title: Endovascular abdominal aortic aneurysm repair: nonenhanced volumetric CT for follow-up.
abstract: OBJECTIVE
  To evaluate the clinical usefulness of volumetric analysis at nonenhanced computed tomography (CT) as the sole method with which to follow up endovascular abdominal aortic aneurysm repair (EVAR) and to identify endoleaks causing more than 2% volumetric increase from the previous volume determination.
  
  
  METHODS
  The study had institutional review board approval. Images were reviewed retrospectively in a HIPAA-compliant manner for 230 CT studies in 70 patients (11 women, 59 men; mean age, 74 years) who underwent EVAR. The scannning protocol consisted of three steps: (a) contrast material-enhanced CT angiography before endovascular stent placement, (b) contrast-enhanced CT angiography 0-3 months after repair to depict immediate complications, and (c) nonenhanced CT at 3, 6, and 12 months after repair. At each follow-up visit, immediate aortic volume analysis was performed. If the interval volumetric change was 2% or less, no further imaging was performed. If the volume increased by more than 2% on the nonenhanced CT image, contrast-enhanced CT angiography was performed immediately to identify the suspected endoleak. Confidence intervals (CIs) were obtained by using bootstrapping to account for repeated measurements in the same patients.
  
  
  RESULTS
  Mean volume decrease was -3.2% (95% CI: -4.7%, -1.9%) in intervals without occurrence of a clinically relevant endoleak (n = 183). Types I and III high-pressure endoleaks (n = 10) showed a 10.0% (95% CI: 5.0%, 18.2%) interval volumetric increase. Type II low-pressure endoleaks (n = 37) showed a 5.4% (95% CI: 4.6%, 6.2%) interval volumetric increase. Endoleaks associated with minimal aortic volume increase of less than 2% did not require any intervention. This protocol reduced radiation exposure by approximately 57%-82% in an average-sized patient.
  
  
  CONCLUSIONS
  Serial volumetric analysis of aortic aneurysm with nonenhanced CT serves as an adequate screening test for endoleak, causing volumetric increase of more than 2% from the volume seen at the previous examination.
authors.affiliation: Departments of Radiology, Statistics, and Vascular Surgery, University of Wisconsin-Madison, Madison, WI 53792, USA.
authors.forename: Thorsten A
authors.initials: TA
authors.lastname: Bley
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Chase
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: François
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Shinki
authors.forename: Girma
authors.initials: G
authors.lastname: Tefera
authors.forename: Frank N
authors.initials: FN
authors.lastname: Ranallo
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Grist
authors.forename: Myron
authors.initials: M
authors.lastname: Pozniak
mesh_terms: D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000628:therapy*; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D003287:Contrast Media; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D012372:ROC Curve; D012189:Retrospective Studies; D015607:Stents; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media