title: Cerebral hemodynamic patterns with technetium Tc 99m exametazime single photon emission computed tomography and transcranial Doppler sonography: a validation study using visual stimulation.
abstract: OBJECTIVE
  To assess whether a correlation between perfusion changes to visual stimulus on the bilateral occipital areas and blood flow velocity changes to visual stimulus in both posterior cerebral arteries is present.
  
  
  METHODS
  Nine right-handed healthy subjects (4 women and 5 men; mean +/- SD age, 58.0 +/- 5.6 years) were included in the study. Visual stimulation was performed in room light with the subject's eyes open and looking around versus eyes closed as the stimulus-off condition. The blood flow velocities were recorded using transcranial Doppler sonography, and the regional cerebral blood flow measurements were recorded with the use of technetium Tc 99m exametazime and a single photon emission computed tomographic gamma camera system. Individual reactivity was defined as a relative increase of blood flow velocity and perfusion, which were calculated as percentage changes of baseline values.
  
  
  RESULTS
  Visual stimuli produced a marked increase of blood flow velocity in both posterior cerebral arteries (35.2 +/- 2.3 cm/s; P < .001) without a significant side-to-side difference in all subjects as well as a marked increase of perfusion on both occipital areas (24.9 +/- 4.8 cm/s; P < .01). Moreover, there was a positive correlation between blood flow velocity changes and perfusion changes on both sides (r = 0.833; P < .01).
  
  
  CONCLUSIONS
  The use of bilateral simultaneous Doppler recordings by means of a flow velocity averaging algorithm to a specific stimulus allows quantitative assessment of blood flow responses, and simple visual stimuli can be applied for different disorders to assess the vasomotor regulation that may result in measurable abnormal cerebral flow regulation even when clinically stabilized.
authors.affiliation: Department of Neurology, Osmangazi University, School of Medicine, Eskisehir, Turkey.
authors.forename: Nevzat
authors.initials: N
authors.lastname: Uzuner
authors.forename: Ilknur
authors.initials: I
authors.lastname: Ak
authors.forename: Demet
authors.initials: D
authors.lastname: Gücüyener
authors.forename: Talip
authors.initials: T
authors.lastname: Asil
authors.forename: Erkan
authors.initials: E
authors.lastname: Vardareli
authors.forename: Gazi
authors.initials: G
authors.lastname: Ozdemir
mesh_terms: D001783:Blood Flow Velocity; D001921:Brain / Q000098:blood supply*; D002560:Cerebrovascular Circulation; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D019275:Radiopharmaceuticals; D012039:Regional Blood Flow; D019690:Technetium Tc 99m Exametazime; D015899:Tomography, Emission-Computed, Single-Photon; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime