title: Initial evaluation of non-contrast-enhanced magnetic resonance angiography in patients with peripheral arterial occlusive disease at 7 T.
abstract: OBJECTIVE
  The aim of this study was to achieve initial experience with non-contrast-enhanced (ne) magnetic resonance angiography (MRA) of the lower leg arteries in patients with peripheral arterial occlusive disease (PAOD) at 7 T.
  
  
  METHODS
  Seven patients with PAOD were examined on a 7-T whole-body magnetic resonance system. A custom-built 16-channel transmit/receive coil and a manually positionable AngioSURF table were used for multistation imaging. For ne-MRA, an axial T1-weighted Turbo-fast low angle shot sequence (repetition time, 700 milliseconds; echo time, 3.84 milliseconds; bandwidth, 930 Hz/pixel; voxel volume, 1 × 1 × 2 mm; matrix, 384 × 288) with phonocardiogram gating was acquired at 7 T. Acquisition time of an entire angiogram covering the vasculature from pelvis to feet amounted to approximately 30 minutes, depending on the patient's heart frequency. All patients underwent a contrast-enhanced MRA (ce-MRA) at 1.5 T as standard of reference. The presence of stenosis and occlusions was evaluated segment based and compared for both MRA techniques. The degree of stenosis was defined as low grade (<50%), high grade (50%-99%), and occlusion (100%). High-grade stenosis and occlusion were considered to be hemodynamically significant stenosis.
  
  
  RESULTS
  The 7-T ne-MRA enabled a homogenous, hyperintense artery signal and nearly total venous suppression with accurate delineation of arterial anatomy both proximal and distal to stenotic disease. A total of 154 artery segments were depicted with ce-MRA at 1.5 T. At 7 T, only 124 segments (80.5%) were displayed and involved for analysis, as the iliacal region was displayed incompletely in 4 patients because of the fact that the fixed coil diameter was too small to contain the lower abdomen and pelvis of these patients. In comparison with ce-MRA at 1.5 T as the reference standard, there was total agreement regarding the characterization of an artery segment as being normal or having any kind of stenosis. Of the 124 included segments, 28 segments (23%) had hemodynamically significant stenosis evaluated with 7-T ne-MRA and 26 segments (21%) assessed with 1.5-T ce-MRA. The sensitivity and specificity values of 7-T ne-MRA for detecting segments with hemodynamically significant stenosis were 93% and 98%, respectively.
  
  
  CONCLUSIONS
  Non-contrast-enhanced MRA by means of T1-weighted Turbo-fast low angle shot imaging at 7 T in patients with PAOD is feasible and allowed for good visualization of stenosis and occlusions in all analyzed artery segments in this small patient group. However, this study also shows the challenges of ultrahigh-field body imaging, and more experience is required to determine the impact of 7-T ne-MRA in clinical practice.
authors.affiliation: From the *Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen; †Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen; ‡Medical Physics in Radiology, German Cancer Research Center, Heidelberg; and §Clinic for Vascular Surgery, Elisabeth Hospital Essen, Essen, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Fischer
authors.forename: Stefan
authors.initials: S
authors.lastname: Maderwald
authors.forename: Sören
authors.initials: S
authors.lastname: Johst
authors.forename: Stephan
authors.initials: S
authors.lastname: Orzada
authors.forename: Mark E
authors.initials: ME
authors.lastname: Ladd
authors.forename: Lale
authors.initials: L
authors.lastname: Umutlu
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Lauenstein
authors.forename: Horst-Wilhelm
authors.initials: HW
authors.lastname: Kniemeyer
authors.forename: Kai
authors.initials: K
authors.lastname: Nassenstein
mesh_terms: D000368:Aged; D003287:Contrast Media; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007866:Leg / Q000098:blood supply*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D058729:Peripheral Arterial Disease / Q000175:diagnosis*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D051598:Whole Body Imaging / Q000379:methods
chemical_list: D003287:Contrast Media