title: Effect of regional tracer delay on CBF in healthy subjects measured with dynamic susceptibility contrast-enhanced MRI: comparison with 15O-PET.
abstract: OBJECTIVE
  Deconvolution based on truncated singular value decomposition (SVD deconvolution) is a promising method for measuring cerebral blood flow (CBF) with dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI), but it has proved extremely sensitive to tracer delay. The purpose of this study was to investigate the effect of regional tracer delay on CBF determined by SVD deconvolution (SVD-CBF). SVD-CBFs with and without correction for the delay were compared with CBF measured by positron emission tomography (PET-CBF), which is regarded as the gold standard for quantification of CBF.
  
  
  METHODS
  Perfusion MRI and PET were performed on seven healthy men. In the PET study, the CBF image was obtained with bolus injection of H2(15)O and continuous arterial sampling. In the DSC-MRI study with bolus injection of Gd-based contrast agent, dynamic perfusion data were obtained with a 1.5T scanner at 1-s intervals by means of gradient-echo echo-planar imaging. CBF was determined by the SVD deconvolution method with and without correction for the tracer delay. Region-of-interest measurements were obtained in the gray matter (cerebral cortex in the middle cerebral artery territory) and white matter (centrum semiovale).
  
  
  RESULTS
  Tracer delay was significantly longer in white matter than in gray matter (1.45+/-0.61 s vs. 0.59+/-0.35 s, P<0.01). Correction for the delay increased SVD-CBF in the white matter and consequently reduced the gray-to-white SVD-CBF ratio. The uncorrected gray-to-white SVD-CBF ratio was significantly larger than that of PET-CBF (3.33+/-0.66 vs. 2.54+/-0.49, P<0.01). However, the gray-to-white delay-corrected SVD-CBF ratio did not differ significantly from that of PET-CBF (2.83+/-0.31 vs. 2.54+/-0.49, P=0.10).
  
  
  CONCLUSIONS
  The tracer delay in DSC-MRI causes errors in CBF estimates, even in healthy persons, and therefore should be corrected for when delay-sensitive deconvolution, such as SVD deconvolution, is used.
authors.affiliation: Department of Radiology and Nuclear Medicine, Akita Research Institute of Brain and Blood Vessels, 6-10 Senshu-Kubota Machi, Akita 010-0874, Japan. iba@akita-noken.go.jp
authors.forename: Masanobu
authors.initials: M
authors.lastname: Ibaraki
authors.forename: Eku
authors.initials: E
authors.lastname: Shimosegawa
authors.forename: Hideto
authors.initials: H
authors.lastname: Toyoshima
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ishigame
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ito
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Takahashi
authors.forename: Shuichi
authors.initials: S
authors.lastname: Miura
authors.forename: Iwao
authors.initials: I
authors.lastname: Kanno
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003287:Contrast Media; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008657:Metabolic Clearance Rate; D010104:Oxygen Radioisotopes / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D003287:Contrast Media; D010104:Oxygen Radioisotopes; D019275:Radiopharmaceuticals