Susceptibility tensor imaging (STI) of the brain.
Susceptibility tensor imaging (STI) is a recently developed MRI technique that allows quantitative determination of orientation-independent magnetic susceptibility parameters from the dependence of gradient echo signal phase on the orientation of biological tissues with respect to the main magnetic field. By modeling the magnetic susceptibility of each voxel as a symmetric rank-2 tensor, individual magnetic susceptibility tensor elements as well as the mean magnetic susceptibility and magnetic susceptibility anisotropy can be determined for brain tissues that would still show orientation dependence after conventional scalar-based quantitative susceptibility mapping to remove such dependence. Similar to diffusion tensor imaging, STI allows mapping of brain white matter fiber orientations and reconstruction of 3D white matter pathways using the principal eigenvectors of the susceptibility tensor. In contrast to diffusion anisotropy, the main determinant factor of the susceptibility anisotropy in brain white matter is myelin. Another unique feature of the susceptibility anisotropy of white matter is its sensitivity to gadolinium-based contrast agents. Mechanistically, MRI-observed susceptibility anisotropy is mainly attributed to the highly ordered lipid molecules in the myelin sheath. STI provides a consistent interpretation of the dependence of phase and susceptibility on orientation at multiple scales. This article reviews the key experimental findings and physical theories that led to the development of STI, its practical implementations, and its applications for brain research. Copyright © 2016 John Wiley & Sons, Ltd.
Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.|Department of Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Wei
W
Li
Brain Imaging and Analysis Center, School of Medicine, Duke University, Durham, NC, USA.|Department of Radiology, School of Medicine, Duke University, Durham, NC, USA.
Chunlei
C
Liu
Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.|Department of Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
Timothy Q
TQ
Duong
F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.|Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Peter C M
PC
van Zijl
F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.|Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Xu
X
Li
D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D059906:Neuroimaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D066127:White Matter / Q000033:anatomy & histology / Q000000981:diagnostic imaging*
brain imaging; fiber tracking; gradient echo MRI; phase contrast; quantitative susceptibility mapping; susceptibility tensor imaging; white matter