title: MR imaging of partially thrombosed cerebral aneurysms: characteristics and evolution.
abstract: OBJECTIVE
  A comprehensive evaluation of aneurysmal morphometry requires appreciation of both the vascular lumen and the intraluminal thrombus. MR imaging methods can both evaluate the lumen and directly image the vessel wall. We investigated the ability of T1-weighted, T2-weighted, and steady-state MR imaging techniques to delineate thrombus morphology and reveal changes with time.
  
  
  METHODS
  Nine patients with fusiform basilar or intracranial vertebral artery aneurysms that contained intraluminal thrombus were studied with MR imaging. All patients underwent at least 2 imaging sessions, which were separated by 4-22 months. Analysis of signal intensity to determine the mean signal intensity from thrombus, blood, CSF, and brain in matched regions was performed. Aneurysm maximal diameter and cross-sectional area were determined with and without thrombus.
  
  
  RESULTS
  Thrombus was identified on all image sequences, and its general appearance was consistent between imaging sessions. Thrombus produced the highest and most consistent signal intensities with T1-weighted and steady-state techniques, though the latter showed superior contrast between luminal blood and thrombus. Heterogeneity within clot was evident in 4/9 of patients, with peripheral hyperintensity being a common feature.
  
  
  CONCLUSIONS
  Steady-state imaging was found to be superior to T1- and T2-weighted imaging for delineating and characterizing intraluminal thrombus within aneurysms. The imaging characteristics of intraluminal thrombus proved to be very consistent for long periods. Assessment of overall aneurysm size, including thrombosed portions, permits more accurate evaluation of aneurysm growth and concomitantly may permit more informed clinical decision-making with regard to the timing and need for aneurysm treatment.
authors.affiliation: Department of Radiology, University of California, San Francisco, 94143, USA. Alastair.Martin@radiology.ucsf.edu
authors.forename: A J
authors.initials: AJ
authors.lastname: Martin
authors.forename: S W
authors.initials: SW
authors.lastname: Hetts
authors.forename: W P
authors.initials: WP
authors.lastname: Dillon
authors.forename: R T
authors.initials: RT
authors.lastname: Higashida
authors.forename: V
authors.initials: V
authors.lastname: Halbach
authors.forename: C F
authors.initials: CF
authors.lastname: Dowd
authors.forename: M T
authors.initials: MT
authors.lastname: Lawton
authors.forename: D
authors.initials: D
authors.lastname: Saloner
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003287:Contrast Media; D018450:Disease Progression; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000473:pathology* / Q000503:physiopathology; D020767:Intracranial Thrombosis / Q000473:pathology* / Q000503:physiopathology; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D014715:Vertebrobasilar Insufficiency / Q000473:pathology* / Q000503:physiopathology
chemical_list: D003287:Contrast Media