title: Multidetector-row computed tomography angiography in abdominal aortic aneurysm treated with endovascular repair: evaluation of optimal timing of delayed phase imaging for the detection of low-flow endoleaks.
abstract: OBJECTIVE
  To evaluate the optimal timing of delayed phase imaging for detecting low-flow endoleaks.
  
  
  METHODS
  Fifty-eight patients with unruptured abdominal aortic aneurysm treated with endovascular repair underwent 1- and 6-month follow-up multidetector row computed tomography (CT) performed during unenhanced, arterial, and delayed phase. At 6-month follow-up, delayed phase imaging, focused on stent graft, was performed with a delay of 60 (early delayed enhanced phase) and 300 seconds (late delayed enhanced phase) after intravenous injection of 120 mL of iodinated nonionic contrast medium (iomeprol 300 mgI/mL, Iomeron), at a flow rate of 3 mL/s via an antecubital vein, with a detector-row configuration of 4 x 1-mm, a 1.25-mm slice width, and a pitch of 6. Six-month follow-up CT images were independently evaluated by 2 readers during 2 different reading sessions: sets A (unenhanced, arterial, and early delayed phase images) and B (unenhanced, arterial, and late delayed phase images). Sensitivity and diagnostic accuracy of both reading sessions were compared. The standard of reference was represented by the combined evaluation of 1- and 6-month CT scans.
  
  
  RESULTS
  At standard of reference, 24 of 58 patients had an endoleak classified as type 1 in 2 cases, type 2 in 21 cases, and type 3 in the last 1 case. Seven of 21 type 2 endoleaks were classified as low-flow endoleaks. Set A reading session, including early delayed enhanced phase, allowed the detection of 19 of 24 endoleaks (5 false-negative cases represented by low-flow endoleaks), whereas all endoleaks were detected during set B reading session, including late delayed enhanced phase. Differences between sets A and B in terms of sensitivity and diagnostic accuracy were statistically significant (P < 0.05).
  
  
  CONCLUSIONS
  For optimal multidetector CT detection of low-flow endoleaks in patients who underwent endovascular repair, delayed phase should be acquired 300 seconds after injection of contrast medium.
authors.affiliation: Department of Clinical Science and Bioimaging, Section of Radiology, University G. D'Annunzio, Chieti, Italy. r.iezzi@rad.unich.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Iezzi
authors.forename: Antonio Raffaele
authors.initials: AR
authors.lastname: Cotroneo
authors.forename: Antonella
authors.initials: A
authors.lastname: Filippone
authors.forename: Marco
authors.initials: M
authors.lastname: Santoro
authors.forename: Raffaella
authors.initials: R
authors.lastname: Basilico
authors.forename: Maria Luigia
authors.initials: ML
authors.lastname: Storto
mesh_terms: D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging*; D017544:Aortic Aneurysm, Abdominal / Q000175:diagnosis* / Q000601:surgery*; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007479:Iopamidol / Q000031:analogs & derivatives; D008297:Male; D015588:Observer Variation; D011183:Postoperative Complications / Q000175:diagnosis*; D011446:Prospective Studies; D011856:Radiographic Image Enhancement / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015607:Stents; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; C057937:iomeprol; D007479:Iopamidol