title: An intravoxel oriented flow model for diffusion-weighted imaging of the kidney.
abstract: By combining intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) we introduce a new diffusion model called intravoxel oriented flow (IVOF) that accounts for anisotropy of diffusion and the flow-related signal. An IVOF model using a simplified apparent flow fraction tensor (IVOFf ) is applied to diffusion-weighted imaging of human kidneys. The kidneys of 13 healthy volunteers were examined on a 3 T scanner. Diffusion-weighted images were acquired with six b values between 0 and 800 s/mm(2) and 30 diffusion directions. Diffusivity and flow fraction were calculated for different diffusion models. The Akaike information criterion was used to compare the model fit of the proposed IVOFf model to IVIM and DTI. In the majority of voxels the proposed IVOFf model with a simplified apparent flow fraction tensor performs better than IVIM and DTI. Mean diffusivity is significantly higher in DTI compared with models that account for the flow-related signal. The fractional anisotropy of diffusion is significantly reduced when flow fraction is considered to be anisotropic. Anisotropy of the apparent flow fraction tensor is significantly higher in the renal medulla than in the cortex region. The IVOFf model describes diffusion-weighted data in the human kidney more accurately than IVIM or DTI. The apparent flow fraction in the kidney proved to be anisotropic.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany. e_hilbert_f@ukw.de.
authors.forename: Fabian
authors.initials: F
authors.lastname: Hilbert
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Bock
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Neubauer
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Veldhoen
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wech
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany.
authors.forename: Thorsten Alexander
authors.initials: TA
authors.lastname: Bley
authors.affiliation: Department of Diagnostic and Interventional Radiology, University of Würzburg, Würzburg, Germany.
authors.forename: Herbert
authors.initials: H
authors.lastname: Köstler
mesh_terms: D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007668:Kidney / Q000033:anatomy & histology*; D064847:Multimodal Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Akaike information criterion; biophysical mechanisms of MR diffusion; diffusion tensor imaging; flow fraction; intravoxel incoherent motion; renal