title: Subtraction 3D CT angiography with the orbital synchronized helical scan technique for the evaluation of postoperative cerebral aneurysms treated with cobalt-alloy clips.
abstract: OBJECTIVE
  CT angiography (CTA) has been used for the evaluation of intracranial aneurysms and recently has been applied to assess postoperative aneurysms treated with titanium-alloy clips. We investigated the clinical usefulness of subtraction CTA by using the orbital synchronized helical scan technique (OSHST) for evaluating intracranial aneurysms surgically treated with cobalt-alloy clips.
  
  
  METHODS
  We scanned an agar gel phantom with a cobalt-alloy clip mounted in the center by using subtraction CT with and without OSHST. Eighteen patients (20 aneurysms) who underwent surgery with cobalt-alloy clips were postoperatively evaluated with subtraction CTA with OSHST, and the results were compared with those from digital subtraction angiography. Two neuroradiologists independently evaluated the 3D CTA images and source images with and without subtraction for the presence of residual flow in the aneurysm and stenotic change in parent or neighboring arteries.
  
  
  RESULTS
  For the phantom study, significantly fewer artifacts from clips were noted on images obtained by using subtraction CT with OSHST than on those obtained without OSHST. For the clinical study, subtraction CTA with OSHST also showed fewer clip artifacts than did conventional CTA. Image quality was poor, and we were unable to diagnose residual neck for 5% (1/20) with subtraction CTA with OSHST and 75% (15/20) with conventional CTA. For evaluation of adjacent vessels, image quality was poor for none (0/20) with subtraction CTA with OSHST and for 55% (11/20) with conventional CTA. For subtraction CTA with OSHST, sensitivity in detecting residual neck was 1.0, and specificity was 0.94. For conventional CTA, sensitivity and specificity were both 0.25.
  
  
  CONCLUSIONS
  OSHST is a useful technique for subtracting cobalt-alloy clips, and subtraction CTA with OSHST is available for evaluating aneurysms after clipping with cobalt-alloy clips.
authors: Department of Radiology, National Cardiovascular Center, Osaka, Japan. ywatanab@hsp.ncvc.go.jp
authors: Y
authors: Y
authors: Watanabe
authors: N
authors: N
authors: Kashiwagi
authors: N
authors: N
authors: Yamada
authors: M
authors: M
authors: Higashi
authors: T
authors: T
authors: Fukuda
authors: S
authors: S
authors: Morikawa
authors: Y
authors: Y
authors: Onishi
authors: K
authors: K
authors: Iihara
authors: S
authors: S
authors: Miyamoto
authors: H
authors: H
authors: Naito
mesh_terms: D000497:Alloys; D015901:Angiography, Digital Subtraction / Q000379:methods*; D002533:Cerebral Angiography / Q000379:methods*; D003035:Cobalt; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000209:etiology*; D008297:Male; D019635:Neurosurgical Procedures / Q000009:adverse effects*; D013525:Surgical Instruments / Q000009:adverse effects*; D036542:Tomography, Spiral Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D000497:Alloys; D003035:Cobalt