title: Cross-sectional imaging identifies flow-mediated vasodilatation more accurately compared with longitudinal imaging.
abstract: OBJECTIVE
  The purpose of this study was to evaluate cross-sectional imaging to longitudinal plane imaging for measurement of flow-mediated dilatation (FMD).
  
  
  BACKGROUND
  Accurate and reproducible assessment of FMD as a measure of endothelial function has important implications. Conventional imaging of the brachial artery is in a longitudinal plane. However, the changes in vasodilatation seen are subtle and minimal (10%-20%) in healthy states with an even smaller change in diseased states, thus, affecting interobserver and intraobserver variability and reproducibility.
  
  
  METHODS
  Nine healthy volunteers (5 men, 4 women) between the ages of 25 and 65 years had baseline FMD measurements done using both longitudinal and cross-sectional imaging. Brachial artery was occluded by inflating the sphygmomanometer cuff on the arm at a pressure of 150 mm Hg for 5 minutes. The artery was imaged continuously for 5 minutes postdeflation. The images were recorded digitally on a computer and analyzed for area and diameter changes by user-guided semiautomated boundary detection method described by our group earlier.
  
  
  RESULTS
  The baseline measurements were normalized to 1.00 for both longitudinal and cross-sectional images. After cuff deflation, the mean longitudinal diameter increased to 1.10 +/- 0.04 versus 1.30 +/- 0.17 (P = .007) for the cross-sectional method. The mean longitudinal measurements were 85.7 +/- 13.9 pixels at baseline that increased to 94.3 +/- 13.1 pixels for a mean change of 8.6 +/- 3.1 pixels after cuff deflation, compared with a mean of 8577.4 +/- 2950.8 pixels that increased to 11120.5 +/- 3989.4 pixels for a mean change of 2543 +/- 1552 pixels by the cross-sectional method (P < .001).
  
  
  CONCLUSIONS
  Cross-sectional imaging produced a much larger change in area and pixels compared with longitudinal imaging. This translates into greater sensitivity in detecting small changes produced by FMD.
authors.affiliation: St Luke's-Roosevelt Hospital Center, New York, New York 10025, USA. fchaudhr@chpnet.org
authors.forename: Farooq A
authors.initials: FA
authors.lastname: Chaudhry
authors.forename: Sripal
authors.initials: S
authors.lastname: Bangalore
authors.forename: Shrikanth
authors.initials: S
authors.lastname: Upadya
authors.forename: Ajay
authors.initials: A
authors.lastname: Shah
authors.forename: Hossein
authors.initials: H
authors.lastname: Eftekhari
authors.forename: Danny
authors.initials: D
authors.lastname: Pudpud
authors.forename: Chandra M
authors.initials: CM
authors.lastname: Sehgal
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D019412:Anatomy, Cross-Sectional / Q000379:methods*; D001783:Blood Flow Velocity / Q000502:physiology*; D001916:Brachial Artery / Q000000981:diagnostic imaging* / Q000502:physiology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods*; D014664:Vasodilation / Q000502:physiology*