title: Bone subtraction CT angiography for the detection of intracranial aneurysms.
abstract: BACKGROUND
  The aim of the study was to retrospectively analyse the accuracy of CT angiography (CTA) of the Circle of Willis and a prototype bone subtraction CT angiogram (BSCTA) compared with digital subtraction angiography (DSA) in the detection of intracranial aneurysms.
  
  
  METHODS
  A total of 36 patients with suspected subarachnoid haemorrhage who had CTA scans that had matching DSA studies between November 2005 and December 2006 were retrospectively reviewed by two experienced neurointerventionalist. Three-dimensional volume-rendered (3D VR) CTA and BSCTA were reviewed, followed by review of the source data in multi-planar reformats (MPRs). The results were then assessed for sensitivity and specificity compared with the gold standard DSA. Time taken to review the studies, visibility of the ophthalmic, posterior communicating arteries, superior cerebella artery, posterior cerebral artery on the 3D VR BSCTA and CTA were analysed. BSCTA was assessed for residual bone and artificial stenosis. Further, the aneurysms were analysed for suitability of endovascular treatment versus surgical treatment based on CTA and BSCTA with MPR and 3D VR.
  
  
  RESULTS
  CTA 3D VR sensitivity and specificity was 94 and 80%, respectively. CTA MPR sensitivity and specificity was 100% and 90%, respectively. When both CTA 3D VR and MPR images were combined the sensitivity and specificity was 100 and 90%, respectively. BSCTA 3D VR sensitivity and specificity was 91 and 90%, respectively, and the MPR sensitivity and specificity was 97 and 90%, respectively. When both BSCTA 3D VR and MPR images were combined the sensitivity was 97% with a specificity of 90% Overall, an 84% correlation was found between both CTA and BSCTA when compared with DSA for assessing for suitability of endovascular treatment versus surgical treatment. A statistically significant difference was shown between the time taken to review the CTA and BSCTA (P < 0.001 confidence interval 3.1-3.9 min).
  
  
  CONCLUSIONS
  In this study there was no significant difference between the diagnostic ability of BSCTA compared with CTA. Importantly, both CTA and BSCTA had high sensitivities and specificities compared to DSA.
authors.affiliation: Department of Radiology, Royal Melbourne Hospital, Parkville, Victoria, Australia. sanjeeva.ramasundara@mh.org.au
authors.forename: S
authors.initials: S
authors.lastname: Ramasundara
authors.forename: P J
authors.initials: PJ
authors.lastname: Mitchell
authors.forename: R J
authors.initials: RJ
authors.lastname: Dowling
mesh_terms: D015901:Angiography, Digital Subtraction / Q000379:methods*; D002533:Cerebral Angiography / Q000379:methods*; D002941:Circle of Willis / Q000000981:diagnostic imaging; D003287:Contrast Media; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D002532:Intracranial Aneurysm / Q000150:complications / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging / Q000209:etiology; D036542:Tomography, Spiral Computed / Q000379:methods*
chemical_list: D003287:Contrast Media