title: In vivo evaluation of patency and in-stent stenoses after implantation of nitinol stents in iliac arteries using MR angiography.
abstract: OBJECTIVE
  Our study was a prospective in vivo study to evaluate whether MR angiography is suitable for assessing stent patency and grading in-stent stenoses and to examine whether the accuracy of MR angiography changes with time after stent implantation.
  
  
  METHODS
  In a prospective study, 34 iliac stenoses in 27 patients were treated by implantation of 35 nitinol stents. MR angiography was performed immediately after stent placement for 32 stents, and both digital subtraction angiography (DSA) and MR angiography were repeated at the 6-month follow-up for 23 stents. Three blinded observers assessed stent patency and the degree of in-stent stenoses on MR angiography and DSA (the standard of reference) images. The difference between the observers' grading of stenoses on DSA and on MR angiography was determined. Statistical analysis was performed using the Student's t test for paired samples.
  
  
  RESULTS
  Stent patency was assessed correctly for all stents and both sets of MR angiography images. Evaluation of DSA 1 images (obtained at end of implantation procedure) revealed that 96.9% of in-stent stenoses were less than 50%. On DSA 2 images (obtained at follow-up), 95.7% of in-stent stenoses were graded as less than 50%. The difference between grading of stenoses on DSA and MR angiography images was 15.0% +/- 16.0% (minimum, 0.0%; maximum, 63.3%) for DSA 1 versus MR angiography 1 (statistically significant, p = 0.037) and 9.8% +/- 13.5% (minimum, 0.0%; maximum, 63.3%) for MR angiography 2 versus DSA 2 (not statistically significant, p = 0.355).
  
  
  CONCLUSIONS
  Patency was correctly assessed for all stents on MR angiography. The quality of MR angiography regarding characterization of in-stent stenoses improved with time after stent placement. However, discrepancies of more than 60% between grading of lumen narrowing on DSA and MR angiography images occurred even at the 6-month follow-up. Thus, MR angiography is not yet a reliable technique for characterization of in-stent stenoses.
authors.affiliation: Department of Diagnostic Radiology, University Hospital of Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany. o.hamer@gmx.de
authors.forename: Okka W
authors.initials: OW
authors.lastname: Hamer
authors.forename: Thomas
authors.initials: T
authors.lastname: Finkenzeller
authors.forename: Ingitha
authors.initials: I
authors.lastname: Borisch
authors.forename: Christian
authors.initials: C
authors.lastname: Paetzel
authors.forename: Niels
authors.initials: N
authors.lastname: Zorger
authors.forename: Stefan
authors.initials: S
authors.lastname: Feuerbach
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Nitz
mesh_terms: D000328:Adult; D000368:Aged; D015901:Angiography, Digital Subtraction; D001157:Arterial Occlusive Diseases / Q000601:surgery*; D016477:Artifacts; D005260:Female; D006083:Graft Occlusion, Vascular / Q000175:diagnosis*; D006801:Humans; D007083:Iliac Artery; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D015607:Stents; D014654:Vascular Patency