title: Impact of a new metal artefact reduction algorithm in the noninvasive follow-up of intracranial clips, coils, and stents with flat-panel angiographic CTA: initial results.
abstract: BACKGROUND
  Flat-panel angiographic CT after intravenous contrast agent application (ivACT) is increasingly used as a follow-up examination after coiling, clipping, or stenting. The purpose of this study was to evaluate the feasibility of a new metal artefact reduction algorithm (MARA) in patients treated for intracranial aneurysms and stenosis.
  
  
  METHODS
  IvACT was performed on a flat-panel detector angiography system after intravenous application of 80 ml contrast media. The uncorrected raw images were transferred to a prototype reconstruction workstation where the MARA was applied. Two experienced neuroradiologists examined the corrected and uncorrected images on a commercially available workstation.
  
  
  RESULTS
  Artefacts around the implants were detected in all 16 uncorrected cases, while eight cases showed remaining artefacts after correction with the MARA. In the cases without correction, there were 11 cases with "extensive" artefacts and five cases with "many" artefacts. After correction, seven cases showed "few" and only one case "many" artefacts (Wilcoxon test, P < 0.001). Parent vessels were characterized as "not identifiable" in 62% of uncorrected images, while the delineation of parent vessels were classified as "excellent" in 50% of the cases after correction (Wilcoxon test, P = 0.001).
  
  
  CONCLUSIONS
  Use of the MARA in our study significantly reduced artefacts around metallic implants on ivACT images and allowed for the delineation of surrounding structures.
authors.affiliation: Department of Neuroradiology, University Medicine Goettingen, Goettingen, Germany. m.psychogios@med.uni-goettingen.de
authors.forename: Marios-Nikos
authors.initials: MN
authors.lastname: Psychogios
authors.forename: Bernhard
authors.initials: B
authors.lastname: Scholz
authors.forename: Christopher
authors.initials: C
authors.lastname: Rohkohl
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Kyriakou
authors.forename: Alexander
authors.initials: A
authors.lastname: Mohr
authors.forename: Peter
authors.initials: P
authors.lastname: Schramm
authors.forename: Dorothee
authors.initials: D
authors.lastname: Wachter
authors.forename: Katrin
authors.initials: K
authors.lastname: Wasser
authors.forename: Michael
authors.initials: M
authors.lastname: Knauth
mesh_terms: D000368:Aged; D000465:Algorithms; D016477:Artifacts; D001807:Blood Vessel Prosthesis; D002533:Cerebral Angiography / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D061185:Mechanical Thrombolysis / Q000295:instrumentation; D008670:Metals; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D015607:Stents; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods; D016896:Treatment Outcome
chemical_list: D008670:Metals