title: Evaluation of symptomatic carotid plaques by tissue characterization using integrated backscatter ultrasound and magnetic resonance imaging.
abstract: BACKGROUND
  Unstable carotid plaques that consist of large lipid pool and intraplaque hemorrhage are more likely to cause cerebral infarction. We previously developed an integrated backscatter (IBS) ultrasound color-coded mapping method to evaluate the tissue characteristics of plaques. The purpose of this study was to determine whether 3-dimensional IBS color-coded mapping and signal intensity ratio (SIR) from magnetic resonance imaging (MRI) could distinguish the early symptomatic plaques from late symptomatic plaques.
  
  
  METHODS
  We performed quantitative tissue characterization of carotid plaques measuring IBS values and the SIR from T(1)-weighted MRI images in 95 carotid plaques (>50% stenosis) in 95 patients (45 symptomatic, 50 asymptomatic).
  
  
  RESULTS
  The percent unstable component volume (UCV) that consisted of lipid pool and intraplaque hemorrhage and the SIR of symptomatic carotid plaques were higher than those of asymptomatic plaques (57.8 ± 25.1 vs. 46.8 ± 25.1%, p = 0.036; 1.31 ± 0.25 vs. 1.21 ± 0.26, p = 0.047). In patients that were imaged within 3 days of symptom onset, the %UCV and SIR were significantly higher than the values in patients that were imaged 30-180 days after symptom onset (73.1 ± 18.4 vs. 38.7 ± 18.4%, p < 0.001; 1.38 ± 0.22 vs. 1.22 ± 0.26, p = 0.031). From the analysis of receiver operating characteristic curves, a %UCV of 50% (measured by IBS) and an SIR of 1.25 (measured by MRI) were the most optimal cutoff values for identifying early symptomatic plaques.
  
  
  CONCLUSIONS
  Noninvasive quantitative tissue characterization of atherosclerotic lesions in carotid arteries using IBS ultrasound and MRI is useful to distinguish early symptomatic plaques from late symptomatic plaques.
authors.affiliation: Department of Neurosurgery, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu, Japan.
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Yamada
authors.forename: Masanori
authors.initials: M
authors.lastname: Kawasaki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Yoshimura
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Enomoto
authors.forename: Takahiko
authors.initials: T
authors.lastname: Asano
authors.forename: Shinya
authors.initials: S
authors.lastname: Minatoguchi
authors.forename: Toru
authors.initials: T
authors.lastname: Iwama
mesh_terms: D000368:Aged; D058070:Asymptomatic Diseases; D016893:Carotid Stenosis / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000628:therapy; D002544:Cerebral Infarction / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology / Q000628:therapy; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D002546:Ischemic Attack, Transient / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology / Q000628:therapy; D007564:Japan; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012720:Severity of Illness Index; D013997:Time Factors; D014463:Ultrasonography