title: Carotid plaque morphometric assessment with three-dimensional ultrasound imaging.
abstract: OBJECTIVE
  As investigations into nonsurgical treatment for atherosclerosis expand, the measurement of plaque regression and progression has become an important end point to evaluate. Measurements of three-dimensional (3D) plaque volume are more reliable and sensitive to change than are traditional estimates of stenosis severity or cross-sectional area. 3D ultrasound (3D US) imaging may allow monitoring of plaque volume changes but has not been used routinely due to the cumbersome motorized units required to drive transducers. We investigated the variability, reliability, and the least amount of change detectable by 1D plaque measures, as well as 2D and 3D measures of plaque morphometry, that can be applied in a clinical environment.
  
  
  METHODS
  3D US imaging was obtained in 10 patients with carotid stenosis. The lumen and outer wall boundaries were outlined in serial cross-sectional images 1 mm apart. Three observers manually segmented vessel wall volumes (VWVs), and the segmentation was repeated again 4 weeks later. This allowed measurement of interobserver and intraobserver variability of 6 pairs of observations. We measured Bland-Altman statistics, intraclass correlation coefficients, coefficient of variability, and the minimum detectable plaque change for each morphometric measure.
  
  
  RESULTS
  The mean VWV of carotid lesions in the study was 1276.8 mm(3) (range, 620.6-1956.3 mm(3)). Bland-Altman plots demonstrated low interobserver and intraobserver variability. The interobserver variability of volume measurements as a function of mean volume was 14.8% and interobserver variability was 8.9%. Reliability was 87% as quantified by the interclass correlation and was 95% by the intraclass correlation. The least detectable change in VWV was 12.9% for interobserver variability and 4.5% for intraobserver variability for the three observers.
  
  
  CONCLUSIONS
  Carotid plaque diameter measurements from B-mode images have high variability. Plaque burden, as estimated by VWV, can be measured reliably with a 3D US technique using a clinical scanner. The volumetric change, with 95% confidence, that must be observed to establish that a plaque has undergone growth or regression is ∼12.9% for different observers and 4.5% for the same observer performing the follow-up study.
authors.affiliation: Center for Vascular Diagnostics, Division of Vascular Surgery, University of Maryland School of Medicine, Baltimore, Md; Department of Electrical and Computer Engineering, George Mason University, Fairfax, Va.
authors.forename: Khalid
authors.initials: K
authors.lastname: AlMuhanna
authors.affiliation: Department of Electrical and Computer Engineering, George Mason University, Fairfax, Va.
authors.forename: Md Murad
authors.initials: MM
authors.lastname: Hossain
authors.affiliation: Center for Vascular Diagnostics, Division of Vascular Surgery, University of Maryland School of Medicine, Baltimore, Md; Vascular Service, Veterans Affairs Medical Center, Baltimore, Md.
authors.forename: Limin
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Center for Vascular Diagnostics, Division of Vascular Surgery, University of Maryland School of Medicine, Baltimore, Md.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Fischell
authors.affiliation: Center for Vascular Diagnostics, Division of Vascular Surgery, University of Maryland School of Medicine, Baltimore, Md; Vascular Service, Veterans Affairs Medical Center, Baltimore, Md.
authors.forename: Gregory
authors.initials: G
authors.lastname: Kowalewski
authors.affiliation: Vascular Service, Veterans Affairs Medical Center, Baltimore, Md.
authors.forename: Moira
authors.initials: M
authors.lastname: Dux
authors.affiliation: Department of Electrical and Computer Engineering, George Mason University, Fairfax, Va.
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Sikdar
authors.affiliation: Center for Vascular Diagnostics, Division of Vascular Surgery, University of Maryland School of Medicine, Baltimore, Md; Vascular Service, Veterans Affairs Medical Center, Baltimore, Md. Electronic address: blal@smail.umaryland.edu.
authors.forename: Brajesh K
authors.initials: BK
authors.lastname: Lal
mesh_terms: D000368:Aged; D001783:Blood Flow Velocity; D002339:Carotid Arteries / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016893:Carotid Stenosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D058226:Plaque, Atherosclerotic; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D018616:Ultrasonography, Doppler, Duplex