title: Appearance of the Nellix endovascular aneurysm sealing system on computed tomography: implications for postoperative imaging surveillance.
abstract: OBJECTIVE
  To describe the imaging characteristics of the Nellix Endovascular Aneurysm Sealing (EVAS) System on serial computed tomography (CT) surveillance.
  
  
  METHODS
  Sixty-eight patients undergoing EVAS were enrolled in a surveillance protocol that included CT scans prior to hospital discharge and at 3, 6, and 9 months postoperatively. Images were analyzed for the presence of gas within the endobag, endoleak, and for maximum radiodensity measured in Hounsfield units (HU) within the uppermost, middle, and lowermost regions of each endobag.
  
  
  RESULTS
  Gas was seen within the endobags of all 68 EVAS repairs at the first postoperative CT compared with 2 (5.6%) of 36 undergoing the 3-month scan. The endobags appeared radiodense during initial imaging, and the median (interquartile range) radiodensity of the Nellix polymer decreased from 158.3 HU (149.5; 169.5) at the postoperative CT to 81.0 HU (74.0; 88.0) at 3 months, excluding 3 cases in which contrast pre-fill was utilized. Type I endoleak was seen at the periphery of the aneurysm sac or in the cleft between the endobags, with a substantially different appearance to endoleak after endovascular aneurysm repair.
  
  
  CONCLUSIONS
  The evolution of CT appearances after EVAS was characteristic and predictable. The device endobags were initially radiodense, which may impact the detection of endoleak within 3 months of EVAS. Endoleaks after EVAS were seen in a different anatomical area to endoleaks after conventional stent-graft repair.
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK akarthik@sgul.ac.uk.
authors.forename: Alan
authors.initials: A
authors.lastname: Karthikesalingam
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK.
authors.forename: Jorg L
authors.initials: JL
authors.lastname: de Bruin
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK.
authors.forename: Shaneel R
authors.initials: SR
authors.lastname: Patel
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK.
authors.forename: Bilal
authors.initials: B
authors.lastname: Azhar
authors.affiliation: Department of Surgery and Translational Medicine, University of Milano Bicocca, Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Rossi
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Morgan
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK.
authors.forename: Peter J E
authors.initials: PJ
authors.lastname: Holt
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Loftus
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, St George's University Hospitals NHS Foundation Trust, London, UK.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Thompson
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging / Q000601:surgery*; D001027:Aortography / Q000379:methods*; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D057867:Endoleak / Q000000981:diagnostic imaging* / Q000209:etiology; D057510:Endovascular Procedures / Q000009:adverse effects / Q000295:instrumentation*; D006801:Humans; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D015607:Stents; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
keywords: abdominal aortic aneurysm; computed tomography; endoleak; endovascular aneurysm sealing; radiodensity; radiopacity; reintervention; surveillance