetic field inhomogeneity, which is worse at higher field strengths. Such susceptibility artifacts are particularly severe in relation to the small size of the mouse brain. In this study we compared different distortion correction methods, including nonlinear registration, field map-based, and reversed phase-encoding-based approaches, on quantitative imaging of T1 and perfusion in the mouse brain acquired by spin-echo EPI with inversion recovery and pseudo-continuous arterial spin labeling, respectively, at 7 T. Our results showed that the 3D reversed phase-encoding correction outperformed other methods in terms of geometric fidelity, and that conventional field map-based correction could be improved by combination with affine transformation to reduce the bias in the field map. Both methods improved quantification with smaller fitting error and regional variation. These approaches offer robust correction of EPI distortions at high field strengths and hence could lead to more accurate co-registration and quantification of imaging biomarkers in both clinical and preclinical applications.
authors.affiliation: Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium Agency for Science Technology and Research, 11 Biopolis Way, #01-02 Helios Building, Singapore, 138667.
authors.forename: Xin
authors.initials: X
authors.lastname: Hong
authors.affiliation: Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium Agency for Science Technology and Research, 11 Biopolis Way, #01-02 Helios Building, Singapore, 138667.
authors.forename: Xuan Vinh
authors.initials: XV
authors.lastname: To
authors.affiliation: Clinical Imaging Research Centre, National University of Singapore, 14 Medical Drive, #B1-01, Singapore, 117599.
authors.forename: Irvin
authors.initials: I
authors.lastname: Teh
authors.affiliation: Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium Agency for Science Technology and Research, 11 Biopolis Way, #01-02 Helios Building, Singapore, 138667.
authors.forename: Jian Rui
authors.initials: JR
authors.lastname: Soh
authors.affiliation: Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium Agency for Science Technology and Research, 11 Biopolis Way, #01-02 Helios Building, Singapore, 138667; Clinical Imaging Research Centre, National University of Singapore, 14 Medical Drive, #B1-01, Singapore, 117599; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Block MD9, 2 Medical Drive #04-01, Singapore, 117597. Electronic address: kaichuang@gmail.com.
authors.forename: Kai-Hsiang
authors.initials: KH
authors.lastname: Chuang
mesh_terms: D000818:Animals; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D001931:Brain Mapping / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D060526:Magnetic Fields; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D015203:Reproducibility of Results
keywords: Cerebral blood flow; Distortion correction; Field inhomogeneity; High magnetic field; Susceptibility artifact; Transgenic mouse