title: MR angiographic evaluation is limited in intracranial aneurysms embolized with Nexus coils.
abstract: BACKGROUND
  Nexus coils are a type of bioactive coil used to embolize intracranial aneurysms. The purpose of this study was to test the feasibility of the noninvasive follow-up of aneurysms treated with Nexus coils by means of magnetic resonance angiography (MRA).
  
  
  METHODS
  Three-dimensional (3D) time-of-flight (TOF) MRA images of patients treated with Nexus coils (the Nexus coil group) or bare platinum coils (the control group) were compared for the severity and frequency of artifacts. The reviewers were unaware of the coil types used. In the Nexus coil group, 17 MRA examinations were performed in 14 patients harboring 15 aneurysms treated with Nexus coils using 3-T (n = 11) and 1.5-T (n = 6) MR units. The findings of these examinations were compared to those of 28 MRA studies conducted on 24 control patients (bare platinum coils). Conventional angiograms, maximum intensity projections, and source data of 3D-TOF MRA were reviewed in terms of residual flow within aneurysms and parent arterial patencies. The qualities of the MRA images were rated from grade 0 (no significant signal loss) to grade 2 (complete segmental signal loss of the parent artery). The normalized ratio, defined as the diameter of signal loss on MRA axial source images (in mm) divided by that of coil mass on plain radiographs (in mm), was calculated to compare the sizes of coil-related artifacts in the two groups.
  
  
  RESULTS
  The quality of the MRA image for the Nexus coil group was significantly poorer than that for the control group (p < 0.0001) due to signal loss caused by the presence of artifacts in the former. In particular, the interpretation of aneurysmal status was impossible in all cases of coiled aneurysms due to segmental signal loss. The sizes of the MRA artifacts were also significantly larger in the Nexus coil group (normalized ratio 1.61 +/- 0.22 vs. 1.15 +/- 0.20; p < 0.0001).
  
  
  CONCLUSIONS
  Follow-up evaluations by 3D-TOF MRA of aneurysms treated with Nexus coils are severely limited.
authors.affiliation: Department of Neurosurgery, Konkuk University Hospital, Seoul, South Korea.
authors.forename: Hyun-Seung
authors.initials: HS
authors.lastname: Kang
authors.forename: Won-Jin
authors.initials: WJ
authors.lastname: Moon
authors.forename: Hong Gee
authors.initials: HG
authors.lastname: Roh
authors.forename: Moon Hee
authors.initials: MH
authors.lastname: Han
authors.forename: Woo Jin
authors.initials: WJ
authors.lastname: Choe
authors.forename: Joon
authors.initials: J
authors.lastname: Cho
authors.forename: Chang-Taek
authors.initials: CT
authors.lastname: Moon
authors.forename: Young Cho
authors.initials: YC
authors.lastname: Koh
mesh_terms: D000328:Adult; D000368:Aged; D004621:Embolization, Therapeutic / Q000295:instrumentation*; D004867:Equipment Design; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000175:diagnosis*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged