title: The IVIM signal in the healthy cerebral gray matter: A play of spherical and non-spherical components.
abstract: The intra-voxel incoherent motion (IVIM) model assumes that blood flowing in isotropically distributed capillary segments induces a phase dispersion of the MR signal, which increases the signal attenuation in diffusion-weighted images. However, in most tissue types the capillary network has an anisotropic micro-architecture. In this study, we investigated the possibility to indirectly infer the anisotropy of the capillary network in the healthy cerebral gray matter by evaluating the dependence of the IVIM signal from the direction of the diffusion-encoding. Perfusion-related indices and self-diffusion were modelled as symmetric rank 2 tensors. The geometry of the tensors was quantified pixel-wise by decomposing the tensor in sphere-like, plane-like, and line-like components. Additionally, trace and fractional anisotropy of the tensors were computed. While the self-diffusion tensor is dominated by a spherical geometry with a residual contribution of the non-spherical components, both, fraction of perfusion and pseudo-diffusion, present a substantial (in the order of 30%) contribution of planar and linear components to the tensor metrics. This study shows that the IVIM perfusion estimates in the cerebral gray matter present a detectable deviation from the spherical model. These non-spherical components may reflect the direction-dependent morphology of the microcirculation. Therefore, the tensor generalization of the IVIM model may provide a tool for the non-invasive monitoring of cerebral capillary micro-architecture during development, aging or in pathologies.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: Tim
authors.initials: T
authors.lastname: Finkenstaedt
authors.affiliation: Siemens Healthcare AG, Zurich, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Klarhoefer
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Eberhardt
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: Anton S
authors.initials: AS
authors.lastname: Becker
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: Gustav
authors.initials: G
authors.lastname: Andreisek
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Boss
authors.affiliation: Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland. Electronic address: cristina.rossi@usz.ch.
authors.forename: Cristina
authors.initials: C
authors.lastname: Rossi
mesh_terms: D000328:Adult; D016880:Anisotropy; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000098:blood supply*; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D017352:Echo-Planar Imaging; D005260:Female; D066128:Gray Matter / Q000033:anatomy & histology* / Q000098:blood supply*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008297:Male; D008833:Microcirculation; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
keywords: Anisotropy; Gray matter; IVIM; Tensor