title: Reduction of CT beam hardening artefacts of ethylene vinyl alcohol copolymer by variation of the tantalum content: evaluation in a standardized aortic endoleak phantom.
abstract: OBJECTIVE
  Our aim was to develop an aortic stent graft phantom to simulate endoleak treatment and to find a tantalum content (TC) of ethylene-vinyl-alcohol-copolymer that causes fewer computed tomography (CT) beam hardening artefacts, but still allows for fluoroscopic visualization.
  
  
  METHODS
  Ethylene-vinyl-alcohol-copolymer specimens of different TC (10-50 %, and 100 %) were injected in an aortic phantom bearing a stent graft and endoleak cavities with simulated re-perfusion. Fluoroscopic visibility of the ethylene-vinyl-alcohol-copolymer specimens was analyzed. In addition, six radiologists analyzed endoleak visibility, and artefact intensity of ethylene-vinyl-alcohol-copolymer in CT.
  
  
  RESULTS
  Reduction of TC significantly decreased CT artefact intensity of ethylene-vinyl-alcohol-copolymer and increased visibility of endoleak re-perfusion (p < 0.000). It also significantly decreased fluoroscopic visibility of ethylene-vinyl-alcohol-copolymer (R = 0.883, p ≤ 0.01), and increased the active embolic volumes prior to visualization (Δ ≥ 40 μl). Ethylene-vinyl-alcohol-copolymer specimens with a TC of 45-50 % exhibited reasonable visibility, a low active embolic volume and a tolerable CT artefact intensity.
  
  
  CONCLUSIONS
  The developed aortic stent graft phantom allows for a reproducible simulation of embolization of endoleaks. The data suggest a reduction of the TC of ethylene-vinyl-alcohol-copolymer to 45 -50 % of the original, to interfere less with diagnostic imaging in follow-up CT examinations, while still allowing for fluoroscopic visualization.
authors.affiliation: Institute for Clinical Radiology, Hospitals of the Ludwig-Maximilians-University of Munich, Pettenkoferstr. 8a, D-80336, Munich, Germany, karlamaria.treitl@med.uni-muenchen.de.
authors.forename: Karla M
authors.initials: KM
authors.lastname: Treitl
authors.forename: Michael
authors.initials: M
authors.lastname: Scherr
authors.forename: Monika
authors.initials: M
authors.lastname: Förth
authors.forename: Franziska
authors.initials: F
authors.lastname: Braun
authors.forename: Daniel
authors.initials: D
authors.lastname: Maxien
authors.forename: Marcus
authors.initials: M
authors.lastname: Treitl
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging*; D016477:Artifacts; D004621:Embolization, Therapeutic / Q000379:methods; D057867:Endoleak / Q000000981:diagnostic imaging*; D005471:Fluoroscopy; D006801:Humans; D019047:Phantoms, Imaging; D011145:Polyvinyls / Q000737:chemistry*; D015607:Stents; D013635:Tantalum / Q000737:chemistry*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods
chemical_list: D011145:Polyvinyls; C020320:ethylene-vinyl alcohol copolymer; D013635:Tantalum