title: Brain capillary transit time heterogeneity in healthy volunteers measured by dynamic contrast-enhanced T1-weighted perfusion MRI.
abstract: Capillary transit time heterogeneity, measured as CTH, may set the upper limit for extraction of substances in brain tissue, e.g., oxygen. The purpose of this study was to investigate the feasibility of dynamic contrast-enhanced T1weighted MRI (DCE-MRI) at 3 Tesla (T), in estimating CTH based on a gamma-variate model of the capillary transit time distribution. In addition, we wanted to investigate if a subtle increase of the blood-brain barrier permeability can be incorporated into the model, still allowing estimation of CTH.
  
  
  
  Twenty-three healthy subjects were scanned at 3.0T MRI system applying DCE-MRI and using a gamma-variate model to estimate CTH as well as cerebral blood flow (CBF), cerebral blood volume (CBV), and permeability of the blood-brain barrier, measured as the influx constant Ki. For proof of principle we also investigated three patients with recent thromboembolic events and a patient with a high grade brain tumor.
  
  
  
  In the healthy subjects, we found a narrow symmetric delta-like capillary transit time distribution in basal ganglia gray matter with median CTH of 0.93 s and interquartile range of 1.33 s. The corresponding residue impulse response function was compatible with the adiabatic tissue homogeneity model. In two patients with complete occlusion of the internal carotid artery and in the patient with a brain tumor CTH was increased with values up to 6 s in the affected brain tissue, with an exponential like residue impulse response function.
  
  
  
  Our results open the possibility of characterizing brain perfusion by the capillary transit time distribution using DCE-MRI, theoretically a determinant of efficient blood to brain transport of important substances.
  
  
  
  2 J. MAGN. RESON. IMAGING 2017;45:1809-1820.
authors.affiliation: Functional Imaging Unit, Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Glostrup, Denmark.|Institute of Clinical Medicine, The Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: Henrik B W
authors.initials: HBW
authors.lastname: Larsson
authors.affiliation: Functional Imaging Unit, Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Glostrup, Denmark.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Vestergaard
authors.affiliation: Functional Imaging Unit, Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Glostrup, Denmark.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Lindberg
authors.affiliation: Institute of Clinical Medicine, The Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.|Department of Neurology, Rigshospitalet, Glostrup, Denmark.
authors.forename: Helle K
authors.initials: HK
authors.lastname: Iversen
authors.affiliation: Functional Imaging Unit, Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Glostrup, Denmark.
authors.forename: Stig P
authors.initials: SP
authors.lastname: Cramer
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000502:physiology*; D002196:Capillaries / Q000000981:diagnostic imaging / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D063177:Pulse Wave Analysis / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media
keywords: MRI; blood-brain barrier; capillary transit time heterogeneity; cerebral hemodynamics; perfusion weighted MRI