title: Mean magnetic susceptibility regularized susceptibility tensor imaging (MMSR-STI) for estimating orientations of white matter fibers in human brain.
abstract: OBJECTIVE
  An increasing number of studies show that magnetic susceptibility in white matter fibers is anisotropic and may be described by a tensor. However, the limited head rotation possible for in vivo human studies leads to an ill-conditioned inverse problem in susceptibility tensor imaging (STI). Here we suggest the combined use of limiting the susceptibility anisotropy to white matter and imposing morphology constraints on the mean magnetic susceptibility (MMS) for regularizing the STI inverse problem.
  
  
  METHODS
  The proposed MMS regularized STI (MMSR-STI) method was tested using computer simulations and in vivo human data collected at 3T. The fiber orientation estimated from both the STI and MMSR-STI methods was compared to that from diffusion tensor imaging (DTI).
  
  
  RESULTS
  Computer simulations show that the MMSR-STI method provides a more accurate estimation of the susceptibility tensor than the conventional STI approach. Similarly, in vivo data show that use of the MMSR-STI method leads to a smaller difference between the fiber orientation estimated from STI and DTI for most selected white matter fibers.
  
  
  CONCLUSIONS
  The proposed regularization strategy for STI can improve estimation of the susceptibility tensor in white matter.
authors: F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA; Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Xu
authors: X
authors: Li
authors: Peter C M
authors: PC
authors: van Zijl
mesh_terms: D000328:Adult; D016880:Anisotropy; D001931:Brain Mapping / Q000379:methods*; D003198:Computer Simulation; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D019047:Phantoms, Imaging; D066127:White Matter / Q000033:anatomy & histology*
keywords: MMS; MSA; diffusion tensor imaging; fiber orientation; magnetic susceptibility anisotropy; mean magnetic susceptibility; susceptibility tensor imaging; white matter