title: Brachial artery vasomotion and transducer pressure effect on measurements by active contour segmentation on ultrasound.
abstract: OBJECTIVE
  To use feed-forward active contours (snakes) to track and measure brachial artery vasomotion on ultrasound images recorded in both transverse and longitudinal views; and to compare the algorithm's performance in each view.
  
  
  METHODS
  Longitudinal and transverse view ultrasound image sequences of 45 brachial arteries were segmented by feed-forward active contour (FFAC). The segmented regions were used to measure vasomotion artery diameter, cross-sectional area, and distention both as peak-to-peak diameter and as area. ECG waveforms were also simultaneously extracted frame-by-frame by thresholding a running finite-difference image between consecutive images. The arterial and ECG waveforms were compared as they traced each phase of the cardiac cycle.
  
  
  RESULTS
  FFAC successfully segmented arteries in longitudinal and transverse views in all 45 cases. The automated analysis took significantly less time than manual tracing, but produced superior, well-behaved arterial waveforms. Automated arterial measurements also had lower interobserver variability as measured by correlation, difference in mean values, and coefficient of variation. Although FFAC successfully segmented both the longitudinal and transverse images, transverse measurements were less variable. The cross-sectional area computed from the longitudinal images was 27% lower than the area measured from transverse images, possibly due to the compression of the artery along the image depth by transducer pressure.
  
  
  CONCLUSIONS
  FFAC is a robust and sensitive vasomotion segmentation algorithm in both transverse and longitudinal views. Transverse imaging may offer advantages over longitudinal imaging: transverse measurements are more consistent, possibly because the method is less sensitive to variations in transducer pressure during imaging.
authors: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Theodore W
authors: TW
authors: Cary
authors: Department of Medicine, Division of Cardiovascular Medicine, Section of Vascular Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Courtney B
authors: CB
authors: Reamer
authors: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Laith R
authors: LR
authors: Sultan
authors: Department of Medicine, Division of Cardiovascular Medicine, Section of Vascular Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Emile R
authors: ER
authors: Mohler
authors: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
authors: Chandra M
authors: CM
authors: Sehgal
mesh_terms: D001916:Brachial Artery / Q000000981:diagnostic imaging* / Q000502:physiology*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009068:Movement; D015588:Observer Variation; D011312:Pressure; D013997:Time Factors; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation*