title: Identification of the distal dural ring with use of fusion images with 3D-MR cisternography and MR angiography: application to paraclinoid aneurysms.
abstract: OBJECTIVE
  The distal dural ring (DDR) represents the anatomic border between the extradural and intradural internal carotid arteries (ICAs). The purpose of this study was to examine whether 3D-MR cisternography and MR angiography (MRA) fusion images can identify the boundary between the CSF and the cavernous sinus, which might represent the DDR.
  
  
  METHODS
  Thirty-six consecutive patients with 39 ICA aneurysms were examined with use of MR fusion images with 3D-cisternography and MRA on a 1.5T unit. Two neuroradiologists evaluated the configuration of the carotid cave and the location of the aneurysms on fusion images and classified them as intradural, transdural, and extradural aneurysms.
  
  
  RESULTS
  The borderline between the CSF and the cavernous sinus was visualized on fusion images in all patients. The carotid cave configuration in 72 ICAs was classified as having no dent (n = 31), a shallow dent (n = 27), and a deep dent (n = 14). The MR fusion images led to the classification of 39 ICA aneurysms as 21 intradural, 6 transdural, and 12 extradural. The interobserver agreement of MR fusion images was excellent (kappa = 0.80).
  
  
  CONCLUSIONS
  Fusion images with 3D-cisternography and MRA yielded clear visualization of the boundary between the suprasellar cistern and cavernous sinus indicating the DDR. This imaging technique may provide additional information in consideration of a treatment option for paraclinoid aneurysms.
authors.affiliation: Department of Radiology, National Cardiovascular Center, Osaka, Japan. yowatana@luke.or.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Watanabe
authors.forename: T
authors.initials: T
authors.lastname: Nakazawa
authors.forename: N
authors.initials: N
authors.lastname: Yamada
authors.forename: M
authors.initials: M
authors.lastname: Higashi
authors.forename: T
authors.initials: T
authors.lastname: Hishikawa
authors.forename: S
authors.initials: S
authors.lastname: Miyamoto
authors.forename: H
authors.initials: H
authors.lastname: Naito
mesh_terms: D000328:Adult; D000368:Aged; D002340:Carotid Artery Diseases / Q000473:pathology*; D002343:Carotid Artery, Internal / Q000473:pathology; D002426:Cavernous Sinus / Q000033:anatomy & histology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D002532:Intracranial Aneurysm / Q000473:pathology*; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D011446:Prospective Studies