title: Improved in-stent magnetic resonance angiography with high flip angle excitation.
abstract: OBJECTIVE
  To optimize the intraluminal signal intensity of a nitinol stent by performing contrast-enhanced three-dimensional magnetic resonance angiography (CE-MRA) with varying flip angles (FAs).
  
  
  METHODS
  Contrast-enhanced magnetic resonance angiography at 1.5 T and FAs of 30 degrees, 100 degrees, and 150 degrees was performed on five sheep with 10 iliac nitinol stents (Memotherm-FLEXX). Maximum-intensity projections (MIPs) and composite images of MIPs were performed and compared.
  
  
  RESULTS
  Reconstructed MIPs at an FA of 150 degrees showed a slightly disturbed lumen visibility inside the stent accompanied by low-grade lumen visibility outside the stent and vice versa for an FA of 30 degrees. Composite images of a 30 degrees MIP added to a 150 degrees MIP resulted in improved image quality compared with the standard MIP of a single FA.
  
  
  CONCLUSIONS
  Signal loss due to radiofrequency shielding inside nitinol stents imaged by CE-MRA can be reduced by applying high FAs. Composite MIP images allow simultaneous visualization of the lumen inside as well as outside the stent.
authors.affiliation: Department of Diagnostic Radiology, University of Technology Aachen, Pauwelsstrasse 30, Aachen, D-52074, Germany. meyer@rad.rwth-aachen.de
authors.forename: J M
authors.initials: JM
authors.lastname: Meyer
authors.forename: A
authors.initials: A
authors.lastname: Buecker
authors.forename: E
authors.initials: E
authors.lastname: Spuentrup
authors.forename: K
authors.initials: K
authors.lastname: Schuermann
authors.forename: M
authors.initials: M
authors.lastname: Huetten
authors.forename: R D
authors.initials: RD
authors.lastname: Hilgers
authors.forename: J J
authors.initials: JJ
authors.lastname: van Vaals
authors.forename: R W
authors.initials: RW
authors.lastname: Guenther
mesh_terms: D000497:Alloys; D000818:Animals; D003287:Contrast Media; D019786:Gadolinium DTPA; D007083:Iliac Artery / Q000473:pathology / Q000601:surgery; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D012756:Sheep; D015607:Stents
chemical_list: D000497:Alloys; D003287:Contrast Media; C013616:nitinol; D019786:Gadolinium DTPA