title: Prospective intraindividual comparison of unenhanced magnetic resonance imaging vs contrast-enhanced computed tomography for the planning of endovascular abdominal aortic aneurysm repair.
abstract: OBJECTIVE
  This study clarified whether unenhanced magnetic resonance imaging (MRI) is an alternative to contrast-enhanced computed tomography (CT) for aortoiliac arterial measurement before endovascular abdominal aortic aneurysm repair (EVAR).
  
  
  METHODS
  The institutional review board approved this prospective study. Twenty patients being considered for EVAR underwent MRI using a steady-state free-precession sequence in a 1.5-T system and contrast-enhanced CT within 4 weeks of each other. Two independent observers reviewed MRI and CT in random order using vessel analysis software and measured seven diameters, four lengths, and the angle of the aortoiliac arteries. The intermodality, interobserver, and intraobserver agreements were assessed for each measurement by intraclass correlation coefficients (ICCs) and the Altman-Bland method. Additionally, the observers independently recorded the number of bilateral renal arteries, decided EVAR suitability, and selected the main endograft on each modality.
  
  
  RESULTS
  Intermodality ICCs for observers A and B showed ranges of 0.83 to 0.99 and 0.70 to 0.98; interobserver ICCs for MRI and CT showed ranges of 0.73 to 0.99 and 0.65 to 0.99; and intraobserver ICCs for MRI and CT showed ranges of 0.59 to 0.99 and 0.59 to 0.99. In intermodality, interobserver, and intraobserver comparisons, mean differences in diameters were included within the range -1 to +1 mm, excluding three of seven diameters on CT in interobserver comparison and one of seven on CT in intraobserver comparison. Mean differences in lengths were included within the range -5 to +5 mm, excluding one of four lengths in observer B in intermodality comparison and one of four on MRI and CT in interobserver comparison. All mean differences in angles were included within the range -5° to +5°. Both observers detected all 40 bilateral main renal arteries on MRI and CT. Of the 13 accessory renal arteries, observers A and B detected four (31%) and nine (69%), respectively, on MRI; in contrast, both observers detected 11 (85%) on CT. The observers independently determined that the same seven patients were suitable for EVAR on MRI and CT. Of the seven selected main endografts, seven and six diameters and five and six lengths agreed exactly between MRI and CT for observers A and B, respectively.
  
  
  CONCLUSIONS
  Although contrast-enhanced CT remains the gold standard for preoperative EVAR planning, unenhanced MRI with steady-state free-precession sequence can be an alternative modality for patients with contraindications for CT, such as renal impairment, because the intermodality agreement for preoperative measurements is as good as interobserver and intraobserver agreement.
authors: Department of Radiology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan. saida_sasaki_tsukasa@yahoo.co.jp
authors: Tsukasa
authors: T
authors: Saida
authors: Kensaku
authors: K
authors: Mori
authors: Fujio
authors: F
authors: Sato
authors: Masashi
authors: M
authors: Shindo
authors: Hideto
authors: H
authors: Takahashi
authors: Nobuyuki
authors: N
authors: Takahashi
authors: Yuzuru
authors: Y
authors: Sakakibara
authors: Manabu
authors: M
authors: Minami
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D001027:Aortography / Q000379:methods*; D019917:Blood Vessel Prosthesis Implantation; D003287:Contrast Media; D057510:Endovascular Procedures; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007564:Japan; D016018:Least-Squares Analysis; D018810:Magnetic Resonance Angiography; D015588:Observer Variation; D018579:Patient Selection; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media