Endovascular Abdominal Aortic Aneurysm Repair: Nonenhanced Volumetric CT for Follow-up

Endovascular Abdominal Aortic Aneurysm Repair: Nonenhanced Volumetric CT for Follow-up¹

1. Thorsten A. Bley, MD²,
2. Peter J. Chase, MD,
3. Scott B. Reeder, MD, PhD,
4. Christopher J. François, MD,
5. Kazuhiko Shinki, MS,
6. Girma Tefera, MD,
7. Frank N. Ranallo, PhD,
8. Thomas M. Grist, MD and
9. Myron Pozniak, MD

+ Author Affiliations

1. ¹From the Departments of Radiology (T.A.B., P.C., S.B.R., C.J.F., F.R., T.M.G., M.P.), Statistics (K.S.), and Vascular Surgery (G.T.), University of Wisconsin–Madison, 600 Highland Ave, Madison, WI 53792. From the 2006 RSNA Annual Meeting.

1. Address correspondence to
   M.P. (e-mail: mpozniak@uwhealth.org).

• ↵² Current address: Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

1. Author contributions: Guarantors of integrity of entire study, T.A.B., M.P.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, T.A.B., P.C., S.B.R., F.R., M.P.; clinical studies, S.B.R., G.T., M.P.; statistical analysis, S.B.R., K.S., M.P.; and manuscript editing, T.A.B., S.B.R., C.J.F., G.T., F.R., M.P.

Abstract

Purpose: 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.

Materials and 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.

Conclusion: 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.

© RSNA, 2009

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