title: Calculation of cerebral perfusion parameters using regional arterial input functions identified by factor analysis.
abstract: OBJECTIVE
  To calculate regional cerebral blood volume (rCBV), regional cerebral blood flow (rCBF), and regional mean transit time (rMTT) accurately, an arterial input function (AIF) is required. In this study we identified a number of AIFs using factor analysis of dynamic studies (FADS), and performed the cerebral perfusion calculation pixel by pixel using the AIF that was located geometrically closest to a certain voxel.
  
  
  METHODS
  To verify the robustness of the method, simulated images were generated in which dispersion or delay was added in some arteries and in the corresponding cerebral gray matter (GM), white matter (WM), and ischemic tissue. Thereafter, AIFs were determined using the FADS method and simulations were performed using different signal-to-noise ratios (SNRs). Simulations were also carried out using an AIF from a single pixel that was manually selected. In vivo results were obtained from normal volunteers and patients.
  
  
  RESULTS
  The FADS method reduced the underestimation of rCBF due to dispersion or delay that often occurs when only one AIF represents the entire brain.
  
  
  CONCLUSIONS
  This study indicates that the use of FADS and the nearest-AIF method is preferable to manual selection of one single AIF.
authors.affiliation: Department of Medical Radiation Physics, Lund University Hospital, Lund, Sweden. Linda.Knutsson@med.lu.se
authors.forename: Linda
authors.initials: L
authors.lastname: Knutsson
authors.forename: Elna-Marie
authors.initials: EM
authors.lastname: Larsson
authors.forename: Oliver
authors.initials: O
authors.lastname: Thilmann
authors.forename: Freddy
authors.initials: F
authors.lastname: Ståhlberg
authors.forename: Ronnie
authors.initials: R
authors.lastname: Wirestam
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001810:Blood Volume; D002536:Cerebral Arteries; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003198:Computer Simulation; D003287:Contrast Media; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009942:Organometallic Compounds; D012039:Regional Blood Flow; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C090600:gadobutrol