title: Time-resolved CT angiography for the detection and classification of endoleaks.
abstract: OBJECTIVE
  To assess the feasibility and diagnostic performance of time-resolved computed tomographic (CT) angiography in the detection and classification of endoleaks after endovascular aortic aneurysm repair (EVAR) in high-risk patients.
  
  
  METHODS
  The study was approved by our ethics committee. Written informed consent was obtained from all participating patients. Fifty-four patients (42 male and 12 female patients; mean age, 70.9 years ± 9.3 [standard deviation]) with either thoracic (n = 8) or abdominal (n = 46) aortic aneurysms treated with a stent-graft were prospectively included. The patients were examined with a time-resolved CT angiographic protocol consisting of 12 low-dose phases (80 kVp; 120 mAs [effective]; scan range, 27 cm), with 60 mL of iomeprol. Patients with abdominal aneurysm repair also underwent contrast material-enhanced (CE) ultrasonography (US). The time delay between contrast enhancement within the stent lumen and the endoleak was measured. Effective radiation dose was calculated from the scanner protocols. Measures of diagnostic performance for the detection of endoleaks were calculated for time-resolved CT angiography, with CE US serving as the reference standard.
  
  
  RESULTS
  All time-resolved CT angiographic data sets were diagnostic. Mean effective radiation dose was 14.6 mSv. Four thoracic and 19 abdominal endoleaks were identified by using time-resolved CT angiography. Seventeen of 19 abdominal endoleaks were confirmed with CE US. This rate resulted in a sensitivity of 94%, a specificity of 93%, a positive predictive value of 89%, and a negative predictive value of 96% for time-resolved CT angiography after abdominal EVAR. Type I endoleaks showed significantly earlier mean peak contrast enhancement (0.28 second ± 0.83) compared with that for type II endoleaks (9.17 seconds ± 3.59, P < .0001).
  
  
  CONCLUSIONS
  Time-resolved CT angiography with 12 low-dose phases is feasible for patients after thoracic and abdominal EVAR. The protocol approximates the radiation dose of standard triphasic protocols. Its dynamic information differentiates types of endoleaks and shows high diagnostic performance.
authors.affiliation: Department of Clinical Radiology, University Hospitals-Grosshadern, Ludwig-Maximilians University, Marchioninistrasse 15, 81377 Munich, Germany. wieland.sommer@med.uni-muenchen.de
authors.forename: Wieland H
authors.initials: WH
authors.lastname: Sommer
authors.forename: Christoph R
authors.initials: CR
authors.lastname: Becker
authors.forename: Mareike
authors.initials: M
authors.lastname: Haack
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Rubin
authors.forename: Rolf
authors.initials: R
authors.lastname: Weidenhagen
authors.forename: Florian
authors.initials: F
authors.lastname: Schwarz
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Thorsten R
authors.initials: TR
authors.lastname: Johnson
authors.forename: Dirk A
authors.initials: DA
authors.lastname: Clevert
mesh_terms: D000368:Aged; D000792:Angiography / Q000379:methods*; D001014:Aortic Aneurysm / Q000000981:diagnostic imaging* / Q000628:therapy*; D003287:Contrast Media; D057867:Endoleak / Q000145:classification / Q000000981:diagnostic imaging*; D057510:Endovascular Procedures; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007479:Iopamidol / Q000031:analogs & derivatives; D008297:Male; D010743:Phospholipids; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013459:Sulfur Hexafluoride; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D010743:Phospholipids; C420843:contrast agent BR1; C057937:iomeprol; D007479:Iopamidol; D013459:Sulfur Hexafluoride