title: In vivo noninvasive detection and age definition of arterial thrombus by MRI.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the potential of magnetic resonance (MR) to detect arterial thrombotic obstruction and define thrombus age. BACKGROUND; Arterial thrombi underlie the clinical consequences of atherosclerosis and are not reliably detected by current noninvasive diagnostic techniques.
  
  
  METHODS
  Carotid thrombi were induced in swine (n = 7) by arterial injury. Serial high-resolution in vivo MR images were obtained using black-blood T1-weighted (T1W) and T2-weighted (T2W) sequences in a clinical 1.5T MR system at 6 h, 1 day and at 1, 2, 3, 6 and 9 weeks. At each time point one animal was sacrificed and the occluded carotid artery processed for histopathology. Thrombus signal intensity (SI) was normalized to that of the adjacent muscle. Thrombus age was assessed based on MR appearance by two blinded independent observers.
  
  
  RESULTS
  Thrombus appearance and relative SI revealed characteristic temporal changes in multicontrast-weighted MR images, reflecting histologic changes in the composition. Acute thrombus appeared very bright on the T2W images, facilitating the detection. Signal intensity was 197 +/- 25% at 6 h, peaking at 1 week (246 +/- 51%), reaching a plateau by 6 weeks (120 +/- 15%). At six weeks, complete thrombus organization was confirmed histologically. The T1W images had similar pattern with lower SI than T2W. Age definition using visual appearance was highly accurate (Pearson's chi-square with 4 df ranging from 96 to 132 and Cohen's kappa at 0.81 to 0.94). Agreement between observers was substantial (Pearson chi-square with 4 df = 91.5, kappa = 0.79).
  
  
  CONCLUSIONS
  Magnetic resonance imaging is a promising tool to noninvasively detect arterial thrombosis. Measurement of SI and the characteristic visual appearance of the thrombus have the potential to define thrombus age.
authors.affiliation: Cardiovascular Biology Research Laboratory, Mount Sinai Medical Center, New York, New York, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Corti
authors.forename: Julio I
authors.initials: JI
authors.lastname: Osende
authors.forename: Zahi A
authors.initials: ZA
authors.lastname: Fayad
authors.forename: John T
authors.initials: JT
authors.lastname: Fallon
authors.forename: Valentin
authors.initials: V
authors.lastname: Fuster
authors.forename: Gabor
authors.initials: G
authors.lastname: Mizsei
authors.forename: Elisha
authors.initials: E
authors.lastname: Dickstein
authors.forename: Burton
authors.initials: B
authors.lastname: Drayer
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Badimon
mesh_terms: D000367:Age Factors; D000818:Animals; D001157:Arterial Occlusive Diseases / Q000150:complications* / Q000175:diagnosis*; D017536:Carotid Artery, Common / Q000000981:diagnostic imaging* / Q000473:pathology*; D004195:Disease Models, Animal; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D008955:Models, Cardiovascular; D015588:Observer Variation; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine; D013927:Thrombosis / Q000150:complications* / Q000175:diagnosis*