title: Magnetic resonance angiography of nonferromagnetic iliac artery stents and stent-grafts: A comparative study in sheep.
abstract: OBJECTIVE
  To compare nonferromagnetic iliac artery prostheses in their suitability for patency monitoring with magnetic resonance angiography (MRA) using conventional angiography as a reference.
  
  
  METHODS
  In experiment 1, three Memotherm stents were inserted into the iliac arteries of each of six sheep: two "tandem" stents on one side and a single stent on the other side. In experiment 2, four prostheses (normal and low-porosity Corvita stent-grafts, Memotherm, ZA-stent) were inserted in each of 11 sheep. Patency was monitored before and 1, 3, and 6 months after insertion with 3D phase-contrast and two 2D time-of-flight sequences (TOF-1: TR/TE = 18/6.9, TOF-2: 13/2.5) with and without contrast at 1.5 T. On 206 coronal MIP images (72 pre-, 134 post-stenting), three readers analyzed 824 iliac segments (206 x 4) for patency and artifacts.
  
  
  RESULTS
  There was no difference in the number of artifacts between tandem and single iliac Memotherm stents. The ZA-stent induced significantly fewer artifacts than the other prostheses (p < 0.00001). With MRA, patency of the ZA-stent was correctly diagnosed in 88% of cases, which was almost comparable to nonstented iliac segments (95%), patency of the Memotherm stent in 59%, and of the Corvita stent-grafts in 57% and 55%. The TOF-2 sequence with contrast yielded the best images.
  
  
  CONCLUSIONS
  MRA compatibility of nonferromagnetic prostheses depends strongly on the design of the device. MRA may be used to monitor the patency of iliac ZA-stents, whereas iliac Memotherm stents and Corvita stent-grafts appear to be less suited for follow-up with MRA.
authors.affiliation: Department of Diagnostic Radiology, University of Technology, Pauwelsstrasse 30, D-52057 Aachen, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Schürmann
authors.forename: D
authors.initials: D
authors.lastname: Vorwerk
authors.forename: A
authors.initials: A
authors.lastname: Bücker
authors.forename: J
authors.initials: J
authors.lastname: Neuerburg
authors.forename: S
authors.initials: S
authors.lastname: Grosskortenhaus
authors.forename: P
authors.initials: P
authors.lastname: Haage
authors.forename: W
authors.initials: W
authors.lastname: Piroth
authors.forename: D W
authors.initials: DW
authors.lastname: Hunter
authors.forename: R W
authors.initials: RW
authors.lastname: Günther
mesh_terms: D000818:Animals; D016477:Artifacts; D004195:Disease Models, Animal; D007083:Iliac Artery / Q000000981:diagnostic imaging / Q000601:surgery*; D018810:Magnetic Resonance Angiography; D008297:Male; D011859:Radiography; D012756:Sheep; D018709:Statistics, Nonparametric; D015607:Stents; D014654:Vascular Patency / Q000502:physiology