title: Contrast-reduced imaging of tissue concentration and arterial level (CRITICAL) for assessment of cerebral hemodynamics in acute stroke by magnetic resonance.
abstract: OBJECTIVE
  To compare cerebral perfusion data obtained by using a low-dose, T1-weighted MRI technique with radionuclide (single positron emission computed tomography [SPECT]) brain imaging and to assess the reproducibility of parametric MRI data (cerebral blood flow [CBF], cerebral blood volume [CBV], and time to peak [TTP]) by applying a previously described nuclear medicine technique to derive quantitative perfusion data.
  
  
  METHODS
  Single-slice brain and neck images were rapidly acquired during the passage of a small (1/10th of normal dose) bolus of contrast. Parametric images were constructed from the MR data by extracting the bolus transit curve for the brain and the peak arterial input curve from the carotid vessels in the neck. These were compared with SPECT perfusion imaging. Twenty-four patients with acute stroke were studied with both techniques; 13 underwent repeated scanning to assess data reproducibility.
  
  
  RESULTS
  Relative CBF data were comparable to SPECT data (r = 0.584, P = 0.01). Results were reproducible for relative CBF, CBV, and TTP. The arterial input function was significantly different on the second injection with an average difference of 73.5, suggesting that the signal-concentration relationship had lost linearity with increased contrast load. Absolute quantitative MRI data produced values in the expected range (CBF = 42.6 mL x 100 g(-1) x min(-1)).
  
  
  CONCLUSIONS
  This technique allows estimation of CBF in the setting of acute stroke with quantitative values in the expected range. Repeated measurements in the same patients showed that this technique provides a reproducible measure of relative CBF, CBV, and TTP.
authors.affiliation: Department of Academic Radiology, Nottingham University, UK. alan.moody@nottingham.ac.uk
authors.forename: A R
authors.initials: AR
authors.lastname: Moody
authors.forename: A
authors.initials: A
authors.lastname: Martel
authors.forename: A
authors.initials: A
authors.lastname: Kenton
authors.forename: S
authors.initials: S
authors.lastname: Allder
authors.forename: M A
authors.initials: MA
authors.lastname: Horsfield
authors.forename: G
authors.initials: G
authors.lastname: Delay
authors.forename: P
authors.initials: P
authors.lastname: Morgan
mesh_terms: D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000473:pathology; D002560:Cerebrovascular Circulation; D003287:Contrast Media; D019786:Gadolinium DTPA; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D020521:Stroke / Q000175:diagnosis / Q000503:physiopathology*; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA