title: CT and MR imaging findings and their implications in the follow-up of patients with intracranial aneurysms treated with endosaccular occlusion with onyx.
abstract: OBJECTIVE
  Our purpose was to describe the CT and MR features of intracranial aneurysms occluded with the liquid polymer Onyx.
  
  
  METHODS
  At two centers, 35 aneurysms in 33 patients and 11 in nine patients were treated with the polymer. In 17 patients, adjunctive stents were placed at the aneurysm neck. All but three aneurysms originated from the internal carotid artery (ICA). Eighteen were giant; 15, large; and 13, small. Patients underwent pre- and postprocedural CT and/or MR imaging; MR angiograms (MRAs) were available in 22. In 35 patients (38 aneurysms), 3-month and/or 1-year follow-up angiograms were obtained for correlation with sectional images.
  
  
  RESULTS
  Except in two small aneurysms, polymer filling created beam hardening artifacts on CT scans. In 10 aneurysms, the polymer did not fill the aneurysm sac entirely; five showed recanalization at follow-up. On MR images (all sequences), the polymer appeared hypointense, probably because of its tantalum content; it did not create artifacts. MRAs falsely suggested reduced or absent ICA flow in 11 of 22 patients, nine of whom with stents. In the rest, MRA provided results comparable to those of selective angiography. In 12 patients, postprocedural imaging revealed new lesions.
  
  
  CONCLUSIONS
  Onyx appears hypointense on MR images, with no artifact, and it does not interfere with MRA except in patients with stents. MR imaging may reveal new parenchymal lesions, even in asymptomatic patients. In the immediate control and follow-up of polymer-treated aneurysms, MR imaging and MRA may be preferred. CT may show the degree of filling in the aneurysmal sac, but Onyx creates artifacts that hinder CT evaluation.
authors.affiliation: Department of Radiology, Hacettepe University Hospital, Ankara, Turkey.
authors.forename: Isil
authors.initials: I
authors.lastname: Saatci
authors.forename: H Saruhan
authors.initials: HS
authors.lastname: Cekirge
authors.forename: Elisa F M
authors.initials: EF
authors.lastname: Ciceri
authors.forename: Michel E
authors.initials: ME
authors.lastname: Mawad
authors.forename: A Gulsun
authors.initials: AG
authors.lastname: Pamuk
authors.forename: Aytekin
authors.initials: A
authors.lastname: Besim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D002340:Carotid Artery Diseases / Q000628:therapy; D002343:Carotid Artery, Internal / Q000473:pathology; D002426:Cavernous Sinus / Q000473:pathology; D002531:Cerebellum / Q000098:blood supply; D002533:Cerebral Angiography; D002648:Child; D004121:Dimethyl Sulfoxide / Q000008:administration & dosage*; D004621:Embolization, Therapeutic / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002532:Intracranial Aneurysm / Q000175:diagnosis / Q000628:therapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011145:Polyvinyls / Q000008:administration & dosage*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D015607:Stents; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: C450660:Onyx copolymer; D011145:Polyvinyls; D004121:Dimethyl Sulfoxide