title: Comparative study of power-based versus mean frequency-based transcranial color-coded duplex sonography in normal adults.
abstract: OBJECTIVE
  Power-based transcranial color-coded duplex sonography (p-TCCD) is a new ultrasonic method that has advantages compared with frequency-based TCCD (f-TCCD), since it is essentially independent of the angle of insonation, not subject to aliasing, and has a better signal-to-noise ratio. The purpose of this study was to evaluate the ability of p-TCCD to visualize flow in cerebral parenchyma and to compare the advantages, limitations, and reliability of velocity measurements of p-TCCD versus f-TCCD in the major basal cerebral arteries of normal subjects.
  
  
  METHODS
  Two investigators performed 15 p-TCCD and 15 f-TCCD studies in 30 normal subjects with adequate ultrasonic windows. Each investigator did a p-TCCD or f-TCCD study in every patient, and each was blinded in every case to the results of the other. Peak systolic (Vs) and end-diastolic (Vd) velocities were determined in the anterior, middle, and posterior cerebral, basilar, and vertebral arteries. The reliability of p-TCCD velocimetry was evaluated by calculating both the correlation coefficient (r) of the difference between p-TCCD versus f-TCCD measurements and the coefficient of variation (CV), defined as the difference between the mean values for p-TCCD and f-TCCD divided by the mean values for f-TCCD measurements, expressed as percent.
  
  
  RESULTS
  p-TCCD did not display flow in cerebral parenchyma but depicted arteries with a course perpendicular to that of the ultrasound beam and showed good reliability of velocity measurements in all examined arteries: for Vs, r was .84 to .93 (P < .001) and CV was 7.7% to 10.8%; for Vd, r was .87 to .90 (P < .001) and CV was 10.3% to 13.7%. The lack of directional and velocity information and tissue motion artifacts were unimportant limitations in p-TCCD.
  
  
  CONCLUSIONS
  Compared with f-TCCD, p-TCCD had no important advantages but had several unimportant limitations in a study of normal adults with adequate ultrasonic windows.
authors.affiliation: Department of Neurology, University of Bern, Inselspital, Switzerland.
authors.forename: R W
authors.initials: RW
authors.lastname: Baumgartner
authors.forename: C
authors.initials: C
authors.lastname: Schmid
authors.forename: I
authors.initials: I
authors.lastname: Baumgartner
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D001488:Basilar Artery / Q000000981:diagnostic imaging; D001783:Blood Flow Velocity; D002536:Cerebral Arteries / Q000000981:diagnostic imaging; D002560:Cerebrovascular Circulation; D003971:Diastole; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D016037:Single-Blind Method; D013599:Systole; D018615:Ultrasonography, Doppler, Color / Q000379:methods; D018616:Ultrasonography, Doppler, Duplex / Q000379:methods; D018617:Ultrasonography, Doppler, Pulsed; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods; D014711:Vertebral Artery / Q000000981:diagnostic imaging