title: In vivo cardiovascular magnetic resonance of 2D vessel wall diffusion anisotropy in carotid arteries.
abstract: BACKGROUND
  Diffusion weighted (DW) cardiovascular magnetic resonance (CMR) has shown great potential to discriminate between healthy and diseased vessel tissue by evaluating the apparent diffusion coefficient (ADC) along the arterial axis. Recently, ex vivo studies on porcine arteries utilizing diffusion tensor imaging (DTI) revealed a circumferential fiber orientation rather than an organization in axial direction, suggesting dominant diffusion perpendicular to the slice direction. In the present study, we propose a method to access tangential and radial diffusion of carotids in vivo by utilizing a pulse sequence that enables high resolution DW imaging in combination with a two-dimensional (2D) diffusion gradient direction sampling scheme perpendicular to the longitudinal axis of the artery.
  
  
  METHODS
  High resolution DTI of 12 healthy male volunteers (age: 25-60 years) was performed on one selected axial slice using a read-out segmented EPI (rs-EPI) sequence on a 3T MR scanner.
  
  
  RESULTS
  It was found consistently for all 12 volunteers, that the tangential component as the principle direction of diffusion. Mean vessel wall fractional anisotropy (FA) values ranged from 0.7 for the youngest to 0.56 for the oldest participant. Linear regression analysis between the FA values and volunteers age revealed a highly significant (P < 0.01) linear relationship with an adjusted R2of 0.52. In addition, a linear trend (P < 0.1) could be observed between radial diffusivity (RD) and age.
  
  
  CONCLUSIONS
  These results point to FA being a sensitive parameter able to capture changes in the vascular architecture with age. In detail, the data demonstrate a decrease in FA with advancing age indicating possible alterations of tissue microstructural integrity. Moreover, analyzing 2D diffusion tensor directions is sufficient and applicable in a clinical setup concerning the overall scan time.
authors.affiliation: Clinical Institute for Medical and Chemical Laboratory Diagnosis, Medical University of Graz, Auenbruggerplatz 15, A-8036, Graz, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Opriessnig
authors.affiliation: Clinical Institute for Medical and Chemical Laboratory Diagnosis, Medical University of Graz, Auenbruggerplatz 15, A-8036, Graz, Austria.
authors.forename: Harald
authors.initials: H
authors.lastname: Mangge
authors.affiliation: Institute of Medical Engineering, Graz University of Technology, Stremayrgasse 16/III, A-8010, Graz, Austria.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Stollberger
authors.affiliation: Department of Radiology, Division of Neuroradiology, Vascular and Interventional Radiology, Medical University of Graz, Auenbruggerplatz 9, A-8036, Graz, Austria.
authors.forename: Hannes
authors.initials: H
authors.lastname: Deutschmann
authors.affiliation: Department of Radiology, Division of Neuroradiology, Vascular and Interventional Radiology, Medical University of Graz, Auenbruggerplatz 9, A-8036, Graz, Austria. gernot.reishofer@medunigraz.at.
authors.forename: Gernot
authors.identifier: http://orcid.org/0000-0002-3068-6475
authors.initials: G
authors.lastname: Reishofer
mesh_terms: D000328:Adult; D000367:Age Factors; D000818:Animals; D016880:Anisotropy; D002339:Carotid Arteries / Q000000981:diagnostic imaging*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D064368:Healthy Volunteers; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D016014:Linear Models; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D034421:Sus scrofa
keywords: Atherosclerosis; Cardiovascular diseases; Cardiovascular magnetic resonance; Diffusion tensor imaging