title: Assessment of intracranial blood flow velocities using a computer controlled vasoactive stimulus: a comparison between phase contrast magnetic resonance angiography and transcranial Doppler ultrasonography.
abstract: OBJECTIVE
  To compare measurements of blood flow velocity (BFV) and BFV changes in the middle cerebral arteries (MCA) acquired from phase contrast magnetic resonance angiography (PCMRA) and transcranial Doppler ultrasound (TCD) during controlled manipulation of end-tidal partial pressure of carbon dioxide (PetCO2 ).
  
  
  METHODS
  In vivo TCD and PCMRA velocity data from the M1 segment in the MCA of nine healthy adult volunteers were acquired during precise targeting of PetCO2 induced by a computer-controlled gas delivery system. Doppler spectra and phase contrast data were processed into time-averaged peak-velocity (TAPV) values for comparison. Changes in velocity between baseline and hypercapnia were analyzed in terms of velocity-based cerebrovascular reactivity (CVR).
  
  
  RESULTS
  Good correlation between the pairs of velocity measurements acquired from the two modalities were found (ρ = 0.81), but Bland-Altman analysis indicates a significant bias error. There was relatively weak agreement between the pairs of computed CVR values (ρ = -0.26).
  
  
  CONCLUSIONS
  Under precise PetCO2 control, PCMRA proves to be more consistent than TCD. Despite issues with variability, TCD is qualitatively comparable to PCMRA measures of velocity in the MCA. However, PCMRA velocity results are better suited for analyses that require quantitative values, such as CVR.
authors.affiliation: Department of Physiology and Experimental Medicine, Hospital for Sick Children Toronto, Ontario, Canada.
authors.forename: Jackie
authors.initials: J
authors.lastname: Leung
authors.forename: Amir
authors.initials: A
authors.lastname: Behpour
authors.forename: Neil
authors.initials: N
authors.lastname: Sokol
authors.forename: Arun
authors.initials: A
authors.lastname: Mohanta
authors.forename: Andrea
authors.initials: A
authors.lastname: Kassner
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D002245:Carbon Dioxide / Q000008:administration & dosage*; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D020768:Middle Cerebral Artery / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*; D014662:Vasoconstrictor Agents / Q000008:administration & dosage; D055815:Young Adult
chemical_list: D014662:Vasoconstrictor Agents; D002245:Carbon Dioxide